Efeitos sistêmicos da hipoxemia noturna em pacientes com doença pulmonar obstrutiva crônica sem síndrome da apnéia obstrutiva do sono

OBJETIVO: Estudar os efeitos da hipoxemia noturna em pacientes com doença pulmonar obstrutiva crônica sem síndrome da apnéia obstrutiva do sono. MÉTODOS: Estudamos 21 pacientes-10 dessaturadores e 11 não-dessaturadores-submetidos a gasometria arterial, polissonografia, espirometria, teste de exercício cardiopulmonar (cicloergômetro), dinamometria manual e medidas de pressão inspiratória máxima, pressão expiratória máxima e proteína C reativa (PCR). Incluíram-se os pacientes com pressão parcial arterial de oxigênio > 60 mmHg; excluíram-se os com índice de apnéia-hipopnéia > 5 eventos/hora de sono. Foram medidos consumo máximo de oxigênio, potência máxima, pressão arterial sistólica, pressão arterial diastólica (PAD) e frequência cardíaca máxima durante exercício, visando detectar alterações hemodinâmicas. A PCR foi considerada positiva quando acima de 3 mg/L. RESULTADOS: A saturação periférica de oxigênio mínima durante o sono foi significativamente maior nos não-dessaturadores (p = 0,03). Mais dessaturadores apresentaram PCR > 3 mg/L (p < 0,05). Não houve diferença quanto a capacidade de exercício e demais variáveis. No entanto, PAD (p < 0,001) e pressão inspiratória máxima (p = 0,001) correlacionaram-se com saturação periférica de oxigênio média durante o sono. CONCLUSÕES: A hipoxemia noturna não reduz a capacidade de exercício e a força de preensao manual em pacientes com DPOC leve/moderada, mas o ajuste da PAD durante o exercício máximo parece depender do grau de hipoxemia. Além disso, há uma relação positiva entre pressão inspiratória máxima e saturação periférica de oxigênio média durante o sono, bem como indícios de ativação inflamatória diferenciada em pacientes com hipoxemia noturna.

Respiratory muscle unloading improves leg muscle oxygenation during exercise in patients with COPD

BACKGROUND

Respiratory muscle unloading during exercise could improve locomotor muscle oxygenation by increasing oxygen delivery (higher cardiac output and/or arterial oxygen content) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

Sixteen non-hypoxaemic men (forced expiratory volume in 1 s 42.2 (13.9)% predicted) undertook, on different days, two constant work rate (70-80% peak) exercise tests receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Delta%) in deoxyhaemoglobin (HHb), oxyhaemoglobin (O(2)Hb), tissue oxygenation index (TOI) and total haemoglobin (Hb(tot)) in the vastus lateralis muscle were measured by near-infrared spectroscopy. In order to estimate oxygen delivery (Do(2)est, l/min), cardiac output and oxygen saturation (Spo(2)) were continuously monitored by impedance cardiography and pulse oximetry, respectively.

RESULTS

Exercise tolerance (Tlim) and oxygen uptake were increased with PAV compared with sham ventilation. In contrast, end-exercise blood lactate/Tlim and leg effort/Tlim ratios were lower with PAV (p<0.05). There were no between-treatment differences in cardiac output and Spo(2) either at submaximal exercise or at Tlim (ie, Do(2)est remained unchanged with PAV; p>0.05). Leg muscle oxygenation, however, was significantly enhanced with PAV as the exercise-related decrease in Delta(O(2)Hb)% was lessened and TOI was improved; moreover, Delta(Hb(tot))%, an index of local blood volume, was increased compared with sham ventilation (p<0.01).

CONCLUSIONS

Respiratory muscle unloading during high-intensity exercise can improve peripheral muscle oxygenation despite unaltered systemic Do(2 )in patients with advanced COPD. These findings might indicate that a fraction of the available cardiac output had been redirected from ventilatory to appendicular muscles as a consequence of respiratory muscle unloading.

