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Airway Closure and Distribution of Inspired Gas in the Extremely Obese, Breathing Spontaneously and During Anaesthesia with Intermittent Positive Pressure Ventilation
Author(s) -
Hedenstierna GöraN,
Santesson Joakim,
Norlander Olof
Publication year - 1976
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.1399-6576.1976.tb05047.x
Subject(s) - medicine , nitrogen washout , anesthesia , ventilation (architecture) , airway , general anaesthesia , tidal volume , functional residual capacity , lung volumes , respiratory minute volume , respiratory system , lung , mechanical engineering , engineering
Airway closure (closing capacity, CC), FRC, total efficiency of ventilation (lung clearance index, LCI) and distribution of inspired gas (nitrogen washout delay percentage, NWOD) were determined by nitrogen washout techniques and arterial Po 2 and Pco 2 measured by standard electrodes in 10 extremely obese subjects, prior to and during anaesthesia and artificial ventilation. CC was normal, but because of small FRC, airway closure occurred within a tidal breath in 9 out of 10 subjects during spontaneous breathing, when awake. Po 2 was reduced, the hypoxaemia correlating to the magnitude of airway closure. LCI was normal, but NWOD was borderline. During anaesthesia, CC was unaltered but FRC was further reduced, so that in nine subjects airway closure occurred above FRC and tidal volume together. A marked increase in relative hypoxaemia was recorded. LCI and NWOD rose, indicating less efficient and less even ventilation. It is concluded that airway closure reasonably explains the marked hypoxaemia in obese subjects during anaesthesia, and that it may also be the reason for the uneven distribution of inspired gas.