Blood pressure monitor with compensation for physique and method of use

An automated blood pressure measurement apparatus and method which includes an inflatable cuff at a predetermined height relative to where a user must sit or stand in order to comfortably use the apparatus including a correction arrangement which provides a numerical correction for a hydrostatic pressure differential between the heart level of a user in a posture implied by the predetermined height of the cuff based on the user's overall height and a standard posture for measuring blood pressure at which the cuff height is at approximately the same level as the heart level when blood pressure is measured.

TECHNICAL FIELD 
This invention relates to devices for determining physical condition. In 
particular, this invention relates to automated blood pressure testing 
apparatus for use by the public and specifically to devices of that type 
which include the facility of providing a correction for variations in 
physique and/or posture of the user. 
BACKGROUND ART 
Blood pressure has long been known as an important factor in the evaluation 
of the general level of health of an individual. Blood pressure is 
typically measured by a so-called auscultatory method using a 
sphygmomanometer where an inflatable cuff is placed over an extremity of a 
subject and inflated to a pressure at which circulation is halted in the 
extremity and then deflated while the subject's pulse and circulation are 
aurally monitored with a stethoscope or the like. Since the inflatable 
cuff imposes pressure on the extremity against the natural elasticity of 
the flesh of the extremity, the circulation in different depths below the 
surface of the flesh in the extremity will be affected at different 
pressures. Upon deflation after circulation is halted in the extremity, 
circulation will resume in deep tissues at a first pressure, referred to 
as the systolic pressure, reflecting the maximum pressure developed by the 
heart and at a second, lower pressure, known as the diastolic pressure, in 
the shallow tissues near the surface of the extremity which reflects the 
minimum pressure against which the heart must work. 
When the above procedure is performed, it is necessary for it to be 
performed by a person other than the person whose blood pressure is being 
measured since muscular tension necessary to control deflation of the cuff 
or to position a listening device such as a stethoscope will affect the 
accuracy of the measurement. Also, the ability to hear the differences in 
circulation will be reduced, since circulation in the ear of the user will 
mask the subtle changes in the sounds caused by changes in circulation in 
the extremity during control thereof by the inflatable cuff. 
In recent years, the increase in "health-consciousness" on the part of some 
individuals has led to the development of personal automated devices for 
measuring blood pressure and pulse rate. While the cost of such devices is 
not great and their availability is reasonably widespread, such devices 
are likely to be regarded as unnecessary or a luxury for private ownership 
unless strongly recommended by a physician having already diagnosed 
hypertension in the individual. Thus, such devices are not likely to 
result in the discovery of hypertension or other conditions for which 
treatment should be sought. 
On the other hand, it has become increasingly apparent in recent years that 
hypertension, or elevated blood pressure, is a major, generally 
undiagnosed, condition since it is not accompanied by symptoms which would 
typically lead an individual to seek medical attention. Over a period of 
time, undiagnosed or untreated hypertension may cause substantial damage 
or degeneration to the heart and circulatory system. Such undiagnosed 
and/or untreated hypertension has been found to be a major factor in the 
development of heart disease or the occurrence of heart attacks. Further, 
abnormal blood pressure may be a major indicator of the existence of an 
aneurism, an enlargement of a blood vessel which has an increased 
likelihood of bursting with often catastrophic consequences and high 
mortality rate. 
To provide such availability of blood pressure testing, it has become 
common for medical institutions such as hospitals to provide screenings 
for high blood pressure and other conditions. Such screenings have the 
advantage of providing trained personnel to test and counsel large numbers 
of people. However, such screenings are expensive to the institution 
providing them and involve administrative and other expenses such as 
advertising and publicity. While such screenings have been fairly 
successful at raising public awareness of particular health problems, they 
often do not succeed in promoting follow-up testing or treatment, 
particularly where the physical parameter tested is subject to wide 
variation due to many causes, as is the case with blood pressure. Further, 
there may be a perceived lack of confidentiality in such screenings and 
the potential adverse effects of seeking information concerning 
hypertension on insurance premiums may deter an individual from seeking 
information concerning his or her condition. 
Accordingly, it has recently become apparent that there is a need for the 
ready availability to the public of apparatus to measure blood pressure. 
