Outcomes for COPD pharmacological trials: from lung function to biomarkers

The American Thoracic Society/European Respiratory Society jointly created a Task Force on "Outcomes for COPD pharmacological trials: from lung function to biomarkers" to inform the chronic obstructive pulmonary disease research community about the possible use and limitations of current outcomes and markers when evaluating the impact of a pharmacological therapy. Based on their review of the published literature, the following document has been prepared with individual sections that address specific outcomes and markers, and a final section that summarises their recommendations.

Clinical use of Heliox in asthma and COPD

Heliox is a low density gas mixture of helium and oxygen commonly used in deep diving (> 6 ATM). This mixture has been also used for clinical purposes, particularly in the critical care setting. Due to of its physical proprieties, Heliox breathing reduces air flow resistances within the bronchial tree; in patients with obstructive lung diseases Heliox may also reduce the work of breathing and improve pulmonary gas exchange efficiency. Beneficial effects have been documented in severe asthma attacks and in patients with chronic obstructive pulmonary disease. A reduction in WOB during mechanical ventilation and an increase in exercise endurance capacity have also been described in COPD. Heliox has been also used in the treatment of upper airways obstruction, bronchiolitis and bronchopulmonary dysplasia. Despite the encouraging results, Heliox use in routine practice remains controversial because of technical implications and high costs.

Dilated Cardiomyopathy Due to Thrombotic Microangiopathy as the only Manifestation of Antiphospholipid Syndrome: A Case Report

Dilated cardiomyopathy due to thrombotic microangiopathy has been rarely reported as a clinical manifestation of antiphopspholipid syndrome (APS). We describe the case of a 39-year-old woman affected by systemic lupus erythematosus (SLE) and positive antiphospholipid antibodies (aPL) who presented with orthopnea and peripheral oedema. Diagnosis of dilated cardiomyopathy due to myocardial thrombotic microangiopathy was made and treatment with anticoagulants prevented the worsening of the clinical condition. Interestingly, at variance with other cases, our patient showed no extracardiac signs of APS. The review of the current literature has confirmed that dilated cardiomyopathy due to thrombotic microangiopathy is a rare manifestation of APS.

Circulating haemopoietic and endothelial progenitor cells are decreased in COPD

Circulating CD34+ cells are haemopoietic progenitors that may play a role in tissue repair. No data are available on circulating progenitors in chronic obstructive pulmonary disease (COPD). Circulating CD34+ cells were studied in 18 patients with moderate-to-severe COPD (age: mean+/-sd 68+/-8 yrs; forced expiratory volume in one second: 48+/-12% predicted) and 12 controls, at rest and after endurance exercise. Plasma concentrations of haematopoietic growth factors (FMS-like tyrosine kinase 3 (Flt3) ligand, kit ligand), markers of hypoxia (vascular endothelial growth factor (VEGF)) and stimulators of angiogenesis (VEGF, hepatocyte growth factor (HGF)) and markers of systemic inflammation (tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8) were measured. Compared with the controls, the COPD patients showed a three-fold reduction in CD34+ cell counts (3.3+/-2.5 versus 10.3+/-4.2 cells.microL-1), and a 50% decrease in AC133+ cells. In the COPD patients, progenitor-derived haemopoietic and endothelial cell colonies were reduced by 30-50%. However, four COPD patients showed progenitor counts in the normal range associated with lower TNF-alpha levels. In the entire sample, CD34+ cell counts correlated with exercise capacity and severity of airflow obstruction. After endurance exercise, progenitor counts were unchanged, while plasma Flt3 ligand and VEGF only increased in the COPD patients. Plasma HGF levels were higher in the COPD patients compared with the controls and correlated inversely with the number of progenitor-derived colonies. In conclusion, circulating CD34+ cells and endothelial progenitors were decreased in chronic obstructive pulmonary disease patients and could be correlated with disease severity.

