The purpose of this study is to determine whether prophylactic nasal continuous positive airway pressure (nCPAP) in the post-anaesthesia care unit (PACU) improves post-operative pulmonary function following elective bowel surgery. The investigators hypothesize that one hour of nCPAP in the PACU will result in a higher partial pressure of arterial oxygen (PaO2) when compared to the standard treatment of low flow oxygen applied by face mask.

Post-operative pulmonary complications, such as hypoxemia, pneumonia and respiratory failure, occur in 5-10% of patients following abdominal surgery. These post-operative pulmonary complications result in increased morbidity, mortality, ICU admission, length of hospital stay and resource use.

CPAP has shown to be an effective treatment for hypoxemia following abdominal surgery. It decreases atelectasis formation the risk of pneumonia. Application of nCPAP to treat hypoxemic respiratory failure following thoraco-abdominal surgery has shown to decrease endotracheal intubation.

Nasal CPAP has shown to be effective prophylaxis following elective cardiac and thoraco-abdominal aortic surgery. It reduces the incidence of hypoxemia, pneumonia, re-intubation and re-admission to the ICU. It has also shown to decrease the length of hospital stay.

The use of nCPAP immediately post-operatively in the PACU following abdominal surgery has not been evaluated. Nasal CPAP is better tolerated than full face mask CPAP. It allows for effective clearance of respiratory secretions, improved communication and decreases claustrophobic sensation. The PACU is a transition period from general anaesthesia into the post-operative recovery phase. During this time, residual anaesthetic causes decreased level of consciousness and sub-optimal respiratory effort. Reversal agent for neuromuscular blockade has often not reached its peak effect. Inadequate pain control may further decrease respiratory effort. This transition period may be when maximal atelectasis of alveolar lung units occurs. This time period may be optimal for the application of nCPAP for prophylaxis against hypoxemia. It may improve post-operative pulmonary function which could decrease post-operative morbidity, mortality, length of hospital stay and resource use.

Inclusion Criteria:

• patients scheduled to undergo laparotomy for elective bowel surgery

Exclusion Criteria:

• age < 18 years
• postoperative admission to the intensive care unit
• a history of allergy/intolerance to Ametop