Original Article
Does the 6-minute walk test predict nocturnal oxygen desaturation in patients with moderate to severe COPD?
Chronic Respiratory Disease 2015, Vol. 12(1) 61–68 ª The Author(s) 2014 Reprints and permission: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1479972314562406 crd.sagepub.com
Sinem Iliaz1, Tulin Cagatay1, Zuleyha Bingol1, Gulfer Okumus1, Raim Iliaz2, Goksen Kuran3, Esen Kiyan1 and Penbe Cagatay4
Abstract Patients with chronic obstructive pulmonary disease (COPD) who have nocturnal oxygen desaturation (NOD) can be treated with nocturnal oxygen therapy (NOT) to avoid possible morbidity and mortality. Although there is no definite data recommending NOT alone, our aim is to evaluate the relationship between desaturation during the six-minute walk test (6MWT) and NOD in COPD. Fifty-five stable patients with COPD were enrolled in this study. The 6MWT and nocturnal oximetry were performed. Patients with comorbid diseases and respiratory failure were excluded. In total, 55 patients (49 males and 6 females, mean age: 65.8 + 8.4 years) were analysed. Twenty-seven of the patients had moderate COPD and the remainder (n ¼ 28) had severe COPD. Three patients (11%) with moderate COPD and 12 patients (42.9%) with severe COPD desaturated during 6MWT (p ¼ 0.003). NOD was observed in five patients with severe COPD (17.9%). There were no patients with NOD in the moderate COPD group. Three (25%) of patients with severe COPD who desaturated during the 6MWT also had NOD. NOD was more common in patients with severe COPD and the patients with higher carbon dioxide levels (p ¼ 0.02 and p ¼ 0.001). Three patients (11%) with moderate COPD desaturated during the 6MWT; however they did not have NOD. Although the sample size in this study was too small to be conclusive, NOD was more common in desaturators during the 6MWT particularly in patients with severe COPD. Keywords Chronic obstructive pulmonary disease, nocturnal desaturation, six-minute walk test, COPD stage, nocturnal oxygen therapy
Introduction Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide.1–3 The quality of life is poor in the vast majority of patients with COPD, and these patients die at early ages.4 Morbidity and mortality are mostly due to respiratory failure and its complications.5 Patients with moderate and severe COPD suffer from hypoxaemia.6,7 In previous studies, long-term oxygen therapy (LTOT) has been reported to reduce mortality in COPD patients with respiratory failure; therefore, early identification of individuals for LTOT is important.8–10 Some patients with COPD may desaturate only during exercise or
1
Department of Pulmonology, Faculty of Medicine, Istanbul University, Istanbul, Turkey 2 Department of Internal Medicine, Faculty of Medicine, Istanbul University, Istanbul, Turkey 3 Division of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Istanbul University, Istanbul, Turkey 4 Department of Biostatistics, Faculty of Medicine, Istanbul University, Istanbul, Turkey Corresponding author: Sinem Iliaz, Istanbul University, Istanbul Faculty of Medicine, Department of Pulmonology, Fatih, Istanbul 34093, Turkey. Email: [email protected]
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sleep. Current guidelines do not recommend nocturnal oxygen treatment (NOT) for patients with nocturnal oxygen desaturation (NOD) accompanied by daytime normoxaemia. The clinical importance of NOD is unclear in the literature, and there is a need for studies to understand complications and results of NOD. Nocturnal oximetry is used for evaluating NOD, which is a process that requires overnight monitoring. It is also time-consuming due to staff time. This study was designed to investigate the utility of the 6-minute walk test (6MWT), a more practical test, instead of nocturnal oximetry for identifying patients who have NOD. Our aim was to evaluate whether desaturation during 6MWT was useful in predicting NOD at different stages of COPD.
