WHOLE BODY MEASUREMENT SYSTEMS

• US 3,769,834 A
• Filed: 11/18/1971
• Issued: 11/06/1973
• Est. Priority Date: 11/18/1971
• Status: Expired due to Term

• Current Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, John S. Ogle, N/a,
• Original Assignee: Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of, John S. Ogle, N/a,
• Inventors: Ogle, John S., Fletcher, James C. Administrator of the National Aeronautics and Space, N/a,
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US05/200,040
• Time in Patent Office: 719 Days
• Field of Search: 73/149,29B 128/2S,2.05
• US Class Current: 600/587
• CPC Class Codes: A61B 5/0806 by whole-body plethysmography measuring blood flow using plethysmography A61B5/0295; impedance plethysmography A61B5/053; measuring volume of the body or parts thereof A61B5/1073
• CPC Class Codes: A61B 5/1073 Measuring volume, e.g. of limbs
• CPC Class Codes: G01F 17/00 Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies measuring linear dimensions to determine volume G01B

Abstract

A system for measuring the volume and volume variations of a human body under zero gravity conditions is disclosed. An enclosed chamber having a defined volume and arranged for receiving a human body is provided with means for infrasonically varying the volume of the chamber. The changes in volume produce resultant changes in pressure, and under substantially isentropic conditions, an isentropic relationship permits a determination of gas volume which, in turn, when related to total chamber volume permits a determination of the body volume. By comparison techniques, volume changes of a human independent of gravity conditions can be determined.

Claims

1. A method of ascertaining the volume of a human body wherein a respiratory subject is located within a chamber having a defined volume comprising the steps of cyclically changing at a rate of 1 to 100 Hz the volume of a chamber containing a respiratory subject;

suppLying a gas to said respiratory subject;

while changing the volume of such chamber, measuring the pressure change in such chamber;

measuring the absolute pressure in said chamber; and

computing by machine operations the body volume of the respiratory subject by subtracting from the total volume of the enclosure the gas volume as determined from the equation ( Delta P/ Delta V) ( gamma Pg/Vg) where Delta P/ Delta V is the derivative change in pressure relative to volume, gamma is the ratio of specific heat at constant pressure to the specific heat at constant volume, Pg is the absolute pressure of the gas, and Vg is the volume of the gas.

2. The method as defined in claim 1 wherein the frequency of the changing of the volume is such that it has a short time period relative to the time period established for any leaks from the enclosure.

3. Apparatus for determining the volume of a human body comprising a substantially gas-tight enclosure containing a gas;

means for supplying air to a subject within said enclosure;

means for cyclically varying at a rate of 1 to 100 Hz the volume of said enclosure and for deriving an indication of the relative volume of said enclosure;

means for deriving indications of changes in pressure;

means for deriving an indication of the absolute pressure within said enclosure;

means responsive to the derivative change in indications of pressure relative to changes in volume of said enclosure, the ratio of specific heat at constant pressure to the specific heat at constant volume, and the ambient absolute pressure of the gas in said enclosure for deriving the volume of gas in said enclosure; and

means responsive to the derived value for the volume of gas in said enclosure for determining the volume of a subject in said enclosure.

4. The apparatus of claim 3 wherein said means for varying the volume of said enclosure includes a piston and cylinder system and said pressure deriving means comprises a low frequency response device.

5. The apparatus of claim 4 wherein said gas volume deriving means operates according to the relationship of ( Delta P/ Delta V) ( gamma P/V) where Delta P/ Delta V is the derivative change in indications of pressure relative to volume in said enclosure, gamma is the ratio of specific heat at constant pressure to the specific heat at constant volume, P is the ambient absolute pressure of the gas in said enclosure, and V is the gas volume in said enclosure.