Chest
Volume 139, Issue 5, May 2011, Pages 1018-1024
Journal home page for Chest

Original Research
Critical Care
The Effect of Supplemental Oxygen on Hypercapnia in Subjects With Obesity-Associated Hypoventilation: A Randomized, Crossover, Clinical Study

https://doi.org/10.1378/chest.10-1280Get rights and content

Background

It is unknown whether oxygen therapy causes worsening hypercapnia in patients with obesity-associated hypoventilation (OAH), similar to the response observed in COPD. The objectives of this study were to investigate whether breathing 100% oxygen results in an increase in hypercapnia in patients with OAH and the mechanisms of any effect.

Methods

In this double-blind, randomized, controlled, crossover trial, 24 outpatients with newly diagnosed OAH inhaled 100% oxygen or room air for 20 min on 2 separate days. Transcutaneous CO2 tension (Ptco2), minute ventilation, and volume of dead space to tidal volume ratio were measured at baseline and at 20 min. A mixed linear model was used to determine differences between the two treatments.

Results

The study was terminated in three subjects breathing 100% oxygen due to a Ptco2 increase ≥ 10 mm Hg, which occurred after 10:35, 13:20, and 15:51 min. Ptco2 increased by 5.0 mm Hg (95% CI, 3.1–6.8; P < .001) with oxygen compared with room air. Minute ventilation decreased by 1.4 L/min (95% CI, 0.11–2.6 L/min; P = .03), and volume of dead space to tidal volume ratio increased by 0.067 (95% CI, 0.035–0.10; P < .001) with oxygen compared with room air.

Conclusions

Breathing 100% oxygen causes worsening hypercapnia in stable patients with OAH.

Trial registry

Australia New Zealand Clinical Trials Registry; No.: ACTRN 12608000592347; URL: www.anzctr.org.au.

Section snippets

Subjects

Patients with newly diagnosed OAH were approached to participate in the study. To be included in the study, subjects had to be obese (BMI > 30 kg/m2) and have evidence of daytime hypercapnia (transcutaneous CO2 tension [Ptco2] ≥ 45 mm Hg). Patients were excluded if they had COPD (defined by a postbronchodilator FEV1/FVC ratio < 0.7, FEV1 < 80% predicted, and > 10 pack-year smoking history); had another disorder associated with hypercapnic respiratory failure, such as neuromuscular disease; or

Characteristics of Subjects

A total of 76 patients with obesity (mean BMI, 47.6 kg/m2) without a history of COPD were screened for evidence of daytime hypercapnia (Fig 1). Of these, 25 met the inclusion criteria, and 24 consented to take part in the study. As a result, 24 subjects were randomized; one subject did not attend for the second test. The study took place between June 2008 and May 2009.

Table 1 shows the baseline characteristics of the subjects included in the study. The 24 subjects were morbidly obese with a

Discussion

This double-blind, randomized, crossover study has demonstrated that breathing 100% oxygen causes worsening hypercapnia in subjects with OAH in a stable condition. After 20 min breathing 100% oxygen, the Ptco2 increased by a mean of 5 mm Hg, with three of 24 subjects withdrawn before completion of the study while breathing oxygen because of an increase in Ptco2 of ≥ 10 mm Hg. This finding indicates that patients with stable OAH are at risk for worsening hypercapnia with high-flow uncontrolled

Conclusions

To the best of our knowledge, this investigation is the first double-blind, randomized, controlled study of high-concentration oxygen therapy in subjects with OAH. It has demonstrated that breathing 100% oxygen leads to worsening hypercapnia in subjects with OAH and that the magnitude and speed of the effect may be striking. This physiologic response is due to a reduction in MV, resulting in alveolar hypoventilation and an associated increase in Vds/Vt. We suggest that in patients with morbid

Acknowledgments

Author contributions: Dr Wijesinghe had full access to all of the data in the study and takes full responsibility for their integrity and the accuracy of the data analysis, including any adverse effects.

Dr Wijesinghe: contributed to planning the study, conducting the testing, and preparing the manuscript.

Mr Williams: contributed to conducting the testing and preparing the manuscript.

Dr Perrin: contributed to planning the study, conducting the testing, and preparing the manuscript.

Dr Weatherall:

References (34)

  • World Health Organization

    Global strategy on diet, physical activity and health. World Health Organization Web site

  • B Mokhlesi et al.

    Assessment and management of patients with obesity hypoventilation syndrome

    Proc Am Thorac Soc

    (2008)
  • F Crummy et al.

    Obesity and the lung: 2. Obesity and sleep-disordered breathing

    Thorax

    (2008)
  • JK Quint et al.

    Previously undiagnosed obesity hypoventilation syndrome

    Thorax

    (2007)
  • M Aubier et al.

    Effects of the administration of O2 on ventilation and blood gases in patients with chronic obstructive pulmonary disease during acute respiratory failure

    Am Rev Respir Dis

    (1980)
  • FJ Prime et al.

    The respiratory response to CO2 in emphysema

    Clin Sci (Lond)

    (1954)
  • TD Robinson et al.

    The role of hypoventilation and ventilation-perfusion redistribution in oxygen-induced hypercapnia during acute exacerbations of chronic obstructive pulmonary disease

    Am J Respir Crit Care Med

    (2000)
  • Cited by (94)

    • Evolution of obesity hypoventilation syndrome

      2020, Obesity Hypoventilation Syndrome: From Physiologic Principles to Clinical Practice
    • The effects of weight loss, tracheostomy, and medication on obesity hypoventilation syndrome

      2020, Obesity Hypoventilation Syndrome: From Physiologic Principles to Clinical Practice
    View all citing articles on Scopus

    Funding/Support: Dr Wijesinghe is a Wellington Hospitals and Health Foundation Research Fellow, and Dr Perrin is a Health Research Council of New Zealand Training Fellow.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

    View full text