Changes in respiratory mechanics and gas exchange during the acute respiratory distress syndrome

Nunes, S; Valta, P; Takala, J (2006). Changes in respiratory mechanics and gas exchange during the acute respiratory distress syndrome. Acta anaesthesiologica Scandinavica, 50(1), pp. 80-91. Oxford: Wiley-Blackwell 10.1111/j.1399-6576.2005.00767.x

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BACKGROUND: The time course of impairment of respiratory mechanics and gas exchange in the acute respiratory distress syndrome (ARDS) remains poorly defined. We assessed the changes in respiratory mechanics and gas exchange during ARDS. We hypothesized that due to the changes in respiratory mechanics over time, ventilatory strategies based on rigid volume or pressure limits might fail to prevent overdistension throughout the disease process. METHODS: Seventeen severe ARDS patients {PaO2/FiO2 10.1 (9.2-14.3) kPa; 76 (69-107) mmHg [median (25th-75th percentiles)] and bilateral infiltrates} were studied during the acute, intermediate, and late stages of ARDS (at 1-3, 4-6 and 7 days after diagnosis). Severity of lung injury, gas exchange, and hemodynamics were assessed. Pressure-volume (PV) curves of the respiratory system were obtained, and upper and lower inflection points (UIP, LIP) and recruitment were estimated. RESULTS: (1) UIP decreased from early to established (intermediate and late) ARDS [30 (28-30) cmH2O, 27 (25-30) cmH2O and 25 (23-28) cmH2O (P=0.014)]; (2) oxygenation improved in survivors and in patients with non-pulmonary etiology in late ARDS, whereas all patients developed hypercapnia from early to established ARDS; and (3) dead-space ventilation and pulmonary shunt were larger in patients with pulmonary etiology during late ARDS. CONCLUSION: We found a decrease in UIP from acute to established ARDS. If applied to our data, the inspiratory pressure limit advocated by the ARDSnet (30 cmH2O) would produce ventilation over the UIP, with a consequent increased risk of overdistension in 12%, 43% and 65% of our patients during the acute, intermediate and late phases of ARDS, respectively. Lung protective strategies based on fixed tidal volume or pressure limits may thus not fully avoid the risk of lung overdistension throughout ARDS.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Intensive Care, Emergency Medicine and Anaesthesiology (DINA) > Clinic of Intensive Care
UniBE Contributor:	Takala, Jukka
ISSN:	0001-5172
ISBN:	16451155
Publisher:	Wiley-Blackwell
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:49
Last Modified:	05 Dec 2022 14:15
Publisher DOI:	10.1111/j.1399-6576.2005.00767.x
PubMed ID:	16451155
Web of Science ID:	000235005500012
URI:	https://boris.unibe.ch/id/eprint/20398 (FactScience: 3689)