DOI: 10.1097/01.sa.0000087669.65158.16
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Issn Print: 0039-6206
Publication Date: 2003/08/01
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Excerpt
(Anesthesiology, 96:795-802,2002), *Servizio di Anestesiologia e Rianimazione, Ospedale di Venere, Bari, Italy; †Dipartimento di Neuroscienze-Sezione di Fistologia, Universita di Torino, Torino, Italy; ‡ Dipartimento di Chirugia-Terapia Intensiva, Cattedre di Anestesiologia e Rianimazione, Ospedale S. Chiara, Universita di Pisa, Pisa, Italy; §Service de Réanimation Medicale, Hopital Henri Mondor, Université Paris XII, Paris, France; and ∥St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada.
A lung-protective ventilatory approach with low tidal volume (VT) has been proposed for use in acute respiratory distress syndrome (ARDS). Alveolar derecruitment may occur during the use of a lung-protective ventilatory approach, which may be averted by recruiting maneuvers. The hypothesis that the effectiveness of a recruiting maneuver to improve oxygenation in patients with ARDS would be influenced by the elastic properties of the lung and chest wall was explored. Twenty-two ARDS patients were studied during the onset of the ARDSNet lung-protective ventilatory approach:VT was set at 6 mL/kg of predicted body weight and positive end-expiratory pressure (PEEP) and inspiratory oxygen fraction (FIo2) were set to obtain an arterial oxygen saturation of 90% to 95% and/or an arterial partial pressure (Pao2) of 60 to 80 mm Hg (baseline). Measurements of Pao2/FIo2 static volume–pressure curve, recruited volume (vertical shift of the volume–pressure curve), and chest wall elastance (EstW and EstL; esophageal pressure) were obtained on zero end-expiratory pressure, at baseline, and at 2 and 20 minutes after a recruiting maneuver (40 cm H2O of continuous positive airway pressure for 40 seconds) was applied. Cardiac output (transesophageal Doppler) and mean arterial pressure were measured immediately before, during, and immediately after the recruiting maneuver. Patients were classified a priori as responders and nonresponders based on the occurrence or nonoccurrence of a 50% increase in Pao2/FIo2 after the recruiting maneuver. Recruiting maneuvers increased Pao2/FIo2 by 20% ± 3% in nonresponders (n = 11) and by 175% ± 23% (n = 11; mean ± standard deviation) in responders. On zero expiratory pressure EstL (28.4 ± 2.2 vs. 24.2 ± 2.9 cm H2O/L) and EstW (10.4 ± 1.8 vs. 5.6 ± 0.8 cm H2O/L) were higher in nonresponders than in responders. Nonresponders had been ventilated for a longer period than responders (7 ± 1 vs. 1 ± 0.3 days). Cardiac output and mean arterial pressure decreased by 31% ± 2% and 19% ± 3% in nonresponders and by 2% ± 1% and by 2% ± 1% in responders. Applying recruiting maneuvers improves oxygenation only in patients with early ARDS who do not have impaired chest wall mechanics and who have a large potential for recruitment, as indicated by the low values of Est.