Relationship between induced sputum cytology and inflammatory status with lung structural and functional abnormalities in asbestosis

BACKGROUND

Asbestosis is associated with lung cellular and immunological abnormalities. Induced sputum cytology and local and systemic markers of inflammation may be helpful to characterize disease status and progression in these patients.

METHODS

Thirty-nine ex-workers with asbestosis on high-resolution CT (HRCT) and 21 non-exposed controls were evaluated. Sputum cytology and IL-8 in serum and sputum were related to lung function impairment.

RESULTS

Subjects with asbestosis had reduced sputum cellularity but higher macrophage/neutrophil ratio and % macrophage as compared with controls. Sputum and serum IL-8 were also higher in patients with asbestosis (P < 0.05). In addition, evidence of lung architectural distorption on HRCT was associated with increased levels of serum IL-8. Interestingly, absolute macrophage number was negatively correlated with total lung capacity (r = -0.40; P = 0.04) and serum IL-8 to lung diffusing capacity (r = -0.45; P = 0.01).

CONCLUSIONS

Occupationally exposed subjects with asbestosis on HRCT have cytologic abnormalities in induced sputum and increased local and systemic pro-inflammatory status which are correlated to functional impairment.

Asbestos-related diseases of the lungs and pleura: uses, trends and management over the last century

Asbestos is a descriptive term for a group of naturally occurring minerals known to mankind since ancient times. The main types of asbestos (chrysotile, and the amphiboles crocidolite and amosite) differ in chemical structure, biopersistence in human tissue and toxicity. Commercial exploitation, with little thought for environmental controls, increased over the twentieth century, particularly after World War II, to accommodate globalisation and the demands of the world's burgeoning cities. As its ill-health effects, both non-malignant (fibrosis of the lungs or asbestosis; pleural effusion, plaques and thickening) and malignant (mesothelioma, lung and other cancers), became evident, public pressure rose to control its use. The last decades of the last century saw decreases in exposure and rates of asbestosis in industrialised and in some less-industrialised countries, where pleural plaques and malignant mesothelioma are currently the most frequent manifestations of asbestos exposure. Longer follow-up of asbestos-exposed cohorts in mining and manufacturing has also strengthened the evidence of a fibre gradient in toxicity, with chrysotile exhibiting lower toxicity than the amphiboles, and amosite lower toxicity than crocidolite. The last decades of the twentieth century saw stabilisation and/or declines in mesothelioma rates in several industrialised countries. In less-industrialised countries, data on disease are sparse, exposure generally high and rates may peak in the future. Management of asbestos-related disease in the workplace requires collaboration between workers and unions (responsible for monitoring workplace dust levels, to which they must have access) and companies (responsible for engineering controls), reinforced by appropriate government regulations and by community support.

A step test to assess exercise-related oxygen desaturation in interstitial lung disease

A 6-min step test (6MST) may constitute a practical method for routinely assessing effort tolerance and exercise-related oxyhaemoglobin desaturation (ERD) in the primary care of patients with interstitial lung disease. In total, 31 patients (19 males) with idiopathic pulmonary fibrosis (n = 25) and chronic hypersensitivity pneumonia were submitted, on different days, to two 6MSTs. Physiological responses were compared with those found on maximal and submaximal cycle ergometer tests at the same oxygen uptake (V'(O(2))). Chronic breathlessness was also determined, as measured by the baseline dyspnoea index (BDI). Responses to 6MST were highly reproducible: 1.3+/-2.0 steps x min(-1), +/-5 beats x min(-1) (cardiac frequency), +/-50 mL x min(-1) (V'(O(2))), +/-7 L x min(-1) (minute ventilation) and +/-2% (arterial oxygen saturation measured by pulse oximetry (S(p,O(2)))). The number of steps climbed in 6 min was correlated to peak V'(O(2)) and the BDI. There were significant associations among the tests in relation to presence (change in S(p,O(2)) between rest and exercise > or = 4%) and severity (S(p,O(2)) <88%) of ERD. Four patients, however, presented ERD only in response to 6MST. Resting diffusing capacity of the lung for carbon monoxide and alveolar-arterial oxygen tension difference were the independent predictors of the number of steps climbed. A single-stage, self-paced 6-min step test provided reliable and reproducible estimates of exercise capacity and exercise-related oxyhaemoglobin desaturation in interstitial lung disease patients.

