The 6th Congress of Exercise and Sport Sciences

Why Do COPD Patients Get So Breathless Walking Uphill? A Physiological Study

Ronen Reuveny 1,2 Amit Yaniv 2 Einat Kodesh 3 Arie Rotstein 2 Michael Segel 1
1The Pulmonary Institute, Sheba Medical Centre, Ramat Gan, Israel
2The Academic College at Wingate, Netanya, Israel
3Physical Therapy Department, University of Haifa, Haifa, Israel

Background: COPD patients often complain of severe dyspnea when walking uphill, even with a mild incline. We aimed to study the effect of incline on Borg dyspnea score during treadmill walking in COPD patients and healthy controls. We hypothesized that this dyspnea is out of proportion to the increased work necessary to overcome gravity when walking uphill.

Methods: Fourteen (f=4) COPD patients (median FEV1 48% predicted, range 30-73%), and nine (f=2) matched healthy control performed 3 symptom-limited exercise tests on a treadmill, each at a fixed grade: 1%, 2.5% and 4%. Treadmill speed was increased stepwise (3’/stage). Subjects reported dyspnea according to the Borg scale (1-10 points) at each stage. Cardiac, respiratory and gas exchange response were continuously recorded. An inspiratory capacity (IC) maneuver was performed during the last minute of each stage. Peak oxygen consumption (pVO2) was determined for each test. Borg score reported by each subject at a uniform level of oxygen consumption (isoV’O2), corresponding to the lowest pVO2 attained in the 3 tests performed by the subject, was compared across tests by repeated-measure ANOVA post-hoc Bonferroni. Parameter values were linearly interpolated as necessary.

Results: COPD patients were more dyspneic when walking at higher grades, despite correction for level of oxygen consumption: at iso-VO2, dyspnea increased with treadmill grade for 1% vs. 4% grade and 2.5 vs. 4% grade. The median increase in Borg score, at iso-VO2, from 1% to 4% grade, was 4 points (median Borg score was 4 and 8, respectively, p0.01), and from 2.5% to 4% grade, was 3 points (median Borg score was 5 and 8, respectively, p0.01).

Severity of dynamic hyperinflation, at isoVO2, increased with grade, as reflected by a decrease in inspiratory reserve volume (IRV) during exercise from 900 ml (400-1400), at 1% grade to 600 ml (50 -1400) at 4% and from 750 ml (300-1400), at 2.5% grade to 600 ml (50 -1400) at 4%. There was no difference in dyspnea score and IRV with higher grades in the healthy control group.

Conclusions: Walking uphill per se increases breathlessness of COPD patients, even at isoVO2, suggesting that the increased dyspnea cannot be explained simply by the increased work. This finding may be a result of the dynamic hyperinflation, which is worse at steeper inclines. Further studies will be necessary to determine the mechanism of this phenomenon. Possibilities include an effect of posture or of gait, perhaps altering afferent output from leg muscles to the respiratory centers in the brain.









Powered by Eventact EMS