Bioinstrumentation system for cardiovascular measurements in tilt-table tests, and bedside monitoring during bedres

Cardus, D.

Hallen, T. O.

Holt, T. W.

Lamonte, R. J.

Mc Connell, J. R.

Spencer, W. A.

Vallbona, C.

Vogt, F. W.

English

NASA Technical Reports Server

Y 
NASA CR- 173 
8 .  , 
THE EFFECT OF BEDREST ON VARIOUS PARAMETERS 
OF PHYSIOLOGICAL FUNCTION 
PART 111. BIOINSTRUMENTATION 
By F. B. Vogt, J. Lamonte, J. R. McConnell, T. 0. Hallen, 
C. Vallbona, . Cardus, W. A. Spencer, and T. W. Holt b 
Distribution of this  report  i s  provided in the interest of 
information exchange. Responsibility for  the contents 
res ides  in the author o r  organization that prepared it. 
Prepared under Contract No. NA'S 9-1461 by 
TEXAS INSTITUTE FOR REHABILITATION AND RESEARCH 
Houston, Texas 
for 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
For sale by the Office of Technical Services, Department of Commerce, 
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THE EFFECT OF BEDREST O N  VARIOUS 
PARAMETERS OF PHYSIOLOGICAL FUNCTION 
PART Ill. BIOINSTRUMENTATION 
By F. B. Vogt, M.D., R. J.  Lamonte, J .  R. McConnell, T. 0. Hallen, 
C .  VaIIbona, M.D., D. Cardus, M.D., W. A .  Spencer, M.D., and T. W. Holt 
ABSTRACT 
,304'7 
A bioinstrumentation system for collecting and recording multiple 
cardiovascular measurements was developed for use in tilt-table tests and for 
bedside monitoring during bedrest studies. Each component unit of the system 
i s  discussed in  this paper. 
i i i  
FOREWORD 
This study i s  a part of a NASA investigation of the effect of bedrest 
on various parameters of physiological function. It was sponsored by NASA 
Manned Spacecraft Center under Contract NAS-9-1461 , with Dr . Lawrence 
F. Dietlein, Chief, Space Medicine Branch serving as Technical Monitor. 
This study was conducted i n  the Immobilization Study Unit of the 
Texas Institute for Rehabilitation and Research, the Texas Medical Center. 
The authors are affiliated with Baylor University College of Medicine as 
follows: Dr. Vogt, Department of Rehabilitation; Mr .  McConnell, Depart- 
ment of Medicine; Mr .  Hallen, Department of Rehabilitation; Dr. VaIIbona, 
Departments of Rehabilitation, Physiology, and Pediatrics; Dr . Cardus, 
Departments of Rehabilitation and Physiology; and Dr. Spencer, Department 
of Rehabilitation. Mr .  Lamonte and Mr. Holt are affiliated with the Bio- 
instrumentation Section - Space Medicine Branch of the Manned Spacecraft 
Center. 
The authors wish to acknowledge the assistance of Mrs. Carolyn 
Caldwell in  the typing of this report. 
V 
THE EFFECT OF BEDREST ON VARIOUS 
PARAMETERS OF PHYSIOLOGICAL FUNCTION 
PART 1 1 1 .  BIOINSTRUMENTATION 
By F. B .  Vogt, M.D., R. J. Lamonte, J. R .  McConnell, T.  0. Hallen, 
C . Val Ibona, M .D., D. Cardus, M .D., W. A.  Spencer, M .D., and T.  W.  Holt 
SUMMARY 
This paper describes a bioinstrumentation system developed and bui l t  i n  
the Bioinstrumentation Section - Space Medicine Branch of the Manned Space- 
craft Center for use i n  bedrest studies conducted at the Texas Institute for Re- 
habilitation and Research under Contract NAS-9-1461. The system i s  bui l t  
primarily from commercially available component units to provide a recording 
and display capability for multiple physiological measurements. Included i s  a 
general discussion of the variety of sensor inputs available to the system, the 
signal processing and display of data for monitoring as the data are collected, 
and the means of coding and storing data on magnetic tape. 
INTRODUCTION 
The bioinstrumentation system described in  this paper was bui l t  to meet 
physiological data collection requirements i n  studies designed primarily to mea- 
