Letter:
We read with interest the description by Chase and colleagues of a system to provide an “in series” rather than “in parallel” sharing of a single ventilator between two patients [1]. Their suggestion is that this is a “last resort technique” that may be useful during the COVID-19 pandemic surge. In contradistinction to other “shared ventilation” systems, Chase’s design permits individual adjustments for patients’ compliance and PEEP [2]. However, using the system described by Chase, every second breath is delivered to each patient. This results in an inspiration time limited to less than 50% of the respiratory cycle time, even if the ventilator set expiration time is minimized [3]. Several ventilators further limit inspiratory time to 80% of cycle time, meaning the longest inspiratory time would be an I:E ratio of 1:1.5 [4].
Anzeige
COVID-19 respiratory failure is characterized by severe hypoxemia, often with near normal compliance, and frequently resistant to PEEP and recruitment maneuvers [5]. One additional strategy available to increase oxygenation is to increase inspiratory time, which allows more distribution of fresh gas to slow filling alveoli and raises the mean alveolar pressure. The Chase apparatus’s inability to provide reverse ratio or even 1:1 ventilation is an important limitation in severe hypoxemia respiratory failure that may reduce its utility in a COVID-19 crisis.
Acknowledgements
Nil
Ethics approval and consent to participate
Not applicable
Consent for publication
Not applicable
Anzeige
Competing interests
The authors have no competing interests.
Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.