http://orcid.org/0000-0002-6505-6019
We thank Bhakta et al. for showing keen interest in our study (Citation1). The authors raise certain pertinent points about the study. We agree that more evidence is required before closed loop ventilation modes can be routinely adopted for the delivery of non-invasive ventilation (NIV) during acute respiratory failure. Our study was infact a feasibility study to investigate if adaptive support ventilation (ASV) could be used during NIV (Citation1). The results of our study suggest that ASV can be safely used during NIV.
The success of NIV is highly dependent upon patient comfort and patient-ventilator synchrony. ASV by modulating the tidal volume delivered and the respiratory rate meets the patients’ requirements and reduces the work of breathing (Citation2). Thus, theoretically due to better patient-ventilator interaction, NIV failures rates should be lower with ASV mode. Although the use of sedatives can facilitate the delivery of NIV by alleviating anxiety and distress, it can also cause harm by increasing the risk of aspiration and prolonging hospital stay (Citation3, Citation4). There is also little evidence to support the routine use of sedation during NIV.
The study subjects in our study were those with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Higher inspiratory pressures are required to overcome the airway resistance to deliver tidal volume in subjects with AECOPD (Citation5). Higher inspiratory pressures could also suggest early recovery of inspiratory muscle strength in the ASV arm (Citation6). Thus, the delivery of high peak pressures with ASV is not surprising. We agree with Bhakta et al. that higher tidal volumes even during NIV can be harmful. However, the tidal volumes in our study were well within the safe range of 6–8 ml/kg. Also, none of patients in the current study developed pneumothorax. The deaths in the study were not directly related to NIV failure (intracranial bleed, cardiac arrythmia and refractory septic shock) but due to the underlying disease.
The patients’ comfort during the delivery of NIV was measured using the visual analogue scale (VAS) in both the study arms and was found to be similar. The mask tolerance and pressure sores can be avoided by explaining the procedure to the patient, selecting a proper sized mask, ensuring the mask is not too tightly placed, adding humidification and giving intermittent off periods during the NIV use (Citation4). The mask intolerance was seen in seven subjects and was not different between the two groups in the current study. Thus, the use of ASV mode during NIV was safe and requires further evaluation in a larger multicentric trial.
Disclosure statement
No potential conflict of interest and financial disclosures were reported by the authors.
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