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Simplified Detection of Dynamic Hyperinflation^*

^* From the Pulmonary Division (Dr. Gelb), Department of Medicine Lakewood Regional Medical Center, Lakewood, CA; Faculty of Medicine (Drs. Gutierrez and Zamel), University of Toronto, Toronto, ON, Canada; Department of Clinical Investigation and Pulmonary Critical Care Medicine (Dr. Weisman), William Beaumont Army Medical Center, El Paso, TX; and independent contractors (Mr. Newsom and Ms. Taylor), Lakewood, CA.

Correspondence to: Arthur F. Gelb, MD, FCCP, 3650 E South St, Suite 308, Lakewood, CA 90712; e-mail: afgelb{at}msn.com

Study objective: To detect dynamic hyperinflation by comparing reduction in inspiratory capacity (IC) during both paced hyperventilation and cycle ergometry in patients with moderate-to-severe COPD, studied before and after acute bronchodilation.

Methods: IC and FEV₁ were measured before and after metronome-paced hyperventilation at twice the resting respiratory rate for 20 s in 16 patients with COPD before and after 54 µg aerosolized ipratropium bromide (IB). We also studied the same 16 patients before and after administration of 54 µg aerosolized IB during symptom-limited incremental cycle ergometry when the final respiratory rate was also twice the resting rate.

Results: Resting IC was 2.23 ± 0.53 L (mean ± SD), and the mean decrease in IC from baseline was 0.36 ± 0.25 L after exercise (p < 0.001), and not significantly different (p = 0.64) from mean decrease in IC of 0.40 ± 0.29 L following hyperventilation. Results following hyperventilation and exercise were similar after bronchodilator. The mean difference for decrease of IC between hyperventilation and exercise was 0.138 L (95% confidence interval, – 0.347 to 0.622; r = 0.66, p = 0.006). The decrease in FEV₁ was 0.01 ± 0.13 L after exercise and 0.06 ± 0.18 L after hyperventilation. Separately, baseline and peak end-expiratory and end-inspiratory lung volumes were similar with hyperventilation vs exercise both before and after bronchodilator.

Conclusion: Both metronome-paced hyperventilation and incremental cycle ergometry, when resting respiratory rate was doubled, provoked similar significant decrease in IC, even after administration of 54 µg aerosolized IB. The noninvasive simplicity of hyperventilation for 20 s provides a clinically useful screening surrogate to monitor changes in IC following exercise.

Key Words: COPD • dynamic hyperinflation • exercise • hyperventilation • lung function

This article has been cited by other articles:

				A. F. Gelb, C. F. Taylor, P. A. McClean, C. M. Shinar, M. T. Rodrigues, C. A. Gutierrez, K. R. Chapman, and N. Zamel Tiotropium and Simplified Detection of Dynamic Hyperinflation Chest, March 1, 2007; 131(3): 690 - 695. [Abstract] [Full Text] [PDF]