sure cardiovascular deconditioning of bedrest immobilization. It was required that 
there be processing units for a multitude of sensor inputs, and that measurements 
be made from either a central study area where t i l t tests were performed, or the 
bedside of an individual subject during the period of recumbency. A moveable 
signal conditioner unit was bui l t  which could be rolled to the test area, either 
the bedside or tilt-table, and connected by wire to a central monitoring console 
at which the recording equipment was located. 
DESCRIPTION OF APPARATUS 
A block diagram of the component units of the bioinstrumentation system 
i s  shown in  Figure 1 .  The output of each sensor or detecting unit i s  connected to 
a signal conditioner to provide signal amplification or detecting capability. A 
single channel oscilloscope can be connected to the output of each signal condi- 
tioner to allow monitoring of the signal as i t  i s  collected at the test area. These 
SENSORS -b 
I I  
SIGNAL OSCILLOSCOPE 
CONDITIONERS MONITORING 
I 
OSCILLOSCOPE I DISPLAY I STRIP CHART 1 RECORDER 
MAGNETIC ANALOG 
TAPECODER PANEL PREPROCESSING 
Ar.  
.I 
MAGNETIC 
TAPE 
RECORDER 
I 2 
Figure 1. - Block diagram of component 
units of bioinstrumentation system. 
units are assembled i n  a moveable rack which i s  connected by wire to a central 
monitoring console. 
for routing signal f low and for programming a l l  control logic and signal proces- 
sing to and from the tape recorder. This patch panel i s  used also to route signals 
to the oscilloscope, to the stripchart recorder, and to and from special proces- 
sing circuits such as bandpass filters or cardiotachometer units. A magnetic tape 
coder provides a means to identify the data collected on magnetic tape or the 
strip- chart recorder. 
A patch panel matrix located i n  the central monitoring console i s  used 
Sensors 
A variety of sensors or detecting units were available for use with the 
system. A brief description of each sensor i s  presented to indicate its use i n  this 
particular experiment. Figure 2 shows a collection of these sensor units. 
Intra-arterial blood pressure. The unit A i n  Figure 2 shows a Statham*, 
Type P-23-Gb, pressure transducer which i s  connected to the artery by a fluid- 
f i l led, flexible, No. 8 cardiac catheter, B, which i s  terminated i n  a No. 20 dis- 
posable needle, c .  The transducer i s  used with a Sanborn** Carrier Preamplifier, 
Mode I 350- 1 1 00. 
Skin electrodes. The electrocardiogram and impedance pneumogram are 
detected by means of skin electrodes attached to the skin with an adhesive of 
either Eastman*** 9-10 glue or double-backed colostomy tape. The electrodes 
used for this study are of the NASA type1 and are shown a t  E in  Figure 2. They 
are stainless steel wire mesh electrodes of approximately 5/8 inch diameter and 
are connected to the signal conditioner unit by a coaxial type single-shielded 
wire with the shield grounded. 
Indirect blood pressure. Indirect blood pressure i s  obtained by a cuff- 
microphone techniqueL, shown at  F and I i n  Figure 2, by using an E & M Com- 
pany**** cuff and inflator system which provides automatic cycling of the cuff . .  
every 30 seconds. 
Carotid pulse. The carotid pulse contour i s  detected by means of a crys- 
tal pickup located i n  a plastic cup, K, as shown in  Figure 2. The unit i s  placed 
on the skin over the carotid artery and held in place by a spring-loaded attach- 
ment, J, which f i t s  around the neck. 
* Statham Instruments, Inc .; Los Angeles, California 
**  Sanborn Company; Waltham, Massachusetts 
Eastman Kodak Company; Rochester, New York 
E & M Instrument Company; Houston, Texas 
*** 
**** 
3 

