[Peripheral muscle dysfunction in chronic obstructive pulmonary disease]

Patients with chronic obstructive pulmonary disease (COPD) often develop systemic complications of their disease. Peripheral muscle dysfunction is one such complication and is characterised by atrophy, weakness, and low oxidative capacity. These muscle changes influence exercise tolerance and quality of life independent of the impairment in lung function. In the following article, the evidence for peripheral muscle dysfunction in patients with COPD and the possible clinical implications of this problem will be discussed. Lastly, the available therapeutic options to improve peripheral muscle function in COPD will be reviewed.

21st century perspective on chronic obstructive pulmonary disease

The prediction that chronic obstructive pulmonary disease (COPD) will be the third leading cause of death worldwide by 2020 has enormous economic repercussions. Yet many issues and questions remain unresolved. For example, how can population studies of morbidity and mortality be viewed as comparable, without a worldwide consensus on the definition of COPD? How can the early diagnosis of COPD be improved? Why is it that only a minority of smokers develop COPD, despite tobacco smoking being the primary risk factor for chronic bronchitis and emphysema? How can the efficacy of smoking cessation interventions be improved? To what extent are the pathologic changes in the lungs reversible - and, if so, at what stage? And to what degree is it appropriate to emphasize the similar features of COPD and asthma? It is to be hoped that the emerging post-genomic and proteomic climate will facilitate the unlocking of the genetic substrate for COPD, and thus promote greater therapeutic specificity and efficacy.

A long-term evaluation of once-daily inhaled tiotropium in chronic obstructive pulmonary disease

Currently available inhaled bronchodilators used as therapy for chronic obstructive pulmonary disease (COPD) necessitate multiple daily dosing. The present study evaluates the long-term safety and efficacy of tiotropium, a new once-daily anticholinergic in COPD. Patients with stable COPD (age 65.2+/-8.7 yrs (mean+/-SD), n=921) were enrolled in two identical randomized double-blind placebo-controlled 1-yr studies. Patients inhaled tiotropium 18 microg or placebo (mean screening forced expiratory volume in one second (FEV1) 1.01 versus 0.99 L, 39.1 and 38.1% of the predicted value) once daily as a dry powder. The primary spirometric outcome was trough FEV1 (i.e. FEV1 prior to dosing). Changes in dyspnoea were measured using the Transition Dyspnea Index, and health status with the disease-specific St. George's Respiratory Questionnaire and the generic Short Form 36. Medication use and adverse events were recorded. Tiotropium provided significantly superior bronchodilation relative to placebo for trough FEV1 response (approximately 12% over baseline) (p<0.01) and mean response during the 3 h following dosing (approximately 22% over baseline) (p<0.001) over the 12-month period. Tiotropium recipients showed less dyspnoea (p<0.001), superior health status scores, and fewer COPD exacerbations and hospitalizations (p<0.05). Adverse events were comparable with placebo, except for dry mouth incidence (tiotropium 16.0% versus placebo 2.7%, p<0.05). Tiotropium is an effective, once-daily bronchodilator that reduces dyspnoea and chronic obstructive pulmonary disease exacerbation frequency and improves health status. This suggests that tiotropium will make an important contribution to chronic obstructive pulmonary disease therapy.

