NIPPER-PLUS: Does intermittent non-invasive ventilation prevent postoperative pulmonary complications following major upper abdominal surgery?

Extubation post-surgery onto high flow nasal prongs (HFNP) which will have fraction of inspired oxygen (FiO2) titrated to achieve a peripheral oxygenation (SpO2) of between 92-96% unless otherwise specified by attending anaesthetist (i.e. severe COPD). Gas flow rate will be set at 50l/min and can be decreased to a minimum of 30l/min if the patient requires for tolerance. HFNP is to be provided continuously from end of surgery (Day 0) to 48 hours later (Day 2). The intervention group will get an additional single 30-minute Bi-Level Positive Airway Pressure Non-Invasive Ventilation (BiPAP-NIV) session within four hours of extubation by either the attending anaesthetist or the specialist surgical physiotherapist (Day 0) then twice daily, 30-minute sessions of BiPAP-NIV on Day 1 and Day 2 with a Physiotherapist. BiPAP NIV will be delivered via facemask by a VPAP Resmed machine. This will be carried out with patients either sitting up in bed with the head of bed raised between 45 – 90 degrees as tolerated or sitting out of bed in a high back chair. Expiratory positive airway pressure (EPAP) will be set at 10cmH20. Inspiratory positive airway pressure (IPAP) will be initially set at 15cmH20 and adjusted as required to achieve tidal volumes of at least 6-8mls/kg. Participants with BMI > 30 will have a starting EPAP set at 12cmH20 and a starting IPAP set at 16cmH20. The difference between IPAP and EPAP (known as pressure support ventilation (PSV)) will be a minimum of 4cmH20 and the maximum total pressure (PSV + EPAP) will be no greater than 25cmH20. If a participant is unable to tolerate the set pressures, reassurance will firstly be given to the participant and the following modifications will be taken in sequential order, until patient tolerance is achieved: 1. Reduce EPAP to 8cmH20 (set minimum) 2. Reduce IPAP to 12cmH20 (set minimum) in decrements of 1cmH20. If the participant remains unable to tolerate the therapy despite pressure titration and reassurance, cessation of NIV therapy will occur and will be reported. Pressure rise time will be set at the slowest speed (900ms) and the inspiratory trigger will be set at the minimum value. Inspired gases will be heated and humidified via the VPAP Resmed machine. Air-leaks will be managed by fitting the correct size mask carefully with focus on leaks around the nasogastric tube. Any air leak will be monitored and recorded. Fi02 will be titrated to achieve Sp02 >92-96% unless otherwise specified by the medical team (i.e. COPD). The patient will be continuously monitored by the treating physiotherapist for the duration of the therapy and again at 30-minutes post BiPAP-NIV. Pre-operative physiotherapy education session (Boden et al, ACTRN12613000664741.) and post-op early ambulation protocol (Boden et al,) will be provided as per the LIPPSMAck-POP trial intervention group (ACTRN12613000664741). One (1) 20-30 minute pre-operative education session delivered by a Physiotherapist at the standard outpatient Pre-Admission Clinic appointment. The education is to be provided within 6 weeks of the schedued operation date and will be performed in person, however, if this is not possible, the patient will be contacted by phone and provided with the education and training via telephone and the booklet sent via mail. The pre-operative physiotherapy session will consist of education on the prevention of post-operative pulmonary complications stressing the importance of early post-operative ambulation and the performance of self-directed deep breathing and coughing (DB&C) exercises immediately from waking from the operation. Patients will be informed that the further they walk and the more often they walk away from the bedside each day following their operation the better their chance of avoiding serious post-operative complications (chest infection or deep vein thrombosis). They will be informed that a Physiotherapist will see them on the first post-operative day and assist them out of bed to walk as far as possible. They will be told that they will be walking at a pace that gets them a bit breathless and will be familiarised with the 0-10 Borg scale Rating of Perceived Exertion (RPE). They will be told that each time they walk it should feel like a 3-4/10 in exertion. After the first post-operative day session with the Physiotherapist they will be encouraged strongly to walk or exercise by their bedside as often as they can by themselves or with the assistance of a nurse or carer. As it is frequently not possible to ambulate as early and as often as recommended, participants will be encouraged (during the pre-operative intervention) to perform self-directed breathing exercises to protect their lungs during this time in bed. They will be instructed to perform the DB&C exercises immediately from waking from the anaesthetic and then every hour during daytime waking hours until their first ambulation session, and then at any time when they are not ambulant. The physiotherapist will then coach each participant in at least three repetitions, and as many as required to master technique, of two sets of 10 slow-flow breaths to maximum inspiratory capacity with two to three inspiratory sniff breath stacking manoeuvres. Each breath is held for three to five seconds. Each set of 10 breaths are followed by three coughs, or a forced expiratory technique with an open glottis called a “huff”, with a small firm pillow pressed over on the abdominal incision to support the wound and to encourage greater expiratory force. Participants will be encouraged to practice these exercises prior to their operation to develop familiarity. Each patient in the intervention group will be given an estimate of their likelihood of getting a PPC based on available pre-operative information (type of procedure proposed, booked post-operative admission to ICU, usual length of procedure, respiratory co-morbidity, self rated fitness levels, current smoker). Patients will be informed that aggressive early self directed DB & C exercises and ambulation is effective in reducing this known risk of a PPC. Participants will be provided with an accompanying education booklet outlining what was presented on prevention of PPC, post-operative physiotherapy, early ambulation, self directed DB&C (2 sets of 10 DB followed by 3 coughs every hour during daytime) and the expected recovery process. Post-operatively participants will be provided with a standardised physiotherapy assisted early mobilisation program and reminded to do the DB&C exercises as per the booklet provided. No further coached respiratory physiotherapy is provided. To reduce confounding variables no other pre- or post-operative respiratory physiotherapy will be provided.