Radial pulse. The radial pulse contour i s  detected by an E & M Com- 
pany* crystal pickup mounted on a firm board and covered by an elastic cloth 
as shown at  L in  Figure 2 .  The unit i s  placed on the skin over the radial artery 
and held i n  place by an elastic wrist band. 
Vibrocardiogram . The precordial vibrations corresponding to the vibro- 
cardiogram are detected by a Ling - Temco - Vought** capacitance microphone 
operated by a carrier system. The microphone i s  shown at D in  Figure 2.  
Phonocardiogram. The precordial vibrations corresponding to the phono- 
cardiogram are detected by a crystal type microphone of the type shown at  H of 
Figure 2 .  
Mobile Unit 
The mobile unit contains the signal conditioners, amplifiers, detecting 
units, and accessory equipment which can be rolled to the bedside or to the 
tilt area. Figure 3 shows the unit at the bedside of an experimental subject. 
Electrocardiogram preamplifier. A Gulf Aerospace Amplifier**: Model 
702, amplifies the ECG signal level to approximately 1 .5 volts output for trans- 
mission to the central monitoring console. The frequency response of the ampli- 
f ier i s  from 0.5 to 100 cycles per second. 
Impedance pneumograph. Respiration i s  detected by using an E & M 
Company* impedance pneumograph3 connected to an E & M Company* DC amp- 
l i f ier  which i s  used to drive the magnetic tape recorder. 
Central Monitoring Console 
The central monitoring console provides for signal routing, signal proces- 
sing, magnetic tape recording, signal monitoring on an oscilloscope, and signal 
monitoring on a direct recorder. The console i s  shown i n  Figure 4. 
Oscilloscope. An 8 channel Sanborn****, Model 769, oscilloscope 
i s  used for simultaneous display of multiple signals. The device can be connected 
to either the input or output of the tape recorder. The oscilloscope provides a con- 
venient means of monitoring signals while sensors are placed correctly to assure col- 
lection of good quality recordings. 
* 
**  
*** 
**** 
E & M instrument Company; Houston, Texas 
Ling-Temco-Vought, Inc .; 10s Angeles, California 
Gulf  Aerospace Corporation; Houston, Texas 
Sanborn Company; WaI tham, Massachusetts 
5 
p....*.**. 
....(I..... - _  
Figure 3 .  - Portable unit containing signal conhitioner s. 
6 
Figure 4. - Central  monitoring console for bioinstrumentation system. 
7 
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Magnetic tape recorder. Two 7 channel Precision Instruments", Model 
PS-200, tape recorders were used i n  the earlier part of studies at the Texas Institute 
for Rehabilitation and Research. Later, a single 14 channel P I  200 magnetic tape 
recorder provided for simultaneous recording of the multiple channels of data col- 
lected. The units were operated i n  the FM mode at a speed of 1 7/8 inches per 
second to provide a frequency response from 0 to 312 cycles per second. 
Magnetic tape coder. A Cutler-Hammer, Airborne Instruments Laboratory**, 
Model 483, coder unit provides a signal code with a 12 b i t  binary code generated 
a t  a slow speed for display on the strip chart recorder and for recording on an FM 
channel of the tape recorder. A log of experimental events i s  kept to correlate 
with the code signals which are provided either automatically at a preset time inter- 
val, or manually for special events. 
Bandpass f i l ter .  A Krohn-Hite***, Model 330-AR, bandpass f i l ter  could 
be inserted into any desired part of the system to provide bandpass fi l tering in  the 
frequency range of 0.02 to 2000 cycles per second. 
an RC decay curve whose amplitude represents approximately a linear relation to 
the R-R interval of the electrocardiogram; the longer the R-R interval, the greater 
the amplitude of the ramp voltage. A beat-by-beat indicator of the preceding 
R-R interval i s  thus provided in  an analog form. 
S tri p- chart recorder. A Consol ida ted E I ectrodynam i cs Corpora ti on* * ** * 
optical galvanometer type recorder system i s  attached to the central monitoring 
console for playback of data. Galvanometers with an upper frequency response 
of 2000 cycles per second are available i n  this unit. A physiographd system****and 
an Offner****** , Model Type S, Dynograph, pen recorder system are used also for 
monitoring and playback of data. 
Cardiotachometer. An E & M Company**** cardiotachometer provides 
RESULTS 
back on a strip chart recorder i s  shown i n  Figures 5 and 6. Figure 5 shows a simul- 
taneous display of the electrocardiogram, the phonocardiogram, the carotid pulse 
tracing and the radial pulse tracing at  a paper speed of 50 mm. per second to allow 
clear identif ication of the components of each measurement and their temporal re- 
lationships. Figure 6 shows a recording of some of the measurements obtained during 
a t i l t test. A slow speed writeout i s  used to show the trend of changes i n  the mea- 
surements for the 5 minute period of the record. 
A sample of the type of data collected, amplified, recorded, and played 
* Precision Instruments; San Carlos, California 
* *  Cutler-Hammer, Airborne Instruments Division; Long Island, N .Y. 
*** Krohn-Hite Corporation; Cambridge, Massachusetts 
E & M Instrument Company; Houston, Texas **** 
***** Consol ida ted El  e ctrodynam i cs Corporation; Pasadena, Ca I i f  ornia 
****** Beckman Instruments, Inc., Offner Division; Shi l ler Park, II linois 
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REFERENCES 
1 .  Day, J.L., and Lippitt, M.E.: A Long Term Electrode System Suitable for ECG 
and Impedance Pneumography. NASA Memorandum, 1963. Unpublished 
report. 
2. Geddes, L.A., Spencer, W.A., and Hoff, H.E.: Graphic Recording of the Korot- 
koff Sounds. American Heart Journal 57:370, 1959. - 
3. Geddes, L.A. , Hoff, H .E. , Hickman, D .M., and Moore, A.G.: The Impedance 
Pneumograph. Aerospace Medicine 33:28,1962. - 
4 .  Hoff, H.E., Geddes, L.A., ahd Spencer, W.A.: The Physiograph, An Instrument 
i n  Teaching Physiology. Journal of Medical Education 32: 181,1957. - 
5 .  Geddes, L.A., Partridge, M., and Hoff, H.E.: An EKG Lead for Exercising 
Subjects. Journal of Applied Physiology - 15:311 , 1960. 
NASA-Langley, 1965 CR-173 11 


The effect of bed rest on various parameters of physiological function.  part iii- bioinstrumentation

The effect of bed rest on various parameters of physiological function. part iii- bioinstrumentation

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