Testosterone dose-response relationships in healthy young men

Testosterone increases muscle mass and strength and regulates other physiological processes, but we do not know whether testosterone effects are dose dependent and whether dose requirements for maintaining various androgen-dependent processes are similar. To determine the effects of graded doses of testosterone on body composition, muscle size, strength, power, sexual and cognitive functions, prostate-specific antigen (PSA), plasma lipids, hemoglobin, and insulin-like growth factor I (IGF-I) levels, 61 eugonadal men, 18-35 yr, were randomized to one of five groups to receive monthly injections of a long-acting gonadotropin-releasing hormone (GnRH) agonist, to suppress endogenous testosterone secretion, and weekly injections of 25, 50, 125, 300, or 600 mg of testosterone enanthate for 20 wk. Energy and protein intakes were standardized. The administration of the GnRH agonist plus graded doses of testosterone resulted in mean nadir testosterone concentrations of 253, 306, 542, 1,345, and 2,370 ng/dl at the 25-, 50-, 125-, 300-, and 600-mg doses, respectively. Fat-free mass increased dose dependently in men receiving 125, 300, or 600 mg of testosterone weekly (change +3.4, 5.2, and 7.9 kg, respectively). The changes in fat-free mass were highly dependent on testosterone dose (P = 0.0001) and correlated with log testosterone concentrations (r = 0.73, P = 0.0001). Changes in leg press strength, leg power, thigh and quadriceps muscle volumes, hemoglobin, and IGF-I were positively correlated with testosterone concentrations, whereas changes in fat mass and plasma high-density lipoprotein (HDL) cholesterol were negatively correlated. Sexual function, visual-spatial cognition and mood, and PSA levels did not change significantly at any dose. We conclude that changes in circulating testosterone concentrations, induced by GnRH agonist and testosterone administration, are associated with testosterone dose- and concentration-dependent changes in fat-free mass, muscle size, strength and power, fat mass, hemoglobin, HDL cholesterol, and IGF-I levels, in conformity with a single linear dose-response relationship. However, different androgen-dependent processes have different testosterone dose-response relationships.

Dose-response effect of oxygen on hyperinflation and exercise endurance in nonhypoxaemic COPD patients

Dynamic hyperinflation contributes to exertional breathlessness and reduced exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. This study examined whether oxygen supplementation results in a dose-dependent decrease in hyperinflation associated with functional and symptomatic improvement. Ten severe COPD patients without clinically significant oxygen (O2) desaturation during exercise, and seven healthy subjects, performed five exercise tests at 75% of maximally tolerated work rate. Inspired oxygen fraction (FI,O2) was varied (0.21, 0.3, 0.5, 0.75 and 1.0) among tests in a randomized order. Ventilation (V'E) was measured, and end-inspiratory (EILV) and end-expiratory (EELV) lung volume changes were assessed from inspiratory capacity manoeuvres. In the patients, compared to room air, endurance time increased with FI,O2=0.3 (mean+/-SEM 92+/-20%) and increased further with FI,O2=0.5 (157+/-30%). At isotime, compared to room air, there were significant reductions in dyspnoea score, EELV, EILV, V'E and respiratory frequency (fR) with FI,O2=0.3. Improved endurance time negatively correlated with change in EELV (r=0.48, p=0.002) and EILV (r=0.43, p=0.005). The dyspnoea rating decrease correlated with fR decrease. In healthy subjects, smaller V'E and fR decreases were observed at FI,O2=0.5, accompanied by more modestly increased endurance. Oxygen supplementation during exercise induced dose-dependent improvement in endurance and symptom perception in nonhypoxaemic chronic obstructive pulmonary disease patients, which may be partly related to decreased hyperinflation and slower breathing pattern. This effect is maximized at an inspired oxygen fraction of 0.5.

Skeletal muscle dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major health care problem. Formerly mainly a disease of men, women are increasingly frequently afflicted. In many of these patients, exercise intolerance is the chief complaint. Few effective therapies are available. In recent years, dysfunction of the muscles of ambulation has been identified as a source of a portion of the exercise intolerance these patients experience, and this dysfunction has been shown to be, at least in part, remediable. Mechanisms inducing muscle dysfunction include disuse atrophy, malnutrition, low levels of anabolic steroids, and myopathy from corticosteroid use. Endurance exercise training has been conclusively demonstrated to improve exercise tolerance in COPD. Recent studies suggest that strength training is beneficial as well. A new frontier of therapy for muscle dysfunction in COPD is the use of anabolic hormones. Testosterone supplementation has been shown to increase muscle mass and strength in both hypogonadal and eugonadal healthy men. Low-dose testosterone supplementation is being considered for use in postmenopausal women. Though short-term administration of testosterone in moderate doses seems to be well tolerated in both men and women, further studies are required before safety and effectiveness can be established for routine use in COPD patients.

