Pulse oximetry testing

Abstract

A method and apparatus for testing a pulse oximeter which is based on the concept of an electrical interface between the testing instrument and the oximeter rather than an optical interface. The pulse oximeter signal processor is tested separately from the probe, and still further, the optical elements, that is, the LEDs and the photodiode, of the probe are tested separately from the probe cable. With the probe disconnected from the oximeter, a modulated electrical test signal representative of SpO 2 values and other parameters is generated in response to an electrical signal from the oximeter, and the test signal is applied to the oximeter signal processor, whereby the display of the oximeter shows a value of SpO 2 which is compared with the SpO 2 value represented by the test signal. Independently, the probe including the probe cable, the LEDs and the photodiode are respectively and separately subjected to continuity and optical sensitivity tests. Each of the main components of the oximeter is thereby separately analyzed, and the source of a defect is isolated.

What is claimed is: 
     
       1. An apparatus for testing a pulse oximeter having means for optically sensing SpO 2  values of living tissue, electrical drive means for electrically activating the optically sensing means, and electrical signal processing means responsive to the optically sensing means for producing an oximeter signal corresponding to the SpO 2  value being sensed, said testing apparatus comprising: first testing means bypassing the optically sensing means and responsive to the electrical drive means for generating selected first electrical test signals respectively representative of selected SpO 2  values in living tissue and for transmitting said first signals to the electrical signal processing means to test the ability of the signal processing means to process said representative SpO 2  values and produce oximeter signals corresponding to the selected SpO 2  values represented by the test signals generated, and   second testing means for generating second electrical test signals, for transmitting the same to the optically sensing means, for receiving response signals from the optically sensing means in response to transmission of the second test signals, and for providing an indication of said response signals thereby to test the optically sensing means separately from said testing by the first testing means.   
     
     
       2. The apparatus of claim 1, wherein: the optically sensing means includes an LED, a photodiode for producing an electrical output signal in response to activation of the LED, a first electrical circuit including the LED, and a second electrical circuit including the photodiode, said drive means being connected to the first electrical circuit for electrically activating the optically sensing means, said oximeter further including driven means interconnecting the second electrical circuit and the signal processing means for transmitting the electrical output signal from the photodiode to the signal processing means:   wherein said first testing means is capable of transmitting said first test signals instead of said photodiode output signal, to the driven means for testing the drive means, the driven means and the signal processing means,   said second test signals including electrical continuity test signals and electrical sensitivity test signals,   wherein said second testing means is capable of conducting the electrical continuity test signals through both of said first and second circuits to provide electrical continuity outputs,   wherein said second testing means is capable of conducting the electrical sensitivity test signals through said first circuit to provide an electrical sensitivity output in the second circuit, and further including   means for sensing said electrical continuity and sensitivity outputs from said circuits in response to said continuity and sensitivity test signals to test both the continuity and the optical sensitivity of the optical sensing means.   
     
     
       3. An apparatus for testing a pulse oximeter capable of sensing the SpO 2  in living tissue and including a probe including LEDs and a photodiode; and an electronic unit including an LED driver providing output signals for activating the LEDs, an electronic signal processor for receiving and processing input signals from the photodiode in response to activation of the LEDs, and a display for showing the SpO 2  values represented by the input signals, said probe releasably interconnecting the LED driver and the LEDs and the photodiode and the signal processor, comprising: means operable with the probe disconnected from the LED driver and the signal processor for providing electrical test signals in response to output signals from the LED driver;   means for modulating said electrical test signals so as to provide modulated electrical test signals representative of selected SpO 2  values corresponding to those in living tissue; and   means for transmitting said modulated electrical test signals to the signal processor in place of said input signals to cause the signal processor to process the test signals as if they were said input signals whereby SpO 2  values shown on the display can be compared with a range of selected SpO 2  values corresponding to the modulated electrical test signals thereby to test said electronic unit over its normal operating range.   
     
     
       4. The apparatus of claim 3, further including: electronic memory means adapted to store an SpO 2  profile including a plurality of SpO 2  values which vary over a predetermined time base; and   wherein said modulating means is adapted to modulate said electrical test signals with selected SpO 2  profiles so as to provide modulated electrical test signals representative of selected SpO 2  profiles.   
     
     
       5. The apparatus of claim 4 further including: display means;   wherein said electronic memory means is also adapted to store a cursor for said profiles,   wherein said modulating means is further adapted to feed a selected SpO 2  profile and said cursor to said display means so that a selected profile and cursor can be displayed,   wherein said memory means, said modulating means and said display means cooperate to cause the cursor to move in steps over the displayed profile at a predetermined rate stored in said memory, with the position of the cursor at each step indicating on the display means the value of SpO 2  then modulating the test signal whereby the oximeter can be tested with said profile of SpO 2  values sequentially delivered to the signal processor.   
     
     
       6. An apparatus for testing the probe of a pulse oximeter having an electronic unit including an LED driver and an electronic signal processor; said probe including red and IR LEDs, a photodiode, and a probe cable, said probe cable being releasably connected to the driver and the signal processor when the probe is being used to sense the SpO 2  of living tissue and to feed a signal representative of the same to the signal processor, comprising: means for supplying current to the LEDs and the photodiode while the probe is disconnected from the driver and the signal processor to provide electrical continuity outputs from the LEDs and the photodiode;   means for driving the LEDs while the probe is disconnected from the driver and the signal processor so as to activate the photodiode and provide electrical sensitivity outputs from the photodiode; and   means for sensing said outputs thereby to indicate the sensitivity and the continuity of the probe.   
     
