Abstract
Dear Editor,
We thank the authors for their interest in physiotherapy-delivered postoperative NIV and for their opinions regarding our paper.
The small study by Yağlıoğlu et al. [1] of COPD patients undergoing upper abdominal surgery found no statistical difference in PaO2, PaCO2, SpO2, and respiratory rate one hour following surgery between those who received CPAP or BiPAP. On this data alone it is incorrect to claim that either mode is superior or to extrapolate this to other patient cohorts as this study only involved patients with COPD. Our choice to use BiPAP was based pragmatically on the predominant use of this mode at our facility and the untested hypotheses that the pressure differentials during the breath cycle particular to BiPAP may have benefits in compensating for respiratory pump deficiencies following upper abdominal surgery [2].
Presently, there is no consensus on the ideal mode, pressures, or durations of prophylactic NIV and as such our protocol was guided by expert recommendations [2]. We aimed to provide a clinically realistic protocol where pressures were initiated at a set minimum (IPAP 10, EPAP 5 cmH2O) and increased to a target maximum (IPAP 15, EPAP 10 cmH2O) dependent on patient tolerance with a minimum allowable driving pressure of 4 cmH2O. We reported the mean pressures successfully delivered so that results can be interpreted within pragmatic intention-to-treat principles. Whilst gas exchange and pulse-oximetry data may be useful, we agree with Glossop and Esquinas [3] that physiological end points such as these may not be as meaningful in determining effectiveness as clinical outcomes such as PPCs and reintubation rates.
We agree that more evidence is required to determine the effectiveness of postoperative prophylactic NIV, and indeed, timing of NIV initiation may be a crucial factor and may require multidisciplinary teams to facilitate. A key finding of our study was that the target NIV initiation time of four hours within extubation was achieved in only 11% of patients. This was due to a limited after-hours and weekend physiotherapy service. Our findings were also limited by the non-parallel group design and non-standardisation of chest physiotherapy in the NIV group. To address these limitations, including factors raised by the corresponding authors, we are currently undertaking a pilot randomised controlled trial to assess the feasibility, safety, and possible effectiveness of physiotherapy provided postoperative NIV after high-risk upper abdominal surgery [4].
Citation
Response to Letter to the Editor re: ‘Physiotherapist administered, non-invasive ventilation to reduce postoperative pulmonary complications in high-risk patients following elective upper abdominal surgery; a before-and-after cohort implementation study’