Telemetry monitored physiological data of human circadian cycles during prolonged isolatio

Clagg, B. R.

Schaefer, K. E.

English

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https://ntrs.nasa.gov/search.jsp?R=19680009668 2020-03-12T09:29:58+00:00Z
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INTRODUCTION 
recan% yews t;eleme-t;ry systems have been @x-bwimly used in  
Cassdiovaseulw data mm monitorad during F400 dicine. 
heart; rate and reapiration reapoxme p 
Sirnorm and Prathw (3) daacribed an 
which took into aw0un-t the -t;rg. SY 
axdLydfB%b3d* 
, 
referencrE3d t o  a constant pmsaure sourchj, p roviad  a set-point signal 
t o  the confxolling inslzument, 
inches of m c u r y  within a &xnda,rd bv ia t ion  of' *004 inches, 
chamber was continuously ventilated w i t h  100 literslmin provided by a 
lubricanbfme air pump, Humidity m a  h p t  at 30 per cent + 5 per cent 
by a pmumaticaJ$Ly controlled chemical drier. 
30-foot c 
t o  about &foot c m U s *  C m i c a t i o n  through the chamber was b 
-way audio out of the chamber, 2) audio c o b  into th chanib 
The chamber pr%smre was held at 30,560 
Thte 
~ l u n i n a t i o n % s  aet at  
s during the subjmts' day and during l$m night redwed 
medical-lock written me 
PhysiologicaJ. Data Acquisitionr 
ject$ 
wm), 3) basal skin resistance (palm), 4) EEG (occipital), 5) respi- 
ration, wad 6) EKG. The subjects wore an FWFM type telemetry vest 
(Biometrics) The raw data were received a t  a csntraJ, location out- 
side the chamber f o r  preliminary reduction and recordingr !Cha core 
and amface temperatures and 'che basal. skin ralsistances were direct 
analogue s igmla  which passed through l o w  paas f i l t e r s  before baing 
converted t o  digi ta l  fomn and recorded on standard IBM cards once 
&very ndnute, These low pass f i l t e r s  (ha2i power frequency, 6(10)'3 
cpa * )  were necessary t o  minimize t'a,liasLngtt problems during subsem 
0uen.l; sspeeWa2 analyses. EKG and respiratory sign8J.s were converted 
t o  minuteaatera rznd recorded d i g i t d l y  on cards once a minute, and 
monitored graphically every 15 minutes f o r  a duration af two minutes. 
EECI slgrmLs were a.lao gaph2caU.y monitored every 15 minuties. More- 
aver, baselbe croaeinga (inctica-bAon o f  prominen% BEG frequency) and 
averaged a t rp l l tud~ were ~ g ~ ~ ~ l y  recarded awry inhutera Figure 1 
Bhma a b l ~ k  diagram of .t;l;zes t o t a l  tslsrne.t;zy ayatem which conaisted 
o f  ~ W C I  e i g h % - c h a . l  systems ( B l ~ ~ W l c a )  
untts wsm 'by 
The following variables were continuously monitored on each sub- 
1) core temperature ( r e c t a ) ,  2) surface temperature (upper 
BWISQX a d  t r t ~ m l t t ~  
2nwVm.a BubJects w e  a i ~ p i ~ ~ e l .  i n  P I ~ U T ~  2, 
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part  used was isotonic and less prone t o  cause skin i r r i ta t ion,  
These electrodes lasted up t o  s ix  or seven days, depending on the 
application, 
somewhat shorter since the very l o w  potentials were af 
by the slowly charging resistance of the electrodes, This deterio- 
ration prompted us t o  implant si lver wires in  subseqwnt experiments 
and we found them t o  last 10-12 days, The limitation of the silver 
or platinum wire method l i e s  i n  the eventual t issue rejectionl 
In the case of EEG electrodes, the useful time was 
e P 
t 
Leads t 
The second problem of the telemetry system consists of fatiguing 
and breaking of electrode wires, particularly of those electrodes 
whose connections are exposed t o  constant movement (EKG, BSR, palm 
electrodes)* 
wire, furnishedby Cyanamid, This wire consists of 40 strands of 
extremely fine vir@, capper Wire, sufficient t o  m a k e  the gauge a 
standard 22, 
For t h i s  reason, we obtained special fatigue resistant 
Long term continuous use of telemetry equipment presents the 
obvious problem of obtaining routine calibrations, A decision must 
be made whether, at some point, it is suitable t o  interrupt the ex- 
periment i n  order t o  carry out recalibrations, 
Signal Conditioner: 
The type of data analysis determines what kinds of analog signal 
conditioning is t o  be done t o  the telemetry data, 
was desired f r o m  the EKG signals and the respiratory signals, 
ra te  information was obtained by counting both EKG, BSR complexes 
and the nmber of inspiration signals during one minute and recording 
%his information, 
inent EEG frequency, 
t h e  number of EEG baseline crossings i n  one minute. 
the EEG signal was obtained by integration of the signal for one 
minute* 
sistance were recorded essentially unmodifTed, The sampling theory 
of data analysis requiredthat  frequencies which were greater than 
half the sampling interval be attenuated, For th i s  purpose, special 
l o w  pass f i l ters  have been used having a time constant of three min- 
utes, 
worked out very well. 
Rate information 
T h i s  
It was desired t o  obtain an estimate of the prom- 
The most expedient method w a s  simply t o  count 
The average of 
Surface temperature, core temperature and basal skin re- 
The signal Conditioning equipment was developed locally and 
Data Transmission Equipment: 