Such availability provides the equivalent of screening by trained 
personnel, which, while generally accurate and offering the possibility of 
providing advice and counseling when results are abnormal, suffers from 
the drawbacks of expense, irregular and inconvenient availability, a 
perceived lack of privacy and confidentiality and the likelihood that a 
significant result will be dismissed by the subject due to the unusual 
circumstances of the screening itself. It is also well-known that 
hypertension cannot be reliably diagnosed on the basis of a single blood 
pressure measurement but requires several consistently high measurements 
to reliably indicate the condition. 
Even after diagnosis of hypertension, it is necessary to periodically 
monitor blood pressure. The expense or inconvenience of obtaining such 
measurements may impede or interfere with treatment. Even the personal 
blood pressure monitors alluded to above may constitute a relatively large 
expense and an alternative to ownership of such a device is necessary. 
Recently, therefore, it has been found to be effective in the early 
detection of hypertension to provide automated blood pressure testing 
apparatus in public places either as a public service or on a pay-per-use 
basis. This has been found to be particularly effective in pharmacies and 
other commercial establishments which also distribute prescription 
medications because of the availability of a pharmacist who can give 
independent confirmation of the need to consult a physician if blood 
pressure measurements are consistently high. Installation of such 
automated blood pressure measuring devices has also been found to be 
beneficial to the commercial establishments providing them and such 
installations have proven to be a substantial source of income when 
installed on a pay-per-use basis as well as enhancing sales of other 
products. Such installations allow blood pressure tests to be done 
conveniently and at intervals over a substantial period of time and with a 
fairly high degree of confidentiality. 
One example of a suitable device is disclosed in U.S. Pat. No. 4,729,382, 
filed on Sept. 2, 1986, and issued to joint inventors herein Jon D. 
Schaffer and George L. McDade entitled METHOD AND APATUS FOR 
AUTOMATICALLY DETERMINING PULSE RATE AND DIASTOLIC AND SYSTOLIC BLOOD 
PRESSURE which disclosure is fully incorporated by reference herein. 
Details of the operation of the basic device which are not necessary to a 
full understanding of the present invention are omitted herein in the 
interest of clarity and full disclosure of such details may be found in 
the patent incorporated by reference. 
With regard to the basic device, it has been found that, for installation 
in a commercial establishment, a stand is desireable due to the high cost 
of floor space. Further, and for the same reason, it has been found 
desireable to provide such a stand which allows the basic device to be 
used when the user is in a standing position. Use in a standing position 
is also desireable since the device can be used less conspicuously in a 
store environment where it is unusual for a customer to sit. However, such 
an installation presents a problem since the standing posture of a user is 
not typical of standard postures in which blood pressure is commonly 
measured. Specifically, when done by medical personnel, blood pressure is 
typically measured at the upper arm with the subject either seated or 
recumbent so that the inflatable cuff used in the measurement will be 
located at heart level. It is highly desireable, in this regard, 
considering potential use by users who may be screening themselves for 
hypertension and those who use the device as an aid to medical treatment 
that the measurements made by the device be accurately and consistently 
correlated with measurements made by trained medical personnel using 
sphygmomanometers. It has also been found to be desireable that the 
inflatable cuff be rigidly mounted to the housing of the device as shown 
in U.S. Patr. Des. No. 298,167, filed Dec. 6, 1985, and also issued to 
joint inventors herein Jon D. Schaffer and George L. McDade. This 
arrangement provides for protection of pneumatic parts which are 
vulnerable to tampering and vandalism and permits the pressure cuff, pump 
and valves to be assembled in a module which can be readily replaced for 
ease of servicing in the field. The device is also intended to take blood 
pressure measurements from the forearm of the user which has been found to 
be highly accurate in accepted invasive methods of blood pressure 
measurement using an arterial catheter. Use of the forearm of the user for 
blood pressure measurements is also a matter of convenience to the user, 
particularly in the intended application, since a comfortable and natural 
posture can be maintained which does not draw attention to the user. For 
much the same reasons, and also the additional fabrication and possible 
maintenance expense involved, it is not deemed to be reasonably practical 
to provide for alteration of the height of the entire machine in an 
attempt to standardize posture since that effect would not be achieved in 
any event without substantial other structure impeding ease and 
discreteness of use. Further, use of the forearm does not require the 
upper arm to be exposed and therefore does not require sleeves to be fully 
rolled up, thus avoiding the binding effect of clothing which may affect 
measurement results. However, unlike techniques using the upper arm, the 
cuff is not assured to be at or near heart level and, therefore, errors 
due to differences in hydrostatic pressure due to the difference in height 
between the heart and the inflatable cuff may cause substantial 
differences between the actual measurement made and the value which would 
have been obtained if the subject were in a more standard position or 
posture for measurement of blood pressure. 
