A44-26 Nasal High Flow With Expiratory Flow Relief: Effects on the Ventilation and Patient Comfort in COPD Patients During Acute Exacerbation

Rationale Nasal High Flow (NHF) has become an established form of respiratory support in a broad range of patients. The asymmetrical cannula interface has been shown to accelerate the clearance of dead space in upper airways and increase positive airway pressure. Both effects are flow-dependent and contribute to the key physiological mechanisms of NHF. It is known that an increase of NHF rate is not always well-tolerated, particularly in patients with a lower breathing frequency. The study tested the hypothesis that expiratory flow relief (NHFrelief), which modulates the expiratory pressure profile without reducing its value at the end of expiration, can improve the tolerance of COPD patients to higher NHF settings without diminishing physiological benefits. Methods NHF at 30 L/min and NHFrelief at 50 L/min were delivered by AIRVO3 device and Optiflow Duet cannula interfaces (Fisher & Paykel Healthcare, New Zealand) in a group of COPD patients admitted with acute exacerbation. Each condition was applied for 45 min in a randomised crossover design. When supplemental oxygen was required, FiO2 was individually adjusted. Ventilation was assessed by calibrated inductance plethysmography, and transcutaneous SpO2 and transcutaneous pCO2 along with lung mechanics parameters, were continuously monitored and recorded. Patient comfort was assessed by a five-item smiley scale (+2 very comfortable, 0 = neutral, -2 = very uncomfortable) for airflow, warmth, humidity, and noise after each phase. Results In 22 patients (9 female; age 67.8±9.2; BMI 24.8±8.7; FEV1 36.4±14.9; pCO2 45.0±9.6; CAT 23.2±7.9; mMRC 3.2±1.2; Multidimensional Dyspnea Profile A1-Scale 5.1±2.9 of 10), NHF with both modes had a similar impact on respiratory rate and ventilation, while pCO2 and SpO2 also differed significantly between the phases (see Table 1). Both modes were equally rated with neutral (0) to comfortable (1), in Median: 1, SD 0.51 with no negative impact of the higher flow under NHFrelief. Conclusions In COPD exacerbation, NHF applied for 45 min reduced respiratory rate by prolonging both inspiratory and expiratory times and decreased pCO2, with a further reduction observed at the higher flow used in the expiratory flow relief mode. Both NHF 30 L/min and NHFrelief 50 L/min were similarly well tolerated. Further studies are needed to confirm these findings over a longer duration or during overnight application.