Peripheral muscle dysfunction in chronic obstructive pulmonary disease

Peripheral muscle dysfunction is a common systemic complication of moderate to severe COPD and may contribute to disability, handicap, and premature mortality. In contrast to the lung impairment, which is largely irreversible, peripheral muscle dysfunction is potentially remediable with exercise training, nutritional intervention, oxygen, and anabolic drugs. Therapeutic success is often incomplete, however, and a better understanding of the mechanisms involved in the development of peripheral muscle dysfunction in COPD is needed to help develop innovative and more effective therapeutic strategies.

The spirometric efficacy of once-daily dosing with tiotropium in stable COPD: a 13-week multicenter trial. The US Tiotropium Study Group

STUDY OBJECTIVE

To compare the bronchodilator efficacy and safety of tiotropium and placebo.

DESIGN

A 3-month, randomized, double-blind, placebo-controlled, multicenter trial.

SETTING

Outpatient.

PATIENTS

Four hundred seventy patients with stable COPD (mean FEV(1) = 38.6% predicted).

INTERVENTIONS

Tiotropium 18 microg (N = 279) or placebo (N = 191) given once daily via a lactose-based dry-powder inhaler device.

MEASUREMENTS AND RESULTS

Spirometry was evaluated on days 1, 8, 50, and 92. Data were expressed as the mean trough (ie, before morning dose; 23 to 24 h after previous dose) and average response observed in the 3 h after the dose was received. Tiotropium produced significant improvement in trough FEV(1) and FVC, averaging 12% greater than baseline on day 8; these improvements were maintained on days 50 and 92. The average postdose FEV(1) was 16% greater than baseline on day 1 and 20% greater than baseline on day 92; FVC was 17% greater than baseline on day 1 and 19% greater than baseline on day 92. Tiotropium was significantly more effective than placebo in both trough and average FEV(1) and FVC response (p < 0.001). These spirometric effects were corroborated by significant improvements in daily morning and evening peak expiratory flow rate, as well as a reduction in "as-needed" albuterol use. Symptoms of wheezing and shortness of breath were significantly less in patients receiving tiotropium, and the physician global assessment noted overall improvements with those treated with tiotropium relative to placebo. The most common reported adverse event after tiotropium was dry mouth (9.3% vs 1.6% relative to placebo; p < 0.05).

CONCLUSIONS

These data demonstrate that tiotropium is a safe and effective once-daily anticholinergic bronchodilator and should prove useful as first-line maintenance therapy in COPD.

Recommendations of the Fifth Oxygen Consensus Conference. Writing and Organizing Committees

It should be recognized that the advent of LTOT created a new health care system that is based on powerful scientific data. Oxygen therapy studies such as those by the Nocturnal Oxygen Therapy Trial Group and the British Medical Research Council study clearly demonstrated that LTOT improves both the length and quality of life of hypoxemic COPD patients. Keeping patients at home and out of the hospital or nursing home has both psychosocial and economic benefits. Efforts should be towards enhancing, not limiting., the availability of LTOT.

Influence of work rate incremental rate on the exercise responses in patients with COPD

PURPOSE

The peak work rate (Wpeak) measured during a progressive stepwise exercise test is commonly used to select the target training intensity for an exercise training program. In healthy subjects, a greater Wpeak is achieved when a faster rate of increase in work rate is used, whereas VO2 peak is independent of the rate of increase in work rate. This effect might be even more pronounced in chronic obstructive pulmonary disease (COPD) patients, in whom the VO2 kinetics during exercise are slower compared with healthy subjects.

