Effects of Body Mass Index on Task-Related Oxygen Uptake and Dyspnea during Activities of Daily Life in COPD

<div><h3>Background</h3><p>Patients with COPD use a higher proportion of their peak aerobic capacity during the performance of domestic activities of daily life (ADLs) compared to healthy peers, accompanied by a higher degree of task-related symptoms. To date, the influence of body mass index (BMI) on the task-related metabolic demands remains unknown in patients with COPD. Therefore, the aim of our study was to determine the effects of BMI on metabolic load during the performance of 5 consecutive domestic ADLs in patients with COPD.</p> <h3>Methodology</h3><p>Ninety-four COPD patients and 20 healhty peers performed 5 consecutive, self-paced domestic ADLs putting on socks, shoes and vest; folding 8 towels; putting away groceries; washing up 4 dishes, cups and saucers; and sweeping the floor for 4 min. Task-related oxygen uptake and ventilation were assessed using a mobile oxycon, while Borg scores were used to assess task-related dyspnea and fatigue.</p> <h3>Principal Findings</h3><p>1. Relative task-related oxygen uptake after the performance of domestic ADLs was increased in patients with COPD compared to healthy elderly, whereas absolute oxygen uptake is similar between groups; 2. Relative oxygen uptake and oxygen uptake per kilogram fat-free mass were comparable between BMI groups; and 3. Borg symptom scores for dyspnea en fatigue were comparable between BMI groups.</p> <h3>Conclusion</h3><p>Patients with COPD in different BMI groups perform self-paced domestic ADLs at the same relative metabolic load, accompanied by comparable Borg symptom scores for dyspnea and fatigue.</p> </div

Characteristics.

<p>Results are presented as mean (standard deviation). FEV₁  =  forced expiratory volume in the first second; L  =  litre; FVC  =  forced vital capacity; kg  =  kilogram; kg/m²  =  kilogram per squared meters; Charlson CMI  =  Charlson co-morbidity index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041078#pone.0041078-Charlson1" target="_blank">[19]</a>; Charlson CMI 2 =  Charlson age comorbidity index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041078#pone.0041078-Charlson2" target="_blank">[20]</a>; 6MWD  =  six-minute walking distance; VO2 =  oxygen uptake; mL  =  millilitre; min  =  minute; BW  =  body weight; FFM  =  fat free mass; VE  =  minute ventilation; MVV  =  maximum voluntary ventilation; HR  =  heart rate; bpm  =  beats per minute. ^*1 kPa  = 7.5 mm Hg; ^**1 kilogram  = 2.2046 pounds; ^†p≤0.05 vs. healthy subjects.</p

Borg symptom scores after performance of domestic ADLs.

<p>a. absolute Borg dyspnea scores. b. relative Borg dyspnea scores (%peak). c. absolute Borg fatigue scores. d. relative Borg fatigue scores (%peak).</p

Task-related oxygen uptake in patients with COPD and healthy controls.

<p>a. Absolute task-related oxygen uptake (mL/min). b. Relative task-related oxygen uptake (%peakVO₂).</p

Baseline characteristics by BMI categories.

<p>Results are presented as mean (standard deviation). FEV₁  =  forced expiratory volume in the first second; L  =  litre; FVC  =  forced vital capacity; kg  =  kilogram; kg/m²  =  kilogram per squared meters; Charlson CMI  =  Charlson co-morbidity index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041078#pone.0041078-Charlson1" target="_blank">[19]</a>; Charlson CMI 2 =  Charlson age comorbidity index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041078#pone.0041078-Charlson2" target="_blank">[20]</a>; 6MWD  =  six-minute walking distance; VO2 =  oxygen uptake; mL  =  millilitre; min  =  minute; BW  =  body weight; FFM  =  fat free mass; VE  =  minute ventilation; MVV  =  maximum voluntary ventilation; HR  =  heart rate; bpm  =  beats per minute. ^*1 kPa  = 7.5 mm Hg; ^**1 kilogram  = 2.2046 pounds; ^†p<0.05 vs. <21 kg/m² +p<0.05 vs. 21–25 kg/m²^#p<0.05 vs. 25–30 kg/m².</p

Task-related oxygen uptake in patients with COPD.

<p>a. Relative task-related oxygen uptake (%peakVO₂). b. Task-related oxygen uptake per kilogram FFM (mL/min/kg FFM).</p

Task-related ventilation in patients with COPD.

<p>a. Relative task-related ventilation (%peakVE).</p

A and B. Prevalence of metabolic syndrome and its components in male and female COPD and healthy subjects with BMI <25 kg/m².

<p>WC, waist circumference; HDL, high density lipoprotein; Syst BP, systolic blood pressure; Dia BP, diastolic blood pressure; Met Syn, metabolic syndrome.</p

Baseline characteristics of the total study population.

<p>Data are presented: mean ± SD, percentages or ^#median (interquartile range) if data were not normal distributed.</p><p>FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; BMI, body mass index; FFMI, fat free mass index; HDL, high density lipoprotein.</p>$<p>according to the IDF.</p><p>Other symbols:</p><p>*p<0.01,</p>†<p>p<0.05 compared with COPD patients.</p

Clinical and functional characteristics of the COPD patients by metabolic syndrome.

<p>Data are mean ± SD or percentages or ^#median (interquartile range) if data were not normal distributed.</p><p>FEV₁, forced expiratory volume in the first second; FVC, forced vital capacity; BMI, body mass index; FFMI, fat free mass index; BMD, bone mineral density; 6MWD, six minute walking distance; LTOT, long term oxygen therapy; PaCO₂, arterial carbon dioxide tension; PaO₂, arterial oxygen tension; CVD, cardiovascular disease; inhaled and oral CS, inhaled and oral corticosteroids; MRC, modified Medical Research Council; HADS, Hospital Anxiety and Depression Scale; SGRQ, St. George Respiratory Questionnaire.</p><p>*<i>p</i><0.01,</p>†<p><i>p</i><0.05 compared to patients without the metabolic syndrome.</p