The output of the signal conditioning equipment was multiplexed 
and converted t o  a digi ta l  format f o r  punching w i t h  a standard IEM 
cwd punch, The analog digi ta l  converter was furnished by Gulton In- 
&mtriea, Inc* The card punch was the weakerst link i n  th@ data re- 
cording @bystem. Reliable card punching represents a major prob~em 
for continuous long-duration experimentse 
curacy of the card punched data, measurements were graghically re- 
corded every fifterefn minutes f o r  a period of one minute w i t h  an Offner 
dynograph, Under o w  conditionla, the use of the punch-oard syrjternms 
neoessary because the existing computer facilities had only punch-card 
input* Otherwise, it would have bmn more feaeibLe t o  ue? punched 
paper tape, or  magnetic tag@* 
In order t o  verify the ac- 
5 
Corrections ,of, Artifacts ,in Telemetere,d patat 
Several coqputer programs were developed t o  locate and correct 
many of th@ae errorsa One program oorrected mechanical carbpunching 
emor i j  such as false column r@gieatration, card order, e tcw A second 
correction program detected errors i n  telemetry signal, e*g'l loss  of 
signals or  loss of electrode Qontact, 
ditiona, 1) they had t o  be within a rsaaonable physiological range, 
and 2) the data could not display unphysio1ogicaLl.y fast changes, 
Certain types of error& could be corrected by a l inear approximationn 
me data had t o  meet two con- 
oted data and t i m e  information were placed i n  standard binary- 
Subjects: 
Extended experiments of t h i s  t y p  put great demands on the sub- 
jects, They must be highly motivated, intell igent and thoroughly ac- 
d with the elcperimental plan and, furthermore, must be able t o  
O w  
students who gmticipa%e& i n  the Navyts 
t r y  ~ u u i ~ n t  during the e x g e r h n t ,  
searah gersannel a 
t 
RESULTS AND DISCUSSION 
a 
In  the following, a few examples are given showing acquisition 
and analyses of telemetry data  from subjects who were confined f o r  
long periods e 
Figure 3 exhibi ts  the telemetered core t e q e r a t u r e  data of two 
subjects, Following isolat ion i n  a constant environment, the sleep- 
wakefulness cycle s h i f t s  regularly about 1-2 hours per day, as indi- 
cated i n  the s h i f t  of the black bars denoting the sleep period, The 
circadian cycles of body temperature s h i f t  correspondingly. Under 
these conditions, i n  which the subjects retained the i r  normal pattern 
of physical ac t iv i ty  i n  isolation, all of the measured circadian cycles 
of physiological functions were  synchronized w i t h  the sleep-wakefulness 
cycle. 
Figure 4 exhibi ts  the results of a three-day overlapping auto- 
correlation analysis of respiratory rate i n  a subject confined f o r  
1 2  days i n  a constant environment, It can be seen tha t  the 24-hour 
component (within the low frequency band 18-48 hours) of the spectrum 
analysis decreases during the first days of isolat ion while the 5-7 
hour frequencies increase. 
t i on  produces a marked change i n  the temporal order of frequencies 
underlying the cycles of physiological functions, 
This indicates t ha t  the stress of isola- 
Figure 5 gives an example of cross-correlation analysis of body 
temperature from one subject with a synthesized 24-hour periodicity 
of known amplitude and phase. The body temperature did not follow 
the phase s h i f t  of the sleep-wakefulness cycle indicating a desyn- 
chronization of physiological functions, 
i n  contrast  t o  those shown i n  Figure 3, w e r e  obtained i n  a subject 
whose physical ac t iv i ty  was greatly reduced during isolat ion in  a 
constant environment, 
dinating influence on the cycles of physiological functions. 
These findings, which me 
It appears t h a t  physical ac t iv i ty  has a coor- 
BODY TEMPERATURE O C  
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DEGREES PHASE SHIFT (15'= I HOUR 1 
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REFEEEXCES 
1, Roman, J.A, , Cardiorespiratory Funotioning in-Flight, - Med,, 23322-337, April 1963* 
cal Monitoring Act ivi t ies  and Report on Studies M a d e  on F-125 
PilotB, Aeroapaae MBd, - 35~23-27, 1964rr 
Simons, D,G, and Prather, W,, A Personalized Radio T ~ h w . t r Y  Sys- 
t e m  f o r  Monitoring Centra Mervous Systerm Arousal, in hrospace  
f ibr ight ,  G,A, and Axehod, IL, A Review of Biomedi- 
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Flight, 
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4* Catterson, A,D,, McCutcheon, E,P,, Minnersr H,A, and Pollard, R,A,, 
Aeromedicd Observations, Pg 294-326 i n  Resdts of the Fourth 
Uni-d S ta t e s  Manned Orbital. Flight, NASA, SP-45, 1963+ 
Agadzhanyan, N, a d  Koulinickw, Io# Comic Biotelemetry, Tekhnika 
MoLodezhi, 9x25-26, 1962, English Wandation: Foreign Technol- 
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5, 
6, Wheelmight, Charles Bar Physiological, Sensors f o r  U s e  i n  Project 
Mercury, NASA, TND-1082 e Manned Spacecraft Center, Houston, 
T~XBS, 1962, 


Studies of circadian cycles in human subjects during prolonged isolation in a constant environment using eight-channel telemetry systems

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