DISCLOSURE OF THE INVENTION 
Accordingly, it is an object of the invention to provide a method of 
correcting for differences in hydrostatic pressure caused by differences 
between the levels of the user's heart and that of the inflatable cuff 
during blood pressure measurement during use of an automated blood 
pressure measurement apparatus. 
It is another object of the invention to provide a correction method for 
correction of blood pressure measurements for hydrostatic pressure errors 
based on a parameter which would be readily known to the user or which can 
be easily sensed. 
It is a further object of this invention to provide a blood pressure 
measurement apparatus which determines the posture of the user in a 
discreet, comfortable and natural manner and permits correction for 
hydrostatic pressure differential to be made in a simple and 
straightforward manner. 
It is yet another object of the invention to provide an improvement in an 
automated blood pressure measurement apparatus which occupies little floor 
space even when in use but will provide an output which is accurately 
correlated with blood pressure measurements made in standard postures by 
the use of auscultatory techniques and sphygmomanometers operated by 
trained personnel. 
Therefore, in accordance with one aspect of the invention, a method is 
provided comprising the steps of operating a data entry means to enter 
data corresponding to the height of a user, inserting the lower arm of the 
user within an inflatable cuff, causing an apparatus to measure the blood 
pressure of the user, and correcting the measurement result in accordance 
with the height of the user to derive a corrected result. 
In accordance with another aspect of the invention, a method is provided 
comprising the steps of establishing a correction relationship between at 
least average heights of heart levels relative to user heights and a 
predetermined height of an inflatable cuff and measured blood pressure 
values measured in a standard posture, obtaining data representing the 
height of a user, measuring the blood pressure of the user to derive a 
measurement result, and correcting the measurement result according to the 
correction relationship to obtain a corrected measurement value. 
In accordance with a further aspect of the invention, an apparatus is 
provided comprising an inflatable cuff for encircling a portion of a user 
and mounted at a predetermined height relative to a support for said user, 
a controllable fluid pump apparatus for controllably inflating and 
deflating the inflatable cuff, pressure measuring apparatus responsive to 
variations in pressure in the cuff during said inflating and deflating 
thereof and providing a measurement result, a device for providing data 
representing an overall height of the user, an apparatus for providing a 
correction relationship between average blood pressure of a typical user 
in a predetermined posture determined by the height of the user and the 
predetermined height of the inflatable cuff and a standard posture, and 
apparatus for correcting said measurement result based upon said overall 
height data of said user and said correction relationship and providing a 
corrected measurement value. 
In accordance with yet another aspect of the invention, an improvement 
comprising a data entry device for inputting data representative of a 
parameter of the physique of the user and including a device responsive to 
the data entry means for applying a correction to the output of a 
measuring means to correct the output thereof is provided for an automated 
blood pressure measurement apparatus. 
The attainment of the above and other objects of the invention will become 
apparent to those skilled in the art in light of the following detailed 
description of the invention in connection with the attached drawings 
which will fully enable any person skilled in the art to make and use the 
same.