Inspiratory fraction and exercise impairment in COPD patients GOLD stages II-III

The inspiratory-to-total lung capacity ratio or "inspiratory fraction" (inspiratory capacity(IC)/total lung capacity (TLC)) may be functionally more representative than traditional indices of resting airflow limitation and lung hyperinflation in patients with chronic obstructive pulmonary disease (COPD). In the present retrospective study, a comparison was made of the individual performance of post-bronchodilator IC, IC/TLC and forced expiratory volume in one second (FEV(1)) in predicting a severely reduced peak oxygen uptake (V'(O(2)); <60% predicted) in 44 COPD patients Global Initiative for Chronic Obstructive Lung Disease stages II-III (post-bronchodilator FEV(1) ranging from 31-79% pred). Patients with lower IC/TLC values (<or=0.28) showed increased lung volumes and reduced exercise capacity as compared with other subjects. Following a multiple linear regression analysis, only IC/TLC and FEV(1) remained as independent predictors of V'(O(2)) (r(2) = 0.33). A receiver operating characteristic (ROC) curve analysis revealed that an IC/TLC <or=0.28 had the highest specificity (89.6%), positive predictive value (80%) and overall accuracy (86.3%) in identifying patients with V'(O(2)) <60% pred. In addition, the area under the ROC curve tended to be higher for IC/TLC than IC. In conclusion, post-bronchodilator total lung capacity-corrected inspiratory fraction provides useful information in addition to forced expiratory volume in one second and inspiratory capacity, to estimate the likelihood of chronic obstructive pulmonary disease patients to present with severely reduced maximal exercise capacity.

Avaliação da disfunção e da incapacidade nas pneumoconioses

A determinaçâo das conseqüências funcionais (disfunção) e do seu impacto na vida diária (incapacidade) são aspectos centrais da avalição de pacientes com doença ocupacional respiratória. A presente revisão apresenta as bases fundamentais para o entendimento dos instrumentos utilizados para a definição do grau de disfunção, incluindo aspectos clínicos, funcionais pulmonares e, em algumas circunstâncias, da capacidade de exercício. Em especial, apresenta-se uma classificação multifatorial do grau de disfunção com o intuito de nortear a concessão ou não de benefícios previdenciários em nosso meio.

Pleural Plaques in Asbestos-exposed Workers: Reproducibility of a New High-resolution CT Visual Semiquantitative Measurement Method

OBJECTIVE

To assess the reproducibility of a new high-resolution computed tomography (CT) visual semiquantitative method for pleural plaques in asbestos-exposed workers.

MATERIAL AND METHODS

We performed thin-section CT in 752 chrysotile asbestos mining workers and ex-workers. Institutional review board approval and signed written informed consent from subjects were obtained. Two readers independently evaluated the 752 CT scans and identified 57 workers (mean age +/- SD, 61.8 years +/- 8.1; range, 37 to 81 years) who had pleural plaques and no other pleural or parenchymal abnormality. Three independent radiologists then quantified the plaque burden in these 57 workers using a scoring system based on the evaluation of the maximum thickness of parietal pleural plaques and percentage of parietal pleural surface involvement. We also calculated the proportion between the number of CT slices with diaphragmatic plaques and the total number of slices in which the diaphragm was seen (pdiaph). The intraobserver and interobserver agreements were analyzed using weighted Kappa coefficient.

