Patent Publication Number: US-2009227852-A1

Title: Pulse sensor, pulse meter, oximeter, joystick, and helmet

Description:
The invention relates to the technical field of pulse sensors, pulse meters and oximeters as well as to applications of pulse sensors in joysticks and helmets. Specifically, the invention relates to pulse and/or oximeters of small structural shapes and to sensors for such apparatus, which are equipped with an acoustic and/or optical alarm. 
     The basic mode of operation of oximeters is described, for example, in U.S. Pat. No. 6,736,759 B1. Oxyhemoglobin found in oxygen-enriched corpuscles and deoxyhemoglobin found in low-oxygen corpuscles have a different optical absorption. Deoxyhemoglobin absorbs more in the red range, while oxyhemoglobin absorbs more in the infrared range. Absorption curves are shown, for example, in U.S. Pat. No. 5,152,296. To detect these differences, mostly red light-emitting diodes, which emit light mainly between 610 nm and 650 nm, and infrared light-emitting diodes having an emission mainly between 810 and 850 nm, are used. 
     Light having two different wavelengths is alternately directed at tissue supplied with blood. A photosensor detects transmitted or backscattered light, depending on the model of the oximeter sensor. Depending on which of the light-emitting diodes lights up, the absorption or backscattering in the red or infrared range is measured. 
     The absorption of light in the tissue also depends on the phase of the heartbeat. During the systole the amount of blood in the arteries increases, which leads to a detectable increased light absorption. Therefore, the pulse of a subject can be determined from the time interval between the light absorption peaks. Although this type of pulse measurement only requires one wavelength, the pulse can also be determined from the signal of an oximeter sensor. Therefore, the additional effort for a pulse measurement in an oximeter is small. Consequently, almost exclusively pulse oximeters are being sold at present. 
     U.S. Pat. No. 6,736,759 B1 describes several embodiments of a training monitoring system. This system comprises an electronic positioning apparatus operated on a GPS basis (global positioning system), a physiological monitor, which may include an oximeter, as well as a display device. In one embodiment, a GPS module, an oximeter, batteries, a processor-transmitter module and other modules may be attached to a belt worn by a sportsman around his belly. On one wrist the sportsman wears the display device, which is received in a watch-like housing. The display device comprises a (radio) receiver so as to receive data from the processor-transmitter module, a processor, a display screen, input switches as well as one or more alarms delivering an audible and/or visible information such as blinking. An alarm can, for example, be activated when the blood oxygen content or the pulse are outside a predetermined range. The predetermined range can be adjusted by means of the input switches. In another embodiment, the display device can be accommodated in a tacho-like housing, which is attached to a handlebar of a bicycle. Finally, an embodiment is described, in which the data to be displayed are played into the eyes of a user via spectacle glasses. 
     In U.S. Pat. No. 5,490,523 a finger clip pulse oximeter is described, which is sold by Nonin Medical Inc. obviously under the product name 9500 Onyx. In use, for example, the index is clamped between a lower housing and an upper housing. A spring presses both housings against the finger. In the lower housing there is provided a battery case and an aperture through which two light-emitting diodes (LEDs) can emit light. In the upper housing there is substantially accommodated a board carrying the electronic system and six 7-segment LEDs for displaying the measured values. The upper half of the upper housing is transparent. On the underside of the board a photodetector is mounted, which picks up through an aperture in the lower half of the upper housing the light transmitted by the finger. A flat ribbon cable connects the battery case, the two LEDs mounted on the flat ribbon cable, the upper half of the lower housing, the lower half of the upper housing and the board. In a second embodiment a reflection pulse oximeter may be used, which is described, for example, in U.S. Pat. No. 5,224,478. In this embodiment, all units may be accommodated in one housing. For the measurement, the user places his finger into a hollow provided in said housing. In a third embodiment, the shape of the housing of a reflection pulse oximeter can be adapted to the shape of the forehead of a user and is fixed to the forehead presumably by means of a tape. 