BEST MODE FOR CARRYING OUT THE INVENTION 
FIG. 1 shows the overall appearance of the apparatus according to the 
invention. The physical arrangement of the invention 10 includes a base 15 
which can advantageously include a scale 15b for measuring the weight of 
the user. Housing 11, including a mounting position for an inflatable cuff 
12, a display, which is preferably digital in nature, and keyboard 13 is 
supported on posts 14. Panel 16 can be used to display written 
instructions, blood pressure information and interpretive data or even 
advertising matter for perusal by the user during operation of the blood 
pressure testing apparatus. The housing 11 may advantageously be made in a 
divided manner as illustrated at division 18 so that the pump, valves, 
cuff and pressure sensors are contained in a single module for ease of 
service and field replacement. While the entire unit, constructed 
according to the invention, has been found to be of relatively light 
weight and easily portable, the overall size of the device may be somewhat 
awkward to move when relocation is required, and wheels (not shown) may be 
provided at one edge of the base to allow the device to be tilted and 
rolled on the wheels but stable and stationary when upright. The 
configuration of the base is not critical and dimension 15a is typically 
determined to accommodate a treadle for a scale, as noted above. If a 
scale is not included, the base may be of any desired construction, such 
as that illustrated in FIGS. 2A-2C, which will offer good stability and 
rigidity and may permit the user to stand on the floor upon which the 
invention is also placed. 
Speaker 17 can be used for messages or instructions in any desired language 
and for voice-synthesized reporting of the test results, if desired, in a 
manner well known in the art. In the preferred embodiment, such voice data 
is held in read-only-memory for rapid access, freedom from mechanical and 
aging deterioration (as compared, for instance, to tape) and rapid 
interchange of messages (for other languages, for instance) if desired. 
This feature is also advantageous for use of the apparatus by the blind or 
visually impaired. Location of speaker 17 is not critical to the practice 
of the invention and can be located at any position deemed convenient. 
Posts 14 extend through base 15, of whatever form may be chosen, and 
terminate at approximately floor level. Due to the flexure angle of the 
human elbow, the apparatus is arranged and the post length determined to 
place the cuff 12 at a level which is at heart level for a user several 
inches shorter than average human height. The dimension adopted in the 
preferred embodiment of the invention accommodates a user of a minimum 
height of 64 inches. This design feature has the advantage that all blood 
pressure corrections for taller (or slightly shorter, as will be discussed 
below) persons will be done by a subtraction of hydrostatic pressure, thus 
simplifying the programming of microprocessor 20. It has also been found 
that using software to provide a set of corrections for a specific height 
of cuff 12 is sufficiently simple that custom adaptations to different 
cuff heights may be easily done if necessary. Therefore, for the 
predominant number of installations it has been found economical to 
standardize heights of posts 14 and to provide different corrections in 
software for the thickness 15a of base 15, if, in fact, the base is used 
to support the user during blood pressure testing. 
Housing 11 may also be advantageously adapted to be easily removable from 
posts 14 so that persons of shorter stature may be accommodated with 
housing 11 placed on another support which will allow such a user to 
assume a nearly standard blood pressure measurement posture, in which 
case, the default user height value of 64 inches will yield an accurate 
result regardless of the actual height of the user. Alternatively, a user 
of short stature may be supported by a base or other support arrangement 
to a height where a standard posture is approximated. 
Finally, it is noted that the preferred form of housing 11 is also not 
critical to the practice of the invention and details thereof are omitted 
in the interest of clarity. However detailed illustration of a preferred 
form of the housing are fully illustrated in U.S. Pat. Des. No. 298,167, 
cited above and hereby incorporated by reference for purposes of full, 
detailed illustration of the housing 11. 
FIGS. 2A, 2B and 2C illustrate the use of the invention by users of 
differing heights. FIG. 2A shows use by a person of the minimum exemplary 
design height. In this case, the inflatable cuff is at heart level and the 
user assumes a comfortable, upright position with the user's forearm 
inserted in cuff 12. The upper arm assumes a comfortable upward angle to 
the user's shoulder. Also, in this case, no correction for hydrostatic 
pressure is required since the cuff is at heart level. 
In FIG. 2B, the user is depicted as being of greater than minimum design 
height for the cuff position and the heart level will be above the center 
line of the cuff by a distance 30b. While the upper arm of the user rises 
at a sharper angle, this posture is still upright and comfortable. The 
height differential 30b will cause the measured blood pressure to be 
increased by the hydrostatic pressure corresponding to distance 30b and 
correction will be made by the invention in a manner which will be 
explained below. 
FIG. 2C illustrates the use of the apparatus by a user much taller than the 
minimum height for which the apparatus is designed. In this case, if the 
user were standing upright, the heart level would be above the center line 
of the inflatable cuff by a distance 31. However, the user will assume the 
most comfortable position which is slightly bent at the knees and waist. 