RESULTS

Interobserver agreements were good for the pleural plaque score (k = 0.61, 0.75, and 0.79) and ranged from good (k = 0.61) to excellent (k = 0.86) for the pdiaph. Intraobserver agreements ranged from good to excellent for the pleural plaque score (k = 0.79 and 1.00) and for the pdiaph (k = 0.79 and 0.93).

CONCLUSION

The method proposed for high-resolution CT pleural plaque quantification in asbestos-exposed workers has a high reproducibility.

Novas terapias ergogênicas no tratamento da doença pulmonar obstrutiva crônica

A doença pulmonar obstrutiva crônica é considerada, atualmente, uma doença sistêmica, cujas alterações estruturais e metabólicas podem levar à disfunção muscular esquelética. Esta afeta negativamente o desempenho muscular respiratório e periférico, a capacidade funcional, a qualidade de vida relacionada à saúde e mesmo a sobrevida. A indicação de suplementação de substâncias ergogênicas para pacientes com doença pulmonar obstrutiva crônica baseia-se no fato de que estas drogas podem evitar, ou minimizar, o catabolismo e/ou estimular a síntese protéica, diminuindo a depleção de massa muscular e aumentando a capacidade de exercício. A presente revisão sumariza o conhecimento disponível acerca da utilização de esteróides anabolizantes, creatina, L-carnitina, aminoácidos de cadeia ramificada e hormônio de crescimento em pacientes com doença pulmonar obstrutiva crônica. A vantagem do uso dessas substâncias ergogênicas parece residir no aumento da massa magra e/ou na indução de modificações bioenergéticas. Nesse contexto, a maior experiência acumulada é com os esteróides anabolizantes. Entretanto, os benefícios clínicos em relação à melhora da capacidade de exercício e força muscular, bem como os efeitos na morbimortalidade, não foram, até a presente data, consistentemente demonstrados. A suplementação ergogênica pode vir a se constituir numa ferramenta adjuvante para o tratamento de pacientes com doença pulmonar obstrutiva crônica avançada, especialmente naqueles com depleção muscular e/ou fraqueza periférica.

Placas pleurais relacionadas com o asbesto: Revisão da literatura

Pleural plaques (PP) are considered to be hallmarks of asbestos exposure. They constitute focal thickenings of the pleura and are commonly seen in patients without lung disease. They can involve parietal, diaphragmatic and mediastinal pleura. Chest x-ray is frequently used for PP diagnosis, but computed tomography, especially when used the high-resolution technique, is the imaging exam with the greatest sensibility and specificity. PP are almost always asymptomatic, but there are some controversial about their relationship with asbestos exposure indexes, pulmonary functional alterations and risk of neoplasias.

Alterações pleurais e parenquimatosas relacionadas com a exposição ao asbesto: Ensaio pictórico

Pleural and pulmonary asbestos-related diseases range from benign conditions, like pleural effusion and pleural plaques, to some neoplasias, such as lung cancer and malignant mesothelioma. Pleural effusion is the earliest finding after asbestos exposure, but the imaging findings are not specific. Diffuse pleural thickening involves the visceral pleura and pleural plaques are considered to be hallmarks of exposure. Asbestosis is the pulmonary fibrosis due to asbestos. Rounded atelectasis is a peripheral lung collapse in these individuals, generally related to pleural disease. Some neoplasias, like lung carcinoma and pleural mesothelioma, are more prevalent in asbestos-exposed subjects. The aim of this essay is to illustrate the main imaging findings of asbestos-related diseases.

Creatine supplementation during pulmonary rehabilitation in chronic obstructive pulmonary disease

BACKGROUND

Skeletal muscle wasting and dysfunction are strong independent predictors of mortality in patients with chronic obstructive pulmonary disease (COPD). Creatine nutritional supplementation produces increased muscle mass and exercise performance in health. A controlled study was performed to look for similar effects in 38 patients with COPD.

