Expiratory flow limitation promotes dynamic hyperinflation during exercise in chronic obstructive pulmonary disease (COPD) patients with a consequent reduction in inspiratory capacity (IC), limiting their exercise tolerance. Therefore, the exercise capacity of patients with tidal expiratory flow limitation (FL) at rest should depend on the magnitude of IC. The presented study was designed to evaluate the role of FL on the relationship between resting IC, other respiratory function variables and exercise performance in COPD patients.Fifty-two patients were included in the study. Negative expiratory pressure (NEP) technique was employed to assess FL. Maximal work rate (WRmax) and oxygen uptake (V'O 2 ,max) were measured during an incremental symptom-limited cycle exercise.Twenty-nine patients were FL at rest. The IC was normal in all non-FL patients, while in most FL subjects it was decreased. Both WRmax and V'O 2 ,max were lower in FL patients (p<0.001, each). A close relationship of WRmax and V'O 2 ,max to IC was found (r=0.73 and 0.75, respectively; p<0.0001, each). In the whole group, stepwise regression analysis selected IC and forced expiratory volume in one second (FEV1)/ forced vital capacity (FVC) (% predicted) as the only significant contributors to exercise tolerance. Subgroup analysis showed that IC was the sole predictor in FL patients, and FEV1/FVC in non-FL patients.Detection of flow limitation provides useful information on the factors that influence exercise capacity in chronic obstructive pulmonary disease patients. Accordingly, in patients with flow limitation, inspiratory capacity appears as the best predictor of exercise tolerance, reflecting the presence of dynamic hyperinflation. Patients with chronic obstructive pulmonary disease (COPD) show widely variable exercise capacities. The relationship between resting lung function and exercise tolerance has been extensively studied in this group of patients [1±5]. In most previous studies, it was found that forced expiratory volume in one second (FEV1) was a poor predictor of exercise capacity [1±3]. Recently, however, it has been shown that indices related to dynamic hyperinflation, such as the inspiratory capacity (IC), are more closely related to exercise tolerance than FEV1 [4,5].Even at rest, patients with COPD often exhibit tidal expiratory flow limitation (FL) [6,7], promoting an increase in end-expiratory lung volume (EELV) due to dynamic hyperinflation with a concomitant decrease in inspiratory capacity and inspiratory reserve volume (IRV) [8,9]. During exercise, normal subjects increase the tidal volume (VT) at the expense of both the IRV and the expiratory reserve volume [8,9]. In contrast, in flowlimited COPD patients, VT increases only at the expense of their reduced IRV and eventually it impinges into the flat portion of the static volume-pressure relationship of the respiratory system [8,9]. Thus, in flow-limited COPD patients the maximal VT (VT,max) achieved during exercise should depend on the magnitude of IC. Since the ...

Physical inactivity is a cardinal feature of chronic obstructive pulmonary disease (COPD), and is associated with increased morbidity and mortality. Pedometers, which have been used in healthy populations, might also increase physical activity in patients with COPD.COPD patients taking part in a 3-month individualised programme to promote an increase in their daily physical activity were randomised to either a standard programme of physical activity encouragement alone, or a pedometer-based programme. Assessments were performed by investigators blinded to treatment allocation. Change in average 1-week daily step count, 6-min walking distance (6MWD), modified Medical Research Council scale, St George’s respiratory questionnaire (SGRQ) and COPD assessment test (CAT) were compared between groups.102 patients were recruited, of whom 97 completed the programme (pedometer group: n=50; control group: n=47); 60.8% were male with a mean±sd age of 68.7±8.5 years, and forced expiratory volume in 1 s (FEV1) 66.1±19.4% and FEV1/forced vital capacity 55.2±9.5%. Both groups had comparable characteristics at baseline. The pedometer group had significantly greater improvements in: physical activity 3080±3254 steps·day−1 versus 138.3±1950 steps·day−1 (p<0.001); SGRQ −8.8±12.2 versus −3.8±10.9 (p=0.01); CAT score −3.5±5.5 versus −0.6±6.6 (p=0.001); and 6MWD 12.4±34.6 versus −0.7±24.4 m (p=0.02) than patients receiving activity encouragement only.A simple physical activity enhancement programme using pedometers can effectively improve physical activity level and quality of life in COPD patients.

