Abstract
IntroductionAcute lung injury (ALI) can result from various insults to the pulmonary tissue. Experimental and clinical data suggest that spontaneous breathing (SB) during pressure-controlled ventilation (PCV) in ALI results in better lung aeration and improved oxygenation. Our objective was to evaluate whether the addition of SB has different effects in two different models of ALI.MethodsForty-four pigs were randomly assigned to ALI resulting either from hydrochloric acid aspiration (HCl-ALI) or from increased intra-abdominal pressure plus intravenous oleic acid injections (OA-ALI) and were ventilated in PCV mode either with SB (PCV + SB) or without SB (PCV – SB). Cardiorespiratory variables were measured at baseline after induction of ALI and after 4 hours of treatment (PCV + SB or PCV – SB). Finally, density distributions and end-expiratory lung volume (EELV) were assessed by thoracic spiral computed tomography.ResultsPCV + SB improved arterial partial pressure of oxygen/inspiratory fraction of oxygen (PaO2/FiO2) by a reduction in intrapulmonary shunt fraction in HCl-ALI from 27% ± 6% to 23% ± 13% and in OA-ALI from 33% ± 19% to 26% ± 18%, whereas during PCV – SB PaO2/FiO2 deteriorated and shunt fraction increased in the HCl group from 28% ± 8% to 37% ± 17% and in the OA group from 32% ± 12% to 47% ± 17% (P < 0.05 for interaction time and treatment, but not ALI type). PCV + SB also resulted in higher EELV (HCl-ALI: 606 ± 171 mL, OA-ALI: 439 ± 90 mL) as compared with PCV – SB (HCl-ALI: 372 ± 130 mL, OA-ALI: 192 ± 51 mL, with P < 0.05 for interaction of time, treatment, and ALI type).ConclusionsSB improves oxygenation, reduces shunt fraction, and increases EELV in both models of ALI.
Highlights
Acute lung injury (ALI) can result from various insults to the pulmonary tissue
pressure-controlled ventilation (PCV) + spontaneous breathing (SB) improved arterial partial pressure of oxygen/ inspiratory fraction of oxygen (PaO2/FiO2) by a reduction in intrapulmonary shunt fraction in hydrochloric acid (HCl)-acute lung injury (ALI) from 27% ± 6% to 23% ± 13% and in oleic acid (OA)-ALI from 33% ± 19% to 26% ± 18%, whereas during PCV – SB PaO2/FiO2 deteriorated and shunt fraction increased in the HCl group from 28% ± 8% to 37% ± 17% and in the OA group from 32% ± 12% to 47% ± 17% (P < 0.05 for interaction time and treatment, but not ALI type)
PCV + SB resulted in higher end-expiratory lung volume (EELV) (HCl-ALI: 606 ± 171 mL, OAALI: 439 ± 90 mL) as compared with PCV – SB (HCl-ALI: 372 ± 130 mL, OA-ALI: 192 ± 51 mL, with P < 0.05 for interaction of time, treatment, and ALI type)
Summary
Acute lung injury (ALI) can result from various insults to the pulmonary tissue. Experimental and clinical data suggest that spontaneous breathing (SB) during pressurecontrolled ventilation (PCV) in ALI results in better lung aeration and improved oxygenation. On the other hand, during controlled ventilation, as the diaphragm relaxes, it is displaced by the weight of the contents of the abdominal cavity, leading to the redistribution of tidal volumes (VT) to anterior, non-dependent, and less perfused lung regions [13,18]. These effects may be even more pronounced in indirect ALI/ ARDS. We asked the question of whether SB during pressure-controlled ventilation (PCV) improves oxygenation, VA Q distribution, shunt fraction, and end-expiratory lung volume (EELV) in two different models of ALI. This research question was tested in porcine models of hydrochloric acid (HCl)-induced ALI and in the combination of oleic acid (OA) injection and elevated IAP
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