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Isocapnic high frequency jet ventilation: dead space depends on frequency, inspiratory time and entrainment
Author(s) -
Fletcher R.,
Malmkvist G.,
Lührs C.,
Mori N.,
Drefeldt B.,
Brauer K.,
Jonsson B.
Publication year - 1991
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.1399-6576.1991.tb03264.x
Subject(s) - tidal volume , jet ventilation , entrainment (biomusicology) , dead space , ventilation (architecture) , medicine , jet (fluid) , respiratory minute volume , anesthesia , mechanics , respiratory system , mechanical ventilation , meteorology , physics , airway , rhythm
Twelve healthy pigs were ventilated with high frequency jet ventilation via a Mallincrodt HiLo jet tube. The expired gas was led to a conventional ventilator and CO 2 analyzer which were used to measure CO 2 climination. There was no bias flow, so that the jet entrained only expired gas, i.e. rebreathing occurred. Frequency was varied between 2 and 11 Hz and the duration of inspiration, as a fraction of the ventilatory cycle (Ti/Ttot), from 5 to 20%. The minute ventilation, Vjet, delivered by the jet ventilator was adjusted to maintain a constant Paco 2 . At 2 Hz and a Ti/Ttot of 5%, Vjet was of the same magnitude as ventilation during conventional intermittent positive pressure ventilation, and the total dead space fraction, V D /V T was 0.32. Both increasing frequency at a constant Ti/Ttot, and increasing Ti/Ttot at a constant frequency, increased V D /V T which was maximal (0.8) at 11 Hz and a Ti/Ttot of 20%. When entrainment was blocked, tidal jet volume had to be greatly increased. The continuous measurement of CO 2 climination was found to be useful for maintaining isocapnia when the jet ventilator setting was changed.