Determinants of cough effectiveness in patients with respiratory muscle weakness.

Experiments were undertaken to mechanistically define expiratory-muscle contribution to effectiveness of cough while controlling glottic movement. We hypothesized that electrical abdominal-muscle stimulation in patients with respiratory-muscle weakness produces effective coughs only when glottic closure accompanies coughs. In ten spinal-cord-injury patients, esophago-gastric pressure and airflow were recorded during solicited-coughs, coughs augmented by abdominal-muscle stimulation, and passive open-glottis exhalations. During solicited-coughs, patients closed the glottis initially; five were flow-limited, five non-flow-limited. Stimulations during solicited-coughs or open-glottis exhalations elicited similar driving pressures (changes in gastric pressure; p<0.001). Despite high driving pressures, stimulations induced flow-limitation only when patients transiently closed the glottis - not during open-glottis exhalations. That is, transient glottic closure enabled transmission of abdominal (driving) pressure to the thorax during cough, while impeding dissipation of intrathoracic pressure. In conclusion, transient glottic closure is necessary to render cough effective in patients with respiratory-muscle weakness, indicating that failure to close the glottis contributes to ineffective cough in weak tracheostomized patients and patients with bulbar disorders.

Contrasting pressure-support ventilation and helium-oxygen during exercise in severe COPD.

Helium-oxygen mixtures and pressure-support ventilation have been used to unload the respiratory muscles and increase exercise tolerance in COPD. Considering the different characteristics of these techniques, we hypothesized that helium-oxygen would be more effective in reducing exercise-induced dynamic hyperinflation than pressure-support. We also hypothesized that patients would experience greater increases in respiratory rate and minute ventilation with helium-oxygen than with pressure-support. The hypotheses were tested in ten patients with severe COPD (FEV(1) = 28 ± 3% predicted [mean ± SE]) during constant-load cycling (80% maximal workrate) while breathing 30% oxygen-alone, helium-oxygen, and pressure-support in randomized order. As hypothesized, helium-oxygen had greater impact on dynamic hyperinflation than did pressure-support (end-exercise; p = 0.03). For the most part of exercise, respiratory rate and minute ventilation were greater with helium-oxygen than with pressure-support (p ≤ 0.008). During the initial phases of exercise, helium-oxygen caused less rib-cage muscle recruitment than did pressure-support (p < 0.03), and after the start of exercise it caused greater reduction in inspiratory reserve volume (p ≤ 0.02). Despite these different responses, helium-oxygen and pressure-support caused similar increases in exercise duration (oxygen-alone: 6.9 ± 0.8 min; helium-oxygen: 10.7 ± 1.4 min; pressure-support: 11.2 ± 1.6 min; p = 0.003) and similar decreases in inspiratory effort (esophageal pressure-time product), respiratory drive, pulmonary resistance, dyspnea and leg effort (p < 0.03). In conclusion, helium-oxygen reduced exercise-induced dynamic hyperinflation by improving the relationship between hyperinflation and minute ventilation. In contrast, pressure-support reduced hyperinflation solely as a result of lowering ventilation. Helium-oxygen was more effective in reducing exercise-induced dynamic hyperinflation in severe COPD, and was associated with greater increases in respiratory rate and minute ventilation than pressure-support.

Energy cost of physical activities in persons with spinal cord injury.

INTRODUCTION: The objectives of this descriptive study were (a) to determine the energy expenditure of activities commonly performed by individuals with a spinal cord injury (SCI) and summarize this information and (b) to measure resting energy expenditure and establish the value of 1 MET for individuals with SCI. METHODS: One-hundred seventy adults with SCI were partitioned by gender, anatomical level of SCI, and American Spinal Injury Association designations for motor function. Twenty-seven physical activities, 12 recreational/sport and 15 daily living, were performed, while energy expenditure was measured continuously via a COSMED K4b portable metabolic system. In addition, 66 adult males with SCI completed 30 min of supine resting energy testing in a quiet environment. RESULTS: Results for the 27 measured activities are reported in kilocalories per minute (kcal·min(-1)) and VO2 (mL·min(-1) and mL·kg(-1)·min(-1)). One MET for a person with SCI should be adjusted using 2.7 mL·kg(-1)·min(-1). Using 2.7 mL·kg(-1)·min(-1), the MET range for persons in the motor incomplete SCI group was 1.17 (supported standing) to 6.22 (wheeling on grass), and 2.26 (billiards) to 16.25 (hand cycling) for activities of daily living and fitness/recreation, respectively. The MET range for activities of daily living for persons in the group with motor complete SCI was 1.27 (dusting) to 4.96 (wheeling on grass) and 1.47 (bait casting) to 7.74 (basketball game) for fitness/recreation. CONCLUSIONS: The foundation for a compendium of energy expenditure for physical activities for persons with SCI has been created with the completion of this study. In the future, others will update and expand the content of this compendium as has been the case with the original compendium for the able-bodied.

