Nasal Oxygen Therapy After Cardiac Surgery

NOTACS aims to determine if prophylactic use of high-flow nasal therapy (for a minimum of 16 hours after tracheal extubation, inclusive of up to one hour off randomised therapy for transfers around the hospital and/or physio mobilisation) increases days at home in the first 90 days after surgery, for adult patients undergoing cardiac surgery who are at high risk of postoperative pulmonary complications. The study also incorporates a health economic analysis to estimate the incremental cost-effectiveness and cost-utility of HFNT versus standard oxygen therapy at 90 days, from the view-point of the public sector, NHS and patients.

Patients undergoing cardiac surgery are at significant risk of postoperative pulmonary complications that may lead to prolonged ICU and hospital stay and increase mortality. The incidence of respiratory complications may be three to four times more common in patients with intrinsic respiratory disease and lower airway obstruction (including asthma or chronic obstructive pulmonary disease (COPD)), or obese patients or current heavy smokers (\> 10 pack years).

High-flow nasal therapy (HFNT) is increasingly used as a non-invasive form of respiratory support. It delivers low level, flow-dependent positive airway pressure, and is much better tolerated by patients than alternatives such as continuous positive airway pressure (CPAP) or non-invasive ventilation. Patients can talk, eat, drink and walk whilst using HFNT. However, there is equipoise regarding its prophylactic use and effect on important patient-centred outcomes. Before the intervention is recommended for routine NHS use in cardiac surgery patients at high risk of pulmonary complications, whether it improves patient-related outcomes and is cost effective in a UK setting needs to be assessed.

Eligibility Criteria:
Inclusion Criteria:

* Aged 18 years or over.
* Undergoing any elective or urgent first-time or redo cardiac surgery performed on cardiopulmonary bypass
* Have one or more clinical risk factors for postoperative pulmonary complications (COPD, asthma, lower respiratory tract infection in last 4 weeks as defined by use of antibiotics, body mass index ≥35 kg/m2 , current (within the last 6 weeks) heavy smoker (\> 10 pack years)) (47, 48).

Asthma is a disease characterized by recurrent attacks of breathlessness and wheezing, and patients will have been prescribed medication by inhalers or nebulisers (either bronchodilators or steroids).

Chronic Obstructive Pulmonary Disease (COPD) is an umbrella term used to describe chronic lung diseases that cause limitations in lung airflow. The more familiar terms 'chronic bronchitis' and 'emphysema' are no longer used but are now included within the COPD 13 diagnosis. The most common symptoms of COPD are breathlessness, or a 'need for air', excessive sputum production, and a chronic cough. Patients suitable for the NOTACS study will have been prescribed medication by inhalers or nebulisers (either bronchodilators or steroids).

Exclusion Criteria:

* Requiring home oxygen therapy.
* Deep hypothermic circulatory arrest planned
* Contraindication to HFNT, e.g. nasal septal defect.
* Requirement for home ventilatory support (including: HFNT, CPAP, BiPAP)
* Requiring emergency cardiac surgery defined as surgery required within 24 hours of the decision to operate.
* Patients not fluent in English.