     
       7. An apparatus for testing a pulse oximeter probe which includes optical sensing means providing an LED circuit including red and IR LEDs and a photodiode circuit including a photodiode, there being an interactive red LED-photodiode combination and an interactive IR LED-photodiode combination, said LED circuit, said photodiode circuit, said interactive red LED-photodiode combination, and said interactive IR LED-photodiode combination constituting first, second, third, and fourth parts, respectively, of the optical sensing means capable of being tested for continuity and sensitivity, comprising: current supply means simultaneously connectable to the LED and photodiode circuits for causing testing current to flow in at least one of said circuits and for producing test output signals representative of the test results on at least one of said parts of the optical sensing means; and   means for receiving the test output signals and being responsive to the magnitude thereof to produce an indication of the results of said test to a user of the apparatus.   
     
     
       8. The apparatus of claim 7, further including: indicator means, wherein said current supply means and said receiving means interact to produce test output signals each of which individually represents the test results for one of said parts of the optical sensing means, and   wherein said indicator means is capable of indicating each of said individual output signals, whereby selected parts of the optical sensing means can be separately analyzed.   
     
     
       9. The apparatus of claim 7, further including: indicator means;   wherein for said continuity test, the current supply means is adapted to supply current simultaneously to each of said circuits thereby to produce LED circuit continuity output test signals and photodiode circuit continuity output test signals;   wherein said receiving means includes means for multiplexing said continuity output test signals and means for feeding said multiplexed output test signals to said indicator means; and   wherein said indicator means is adapted separately to indicate the LED and photodiode continuity output signals thereby to enable individual analysis of the continuity of the LED and photodiode circuits.   
     
     
       10. The apparatus of claim 7, further including: indicator means;   wherein said receiving means includes microprocessor means;   wherein, for said sensitivity test, the microprocessor means is adapted to cause the current supply means to alternately supply current to the red LED and the IR LED whereby said test output signals are alternately red sensitivity signals and IR sensitivity signals,   said microprocessor means being adapted to develop red sensitivity/IR sensitivity ratio signals from said red and IR sensitivity signals, and   said indicator means being adapted to indicate said red sensitivity signals, said IR sensitivity signals, and said red sensitivity/IR sensitivity ratio signals to a user of the apparatus, thereby to enable the user to analyze the sensitivity of said third and fourth parts of the optical sensing means.   
     
     
       11. An apparatus for testing the continuity of a pulse oximeter probe which provides an LED circuit and a photodiode circuit, said apparatus comprising: means for activating each of said circuits so as to produce an electrical test output in each circuit representative of whether the circuit is open, continuous or shorted;   means for separating the test outputs representing the LED circuit from the test outputs representing the photodiode circuit; and   means for analyzing each of said outputs to determine whether or not the LED circuit or the photodiode circuit is open, continuous or shorted.   
     
     
       12. The apparatus of claim 11, wherein: said activating means is adapted to activate said photodiode circuit by causing current to flow in a direction in said photodiode circuit opposite to the direction current flows when light activates the photodiode.   
     
     
       13. The apparatus of claim 11, wherein said analyzing means includes display means providing separate channels respectively associated with the test outputs of the LED and photodiode circuits, and   wherein said analyzing means is capable of displaying representations of said test outputs in the respective channels for the LED and photodiode circuits so that a predetermined representation indicates whether the respective circuit is open, continuous, or shorted.   
     
     
       14. The apparatus of claim 11, wherein said analyzing means includes display means,   wherein said analyzing means is capable of displaying representations of said test outputs on the display means so that a predetermined representation represents a circuit that is open, continuous, or shorted, and   wherein said analyzing means is capable of freezing the representation on the display means when a circuit is open or shorted.   
     
     
       15. An apparatus for testing the sensitivity of a pulse oximeter probe which provides red and infrared LEDs an a photodiode adapted to be alternately activated by said LEDs, said apparatus comprising: means for electrically alternately activating the LEDs so as to produce electrical red and IR sensitivity test output signals from the photodiode;   means for producing red sensitivity/IR sensitivity ratio signals from said red and IR test output signals; and   means for indicating each of said red sensitivity, IR sensitivity and red sensitivity/IR sensitivity ratio signals to determine the sensitivity of the optical sensing means.   
     
     
       16. The apparatus of claim 15, wherein said activating means is adapted alternately to supply relatively low and relatively high current to the red and IR LEDs to produce alternately low and high red signals and low and high IR signals, said apparatus further including   means for subtracting the low red from the high red signal and the low IR from the high IR signal, and   wherein said producing means is adapted to produce said red sensitivity signal from the difference between the high and low red signals and to produce said IR sensitivity signal from the difference between the high and low IR signals.   
     
     
       17. The apparatus of claim 15, wherein said indicating means includes display means for respectively separately displaying said red and IR sensitivities and said red sensitivity/IR sensitivity and said red sensitivity/IR sensitivity ratio.   
     
     
       18. A method for testing a pulse oximeter having means for optically sensing SpO 2  values in living tissue, means for electrically activating the optically sensing means, and electrical means responsive to the optically sensing means for indicating the SpO 2  value in tissue being sensed, said method comprising the steps of: generating first test signals representative of SpO 2  values in living tissue in response to the electrically activating means and independently of the optically sensing means,   transmitting the first test signals to the electrical responsive means independently of the optically sensing means to test the ability of the oximeter to indicate said representative SpO 2  values,   generating a second test signal independently of the electrically activating means for testing the optically sensing means,   transmitting the second test signal to the optically sensing means independently of the electrically activating means, and   receiving an output from the optically sensing means indicative of the responses of the optically sensing means to the second test signal, thereby to test the operability of the optically sensing means.   
     
