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CHANGES IN CAPACITY OF THE LEG VEINS STUDIED BY A SIMPLE COUNTER‐PRESSURE TECHNIQUE
Author(s) -
Shephard R. J.
Publication year - 1961
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1961.sp001531
Subject(s) - spirometer , blood volume , blood pressure , medicine , anesthesia , body position , venous return curve , central venous pressure , volume (thermodynamics) , displacement (psychology) , cardiology , heart rate , hemodynamics , physical medicine and rehabilitation , airway , exhaled nitric oxide , psychology , physics , quantum mechanics , bronchoconstriction , psychotherapist
The effective transmural pressure in the leg veins may be reduced to zero by appropriate inflation of an anti‐g suit applied to the legs only. The central displacement of venous blood consequent upon suit inflation causes consistent physiological changes, particularly an expiratory shift of the end‐tidal position recorded by a spirometer. The end‐tidal shift is proportional to the expected displacement of blood, and is modified by both the initial venous pressure (varying body posture) and the initial venous tone (varying room temperature and use of pressor amines). It may thus be used as a simple index of the pressure/volume state of the leg veins before and after administration of pharmacological agents. Inflation of the anti‐g suit also produces an increase of respiratory rate and minute volume, but tidal volume is unchanged. Vital capacity is reduced, both inspiratory and expiratory capacity being affected. Pulse rate and pulmonary compliance are also reduced. Each of these changes may be interpreted in terms of central displacement of blood.