The Reduced Sensation of Dyspnea During Exercise by Inhaled Oxitropium Bromide in Severe COPD Patients

Abstract

To the Editor: We read, with great interest, the article by Ikeda and coworkers published in the December 1994 issue (CHEST 1994; 106:1740–45) concerning the effects of oxitropium bromide (OTB) on exercise capacity in severe COPD patients. The authors showed that the OTB increased the exercise capacity in severe COPD patients. However, the improvement of exercise capacity was obviously small as previously reported.1Hay JG Stone P Carter J et al.Bronchodilator reversibility, exercise performance and breathlessness in stable chronic obstructive pulmonaiy disease.Eur Respir J. 1992; 5: 659-664PubMed Google Scholar,2Teramoto S Fukuchi Y Orimo H Effects of inhaled anticholinergic drug on dyspnea and gas exchange during exercise in chronic obstructive pulmonary disease.Chest. 1993; 103: 1774-1782Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar The exercise capacity can be expressed by several parameters including maximal work load, maximal minute ventilation ( V˙E), and maximal oxygen uptake ( V˙O2). Theoretically, there are linear relationships between these parameters. However, in the current study, the maximal work rate may not be an appropriate indicator of the exercise capacity. The coefficient of variation of the mean value of work rate/ V˙O2 is 3 to 4 fold greater than that of the ventilatory ratio ( V˙E/V˙O2) (Table 1).Table 1Coefficient of Variation of the Mean Value of Work/ V˙O2 and Standardized Dyspnea ScorePlaceboOTBValuesBeforeAfterBeforeAfterCoefficient of VariationWork rate/ V˙O2 (W/L/min)124.6115.1114.0111.84.9%Work rate/ V˙E (W/L/min)2.592.382.432.344.5% V˙E/V˙O248.148.447.047.81.3%BS7.47.47.37.1BS/work rate (BS/W)0.0840.0850.0850.075BS/ V˙O2 (BS/L/min)10.59.79.78.4 Open table in a new tab Another problem is that an increase rate of work load (20 W/min) is too hard to perform especially in patients with severe COPD. The placebo data suggest that the first exercise testing cannot be adapted to the patients. In our experience, the maximal V˙O2 in patients with severe COPD (FEV1<0.8 L) could not reach the same level of first exercise testing in the second testing 90 min after the first exercise.2Teramoto S Fukuchi Y Orimo H Effects of inhaled anticholinergic drug on dyspnea and gas exchange during exercise in chronic obstructive pulmonary disease.Chest. 1993; 103: 1774-1782Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar Compared with the changes in V˙O2 after placebo administration (about 54 mL/min), the absolute value of the improvement of exercise capacity after OTB inhalation (about 86 mL/min) is very small. The authors' conclusion may be exaggerated. The most important finding of this study may confirm the beneficial effects of inhaled anticholinergic drug on dyspnea during exercise, which we have reported.2Teramoto S Fukuchi Y Orimo H Effects of inhaled anticholinergic drug on dyspnea and gas exchange during exercise in chronic obstructive pulmonary disease.Chest. 1993; 103: 1774-1782Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar Although the authors did not mention the improvement of dyspnea after the OTB inhalation, the results from the authors may indicate the reduced sensation of dyspnea if the data are appropriately analyzed.3Teramoto S Fukuchi Y Nagase T et al.Quantitative assessment of dyspnea during exercise Before and after bullectomy for giant bulla.Chest. 1992; 102: 1362-1366Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar As shown in the table, maximal score of Borg scale (BS) was not different between placebo and OTB inhalation, but the standardized dyspnea score (BS/work rate or BS/ V˙O2) after OTB inhalation was about 10% reduction of that after placebo inhalation. Although the calculations do not represent the accurate value reflecting individual measurements, the obtained data are consistent with our previous findings.2Teramoto S Fukuchi Y Orimo H Effects of inhaled anticholinergic drug on dyspnea and gas exchange during exercise in chronic obstructive pulmonary disease.Chest. 1993; 103: 1774-1782Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar We basically agree with the authors that OTB can improve the exercise capacity in stable COPD patients. We also recognize that even a small increase of exercise capacity is important for improvements in physiologic and metabolic aspects in the patients. However, the reason why we administer the OTB to COPD patients is a reduction of dyspnea during exercise rather than a small increase of work rate, because the reduction of dyspnea directly contributes to a better quality of daily life. The Reduced Sensation of Dyspnea During Exercise by Inhaled Oxitropium Bromide in Severe COPD PatientsCHESTVol. 108Issue 5PreviewWe are pleased to respond to the letter from Drs. Teramoto and Fukuchi. The first issue is that the “maximum work rate” in our study is not an appropriate indicator of exercise capacity, based on the fact that the greater variability of the [maximal work rate (Wmax)/maximal oxygen uptake ( V ˙ O 2 max)] as compared with the [maximal minute ventilation/ V ˙ O 2 max]. A possible explanation for this variability may be that the V ˙ O 2 does not necessarily increase linearly as the work rate increases, especially after the work rate reaches a level that approaches the anaerobic threshold. Full-Text PDF