Oxygen uptake, ventilation, and symptoms during low-frequency versus high-frequency NMES in COPD: a pilot study.

Transcutaneous neuromuscular electrical stimulation (NMES) involves the application of an electrical current through electrodes placed on the skin over the targeted muscles. During high-frequency NMES (HF-NMES), oxygen uptake, minute ventilation, and the degree of symptom perception (dyspnea and fatigue) have been shown to be acceptable in chronic obstructive pulmonary disease (COPD). Currently, oxygen uptake and ventilation load have never been assessed during low-frequency NMES (LF-NMES) of the lower-limb muscles. The purpose of this study was to compare prospectively oxygen uptake, ventilation, and symptom perception during a single session of LF-NMES versus a single session of HF-NMES of quadriceps muscles in patients with COPD. In 17 COPD patients (mean FEV(1) = 45% predicted, mean body mass index = 26.2 kg/m(2)), peak exercise capacity, functional exercise capacity, and the Medical Research Council dyspnea grade were evaluated. In addition, oxygen uptake, minute ventilation, heart rate, and Borg symptom scores were assessed during one session of LF-NMES (15 Hz) and one session of HF-NMES (75 Hz) and compared with peak values. Mean oxygen uptake (LF-NMES: 327 ml/min vs. HF-NMES: 315 ml/min), minute ventilation (LF-NMES: 14 L vs. HF-NMES: 15 L), and heart rate (LF-NMES: 86 BPM vs. HF-NMES: 83 BPM) were similar during both NMES frequencies. Patients used a relatively low proportion of their peak aerobic capacity during both NMES sessions (LF-NMES: 34% vs. HF-NMES: 33%; P = 0.397). In addition, symptom Borg scores for dyspnea and leg fatigue were also comparable. Oxygen uptake, ventilation, and symptoms of dyspnea and fatigue were comparable and tolerable during LF-NMES and HF-NMES in patients with COPD. Therefore, LF-NMES and HF-NMES may both be suitable rehabilitative modalities to be used in severely dyspneic patients with lower-limb muscle dysfunction.

Task-related oxygen uptake and symptoms during activities of daily life in CHF patients and healthy subjects.

Patients with chronic heart failure (CHF) have a significantly lower peak aerobic capacity compared to healthy subjects, and, may therefore experience more inconvenience during the performance of domestic activities of daily life (ADLs). To date, the extent to which task-related oxygen uptake, heart rate, ventilation and symptoms during the performance of ADLs in CHF patients is different than in healthy subjects remains uncertain. General demographics, pulmonary function, body composition and peak aerobic capacity were assessed in 23 CHF outpatients and 20 healthy peers. In addition, the metabolic requirement of five simple self-paced domestic ADLs was assessed using a mobile oxycon. Task-related oxygen uptake (ml/min) was similar or lower in CHF patients compared to healthy subjects. In contrast, patients with CHF performing ADLs consumed oxygen at a higher proportion of their peak aerobic capacity than healthy subjects (p < 0.05). For example, getting dressed resulted in a mean task-related oxygen uptake of 49% of peak aerobic capacity, while sweeping the floor resulted in a mean task-related oxygen uptake of 52% of peak aerobic capacity, accompanied by significantly higher Borg symptom scores for dyspnea and fatigue (p < 0.05). Patients with CHF experience use a higher proportion of their peak aerobic capacity, peak ventilation and peak heart rate during the performance of simple self-paced domestic ADL than their healthy peers. These findings represent a necessary step in improving our understanding of improving what troubles patients the most-not being able to do the things that they could when they were healthy.

Task-related oxygen uptake during domestic activities of daily life in patients with COPD and healthy elderly subjects.

BACKGROUND: Patients with COPD generally have a poor peak aerobic capacity and, therefore, may experience more inconvenience during domestic activities of daily life (ADLs). Yet, task-related oxygen uptake and symptom perception during ADLs have been studied rarely in COPD. Therefore, it remains unknown whether and to what extent differences may exist in task-related oxygen uptake and symptom perception during ADLs in patients with COPD after stratification for sex; GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage; Medical Research Council (MRC) dyspnea grade; or score on the BMI, obstruction, dyspnea, exercise capacity (BODE) index. METHODS: Ninety-seven patients with COPD and 20 healthy elderly subjects performed the following five self-paced domestic ADLs with 4-min rest intervals: putting on socks, shoes, and vest; folding eight towels; putting away groceries; washing four dishes, cups, and saucers; and sweeping the floor for 4 min. Task-related oxygen uptake was assessed using an Oxycon Mobile device, whereas Borg scores were used to assess task-related dyspnea and fatigue. RESULTS: Patients with COPD used a significantly higher proportion of their peak aerobic capacity and ventilation to perform ADLs than did the healthy subjects, accompanied by higher task-related Borg dyspnea scores. Patients with GOLD stage IV, MRC dyspnea grade 5, or BODE score ≥ 6 points had the highest task-related oxygen uptake and dyspnea perception during the performance of domestic ADLs. Results showed no sex-related differences. CONCLUSION: Patients with COPD experience a relatively high metabolic load and symptom perception during the performance of ADLs that is not the same as seen in their healthy peers, particularly in patients with GOLD stage IV, MRC dyspnea grade 5, or BODE score ≥ 6 points.