Gas exchange impairment induced by open suctioning in acute respiratory distress syndrome: impact of permissive hypercapnia.

摘要

OBJECTIVE: To determine whether hypercarbia occurs following the use of open suctioning in lung lavage injured sheep and whether the baseline PaCO2 and duration of suctioning affect gas exchange. DESIGN: Prospective laboratory evaluation. SETTING: Animal laboratory in a university hospital. SUBJECTS: Seven female Dorset sheep. INTERVENTIONS: Lung lavage was used to create acute respiratory distress syndrome (ARDS). Mechanical ventilation was provided to produce different baseline PaCO2 levels. MEASUREMENTS AND MAIN RESULTS: Lung injury was developed by isotonic saline lavage until the PaO2 decreased to 100-150 mm Hg on an FIO2 of 1.0, positive end-expiratory pressure (PEEP) 5 cm H2O, and tidal volume 10 mL/kg. Then tidal volume was decreased to 6 mL/kg. Open suctioning was performed on each animal. Each animal experienced four experimental conditions in random order (PaCO2 40 and 80 mm Hg and duration of suctioning 10 and 30 secs). Before each of the four experimental conditions, animals underwent lungrecruitment continuous positive airway pressure 40 cm H2O for 40 secs to normalize volume history followed by ventilation for 15 mins where FIO2 and PEEP were set based on the ARDSNet FIO2/PEEP. Mean arterial blood pressure, heart rate, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac output, and arterial blood gases were measured before, 1 min after, and then every 2 mins after open suctioning for 30 mins. Neither the duration of suctioning nor the baseline level of CO2 had an important influence on the magnitude of the desaturation and the recovery of PO2 following suctioning (p < .05). Level of PEEP did influence the recovery of PaO2 following suctioning. CONCLUSIONS: While neither baseline CO2 nor duration of suctioning affected the gas exchange alterations induced by endotracheal suction, high levels of PEEP can help to avoid the associated gas exchange abnormalities in ARDS.