Application of the COPD Assessment Test (CAT) to Patients with Interstitial Lung Disease

The COPD Assessment Test was recently developed to assess health status in patients with COPD. However, little was known about its application to patients with interstitial lung disease, so we examined the relationship between the COPD Assessment Test score and respiratory impairment including the clinical picture in subjects with interstitial lung disease. Data were collected retrospectively from 52 consecutive subjects with interstitial lung disease on admission to our facility. All subjects completed the COPD Assessment Test, in which a higher score represented a worse health status. They were also assessed by pulmonary function test, SpO2 during 6-min walk test, and arterial blood gases. The COPD Assessment Test score was negatively correlated with the percentage of predicted forced vital capacity, forced expiratory volume in 1 second, total lung capacity, diffusion capacity of the lung for carbon monoxide, and PaO2 (p = 0.0005, 0.005, 0.0002, 0.0005, and 0.002, respectively). Breathlessness was detected as the high scoring item, while phlegm and sleep were the last affected items. The COPD Assessment Test score was higher in subjects with oxygen desaturation in SpO2 (≥4%) during 6-min walk test (p = 0.0001) and in subjects on home oxygen therapy (p = 0.0007). More than 75% of subjects with oxygen desaturation during walking were classified into a medium or severer impact level of the COPD Assessment Test score, and subjects on home oxygen therapy were classified into a high or severer impact level. PaCO2 in room air and SpO2 at rest did not correlate with the COPD Assessment Test score. The reliability of items in the COPD Assessment Test was 0.87 by Cronbach’s α coefficient. Our results suggest that the COPD Assessment Test may be a candidate for evaluating the health status and impact of disease on patients with interstitial lung disease.

Pulmonary rehabilitation outcome of exercise-induced oxygen desaturation in systemic sclerosis with interstitial lung disease

While exercise capacity in systemic sclerosis with interstitial lung disease could be improved by exercise training, the training outcome of exercise-induced oxygen desaturation has not been examined. The aim of this study was to investigate the effect of pulmonary rehabilitation on exercise-induced oxygen desaturation during the six-minute walk test and to detect the factors affecting outcome retrospectively. Patients showing impaired exercise capacity (≤80% of predicted) and/or exercise-induced oxygen desaturation (≤-4% in SpO2) at the end of the six-minute walk test underwent routine walking exercise. Sixteen patients with stable systemic sclerosis completed exercise training for 55 days on average. The mean six-minute walk distance improved from 467 m to 502 m (P = 0.0012). The improvement in distance was negatively related to baseline distance (R2 = 0.28, P = 0.037), but was not related to parameters from pulmonary function tests and echocardiograms. Oxygen saturation was normal at rest, but was decreased in fifteen patients at the end of the test. Exercise-induced oxygen desaturation was positively related to the diffusion capacity of the lungs for carbon monoxide at baseline (R2 = 0.33, P = 0.026);however, it was not related to any cardiopulmonary parameters after intervention. Seven of sixteen patients ameliorated exercise-induced oxygen desaturation or showed no oxygen desaturation after exercise training, while others deteriorated. No cardiopulmonary parameters affected the training outcome of exercise-induced oxygen desaturation. Exercise train ing was beneficial in improving exercise tolerance, but training effects and mechanisms on exercise-induced oxygen desaturation still need more studies to be explained.