Newly Published
Critical Care Medicine  |   July 2020
Prevalence of Complete Airway Closure According to Body Mass Index in Acute Respiratory Distress Syndrome: Pooled Cohort Analysis
Author Notes
  • From the Interdepartmental Division of Critical Care Medicine, University of Toronto, St. Michael’s Hospital, Toronto, Ontario, Canada (R.C., L.C., L.B.); Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada (R.C., L.C., L.B.); Medical Intensive Care Unit, University Hospital of Poitiers, Poitiers, France (R.C.); INSERM CIC 1402, ALIVE group, University of Poitiers, Poitiers, France (R.C.); Medical Intensive Care Unit, European Hospital Georges Pompidou, Greater Paris Public Hospitals (Assistance Publique-Hoôpitaux de Paris), Paris, France (D.V., N.A., R.Y., C.B., A.C.-C., A.L., E.G., J.-L.D.); INSERM U970 - Cardiovascular Research Center of Paris, Paris, France (N.A.); and INSERM, UMR_S1140: Therapeutic Innovations in Hemostasis, University of Pharmaceutical and Biological Sciences, Paris Descartes University, Paris, France (J.-L.D.).
  • Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).
    Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).×
  • Some of the data from this manuscript have been presented at the European Society of Intensive Care Medicines Congress on October 23, 2018 in Paris, France and October 1, 2019 in Berlin, Germany, and at the French Intensive Care Society Congress in February 5, 2020 in Paris, France.
    Some of the data from this manuscript have been presented at the European Society of Intensive Care Medicines Congress on October 23, 2018 in Paris, France and October 1, 2019 in Berlin, Germany, and at the French Intensive Care Society Congress in February 5, 2020 in Paris, France.×
  • Submitted for publication August 29, 2019. Accepted for publication May 29, 2020.
    Submitted for publication August 29, 2019. Accepted for publication May 29, 2020.×
  • Correspondence: Address correspondence to Dr. Coudroy: Médecine Intensive et Réanimation, CHU de Poitiers, 2 rue de la Milétrie, 86021 Poitiers, France. r.coudroy@yahoo.fr. Anesthesiology’s articles are made freely accessible to all readers on www.anesthesiology.org, for personal use only, 6 months from the cover date of the issue.
Article Information
Critical Care Medicine / Airway Management / Critical Care / Respiratory System / Technology / Equipment / Monitoring
Critical Care Medicine   |   July 2020
Prevalence of Complete Airway Closure According to Body Mass Index in Acute Respiratory Distress Syndrome: Pooled Cohort Analysis
Anesthesiology Newly Published on July 14, 2020. doi:https://doi.org/10.1097/ALN.0000000000003444
Anesthesiology Newly Published on July 14, 2020. doi:https://doi.org/10.1097/ALN.0000000000003444
Abstract

Background: Complete airway closure during expiration may underestimate alveolar pressure. It has been reported in cases of acute respiratory distress syndrome (ARDS), as well as in morbidly obese patients with healthy lungs. The authors hypothesized that complete airway closure was highly prevalent in obese ARDS and influenced the calculation of respiratory mechanics.

Methods: In a post hoc pooled analysis of two cohorts, ARDS patients were classified according to body mass index (BMI) terciles. Low-flow inflation pressure–volume curve and partitioned respiratory mechanics using esophageal manometry were recorded. The authors’ primary aim was to compare the prevalence of complete airway closure according to BMI terciles. Secondary aims were to compare (1) respiratory system mechanics considering or not considering complete airway closure in their calculation, and (2) and partitioned respiratory mechanics according to BMI.

Results: Among the 51 patients analyzed, BMI was less than 30 kg/m2 in 18, from 30 to less than 40 in 16, and greater than or equal to 40 in 17. Prevalence of complete airway closure was 41% overall (95% CI, 28 to 55; 21 of 51 patients), and was lower in the lowest (22% [3 to 41]; 4 of 18 patients) than in the highest BMI tercile (65% [42 to 87]; 11 of 17 patients). Driving pressure and elastances of the respiratory system and of the lung were higher when complete airway closure was not taken into account in their calculation. End-expiratory esophageal pressure (ρ = 0.69 [95% CI, 0.48 to 0.82]; P < 0.001), but not chest wall elastance, was associated with BMI, whereas elastance of the lung was negatively correlated with BMI (ρ = −0.27 [95% CI, −0.56 to −0.10]; P = 0.014).

Conclusions: Prevalence of complete airway closure was high in ARDS and should be taken into account when calculating respiratory mechanics, especially in the most morbidly obese patients.

Editor’s Perspective:

What We Already Know about This Topic:

  • Plateau and driving pressures have been shown to correlate with mortality in adult respiratory distress syndrome (ARDS). However, these static airway pressures may not always accurately reflect alveolar pressure.

  • It has recently been recognized that in ARDS, airway closure may occur while some alveoli are still inflated. This may result in a biased estimate of mean alveolar pressure.

  • Complete airway closure can only be measured by the inflection point on the initial portion of a low-flow inflation pressure–volume or pressure–time curve with the absence of cardiac oscillations and very low compliance, most likely in the terminal bronchioles.

  • In 25 to 33% of patients with ARDS, airway opening pressure (the inflection point value) is greater than the total positive end-expiratory pressure measured by an end-expiratory maneuver.

What This Article Tells Us That Is New:

  • In a post hoc analysis of two cohort studies of respiratory mechanics in ARDS, the authors compared the prevalence of complete airway closure stratified by body mass index and its effects on respiratory mechanics.

  • Complete airway closure was present in 41% of patients, increasing with body mass index tercile (65% in the highest).

  • Driving pressure and respiratory system elastances (lung, chest wall) were higher when complete airway closure was not adjusted for.