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

TY - JOUR

T1 - Tidal changes in PaO2 and their relationship to cyclical lung recruitment/derecruitment in a porcine lung injury model

AU - Crockett, D C

AU - Cronin, J. N.

AU - Bommakanti, N.

AU - Chen, R.

AU - Hahn, C. E. W.

AU - Hedenstierna, G.

AU - Larsson, A.

AU - Farmery, A.

AU - Formenti, F.

PY - 2019/2

Y1 - 2019/2

N2 - 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.

AB - 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.

KW - diagnostic imaging

KW - dynamic computed tomorgraphy

KW - lung injury

KW - pulmonary atelectasis

KW - respiration

KW - ventilation

UR - http://www.scopus.com/inward/record.url?scp=85055910846&partnerID=8YFLogxK

U2 - 10.1016/j.bja.2018.09.011

DO - 10.1016/j.bja.2018.09.011

M3 - Article

SN - 0007-0912

VL - 122

SP - 277

EP - 285

JO - British Journal of Anaesthesia

JF - British Journal of Anaesthesia

IS - 2

ER -