Recommendations on the use of exercise testing in clinical practice

Evidence-based recommendations on the clinical use of cardiopulmonary exercise testing (CPET) in lung and heart disease are presented, with reference to the assessment of exercise intolerance, prognostic assessment and the evaluation of therapeutic interventions (e.g. drugs, supplemental oxygen, exercise training). A commonly used grading system for recommendations in evidence-based guidelines was applied, with the grade of recommendation ranging from A, the highest, to D, the lowest. For symptom-limited incremental exercise, CPET indices, such as peak O(2) uptake (V'O(2)), V'O(2) at lactate threshold, the slope of the ventilation-CO(2) output relationship and the presence of arterial O(2) desaturation, have all been shown to have power in prognostic evaluation. In addition, for assessment of interventions, the tolerable duration of symptom-limited high-intensity constant-load exercise often provides greater sensitivity to discriminate change than the classical incremental test. Field-testing paradigms (e.g. timed and shuttle walking tests) also prove valuable. In turn, these considerations allow the resolution of practical questions that often confront the clinician, such as: 1) "When should an evaluation of exercise intolerance be sought?"; 2) "Which particular form of test should be asked for?"; and 3) "What cluster of variables should be selected when evaluating prognosis for a particular disease or the effect of a particular intervention?"

Rhinitis and asthma in athletes: an ARIA document in collaboration with GA2LEN

This consensus document is aimed at reviewing evidence that the rhinitis-asthma links have peculiar features in athletes. Beside a review of epidemological data on the high prevalence of rhinitis and asthma in athletes, the effects on intense physical exercise on the immune system and repiratory functions are discussed, with special reference to the role of allergens and pollutants. In extending the Allergic Rhinitis and its Impact on Asthma (ARIA) recommendations to athletes, the issue is addressed of adapting diagnosis and management to criteria set by the International Olympic Committee (IOC) and regulations adopted by the World Anti-Doping Agency (WADA).

Water and sodium imbalance in COPD patients

Water retention and hyponatraemia are typically observed in the final stages of Chronic Obstructive Pulmonary Disease (COPD) and the onset of edema is a poor prognostic factor. For several years the pathogenesis of edema in COPD patients was attributed to heart impairment because of pulmonary hypertension, but the evidence that cardiac output is often adequate for the metabolic demands has suggested, since 1960, that the pathogenesis of edema in these patients would be correlated with gas exchange impairment and in particular with carbon dioxide (CO2) retention. The gas exchange impairment induces, in these patients several hormonal abnormalities: renin (Rn), angiotensin II (AnII), aldosterone (Ald), atrial natriuretic peptide (ANP), vasopressin (ADH) and endothelial factors are some of the factors involved. The systemic response to hypercapnia has the effect of reducing the renal blood flow and, as a result, increasing water and sodium retention with the final effect of edema and hyponatraemia. The aim of this brief review is to highlight the current knowledge on renal/hormonal abnormalities in COPD and their therapeutic implications.

Exercise physiology in COPD

Multiple mechanisms contribute to exercise limitation in chronic obstructive pulmonary disease (COPD). The ability to increase ventilation during exercise is reduced; the more advanced the disease, the more impaired the exercise tolerance is. However, factors other than ventilatory limitation play an important role in reducing the exercise capacity in COPD. Data implicating peripheral muscle atrophy and muscle weakness as cofactors have been reported in individuals with advanced disease. At this stage daily activities are curtailed to avoid exertional respiratory discomfort. Recent studies have demonstrated that the muscle aerobic capacity of stable hypoxemic COPD patients is impaired; oxygen uptake (V'O2) kinetics and 31P magnetic resonance spectroscopy studies have shown that these patients rely heavily on non-aerobic energy sources even during moderate, sustained workloads. Finally, early occurrence of metabolic acidosis has been demonstrated in patients with mild to severe COPD during exercise. Inadequate tissue oxygenation appears to result from a defect in peripheral oxygen utilization rather than from a reduction in O2 bulk flow. Peripheral factors may include: a) impaired diffusive conductance for O2 between red cells and mitochondria; b) heterogeneous distribution of O2 bulk flow within the exercising muscle fibers; c) inertia of the oxidative processes at the cellular level; d) changes in distribution of muscle fibers, e) reduction in muscle aerobic enzymes; and f) poor nutritional status. Since muscle dysfunction has an important role in the development of exercise intolerance, physical rehabilitation is more and more used as part of the treatment of COPD. The aim of this review is to briefly discuss current views on the mechanisms responsible for the reduced ability to exercise and the rationale for exercise rehabilitation in COPD patients.