Mechanisms of worsening gas exchange during acute exacerbations of chronic obstructive pulmonary disease. J. A. Barberà, J. Roca, A. Ferrer, M.A. Félez, O. Díaz, N. Roger, R. Rodriguez-Roisin. ERS Journals Ltd 1997. ABSTRACT: This study was undertaken to investigate the mechanisms that determine abnormal gas exchange during acute exacerbations of chronic obstructive pulmonary disease (COPD). Thirteen COPD patients, hospitalized because of an exacerbation, were studied after admission and 38±10 (±SD) days after discharge, once they were clinically stable. Measurements included forced spirometry, arterial blood gas values, minute ventilation (V ' 'E), cardiac output (Q ' '), oxygen consumption (V ' 'O 2 ), and ventilation/perfusion (V ' 'A/Q ' ') relationships, assessed by the inert gas technique.Exacerbations were characterized by very severe airflow obstruction (forced expiratory volume in one second (FEV1) We conclude that worsening of gas exchange during exacerbations of chronic obstructive pulmonary disease is primarily produced by increased ventilation/perfusion inequality, and that this effect is amplified by the decrease of mixed venous oxygen tension that results from greater oxygen consumption, presumably because of increased work of the respiratory muscles. Eur Respir J 1997; 10: 1285-1291 Episodes of acute exacerbation are one of the most common complications in the evolution of chronic obstructive pulmonary disease (COPD). Irrespective of the precipitating factor, these episodes are characterized by worsening of pulmonary gas exchange that results in severe hypoxaemia with or without hypercapnia [1]. Abnormal gas exchange is thought to have a multifactorial origin [2], although some evidence suggests greater ventilation/perfusion (V'A/Q') inequality as the major determinant of respiratory failure [3,4]. However, little information exists concerning the characteristics of the V 'A/Q ' distributions and their interrelations with the conditions under which the lung operates, namely the extrapulmonary factors (i.e. ventilation, cardiac output, oxygen uptake) that also influence the arterial blood gas values. This lack of information is due essentially to the difficulty of assessing and quantifying the degree of V'A/Q' mismatch. In this regard, the use of the multiple inert gas elimination technique has been a major advance in interpreting gas exchange abnormalities, as it allows quantitation of V'A/Q' distributions and characterization of the different factors that produce hypoxaemia [5]. Identification and interpretation of the pathophysiological determinants of abnormal gas exchange during exacerbations of COPD should help to optimize the management of such episodes [6,7].Accordingly, the present study was undertaken to investigate the contribution of the different mechanisms that determine abnormal gas exchange during acute exacerbations of COPD by using the inert gas elimination technique, and to examine how the factors contributing to abnormal gas exchange vary during recovery.

Effects of noninvasive ventilation on lung hyperinflation in stable hypercapnic COPD. O. Díaz, P. Bégin, B. Torrealba, E. Jover, C. Lisboa. #ERS Journals Ltd 2002. ABSTRACT: Two previous uncontrolled studies have suggested that noninvasive mechanical ventilation (NIMV) in patients with hypercapnic chronic obstructive pulmonary disease (COPD) improves arterial blood gas tensions by decreasing lung hyperinflation with the consequent reduction in inspiratory loads and changes in ventilatory pattern. The aim of this randomised placebo-controlled study was to determine whether these mechanisms play a pivotal role in the effects of NIMV on arterial blood gases.Thirty-six stable hypercapnic COPD patients were randomly allocated to NIMV or sham NIMV. A 2-week run-in period was followed by a 3-week study period, during which ventilation was applied 3 h?day -1 , 5 days a week. Arterial blood gases, spirometry, lung volumes, and respiratory mechanics were measured before and after application of NIMV.Patients submitted to NIMV showed changes (mean (95% confidence interval)) in daytime arterial carbon dioxide tension (Pa,CO 2 ) and arterial oxygen tension of -1.12 (-1.52--0.73) kPa (-8.4 (-11.4--5.5) mmHg) and 1.14 (0.70-1.50) kPa (8.6 (5.3-11.9) mmHg), respectively. Total lung capacity, functional residual capacity (FRC) and residual volume were found to be reduced by 10 (7-13), 25 (18-31), and 36 (27-45)% of their predicted value, respectively, whereas forced expiratory volume in one second and forced vital capacity increased by 4 (1.5-6.9) and 9 (5-13)% pred, respectively. Tidal volume (VT) increased by 181 (110-252) mL. All of the above changes were significant compared with sham NIMV. Changes in Pa,CO 2 were significantly related to changes in dynamic intrinsic positive end-expiratory pressure, inspiratory lung impedance, VT and FRC.It was concluded that the beneficial effects of noninvasive mechanical ventilation could be explained by a reduction in lung hyperinflation and inspiratory loads.

Arterial oxygen tension (PaO2) is known to decrease with age, and this is accompanied by a number of changes in mechanical properties of the lungs, including loss of elastic recoil and increase in closing volume. The changes in respiratory mechanics with age could induce greater ventilation/perfusion (VA/Q) mismatch and thus explain the decrease in PaO2. In 64 normal subjects aged 18 to 71 yr (lifetime nonsmokers with normal spirometry), we measured VA/Q inequality and arterial respiratory blood gases (PaO2 and PaCO2) at rest in the seated position. VA/Q mismatch, represented by the second moments of the blood flow and ventilation distributions (log SDQ and log SDV) increased with age, but only slightly (mean log SDQ was 0.36 at age 20 yr and 0.47 at age 70 yr). PaO2 fell by a correspondingly small amount of 6 mm Hg. Previously established upper 95% confidence limits for log SDQ (0.60) and log SDV (0.65) in subjects at age 20 yr were confirmed. At age 70 yr, the upper limits of reference for log SDQ are 0.70 and for log SDV 0.75. The study shows that an increased alveolar-arterial O2 gradient with age is due to VA/Q inequality rather than to shunting.