     Under the product name 3100 WristOx Nonin Medical Inc. offers a pulse oximeter in watch form, which may be worn on one wrist. The 3100 WristOx can be connected, for example, to a finger clip sensor. 
     A similar device is described in U.S. Pat. No. 6,731,962 B1 and is called a finger oximeter. It is sold, for example, by Miami Medical under the trademark DIGIT and is obviously manufactured by BCI. In addition to the finger clip pulse oximeter described in U.S. Pat. No. 5,490,523 the finger oximeter includes a bi-directional radio interface, so that the finger oximeter can communicate in a cordless manner with a remote monitoring system, e.g. a Vital Signs of Smith Medical PM, Inc., Waukesha, Wis., USA. The signal received can be displayed graphically or alphanumerically in the monitor. The signal can also be outputted by the monitoring system as an audio or visual alarm if an undesired threshold is reached or exceeded. The radio interface can use the Bluetooth protocol. The finger oximeter can be activated or deactivated by a switch provided in the housing of the finger oximeter or by the monitoring system. 
     In U.S. Pat. No. 5,800,349 different transmission pulse oximeter sensors are described, in which the light sources and the photodetectors are not arranged on one axis; but offset with respect to each other. 
     In U.S. Pat. No. 6,771,172 B1 a portable patient monitor is described, in the handle of which red and yellow light-emitting diodes are installed so as to output visual alarms. An alarm may also be outputted by a loudspeaker. The alarm thresholds can be set by means of a keyboard. The patient monitor can be a portable oximeter. 
     If the oxygen partial pressure in the respiratory air decreases, humans lose their consciousness without realizing it. The time until the loss of consciousness is called “usable consciousness”. The oxygen partial pressure can drop, for example, because of a defect in the air conditioning system of aircraft or if gliders flying too high. Whether and when a specific oxygen partial pressure leads to a loss of consciousness also depends on the constitution of the person concerned. An imminent loss of consciousness can be detected by means of an oximeter from the oxyhemoglobin content of the person more independently of its constitution than it would be possible, for example, by measuring the pressure or the oxygen partial pressure in the ambient air. After all, persons with pulmonary diseases can have problems already in 1500 to 2000 m above mean sea level, e.g. during mountain tours. 
     If during the usable consciousness the risk of a loss of consciousness is displayed to the persons, they can take countermeasures. 
     It is the object of the invention to provide pulse and oximeter sensors, pulse and oximeters as well as joysticks and helmets for active persons. 
     This object is achieved with the teaching defined in the independent claims. 
     Preferred embodiments of the invention are defined in the dependent claims. 
     It is an advantage of the invention that the attention of sportsmen, pilots or persons having pulmonary diseases is actively drawn to an overload or oxygen deficit in their body. 
     A buzzer, a loudspeaker, a bright light source, a vibrator or electrodes have the advantage that all of these means actively attract the attention of a person. Thus, the person is not forced to check one or two three-digit 7-segment displays from time to time. Besides, the invention solves so-to-speak also the problem that the time interval between two checks must be shorter than the usable consciousness. When using apparatus according to the prior art, the person would, after all, have to be reminded somehow of the next reading of the display. 
     A battery-operated pulse meter can be equipped with a vibration alarm in a particularly compact manner if one or more batteries are moved with respect to the housing. 
     It is an advantage of the use of a warning and alarm mode that the urgency of a danger is recognizable. 
     It is particularly advantageous to draw a person&#39;s attention to too low an oxyhemoglobin content in its blood by means of an stimulus, because there is the danger that the person loses its consciousness without pains or malaise. 
     Advantageously, a pulse sensor or an oximeter sensor can be integrated in a joystick or a helmet. 
     Also stimulus generators such as LEDs or electrodes can advantageously be integrated in joysticks or helmets. 
