Can COPD patients who hyperinflate during daily life activities be identified by laboratory tests?

BACKGROUND: Identification of patients with chronic obstructive pulmonary disease (COPD) who develop dynamic hyperinflation (DH) during activities in daily life (ADL) is important, because of the association between DH and dyspnea and exercise limitation. OBJECTIVE: We aimed to answer the question whether measurements of DH during metronome-paced tachypnea (MPT) or cardiopulmonary exercise testing (CPET) can be used to identify patients who develop DH during ADL. METHODS: DH was measured by tracking changes in inspiratory capacity during CPET, MPT and ADL. Bland-Altman plots were used to evaluate agreement in DH between methods. With a receiver operating characteristic (ROC) analysis, the overall accuracy of MPT and CPET to identify patients who hyperinflate during ADL was assessed. RESULTS: There are broad limits of agreement in DH between methods. ROC curve analyses showed good overall accuracy of both CPET and MPT to identify patients who hyperinflate during ADL. For CPET, area under the curve (AUC) = 0.956 (95% CI 0.903-1.009). For MPT, AUC = 0.840 (95% CI 0.699-0.981). Sensitivity and specificity to identify patients who hyperinflate during ADL with CPET were 96 and 83%, respectively, and with MPT, they were 89 and 77%, respectively. CONCLUSION: Both CPET and MPT can serve as screening tools to identify patients who are susceptible to developing DH during ADL. In practice, MPT is the most simple and inexpensive surrogate. However, the sensitivity of MPT is not optimal. When DH does not occur during CPET, it is unlikely to occur during ADL.

Physiologic limitations during daily life activities in COPD patients.

INTRODUCTION: Patients with COPD are known to be limited in their performance of activities of daily life (ADL). This observational study aims to investigate the ventilatory and metabolic demand of ADL in home settings of patients and evaluate possible mechanisms involved in physiological limitation during ADL in COPD. METHODS: In their home settings, 21 stable patients with COPD (GOLD II-IV, mean FEV(1) 43% predicted) were asked to perform their most dyspnea causing activities at their usual pace until symptoms discouraged further performance. Ten healthy control subjects, matched for age and gender, performed comparable activities. Ventilatory and metabolic demands of the ADL were studied using a portable breath-by-breath system. RESULTS: Compared with healthy controls, ADL time was shorter in patients (530 +/- 38 s vs. 318 +/- 37 s respectively) and activities resulted in important complaints of dyspnea. Oxygen consumption (V O(2)) during the activities was higher in patients compared to healthy subjects (957 +/- 51 vs. 768 +/- 63 mL/min resp.). Ventilatory demand (V E) for comparable activity (at isoV O(2)) was higher in patients and went together with complaints of dyspnea in patients, but not in healthy subjects. Ventilatory constraints like low ventilatory reserve and inspiratory reserve volume and dynamic hyperinflation occurred in more than 80% of the patients, especially in (very) severe patients. CONCLUSION: Patients with COPD experience limitations in the performance of ADL, which lead to reductions in ADL time and dyspnea complaints. There appears to be an important role for ventilatory limitations, which become more prominent as disease progresses.