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Cardiopulm Phys Ther J. 2008 December; 19(4): 119–120.
PMCID: PMC2845231

Commentary on Current Literature

Anne Swisher, PT, PhD, CCS
2008 December; 19(4): 119–120.

Are Patients with COPD More Active after Pulmonary Rehabilitation?

Background: Despite a variety of benefits brought by pulmonary rehabilitation to patients with COPD, it is unclear whether these patients are more active during daily life after the program. Methods: Physical activities in daily life (activity monitoring), pulmonary function (spirometry), exercise capacity (incremental cycle-ergometer testing and 6-min walk distance testing), muscle force (quadriceps and handgrip force, and inspiratory and expiratory maximal pressures), quality of life (chronic respiratory disease questionnaire), and functional status (pulmonary functional status and dyspnea questionnaire-modified version) were assessed at baseline, after 3 months of a multidisciplinary rehabilitation program, and at the end of a 6-month multidisciplinary rehabilitation program in 29 patients (mean [± SD] age, 67 ± 8 years; FEV1, 46 ± 16% predicted). Results: Exercise capacity, muscle force, quality of life, and functional status improved significantly after 3 months of pulmonary rehabilitation (all p < 0.05), with further improvements in muscle force, functional status, and quality of life at 6 months. Movement intensity during walking improved significantly after 3 months (p = 0.046) with further improvements after 6 months (p = 0.0002). Walking time in daily life did not improve significantly at 3 months (mean improvement, 7 ± 35%; p = 0.21), but only after 6 months (mean improvement, 20 ± 36%; p = 0.008). No significant changes occurred in other activities or in the pattern of the time spent walking in daily life. Changes in dyspnea after the program were significantly related to changes in walking time in daily life (r = 0.43; p = 0.02). Conclusion: If one aims at changing physical activity habits in the daily life of COPD patients, the contribution of long-lasting programs might be important.

COMMENTARY

Promoting physical activity in persons with chronic disease presents significant and unique challenges. One of the implied outcomes of pulmonary rehabilitation for people with COPD is to teach patients to become independent in all aspects of life, including physical activity and exercise. The findings of this study suggest that improving exercise capacity alone will not translate into greater physical activity in daily life. Thus, there is a need to incorporate strategies to change behaviors related to physical activity and exercise. The findings that changes in daily physical activity only occurred after 6 months of rehabilitation suggest that these behavior changes take time.

2008 December; 19(4): 119–120.

Habitual Physical Activity in Daily Life Correlates Positively with Markers for Mitochondrial Capacity

Physical exercise training is a powerful tool to maintain or improve mitochondrial density and function (mitochondrial capacity). This study aims to determine whether mitochondrial capacity is also associated with habitual physical activity in daily life (PADL). The capacity of classic markers for mitochondrial density, ie, the capacity of citrate synthase (CS) and succinate dehydrogenase (SDH), as well the capacity of cytochrome c oxidase (COX) and beta-hydroxyacyl-CoA dehydrogenase (HAD), was determined in homogenized muscle biopsy samples obtained from the vastus lateralis muscle of nonexercising healthy young (age 20 ± 2 yr) subjects (31 women, 7 men). PADL was measured during two periods of 14 days using a triaxial accelerometer for movement registration. CS, SDH, and COX were positively associated with PADL [P < 0.05, R = 0.36, 95% confidence interval (CI): 1.3.10−4 to 2.2.103; P < 0.05, R=0.39, 95% CI: 1.1.10−5 to 9.9.10−5; and P < 0.05, R = 0.33, 95% CI: 7.5.10−6 to 3.6.10−4, respectively], and HAD tended to correlate positively with PADL (P = 0.06, R = 0.31, 95% CI: −2.2.10−5 to 1.1.10−3). The population was subsequently stratified based on the intensity of the activities performed. CS was only associated with PADL in subjects spending more time on high-intensity physical activity, whereas HAD was only associated with PADL in subjects spending less time on low intensity physical activity. We are the first to report that even within the range of normal daily life activities, mitochondrial capacity is positively associated with the level of habitual physical activity in daily life. Thus an active lifestyle may help to maintain or improve mitochondrial capacity.

COMMENTARY

This study sought to determine if muscle metabolism, specifically mitochondrial oxidative capacity, was related to levels of physical activity. By finding a positive association between higher levels of physical activity and oxidative enzyme activity, the authors give evidence of a relationship. However, the question remains—does increasing activity cause greater oxidative capacity or do people who have higher oxidative capacity find it easier to be more physically active? These types of questions are difficult to answer but important. The authors have identified potentially important thresholds of physical activity (39 minutes per day of moderate to high intensity and 8 minutes per day of high intensity) associated with better oxidative capacity which may give our patients some targets for activity.