    
    
     
       A preferred embodiment of the invention will be explained in more detail below by means of the accompanying drawings, wherein 
         FIG. 1  shows a finger clip pulse oximeter according to the invention; 
         FIG. 2  shows a lower half of the housing of the finger clip pulse oximeter illustrated in  FIG. 1 ; 
         FIG. 3  shows an upper half of the housing of the finger clip pulse oximeter illustrated in  FIG. 1 ; 
         FIG. 4  shows a section through a first embodiment of the lower half of the housing illustrated in  FIG. 2 ; 
         FIG. 5  shows a section through a second embodiment of the lower half of the housing illustrated in  FIG. 2 ; 
         FIG. 6  shows a lateral view of an ear clip sensor according to the invention; 
         FIG. 7  shows a rear view of an ear clip sensor according to the invention; 
         FIG. 8  shows a top view of a wrist pulse oximeter according to the invention; 
         FIG. 9  shows a section through the wrist pulse oximeter illustrated in  FIG. 8 ; 
         FIG. 10  shows a warning and alarm characteristic of an oximeter according to the invention; 
         FIG. 11  shows a warning and alarm characteristic of a pulse meter according to the invention; 
         FIG. 12  shows a display according to the invention; 
         FIG. 13  shows a joystick according to the invention; and 
         FIG. 14  shows a helmet according to the invention. 
     
    
    
     One essential aspect of this invention consists in the measurement of the oxyhemoglobin content in the blood of a person and/or the pulse of the person and in warning the person by appropriate stimuli if the oxyhemoglobin content or the pulse adopt undesired or even dangerous values. 
     The finger clip pulse oximeter  1  shown in  FIG. 1  comprises an upper housing half  3 , a lower housing half  2  as well as a spring  4  pressing the upper housing half  3  and the lower housing half  3  together. The spring  4  engages into the grooves  13  and  14  in the upper housing half  3  and the lower housing half  2 , respectively. Both the upper housing half  3  and the lower housing half  2  include a recess  5  for receiving a finger, especially an index, whereby the depth of the recess  5  is dimensioned in such a close-fitting manner that the upper and the lower housing halves  3  and  2  are not pressed against each other, but press against the finger. 
     The upper housing half  3  comprises a first key  11  and a second key  12  for controlling the pulse oximeter  1 , as well as a groove  13  into which the spring  4  is engaged. The operation by means of the two keys  11  and  12  shall be explained in more detail in connection with  FIGS. 10 to 12 . The upper housing half  3  moreover comprises a display  17  as well as several stimulus generators. 
     The stimulus generators include a bright LED  15 , a buzzer  16  behind buzzer apertures, electrodes  24  and vibrators. The latter shall be explained in more detail in connection with  FIGS. 4 and 5 . These stimulus generators have the property that they are able to actively draw the user&#39;s attention to them. 7-segment displays, as are employed, for example, in the 9500 Onyx and in the DIGIT, do not represent stimulus generators in accordance with this application. One could also say that stimulus generators in accordance with this application are non-alphanumeric displays. However, this does not so clearly express the purpose of actively attracting the user&#39;s attention, and it does not include all of the embodiments according to the invention either, as will be explained below three paragraphs from here. 
     Usually, such 7-segment displays are multiplexed with a frequency of such an intensity that the human eye perceives a uniform light. Thus, the brightness fluctuates between 2/7 for a “1” and 7/7 for an “8”. In the case of two-digit displays and in the interesting range between 70% and 100% of the oxyhemoglobin content the fluctuations in the brightness on representing the numbers between 70 and 99 are far smaller. In addition, the numbers of the low-order position are periodically passed through three times, which is not suited to display the falling below a threshold. 
     Finally, the 7-segment displays in the 9500 Onyx and the DIGIT are oriented such that the displays are not visible in a relaxed position of the hand or during a number of activities such as driving, flying or hiking. 
