Chronic obstructive pulmonary disease (COPD)

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Chronic Obstructive Pulmonary Disease (COPD) is characterized by persistently limited airflow. It is associated with an enhanced chronic inflammatory response in the airways and lungs to noxious particles or gases. Aerobic exercise, interval-training, resistance-training and inspiratory muscle training can all be used to help individuals with COPD improve their breathing, fitness, exercise capacity and health-related quality of life.

CONTENTS


What is Chronic Obstructive Pulmonary Disease?

Chronic Obstructive Pulmonary Disease (COPD) is characterized by persistently limited airflow and is associated with an enhanced chronic inflammatory response in the airways and lungs to noxious particles or gases (Pauwels et al.). The chronic inflammatory response may lead to tissue destruction in the lungs (leading to emphysema), and disrupt normal repair (leading to fibrosis of the small airways). Such changes may increase the limitations to airflow limitation, thereby increasing the sensation of breathlessness.

Individuals with COPD typically suffer from a progressive decline in exercise capacity and muscular strength and endurance (Clark et al.) as well as alterations in skeletal muscle morphology, involving a reduction in type I muscle fibers (Eliason et al.), an increased number of senescent satellite cells and an exhausted muscle regenerative capacity, which compromises the maintenance of muscle mass (Thériault et al.), and weight loss (Schols et al.) or cachexia. COPD patients also display a high prevalence of chronic comorbid diseases, including cardiovascular disease (2.4 times), diabetes (1.5 times) and hypertension (1.6 times) even after accounting for confounding factors, including smoking (Mannino et al.).


What is the prevalence of COPD?

While respiratory diseases in general and COPD in particular have been identified as a leading cause of death (after cardiovascular diseases and cancer), the prevalence in the general population is widely regarded as fairly low. However, various researchers have observed that there are significant factors that affect prevalence, including the method of diagnosis, as well as geography, and that the real prevalence might be considerably under-reported. The following table sets out the findings of some of the more recent reviews and larger scale studies:

Study Population Prevalence
Lopez et al. Males aged >30 years in Africa 0.6 – 1.1%
Lopez et al. Females aged >30 years in Africa 0.2 – 0.5%
Lopez et al. Males aged >30 years in the United States 3.4 – 4.0%
Lopez et al. Females aged >30 years in the United States 2.5 – 3.2%
Lopez et al. Males aged >30 years in Europe 1.7 – 3.1%
Lopez et al. Females aged >30 years in Europe 1.5 – 2.2%
Halbert et al. Adults in Europe and North America 4 – 10%
Halbert et al. Adults in the Americas 4.5%
Halbert et al. Adults in Europe 8.3%
Halbert et al. Adults in South-East Asia 12.5%
Halbert et al. Adults in the Western Pacific 10.6%
Halbert et al. Adults >40 years old worldwide 9 – 10%

Based on these studies, the prevalence of COPD can vary widely according to the method of diagnosis, as well as the exact geography. However, prevalence estimates in adults seem to range from 0.2 – 12.5% of the population.


What are the risk factors for COPD?

COPD is widely associated with smoking but exposure to other airborne particular matter as a result of occupation or cooking with biofuels can also be a significant factor. The following table sets out various studies that have identified the risk factors for developing COPD in various populations:

Study Method Finding
Lindberg  et al. The researchers identified the risk factors for incident COPD in a cohort of subjects who already had respiratory symptoms. The researchers found that more advanced age and smoking were significant risk factors for the development of COPD but gender or heredity were not significant risk factors for the development of COPD. Specifically, smoking put males and females at an 3.14 and 8.52 times greater risk of developing COPD, respectively.
De Marco et al. The researchers prospectively assessed the incidence of COPD over a period of 11 years in an international cohort of 5,002 subjects aged 20 – 44 years without asthma and with normal lung function at baseline, in relation to the presence of chronic cough/phlegm. The researchers found that individuals who displayed the presence of chronic cough/phlegm at baseline were 1.85 times more likely to develop COPD, even after controlling for smoking habits and other potential confounders. Additionally, they found that those subjects who reported chronic cough/phlegm both at baseline and at the follow-up had a 2.88 times greater risk of developing COPD.
Silva et al. The researchers prospectively assessed the association between physician-diagnosed asthma and the development of COPD in a cohort of 3,099 adult subjects in the United States over a period of 20 years. The researchers reported that those subjects with active asthma at baseline were 10 times more likely to develop the symptoms of chronic bronchitis, 17 times more likely to incur a diagnosis of emphysema and 12.5 times more likely to develop COPD, even after adjusting for smoking history and other potential confounders.
Meyer and Mannino The researchers set out to describe those factors that were associated with of adults >35 years of age who died of COPD in the United States. They therefore reviewed the features recorded for 12,803 deceased individuals in the National Mortality Follow-back Survey, a nationally representative sample of US deaths in 1993. The researchers reported that individuals dying with COPD were 6.5 times more likely than those dying without COPD to be current smokers. 3.7 times more likely to have been former smokers, 5.0 times more likely to have had a history of asthma, 4.5 times more likely to have been underweight and 3.1 times more likely to have been white, even after controlling for age group and sex.
Eisner et al. The researchers assessed the association between lifetime exposure to environmental tobacco smoke and the risk of developing COPD in a population-based sample of 2,113 adults in the United States, aged 55 – 75 years. The researchers found that a higher cumulative lifetime home and work exposure to environmental tobacco smoke were both associated with a greater risk of COPD. They reported that those individuals in the highest quartile of lifetime home environmental tobacco smoke exposure had a 1.55 times greater risk of developing COPD than those in the lowest quartile. Similarly, the researchers found that those individuals in the highest quartile of lifetime workplace environmental tobacco smoke exposure had a 1.36 times greater risk of developing COPD than those in the lowest quartile.
Hnizdo et al. The researchers assessed the association between COPD and employment by industry and occupation using the US population-based Third National Health and Nutrition Examination Survey, conducted from 1988 – 1994. The researchers found that the risk of developing COPD, even after adjusting for age, smoking status, pack-years of smoking, body mass index (BMI), education and socioeconomic status, was increased for individual who worked in the following industries: rubber, plastics, and leather manufacturing; utilities; office building services; textile mill products manufacturing; the armed forces; food products manufacturing; repair services and gas stations; agriculture; sales; construction; transportation and trucking; personal services; and health care. For example, among females, individuals working in the rubber, plastics, and leather manufacturing industry were 4.7 times more likely to develop COPD, individuals working in the textile mill products manufacturing industry were 2.4 times more likely to develop COPD, and those working in the agriculture industry were 2.0 times more likely to develop COPD.
Trupin et al. The researchers assessed the association between occupation and the risk of developing COPD in a randomly selected sample of 2,061 United States residents aged 55 – 75 years by way of telephone interviews covering respiratory health, general health status and occupational history. The researchers found that after adjusting for smoking status and demography, that individuals who had exposure to at-risk occupations (i.e. those jobs that exposed workers to vapors, gas, dust, or fumes) were 2.0 times more likely to develop COPD than those who were not in at-risk occupations.
Matheson et al. The researchers assessed the association between occupational exposure to different types of dust and the risk of developing COPD as part of a wider cross-sectional study of the risk factors for COPD in a total of 1,232 in adults aged between 45 – 70 years in Melbourne, Australia. They differentiated between biological dusts (including those substances of microbial, plant or animal origin such as bacteria, fungi, allergens, endotoxins, peptidoglycans, pollens and plant fibers), mineral dust and gases/fumes. Occupations commonly exposed to biological dusts include cotton textiles, farmers, grain handlers, bakers and saw mill workers. The researchers reported that those subjects who had ever been exposed to biological dusts had a 2.7 times greater risk of developing COPD and they noted that these risks were higher in women than in men. However, the researchers did not identify any significant increased risks for COPD for exposure to either mineral dust or gases/fumes.