METHODS

To investigate this, we studied 10 COPD patients (9 M/1 F, age: 65+/-5 yr [mean +/- SD], FEV1: 33+/-8%). They underwent, on separate days, three stepwise exercise tests on an ergocycle. For each test, increments of 5, 10, or 20 W x min(-1) were used in random order; the investigator was blinded as to which increment was used. VO2, VCO2, heart rate (HR), minute ventilation (VE), breathlessness and leg fatigue at rest, at each work rate, and at maximal capacity were obtained.

RESULTS

Wpeak averaged 40+/-13, 53+/-14, and 66+/-19 W for the 5-, 10-, and 20-W protocol, respectively (P < 0.001), whereas VO2 peak was comparable at 0.96+/-0.16, 1.02+/-0.18, and 1.03+/-0.20 L x min(-1). As the rate of increase in work rate became faster, the VO2/work rate relationship shifted to the right. This is exemplified by the VO2 at 40 W, which averaged 0.98+/-0.06, 0.90+/-0.09, and 0.83+/-0.10 L x min(-1) for the 5-, 10-, and 20-W protocol, respectively (P < 0.05). Similar observations were made for the relationship between HR, VE, and symptom scores, and work rate. There was no significant differences in peak values for HR and VE, and symptoms scores.

CONCLUSIONS

We conclude that the work rate incremental rate influences the Wpeak achieved, whereas the peak values for VO2, HR, VE, and symptom scores remain comparable. These findings have practical implications for the exercise evaluation of patients with COPD.

Skeletal muscle function in COPD

Few effective therapies exist for patients with COPD. Rehabilitative therapy aimed at curing dysfunction of the peripheral muscles may be an appropriate addition to this short list. This review does the following: (1) presents evidence that skeletal muscle dysfunction is present in COPD patients; (2) considers the mechanisms of this dysfunction; (3) describes the role of exercise training in correcting this disorder; and (4) speculates that anabolic hormone supplementation may find a place in COPD therapy. Further research will be necessary to refine these concepts.

Comparison of effects of supervised versus self-monitored training programmes in patients with chronic obstructive pulmonary disease

The effects of two 8 week programmes of reconditioning in chronic obstructive pulmonary disease (COPD) patients were studied. Forty one subjects (mean+/-SD) 644.5) yrs; forced expiratory volume in one second (FEV1) 1.09+/-0.16 L; 40.6+/-6.2% predicted were randomly assigned either to supervised training on a treadmill, 4 days x week(-1) (group S; n=21) or walking 3 or 4 km in 1 h 4 days x week(-1), self-monitored with a pedometer, with weekly visits to encourage adherence (group SM; n=20). Patients were evaluated with the chronic respiratory diseases questionnaire (CRQ) and two exercise tests on a treadmill: incremental (IT) and constant (CT), above lactic threshold or 70% of maximal oxygen uptake (VO2, max) with arterial blood lactate determinations. Estimated mean work rate of training was 69+/-27 W and 25+/-5 W respectively for groups S and SM. Both types of training produced similar changes in the four dimensions of the CRQ. In group S reconditioning yielded significant (p<0.05) increases in VO2, max and increases in duration, with decreased lactate accumulation, ventilation, CO2 output (VCO2), heart rate (HR) and diastolic blood pressure (DBP) at the end of CT. They also adopted a deeper slower pattern of breathing during exercise. The SM group showed significant (p<0.05) increases in duration, lower HR and DBP at the end of CT. Significantly (p<0.05) different effects between S and SM programmes were changes in VO2, max 100+/-101 mL x min(-1) versus 5+/-101 mL x min(-1)), duration of the CT (8.1+/-4.4 min versus 3.9+/-4.7 min), VCO2 (-94+/-153 mL x min(-1) versus 48+/-252 mL x min(-1)), lactate accumulation (-1.3+/-2.2 mmol x L(-1) versus 0+/-1.2 mmol x L(-1) and respiratory rate at the end of CT (4.3+/-3.4 min(-1) versus -1+/-4.2 min(-1)). Supervised, intense training yields physiological improvements in severe chronic obstructive pulmonary disease patients not induced by self-monitored training. The self-monitored, less intense training, increases submaximal exercise endurance, although to a lesser degree.