     In order to transform conventional 7-segment displays into stimulus generators in accordance with this application, for example, the 7-segment display would have to be switched on and off in an alarm or warning range in a manner visible to the human eye, that is at a frequency between approximately 0.5 and 20 Hz, (compare  FIGS. 9 and 10 ). Alternatively or additionally, the 7-segment display could be switched off entirely in the green range  107 . Furthermore, the 7-segment display should be accommodated on the side of the finger clip pulse oximeter  1  next to the buzzer  16 . 
       FIG. 2  shows the lower housing half  2  and, specifically, the upper side thereof with the recess  5 . On the upper side one can see a light-emitting diode (LED)  21 , an infrared light-emitting diode (IRED)  22  and two electrodes  24 . The LED  21  together with IRED  22  form a radiation source emitting at least two light wavelengths. As will be explained in connection with  FIG. 4  below, the lower housing half  2  includes batteries or accumulators serving as energy sources. The electrodes  24  serve to generate by means of current pulses another type of stimulus alternatively or in addition to light and sound, so as to actively warn or alert the user. 
       FIG. 3  shows the upper housing half  3  and specifically the lower side thereof with the recess  5 . A photodetector  23  can be seen on the lower side. The photodetector  23  together with the LED  21  and the IRED  22  form an oximeter sensor in the narrower sense. The upper housing half  3  specifically comprises a board  26  with the evaluation circuit  25 . The lower and upper housing halves  2  and  3  are connected, for example, by a (non-illustrated) flat ribbon cable as to supply the evaluation circuit  25  with energy and control the LED  21 , the IRED  22  and the electrodes  24 . 
     In operation, the photodetector converts the red and infrared photons transmitted by the finger into electric signals as to determine in a manner known per se the content of oxyhemoglobin. The photodetector can be mounted opposite the LED  21  and the IRED  22  (compare U.S. Pat. No. 5,490,523 and U.S. Pat. No. 6,731,962) or offset opposite to the LED  21  and the IRED  22  (compare U.S. Pat. No. 5,800,349). To distinguish between red and infrared, the LED  21  and IRED  22  can be switched on in a phase-shifted manner. In another embodiment, the LED  21 , the IRED  22  and the photodetector  23  may be accommodated in the same housing half, so that the oxyhemoglobin content is determined by means of backscattered photons (U.S. Pat. No. 5,490,523 “reflective type pulse oximeter”). In this connection, one also talks about a reflection pulse oximeter or reflection sensor. 
       FIG. 4  shows a section through an embodiment of the lower housing half  2 . As was mentioned above, the lower housing half  2  includes above all the batteries  40  and  41  serving as energy sources. A spring  42  presses in a usual manner the battery  40  against a contact on the opposite side. The battery  41  moreover serves as inertial mass as to make the lower housing half  2  and thus also the upper housing half  3  vibrate. To this end, a motor  44  drives an eccentric  45 , on which a contact  46  is rotatably mounted. The contact moves the battery  41  with respect to the lower housing half  2  when the motor  44  with the eccentric  45  is rotated. The spring  43  thereby presses the battery  41  against the contact  46 , wherein the spring  43  is pressed together alternately stronger or less strongly. 
       FIG. 5  shows a section through another embodiment of the lower housing half  2 . Again, the lower housing half  2  comprises two batteries  47  and  48 , which are held in the lower housing half by means of springs on both ends. A coil  49  is accommodated between both batteries. Inside the coil there is located a mobile magnet  50 , which may be fixed to the housing by a bendable tongue. It is irrelevant as to whether the magnet  50  is clamped between the two batteries  47  and  48  free from play, or whether—as is shown in FIG.  5 —a small gap is provided between the batteries  47  and  48  and the magnet  50 . 
     Depending on the direction of the current flow in the coil  49 , the magnet  50  is pressed against the right battery  47  or the left battery  48  and moves the same. The batteries  47  and  48  experience a particularly great mechanical deflection if the coil  49  is operated with an alternating current, whose frequency corresponds to the mechanical resonance frequency of the batteries  47  and  48 . The mechanical resonance frequency of the batteries should, again, correspond to the desired vibration frequency. 
