The confounding effects of thoracic gas compression on measurement of acute bronchodilator response

Amir Sharafkhaneh, Tony G. Babb, Todd M. Officer, Nicholas A. Hanania, Hossein Sharafkhaneh, Aladin M. Boriek

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Rationale: Improvement in FEV1 is a main endpoint in clinical trials assessing the efficacy of bronchodilators. However, the effect of bronchodilators on maximal expiratory flow may be confounded by thoracic gas compression (TGC). Objective: To determine whether TGC confounds effect of albuterol on FEV1. Methods: We evaluated the response to albuterol inhalation in 10 healthy subjects, 9 subjects with asthma, and 15 subjects with chronic obstructive pulmonary disease (COPD) with mean (SD) age in years of 38 (SD, 11), 45 (SD, 11), and 64 (SD, 8), respectively. Lung mechanics were measured at baseline and 20 minutes after inhalation of 180 μg of albuterol. We then applied a novel method to calculate FEV1 corrected for the effect of TGC (NFEV1). Results: Prior to albuterol administration, NFEV1 was significantly higher than FEV1. However, post-albuterol inhalation, FEV1 increased more than NFEV1 because of reduced TGC. In multiple regression analysis, the changes in TGC, inspiratory lung resistance, and ratio of residual volume to total lung capacity postalbuterol predicted more than 75% of FEV1 improvement in patients with COPD. Conclusion: Improvements in FEV1 after albuterol in patients with COPD are due to reduction of lung resistance, hyperinflation, and TGC. The latter is negligible during tidal breathing. Thus, although reduction of lung resistance and hyperinflation may result in improved dyspnea with a bronchodilator, the contribution of TGC reduction to improvement of FEV1 may not exert any meaningful clinical effect during tidal breathing. This fact has to be taken into consideration when assessing the efficacy of new bronchodilators.

Original languageEnglish (US)
Pages (from-to)330-335
Number of pages6
JournalAmerican Journal of Respiratory and Critical Care Medicine
Volume175
Issue number4
DOIs
StatePublished - Feb 15 2007

Fingerprint

Bronchodilator Agents
Albuterol
Thorax
Gases
Chronic Obstructive Pulmonary Disease
Inhalation
Lung
Respiration
Total Lung Capacity
Residual Volume
Mechanics
Dyspnea
Healthy Volunteers
Asthma
Regression Analysis
Clinical Trials

Keywords

  • Albuterol
  • Asthma
  • Chronic obstructive pulmonary disease
  • FEV
  • Lung mechanics

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

Cite this

The confounding effects of thoracic gas compression on measurement of acute bronchodilator response. / Sharafkhaneh, Amir; Babb, Tony G.; Officer, Todd M.; Hanania, Nicholas A.; Sharafkhaneh, Hossein; Boriek, Aladin M.

In: American Journal of Respiratory and Critical Care Medicine, Vol. 175, No. 4, 15.02.2007, p. 330-335.

