Predictors of Morphine Efficacy for Dyspnea in Inpatients with Chronic Obstructive Pulmonary Disease: A Secondary Analysis of JORTC-PAL 07

Objective: This study aimed to explore the predictors of morphine efficacy in the alleviation of dyspnea in COPD. Background: Dyspnea is prevalent in patients with chronic obstructive pulmonary disease (COPD) and often persists despite conventional treatment. Methods: A secondary analysis of a multi-institutional prospective before-after study was conducted focusing on morphine use for alleviating dyspnea in COPD patients. Subjects included COPD patients with dyspnea at seven hospitals in Japan. Patients received 12 mg/day of oral morphine (or 8 mg/day if they had low body weight or renal impairment). Univariate and multivariate logistic regression analyses were performed with numerical rating scale (NRS) score of the current dyspnea intensity in the evening of day 0, Eastern Cooperative Oncology Group Performance Status (ECOG PS; ≤2 or ≥3), age, and partial arterial pressure of carbon dioxide (PaCO2) as independent factors; an improvement of ≥1 in the evening NRS score of dyspnea from day 0 to 2 was the dependent factor. Results: Thirty-five patients were enrolled in this study between October 2014 and January 2018. Excluding one patient who did not receive the treatment, data from 34 patients were analyzed. In the multivariate analysis, lower PaCO2 was significantly associated with morphine efficacy for alleviating dyspnea (odds ratio [OR] 0.862, 95% confidence interval [CI] 0.747-0.994), whereas the NRS of dyspnea intensity on day 0 (OR 1.426, 95% CI 0.836-2.433), ECOG PS (OR 4.561, 95% CI 0.477-43.565), and patients' age (OR 0.986, 95% CI 0.874-1.114) were not. Discussion: Morphine can potentially alleviate dyspnea in COPD patients with lower PaCO2. Trial registration: UMIN000015288 (http://www.umin.ac.jp/ctr/index.htm)