     In another embodiment, the batteries may be fixed by a spring to be mobile on one side only, or in the conventional manner, that is immobile with respect to the lower housing half  2 . In the latter case, then merely the magnet  50  serves as inertial mass. 
     The magnet  50  may be both a permanent magnet and an electromagnet, e.g. including a soft iron core. 
       FIG. 6  shows a lateral view of an inventive ear clip sensor  51 .  FIG. 6  shows a rear view of the ear clip sensor  51 . The ear clip sensor  51  comprises a clamp  54  for clamping an earlobe of a user. To increase the wearing comfort and to ensure a stable seat of the ear clip sensor  51  the ear clip sensor includes an ear bow  53  which, similar to a hearing aid, extends between the outer ear and the head upwardly and finally forwardly so as to transfer a force onto the outer ear. The ear bow  53  may be made of a thermoplastic material so as to adopt the shape of the ear bow to the anatomy of the user. The ear bow  53  may be hollow and comprise a sound aperture  52  on its end to warn or alert a user. The buzzer or loudspeaker for the generation of sound can be accommodated for example, in the inner half of the clamp  57  or in a thickened portion of the ear bow  53 . 
     In the outer half of the clamp  68  there are mounted an LED  61  and an IRED  62 . A photodetector  63  is accommodated in the inner half of the clamp  57 . The photodetector  63  can be located either opposite the LED  61  and the IRED  62 , or can be mounted to be offset opposite to the LED  61  and the IRED  62 . In other embodiments, the LED  61 , the IRED  62  and the photodetector  63  can be accommodated together either in the inner clamp  57  or the outer clamp  58  so as to determine the oxyhemoglobin content by means of the backscattering (reflection type). 
     Electrodes  64  mounted in the inner half of the clamp  57  and/or the outer half of the clamp  58  to touch, during the use, the skin of a user, specifically his earlobe, serve to warn or alert the user by means of current pulses. 
     An electric line  55  serves to connect the ear clip sensor  51  to a pulse oximeter. To achieve a better stability and higher wearing comfort the line  55  is fixed to the inner half of the clamp  57 . Via the line  55  the LED  61 , the IRED  62  and the electrodes  63  are controlled and the photodetector  63  is read out. 
     In another embodiment the halves of the clamp  57  and  58  may also accommodate batteries, an evaluation circuit, possibly even keys and a display for adjusting warning and alarm thresholds, thereby creating an ear clip pulse oximeter. In this case, the line  55  is dispensable. 
       FIG. 8  shows a top view of an inventive wrist pulse oximeter  71 .  FIG. 9  shows a section through the wrist pulse oximeter  71 . The wrist pulse oximeter  71  has the shape of a watch and is correspondingly worn on the wrist. It comprises the same stimulus generating means as the finger clip pulse oximeter  1 : a bright LED  75 , a buzzer  76 , an eccentric  85 , which simultaneously serves as inertial mass so as to make the wrist pulse oximeter  71  vibrate, as well as electrodes  84  to generate current pulses. As is shown in  FIG. 9 , the lower side of the wrist pulse oximeter  71 , which faces the wrist of the user, is provided with the reflection oximeter sensor including the LED  81 , the IRED  82  and the photosensor  83 . 
     On the upper side of the wrist pulse oximeter  71  there is moreover located a display  77 , which can be designed, for example, like the display  111  illustrated in  FIG. 11 . On a flat side of the wrist pulse oximeter  71  there are mounted a first key  72  and a second key  73 , by means of which, for example, warning and alarm limit values can be inputted. 