Mastrangelo et al. The researchers performed case–control study in 131 cases of COPD and 298 controls in order to assess the risk factors for developing COPD. After adjusting for age and smoking, the researchers found that farmers were 15.1 times more likely to develop COPD, cotton workers were 7.2 times more likely to develop COPD, welders were 6.4 times more likely to develop COPD, painters were 4.7 times more likely to develop COPD, foundry workers were 12.1 times more likely to develop COPD, refractory workers were 6.50 times more likely to develop COPD, and construction workers were 3.1 times more likely to develop COPD. The researchers also observed that in farmers, cotton workers, welders and painters, the adjusted risk ratios significantly increased (by 6 – 9%) for each extra year of work. Finally, the researchers observed that the risk ratios of developing COPD when working in environments involving high levels of mineral dust, gases/fumes and biological dust were 3.8, 5.8 and 8.9 times, respectively. This suggests that biological dust is much more hazardous than non-biological dust.
Hu et al. The researchers assessed the dose‐response relationship between occupational coke oven emissions exposure and the development of COPD in 712 coke oven workers and 211 controls in southern China. The researchers found that those individuals with the highest level of cumulative coke oven emissions exposure were 5.80 times more likely to develop COPD than controls. The researchers also found that the interaction between coke oven emissions exposure and smoking was significant. They reported that those with the highest cumulative exposure to both coke oven emissions and cigarette smoking were 58 times more likely to develop COPD than those individuals who were both non‐smokers and not exposed to coke oven emissions.
Ulvestad et al. The researchers assessed the occurrence of respiratory symptoms, airflow limitation and COPD in 212 tunnel workers in relation to years of exposure in comparison with a reference group of 205 other heavy construction workers. The researchers found that, in comparison with the reference subjects, the tunnel workers had a prevalence of COPD of 14% while the prevalence of COPD was 8% in the reference subjects. Tunnel workers are therefore at 1.75 times greater risk of developing COPD as a tunnel worker in comparison with a normal construction worker.
Tuechsen and Hannerz The researchers assessed the association between socioeconomic group and occupation in high-risk industries and the risk of developing COPD in cohorts of employed, 20 – 59 year old Danes in the years 1981, 1986, and 1991. The researchers found unskilled male workers were 2.3 times more likely to develop COPD than male senior salaried staff.
Po et al. The reviewers performed a systematic review of studies exploring the associations between exposure to biomass smoke and the risk of developing COPD. They found 25 studies that were suitable for their meta-analysis. The reviewers reported that the overall pooled data indicate that there are significant associations between exposure to biomass smoke and COPD in women and that females regularly exposed to biomass smoke were 2.4 times more likely to develop COPD than those who were not.
Kurmi et al. The researchers performed a systematic review to assess the association between biomass smoke and the development of COPD. They found 23 studies that were suitable for their meta-analysis. The reviewers found that there were positive associations between the use of solid fuels and the development of COPD and that individuals regularly exposed to biomass smoke were 2.8 times more likely to develop COPD than those who were not. They therefore concluded that exposure to wood smoke while performing domestic work presents a greater risk of development of COPD than other fuels.
Hu et al. The researchers performed a systematic review to assess the association between biomass smoke and the development of COPD. They found 15 studies that were suitable for their meta-analysis. The reviewers found that there were positive associations between the use of solid fuels and the development of COPD and that exposure to biomass smoke led to a 2.7 times greater risk of developing COPD in women and a 4.3 times greater risk in men.
Yin et al. The researchers assessed the association between passive smoking and COPD and respiratory symptoms in an adult Chinese population from the Guangzhou Biobank Cohort Study, including 20,430 men and women >50 years old recruited in 2003 – 06 of whom 15,379 were never smokers. The researchers found that there was an association between risk of developing COPD and self-reported exposure to passive smoking at both home and work such that those who were highly exposed (equivalent to 40 hours per week for >5 years) had a 1.48 times greater risk of COPD than those who were not exposed.
Jordan et al. The researchers assessed the association between passive smoking exposure and risk of COPD using a cross-sectional analysis of the 1995, 1996 and 2001 Health Surveys for England that incorporated white subjects aged >40 years with valid lung function data. The researchers found that passive smoke exposure of >20 hours per week was independently associated with a 1.05 times greater risk of developing COPD.
Iribarren et al. The researchers assessed the association between cigarette smoking and the development of COPD in a cohort study of 17,774 men aged 30 – 85 years at base line (from 1964 through 1973) who were enrolled in the Kaiser Permanente health plan and who reported that they had never smoked cigarettes and did not currently smoke a pipe. The researchers followed 1,546 men who smoked cigars and 16,228 men who did not smoke at all from 1971 – 1995 or a first hospitalization for or death from a major cardiovascular disease, COPD or cancer. The researchers found that cigar smokers had a 1.45 times greater risk of developing COPD than non-smokers.
Gan et al. The reviewers performed a systematic review and meta-analysis to assess the associations between COPD and systemic inflammation, as indicated by serum levels of C-reactive protein, fibrinogen, leucocytes, and pro-inflammatory cytokines. The reviewers found that in comparison with healthy controls, individuals with COPD had significantly raised levels of C-reactive protein, fibrinogen, leucocytes, and TNF-a, which are indicative of systemic inflammation. This was observed even among non-current smoker and therefore both the reasons for this systemic inflammation and the direction of causation are unclear. The reviewers note, however, that this association partly clarifies the high prevalence of systemic complications alongside COPD, such as cachexia, osteoporosis and cardiovascular disease.

