Impact of adherence to long-term oxygen therapy on patients with COPD and exertional hypoxemia followed for one year

J Bras Pneumol. 2018;44(5):390-397 http://dx.doi.org/10.1590/S1806-37562017000000019 ORIGINAL ARTICLE Impact of adherence to long-term oxygen therapy on patients with COPD and exertional hypoxemia followed for one year Carolina Bonfanti Mesquita1,a, Caroline Knaut1,b, Laura Miranda de Oliveira Caram1,c, Renata Ferrari1,d, Silmeia Garcia Zanati Bazan2,e, Irma Godoy1,f, Suzana Erico Tanni3,g 1. Disciplina de Pneumologia, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista – UNESP – Botucatu (SP) Brasil. 2. Disciplina de Cardiologia, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista – UNESP – Botucatu (SP) Brasil. 3. Disciplina de Clínica Médica, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista – UNESP – Botucatu (SP) Brasil. a. http://orcid.org/0000-0002-0156-7004 http://orcid.org/0000-0002-9005-818X b. http://orcid.org/0000-0002-5863-2006 c. http://orcid.org/0000-0002-6740-5278 d. http://orcid.org/0000-0002-0607-8189 e. http://orcid.org/0000-0002-6588-5626 f. http://orcid.org/0000-0002-2587-2759 g. Submitted: 30 January 2017. Accepted: 14 January 2018. Study carried out in the Disciplina de Pneumologia, Faculdade de Medicina de Botucatu, Universidade Estadual Paulista – UNESP – Botucatu (SP) Brasil. ABSTRACT Objective: To determine the impact of adherence to long-term oxygen therapy (LTOT) on quality of life, dyspnea, and exercise capacity in patients with COPD and exertional hypoxemia followed for one year. Methods: Patients experiencing severe hypoxemia during a six-minute walk test (6MWT) performed while breathing room air but not at rest were included in the study. At baseline and after one year of follow-up, all patients were assessed for comorbidities, body composition, SpO2, and dyspnea, as well as for anxiety and depression, having also undergone spirometry, arterial blood gas analysis, and the 6MWT with supplemental oxygen. The Saint George’s Respiratory Questionnaire (SGRQ) was used in order to assess quality of life, and the Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity (BODE) index was calculated. The frequency of exacerbations and the mortality rate were noted. Treatment nonadherence was defined as LTOT use for < 12 h per day or no LTOT use during exercise. Results: A total of 60 patients with COPD and exertional hypoxemia were included in the study. Of those, 10 died and 11 experienced severe hypoxemia during follow-up, 39 patients therefore being included in the final analysis. Of those, only 18 (46.1%) were adherent to LTOT, showing better SGRQ scores, higher SpO2 values, and lower PaCO2 values than did nonadherent patients. In all patients, SaO2, the six-minute walk distance, and the BODE index worsened after one year. There were no differences between the proportions of adherence to LTOT at 3 and 12 months of follow-up. Conclusions: Quality of life appears to be lower in patients with COPD and exertional hypoxemia who do not adhere to LTOT than in those who do. In addition, LTOT appears to have a beneficial effect on COPD symptoms (as assessed by SGRQ scores). (Brazilian Registry of Clinical Trials – ReBEC; identification number RBR-9b4v63 [http:// www.ensaiosclinicos.gov.br]) Keywords: Respiratory insufficiency; Pulmonary disease, chronic obstructive; Patient compliance; Hypoxia; Oxygen inhalation therapy. INTRODUCTION Patients with COPD constitute the largest homogeneous group of patients who have arterial hypoxemia,(1,2) accounting for 67.8-81.6% of all patients on long-term oxygen therapy (LTOT).(3) The use of LTOT improves quality of life and respiratory symptoms, as well as reducing the risk of mortality.(4,5) In some patients, however, hypoxemia occurs only during activities of daily living. (6) The mechanisms involved in exertional hypoxemia are associated with ventilation/perfusion mismatch, decreased diffusion capacity, and increased pulmonary shunt.(6) As a result, exercise tolerance and quality of life are reduced in such patients.(6) The effectiveness of LTOT in patients with exertional hypoxemia has yet to be established. Although one study has shown that the use of LTOT during pulmonary rehabilitation improves the quality of life of patients with exercise-induced hypoxemia,(7) other studies have shown that the use of LTOT has no beneficial effect on COPD patients with exertional hypoxemia undergoing physical training.(6,8,9) In addition, in patients with moderate resting or exercise-induced hypoxemia, LTOT has been shown to have no beneficial effect on the time to death or first hospitalization.(10) There is no consensus regarding the use of LTOT in such patients.(6,11) Few studies have examined the impact of adherence to LTOT on clinical outcomes in such patients.(10) Therefore, the objective of the present study was to determine the impact of adherence to LTOT on quality of life, dyspnea, and exercise capacity in patients with COPD and exertional hypoxemia followed for one year. METHODS Patients We evaluated 159 COPD patients referred to the Oxygen Therapy Outpatient Clinic of the São Paulo State University Correspondence to: Carolina Bonfanti Mesquita, Departamento de Clínica Médica, Faculdade de Medicina de Botucatu, UNESP, Distrito de Rubião Junior, s/n, CEP 18618-970, Botucatu, SP, Brasil. Tel.: 55 14 3880-1171. Fax: 55 14 3882-2238. E-mail: Financial support: Carolina Bonfanti Mesquita is the recipient of a grant from the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Office for the Advancement of Higher Education). 390 © 2018 Sociedade Brasileira de Pneumologia e Tisiologia ISSN 1806-3713 Mesquita CB, Knaut C, Caram LMO, Ferrari R, Bazan SGZ, Godoy I, Tanni SE Botucatu School of Medicine, in the city of Botucatu, Brazil, in the period between November of 2011 and June of 2012. The inclusion criteria were as follows: having been diagnosed with COPD in accordance with the Global Initiative for Chronic Obstructive Lung Disease criteria(12) and having exertional hypoxemia. At baseline (and while breathing room air), patients experiencing severe arterial hypoxemia during exercise but not at rest were classified as having exertional hypoxemia. To confirm the presence of a PaO2 > 59 mmHg(2,13) at rest and on room air, we performed arterial blood gas analysis. All patients performed a six-minute walk test (6MWT) while breathing room air, the presence of exertional hypoxemia being confirmed by an SpO2 of < 87% during the test. All patients with exertional hypoxemia received a prescription for oxygen supplementation at a flow rate of 0.5 L/ min for at least 12 h per day for one year, to be used when performing activities of daily living (including walking) and during sleep.(11) The exclusion criteria were as follows: severe hypoxemia at rest (PaO2 ≤ 55 mmHg), other respiratory diseases, polycythemia, cor pulmonale, cancer, and active smoking. Clinically unstable patients (medication changes, disease exacerbations, or hospital admissions in the prec (...truncated)