     In another embodiment, the wrist pulse oximeter  71  can also be provided with a finger clip sensor similar to the 3100 WristOx, which is connected to the wrist pulse oximeter by an electric cable. In this case, the wrist pulse oximeter can serve above all as a mechanical retaining device for the finger clip sensor so as not to get lost during work or practicing sports. The finger clip sensor may be smaller and lighter than a finger clip pulse oximeter because the batteries and the evaluation circuit can be accommodated in another housing. This increases the wearing comfort and reduces the risk of losing the finger clip sensor. In this embodiment, the stimulus generator or generators can be located in the wrist pulse oximeter and/or the finger clip sensor. 
       FIG. 10  shows the warning and alarm system for an inventive oximeter. In this three-dimensional diagram the oxyhemoglobin content is plotted on the SpO-axis  91 , the time (t) on the time axis  92  and the stimulus intensity generated by an stimulus generator on the stimulus axis  93 . In the diagram shown in  FIG. 10 , a warning threshold  94  is plotted at 93% of the oxyhemoglobin content and an alarm threshold  95  at 89% of the oxyhemoglobin content. 
     If the oxyhemoglobin content is above the warning threshold  94 , no stimulus is generated, which is illustrated by line  96 . If the oxyhemoglobin content is below the warning threshold  94 , but above the alarm threshold  95 , a warning stimulus  97  is outputted. This may be formed by periodically switching an stimulus on and off. The frequency or the pulse duty factor of the on-off switching, the frequency of a buzzer tone or a vibrator, the volume of the buzzer tone or the intensity of the vibrations may be chosen on the basis of the oxyhemoglobin content, thereby allowing to vary the intensity of a warning. If the oxyhemoglobin content falls below the alarm threshold  95 , an alarm by the stimulus generator or generators is outputted. The alarm may consist of a continuous stimulus, which is shown by line  98 . 
     It is known that especially at the edge of the vision range the human eye is more sensitive to changes in brightness and color, which are normally caused by movements in the environment. Therefore a blinking LED is suited better to attract the attention of a user than an LED which is switched on. In another embodiment especially with respect to optical stimuli, therefore, the warning can be represented by a switched on LED and the alarm by a blinking LED. 
       FIG. 11  shows the warning and alarm system for a pulse meter. On the pulse axis  101  the pulse is illustrated in beats per minute (bpm). On the stimulus axis  102  the stimulus intensity is represented. Moreover represented are a lower alarm threshold  106  at 60 bpm, a lower warning threshold  105  at 70 bpm, an upper warning threshold  103  at 150 bpm and an upper alarm threshold  104  at 160 bpm. Between the lower warning threshold  105  and the upper warning threshold  103  the green range  107  is provided, in which no stimulus is generated. If the pulse ranges between the lower alarm threshold  106  and the lower warning threshold  105  or between the upper warning threshold  103  and the upper alarm threshold  104  a warning  108  is outputted. If the pulse falls below the lower alarm threshold  106  or exceeds the upper alarm threshold  104 , an alarm  109  having about double the stimulus intensity of a warning  108  is outputted. 
     Similar to oximeters, the frequency or the pulse duty factor of the on-off switching of an stimulus, the frequency of a buzzer tone or a vibrator, the volume of the buzzer tone or the intensity of the vibrations may be chosen on the basis of the interval of the measured pulse from the green range  107 . 
     In one embodiment, the pulse meter, the oximeter or pulse oximeter can be manufactured with predefined warning and alarm thresholds. If the warning and alarm thresholds are to be adjustable, a display of the adjusted warning and alarm threshold is helpful. This can be readily achieved by a potentiometer with a scale to make the potentiometer position readable. Expediently, the scale shows the adjusted warning and alarm thresholds immediately. 
     However, the embodiments shown in  FIGS. 1 to 9  make use of two keys for adjusting the warning and alarm thresholds as well as a display for controlling the warning and alarm thresholds. 
     The pulse oximeters may have different modes of operation. In one mode parameters such as the warning and alarm thresholds may be adjusted, in the other one the measured values are displayed. The displays  17  and  77  shown in  FIGS. 1 and 8  may be designed like the display  111  shown in  FIG. 12 . 