Correspondingly, heart level for such an individual will be brought to a 
level which is a distance 30c above the centerline of the cuff which is 
less than distance 31 and, hence, a smaller correction will be necessary 
for distance 30c than for distance 31. 
Comparing FIGS. 2A-2C, it is seen that a non-linear correction function may 
be advantageously employed and is, in fact, used in the preferred 
embodiment of the invention. This fact also effectively provides a limit 
of the maximum height for which correction will be required. 
FIG. 3 schematically illustrates a preferred embodiment of the invention. 
The figure is very similar to FIG. 1 of U.S. Pat. No. 4.,729,382, cited 
and incorporated by reference above. Reference may be made to the 
disclosure of that document for details of the operation thereof. 
While the programming of the microprocessor, according to the present 
invention is deemed to be within the level of one skilled in the art, in 
view of the functions disclosed and the description of the operation of 
the invention given below, the basic microprocessor operations which are 
used in the practice of the invention will be explained with reference to 
the flow chart illustrated in FIGS. 5A-5G. As shown in FIG. 5A, upon 
energization of the apparatus of the invention, all peripheral devices, 
such as the display, inputs, outputs and clock, are initialized, as shown 
at 51. Subsequently, as is common in microprocessors, variables are 
initialized (52), interrupts are enabled (53) and sensors are read for 
zero valued output (54). Once this is done, memory is interrogated to 
obtain the user definable configuration of the apparatus. This step of 
obtaining the configuration, 55, is typically used to configure the 
apparatus for free use or pay-per-use operation. This step is also used to 
set defaults such as voice-synthesized prompts, language, etc. 
Once the system configuration is established, the scale (if used) 
calibration is checked (56) and the sensor outputs are checked for 
zero-valued outputs (57). If these values are not within a predetermined 
range (58), a branch is taken to announce the error 58a and to obtain zero 
values 58b. If the sensor values have a zero value, the process continues. 
Referring now to FIG. 5B, flags in the microprocessor are initialized (61) 
and an idle loop is entered as designated by D and step 62. In this idle 
loop, the timers are periodically updated (63) and the sensors are 
rezeroed (64). After each performance of this check of inputs, the system 
is interrogated for a message (65) which may be installed as defined by 
the configuration of the system. This feature allows the apparatus to 
periodically draw attention of customers and to solicit use. If so, an 
announcement will be made by a voice annunciator or by display. Whether or 
not a message is installed, the process continues with an interrogation of 
the keyboard for an entry of user height data. If not, the idle loop 
continues at B. 
The following steps of the idle loop are shown in FIG. 5C. Step 71 
interrogates a stop switch on the keyboard which interrupts any continuing 
speech synthesis or display and resets flags to effectively alter the 
default configuration of the apparatus as shown at 71a and 71b. The 
keyboard is then interrogated 72 to determine if a key has been actuated 
to request operating instructions for the apparatus. If so, default flags 
are reset and instructions are displayed or announced by voice-synthesis, 
as noted above. Then the keyboard is again interrogated 73 to sense 
depression of the start switch. If so, but no instructions are input 74, 
the user is again prompted to press the start switch 74a. After either of 
conditional branches 73 or 74 is performed, the process continues with 
further interrogation of the keyboard to determine if a weight inquiry has 
been made 75. If so, a subroutine 75a is entered to display the weight 
data, if requested, after which the weight data and display are again 
updated 76, 77 and the idle display is resumed and a reminder message 
concerning the blood pressure test capability of the apparatus is given. 
After the reminder message or if the weight display is not selected, the 
idle loop resumes at D of FIG. 5B. 
In the idle loop, if the interrogation of the keyboard at 66 to determine a 
height entry is successful, a branch is made to the procedure illustrated 
at FIG. 5D, as indicated by legend E. Upon taking this branch, the timer 
for the blood pressure (and pulse) test is reset to zero 84 and flags are 
reset 85 for the blood pressure test. At this point, the stop switch is 
interrogated to allow a user to abort the test at an early stage thereof. 