Methods The study was performed between September 2011 and June 2012 in the Pulmonology Department of our university. Patients with moderate and severe COPD who were not hypoxaemic at rest were included in this study. Patients were excluded if they had a history of acute exacerbation of COPD in the previous month, respiratory failure, were on LTOT or noninvasive mechanical ventilation, had clinically decompensated heart failure (newly developed peripheral oedema, orthopnoea and paroxysmal nocturnal dyspnoea) or were known or suspected to have obesity hypoventilation/obstructive sleep apnoea syndrome. Suspicion of obstructive sleep apnoea syndrome depended on having cardinal symptoms (snoring, witnessed apnoea and excessive daytime sleepiness) and an Epworth Sleepiness Scale score 10. Body mass index (BMI) was calculated using the formula: weight (kg)/height2 (m2).11 Patients with BMI 35 and partial arterial carbon dioxide (paCO2) >45 mmHg were excluded from the study to exclude possible sleep disorders. COPD diagnosis and disease severity were determined according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guideline criteria.12 According to the GOLD guideline criteria, patients were classified as moderate (stage II) COPD if postbronchodilator forced expiratory volume in one second (FEV1) was 50–80% of predicted and as severe (stage III) COPD if FEV1 was 30–50% of predicted values. All patients underwent spirometry, carbon monoxide diffusion test (DLCO), arterial blood gas analysis (ABG) at rest under normal room air conditions. In order to evaluate the severity of dyspnoea, modified Medical Research Council (mMRC) and
Modified Borg dyspnoea scales were used.13,14 Spirometry and DLCO tests were performed using Zan 100 MGA USB Pulmonary Function Device (No:130033, Zan Messgerate, Germany) in accordance with approved standards.15 ABG was performed in the room air after 15 minutes rest using a Cobass b 221 System (Roche Inc., Pleasanton, California, USA). The 6MWT was performed in accordance with the American Thoracic Society guidelines.16 The 6MWT was performed in a 30metre long, straight corridor under the guidance of a single respiratory physiotherapist. There was no practice test prior to 6MWT, but our physiotherapist showed each patient how to walk and turn after a lap was completed. During the exercise, the physiotherapist informed the patients when each minute had elapsed and encouraged them to continue. Oxygen saturation during the test was recorded using the finger probe of a portable pulse oximeter (VM 2160 pulse oximeter, Viamed, UK). During this process, baseline and end 6MWT values of blood pressure, pulse rate, peripheral oxygen saturation (SpO2), Borg dyspnoea scale and mMRC scores of the patients were recorded. At the end of the test, the 6-minute walk distance (6MWD) was recorded. Oxygen desaturation during exercise was defined as a fall in SpO2 of 4% to a value
Does the 6-minute walk test predict nocturnal oxygen desaturation in patients with moderate to severe COPD?
Chronic Respiratory Disease 2015, Vol. 12(1) 61–68 ª The Author(s) 2014 Reprints and permission: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1479972314562406 crd.sagepub.com
Sinem Iliaz1, Tulin Cagatay1, Zuleyha Bingol1, Gulfer Okumus1, Raim Iliaz2, Goksen Kuran3, Esen Kiyan1 and Penbe Cagatay4
Abstract Patients with chronic obstructive pulmonary disease (COPD) who have nocturnal oxygen desaturation (NOD) can be treated with nocturnal oxygen therapy (NOT) to avoid possible morbidity and mortality. Although there is no definite data recommending NOT alone, our aim is to evaluate the relationship between desaturation during the six-minute walk test (6MWT) and NOD in COPD. Fifty-five stable patients with COPD were enrolled in this study. The 6MWT and nocturnal oximetry were performed. Patients with comorbid diseases and respiratory failure were excluded. In total, 55 patients (49 males and 6 females, mean age: 65.8 + 8.4 years) were analysed. Twenty-seven of the patients had moderate COPD and the remainder (n ¼ 28) had severe COPD. Three patients (11%) with moderate COPD and 12 patients (42.9%) with severe COPD desaturated during 6MWT (p ¼ 0.003). NOD was observed in five patients with severe COPD (17.9%). There were no patients with NOD in the moderate COPD group. Three (25%) of patients with severe COPD who desaturated during the 6MWT also had NOD. NOD was more common in patients with severe COPD and the patients with higher carbon dioxide levels (p ¼ 0.02 and p ¼ 0.001). Three patients (11%) with moderate COPD desaturated during the 6MWT; however they did not have NOD. Although the sample size in this study was too small to be conclusive, NOD was more common in desaturators during the 6MWT particularly in patients with severe COPD. Keywords Chronic obstructive pulmonary disease, nocturnal desaturation, six-minute walk test, COPD stage, nocturnal oxygen therapy