Management of COPD: surgical options

Dyspnoea on exertion and exercise intolerance are the hallmarks of chronic obstructive pulmonary disease (COPD); the primary causes appear to be respectively, increased airway resistance with reduced maximal ventilatory capacity and peripheral skeletal muscle dysfunction with early onset of anaerobic metabolism. Patients with end-stage COPD usually show little or no benefit from conventional medical treatment. Physical training is capable of ameliorating exercise tolerance, but improvement is usually modest in the advanced disease state. Two surgical options are generally accepted for carefully selected patients with emphysema: resection of large bullae, when identified, and lung transplantation. Transplantation, the only effective cure for advanced COPD, is of limited use primarily because of age, comorbidity, limited availability of organs and cost. A different approach for severe emphysema, lung volume reduction surgery (LVRS), has been increasingly utilized during the past several years. In carefully selected emphysematous patients, LVRS improves lung volumes and mechanics, and reduces exertional dyspnoea. Unfortunately, surgical mortality still remains high and some patients show no measurable improvement after surgery. There is an urgent need for data on long-term effects of LVRS; the results of large, randomized trials will soon be forthcoming. The aim of this brief review is to summarize the available knowledge on the effects of LVRS, the criteria for patient selection, short- versus long-term effects and, finally, to propose future directions in this field.

Skeletal muscle dysfunction in chronic obstructive pulmonary disease

During the last decade evidence has been accumulated on the role of skeletal muscle dysfunction in reducing exercise capacity and affecting the quality of life of patients with chronic obstructive pulmonary disease (COPD). An appreciable body of research has helped to identify morphological and biochemical alterations, physiological consequences, and possible therapeutic interventions. There are, however, still many areas of uncertainty. For example it is not clear how much of the alterations are within the muscle itself or the consequence of the altered environment in which the muscle works. Similarly it is not clear how much of the impairment is simply due to aging and chronic inactivity. Another key issue is the possible additive effect of drugs often used in COPD patients, such as steroids, beta 2-agonist and cyclosporin. A specific additional layer of complexity comes from nutritional considerations and in particular loss of muscle mass which not infrequently accompanies severe disease and even greater exercise intolerance. Studies on the effects of training or other therapeutic interventions have shown that muscle dysfunction is partially reversible. There is, however, a clear need for studies based on cellular and molecular methods aimed to clarify the role of factors such as oxidative stress, inflammation and nutritional deficiencies on skeletal muscle structure and function. The focus of this review is to highlight the current knowledge on skeletal muscle dysfunction in COPD and briefly summarize the possible therapeutic implications.

CD4(+) T-lymphocytopenia and Pneumocystis carinii pneumonia in a patient with miliary tuberculosis

We report a case of miliary tuberculosis (MTB) occurring after extracorporeal shock-wave lithotripsy in a 51-year-old man. The MTB was complicated by pancytopenia and CD4(+) T-lymphocytopenia, which was responsible for Pneumocystis carinii pneumonia. Hematological parameters returned to normal in response to antituberculous treatment.

Ventilatory and metabolic adaptations to walking and cycling in patients with COPD