Based on these studies and reviews, the key risk factors for developing Chronic Obstructive Pulmonary Disease (COPD) seem to be a history of smoking and passive smoking, working in occupations with exposure to dust and fumes (particularly biological dust), exposure to biomass fuels, advanced age, asthma, being underweight and the presence of chronic cough/phlegm.


Can steady-state aerobic exercise help treat COPD?

A number of studies have investigated the use of steady-state aerobic exercise interventions for the treatment of COPD. However, many of them investigate the use of steady-state aerobic exercise in the context of more complex programs of pulmonary rehabilitation. Pulmonary rehabilitation is defined as “an evidence-based, multi- disciplinary and comprehensive intervention for patients with chronic respiratory diseases who are symptomatic and often have decreased daily life activities… pulmonary rehabilitation is designed to reduce symptoms, optimize functional status, increase participation and reduce health-care costs by stabilizing or reversing systemic manifestations of the disease” (Ries). A program of pulmonary rehabilitation typically includes patient assessment, exercise training, education, nutritional intervention and psychosocial support (Ries). The extent to which each of these other factors are able to enhance the effects of the overall program of pulmonary or respiratory rehabilitation is uncertain. What is certain, however, is the beneficial effect that aerobic exercise is able to produce, as the following studies indicate:

Study Method Finding
Casaburi et al. The researchers assessed the effects on exercise tolerance and physiological exercise responses of rehabilitative exercise training in 25 elderly patients with COPD (15 men and 10 women). The subjects took part in a rehabilitation program in which they performed 45-minute sessions of cycle ergometer training, 3 times per week for 6 weeks at maximal possible intensity. Before and after the intervention, the researchers took measurements while the subjects performed an incremental exercise test and a constant work rate test at 80% of peak work rate. The researchers reported that the exercise training led to an average increase in peak work rate in the incremental test of 36% and an increase in the duration of the constant work rate test of 77%. Additionally, during the constant work rate test, the researchers observed that tidal volume was increased by 8% while respiratory rate was decreased by 19%, producing a more efficient exercise breathing pattern.
Maltais et al. The researchers assessed the proportion of 42 elderly patients with moderate-to-severe COPD in whom a 12-week intervention of higher-intensity exercise training was feasible. In this instance, higher-intensity exercise training was defined as 30-minute exercise sessions on a cycle ergometer at 80% of maximal power output. The researchers also assessed the response to higher-intensity exercise training in these patients. Before and after the intervention, the researchers took measurements while the subjects performed an incremental exercise test. The researchers reported that this higher-intensity training was achieved in 0, 3, 5, and 5 of 42 patients in weeks 2, 4, 10, and 12, respectively. However, the researchers observed that in those patients who were able to complete the intervention, there was a significant increase in VO2-max and maximal power output. Nevertheless, they concluded that most patients with moderate-to-severe COPD are unable to achieve the type of higher-intensity training as defined in this study.
Maltais et al. The researchers assessed the skeletal muscle physiological responses to endurance training in 11 elderly patients with moderate-to-severe COPD. The patients performed 30-minute exercise sessions on a calibrated cycle ergometer, 3 times a week for 12 weeks. Before and after the exercise training intervention, the researchers performed a biopsy of the vastus lateralis and the subjects carried out an incremental exercise test up to their maximal capacity while the researchers took measurements. The researchers reported that VO2-max increased significantly by 14% as a result of the training, while lactate threshold and skeletal muscle oxidative capacity were also increased.
Ries et al. The researchers performed a prospective randomised controlled trial in 119 outpatients with COPD. The researchers randomly assigned the subjects to either an 8-week intervention program or to an 8-week education program. The intervention comprised pulmonary rehabilitation comprising twelve 4-hour sessions including education, physical and respiratory care instruction, psychosocial support, and supervised exercise training, followed by monthly reinforcement sessions over a period of 1 year. The education group attended four 2-hour sessions of education but not individual instruction or supervised exercise training. The researchers found that the addition of individual instruction and supervised exercise training to the rehabilitation program led to a significantly greater improvement in maximal exercise tolerance, maximal oxygen uptake, endurance, perceived breathlessness, muscle fatigue, shortness of breath  and self-efficacy for walking.
Hernández et al. The researchers explored the effects on a group of 60 COPD patients of a simple program of home-based walking exercise. The researchers randomly allocated the subjects into 2 groups (rehabilitation and control) of 30 patients each. The rehabilitation group performed a 12-week walking program at 70% of the maximum speed attained on a shuttle walking test, for 1 hour 6 days/week, with a checkup every 2 weeks. The researchers found a significant improvement in functional exercise capacity, as measured by the shuttle walking test. The rehabilitation group improved distance-walked in the shuttle walking test from 1,274 ± 980 to 2,651 ± 2,056m but the control group did not improve this measure significantly. The rehabilitation group also significantly improved dyspnea and quality of life while the control group patients did not.
Goldstein et al. The researchers performed a prospective randomised controlled trial of respiratory rehabilitation in 89 subjects (44 men and 45 women) aged 66 ±7 years with severe but stable COPD. The researchers allocated the subjects to either a treatment group or normal community care. The intervention group received inpatient rehabilitation for 8 weeks and outpatient rehabilitation for 16 weeks. The researchers followed-up over a 24-week period. The researchers found that the respiratory rehabilitation intervention led to significant improvements in 6-minute walk distance (37.9m), submaximal cycle, questionnaire assessment of dyspnea, emotional function and mastery. The researchers therefore concluded that improvements in exercise capacity and health-related quality of life can be achieved and sustained over a 24-week period in individuals with COPD through respiratory rehabilitation.
Lacasse et al. The reviewers performed a meta-analysis of randomised controlled trials of respiratory rehabilitation in patients with COPD in comparison with no-rehabilitation controls. The reviewers defined respiratory rehabilitation as exercise training with or without education and/or psychological support. They included training interventions >4 weeks. They investigated the effects of the exercise training on exercise capacity and health-related quality of life, with the most commonly used measure being the chronic respiratory questionnaire (CRQ), presented on a 7-point scale. The reviewers found 14 trials that could be included in their review. They reported that exercise training for respiratory rehabilitation led to significant improvements for the dyspnea and mastery elements of health-related quality of life and for exercise capacity (as measured by the 6-minute walk test, with an average improvement of 55.7m, and as measured by the incremental cycle ergometer test, with an average improvement of 8.3W). The reviewers concluded that the effects of exercise training for respiratory rehabilitation are clinically important.
Lacasse et al. The reviewers performed a Cochrane review of the effects of pulmonary rehabilitation on health-related quality of life and/or maximal or functional exercise capacity in individuals with COPD by including studies with any in-patient, out-patient, or home-based rehabilitation program of >4 weeks duration that included exercise therapy with or without any form of education and/or psychological support. The reviewers found 31 trials of which 13 assessed health-related quality of life, using 8 different measurement methods. The reviewers considered only 3 of these methods to be valid (i.e. Transitional Dyspnea Index, the Chronic Respiratory Disease Questionnaire (CRQ) and the St Georges Respiratory Questionnaire). In respect of those studies that used the CRQ, the reviewers found that for each of the CRQ domains (dyspnea, fatigue, emotional function and mastery), there was both a statistical and also a clinically significant effect of respiratory rehabilitation. The reviewers found that maximal exercise capacity was assessed by incremental cycle ergometer test in 13 trials and the mean improvement was 8.4 watts. They found that 16 trials assessed functional exercise capacity using the 6-minute walk test and there was a mean improvement of 48m. The reviewers concluded that their results strongly support the use of respiratory rehabilitation of >4 weeks including exercise training for patients with COPD.

Based on these studies and reviews, it seems that aerobic exercise training in individuals with COPD is able to increase tidal volume and reduce respiratory rate, thereby producing a more efficient exercise breathing pattern, as well as improve VO2-max.

Can interval training exercise help treat COPD?