Introduction Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide.1–3 The quality of life is poor in the vast majority of patients with COPD, and these patients die at early ages.4 Morbidity and mortality are mostly due to respiratory failure and its complications.5 Patients with moderate and severe COPD suffer from hypoxaemia.6,7 In previous studies, long-term oxygen therapy (LTOT) has been reported to reduce mortality in COPD patients with respiratory failure; therefore, early identification of individuals for LTOT is important.8–10 Some patients with COPD may desaturate only during exercise or
1
Department of Pulmonology, Faculty of Medicine, Istanbul University, Istanbul, Turkey 2 Department of Internal Medicine, Faculty of Medicine, Istanbul University, Istanbul, Turkey 3 Division of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Istanbul University, Istanbul, Turkey 4 Department of Biostatistics, Faculty of Medicine, Istanbul University, Istanbul, Turkey Corresponding author: Sinem Iliaz, Istanbul University, Istanbul Faculty of Medicine, Department of Pulmonology, Fatih, Istanbul 34093, Turkey. Email: [email protected]
Downloaded from crd.sagepub.com at COLUMBIA UNIV on February 2, 2015
62
Chronic Respiratory Disease 12(1)
sleep. Current guidelines do not recommend nocturnal oxygen treatment (NOT) for patients with nocturnal oxygen desaturation (NOD) accompanied by daytime normoxaemia. The clinical importance of NOD is unclear in the literature, and there is a need for studies to understand complications and results of NOD. Nocturnal oximetry is used for evaluating NOD, which is a process that requires overnight monitoring. It is also time-consuming due to staff time. This study was designed to investigate the utility of the 6-minute walk test (6MWT), a more practical test, instead of nocturnal oximetry for identifying patients who have NOD. Our aim was to evaluate whether desaturation during 6MWT was useful in predicting NOD at different stages of COPD.
Methods The study was performed between September 2011 and June 2012 in the Pulmonology Department of our university. Patients with moderate and severe COPD who were not hypoxaemic at rest were included in this study. Patients were excluded if they had a history of acute exacerbation of COPD in the previous month, respiratory failure, were on LTOT or noninvasive mechanical ventilation, had clinically decompensated heart failure (newly developed peripheral oedema, orthopnoea and paroxysmal nocturnal dyspnoea) or were known or suspected to have obesity hypoventilation/obstructive sleep apnoea syndrome. Suspicion of obstructive sleep apnoea syndrome depended on having cardinal symptoms (snoring, witnessed apnoea and excessive daytime sleepiness) and an Epworth Sleepiness Scale score 10. Body mass index (BMI) was calculated using the formula: weight (kg)/height2 (m2).11 Patients with BMI 35 and partial arterial carbon dioxide (paCO2) >45 mmHg were excluded from the study to exclude possible sleep disorders. COPD diagnosis and disease severity were determined according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guideline criteria.12 According to the GOLD guideline criteria, patients were classified as moderate (stage II) COPD if postbronchodilator forced expiratory volume in one second (FEV1) was 50–80% of predicted and as severe (stage III) COPD if FEV1 was 30–50% of predicted values. All patients underwent spirometry, carbon monoxide diffusion test (DLCO), arterial blood gas analysis (ABG) at rest under normal room air conditions. In order to evaluate the severity of dyspnoea, modified Medical Research Council (mMRC) and
Modified Borg dyspnoea scales were used.13,14 Spirometry and DLCO tests were performed using Zan 100 MGA USB Pulmonary Function Device (No:130033, Zan Messgerate, Germany) in accordance with approved standards.15 ABG was performed in the room air after 15 minutes rest using a Cobass b 221 System (Roche Inc., Pleasanton, California, USA). The 6MWT was performed in accordance with the American Thoracic Society guidelines.16 The 6MWT was performed in a 30metre long, straight corridor under the guidance of a single respiratory physiotherapist. There was no practice test prior to 6MWT, but our physiotherapist showed each patient how to walk and turn after a lap was completed. During the exercise, the physiotherapist informed the patients when each minute had elapsed and encouraged them to continue. Oxygen saturation during the test was recorded using the finger probe of a portable pulse oximeter (VM 2160 pulse oximeter, Viamed, UK). During this process, baseline and end 6MWT values of blood pressure, pulse rate, peripheral oxygen saturation (SpO2), Borg dyspnoea scale and mMRC scores of the patients were recorded. At the end of the test, the 6-minute walk distance (6MWD) was recorded. Oxygen desaturation during exercise was defined as a fall in SpO2 of 4% to a value
