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JOURNAL CLUB - Phenotypes of Patients with COVID-19 Who Have a Positive Clinical Response to Helmet NIV

By: Marcelo Alcantara, Médico - 04/26/2022 16:11

Are there markers of response to noninvasive respiratory support with HELMET in COVID-19?

In the HENIVOT study (Grieco DL et al. Effect of helmet noninvasive ventilation vs. high-flow nasal oxygen on days free of respiratory support in patients with COVID-19 and moderate to severe hypoxemic respiratory failure: the HENIVOT randomized clinical trial. JAMA 2021); the use of NIV with HELMET resulted in a lower rate of endotracheal intubation (ETI) and more ventilatory support-free days than HFNC use. Therefore, a search for identifying phenotypic characteristics associated with the response to the use of this interface with NIV is warranted.

The authors performed a post-hoc analysis of 109 patients with hypoxemic respiratory failure (PaO2/FIO2 < 200) included in the study and assessed the following baseline parameters: PaO2/FIO2, PaCO2, respiratory rate, visual analog scale dyspnea (VAS) score ), singly or grouped into composite indices.

In patients with PaCO2 < 35mmHg (n=59, 54%), with hyperventilation, there was greater benefit from the use of HELMET-NIV compared to the use of HFNC in terms of the rate of ETI (18% vs. 61 %), absolute risk reduction of 43% (95% CI 19% to 61%) with an odds ratio of 0.10. (IC 95% CI 0.22 to 0.42; p = 0.002). Importantly, ICU mortality was lower in the HELMET group 11% vs 39%, absolute risk reduction of 28% (95% CI, 47% to 6%) and an adjusted odds ratio of 0.15 (95% CI, 0.03 to 0.69; p = 0.015). No statistically significant difference was observed in patients with PaCO2 > 35mmHg (46% of the total). See the image below.

The authors studied a composite index: PaO2/(FIO2 x dyspnea score). Patients were stratified into two groups, those with an index > 30, better oxygenation, less dyspneic (55, 50.4%) or < 30 ( 54, 49.6%), with worse oxygenation, and more dyspneic. Only in the group with an index < 30 was there a benefit from the use of HELMET vs. HFNC, especially regarding the ETI rate, 37% vs. 70%, with an absolute risk reduction of 33% (CI 95% CI, 27% at 54 %) and adjusted odds ratio of 0.11 (95% CI, 0.02 to 0.55; P = 0.008).

These results are relevant as they indicate that patients with more physiological repercussions of COVID-19 resulting in worse hypoxemia, dyspnea, and consequent hyperventilation may have more significant benefits from NIV applied with the helmet interface than HFNC.

It also seems plausible that the benefit is more remarkable in cases where the work of breathing and neural command (respiratory drive) are likely to be under significant stress and potentially associated with self-induced lung injury (P-SILI).

The work has limitations because it is a post-hoc analysis, being just a way to generate new hypotheses for future studies. Furthermore, it is not possible to extrapolate these results to the use of HELMET in the form of CPAP. This type of intervention still lacks a comparison with HELMET-NIV (with two pressure levels) and the HFNC.

Check the full-text paper in the link below:

Grieco DL, Menga LS, Cesarano M, Spadaro S, Bitondo MM, Berardi C, Rosà T, Bongiovanni F, Maggiore SM, Antonelli M; COVID-ICU Gemelli Study Group. Phenotypes of Patients with COVID-19 Who Have a Positive Clinical Response to Helmet Noninvasive Ventilation. Am J Respir Crit Care Med. 2022 Feb 1;205(3):360-364.

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