W. Edwin Langbein

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.

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.

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 </= 0.0167 was used for statistical significance). After training, exercise-induced dynamic hyperinflation, measured at isotime, in VF plus exercise was less than in exercise alone (P = 0.014 for between-group changes) and less than in VF alone (P = 0.019 for between-group changes). After training, expiratory time was longer in VF plus exercise training (P < 0.001), and it was not significantly changed in the other two groups. CONCLUSIONS The combination of VF plus exercise training decreases exercise-induced dynamic hyperinflation and increases exercise duration more than VF alone. An additive effect to exercise training from VF was not demonstrated by predetermined statistical criteria.

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.

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.