Influence of muscle fibre type and fitness on the oxygen uptake/power output slope during incremental exercise in humans

We recently reported that a higher percentage of type I fibres in vastus lateralis and a greater peak oxygen uptake (O2) were associated with a greater initial rise in O2 (O2 /W, where W is work rate) following the onset of heavy constant power output exercise (above the lactate threshold, LT). It was unclear if these results were true only for heavy exercise, or if the association between fibre type and/or fitness and O2 /W would also be seen for moderate (< LT) exercise. The purpose of the present study was to compare the relationships between fibre type or peak O2 and O2 /W determined for moderate (< LT) and heavy (> LT) exercise intensities during incremental exercise. Nine healthy subjects performed an incremental ramp test on a cycle ergometer. The O2 /Wslope was calculated for the domain of power outputs up to the LT (S1), from the LT towards peak O2 (S2), and over the entire linear portion of the O2 /W response (ST), and compared to fibre type distribution determined from biopsy of the vastus lateralis, and to peak O2 (as ml kg-1 min-1). Significant correlations between O2 /W and the proportion of type I fibres were found for each exercise domain (r is 0.69, 0.71 and 0.84 for S1, S2 and ST, respectively, P < 0.05). S1 ranged between about 9 ml min-1 W-1 for a low proportion of type I fibres and 11 ml min-1 W-1 for a high proportion of type I fibres. Similar correlations were also found between S2 (r = 0.70) and ST (r = 0.76) and peak O2. These results are consistent with our previous findings during > LT constant power output exercise, and suggest that the proportion of type I fibres, and possibly fitness as indicated by peak O2, is associated with greater O2 /W during the initial adjustment to < LT as well as > LT exercise. These results do not appear to be explained by classical descriptions of the kinetics of adjustment of O2 following the onset of ramp or constant power output exercise. They might reflect enhanced motor unit recruitment in subjects with a greater percentage of type I fibres, and/or who are more aerobically fit. However, the underlying mechanism for these findings must await further study.

Androgen effects on body composition and muscle function: implications for the use of androgens as anabolic agents in sarcopenic states

Testosterone-induced nitrogen retention in castrated male animals, eunuchoidal men, pre-pubertal boys and women, and the sex-related differences in the size of the muscles between male and female animals, have been cited as evidence that testosterone has anabolic effects. Recent studies have reported that replacement doses of testosterone in hypogonadal men and supraphysiological doses in eugonadal men increase fat-free mass, muscle size and strength. These effects have provided the rationale for exploring these anabolic applications in sarcopenic states. Although emerging data demonstrate modest gains in fat-free mass in HIV-infected men given replacement doses of testosterone, we do not know whether testosterone supplementation can produce clinically meaningful changes in muscle function and disease outcome in patients with wasting disorders.

Rationale for anabolic therapy to facilitate rehabilitation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) afflicts millions of people and is severely disabling. Exercise intolerance is usually the chief complaint. There are few effective therapies. Pulmonary rehabilitation seeks to return the patient to the highest possible level of function but cannot reverse the underlying pulmonary abnormalities. Several lines of evidence have recently pointed to abnormalities of the muscles of ambulation as a remediable source of exercise intolerance in COPD. Possible mechanisms of the muscle abnormalities include deconditioning, malnutrition, low levels of anabolic hormones and, perhaps, a specific myopathy. To date, most reports of attempts to reverse muscle dysfunction in COPD have focused on exercise training. However, abnormalities in the level of circulating anabolic hormones have recently been described, suggesting that anabolic hormone supplementation may be rational therapy for these patients. Accumulating evidence that anabolic steroids increase muscle mass and improve strength in older men is encouraging trials of anabolic steroids in men with COPD.

Patterns of dissimilarities among instrument models in measuring PO2, PCO2, and pH in blood gas laboratories

STUDY OBJECTIVES

To ascertain the degree of dissimilarities among blood gas and pH analyzer models of the same and different manufacturers in measurement of PO2, PCO2, and pH using fluorocarbon containing emulsion (FCE) proficiency testing material.