2008 December; 19(4): 119–120.

Sex Differences in the Perceived Intensity of Breathlessness During Exercise with Advancing Age

The prevalence of activity-related breathlessness increases with age, particularly in women, but the specific underlying mechanisms have not been studied. This novel cross-sectional study was undertaken to examine the effects of age and sex, and their interaction, on the perceptual and ventilatory responses to incremental treadmill exercise in 73 healthy participants (age range 40-80 yr old) with normal pulmonary function. Age-related changes at a standardized oxygen uptake (VO2) during exercise included significant increases in breathlessness ratings (Borg scale), ventilation (VE), ventilatory equivalent for carbon dioxide, and the ratio of tidal volume (VT) to dynamic inspiratory capacity (IC) (all P < 0.05). These changes were quantitatively similar in women (n = 39) and in men (n = 34). For the group as a whole, exertional breathlessness ratings increased as resting static inspiratory muscle strength diminished (P = 0.05), as exercise ventilation increased relative to capacity (P = 0.013) and as the VT/IC ratio increased (P = 0.003) during exercise. Older women (60-80 yr old, n = 23) reported greater (P < 0.05) intensity of exertional breathlessness at a standardized VO2 and VE than age-matched men (n = 16), despite similar age-related changes in ventilatory demand and dynamic ventilatory mechanics. These increases in breathlessness ratings in older women disappeared when sex differences in baseline maximal ventilatory capacity were accounted for. In conclusion, although increased exertional breathlessness with advancing age is multifactorial, contributory factors included higher ventilatory requirements during exercise, progressive inspiratory muscle weakness, and restrictive mechanical constraints on Vt expansion related to reduced IC. The sensory consequences of this age-related respiratory impairment were more pronounced in women, who, by nature, have relatively reduced maximal ventilatory reserve.

COMMENTARY

It is a common observation that healthy elderly women are more likely to report dyspnea as limiting their exercise capacity than healthy elderly men. They are also likely to report higher intensity of dyspnea at a given exercise level than men. This study sought to tease out effects of aging and gender on these observations. None of the subjects were ventilatory limited in their maximal exercise capacity, yet the older women reported higher dyspnea ratings than the men. The authors suggest smaller airways, dynamic hyperinflation, inspiratory muscle weakness, or increased stiffness in the lungs as potentials causes. However, they did not examine breathing pattern, beyond noting a higher breathing frequency in older women, as related to intensity of dyspnea. Perhaps older women also favor a breathing pattern that is less efficient and could cause greater dyspnea. This study remains to be performed. Any takers?

2008 December; 19(4): 119–120.

Restoration of Cough Reflex in Lung Transplant Recipients

Background: Lung transplantation involves vagal nerve interruption resulting in sensory airway denervation and impairment of the cough reflex. Following lung transplantation, it is unclear whether functional recovery of the cough reflex occurs over time. Our objective was to evaluate the afferent limb of the cough reflex in lung transplant recipients. Methods: The assessment of cough reflex involved upper airway anesthesia, conscious sedation, and fiberoptic bronchoscopy; the biopsy forceps and a 5% dextrose solution were applied through the bronchoscope to the airway mucosa at the main carina, proximal and distal to the anastomosis. A cross-sectional group of seven subjects underwent a single assessment, while eight subjects in a longitudinal group underwent assessment at 1.5 and 12 months. Cough frequency was determined by counting the number of audible coughs and abdominal muscle contractions measured with a surface electromyogram recorder. The airway anastomosis from deceased subjects in the longitudinal group was examined for nerves. Results: All seven subjects from the cross-sectional group demonstrated a similar cough frequency after mechanical and chemical irritation of all airway sites. All subjects in the longitudinal group who were evaluated at 1.5 weeks had a cough response at all sites except distal to the anastomosis. Twelve months after transplantation, cough was present at all sites. Immunohistochemical staining for protein gene product 9.5, low-affinity neurotrophin, and vanilloid receptors demonstrated nerves in subepithelial regions proximal and distal to the airway anastomosis. Conclusion: In human lung transplant recipients, recovery of the cough reflex was noted 12 months after lung transplantation.

COMMENTARY

It is a well-known fact that donor lungs and trachea lack innervation in the transplant patient. These patients often lack a protective cough reflex, which can predispose them to pneumonia and aspiration in the postoperative period. However, anecdotal reports suggest that the lack of a cough reflex is not permanent. Duarte et al undertook a very careful analysis of cough response to both saline instillation and mechanical irritation to the airways both above and below the level of the anastamosis at different time points following transplantation. Their finding of cough reflex recovery at 1.5 months postoperatively gives patients and clinicians a timeline for emphasizing specific airway clearance and protection techniques. Further, their autopsy finding of nerve ingrowth at the anastamosis suggests the reason for the restoration of the cough reflex. Further work is needed to pinpoint the time of reinnervation of the donor airways.

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Articles from Cardiopulmonary Physical Therapy Journal are provided here courtesy of Cardiopulmonary Physical Therapy Section of the American Physical Therapy Association