This early opportunity to abort the test is deemed to be helpful in 
instilling confidence of the user. This procedure also is a conditional 
aborting of the test since step 81 requires two actuations of the stop 
switch to return the system to the idle loop at D in FIG. 5B. If the stop 
switch has been pressed only once, flags are interrogated to determine if 
height data has been entered 82. If not, a prompt is given to enter height 
data. Afterwards or if height data has been entered previously, a prompt 
to press the start switch is given. If height data has been entered at 
this point, the timer and flags are reset 88, 89 in anticipation of 
resuming the test. In either case, displays are reset and the procedure 
continues at F. 
Referring now to FIG. 5E, the instructions switch is again interrogated 
and, in response, the user is instructed 92 to insert his or her forearm 
into the inflatable cuff and to press the start button 93. If instructions 
have not been requested, a timer is interrogated 94 to determine if the 
user should be prompted again. If this prompt is determined to be 
required, entry of height data is again tested 95 and a prompt to enter 
the same 95a is again issued, if necessary. The user is again prompted to 
insert his or her forearm into the inflatable cuff 95b and to press the 
start button 95c. If this is not done within a predetermined period, 
governed by a timer, the idle loop may again be entered at 96 by a branch 
to D in FIG. 5B. If height data has been entered, but the start switch has 
not been pushed, weight data, if provided, is obtained and the process is 
resumed at E of FIG. 5D which again allows for early termination of the 
test. If the start key has been actuated, a branch is made to G of FIG. 
5F. 
Referring now to FIG. 5F, the process of the blood pressure test is 
conducted. Flags are reset 101, displays are updated 101a, counters are 
updated 101b valves, shown in FIG. 3 or 4 are closed, as disclosed in U.S. 
Pat. No. 4,729,382, and inflation of the inflatable cuff is initiated 102. 
While the cuff is being inflated, further instruction or messages of 
reassurance may be issued (102a). Inflation is checked 103 and any 
malfunction is reported and the idle loop is resumed if the cuff inflation 
fails. If cuff inflation is successful, the pump is turned off 104 and any 
further installed message 105 is communicated and bleed down o the cuff 
and data gathering 106 is started. 
At step 106, the user is given another opportunity to abort the test 107 
while data is being collected at step 106. If the stop switch is now 
actuated, termination of the test is announced 107a and the idle loop is 
resumed at D. If the test is not stopped, the bleed down of the cuff is 
monitored 108 and if an error is detected, a bleed down failure is 
announced 108a and the idle loop is resumed at D of FIG. 5B. If the bleed 
down is successful, completion of the test is announced with other desired 
messages such as a disclaimer at step 109. 
Referring now to FIG. 5G, the measured blood pressure (and pulse rate) are 
computed and fetched from A/D converters of FIG. 3, if used, at step 111. 
Correction data is now fetched from memory as specified by the keyboard or 
other data entry means and a correction is made at step 112, responsive 
thereto. Accuracy of the blood pressure, pulse rate and error correction 
computation is monitored at 113 and an error message is issued 113a and 
display is cleared (113b) if the correction is not properly performed. If 
no error is detected, results are displayed (113c). In either case, the 
test, whether or not successful, is now complete and flags are reset 114 
and the idle loop is reentered through A of FIG. 5B. 
According to the present invention, a keyboard which preferably includes a 
numerical keypad and a plurality of control switches, such as for turning 
off the voice-synthesized annunciation of instructions and results or 
controlling other options, thereof, is substituted for the start/stop 
switch of the cited device. Keyboard 13 may be advantageously selectively 
illuminated to prompt a user to enter data and to exercise control in a 
proper sequence as is well known in the art. Analog-to-digital converters 
are also provided to digitize the outputs of sensors 22 and 23. Memory 21 
is also included, preferably in the form of a ROM chip possibly in the 
form of an EPROM used as a look-up table for the purpose of holding 
numerical data representing a correction relationship which has been 
either theoretically or empirically determined for providing correction 
numbers in mmHg to be subtracted from measured blood pressure values to 
correct for the hydrostatic pressure caused by differential heights 30b 
and 30c of FIGS. 2B and 2C, respectively. Memory 21 can also be a portion 
of memory storing the program for the microprocessor. The apparatus 
according to the preferred embodiment of the invention also includes 
display 19. 