DESIGN

Statistically and graphically analyze data from six recent proficiency testing surveys for the 20 more frequently used models of analyzers.

SETTING AND PARTICIPANTS

Over a 2-year period, approximately 900 participants from blood gas laboratories in the United States analyzed similar ampules from each of 30 lots.

MEASUREMENTS AND RESULTS

Both graphic and statistical comparisons were used to demonstrate differences between manufacturers. For each of the four major manufacturers, comparisons revealed statistically significant differences not only for PO2, but also for PCO2 and pH. Additionally, comparison models within each of the three manufacturers (those with multiple models and > 15 instruments per model represented) disclosed statistically significant dissimilarities among models for each analyte in 115 of 153 model pairings. Previously reported tonometered blood differences among analyzer models for PO2 are qualitatively similar to the differences found in these same models in this FCE study. Model differences are important in research studies and may be clinically important in deciding abnormality, selecting oxygen therapy, or the treatment of patients with respiratory failure or severe respiratory alkalosis.

CONCLUSIONS

To minimize the likelihood of misleading clinicians, laboratory directors should consider the degree of dissimilarity among blood gas analyzer models in current use and when changing instrumentation.

The effect of exercise training on aerobic fitness, immune indices, and quality of life in HIV+ patients

PURPOSE

Thirty four HIV+ patients participated in a 6-wk aerobic exercise training program to determine whether exercise improved aerobic fitness, immune indices, and quality of life.

METHODS

Subjects were assigned to three groups: control (no regular aerobic exercise), moderate exercise, and heavy exercise training. At study entry and exit (in each subject) we evaluated aerobic function with a symptom limited cardiopulmonary exercise test, immune indices with CD4 counts and Candida skin tests, viral replication with plasma HIV RNA measurements, and quality of life with a HIV+ population validated questionnaire.

RESULTS

Aerobic fitness increased significantly in both exercise groups relative to the control group; immune indices changed very little among all three groups; however, the Candida skin tests (mm2) increased significantly in the moderate group; viral replication was essentially unchanged in all three groups; quality of life (QOL) markers improved in both exercising groups but not the control group. There were no opportunistic infections during the study.

CONCLUSIONS

Exercise training resulted in a substantial improvement in aerobic function while immune indices were essentially unchanged. Quality of life markers improved significantly with exercise. Exercise training is safe and effective in this patient group and should be promoted for HIV+ patients.

Mechanism of the exercise hyperkalemia: an alternate hypothesis

A progressive hyperkalemia is observed as exercise intensity increases. The current most popular hypothesis for the hyperkalemia is that the Na+-K+ pump cannot keep pace with the K+ efflux from muscle during the depolarization-repolarization process of the sarcolemmal membrane during muscle contraction. In this report, we present data that suggest an alternate hypothesis to those previously described. Because phosphocreatine (PCr) is a highly dissociated acid and creatine is neutral at cell pH, the concentration of nondiffusible anions decreases, and an alkaline reaction takes place when PCr hydrolyzes. This creates a state of cation (K+) excess and H+ depletion in the cell. To examine the balance of K+ and H+ for exercising muscle during the early period of exercise when PCr changes most rapidly, catheters were inserted into the brachial artery and femoral vein (FV) in five healthy subjects who performed two 6-min cycle ergometer exercise tests at 40 and 85% of peak oxygen uptake. FV blood was sampled every 5 s during the first 2 min, then every 30 s for the remaining 4 min of exercise and the first 3 min of recovery, and then less frequently for the next 12 min. Arterial sampling was every 30 s during exercise and simultaneous with FV sampling during recovery. Arterial K+ concentration ([K+]) increase lagged FV [K+] increase. The hyperkalemia observed during early exercise results from K+ release from skeletal muscle. FV [K+] increased by 5 s of the start of exercise and followed the rate of H+ loss from the FV blood for the first 30 s of exercise. FV lactate and Na+ kinetics differed from K+ kinetics during exercise and recovery. As predicted from the PCr hydrolysis reaction, the exercising limb took up H+ and released K+ at the start of exercise (first 30 s) at both exercise intensities, resulting in a FV metabolic alkalosis. K+ release was essentially complete by 3 min, the time at which oxygen uptake (and, presumably, PCr) reached its asymptote. These findings lead us to hypothesize that the early K+ release by the cell takes place with H+ exchange and that the major mechanism for the exercise hyperkalemia is the reduction in nondiffusible intracellular anions in the myocyte as PCr hydrolyzes.