     
       19. The method of claim 18, wherein said generating step for testing the optically sensing means is capable of testing the electrical continuity of the optically sensing means.   
     
     
       20. The method of claim 18, including the further step of: disconnecting the optically sensing means from the electrically activating means and the electrical responsive means,   wherein said generating step includes receiving an output signal from the electrically activating means and modulating said output signal so as to provide a modulated test signal representative of a selected value of SpO 2  corresponding to that in living tissue; and   wherein said transmitting step involves transmitting said modulated test signal to the electrical responsive means so as to provide a modulated test signal representative of a selected value of SpO 2  corresponding to that in living tissue.   
     
     
       21. A method for testing a pulse oximeter over a range of values of SpO 2  expected to exist in living tissue said oximeter having a probe including LEDs and a photodiode; and an electronic unit including an LED driver providing an output signal for activating the LEDs, an electronic signal processor for receiving and processing input signals from the photodiode representative of SpO 2  values in living tissue in response to activation of the LEDs, and a display for showing the SpO 2  values represented by the input signals, said probe releasably interconnecting the LED driver and the LEDs and the photodiode and the signal processor, comprising the steps of: disconnecting the probe from the driver and signal processor;   generating an electrical test signal in response to the output signal from the LED driver;   modulating said electrical test signal so as to provide a modulated electrical test signals representative of selected SpO 2  values in living tissue;   transmitting said modulated electrical test signals to the signal processor in place of said input signals to cause the signal processor to process the test signals as if they were said input signals thereby to test said electronic unit and,   displaying the selected SpO 2  values so that a comparison can be made with the SpO 2  values displayed by the oximeter display to determine the accuracy of the oximeter over a range of SpO 2  values.   
     
     
       22. The method of claim 21, including the further steps of: electronically storing an SpO 2  profile including a plurality of SpO 2  values which vary over a predetermined time base; and   wherein said modulating step is adapted to modulate said electrical test signals with selected SpO 2  profiles so as to provide modulated electrical test signals representative of selected SpO 2  profiles.   
     
     
       23. The method of claim 22 including the further steps of: electronically storing a cursor for said profiles and a stepping rate for the cursor,   displaying a selected profile and said cursor; and   moving the cursor in steps over the displayed profile at said stepping rate so that the position of the cursor at each step indicates the value of SpO 2  then modulating the test signal whereby the oximeter can be tested with said profile of SpO 2  values sequentially delivered to the signal processor.   
     
     
       24. A method for testing a pulse oximeter probe which includes optical sensing means providing an LED circuit including red and IR LEDs and a photodiode circuit including a photodiode, there being an interactive red LED-photodiode combination and an interactive IR LED-photodiode combination, said LED circuit, said photodiode circuit, said interactive red LED-photodiode combination, and said interactive IR LED-photodiode combination constituting first, second, third, and fourth parts, respectively, of the optical sensing means one or more of which is capable of being tested for the parameters of continuity and sensitivity, comprising the steps of: electrically activating said circuits so as to produce electrical test output signals which are representative of at least one of the parameters to-be-tested; and   sensing the test output signals and displaying an indication of whether one or more of said parts meet the standards established for said at least one of the parameters to-be-tested.   
     
     
       25. The method of claim 24, wherein: said activating step activates the circuits so as to produce output test signals which are not affected by ambient light on the photodiode.   
     
     
       26. The method of claim 24, wherein: said activating step involves causing current to flow in the photodiode circuit in the opposite direction from that occurring when the photodiode is activated by light.   
     
     
       27. The method of claim 24, wherein: said activating step involves alternatively supplying high and low current pulses in the red and IR LED circuits, respectively, to produce alternate red high and red low test output signals and IR high and IR low test output signals, said activating step further involving subtracting red low signals from the corresponding red high signals and IR low signals from the corresponding IR high signals, thereby to produce said red sensitivity and said IR sensitivity signals, respectively, and including the further step of   generating red sensitivity/IR sensitivity ratio signals from said red sensitivity and said IR sensitivity signals, and   wherein said sensing step involves analyzing said red and IR sensitivity signals and said red sensitivity/IR sensitivity ratio signals thereby to determine the sensitivity of the optically sensing means.   
     
     
       28. The method of claim 24, further including the step of: displaying graphical representations of the test output signals sensed from said circuits thereby to indicate the condition of the continuity of said circuits, and   displaying graphical representations of the test output signals sensed from the photodiode thereby to indicate the sensitivity of the optically sensing means.   
     
     
       29. A method for testing the continuity of a pulse oximeter probe which provides an LED circuit and a photodiode circuit, comprising the steps of: activating each of said circuits so as to produce an electrical test output in each circuit representative of whether the circuit is open, continuous or shorted;   separating the test outputs representing the LED circuit from the test outputs representing the photodiode circuit; and   analyzing each of said outputs to determine whether or not the LED circuit or the photodiode circuit is open, continuous or shorted.   
     
     
       30. The method of claim 29, wherein said analyzing step further includes: displaying representations of said test outputs so that a predetermined representation represents a circuit that is open, continuous, or shorted, and   freezing the representation when a circuit is open or shorted.   
     
     
       31. The apparatus of claim 1, wherein said first and second testing means are capable of independently but simultaneously testing the signal processing means and the optically sensing means.   
     