To test the hypothesis that in chronic obstructive pulmonary disease (COPD) patients the ventilatory and metabolic requirements during cycling and walking exercise are different, paralleling the level of breathlessness, we studied nine patients with moderate to severe, stable COPD. Each subject underwent two exercise protocols: a 1-min incremental cycle ergometer exercise (C) and a "shuttle" walking test (W). Oxygen uptake (VO(2)), CO(2) output (VCO(2)), minute ventilation (VE), and heart rate (HR) were measured with a portable telemetric system. Venous blood lactates were monitored. Measurements of arterial blood gases and pH were obtained in seven patients. Physiological dead space-tidal volume ratio (VD/VT) was computed. At peak exercise, W vs. C VO(2), VE, and HR values were similar, whereas VCO(2) (848 +/- 69 vs. 1,225 +/- 45 ml/min; P < 0. 001) and lactate (1.5 +/- 0.2 vs. 4.1 +/- 0.2 meq/l; P < 0.001) were lower, DeltaVE/DeltaVCO(2) (35.7 +/- 1.7 vs. 25.9 +/- 1.3; P < 0. 001) and DeltaHR/DeltaVO(2) values (51 +/- 3 vs. 40 +/- 4; P < 0.05) were significantly higher. Analyses of arterial blood gases at peak exercise revealed higher VD/VT and lower arterial partial pressure of oxygen values for W compared with C. In COPD, reduced walking capacity is associated with an excessively high ventilatory demand. Decreased pulmonary gas exchange efficiency and arterial hypoxemia are likely to be responsible for the observed findings.

Pulmonary gas exchange and exercise capacity in patients with systemic lupus erythematosus

OBJECTIVE

Exercise tolerance is often reduced in patients with systemic lupus erythematosus (SLE). Mechanisms have been proposed but the underlying causes have not yet been elucidated. The study of pulmonary gas exchange during exercise may be helpful in revealing circulatory, ventilatory, and metabolic abnormalities. We hypothesized that in SLE, exercise aerobic capacity would be reduced due to chronic inactivity and poor muscle energetics.

METHODS

Thirteen women with SLE and low disease activity were studied; 5 age matched subjects served as controls. Clinical examination, chest radiography, electrocardiogram, and pulmonary function test were all normal. Subjects underwent 1 min incremental cycle ergometer exercise to exhaustion. Oxygen uptake (VO2), CO2 output (VCO2), minute ventilation (VE), heart rate (HR), and arterial O2 saturation were monitored. Anaerobic threshold (AT), VO2/HR, deltaVO2/deltaWatt, respiratory rate (RR), Ti/Ttot, VE/VCO2, and breathing reserve (BR) were computed.

RESULTS

At rest, patients exhibited high VE, respiratory alkalosis, and a wide alveolar-arterial O2 gradient [(A - a)O2] during 50% O2 breathing. Other indexes of respiratory function were within the normal range. In the 6 patients with SLE where pulmonary artery systolic pressure at Doppler echocardiography was measurable, mean level was in the upper limits of normal. During exercise, maximal aerobic capacity was reduced in all patients (VO2 peak, 1098+/-74 vs. 2150+/-160 ml/min, p<0.01; AT, 36 +/-3 vs. 48+/-3% predicted VO2 max, p<0.05). Ventilation adjusted for the metabolic demand (VE/VCO2 at AT) was increased (31+/-1 vs. 24+/-1; p<0.05). A normal breathing pattern was observed during all tests. No patient stopped exercising because of ventilatory limitation (i.e., they had normal breathing reserve).

CONCLUSION

Reduced muscle aerobic capacity is common in SLE and is most likely because of peripheral muscle deconditioning. Increased ventilatory demand, secondary to diffuse interstitial lung disease, is not a significant contributor to the reduction in exercise tolerance.

