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Ventilation‐Perfusion Distribution During Inhalation Anaesthesia
Author(s) -
Bindslev L.,
Hedenstierna G.,
Santesson J.,
Gottlieb I.,
Carvallhas A.
Publication year - 1981
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1981.tb01667.x
Subject(s) - medicine , shunt (medical) , anesthesia , supine position , ventilation (architecture) , airway , positive end expiratory pressure , perfusion , mechanical ventilation , cardiology , mechanical engineering , engineering
Ventilation‐perfusion (V̇ a /Q̇) ratios were studied by means of an inert gas elimination technique in healthy subjects with an average age of 51 years in the supine posture (a) when awake, (b) during inhalational anaesthesia, spontaneously breathing, (c) during mechanical ventilation, and (d) when a positive end‐expiratory pressure (PEEP) was applied. In the awake subject a bimodal distribution of V̇ A /Q̇ was recovered in most patients, one mode centered around the ratio of 1 and another, smaller mode, within low V̇ A /Q̇‐regions. Any shunt was less than 3% of cardiac output. With anaesthesia and spontaneous breathing, the low V̇ A /Q̇ mode was reduced and the shunt increased to an average of 6.2%. With mechanical ventilation, the major V̇ A /Q̇ mode was widened while the shunt was further increased in 4 of 10 subjects (mean 8.6%). With PEEP, the shunt was reduced and a new mode within high V̇ A /Q̇‐regions appeared. The shunt and low V̇ A /Q̇‐regions may be explained in terms of airway closure while the high V̇ A /Q̇ mode with PEEP may be attributed to the development of a zone I.