     
       32. The apparatus of claim 1, wherein there is a housing enclosing both the first and second testing means, and   wherein there are spaced first and second connector means on the housing respectively connected to the first and second testing means and respectively adapted to be connected to the signal processing means and the optically sensing means.   
     
     
       33. The apparatus of claim 1, wherein there are microprocessor means for controlling the first and second testing means to enable the first and second testing means to test either the signal processing means or the optically sensing means separately or to test both the signal processing means and the sensing means simultaneously.   
     
     
       34. The apparatus of claim 1 wherein the optically sensing means includes an LED, a photodiode for producing an electrical output signal in response to activation of the LED, a first electrical circuit including the LED, and a second electrical circuit including the photodiode, said drive means being connected to the first electrical circuit for electrically activating the optically sensing means, said oximeter further including driven means interconnecting the second electrical circuit and the signal processing means for transmitting the electrical output signal from the photodiode to the signal processing means: wherein said first testing means is capable of transmitting said first test signals, instead of said photodiode output signal, to the driven means for testing the drive means, the driven means and the signal processing means,   wherein said second test signals are electrical continuity test signals,   wherein said second testing means is capable of conducting the electrical continuity test signals respectively through said first and second circuits to provide electrical continuity outputs, and   wherein there are means for sensing said electrical continuity outputs and displaying an indication of the continuity of the optical sensing means.   
     
     
       35. The apparatus of claim 1 wherein the optically sensing means includes an LED, a photodiode for producing an electrical output signal in response to activation of the LED, a first electrical circuit including the LED, and a second electrical circuit including the photodiode, said drive means being connected to the first electrical circuit for electrically activating the optically sensing means, said oximeter further including driven means interconnecting the second electrical circuit and the signal processing means for transmitting the electrical output signal from the photodiode to the signal processing means: wherein said first testing means is capable of transmitting said first test signals, instead of said photodiode output signal, to the driven means for testing the drive means, the driven means and the signal processing means,   wherein said second test signals are electrical sensitivity test signals,   wherein said second testing means is capable of conducting the electrical sensitivity test signals through said first circuit to provide electrical sensitivity outputs in the second circuit, and   wherein there are means for sensing said electrical sensitivity outputs and displaying an indication of the optical sensitivity of the optical sensing means.   
     
     
       36. The apparatus of claim 3, wherein the apparatus includes means for displaying the values of SpO 2  represented by the modulated electrical test signals whereby SpO 2  values showing on the oximeter display can be compared with selected SpO 2  values showing on the displaying means thereby to determine the accuracy of the oximeter throughout a range of SpO 2  values.   
     
     
       37. An apparatus for testing the continuity of a pulse oximeter probe which provides LED and photodiode circuits connected to LED and photodiode terminals of a probe connector, said apparatus comprising: means simultaneously connectable to the LED and photodiode terminals of the probe connector for activating each of said circuits so as to produce an electrical test output in each circuit representative of whether the circuit is open, continuous or shorted; and   means responsive to said test outputs for displaying indicia representing whether said LED and photodiode circuits are open, continuous or shorted.   
     
     
       38. The apparatus of claim 37, wherein the activating means is a current source for each of said circuits.   
     
     
       39. The apparatus of claim 38, wherein the current sources are simultaneously connectable to their respective LED and photodiode circuits, and   wherein the activating means causes current from the current sources to supply current simultaneously to said circuits.   
     
     
       40. The apparatus of claim 37, wherein the responsive means is capable of sensing and displaying intermittent test outputs of a predetermined threshold indicative of a glitch in either of said circuits. 
     
     
       41. The apparatus of claim 37, wherein there are means for combining the test outputs into a combined signal with alternating LED and photodiode pulses, and   wherein there are means for using the LED and photodiode pulses to display an indication of whether the LED and photodiode circuits are open, continuous or shorted.   
     
     
       42. The apparatus of claim 41, wherein the combining means combines the test outputs into a combined analog signal with said alternating LED and photodiode pulses,   wherein there are means for converting the combined analog signal into discrete digital signals representative of said LED and photodiode pulses; and   wherein there are means for sampling the digital signals and displaying the same to indicate whether or not the LED circuit or the photodiode circuit is open, continuous or shorted.   
     
     
       43. An apparatus for testing the continuity of a pulse oximeter probe that has an LED circuit and a photodiode circuit, comprising means for supplying testing current to each of the LED and photodiode circuits to produce responses including separate analog LED and photodiode continuity voltages,   means for combining said voltages into a single voltage signal with alternating LED and photodiode pulses,   means for converting the single voltage signal into a series of discrete digital voltage pulses representative of the alternating LED and photodiode pulses,   means for sampling the digital voltage pulses,   display means, and   means for activating the display means with the signal samples to indicate whether the LED and photodiode circuits are open, continuous, or shorted.   
     
     
       44. The apparatus of claim 15, wherein said indicating means includes display means for respectively displaying bargraphs in separate channels of said red and IR sensitivities and said red sensitivity/IR sensitivity ratio.   
     
     
       45. The method of claim 18, wherein said generating step for testing the optically sensing means is capable of testing the optical sensitivity of the optically sensing means.   
     
     
       46. The method of claim 19, wherein said generating step for testing the optically sensing means is capable of testing the optical sensitivity of the optically sensing means.   
     