Gas exchange response to exercise in patients with chronic heart failure

The objective of the study was investigate the pulmonary gas exchange response to exercise in 16 male patients with chronic heart failure (CHF) due to previous myocardial infarction and left ventricular dysfunction (ejection fraction < 45%). All patients underwent a symptom-limited exercise test during which cardiac frequency (fC), tidal volume (VT), respiratory frequency (fR), minute ventilation (V'E), oxygen consumption (V'O2) and carbon dioxide production (V'CO2) were measured on a breath-by-breath basis. Ventilatory equivalent for carbon dioxide (V'E/V'CO2) and lactate threshold (LT) were calculated. Arterial blood gas levels were measured at rest and at peak exercise. The dead space (VD) to tidal volume ratio (VD/VT) and alveolar-arterial oxygen gradient (PA-a,O2) were computed. Two subgroups of patients were identified according to peak V'O2 (V'O2,peak), group A (n = 7), V'O2,peak > 14 mL.kg-1.min-1 (17.2 +/- 2.5 SEM, range 14.5-20.8), and group B (n = 9), V'O2,peak < 14 mL.kg-1.min-1 (11.9 +/- 1.8, range 9.2-13.6). Arterial oxygen tension (Pa,O2) increased from rest to peak exercise in both groups (group A: 12.2 +/- 0.94 to 13.4 +/- 0.82 kPa (91.4 +/- 7.1 to 100.4 +/- 6.2 mmHg), p < 0.05; group B: 11.7 +/- 1.0 to 13.4 +/- 1.1 kPa (88.0 +/- 7.8 to 100.9 +/- 8.2 mmHg), p < 0.01), while a significant reduction in arterial carbon dioxide tension (Pa,CO2), from rest to peak exercise, was observed in group B only (4.64 +/- 0.39 to 4.08 +/- 0.36 kPa (34.9 +/- 2.8 to 30.7 +/- 2.7 mmHg), p < 0.005). Maximal V'E and maximal power (Powermax) were significantly lower in group B compared to group A (V'E 37.6 +/- 8.4 versus 52.1 +/- 13.8 L.min-1, p < 0.05; Powermax 64.4 +/- 12 versus 82.8 +/- 14.1 W, p < 0.01). fC was not significantly different at peak exercise, although the work load was significantly higher in group A. VD/VT failed to decrease significantly at maximal exercise in both groups. In group B, V'E/V'CO2 tended to be higher than in group A. In chronic heart failure patients, measurements of arterial blood gas levels during exercise might help to identify those subjects with a more pronounced depression of left ventricular function. At peak exercise, high ventilatory demand and respiratory alkalosis were observed in group B patients, suggesting an increased responsiveness of the respiratory centre that might be one major factor contributing to this excessive ventilatory response to exercise; vice versa, a combination of ventilation-perfusion mismatch, wasted ventilation and unpaired peripheral blood circulation seem to play only a minor role.

Effect of reduced body weight on muscle aerobic capacity in patients with COPD

BACKGROUND

Reduced muscle aerobic capacity in COPD patients has been demonstrated in several laboratories by phosphorus magnetic resonance spectroscopy and by analysis of oxygen uptake (VO2) kinetics. COPD patients are usually elderly, hypoxemic, poorly active with muscle atrophy, and often malnourished. Under these conditions there is usually reduction of O2 delivery to the tissues (bulk O2 flow), redistribution of fiber type within the muscle, capillary rarefaction, and decreased mitochondrial function, alterations all capable of reducing muscle aerobic capacity. In COPD, the effect of reduced body mass on muscle aerobic capacity has not been investigated (to our knowledge).

METHODS

We studied 24 patients with stable COPD with moderate-to-severe airway obstruction (68+/-5 [SD] years; FEV1, 39+/-12% predicted; PaO2, 66+/-8 mm Hg; PaCO2, 41+/-3 mm Hg) with poor to normal nutritional status, as indicated by a low-normal percent of ideal body weight (IBW). Each subject first underwent 1-min maximal incremental cycle ergometer exercise for determination of VO2 peak and lactate threshold (LT). Subsequently, they performed a 10-min moderate (80% of LT-VO2) constant load exercise for determination of oxygen deficit (O2DEF) and mean response time VO2 (MRT). VO2, CO2 output (VCO2), and minute ventilation were measured breath by breath.

RESULTS

Patients displayed low VO2 peak (1,094+/-47 [SE] mL/min), LT-VO2 (35+/-3% predicted O2 max), and higher MRT-VO2 (67+/-4 s). Univariate regression analysis showed that percent of IBW correlated with indexes of maximal and submaximal aerobic capacity: vs VO2 peak, R=0.53 (p<0.01); vs MRT R=-0.77 (p<0.001). Using stepwise regression analysis, MRT correlated (R2=-0.70) with percent of IBW (p<0.01) and with PaO2 (p<0.05).

