Effects of patient ventilator asynchrony (PVA) on gas exchange, respiratory muscle load, patient comfort and adherence to non-invasive ventilation (NIV)

Introduction:PVA may adversely affect gas exchange, respiratory muscle unloading and patient comfort. We investigated the relationship between PVA, physiological and patient-centred outcomes, hypothesising that PVA would lead to poor ventilatory adherence. Methods:Patients requiring domiciliary NIV were enrolled. NIV was titrated using capnometry and oximetry. PVAs were scored using our standard definitions and quantified as percentage of total breaths analysed. We investigated the relationship between PVA at initiation of NIV and (1) time spent with oxygen saturations 2 levels > 7kPa; and (3) patient perception of comfort and co-ordination with the ventilator using visual analogue scores. Parasternal electromyogram (sEMGpara%max) was measured as a marker of neural respiratory drive to chest wall muscles and compared to PVA at initiation of NIV. Ventilator adherence data (log hours) was collected at 6 weeks post commencing NIV. Results:20 patients(11male) participated; 8 chronic obstructive pulmonary disease, 7 obesity hypoventilation syndrome and 5 neuromuscular disease. There was a direct relationship between PVA at initiation of NIV and EMGpara%max (r=0.46; p=0.04). No significant correlation was observed between PVA and overnight gas exchange, patient reported comfort and co-ordination scores or adherence to ventilation. Conclusion:PVA adversely effects respiratory muscle unloading however, it does not negatively impact on ventilatory control or patient perception of comfort on NIV. PVA was not associated with ventilatory adherence questionning its role in achieving successful domiciliary NIV set up.