     The display  111  comprises an oxyhemoglobin section  112 , a pulse section  113 , various indicators  114  to  120  as well as a volume bar  121 . In the oxyhemoglobin section  112  either the oxyhemoglobin concentration or the warning or alarm threshold  94  or  95 , respectively, are displayed. In the pulse section  113  either the pulse or the lower or upper warning and alarm threshold  104 ,  103 ,  105 ,  106  are displayed in bpm. The volume bar  121  generally shows the intensity of an stimulus in the event of an alarm or warning. Specifically, the volume of a buzzer  16  or  76  is envisaged. It is important that the stimulus intensity, that is the volume, cannot be set to zero because this would be equal to deactivating a warning. 
     As to what is displayed where, and what meaning the two keys have, is shown by the indicators  114  through  120 . If none of the indicators is dark, like indicator  118  in  FIG. 12 , the apparatus in the measurement mode and the oxyhemoglobin concentration is displayed in the oxyhemoglobin section  112 , the pulse is displayed in the pulse section  113  and the volume is displayed in the volume bar  121 . By briefly pressing the first key  11  or  72  the apparatus is transferred into the setting mode. Now, first the indicator  114  turns dark. Each further brief pressing of the first key results in a cyclic advancement from indicator to indicator. If the first key is pressed long, altered warning and alarm thresholds are stored and used in the later operation. If no key is pressed for 10 seconds, the apparatus returns to the measurement mode without storing new warning or alarm thresholds. On pressing both keys, the apparatus is switched on or off. 
     On pressing the second key the parameter just selected, which is displayed by the corresponding indicator, is cyclically advanced by one step. If the second key remains pressed down, the parameter selected can be advanced after 3 seconds by one step per second. The advancing frequency can be increased with the duration of maintaining the second key in a pressed position. 
     The warning or alarm value corresponding to the dark indicator is displayed in the corresponding section and can be altered by pressing the second key. The “A” right of an indicator stands for alarm threshold. The “W” right of an indicator stands for warning threshold. The arrangement of the indicators in the display  111  corresponds to the arrangement of the warning and alarm thresholds in  FIGS. 10 and 11 . 
     If one of the indicators  114  or  115  is dark, the level of the warning threshold  94  or the level of the alarm threshold  95 , respectively, is displayed in the oxyhemoglobin section  112  and can be altered by pressing the second key. The warning threshold can thereby be set in 1%-steps between 100% of the oxyhemoglobin content and the alarm threshold. The alarm threshold can be set in 1%-steps between 100% and 70% of the hemoglobin content. 
     If one of the indicators  116 ,  117 ,  118  or  119  is dark, the level of the upper alarm threshold  104 , of the upper warning threshold  103 , of the lower warning threshold  105  and the lower alarm threshold  106 , respectively, can be adjusted. The lower alarm threshold can be adjusted in a range of 40 bpm to 230 bpm. The upper alarm threshold can be adjusted in a range from the lower alarm threshold to 230 bpm. The lower warning threshold can be adjusted in a range from the lower alarm threshold to the upper alarm threshold. The upper warning threshold can be adjusted in a range from the lower warning threshold to the upper alarm threshold. 
     If the indicator  120  is dark, the volume can be adjusted by pressing the second key. The control range can range from 10% to 100% of the maximally obtainable volume bars. In addition, there may be provided other bars and corresponding indicators for the adjustment of the other stimuli, that is the brightness of the LED, the intensity of the current pulses and the intensity or frequency of the vibrations, with the aid of the second key. With respect to the stimuli, especially the volume, it is recommendable to select the step sizes logarithmically. 
