Chest
Volume 126, Issue 6, December 2004, Pages 1855-1860
Journal home page for Chest

Clinical Investigations
PULMONARY FUNCTION TRAITS
Simplified Detection of Dynamic Hyperinflation

https://doi.org/10.1378/chest.126.6.1855Get rights and content

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.

Section snippets

Materials and Methods

We selected 16 patients with smoking history > 20 pack-years with documented moderate-to-severe COPD,10 who were in clinically stable condition for at least 6 weeks prior to the present study and were not receiving oxygen. A history of wheezing and/or responsiveness to aerosolized albuterol were not specific inclusion criteria. Patients were instructed to continue all their usual medications, but to withhold short-acting β2-agonists and/or aerosolized IB for 6 h and long-acting β2-agonists for

Results

In the 21 younger healthy volunteers (13 women) aged 37 ≤ 13 years, baseline IC was 2.98 ≤ 0.73 L.9 After 20 s of metronome-paced hyperventilation at twice the resting respiratory rate, IC was 2.90 ≤ 0.70 L. The mean decrease in IC was 2%. In the eight older healthy volunteers (five women) aged 60 ≤ 2 years, baseline IC was 2.58 ≤ 0.68 L. Following 20 s of metronome-paced hyperventilation at twice the resting respiratory rate, IC was 2.56 ≤ 0.71 L. The mean decrease in IC was 0.8%. In both

Discussion

The present study in 16 patients with COPD with moderate-to-severe expiratory airflow limitation demonstrated the provocative ability of metronome-paced hyperventilation at twice the resting respiratory rate for 20 s to induce a significant decrease in IC. This was similar as a group to the decrease in IC following symptom-limited incremental cycle ergometry when the baseline respiratory rate was also doubled. The noninvasive simplicity of hyperventilation for 20 s provided a clinically useful

ACKNOWLEDGMENT

The authors thank Christy Kirkendall for patient coordination, Aia White-Podue for manuscript preparation, Chris M. Shinar, PharmD, for computer assistance, and Michelle Curry for patient scheduling.

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