http://orcid.org/0000-0002-6101-396X
To the Editor:
We read with interest the comparison by Sehgal IS et al. of the benefits of pressure support (PSV) and adaptive support ventilation (ASV) in patients presenting with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) (Citation1). We congratulate the authors on this interesting study, and wish to discuss some details.
The use of “intelligent” modes to optimize the delivery of the noninvasive ventilation in AECOPD is perhaps prematurely considered state-of-the-art, since clear outcome benefits are not fully established (as regards subsequent intubation or mortality) (Citation2). In the present study, the authors found a non-significant reduction in intubation rates, and delayed time to intubation in the ASV group albeit in association with a higher mortality. This appears to undermine the case for ASV. However, the choice of ventilation mode is one of many factors that can lead to NIV failure. Others such as air leaks, muscular fatigue, and patient–ventilator asynchrony are well known (Citation3); but hard to objectively record. Similarly, the need for sedation to offset patient–ventilator asynchrony or optimize tolerance during aggressive ventilatory support might also ideally be considered as contributing to the outcome (Citation4). We would welcome the authors’ comments on these variables, while acknowledging that they are difficult to protocolize.
We also note considerable variation in the peak inspiratory pressures (PIP) applied between the groups (18.1 vs. 14.8 cmH2O; p < 0.01), with ASV requiring the higher PIP. This will, of course, affect gas leakage, asynchrony and mask tolerance. The higher tidal volumes thus generated (6.7 vs. 5.9 ml/kg) probably improved arterial blood gas results in the ASV group, thereby delaying intubation. Given the possibility of iatrogenic lung injury from higher pressures, we would welcome more information about compliance or resistance in these patients (Citation5), if recorded.
Finally, we would welcome any summary data on the tolerability of the masks and modes used, or the steps taken to optimize this. It is often a major challenge in the delivery of NIV beyond the very short term. These details would help evaluate the relevance of the present study to our clinical practice.
Pradipta Bhakta,
Habib Md Reazaul Karim,
Brian O’Brien,
Antonio Esquinas.
Category of the article
Correspondence in response to previously published article.
Financial support
No funding other than personal was used in conducting the audit as well as writing the manuscript. We declare that we have no financial and/or personal relationships with other people or organizations that could inappropriately influence (bias) our work.
Conflict of interest
The authors report no conflicts of interest.
References
- Sehgal IS, Kalpakam H, Dhooria S, Aggarwal AN, Prasad KT, Agarwal R. A Randomized controlled trial of noninvasive ventilation with pressure support ventilation and adaptive support ventilation in acute exacerbation of COPD: A Feasibility Study. COPD. 2019;1–6. doi:10.1080/15412555.2019.1620716. [Epub ahead of print]
- Simonds AK, Hare A. New modalities for non-invasive ventilation. Clin Med (Lond). 2013;13 Suppl 6:S41–S5. doi:10.7861/clinmedicine.13-6-s41.
- Moerer O, Harnisch L-O, Herrmann P, Zippel C, Quintel M. Patient-ventilator interaction during noninvasive ventilation in simulated COPD. Respir Care. 2016;61:15–22. doi:10.4187/respcare.04141.
- Nava S. Behind a mask: tricks, pitfalls, and prejudices for noninvasive ventilation. Respir Care. 2013;58:1367–1376. doi:10.4187/respcare.02457.
- Agarwal R, Srinivasan A, Aggarwal AN, et al. Adaptive support ventilation for complete ventilatory support in acute respiratory distress syndrome: a pilot randomized controlled trial. Respirology. 2013;18:1108–1115.