A number of studies have investigated the use of interval training aerobic exercise interventions for the treatment of COPD, as follows:

Study Method Finding
Coppoolse et al. The researchers compared the effects of either steady-state or interval training in 21 patients with COPD. The researchers randomly allocated the subjects to steady-state or interval training groups. In both cases, the exercise training was performed on a cycle ergometer, 5 days a week, for 30 minutes per day for the same total workload. The steady-state training group trained continuously at 60% of maximum work rate. The interval training group performed 3 days of similar continuous training and 3 days of interval training, which comprised of 9 blocks of 3 minutes. Each block comprised 1 minute at 90% and 2 minutes at 45 of maximum work rate. The researchers reported that the steady-state training group displayed a significant increase of 17% in VO2-max but no similar change was observed following interval training. The researchers found that lactic acid production was significantly reduced in both groups but was greater in the steady-state than in the interval training group (31% vs. 20%). However, only the interval training group significantly increased maximum work load (by 17%) and decreased leg pain.
Vogiatzis et al. The researchers compared steady-state and interval training for generating physiological improvements in 36 COPD patients. The researchers randomly assigned the subjects to either steady-state (continuous exercise at 50% of maximum work rate) or interval training (30 seconds at 100% of maximum work rate alternating with 30-second rest intervals) groups. Both groups performed the exercise training on cycle ergometers for 40 minutes per day, 2 days per week for 12 weeks. Before and after the exercise intervention, the researchers took various measurements during exercise testing as well as of quality of life, as defined by the Chronic Respiratory Disease Questionnaire (CRDQ). The researchers reported that both groups displayed significantly improved maximum work rate, by 14W and 13W (25 and 23%) in the interval and steady-state groups, respectively. They also observed a trend towards improvement in VO2-max in both groups. Finally, the researchers observed a similar, significant improvement in quality of life, as defined by the CRDQ overall score in both groups, by 14% and 19% in the interval and steady-state groups, respectively.
Vogiatzis et al. The researchers performed a 10-week, randomized controlled study to compare the effects of interval training with steady-state changing on the morphologic and biochemical characteristics of the vastus lateralis muscle in 19 patients with stable advanced COPD. The interval training group exercised at a mean intensity of 124 ± 15% of maximum work rate for 30-second work periods alternating with 30-second rest periods for 45 minutes per day, 3 times per week, while the steady-state group exercised at a mean intensity of 75 ± 5% of maximum work rate for 30 minutes per day, 3 times per week. Before and after the exercise intervention, the researchers took muscle biopsies of the right vastus lateralis. The researchers reported that in the interval training group, maximum work rate and lactate threshold increased significantly, type I and IIa fiber cross-sectional area increased significantly, capillary-to-fiber ratio increased significantly, and citrate synthase activity displayed an increasing trend. However, there were no significant differences between the steady-state and interval training groups in these improvements. Finally, the researchers observed that ratings of dyspnea and leg discomfort were significantly reduced as a result of the intervention in the interval training group in comparison with the steady-state group.
Puhan et al. The researchers performed a randomized, non-inferiority trial in order to assess whether interval exercise as effective as high-intensity steady-state exercise and whether it is tolerated better by 98 patients with severe COPD. The researchers randomly allocated the subjects into either an interval training group or a steady-state group who each performed 12 – 15 supervised exercise sessions over 3 weeks followed by exercise at home for a further 9 weeks. The steady-state group performed cycle ergometer exercise at a workload of >70% of maximum exercise capacity for 20 minutes. The interval group also performed cycle ergometer exercise for 20 minutes but alternated between high-intensity intervals lasting 20 seconds at a workload of 90 – 100% of maximum exercise capacity and low-intensity intervals lasting 40 seconds. The researchers assessed physiological improvements as a result of the exercise programs as well as health-related quality of life as measured by Chronic Respiratory Questionnaire (CRQ) scores. The researchers reported that both interval and steady-state exercise groups displayed large improvements in exercise capacity and health-related quality of life (as measured by CRQ scores) but that the interval training group adhered statistically significantly better to the protocol than the steady-state group (47.9% vs. 24.0%).
Arnardóttir et al. The researchers compared the effects of interval training and steady-state training on maximum work rate, physiological responses, functional capacity, dyspnea (as measured by the dyspnea scale on the Chronic Obstructive Disease Questionnaire), mental health (as measured by the Hospital Anxiety and Depression scale) and health-related quality of life in 60 patients with moderate-to-severe COPD. The researchers randomly allocated the subjects to exercise twice weekly for 16 weeks using either interval- or steady-state training methods on a cycle ergometer. The interval training group performed intervals of 3 minutes at 80% of maximum work rate while the steady-state group exercises continuously at 65% of maximum work rate. The researchers reported that maximum work rate, VO2-max, functional capacity, dyspnea, mental health, and health-related quality of life all increased significantly in both groups but there was no significant differences between the groups.
Beauchamp et al. The reviewers performed a meta-analysis of randomised controlled trials that compared the effects of interval and steady-state training exercise capacity and health-related quality of life in patients with COPD. The reviewers found 8 randomised controlled trials. While the exercise interventions did lead to significant improvements in both exercise capacity and health-related quality of life, the reviewers did not detect any differences in the improvements made by each type of intervention for peak power, peak oxygen uptake, Chronic Respiratory Questionnaire dyspnea score or 6-minute walk test performance. They therefore concluded that interval training is a suitable alternative to steady-state training in COPD patients with varying degrees of disease severity.
Kortianou et al. The reviewers performed a systematic review of studies investigating the effectiveness of interval training in the treatment of COPD. The reviewers observed that while both intensity and duration of exercise are important determinants of the physiological adaptations that occur following training, COPD patients are often thought to be prevented from performing high-intensity training because of their symptoms. However, the reviewers therefore note that interval training may permit exercise to be sustained at a high-intensity in patients with COPD which otherwise would not be tolerable, thereby achieving a physiological training effect because of ventilatory limitation with lower symptoms of dyspnea and leg discomfort. Indeed, they note that studies have shown training in patients with severe COPD to be associated with stable metabolic demands, low minute ventilation and rates of dynamic hyperinflation, and increased total exercise duration than steady-state exercise. The reviewers therefore concluded that interval training has important clinical benefits for the treatment of COPD.