METHODS

Thirty eight patients with COPD (mean (SD) forced expiratory volume in 1 second (FEV(1)) 46 (15)% predicted) were randomised to receive placebo (glucose polymer 40.7 g) or creatine (creatine monohydrate 5.7 g, glucose 35 g) supplements in a double blind trial. After 2 weeks loading (one dose three times daily), patients participated in an outpatient pulmonary rehabilitation programme combined with maintenance (once daily) supplementation. Pulmonary function, body composition, and exercise performance (peripheral muscle strength and endurance, shuttle walking, cycle ergometry) took place at baseline (n = 38), post loading (n = 36), and post rehabilitation (n = 25).

RESULTS

No difference was found in whole body exercise performance between the groups: for example, incremental shuttle walk distance mean -23.1 m (95% CI -71.7 to 25.5) post loading and -21.5 m (95% CI -90.6 to 47.7) post rehabilitation. Creatine increased fat-free mass by 1.09 kg (95% CI 0.43 to 1.74) post loading and 1.62 kg (95% CI 0.47 to 2.77) post rehabilitation. Peripheral muscle performance improved: knee extensor strength 4.2 N.m (95% CI 1.4 to 7.1) and endurance 411.1 J (95% CI 129.9 to 692.4) post loading, knee extensor strength 7.3 N.m (95% CI 0.69 to 13.92) and endurance 854.3 J (95% CI 131.3 to 1577.4) post rehabilitation. Creatine improved health status between baseline and post rehabilitation (St George's Respiratory Questionnaire total score -7.7 (95% CI -14.9 to -0.5)).

CONCLUSIONS

Creatine supplementation led to increases in fat-free mass, peripheral muscle strength and endurance, health status, but not exercise capacity. Creatine may constitute a new ergogenic treatment in COPD.

Non-malignant consequences of decreasing asbestos exposure in the Brazil chrysotile mines and mills

AIMS

To investigate the consequences of improvement in the workplace environment over six decades (1940-96) in asbestos miners and millers from a developing country (Brazil).

METHODS

A total of 3634 Brazilian workers with at least one year of exposure completed a respiratory symptoms questionnaire, chest radiography, and a spirometric evaluation. The study population was separated into three groups whose working conditions improved over time: group I (1940-66, n = 180), group II (1967-76, n = 1317), and group III (1977-96, n = 2137).

RESULTS

Respiratory symptoms were significantly related to spirometric abnormalities, smoking, and latency time. Breathlessness, in particular, was also associated with age, pleural abnormality and increased cumulative exposure to asbestos fibres. The odds ratios (OR) for parenchymal and/or non-malignant pleural disease were significantly lower in groups II and III compared to group I subjects (0.29 (0.12-0.69) and 0.19 (0.08-0.45), respectively), independent of age and smoking status. Similar results were found when groups were compared at equivalent latency times (groups I v II: 30-45 years; groups II v III: 20-25 years). Ageing, dyspnoea, past and current smoking, and radiographic abnormalities were associated with ventilatory impairment. Lower spirometric values were found in groups I and II compared to group III: lung function values were also lower in higher quartiles of latency and of cumulative exposure in these subjects.

CONCLUSIONS

Progressive improvement in occupational hygiene in a developing country is likely to reduce the risk of non-malignant consequences of dust inhalation in asbestos miners and millers.

