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Tidal changes in PaO2 and their relationship to cyclical lung recruitment/derecruitment in a porcine lung injury model

Research output: Contribution to journalArticle

D C Crockett, J. N. Cronin, N. Bommakanti, R. Chen, C. E. W. Hahn, G. Hedenstierna, A. Larsson, A. Farmery, F. Formenti

Original languageEnglish
Pages (from-to)277-285
Number of pages9
JournalBritish Journal of Anaesthesia
Volume122
Issue number2
Early online date3 Nov 2018
DOIs
Publication statusPublished - Feb 2019

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Abstract

Background: Tidal recruitment/derecruitment (R/D) of collapsed regions in lung injury has been presumed to cause respiratory oscillations in the partial pressure of arterial oxygen (PaO 2 ). These phenomena have not yet been studied simultaneously. We examined the relationship between R/D and PaO 2 oscillations by contemporaneous measurement of lung-density changes and PaO 2 . Methods: Five anaesthetised pigs were studied after surfactant depletion via a saline-lavage model of R/D. The animals were ventilated with a mean fraction of inspired O 2 (FiO 2 ) of 0.7 and a tidal volume of 10 ml kg −1 . Protocolised changes in pressure- and volume-controlled modes, inspiratory:expiratory ratio (I:E), and three types of breath-hold manoeuvres were undertaken. Lung collapse and PaO 2 were recorded using dynamic computed tomography (dCT) and a rapid PaO 2 sensor. Results: During tidal ventilation, the expiratory lung collapse increased when I:E <1 [mean (standard deviation) lung collapse=15.7 (8.7)%; P<0.05], but the amplitude of respiratory PaO 2 oscillations [2.2 (0.8) kPa] did not change during the respiratory cycle. The expected relationship between respiratory PaO 2 oscillation amplitude and R/D was therefore not clear. Lung collapse increased during breath-hold manoeuvres at end-expiration and end-inspiration (14% vs 0.9–2.1%; P<0.0001). The mean change in PaO 2 from beginning to end of breath-hold manoeuvres was significantly different with each type of breath-hold manoeuvre (P<0.0001). Conclusions: This study in a porcine model of collapse-prone lungs did not demonstrate the expected association between PaO 2 oscillation amplitude and the degree of recruitment/derecruitment. The results suggest that changes in pulmonary ventilation are not the sole determinant of changes in PaO 2 during mechanical ventilation in lung injury.

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