     
       47. A method for testing a pulse oximeter probe which includes optical sensing means providing an LED circuit including red and IR LEDs and a photodiode circuit including a photodiode, there being an interactive red LED-photodiode combination and an interactive IR LED-photodiode combination said LED circuit, said photodiode circuit, said interactive red LED-photodiode combination, and said interactive IR LED-photodiode combination constituting first, second, third, and fourth parts, respectively, of the optical sensing means to be subjected to such testing including the parameters of continuity and sensitivity, comprising the steps of: electrically activating said circuits so as to produce electrical test output signals which are representative of the parameters to-be-tested of said parts;   electrically separating the test output signals so that there is a test output signal representative of continuity for each of said first and second parts and a test output signal representative of the sensitivity for each of said third and fourth parts;   and analyzing each of said output signals to determine whether or not said parts meet the standards established for said parameters.   
     
     
       48. The method of claim 24 which involves the use of a testing device capable of performing said activating, sensing and displaying steps, further including the step of: electrically connecting the testing device simultaneously to both the LED and photodiode circuits prior to said electrically activating step thereby to enable testing of selected ones of said parts.   
     
     
       49. A method for testing the continuity of a pulse oximeter probe that includes an LED circuit and a photodiode circuit, comprising the steps of: simultaneously connecting electrical activating means to both of the LED and photodiode circuits,   electrically activating each of said circuits with test signals thereby to produce an electrical test output in each circuit representative of whether the circuit is open, continuous or shorted; and   processing the test outputs to provide a visual indication of whether or not each circuit is open, continuous or shorted.   
     
     
       50. The method of claim 49, wherein the activating step involves simultaneously supplying said test signals in the form of current fed to each of said circuits from separate current sources respectively associated with said circuits.   
     
     
       51. The method of claim 49 wherein the probe includes a probe cable including conductors that are part of said circuits, including the further step of: moving the cable around during the electrical activation so that if one or more of the conductors has an open or short condition that occurs only intermittently, such movement will cause the open or short to occur.   
     
     
       52. The method of claim 51, wherein the moving step causes a voltage spike in said test output of the circuit in which an intermittent short or open condition exists;   and wherein the processing step is responsive to the voltage spike to provide a visual indication of the same, whereby such intermittent short or open conditions are not overlooked by the user performing the test.   
     
     
       53. A method for testing the continuity of a pulse oximeter probe that has an LED circuit and a photodiode circuit, comprising the steps of: supplying current to both the LED and photodiode circuits to produce responses including separate LED and photodiode continuity voltages; sensing said responses and combining them into a single voltage signal with alternating LED and photodiode pulses;   converting the single voltage signal into a series of discrete voltage pulses representative of the alternating LED and photodiode pulses; and   using the discrete voltage pulses to display indications of whether the LED and photodiode circuits are open, continuous or shorted. .Iadd.   
     