Research output: Contribution to journalArticle

Sharafkhaneh, Amir ; Babb, Tony G. ; Officer, Todd M. ; Hanania, Nicholas A. ; Sharafkhaneh, Hossein ; Boriek, Aladin M. / The confounding effects of thoracic gas compression on measurement of acute bronchodilator response. In: American Journal of Respiratory and Critical Care Medicine. 2007 ; Vol. 175, No. 4. pp. 330-335.
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abstract = "Rationale: Improvement in FEV1 is a main endpoint in clinical trials assessing the efficacy of bronchodilators. However, the effect of bronchodilators on maximal expiratory flow may be confounded by thoracic gas compression (TGC). Objective: To determine whether TGC confounds effect of albuterol on FEV1. Methods: We evaluated the response to albuterol inhalation in 10 healthy subjects, 9 subjects with asthma, and 15 subjects with chronic obstructive pulmonary disease (COPD) with mean (SD) age in years of 38 (SD, 11), 45 (SD, 11), and 64 (SD, 8), respectively. Lung mechanics were measured at baseline and 20 minutes after inhalation of 180 μg of albuterol. We then applied a novel method to calculate FEV1 corrected for the effect of TGC (NFEV1). Results: Prior to albuterol administration, NFEV1 was significantly higher than FEV1. However, post-albuterol inhalation, FEV1 increased more than NFEV1 because of reduced TGC. In multiple regression analysis, the changes in TGC, inspiratory lung resistance, and ratio of residual volume to total lung capacity postalbuterol predicted more than 75{\%} of FEV1 improvement in patients with COPD. Conclusion: Improvements in FEV1 after albuterol in patients with COPD are due to reduction of lung resistance, hyperinflation, and TGC. The latter is negligible during tidal breathing. Thus, although reduction of lung resistance and hyperinflation may result in improved dyspnea with a bronchodilator, the contribution of TGC reduction to improvement of FEV1 may not exert any meaningful clinical effect during tidal breathing. This fact has to be taken into consideration when assessing the efficacy of new bronchodilators.",
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N2 - Rationale: Improvement in FEV1 is a main endpoint in clinical trials assessing the efficacy of bronchodilators. However, the effect of bronchodilators on maximal expiratory flow may be confounded by thoracic gas compression (TGC). Objective: To determine whether TGC confounds effect of albuterol on FEV1. Methods: We evaluated the response to albuterol inhalation in 10 healthy subjects, 9 subjects with asthma, and 15 subjects with chronic obstructive pulmonary disease (COPD) with mean (SD) age in years of 38 (SD, 11), 45 (SD, 11), and 64 (SD, 8), respectively. Lung mechanics were measured at baseline and 20 minutes after inhalation of 180 μg of albuterol. We then applied a novel method to calculate FEV1 corrected for the effect of TGC (NFEV1). Results: Prior to albuterol administration, NFEV1 was significantly higher than FEV1. However, post-albuterol inhalation, FEV1 increased more than NFEV1 because of reduced TGC. In multiple regression analysis, the changes in TGC, inspiratory lung resistance, and ratio of residual volume to total lung capacity postalbuterol predicted more than 75% of FEV1 improvement in patients with COPD. Conclusion: Improvements in FEV1 after albuterol in patients with COPD are due to reduction of lung resistance, hyperinflation, and TGC. The latter is negligible during tidal breathing. Thus, although reduction of lung resistance and hyperinflation may result in improved dyspnea with a bronchodilator, the contribution of TGC reduction to improvement of FEV1 may not exert any meaningful clinical effect during tidal breathing. This fact has to be taken into consideration when assessing the efficacy of new bronchodilators.

AB - Rationale: Improvement in FEV1 is a main endpoint in clinical trials assessing the efficacy of bronchodilators. However, the effect of bronchodilators on maximal expiratory flow may be confounded by thoracic gas compression (TGC). Objective: To determine whether TGC confounds effect of albuterol on FEV1. Methods: We evaluated the response to albuterol inhalation in 10 healthy subjects, 9 subjects with asthma, and 15 subjects with chronic obstructive pulmonary disease (COPD) with mean (SD) age in years of 38 (SD, 11), 45 (SD, 11), and 64 (SD, 8), respectively. Lung mechanics were measured at baseline and 20 minutes after inhalation of 180 μg of albuterol. We then applied a novel method to calculate FEV1 corrected for the effect of TGC (NFEV1). Results: Prior to albuterol administration, NFEV1 was significantly higher than FEV1. However, post-albuterol inhalation, FEV1 increased more than NFEV1 because of reduced TGC. In multiple regression analysis, the changes in TGC, inspiratory lung resistance, and ratio of residual volume to total lung capacity postalbuterol predicted more than 75% of FEV1 improvement in patients with COPD. Conclusion: Improvements in FEV1 after albuterol in patients with COPD are due to reduction of lung resistance, hyperinflation, and TGC. The latter is negligible during tidal breathing. Thus, although reduction of lung resistance and hyperinflation may result in improved dyspnea with a bronchodilator, the contribution of TGC reduction to improvement of FEV1 may not exert any meaningful clinical effect during tidal breathing. This fact has to be taken into consideration when assessing the efficacy of new bronchodilators.

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