Dispnéia crônica e alterações funcionais respiratórias em ex-trabalhadores com asbestose avaliados para concessão de benefício

INTRODUÇÃO: A dispnéia é um sintoma de difícil avaliação, principalmente nas doenças ocupacionais. OBJETIVO: Avaliar a relação entre presença e intensidade de dispnéia crônica, e sua repercussão funcional em ex-trabalhadores com asbestose na avaliação de disfunção e incapacidade. MÉTODO: Escores de dispnéia pelas escalas Medical Research Council modificada, American Medical Association de 1984 e 1993 e Baseline Dyspnea Index foram obtidos em 40 ex-trabalhadores com diagnóstico de asbestose, os quais foram também submetidos a espirometria, medidas da capacidade de difusão pulmonar do monóxido de carbono e testes de exercício cardiopulmonar incremental e submáximo. RESULTADO: Dispnéia esteve presente em 72,5% e 67,5% dos indíviduos de acordo com as escalas do Medical Research Council e American Medical Association de 1984, respectivamente e em apenas 37,5% e 31,6% dos pacientes de acordo com as escalas American Medical Association de 1.993 e Baseline Dyspnea Index. Houve melhor concordância entre as escalas Medical Research Council e American Medical Association de 1993, e American Medical Association de 1984 e American Medical Association de 1993 quando as graduações "ausente" e "leve" foram agrupadas. Não foi observada relação significativa entre dispnéia de acordo com cada uma das escalas e presença de anormalidades funcionais no repouso e/ou exercício. CONCLUSÃO: O nível de concordância entre as escalas de dispnéia varia significativamente em indivíduos com asbestose. Há falta de relação dos índices de dispnéia com variáveis que avaliam disfunção respiratória em repouso e exercício.

The pattern and timing of breathing during incremental exercise: a normative study

Clinical evaluation of the pattern and timing of breathing during submaximal exercise can be valuable for the identification of the mechanical ventilatory consequences of different disease processes and for assessing the efficacy of certain interventions. Sedentary individuals (60 male/60 female, aged 20-80 yrs) were randomly selected from >8,000 subjects and submitted to ramp incremental cycle ergometry. Tidal volume (VT)/resting inspiratory capacity, respiratory frequency, total respiratory time (Ttot), inspiratory time (TI), expiratory time (TE), duty cycle (TI/Ttot) and mean inspiratory flow (VT/TI) were analysed at selected submaximal ventilatory intensities. Senescence and female sex were associated with a more tachypnoeic breathing pattern during isoventilation. The decline in Ttot was proportional to the TI and TE reductions, i.e. TI/Ttot was remarkably constant across age strata, independent of sex. The pattern, but not timing, of breathing was also influenced by weight and height; a set of demographically and anthropometrically based prediction equations are therefore presented. These data provide a frame of reference for assessing the normality of some clinically useful indices of the pattern and timing of breathing during incremental cycle ergometry in sedentary males and females aged 20-80 yrs.

Home based neuromuscular electrical stimulation as a new rehabilitative strategy for severely disabled patients with chronic obstructive pulmonary disease (COPD)

BACKGROUND

Passive training of specific locomotor muscle groups by means of neuromuscular electrical stimulation (NMES) might be better tolerated than whole body exercise in patients with severe chronic obstructive pulmonary disease (COPD). It was hypothesised that this novel strategy would be particularly effective in improving functional impairment and the consequent disability which characterises patients with end stage COPD.

METHODS

Fifteen patients with advanced COPD (nine men) were randomly assigned to either a home based 6 week quadriceps femoris NMES training programme (group 1, n=9, FEV(1)=38.0 (9.6)% of predicted) or a 6 week control period before receiving NMES (group 2, n=6, FEV(1)=39.5 (13.3)% of predicted). Knee extensor strength and endurance, whole body exercise capacity, and health related quality of life (Chronic Respiratory Disease Questionnaire, CRDQ) were assessed.

RESULTS

All patients were able to complete the NMES training programme successfully, even in the presence of exacerbations (n=4). Training was associated with significant improvements in muscle function, maximal and endurance exercise tolerance, and the dyspnoea domain of the CRDQ (p<0.05). Improvements in muscle performance and exercise capacity after NMES correlated well with a reduction in perception of leg effort corrected for exercise intensity (p<0.01).