     
       54.  An apparatus for testing the sensitivity of a pulse oximeter probe which provides red and infrared LEDs and a photodiode, said apparatus comprising: a red current source that generates red LED activating signals, applies them to the red LED, and generates red high and red low outputs on the photodiode;   an IR current source that generates IR LED activating signals, applies them to the IR LED, and generates IR high and IR low outputs on the photodiode;   sensor circuitry that is responsive to the red high and the red low outputs on the photodiode and to the IR high and the IR low outputs on the photodiode and that generates red testing signals and IR testing signals from said outputs; and   a display that is responsive to the red and IR testing signals and produces an indication thereof, said indication being an indication of the sensitivity of the probe. .Iaddend..Iadd.55. The apparatus of claim 54,   wherein the red current source generates high and low red activating signals and applies them to the red LED thereby to produce said high and low red outputs in the photodiode; and   wherein the IR current source generates high and low IR activating signals and applies them to the IR LED thereby to produce said high and low IR outputs in the photodiode. .Iaddend..Iadd.56. An apparatus for testing the sensitivity of a pulse oximeter probe which provides red and infrared LEDs and a photodiode, said apparatus comprising:   means for applying red high and red low LED activating signals to the red LED so that red high and red low outputs are on the photodiode;   means for applying IR high and IR low LED activating signals to the IR LED so that IR high and IR low outputs are on the photodiode;   means for sensing the outputs on the photodiode and producing a red testing signal from the red high and red low outputs on the photodiode and an IR testing signal from the IR high and IR low outputs on the photodiode, said red and IR testing signals being the differences between their respective high and low outputs; and   means for displaying an indication of said testing signals whereby said indication is an indication of the sensitivity of the probe. .Iaddend..Iadd.57. A method for testing the sensitivity of a pulse oximeter probe which provides red and infrared LEDs and a photodiode, comprising the steps of:   activating one of the LEDs with signals of high and low amplitude thereby producing first high and low outputs on the photodiode;   sensing the first high and low outputs on the photodiode;   producing a first testing signal from said first high and low outputs;   activating the other of the LEDs with signals of high and low amplitude thereby producing second high and low outputs on the photodiode;   sensing the second high and low outputs on the photodiode;   producing a second testing signal from said second high and low outputs; and   displaying an indication of said first and second testing signals thereby to indicate the sensitivity of the probe. .Iaddend..Iadd.58. The method of claim 57,   wherein producing the first and second testing signals involves obtaining the difference between the first high and low outputs and the difference between the second high and low outputs resulting respectively in first and second difference signals. .Iaddend..Iadd.59. An oximeter tester for an oximeter that includes a signal processor, an LED driver and a probe including LED and photodiode circuits respectively including light emitting diodes and a photodiode, the probe being releasably connected to the signal processor and the LED driver, the tester comprising:   a first sensor having an input adapted to be connected to the LED driver in the oximeter in place of the probe, the first sensor, when so connected, receiving electrical red and IR drive signals from the LED driver of the oximeter and producing red and IR pulses,   a de-multiplexer coupled to the sensor and separating the red and IR pulses,   a source of SpO 2  waveforms corresponding to those normally received by the oximeter when its probe is attached to a human being,   a modulator coupled to the de-multiplexer and modulating the separate red and IR pulses with said SpO 2  waveforms from the source and thereby generating first electrical test signals representative of SpO 2  waveforms of living tissue corresponding to those normally received by the oximeter when its probe is attached to a human being,   a tester driver having an input coupled to the modulator and an output adapted to be connected to the signal processor in the oximeter and, when so connected, delivering said first electrical test signals to the signal processor thereby to test the ability of the signal processor to process said SpO 2  waveforms and produce oximeter read-outs corresponding to SpO 2  values represented by the test signals generated;   a current source adapted to be connected to one or more diodes in the probe and, when so connected, coupling second electrical test signals to said one or more of the diodes thereby to activate the diodes;   a second sensor adapted to be connected to one or more diodes in the probe and, when so connected, receiving response signals from said one or more of the diodes in response to the second electrical test signals;   a display;   circuitry interconnecting the second sensor and the display and applying signals to the display indicative of the response signals from the sensor; and   a microprocessor coupled to the modulator, the display and the source and controlling the application of the SpO 2  waveforms to the modulator and the application of actuating current to said one or more diodes, and the application of the signals to the display. .Iaddend..Iadd.60. An apparatus for testing a pulse oximeter having an optical sensor that senses SpO 2  values of living tissue, an electrical driver that produces an electrical signal that activates the optical sensor, and a signal processor responsive to the optical sensor that produces an oximeter signal corresponding to the SpO 2  value being sensed, said testing apparatus comprising:   for testing circuitry that is responsive to the signal from the electrical driver in the oximeter, that generates first electrical test signals that are SpO 2  waveforms simulating those generated by the probe of the oximeter when the oximeter is used to check the blood oxygen level of a patient, and that transmits said first signals to the signal processor of the oximeter independently of the optical sensor,   second testing circuitry that generates second electrical test signals, that transmits the second electrical test signals to the optical sensor in the oximeter independently of the electrical driver of the oximeter, and that receives response signals from said optical sensor in response to transmission of the second test signals, and   a display that provides an indication of said response signals from the second testing circuitry. .Iaddend..Iadd.61. The testing apparatus of claim 60,   wherein the first testing circuitry includes an electrical sensor that receives the electrical signal from the electrical driver and produces an output, a modulator that is connected to the electrical sensor and generate the selected first electrical test signals respectively representative of selected SpO 2  waveforms in response to the output from the electrical sensor, and a tester driver that is connected to the modulator and transmits said first signals to the signal processor in the oximeter. .Iaddend..Iadd.62. The apparatus of claim 61,   wherein the first testing circuitry includes an electronic memory that stores an SpO 2  profile including a plurality of said SpO 2  waveforms; and   wherein the modulator modulates said electrical test signals with selected SpO 2  profiles and provides modulated electrical test signals   
     
     
        representative of selected SpO 2  profiles. .Iaddend..Iadd.63.  The testing apparatus of claim 60, wherein the second testing circuitry includes a source of current that generates the second electrical test signals, electrical connections that transmit the second electrical test signals to the optical sensor, and electrical sensors that receive the response signals from the optical sensor, and   wherein the display is connected to the electrical sensors of the second testing circuitry and produces said indication from the output of the electrical sensors. .Iaddend..Iadd.64. The apparatus of claim 60,   wherein there is a housing enclosing both the first and second testing circuitry, and   wherein there are spaced first and second connectors in the housing respectively connected to the first and second testing circuitry and respectively adapted to be connected to the signal processor and the optical sensor. .Iaddend..Iadd.65. The apparatus of claim 60,   wherein there is a microprocessor that controls the first and second testing circuitry in testing the signal processor and the optical sensor. .Iaddend..Iadd.66. The apparatus of claim 60 for testing a pulse oximeter the optical sensor of which has an LED circuit, a photodiode circuit, and an oximeter connector providing LED and photodiode terminals respectively connected to the LED circuit and photodiode circuits,   wherein the second testing circuitry includes LED testing circuitry, photodiode testing circuitry, and a tester connector having LED and photodiode terminals respectively connected to the LED testing circuitry and photodiode testing circuitry, the LED and photodiode terminals in the tester connector corresponding to the LED and photodiode terminals of the oximeter connector, so that when the tester connector is connected to the oximeter connector, the LED testing circuitry and photodiode testing circuitry are respectively connected to the LED circuit and the photodiode   
     
     
        circuits. .Iaddend..Iadd.67.  An apparatus for testing the probe of a pulse oximeter, said probe including an LED, a photodiode, and a probe connector with LED and photodiode terminals respectively connected to the LED and photodiode, the testing apparatus comprising: a tester connector having LED and photodiode terminals capable of connecting to LED and photodiode terminals of the probe connector;   a signal source that generates probe testing signals and that is connected to predetermined terminals of the tester connector for applying testing signals on the said predetermined terminals so that the testing signals will be applied to the probe when the tester connector is connected to the probe connector;   a signal sensor that is connected to certain terminals of the tester connector, that is responsive to outputs thereon resulting from application of the probe testing signals to the probe, and that generates output signals representative of the outputs from the probe; and   a display connected to the signal sensor for displaying an indication of said output signals, thereby to test the operability of the probe.   
     
