Continuous Positive Airway Pressure After Abdominal Surgery

This is a randomized controlled trial with an allocation ratio of 1:1. Half the patients are randomized to continuous positive airway pressure (CPAP) and half to routine medical care. Included are one hundred and twenty patients aged 18-80 years plus patients with ongoing CPAP scheduled for abdominal surgery at Umeå university hospital. The primary outcome is oxygen partial pressure (PaO2) measured on postoperative day 2 compared with the day before surgery. Secondary outcomes include diffusion capacity for carbon-monoxide, vital capacity, FEV1 and carbon-dioxide partial pressure (PaCO2) on postoperative day 2 compared with the day before surgery. PaO2 and PaCO2 are recorded from blood gas measurements obtained from the radial artery. Percentage of nocturnal hypoxia defined as the percentage of oxygen saturation during 90% of the second postoperative night. Tolerance to CPAP measured by the number of hours used CPAP. Side effects related to CPAP. All patients are examined with a simplified sleep apnea examination (Noxturnal T3, Res Med) the night before surgery. Patients in the CPAP treated group are given an auto-CPAP with a minimum pressure of 5 cm and a maximum pressure of 10 cm. They will be treated with CPAP for at least 2 hours immediately after surgery and during the first two postoperative nights. Oxygen is supplied to CPAP if oxygen saturation falls below 90%. Patients in the control group receives standard treatment and supplemental oxygen if oxygen saturation falls below 90%. In a third arm, we will include patients who already are using CPAP at night at home for previously diagnosed obstructive sleep apnea. are instructed to use CPAP for 2 hours immediately after surgery and subsequent nights during hospital stay.