Protocol for a randomised controlled trial of nasal high flow oxygen therapy compared to standard care in patients following cardiac surgery: the HOT-AS study

Background: Postoperative respiratory complications following cardiac surgery may increase morbidity, mortality and length of stay. Non-invasive respiratory support therapies can be used prophylactically or curatively to reduce respiratory complications. One system, nasal high flow oxygen therapy, is in use in many intensive care units (ICUs) however there is a lack of information regarding its clinical utility and efficacy.

Objectives: This paper outlines the study protocol and methodology for a study designed to determine if the prophylactic use of nasal high flow oxygen therapy can improve pulmonary function in patients following cardiac surgery.

Methods/design: A prospective randomised controlled trial will be conducted of adult patients scheduled for cardiac surgery and admitted to the Cardiothoracic Intensive Care Unit of a tertiary hospital. Study participants will be assigned to receive either nasal high flow or standard oxygen therapy (oxygen therapy at 2-4 L/min via either simple facemask or nasal cannulae) at extubation. The primary outcome measure is improved pulmonary function demonstrated by SpO2/FiO2 ratio >445 on post-operative day 3. Secondary outcome measures include atelectasis score on chest X-ray; spirometry; readmission to ICU for respiratory causes; ICU and hospital length of stay; mortality and incidence of respiratory complications at day 28; oxygenation variables; use of adjunctive respiratory support therapies; escalation of respiratory support; adverse events and patient comfort during administration of oxygen therapy.

Sample size: It was calculated that 340 patients will be required--170 per arm of study--to give a 90% power to detect a 15% treatment effect.

Results: This study started recruiting in March 2011. It is anticipated that enrollment will be complete in April 2012 and results available towards the end of 2012.

Conclusion: This study will provide evidence of any benefits in the use of prophylactic nasal high flow therapy in post-operative cardiac surgical patients.

Trial registration: This trial is registered with the Australian New Zealand Clinical Trials Registry www.anzctr.org.au (ACTRN12610000973011).