     
        .Iaddend..Iadd.68.  The apparatus of claim 67, the probe having LED and photodiode circuits respectively including the LED and the photodiode, wherein the signal source generates probe continuity testing signals at the LED and photodiode terminals of the tester connector;   wherein the signal sensor is connected to the LED and photodiode terminals of the tester connector, is responsive to continuity outputs on said LED and photodiode terminals resulting from the continuity testing signals, and generates continuity output signals representative of the continuity of the LED and photodiode circuits; and   wherein the display shows an indication of the continuity of the LED and photodiode circuits. .Iaddend..Iadd.69. The apparatus of claim 67,   wherein the signal source generates probe sensitivity testing signals at the LED terminals of the tester connector;   wherein the signal sensor is connected to the photodiode terminals of the tester connector, is responsive to sensitivity outputs on said photodiode terminals resulting from the sensitivity testing signals, and generates sensitivity output signals representative of the sensitivity of the probe; and   wherein the display shows an indication of the sensitivity of the probe. .Iaddend..Iadd.70. The apparatus of claim 69, the probe having red and IR LEDs,   wherein the probe sensitivity signals generated by the signal source are high and low current signals for the red LED and high and low current signals for the IR LED, thereby to enable high and low red outputs and high and low IR outputs to be generated by the photodiode when the tester connector is connected to the probe connector;   wherein the signal sensor is responsive to the high and low red outputs and generates red difference signals representing the difference between said high and low red outputs;   wherein the signal sensor is responsive to the high and low IR outputs and generates IR difference signals representing the difference between said high and low IR outputs; and   wherein the display is responsive to the red and IR difference signals and displays an indication thereof to indicate the sensitivity of the red and   
     
     
        IR LEDs. .Iaddend..Iadd.71.  A method for testing the continuity of a pulse oximeter probe that includes an LED circuit and a photodiode circuit, said method involving the use of a tester having a tester connector providing terminals connected to an electrically actuating source and a sensor in the tester, and a probe connector providing terminals connected to said circuits, comprising the steps of: connecting the tester connector to the probe connector and thereby simultaneously connecting the electrically activating source and the sensor to the LED and photodiode circuits,   electrically activating each of said circuits with said source,   sensing each circuit with said sensor for outputs in response to said electrical activation,   producing indications of outputs that are sensed, and   determining the continuity of the circuits from said indications. .Iaddend..Iadd.72. A method for testing the sensitivity of a pulse oximeter probe that has red and IR LED circuits and a photodiode circuit including a photodiode, said method involving the use of a tester having a tester connector providing terminals connected to an electrically actuating source and a sensor in the tester, and a probe connector providing terminals connected to said circuits, comprising the steps of:   connecting the tester connector to the probe connector and thereby simultaneously connecting the electrically activating source and the sensor to the LED and photodiode circuits,   electrically activating the LED circuits with said source,   sensing the photodiode circuit with the sensor for outputs in response to said electrical activation,   producing indications of outputs that are sensed, and   determining the sensitivity of the photodiode from said indications. .Iaddend..Iadd.73. A pulse oximeter testing apparatus for testing a pulse oximeter having an optical sensor that senses SpO 2  values of living tissue, an electrical driver that produces an electrical signal that activates the optical sensor, and a signal processor responsive to the optical sensor that produces an oximeter signal corresponding to the SpO 2  value being sensed, said testing apparatus comprising:   a current sensor that is responsive to the electrical signal from the electrical driver in the oximeter and produces simulated red and IR signals;   an electronic memory storing SpO 2  waveforms that simulate SpO 2  waveforms in living tissue like those produced by the optical sensor in the normal operation of the oximeter;   a modulator responsive to the simulated red and IR signals from the current sensor, modulating the simulated red and IR signals with selected simulated SpO 2  waveforms from the memory, and generating modulated test signals respectively representative of the selected SpO 2  waveforms in living tissue; and   a tester driver responsive to the modulated test signals from the modulator, that produces electrical test signals representative of the selected SpO 2  waveforms, and that transmits the test signals to the signal generator in the oximeter to test the ability of the signal processor to process said representative SpO 2  waveforms and produce oximeter signals corresponding to the selected simulated SpO 2  waveforms. .Iaddend..Iadd.74. The combination of a pulse oximeter and a testing apparatus, the oximeter having a signal processor, a display and a probe, the probe normally receiving signals from the oximeter and delivering modulated human signals to the signal processor resulting from a human finger or other body part placed in the probe,   wherein the testing apparatus is connected to the oximeter in place of the probe;   wherein the tester receives the signals from the oximeter that would normally be delivered to the probe;   wherein the testing apparatus includes an electronic memory containing a database of waveforms corresponding to those produced by human fingers or other body parts when placed in the probe of an oximeter;   wherein the testing apparatus also includes a modulator that modulates the signals received by the testing apparatus with selected waveforms from the electronic memory thereby generating modulated testing signals that simulate the modulated human signals resulting from a human finger or other body part placed in the probe when the oximeter is in its normal use;   wherein the testing apparatus delivers the modulated testing signals to the signal processor;   wherein the modulating testing signals are processed by the signal processor as if the modulating testing signals were the modulated human signals thereby producing processed signals; and   wherein the processed signals are displayed on the display whereby comparisons can be made with known values. .Iaddend..Iadd.75. An apparatus for testing a pulse oximeter having an optical sensor that senses SpO 2  values of living tissue, an LED driver, a signal processor responsive to the optical sensor that produces an oximeter signal corresponding to the SpO 2  value being sensed and a display, said testing apparatus comprising:   first means for testing the LED driver and the signal processor of the oximeter separately from the optical sensor of the oximeter, the display in the oximeter displaying the results of the first testing means;   second means for testing the optical sensor of the oximeter separately from the LED driver and the signal processor of the oximeter; and   means for displaying the results of the second testing means. .Iaddend..Iadd.76. An apparatus for testing a pulse oximeter having an optical sensor that senses SpO 2  values of living tissue, a signal processor responsive to the optical sensor that produces an oximeter signal corresponding to the SpO 2  value being sensed, and a display that displays the said SpO 2  values sensed, the testing apparatus comprising:   means for testing the signal processor of the oximeter with testing SpO 2  values independently of the optical sensor; and   means for enabling a comparison of the testing SpO 2  values with the   
     