Effect of acute bicarbonate administration on exercise responses of COPD patients

Patients with severe chronic obstructive pulmonary disease (COPD) are limited in their exercise tolerance by the level of ventilation (VE) they can sustain. We determined whether acutely increasing blood bicarbonate levels decreased acid stimulation to the respiratory chemoreceptors during exercise, thereby improving exercise tolerance. Responses were compared with those obtained during 100% O2 breathing (known to reduce VE in these patients) and to the responses of healthy young subjects. Participants were six patients with severe COPD (forced expired volume in 1 s = 31 +/- 11% predicted) but without chronic CO2 retention and 5 healthy young subjects. Each subject performed three incremental cycle ergometer exercise tests: 1) control, 2) after ingestion of 0.3 g.kg-1 of sodium bicarbonate and 3) while breathing 100% O2. During these tests VE was measured continuously and arterialized venous blood (patients) or arterial blood (healthy subjects) was sampled serially to assess acid base variables. Bicarbonate loading increased standard bicarbonate by 4-6 mmol.L-1 and this elevation persisted during exercise. In both groups, bicarbonate loading resulted in a substantially higher arterial pH; arterial PCO2 was either unchanged (healthy subjects) or mildly (averaging 5 torr) higher (COPD patients). However, in neither group did bicarbonate loading result in an altered VE response to exercise or an increase in exercise tolerance. In contrast, superimposing hyperoxia on bicarbonate ingestion yielded, on average, 24% reduction in VE and 50% increase in peak work rate in the patients (but not in the healthy young subjects). We conclude that acute bicarbonate loading is not an ergogenic aid in patients with severe COPD.

Physiologic benefits of exercise training in rehabilitation of patients with severe chronic obstructive pulmonary disease

We determined the effect on exercise tolerance and physiological exercise responses of rigorous rehabilitative exercise training in chronic obstructive pulmonary disease (COPD). Fifteen men and 10 women (mean age, 68 +/- 6 yr; FEV1, 0.93 +/- 0.27 L) participated in a rehabilitation program with an exercise component of three per week 45-min sessions of cycle ergometer training for 6 wk with exercise intensity kept near maximal targets. Before and after rehabilitation, patients performed an incremental test and a constant work rate (CWR) test at 80% of the peak work rate in the preprogram incremental test. Ventilation (V(E)) and gas exchange were measured breath by breath; arterialized venous blood was analyzed for blood gas determinations and lactate. Rehabilitation yielded an average increase in peak work rate in the incremental test of 36% (p < 0.001), and in the duration of the CWR test of 77% (p < 0.001). In the CWR test, the kinetics of O2 uptake, CO2 output, V(E), and heart rate were markedly slower than those of healthy subjects. After training, mean response time decrease averaged 17, 22, 34, and 29%, respectively (p < 0.02), evidence of a physiologic training effect. Further, for identical CWR tasks, V(E) was 10% lower (p < 0.02) after training, attributable to altered breathing pattern: tidal volume increased by 8% and respiratory rate decreased by 19%, yielding lower V(D) /V(T) (0.46 versus 0.53 p < 0.005). Rigorous exercise training for patients with severe COPD yields more efficient exercise breathing pattern and lower V(E); this is associated with improved exercise tolerance.