Compact balanced-bellows dry type spirometer was designed to be insensitive to acceleration fields along any or all coordinate axes. It provides true indication of respiratory action of test subject without need for calibration in acceleration fields

Holden, G. G.

Smith, J. R., Jr.

English

NASA Technical Reports Server

.4	
September 1972
	 B72-10279 
.
NASA TECH BRIEF 
Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Balanced-Bellows Spirometer 
The spirometer is an apparatus used to measure 
total lung capacity, maximum breathing capacity, 
tidal volume, functional residual capacity, and oxygen 
uptake. Spirometers can be used to assess the effects 
of space travel (as well as high-altitude and high-
speed travel in the earth's atmosphere) on creatures 
which breathe air. Unfortunately, the acceleration 
forces which occur during takeoff, landing, and other 
maneuvers in test flights as well as the forces asso-
ciated with test centrifuges often interact with ordi-
nary laboratory spirometers; for example, spirometers 
which use water as a gas seal obviously can not per-
form properly in acceleration fields, and ordinary dry-
type spirometers are usually too large for use in test 
chambers. Since dry-type spirometers necessarily in-
clude an expandable and contractable chamber, an 
acceleration force along any axis tends to restrict 
chamber movement, but the dry-type spirometers can 
be used if the acceleration force is allowed to act 
along a neutral axis. 
A compact balanced-bellows dry-type spirometer 
has been designed to be insensitive to acceleration 
fields along any or all coordinate axes, thus, it pro-
vides a true indication of the respiratory action of the 
test subject without need for calibration in accelera-
tion fields. 
The active component of the improved spirometer 
consists of two equal-size'ua1-siz bellows mounted on oppo-
site sides of a metal wall; a passage through the metal 
wall permits them to perform as a single chamber. An 
air inlet is attached to one bellows and an outlet to 
the other. The bellows are pivotally connected to op-
posite edges of the metal wall; they are interconnected 
mechanically so that the tendency of one bellows to
move toward or away from the metal wall under the 
influence of acceleration forces is resisted by an equal 
and opposite tendency of the other. Consequently, 
the bellows are not affected by acceleration forces, 
and they are free to move in accordance with the 
force of the air pressure produced by the lungs of 
the test subject. 
The bellows are identical in shape, size, and con-
struction, and are made of 0.106-mm (0.004-inch) 
thick polyvinyl chloride-acetate film with corner rein-
forcements of 0.254-mm (0.010-inch) polyvinyl chlo-
ride film. Metal plates and screws, metal hinges and 
screws, and cements are used to secure the bellows to 
the intervening metal wall, and two "string" loops 
(any material other than an elastomeric type) are 
used to interconnect them.
(continued overleaf) 
	
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sive or exclusive license for its commercial develop-
ment should be addressed to:
. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B72-10279 
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,420,225). Inquiries concerning nonexclu-
NASA Patent Counsel 
Mail Code 200-1A 
Ames Research Center 
Moffett Field, California 94035 
Source: George C. Holden and

Joseph R. Smith, Jr.

Ames Research Center

(XAC-01547) 
B72-10279	 Category 05


Balanced-bellows spirometer

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