Based on these interventions, interval training appears able to improve lactate threshold, maximum work load and quality of life in patients with COPD.


Can resistance training exercise help treat COPD?

A small number of studies have investigated the use of resistance training exercise interventions for the treatment of COPD, as follows:

Study Method Finding
Bernard et al. The researchers assessed whether resistance training is a useful addition to aerobic training in 45 patients with moderate-to-severe COPD. The researchers randomly allocated the subjects to either 12 weeks of aerobic training alone or in combination with resistance training. The aerobic training exercise comprised 3 weekly 30-minute exercise sessions on a cycle ergometer and the resistance training exercise included 3 sets of 8 – 10 repetitions of 4 exercises. Before and after the intervention, the researchers muscular strength, thigh muscle cross-sectional area, maximal exercise capacity, 6-minute walking distance and quality of life as defined by the Chronic Respiratory Disease Questionnaire (CRDQ). The researchers reported that quadriceps femoris strength increased significantly in both groups but the improvement was greater in the resistance training group (20 ± 12% vs. 8 ± 10%). They observed that thigh muscle cross-sectional area increased significantly only in the resistance training group. They noted that improvements in the other variables were similar in both groups.
Simpson et al. The researchers assessed whether resistance training techniques are helpful in a sample of 34 patients with COPD. The researchers randomly allocated the subjects to a control or resistance training group. The researchers reported that the resistance training group displayed a significant increase of 73% in duration during a constant work rate cycle ergometer test at 80% of maximum power output whereas control subjects displayed no increase. However, the researchers observed no changes in either maximum cycle ergometer exercise capacity during an incremental test nor 6-minute walking distance in either group. Finally, the researchers observed that in response to the Chronic Respiratory Disease Questionnaire (CRDQ), the resistance training group displayed significant improvements in dyspnea and activities of daily living.
Spruit et al. The researchers compared the effects of resistance training and endurance training in 48 patients with moderate-to-severe COPD in addition to peripheral muscle weakness (as measured by a isometric knee extension peak torque value of 75% of predicted value). The researchers randomly allocated the subjects to either a resistance training group or to an endurance training group. The resistance training group performed progressive, machine-based resistance-training exercises, 3 times per week, starting with 70% of 1RM for 3 sets of 8 repetitions. The latter endurance training group performed walking, cycling and arm cranking starting with 10 minutes at 30% of maximum work rate and increasing with a goal of 25 minutes at 75% of maximum work rate. The researchers reported that both groups displayed significant increases in peak knee extension torque, maximal knee flexion torque, elbow flexion torque, 6-minute walking distance, maximum workload, and health-related quality of life but there were no significant differences between the groups.
Kongsgaard et al. The researchers assessed the effects of resistance training in 18 elderly males with COPD. The researchers randomly allocated the subjects to either a resistance training group or to a control group who performed breathing exercises. The resistance training group performed heavy progressive resistance training 2 times per week for 12 weeks. The researchers reported that the resistance training group displayed significant increases in quadriceps cross-sectional area of 4%, significant increases in isometric knee extension torque of 14%, significant increases isokinetic knee extension torque at 60 degrees/s of 18%, significant increases in leg extension power of 19%, significant increases in maximal gait speed of 14%, significant increases in stair climbing time of 17%, and significant increases in self-reported health. However, there were no changes in the control group.
Wright et al. The researchers assessed the effects of a resistance training program on various parameters relevant to COPD in 28 patients with moderate-to-severe COPD. The researchers randomly allocated the subjects to either a resistance training group or to a control group. The resistance training group performed a resistance training program for 12 weeks, initially 2 times, then 3 times a week. The researchers observed an increase in maximum work rate on the cycle ergometer in the resistance training group of 18.7% but no significant change was found in the control group. The researchers also observed a significant improvement in health-related quality of life in the resistance training group but not in the control group.
Clark et al. The researchers performed a randomized controlled trial to assess the effects of a 12-week hospital outpatient resistance-training program on skeletal muscle function and exercise tolerance. The researchers recruited 43 patients with COPD and randomly allocated them into either a training or a control group. The training group attended the hospital 2 times per week and performed a warm-up of either cycling or treadmill walking followed by 3 sets of 10 reps of 8 resistance-training exercises, as follows: bench press, squat, calf raise, lat-pull down, curl, leg press, and leg curl. The subjects performed these exercises with 70% of 1RM. The researchers found that the subjects displayed significant increases in the maximum weight lifted in 4 of the 5 lower body exercises and 1 of the 3 upper body exercises, significant improvements in the sustained 1-minute test of isokinetic muscle work in both upper and lower limbs and mean endurance performance on the treadmill.
Nakamura et al. The researchers assessed how adding either resistance-training or recreational activities to aerobic training would affect 33 patients with moderate-to-severe COPD during a 12-week rehabilitation period. The researchers randomly assigned the subjects to either a control group, an aerobic training and strength training group, or an aerobic training and recreational activities group. In both training groups, the aerobic regimen comprised bouts of 20-minute walking sessions, 3 times per week. In addition, the resistance-training group performed 3 sets of 10 reps of 4 exercises and the recreational activities group trained using exercise balls to improve activities of daily living. Before and after the intervention, the researchers measured muscular strength and endurance, cardiorespiratory fitness, 6-minute walking distance test performance, and quality of life using the Short Form 36 questionnaire (SF-36). The researchers observed that the resistance-training group significantly increased grip strength (8.3%), VO2-max (5.1%) and health-related quality of life physical functioning score (7.9%). However, the recreational activities group displayed significant improvements in social functioning (9.4%) and mental health (12.2%). The researchers therefore concluded that both forms of training are effective for adding to aerobic training in order to enhance the benefits of aerobic training.
Franssen et al. The researchers assessed the effects of 8 weeks of combined exercise training on body composition, maximal exercise capacity and muscular strength in 50 patients with COPD. The patients performed a standardized inpatient exercise training program comprising daily submaximal cycle ergometry, treadmill walking, resistance-training, and gymnastics over an 8-week period. Before and after the intervention, the researchers measured fat-free mass, maximal exercise capacity using incremental cycle ergometry and muscular strength using an isokinetic knee extension dynamometer. The researchers found that after the 8-week period, bodyweight significantly increased as a result of increased fat-free mass (from 52.4 ± 7.3 to 53.4 ± 7.7kg). There was no significant increase in fat mass. The researchers also observed increases in VO2-max (from 1,028 ± 307 to 1,229 ± 421mL/min) and isokinetic quadriceps strength (82.5 ± 36.4 to 90.3 ± 34.9Nm).
Franssen et al. The researchers assessed the effects of 8 weeks of combined exercise training on body composition, maximal exercise capacity and muscular strength in in 59 COPD patients with preserved fat-free mass relative to age- and sex-matched healthy control subjects and in 28 COPD patients with reduced fat-free mass relative to age- and sex-matched healthy control subjects. The exercise training program involved both aerobic exercise and resistance-training. The aerobic exercise comprised cycle ergometry, 2 times per day for 20 minutes, at 50 – 60% of baseline peak work rate. The resistance-training involved 30 minutes of gymnastics and 10 minutes of unsupported arm exercise per day. The researchers reported that the exercise training led to significant improvements in muscular strength and endurance of the quadriceps muscle but not of the biceps muscle. The researchers also reported significant improvements in both bodyweight and fat-free mass (1.8 ± 0.3kg and 1.5 ± 0.3kg, respectively) but not in fat mass. Significant improvements in peak cycling work rate (15 ± 2W) were reported, indicating an increased exercise capacity.
Mador et al. The researchers performed a randomized trial to compare the effects of endurance training only with endurance and strength training combined in 24 patients with COPD. The researchers randomly allocated the subjects into either an endurance-only or a combined training group. The researchers reported that the combined training led to significant improvements in quadriceps (23.6%), hamstring (26.7), pectoralis major (17.5%), and latissimus dorsi (20%) muscle strength and this increase in strength was significantly greater in the combined group compared to the endurance group for the quadriceps and latissimus dorsi muscles but not for the hamstring and pectoralis major muscles. The researchers also reported that 6-minute walk distance, endurance exercise time, and quality of life (as measured by the Chronic Respiratory Questionnaire) significantly increased in both groups and there was no significant difference between groups.