Can ventilation-feedback training augment exercise tolerance in patients with chronic obstructive pulmonary disease?

RATIONALE: Exercise-induced dynamic hyperinflation contributes to decreased exercise tolerance in chronic obstructive pulmonary disease (COPD). It is unknown whether respiratory retraining (ventilation-feedback [VF] training) can affect exercise-induced dynamic hyperinflation and increase exercise tolerance. OBJECTIVES: To determine whether patients with COPD would achieve longer exercise duration if randomized to a combination of exercise training plus VF training than either form of training on its own. METHODS: A total of 64 patients randomized to 1 of 3 groups: VF plus exercise (n = 22), exercise alone (n = 20), and VF alone (n = 22). MEASUREMENTS AND MAIN RESULTS: Exercise duration before and after 36 training sessions and exercise-induced dynamic hyperinflation and respiratory pattern before and after training were measured. In the 49 patients who completed training, duration of constant work-rate exercise was 40.0 (+/- 20.4) minutes (mean +/- SD) with VF plus exercise, 31.5 (+/- 17.3) minutes with exercise alone, and 16.1 (+/- 19.3) minutes with VF alone. Exercise duration was longer in VF plus exercise than in VF alone (P < 0.0001), but did not reach predetermined statistical significance when VF plus exercise was compared with exercise alone (P = 0.022) (because of multiple comparisons, P

Cardiovascular training effect associated with polestriding exercise in patients with peripheral arterial disease.

Because individuals with claudication pain secondary to peripheral arterial disease (PAD) are limited in both walking speed and duration, the benefits of walking exercise may be insufficient to yield a cardiovascular training effect. The objectives of this analysis were to determine whether polestriding exercise training, performed by persons with PAD, would improve exercise endurance, elicit a cardiovascular training benefit, and improve quality of life (QoL). Persons (n = 49) whose claudication pain limited their exercise capacity were randomized into a 24-week polestriding training program (n = 25, 65.8 +/- 7.1 years of age) or a nonexercise attention control group (n = 24, 68.0 +/- 8.6 years of age). Those assigned to the polestriding group trained 3 times weekly. Control group subjects came to the laboratory biweekly for ankle blood pressure measurements. A symptom-limited ramp treadmill test, ratings of perceived leg pain, and QoL data (using the Short Form-36) were obtained at baseline and upon completion of training. After 24 weeks of polestriding training, subjects increased their exercise endurance from 10.3 +/- 4.1 minute to 15.1 +/- 4.5 minute. This was significantly greater than control group subjects whose exercise endurance declined (from 11.2 +/- 4.7 to 10.3 +/- 4.7 minute; P < .001). Relationships between systolic blood pressure (P < .001), heart rate (P = .04), rate pressure product (P = .05), oxygen uptake (P = .016), and perceived leg pain (P = .02) and exercise time improved from the baseline symptom-limited treadmill test to the 6-month symptom-limited treadmill test in the polestriding group compared to the control group. The improvement in the physical component summary score of the Short Form-36 was also greater in the polestriding group (P = .031). Polestriding training significantly improved the clinical indicators of cardiovascular fitness and QoL, and decreased symptoms of claudication pain during exertion.

Respiratory and skeletal muscles in hypogonadal men with chronic obstructive pulmonary disease.

Hypogonadism, found in about one-third of patients with chronic obstructive pulmonary disease (COPD), has potential for decreasing muscle mass and muscle performance. Compared with eugonadal patients, we hypothesized that hypogonadal patients with COPD have decreased respiratory and skeletal muscle performance. Nineteen hypogonadal and 20 eugonadal men with COPD (FEV(1) 1.14 +/- 0.08 and 1.17 +/- 0.11 L [standard error], respectively) were studied. Diaphragmatic contractility, assessed as transdiaphragmatic twitch pressure generated by phrenic nerve stimulation, was similar in hypogonadal and eugonadal patients: 20.6 +/- 2.2 and 19.8 +/- 2.5 cm H(2)O, respectively. During progressive inspiratory threshold loading, hypogonadal and eugonadal patients had similar respiratory muscle endurance times (302 +/- 29 and 313 +/- 48 seconds, respectively) and airway pressure sustained during the last minute of loading (38.2 +/- 3.0 and 40.5 +/- 4.7 cm H(2)O, respectively) (similar to predicted values in healthy subjects). Hypogonadal and eugonadal patients had equivalent limb muscle strength and endurance. During cycle exercise to exhaustion, exercise performance, gas exchange, and respiratory muscle recruitment (estimated by esophageal and gastric pressure swings during tidal breathing) were similar in both groups. In conclusion, hypogonadism does not decrease respiratory or limb muscle performance and exercise capacity in men with moderate-to-severe COPD who, for the most part, are not underweight.

Effects of exercise training on aerobic capacity and quality of life in individuals with heart failure.

