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Effects of lung recruitment maneuver and positiveend‐expiratory pressure on lung volume, respiratory mechanics and alveolar gas mixing in patients ventilated after cardiac surgery
Author(s) -
Dyhr T.,
Laursen N.,
Larsson A.
Publication year - 2002
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1034/j.1399-6576.2002.460615.x
Subject(s) - medicine , positive end expiratory pressure , anesthesia , oxygenation , fraction of inspired oxygen , respiratory physiology , lung volumes , mechanical ventilation , cardiac output , pulmonary compliance , lung , ventilation (architecture) , hemodynamics , mechanical engineering , engineering
Background: It is unclear whether positive end‐expiratory pressure (PEEP) is needed to maintain the improved oxygenation and lung volume achieved after a lung recruitment maneuver in patients ventilated after cardiac surgery performed in the cardiopulmonary bypass (CPB). Methods: A prospective, randomized, controlled study in a university hospital intensive care unit. Sixteen patients who had undergone cardiac surgery in CPB were studied during the recovery phase while still being mechanically ventilated with an inspired fraction of oxygen (FiO 2 ) 1.0. Eight patients were randomized to lung recruitment (two 20‐s inflations to 45 cmH 2 O), after which PEEP was set and kept for 2.5 h at 1 cmH 2 O above the pressure at the lower inflexion point (14±3 cmH 2 O, mean ±SD) obtained from a static pressure‐volume (PV) curve (PEEP group). The remaining eight patients were randomized to a recruitment maneuver only (ZEEP group). End‐expiratory lung volume (EELV), series dead space, ventilation homogeneity, hemodynamics and PaO 2 (oxygenation) were measured every 30 min during a 3‐h period. PV curves were obtained at baseline, after 2.5 h, and in the PEEP group at 3 h. Results: In the ZEEP group all measures were unchanged. In the PEEP group the EELV increased with 1220±254 ml ( P< 0.001) and PaO 2 with 16±16 kPa ( P< 0.05) after lung recruitment. When PEEP was discontinued EELV decreased but PaO 2 was maintained. The PV curve at 2.5 h coincided with the curve obtained at 3 h, and both curves were both steeper than and located above the baseline curve. Conclusions: Positive end‐expiratory pressure is required after a lung recruitment maneuver in patients ventilated with high FiO 2 after cardiac surgery to maintain lung volumes and the improved oxygenation.