Based on these studies, it seems that resistance training can improve dyspnea, activities of daily living, strength, 6-minute walking distance, maximum workload, and health-related quality of life in individuals with COPD.

 


Can inspiratory muscle training exercise help treat COPD?

A small number of studies have investigated the use of inspiratory muscle training exercise interventions for the treatment of COPD, as follows:

Study Method Finding
Sturdy et al. The researchers assessed the feasibility of high-intensity respiratory muscle training in 9 subjects with moderate-to-severe COPD over an 8-weeks period. The intervention comprised progressive, interval-based respiratory muscle training combined with a general exercise program, for 3 sessions of 20-minutes per week, with each session comprising 7 sets of 2-minute bouts of breathing against a constant inspiratory threshold load, with 1 minute of recovery in between. The researchers reported that respiratory muscle strength increased by 32 ± 27% while respiratory muscle endurance increased by 56 ± 33% as a result of the intervention.
Lötters et al. The reviewers performed a meta-analysis to assess the effects of inspiratory muscle training for patients with COPD, either using targeted resistive training or training with a threshold loading device. The reviewers identified 15 studies for which data was available for their meta-analysis. The reviewers found that inspiratory muscle training exercise interventions had significant effects on inspiratory muscle strength, inspiratory muscle endurance and dyspnea. They also observed that there was a trend towards an effect on functional exercise capacity but this did not reach statistical significance. The reviewers observed that no meta-analysis was performed on health-related quality of life, as different outcome measures were used, which made it difficult to summarize the findings. The reviewers observed that the type of inspiratory muscle training used (whether targeted resistive training or training with a threshold loading device) did not affect the outcomes.
Geddes et al. The reviewers performed a meta-analysis to assess the effects of inspiratory muscle training on inspiratory muscle strength and endurance, exercise capacity, dyspnea and quality of life in patients with COPD, either using targeted resistive training or training with a threshold loading device. The reviewers identified 13 studies for which data was available for their meta-analysis. The reviewers found that both types of inspiratory muscle training were associated with significant improvements in inspiratory muscle strength and endurance, exercise capacity, maximum work rate, and dyspnea. The researchers did not find any conclusive evidence for the use of inspiratory muscle training in relation to quality of life.

Based on these studies and reviews, it appears that inspiratory muscle training exercise can significantly increase inspiratory muscle strength, inspiratory muscle endurance, exercise capacity, maximum work rate, and dyspnea, which may be beneficial for individuals with COPD.


Evidence-based recommendations for exercise

Some reviews have made evidence-based recommendations for the treatment of COPD that include non-pharmacological treatments.