       FIG. 13  shows a joystick  130  according to the invention for aircraft and helicopters. In each horn of the joystick  130  there are accommodated a reflection pulse oximeter sensor comprising the LEDs  131  and  141 , respectively, the IREDs  132  and  142 , respectively, and the photodetectors  133  and  143 , respectively. Besides, each horn includes electrodes  134  and  144  for generating electric stimuli. Moreover, a bright LED  135  and  145 , respectively, for generating optical stimuli is provided on each horn. The actual pulse oximeter can be mounted outside the joystick  130 . Connecting cables may be passed through the joystick bearing  146 . The pulse oximeter may be connected to the sound system of the aircraft or helicopter, which substantially consists of a transceiver and perhaps an intercom system. Thus, warnings or alarms can also be issued via the headset worn by the pilots. 
     Similar to the joystick  130  pulse oximeters can also be mounted on their own or in combination with stimulus generators in other operating elements, such as bicycle or motorcycle handlebars or steering wheels for cars and commercial vehicles. 
       FIG. 14  shows a helmet  150  according to the invention. The helmet serves as a holder for a reflection pulse oximeter sensor, which consists of the Led  151 , the IRED  152  and the photodetector  153  and measures the oxyhemoglobin content in the forehead of the pilot. Electrodes  154  can generate electric stimuli. The LED  155  together with the visor  157  can generate optical stimuli. The reflection pulse oximeter sensor, the electrodes  154  and the LED  155  are connected by an electric line  165  to an appropriate pulse oximeter, which may be connected to the sound system of the aircraft or helicopter so as to issue acoustic warnings or alarms via the line  159  and the headset earpiece  156 . 
     Similar to the helmet  150  pulse oximeters can also be mounted on their own or in combination with stimulus generators in other articles of clothing, e.g. gloves or boots. 
     Above, the invention was explained in more detail by means of preferred embodiments. A person skilled in the art will appreciate, however, that various alterations and modifications may be made without departing from the spirit of the invention. Therefore, the scope of protection will be defined by the claims and their equivalents set forth below. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  finger clip pulse oximeter 
           2  lower housing half 
           3  upper housing half 
           4  spring 
           5  recess 
           11 ,  12  keys 
           13 ,  14  groove 
           15  LED 
           16  buzzer 
           17  display 
           21  LED 
           22  IRED 
           23  photodetector 
           24  electrodes 
           25  evaluation circuit 
           26  board 
           40 ,  41  battery 
           42 ,  43  spring 
           44  motor 
           45  eccentric 
           46  contact 
           47 ,  48  battery 
           49  coil 
           50  magnet 
           51  ear clip sensor 
           52  sound aperture 
           53  ear bow 
           54  clamp 
           55  line 
           57  inner half of clamp 
           58  outer half of clamp 
           61  LED 
           62  IRED 
           63  photodetector 
           64  electrodes 
           71  wrist pulse oximeter 
           72 ,  73  key 
           75  LED 
           76  buzzer apertures 
           77  display 
           81  LED 
           82  IRED 
           83  photosensor 
           84  electrodes 
           85  eccentric 
           91  SpO-axis 
           92  time axis 
           93  stimulus axis 
           94  warning threshold 
           95  alarm threshold 
           96  no stimulus 
           97  warning stimulus 
           98  alarm 
           101  pulse axis 
           102  stimulus axis 
           103  upper warning threshold 
           104  upper alarm threshold 
           105  lower warning threshold 
           106  lower alarm threshold 
           107  green range 
           108  warning 
           109  alarm 
           111  display 
           112  oxyhemoglobin section 
           113  pulse section 
           114 - 120  indicators 
           121  volume bar 
           130  joystick 
           131 ,  141  LED 
           132 ,  142  IRED 
           133 ,  143  photodetector 
           134 ,  144  electrodes 
           135 ,  145  LED 
           146  joystick bearing 
           150  helmet 
           151  LED 
           152  IRED 
           153  photodetector 
           154  electrodes 
           155  LED 
           156  headset earpiece 
           157  visor 
           159 ,  165  line