Assessment of the generation of respiratory pressure by high flow nasal prongs using pressure measuring and lung imaging techniques

Following cardiac surgery, patients who are already receiving Nasal High Flow (NHF) as part of their usual care will be approached to participate in this study (NHF = blended air and oxygen which has been warmed and humidified and delivered via nasal cannula at flows of up to 50L/min. Patients may receive this therapy for a few hours or a few days depending on their clinical condition). The research procedure is as follows: 1 Informed consent 2 Insert pressure measuring catheter into the patient’s nasopharynx. 3 Attach belt of electrodes around patient’s chest. 4 Change from NHF to face mask oxygen therapy 5 10 -15 min wash out period 6 Arterial blood gas taken if Arterial line is in situ 7 Simultaneous pressure measurements and electrical readings recorded for a 2 min period. 8 Change from face mask oxygen therapy to NHF 9 10 - 15 min wash out period 10 Arterial blood gas taken if arterial line is in situ 11 Simultaneous pressure measurements and electrical readings recorded for a 2 min period 12 Remove pressure measuring catheter 13 Remove belt of electrodes 14 Continue with usual care Patients will receive the same concentration of oxygen with either therapy and this will be dictated by the patient’s clinical requirements. Physiological and demographic data from the patient’s medical chart will also be recorded.