PURPOSE: The purpose of this study was to determine whether subjects with chronic heart failure, who completed a 12-week rehabilitation program, would have significantly greater quality of life, better aerobic fitness, less difficulty with symptoms of heart failure, greater self-efficacy for exercise, and higher daily activity levels when compared with subjects in a control group. METHODS: Thirty-one males, aged 64 +/- 10 years with left ventricular ejection fraction of 29 +/- 7%, were randomized to a moderate intensity supervised aerobic exercise program (n = 15) or a control group (n = 16). Twenty-seven subjects completed at least 1 follow-up assessment. RESULTS: After 12 weeks there were significant differences in the change scores for perceived physical function (using RAND Corporation's 36-item short form) (P =.025) and peak oxygen uptake (P =.019) between the exercise and control groups with the exercise group experiencing improved physical function and fitness. CONCLUSIONS: Exercise training in adults with heart failure increases exercise tolerance and perceived physical function. Improved heart failure symptoms, self-efficacy for exercise, or increased physical activity may not be associated with enhancement of exercise tolerance.

Effect of ventilation-feedback training on endurance and perceived breathlessness during constant work-rate leg-cycle exercise in patients with COPD.

The purpose of this study was to evaluate the efficacy of a unique program of ventilation-feedback training combined with leg-cycle exercise to improve exertional endurance and decrease perceived dyspnea in patients with chronic obstructive pulmonary disease (COPD). Thirty-nine patients (67.5 +/- 8.1 yr of age) with moderate to severe COPD (42.6% of predicted forced expiratory volume in 1 s) were randomized to one of three 6-week experimental interventions: ventilation-feedback with exercise (V(+EX)), exercise only (EX(ONLY)), or ventilation-feedback only (VF(ONLY)). At baseline and at 6 weeks, patients completed a constant work-rate leg-cycle ergometer test at 85 percent of maximal power output. There were increases within the groups in exercise duration: 11.5 min (103%), 8.0 min (66%), and 0.4 min (4%) for the VF(+EX), EX(ONLY) and VF(ONLY) groups, respectively. The VF(ONLY) group experienced no significant within-group changes in selected gas exchange parameters. However, there were significant (p < 0.05) posttraining changes in minute ventilation, tidal volume, breathing frequency (f), and expiratory time (Te) in the VF(+EX) group, and in f and Te in the EX(ONLY) group. After completing the training, VF(+EX) and EX(ONLY) patients reported less breathlessness and perceived exertion (p < 0.05). The VF(ONLY) patients' ratings changed in the hypothesized direction but were not significant. Based on these preliminary data, VF(+EX) and EX(ONLY) were equally effective in improving leg-cycle exercise tolerance in patients with moderate to severe COPD.

Increasing exercise tolerance of persons limited by claudication pain using polestriding.

OBJECTIVE: The efficacy of polestriding exercise (walking with modified ski poles with a movement pattern similar to cross-country skiing) to increase exercise tolerance of persons with intermittent claudication pain caused by peripheral arterial disease was tested in this 24-week prospective randomized clinical trial. METHODS: The study was conducted in a Department of Veterans Affairs Hospital with 52 individuals who gave written informed consent and were randomized into either a polestriding exercise (n = 27; age, 65.5 +/- 7.0 years; ankle brachial index, 0.64 +/- 0.25) or nonexercise control (n = 25; age, 68.6 +/- 8.9 years; ankle brachial index, 0.69 +/- 0.14) group (P >.05 for all comparisons). The polestriding exercise program consisted of supervised training three times per week for 4 weeks, two times per week for 8 weeks, one time per week for 4 weeks, biweekly for 4 weeks and unsupervised training for 4 weeks. Starting in week 5, subjects took their poles home with instructions to repeat the most recent supervised training walk at an appropriate and convenient location near their residence. This was referred to as unsupervised but directed exercise. Subjects were provided with a personal log book for documenting unsupervised exercise sessions. With both supervised and unsupervised exercise, subjects were expected to complete a total of four 30-minute to 45-minute polestriding exercise sessions per week. The main outcome measures were exercise duration on symptom-limited incremental treadmill test, Walking Impairment Questionnaire, rating of perceived leg pain at baseline, 4, 8, 12, 16, and 24 weeks, and constant work-rate treadmill exercise tests at baseline and at 4, 12, and 24 weeks. RESULTS: Polestriding significantly (P <.001) improved exercise tolerance on the constant work-rate and incremental treadmill tests. Ratings of perceived claudication pain were significantly less after the polestriding training program. Subject perceived distance and walking speed scores on the Walking Impairment Questionnaire improved in the polestriding trained group only (P <.001 and.022, respectively). CONCLUSION: This randomized clinical trial provides empirical evidence that 24 weeks of polestriding training significantly improves quantitative and qualitative measures of the exercise tolerance of persons limited by intermittent claudication pain.