Regional lung derecruitment after endotracheal suction during volume- or pressure-controlled ventilation: a study using electric impedance tomography
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To assess lung volume and compliance changes during open- and closed-system suctioning using electric impedance tomography (EIT) during volume- or pressure-controlled ventilation.
Design and setting
Experimental study in a university research laboratory.
Nine bronchoalveolar saline-lavaged pigs.
Open and closed suctioning using a 14-F catheter in volume- or pressure-controlled ventilation at tidal volume 10 ml/kg, respiratory rate 20 breaths/min, and positive end-expiratory pressure 10 cmH2O.
Measurements and results
Lung volume was monitored by EIT and a modified N2 washout/-in technique. Airway pressure was measured via a pressure line in the endotracheal tube. In four ventral-to-dorsal regions of interest regional ventilation and compliance were calculated at baseline and 30 s and 1, 2, and 10 min after suctioning. Blood gases were followed. At disconnection functional residual capacity (FRC) decreased by 58 ± 24% of baseline and by a further 22 ± 10% during open suctioning. Arterial oxygen tension decreased to 59 ± 14% of baseline value 1 min after open suctioning. Regional compliance deteriorated most in the dorsal parts of the lung. Restitution of lung volume and compliance was significantly slower during pressure-controlled than volume-controlled ventilation.
EIT can be used to monitor rapid lung volume changes. The two dorsal regions of the lavaged lungs are most affected by disconnection and suctioning with marked decreases in compliance. Volume-controlled ventilation can be used to rapidly restitute lung aeration and oxygenation after lung collapse induced by open suctioning.
KeywordsAcute Lung Injury Electrical impedance tomography Functional residual capacity Monitoring Suctioning Lung recruitment
We thank Dr. Sven Lethvall, Dr. Anette Nyberg, and Marita Ahlqvist EMA for valuable assistance during experiments. The authors are grateful for advice from Mr. Eckhard Teschner, Dräger Medical AG, concerning the EIT equipment.
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