CONCLUSIONS

Reduced body mass has an independent negative effect on muscle aerobic capacity in COPD patients: this effect may explain the variability in exercise tolerance among patients with comparable ventilatory limitation.

Hemodynamic, renal, and hormonal responses to lower body positive pressure in human subjects

Studies in healthy human subjects subjected to lower body positive pressure (LBPP) have failed to elucidate many of the physiologic effects of this maneuver. In 7 healthy, well-hydrated men we studied the following responses to LBPP (35 mm Hg, 1 hour, supine position): systemic and renal hemodynamics; urine volume (UV), urine osmolality (Uosm), and urine sodium level (UNaV); free water (CH20) and osmolar (Cosm) clearances; plasma renin activity (PRA); levels of aldosterone (PA), cortisol (CORT), norepinephrine (NE), atrial natriuretic peptide (ANP), and vasopressin (AVP); osmolality (Posm); and serum sodium level. Subjects were restudied on a control day with zero trouser pressure. The recorded changes (p < 0.05) when comparing the LBPP day with the control day were as follows: fractional Na+ reabsorption increased (98.7% +/- 0.2% to 99.3% +/- 0.1%) and UNaV decreased (0.19 +/- 0.03 mEq/min to 0.10 +/- 0.01 mEq/min), with concomitant increases in PRA (1.7 +/- 0.2 ng/ml/90 min to 4.5 +/- 1.8 ng/ml/90 min), PA (7.7 +/- 0.7 ng/dl to 9.3 +/- 1.5 ng/dl), and CORT (13.0 +/- 2.6 mg/dl to 19.2 +/- 3 mg/dl); the increase in blood pressure with LBPP (96 +/- 3 mm Hg to 112 +/- 4 mm Hg) was greater than that during control conditions. Renal plasma flow tended to display an interactive pattern across days, with a slight decline during LBPP (5%) and a slight elevation under control conditions (9%). On the LBPP day only, filtered Na+ declined (15 +/- I mEq/min to 12 +/- 1 mEq/min) as a function of reduced glomerular filtration rate (112 +/- 5 ml/min to 91 +/- 7 ml/min), blood volume decreased (by 2.7% +/- 0.7%), CO decreased (5.5 +/- 0.3 L/min to 4.7 +/- 0.3 L/min), and stroke volume declined (101 +/- 6 ml to 84 +/- 3 ml). On both days, NE increased (control, 221 +/- 23 pg/ml to 340 +/- 33 pg/ml; LBPP, 236 +/- 17 pg/ml to 369 +/- 31 pg/ml) and ANP increased (control, 47 +/- 7 pg/ml to 97 +/- 21 pg/ml; LBPP, 49 +/- 10 pg/ml to 104 +/- 30 pg/ml). We concluded that LBPP reduces renal sodium excretion. The mechanism for this reduction is not known, although it did occur in association with an increase in plasma renin activity, which in turn results from mechanical reduction of renal perfusion, stress-related CORT stimulation, a reflex-based elevation in peripheral vascular resistance leading to a reflex increase in plasma renin activity, or a combination of these.