     
        SpO 2  values displayed on the oximeter display. .Iaddend..Iadd.77.  An oximeter probe tester for an oximeter probe having LED and photodiode circuits, comprising: means for electrically activating the LED circuit and the photodiode circuit of the oximeter probe so as to produce electrical test output signals in the circuits that are representative of the continuity of the circuits,   means for sensing whether or not the test output signals are present in the circuits, and   means for displaying an indication of the test output signals sensed. .Iaddend..Iadd.78. An oximeter probe tester for an oximeter probe having a LED circuit including LEDs and a photodiode circuit including a photodiode, comprising:   means for electrically activating the LEDs of the oximeter probe so as to produce electrical test output signals in the photodiode that are representative of the sensitivity of the photodiode,   means for sensing the test output signals, and   means for displaying an indication of the test output signals sensed. .Iaddend..Iadd.79. An oximeter probe tester for an oximeter probe having an LED circuit including LEDs and a photodiode circuit including a photodiode, comprising:   means for electrically activating the LED circuit and the photodiode circuit of the oximeter probe so as to produce electrical test output signals in the circuits that are representative of the continuity of the circuits,   means for sensing whether or not the test output signals are present in the circuits,   means for electrically activating the LEDs of the oximeter probe so as to produce electrical test output signals on the photodiode that are representative of the sensitivity of the photodiode,   means for sensing the test output signals on the photodiode, and   means for selectively and separately displaying an indication of the test output signals that are representative of the continuity of the circuits and the test output signals that are representative of the sensitivity of   
     
     
        the photodiode. .Iaddend..Iadd.80.  The apparatus of claim 54, wherein the red testing signals are red difference signals that represent the difference between the red high and red low outputs from the photodiode; and   wherein the IR testing signals are IR difference signals that represent the difference between the IR high and IR low outputs of the photodiode. .Iaddend..Iadd.81. The apparatus of claim 80.   wherein the red and IR testing signals also include ratio signals that represent the ratio of the red difference signals to the IR difference   
     
     
        signals. .Iaddend..Iadd.82.  A method for testing a pulse oximeter with a testing instrument wherein the oximeter includes a probe, an LED driver, a signal processor, an oximeter interface connector connected to the signal processor and the LED driver, the probe including LEDs, a photodiode, and a probe connector connected to the oximeter interface connector in normal use of the oximeter, the LEDs being responsive to LED drive signals from the LED driver and the photodiode generating SpO 2  waveforms for delivery to the signal processor through the oximeter interface connector when the probe is attached to the human being, and wherein the testing instrument includes a housing, a probe testing connector mounted on the housing, and a simulator testing connector mounted on the housing, the method comprising the steps of: connecting either the probe connector alone to the probe testing connector, the simulator testing connector alone to the oximeter interface connector, or both the probe connector and the simulator testing connector, respectively, to the probe testing connector and the oximeter interface connector;   with the simulator testing connector connected to the oximeter interface connector in place of the probe, generating first test signals representative of SpO 2  waveforms that simulate said human SpO 2  waveforms generated by the probe in response to said LED drive signals;   transmitting the first test signals to the signal processor through the interconnected simulator testing connector and oximeter interface connector;   with the probe connector connected to the probe testing connector instead of to the oximeter interface connector, generating a second test signal independently of the LED driver;   transmitting the second test signal to the probe through the interconnected probe connector and probe testing connector;   receiving an output from the probe in response to the second test signal; and   
     
     
       displaying said output. .Iaddend..Iadd.83.  A method for testing either the continuity or the sensitivity or both of a pulse oximeter probe that has an LED circuit including red and IR LEDs, a photodiode circuit including a photodiode, and a probe connector, the method involving the use of a housing enclosing electrically activating sources and signal sensing circuitry and mounting a probe testing connector providing LED and photodiode terminals connected to the electrically activating sources and the signal sensing circuitry, the method comprising the steps of: interconnecting the probe connector and the probe testing connector and thereby interconnecting the LED and photodiode terminals and the LED and photodiode circuits respectively;   electrically activating both of the LED and photodiode circuits with an electrical activating source in the housing if continuity is being tested;   electrically activating only the LED circuits with an electrical activating source in the housing if sensitivity is being tested;   sensing both of the LED and photodiode circuits for outputs in response to said electrical activation if continuity is being tested;   sensing the photodiode circuit for outputs in response to said electrical activation if sensitivity is being tested;   displaying visual indications of the outputs that are sensed, and   determining the continuity and/or sensitivity of the probe from said visual indications. .Iaddend.