Background:

High risk patients with lung disease who undergo cardiac surgery are at significant risk of postoperative complications leading to prolonged hospital stay. One method of reducing the risk of lung complications is to treat patients with non-invasive ventilation or continuous positive airways pressure postoperatively. However, this often requires admission to a high dependency unit or intensive care, and is uncomfortable because of the need for a tight fitting mask, as well as being labour intensive and costly. Nasal high flow oxygen (Optiflow™) is a new alternative as it provides warmed humidified oxygen at high flow, and also has been shown to assist breathing and improve recovery. It is comfortable during use and indeed may be more comfortable than standard (dry) oxygen via a facemask (Hudson type) or nasal prongs. It may be administered on a normal ward, however its routine use in high risk patients with lung conditions such as asthma, chronic obstructive pulmonary disease, recent chest infections and heavy smokers has not been tested before.

Aims/Objectives:

The primary aim of this clinical trial is to determine if prophylactic nasal high flow oxygen (Optiflow™) therapy in cardiac surgical patients at high-risk of developing post-operative pulmonary complications is associated with shorter hospital length of stay.

Methods:

High risk adult patients who are scheduled to undergo cardiac surgery will be recruited with full ethical approval and informed consent. Before surgery, each patient will perform a 6- minute walking test under the supervision of a physiotherapist. This simple tests measures how far patients can walk in 6 minutes. Additionally, patients will undergo spirometry testing which is used to assess how well the lungs work by measuring how much air the patient inhales and exhales and how quickly they exhale. Patients will thereafter undergo surgery under general anaesthesia as they would normally. After the operation they will be looked after following our recovery protocols, incorporating pain relief, regular physiotherapy, early mobilisation and eating and drinking, and removal of chest drains and tubes as soon as possible.

On arrival in the critical care area after their surgery, patients will be randomly assigned to receive supplemental oxygen via a soft facemask (Hudson Type) (standard group), or via high-flow nasal cannulae(Optiflow™) (intervention group). Patients will be administered oxygen for at least 24 hours after surgery.

Patients who develop breathing difficulty will receive treatment based on their clinical need. On the fifth or sixth postoperative day they will repeat the walking test and spirometry. The investigators will use a short questionnaire to determine if there is any difference in how patients feel they recovered before they leave hospital and how quickly they returned to normal activities after discharge, and also to evaluate how they tolerated either the facemask (Hudson Type) or high flow nasal cannulae (Optiflow™).

The investigators have used data from previous studies to calculate that a total of 74 patients will be needed to take part, in order to evaluate whether high flow nasal oxygen (Optiflow™) leads to reduced length of hospital stay after high risk cardiac surgery compared with usual care oxygen therapy.

Inclusion Criteria:

Patients are eligible for inclusion if:

• they are aged over 18 years
• are undergoing elective cardiac surgery (coronary artery bypass grafting, valve surgery or both)
• they have one or more patient-related risk factor for post-operative pulmonary complications (COPD, asthma, lower respiratory tract infection in last 4 weeks, body mass index≥35 kg/m2 current (last 6 weeks) heavy smokers (> 10 packyears)).
• they are capable of performing a 6MWT - The 6MWT is a clinical exercise test, and is popular in clinical practice because it aids clinical decision making, and because of the belief that it provides a better estimate of functional capacity than resting cardiorespiratory measurements (24). The 6MWT is the most popular clinical exercise test, which is used for postoperative evaluation after lung surgery and has also been validated in cardiac surgery

Exclusion Criteria:

• Contraindication to high flow nasal oxygen such as nasal septal defect.
• Not met extubation criteria by 10am the day after surgery (Day 1).
• Need for CPAP pre-operatively.