In operation, an operator will activate the apparatus by pressing a 
designated key of keyboard 13 to terminate a stand-by state of the 
apparatus. When this is done, the apparatus, under control of 
microprocessor 20 will prompt the user to enter his or her height either 
by display or voice annunciator. If this is not done after repeated 
prompts, a default at the minimum design height for a user is adopted. 
This feature provides a safety function since the output blood pressure 
value will be higher than if corrected since no correction is performed 
for a user of the minimum height for which the apparatus is intended. 
Alternatively, user height can be determined by direct measurement as by a 
mechanical arm or optical sensing in a manner well known in the art. 
After data is obtained to specify the user's height, the test may be 
started by the user in the manner disclosed in U.S. Pat. No. 4,729,382. 
The user can also abort the test should inflation of the cuff be 
uncomfortable. The data obtained regarding the height of the user is used 
to address memory 21 which outputs correction numbers stored therein which 
are then subtracted from the digital outputs of analog-to-digital 
converters 24 and 25, responsive to sensors 22 and 23. The result of the 
measurement, thus corrected, is displayed on display 19. 
The data held in memory 21 can be theoretically developed on the basis of a 
correction of an average variation of 1.5-2 mmHg per inch of height with a 
somewhat smaller correction for heights near the minimum design height and 
heights above 74", where postures similar to that of FIG. 2C will be 
assumed by the user. The data can also be determined empirically and the 
following Table I provides data which has been experimentally found to 
provide a good correlation with blood pressure measurements taken in more 
standard postures. 
TABLE I 
______________________________________ 
Height of User Correction 
______________________________________ 
62" +2 mmHg 
64" 0 
66" -2 
68" -6 
70" -9 
72" -12 
74" -14 
76" -16, etc. 
______________________________________ 
In an alternative embodiment, shown in FIG. 4, which is also similar to 
FIG. 1 of U.S. Pat. No. 4,728,382, the keyboard entry of height data to 
the microprocessor is used to control a multiplication factor of the 
analog-to-digital converters preferably in a non-linear manner which is, 
per se, well-known in the art. In this case, the output of the D/A 
converters will already be corrected for the height of the user and can be 
directly displayed under control of the microprocessor. 
It should be noted from Table I above that corrections need only be 
provided for two inch increments of height to provide resolution of 
measurement which is well within accepted medical standards. For instance, 
the above table, when implemented in the invention has a mean accuracy 
.+-.3 mmHg which is the standard accepted by the AAMI (Association for 
Advancement of Medical Instrumentation). Most physicians accept a mean 
accuracy of .+-.10 mmHg for non-invasive testing. Since the total number 
of necessary correction data is small, the use of a look-up table is the 
preferred form of implementation of the invention although others, such as 
that of FIG. 4, discussed above and others, such as dedicated digital 
display decoders are certainly possible alternative means of accomplishing 
the numerical correction function. 
It should also be noted from Table I that it may be desireable to provide 
additive corrections to allow for use by persons having a height slightly 
less than the design height of the apparatus since the apparatus of the 
invention can be used with reasonable comfort with the user's arm fully 
extended at shoulder height, yielding a hydrostatic reduction in measured 
blood pressure which must be compensated by increasing the measured value. 
Other variations on the basic invention are also possible to improve the 
function and accuracy thereof, should different standards be required. For 
instance both the measured blood pressure and height data could be used 
together to address the look-up table to improve the ability of the 
invention to conform to empirical data. In this case, subtraction would 
not be necessary and the value obtained from the look-up table could be 
directly displayed. Other variables reflecting stature, such as weight, 
could also be utilized to used to obtain correction data. 
Having thus fully described the invention, other variations will become 
apparent to those skilled in the art without departing from the spirit and 
scope of the present invention. For instance, as noted above, the 
apparatus of the invention may be combined with other transducers for 
independent or combined readout of other physical parameters such as 
weight; which parameters may also be interrelated under control of the 
microprocessor to provide a more detailed health and condition evaluation. 
Accordingly, it is intended that the above description of the invention be 
taken as by way of example and not of limitation, the scope of the 
invention being defined solely by the appended claims.