Exercise-induced asthma in figure skaters

Many highly trained athletes experience exercise-induced bronchospasm (EIB): studies describing EIB in figure skaters, who may be at increased risk of EIB due to rink temperatures (7 to 10 degrees C), have not been published. We studied professionally coached figure skaters (n = 124) for EIB by spirometry at rinkside immediately before a simulated long program and at 0 to 1, 5, 10, and 15 min postexercise. Postexercise spirometry revealed the presence of EIB (a decrease from baseline in FEV1 of at least 10%) in 43 skaters, while the remainder (n = 81, control group) remained relatively stable. Pre-exercise FEV1, FVC, and FEV1/FVC ratio were not different between groups. The EIB group had significantly lower FEV1 vs baseline at each measurement following exercise: baseline, 3.08 +/- 0.13; 0 to 1 min postexercise, 2.81 +/- 0.13 (p < 0.05); 5 min postexercise, 2.77 +/- 0.14 (p < 0.05); 10 min postexercise, 2.78 +/- 0.13 (p < 0.05); 15 min postexercise, 2.78 +/- 0.13 (p < 0.05). The EIB group also had lower FVC: baseline, 3.48 +/- 0.16; 0 to 1 min postexercise, 3.16 +/- 0.15 (p < 0.05); 5 min postexercise, 3.19 +/- 0.15 (p < 0.05); 10 min postexercise, 3.27 +/- 0.16 (p < 0.05); 15 min postexercise, 3.26 +/- 0.16 (p < 0.05). Control subjects, however, experienced no decline in these variables. In conclusion, the incidence of EIB in the figure skaters measured during this investigation (43 of 124 = 35%) is greater than that of the population at large and other highly trained athletes, signifying that screening for EIB and therapeutic follow-up are reasonable considerations for participants in this sport.

Oxygen effect on O2 deficit and VO2 kinetics during exercise in obstructive pulmonary disease

We evaluated the effect of supplemental O2 on energy metabolism of hypoxemic humans by measuring O2 uptake (VO2) kinetics and other cardiorespiratory parameters in nine male chronic obstructive pulmonary disease (COPD) patients and seven age-matched control subjects (on air and on 30% O2) at rest and during moderate cycle ergometer exercise. Heart rate, ventilation, VO2, CO2 output, respiratory exchange ratio, O2 cost of work, and work efficiency were measured with a computerized metabolic cart; O2 deficit and VO2 time courses were calculated. In COPD patients, 30% O2 breathing resulted in 1) reduction of O2 deficit (from 488 +/- 34 ml in air to 398 +/- 27 ml in O2; P < 0.05) and phase 2 VO2 time constant (from 116 +/- 13 s in air to 74 +/- 12 s in O2; P < 0.05); 2) a smaller steady-state increment in CO2 output than in room air (315 +/- 17 ml/min in O2 vs. 358 +/- 27 ml/min in air; P < 0.02), which resulted in a lower exercise respiratory exchange ratio (0.75 +/- 0.02 in O2 vs. 0.80 +/- 0.02 in air; P < 0.02); and 3) reduced steady-state ventilation (22.6 +/- 1.0 l/min in O2 vs. 25.4 +/- 1.1 l/min in air; P < 0.05). In conclusion, 30% O2 breathing accelerated exercise VO2 kinetics in mildly hypoxemic COPD patients. The observed VO2 kinetics improvement with O2 supplementation is consistent with an enhancement of aerobic metabolism in skeletal muscles during moderate exercise.

Nutritional state and exercise tolerance in patients with COPD

We hypothesized that in patients with COPD, poor nutritional status adversely influences exercise tolerance by limiting aerobic capacity of exercising muscles. In 28 patients with stable COPD, we correlated nutritional status with gas exchange indexes obtained during maximal incremental cycle ergometer exercise and with respiratory function parameters. On the basis of percent of ideal body weight (%IBW), patients were divided into three groups (GP): GP1 (n = 8, %IBW < 90); GP2 (n = 13, %IBW > or = 90 < 110); and GP3 (n = 7, %IBW > or = 110). When compared with normally nourished individuals (GPs 2 and 3), malnourished GP1 patients showed greater reduction in maximal workload and in peak O2 uptake (VO2 peak), with earlier onset of metabolic acidosis (anaerobic threshold [AT]); in addition, indexes reflecting O2 cost of ventilation were higher in GP1. Nutritional status could be correlated with exercise tolerance (VO2 peak, r = 0.82, p < 0.0001), with onset of metabolic acidosis (AT, r = 0.69, p < 0.0001) and with dead space/tidal volume ratio (VD/VT, r = -0.59, p < 0.001). Body weight was inversely correlated with indexes that are likely to reflect the increase in O2 cost of ventilation. We conclude that in patients with stable COPD, (1) malnutrition significantly affects muscle aerobic capacity and exercise tolerance, and (2) high wasted ventilation and O2 cost of ventilation may be responsible for the weight loss.