Study Recommendation
Gosselink et al. The reviewers observe that the consequences of reduced exercise capacity are central to those suffering from COPD, leaving them disabled, out of work, socially isolated, heavily utilizing healthcare resources and with a greater mortality rate. They conclude that exercise training is an important part of respiratory rehabilitation programmes in COPD patients, as it leads to both increased maximal exercise capacity and greater functional exercise performance. The reviewers conclude that low-intensity exercise leads to modest improvements in submaximal exercise tests but no increases in maximal exercise performance, while high-intensity training improves both maximal and submaximal exercise test performance and causes both cardiorespiratory and peripheral muscle adaptations. They note that studies have found high-intensity exercise training to be both possible and safe in COPD patients.
Gloeckl et al. The reviewers observe that pulmonary rehabilitation is one of the most efficacious non-pharmacological treatments for COPD and have the potential to improve a patients exercise tolerance, reduce symptoms of dyspnoea and improve health-related quality of life.  The reviewers recommend steady-state exercise consisting initially of 10 – 15 minutes progressing to 30 – 40 minutes at moderate intensity (60 – 70% of peak work rate) progressing 5 – 10% as tolerated, or aiming for a perceived exertion of 4 – 6 on the Borg scale 3 – 4 days/week. Alternatively, they recommend interval training consisting initially of 15 – 20 minutes progressing to 45 – 60 minutes (including rest time) sequenced with bouts of work and rest of 30 seconds work and 30 seconds rest, or 20 seconds work and 40 seconds rest, initially at 80 – 100% intensity and progressing by 5 – 10% as tolerated up to 150% of peak work rate 3 – 4 days/week. The reviewers note that strength training should be included alongside aerobic training and should comprise 2 – 4 sets of 6 – 12 exercises at 50 – 85% of 1RM, or to achieve muscular exhaustion between 6 – 12 repetitions, 2 – 3 days/week.
Ries The reviewer provides a summary of the evidence-based guidelines in respect to the treatment of COPD. Some of these guidelines involve exercise training. The practical guidelines indicate that exercise training for the leg muscles should be performed, that 6 – 12 weeks of pulmonary rehabilitation produces benefits but the benefit reduces gradually over 12 – 18 months, that programs of pulmonary rehabilitation >12 weeks produce greater sustained benefits than programs <12 weeks, that “top-up” exercise following initial periods of pulmonary rehabilitation have a modest but beneficial effect on long-term outcomes, that high-intensity lower body exercise training produces greater physiological adaptations than low-intensity training (but both low-intensity and high-intensity exercise training produce clinical benefit), that a strength-training component increases muscle strength and muscle mass, that endurance training of the upper body should be included, and that inspiratory muscle training is not an essential component of pulmonary rehabilitation.
Cooper The reviewer concluded that a program of structured aerobic exercise lasting >6 weeks using the leg muscles is clearly the most effective component of rehabilitation for patients with COPD and will likely lead to improved exercise capacity and relief from dyspnea.

Based on these guidelines, exercise training is recommended in normal treatment for COPD, with initial rehabilitation periods of >12 weeks involving high-intensity lower body aerobic exercise and strength-training interventions. The recommended initial approach for interval training starts with 15 – 20 minutes of 30 seconds work and 30 seconds rest at 80 – 100% intensity 3 – 4 days/week, while strength training should comprise 2 – 4 sets of 6 – 12 exercises at 50 – 85% of 1RM, 2 – 3 days/week.


Conclusions

On the basis of these studies and reviews, the following conclusions might be drawn:

Area Conclusion
There are a number of environmental risk factors for COPD The key risk factors for developing COPD seem to be a history of smoking and passive smoking, working in occupations with exposure to dust and fumes (particularly biological dust), exposure to biomass fuels, advanced age, asthma, being underweight and the presence of chronic cough/phlegm.
COPD is highly prevalent The prevalence of COPD can vary widely according to the method of diagnosis, as well as the exact geography. However, prevalence estimates in adults seem to range from 0.2 – 12.5% of the population.
Most key risk factors for COPD are well-known The key risk factors for developing COPD seem to be a history of smoking and passive smoking, working in occupations with exposure to dust and fumes (particularly biological dust), exposure to biomass fuels, advanced age, asthma, being underweight and the presence of chronic cough/phlegm.
Aerobic exercise helps individuals with COPD Aerobic exercise training in individuals with COPD is able to increase tidal volume and reduce respiratory rate, thereby producing a more efficient exercise breathing pattern, as well as improve VO2-max.
Interval training helps individuals with COPD Interval training appears able to improve lactate threshold, maximum work load and quality of life in patients with COPD.
Resistance training helps individuals with COPD Resistance training can improve dyspnea, activities of daily living, strength, 6-minute walking distance, maximum workload, and health-related quality of life in individuals with COPD.
Inspiratory muscle exercise helps individuals with COPD Inspiratory muscle training can significantly increase inspiratory muscle strength, inspiratory muscle endurance, exercise capacity, maximum work rate, and dyspnea, which may be beneficial for individuals with COPD.
Guidelines for exercise in COPD are detailed Exercise training is recommended in normal treatment for COPD, with initial rehabilitation periods of >12 weeks involving high-intensity lower body aerobic exercise and strength-training interventions. The recommended initial approach for interval training starts with 15 – 20 minutes of 30 seconds work and 30 seconds rest at 80 – 100% intensity 3 – 4 days/week, while strength training should comprise 2 – 4 sets of 6 – 12 exercises at 50 – 85% of 1RM, 2 – 3 days/week.

In summary, aerobic exercise, interval-training, resistance-training and inspiratory muscle training can all be used to help individuals with COPD improve their breathing, fitness, exercise capacity and health-related quality of life.


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