To monitor breaths per minute, two rate-to-analog converters are alternately used to read and count the respiratory rate from an impedance pneumograph sequentially displayed numerically on electroluminescent matrices

Graham, O.

English

NASA Technical Reports Server

No. 2	 Pifferentiator 
Mono$table	 Reset 
Multivibrator	 Generator
Respiration Pulse In
Pulse Shaper 
(Schmitt Trigger)
November 1964
	
Brief 64-10259 
NASA TECH BRIEF 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint 
industry with the technical content of an innovation derived from the space program. 
Pneumotachometer Counts Respiration Rate of Human Subject 
Electroluminescent 
Numerical Display Matrices 
Monostable Multivibrator
Differentiator	 Reset Generator 
Jifferentiato ThYTTT 
Respiration Phase 
Monostable No. 1 
Pulse	 1	 (P1) 
Pulse 2 (P2) 
Pulse 3 (P3) 
1-cps Clack	 - 
Monostable No. 
211___ 
'uww .1wm fl'fl$Afl_
J1_ Square Pulse 
Holds Gate Closed, 
No Clock Pulses Pass 
Clock Pulses—*. 
WAVEFORMS 1 -cps Multivibrator
Driver	 P 
Morage
Neon
 
P1 gister 2	
Switching Matrices 
t.._ 	 Flip-Flop 
Reset 
LP2	
Diode Logic 
ngPu Ise AN 7 
Reset 
LP3 Pulse	
1 2 4 8 1	 Flip Flop Counter 
-	
Count Register AND Gate Normally Open. 
Counts Pass 
The problem: To monitor respiration rates, in 
breaths per minute, on a breath-to-breath basis. 
The solution: Two rate-to-analog converters are 
alternately used to read and to count respiration 
pulses from a body sensor (an impedance pneumo-
graph) over fixed intervals of time; the converter 
outputs are sequentially displayed numerically on 
electroluminescent matrices. 
How it's done: The respiration waveform from the 
body sensor is fed into the pulse shaper (Schmitt 
trigger), which provides an output that sets the two 
control monostable multivibrators to the ON condi-
tion. The ON time for multivibrator No. 1 is less
than the ON time for multivibrator No. 2. The differ-
ence in ON time between the two multivibrators 
allows the two square-wave outputs to be differen-
tiated to create three sequential timing pulses. Pulse 
I resets storage register No. 1, pulse 2 gates informa-
tion from the count register into this storage register, 
and pulse 3 resets the count register. The ON time of 
multivibrator No. 2 inhibits the dual input AND gate. 
The 1-cps clock pulses are only allowed into the count 
register in the time between respiration pulses, which is 
the OFF time of multivibrator No. 2, and are counted 
by the count register in this OFF time. During the 
gating-pulse time, the binary number in the count 
register, which represents the time in seconds between 
(continued overkal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document. 
https://ntrs.nasa.gov/search.jsp?R=19640000070 2020-03-11T17:05:29+00:00Z
breaths, is steered by the AND-OR logic into the 
storage registers. 
The AND-OR logic circuitry essentially divides the 
count-register binary number (time between breaths) 
into 60, and the resulting quotient (breaths per 
minute) is routed to the proper storage register. The 
AND-OR logic is complicated by the fact that the 
photoconductive matrices require a 1-24-8 binary-
coded input to drive the electroluminescent displays; 
hence, a separate storage register must be used to 
address each matrix properly. 
The AND logic circuitry decodes the four-bit-count 
register number into one of 15 "hot" lines, and the 
OR logic circuitry routes the activated line into 
each storage register as a 1-2-4-8 binary code. The 
OR logic circuitry sets the binary 6-3-2-1-0 code into 
storage register No. 1. The OR logic is also capable 
of setting one of the binaries for 0 through 9 into 
storage register No. 2. The activated "hot" line 
determines which binary is set into each storage 
register. The digital rate meter has the capability of 
driving the electroluminescent matrices to display 
numbers 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 30, and 60.
The intervening numbers in this range could be 
achieved by increasing the clock frequency, increasing 
the count-register capabilities, and by increasing the 
complexity of the AND-OR steering logic. The accu-
racy of the digital meter is a direct function of the 
clock frequency. 
Notes: 
1. Although primarily developed for space-medicine 
research, this digital rate meter may have appli-
cation as a clinical diagnostic aid or as a teaching 
aid for medical students. 
2. Inquiries concerning this innovation may be 
directed to: 
Technology Utilization Officer 
Manned Spacecraft Center 
P.O. Box 1537 
Houston, Texas, 77001 
Reference: B64-10259 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: Olin Graham 
(MSC-92) 
Brief 64-10259	 Category No. 01


Pneumotachometer counts respiration rate of human subject

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