CONCLUSIONS

For severely disabled COPD patients with incapacitating dyspnoea, short term electrical stimulation of selected lower limb muscles involved in ambulation can improve muscle strength and endurance, whole body exercise tolerance, and breathlessness during activities of daily living.

Peak VO2 correction for fat-free mass estimated by anthropometry and DEXA

PURPOSE

Anthropometric (ANTHRO) and dual-energy x-ray absorptiometric (DEXA) estimates of total body and leg fat-free masses (FFM) were obtained in 77 randomly selected sedentary men and women, aged 20-80: intermethod limits of agreement and their clinical significance, as inferred from the differences on peak VO2 corrected for FFMANTHRO and FFMDEXA, were determined.

METHODS

Limits of agreement were calculated as mean bias +/- 95% confidence intervals: peak VO2 at maximum cycle ergometry was related to FFMANTHRO and FFMDEXA by using both standard (y x x(-1)) and power function ratios (allometry).

RESULTS

Data distribution of the ANTHRO-DEXA differences presented significant heteroscedasticity in both sexes, i.e., differences were proportional to the mean (P < 0.05). After logarithmic transformation, the mean bias +/- 95% limits of agreement were expressed as ratios (ANTHRO x DEXA(-1) x// error ratio): these corresponded to 0.95 x// 1.11 or 0.99 x// 1.15 for total body FFM and 0.90 x// 1.10 or 1.02 x// 1.07 for leg FFM in men and women, respectively. In addition, we found different allometric exponents for FFMANTHRO and FFMDEXA: the intermethod differences, therefore, increased after power function expression (P < 0.05).

CONCLUSION

Discrepancies between ANTHRO and DEXA measurements of FFM depend on the magnitude of the estimate: differences are typically within 10 to 15%. Importantly, FFM-corrected peak VO2 values can vary according to the method chosen for body composition assessment, especially when allometry is used for peak VO2 correction. These results demonstrate that ANTHRO-DEXA differences in FFM estimation do have relevant practical consequences for the analysis of maximum aerobic capacity in nontrained humans.

Reference values for dynamic responses to incremental cycle ergometry in males and females aged 20 to 80

Interpretation of incremental cardiopulmonary exercise tests (CPET) might be enhanced by considering the simultaneous rates of change of certain key variables, e.g., Delta oxygen uptake/Delta work rate (Delta VO(2)/Delta WR), Delta heart rate/Delta VO(2) (Delta HR/Delta VO(2)), Delta ventilation/Delta carbon dioxide production (Delta VE/Delta VCO(2)), and the linearized Delta tidal volume/Delta VE (Delta VT/Delta lnVE) relationships. However, there are no published age- and sex-dependent reference values for these relationships that were appropriately obtained in randomly selected subjects. We therefore prospectively evaluated 120 sedentary individuals (60 male, 60 female, age 20 to 80 yr) who were randomly selected from more than 8,000 subjects, and submitted to standard ramp-incremental CPET on an electronically braked cycle ergometer. We found that sex and age significantly influenced several of the dynamic relationships, in addition to anthropometric attributes (p < 0.05). A comprehensive set of linear prediction equations is provided; the limits of normality (at the 95% confidence level) differed substantially from previous recommendations based on single discrete values. These data therefore provide a frame of reference for assessing the normalcy of the response profiles of four standard indices of metabolic, cardiovascular, and ventilatory function during rapidly incremental cycle ergometry in sedentary males and females up to 80 yr of age.

Heart rate at the estimated lactate threshold in patients with chronic obstructive pulmonary disease: effects on the target intensity for dynamic exercise training

BACKGROUND

Physical training at the range of exercise intensities associated with sustained blood lactate accumulation seems to rapidly improve aerobic performance in both healthy subjects and patients with chronic obstructive pulmonary disease (COPD). However, it is still unclear whether patients' heart rate (HR) at the estimated lactate threshold (HR [symbol: see text]L)--as expressed in percent attained peak HR (AHR), predicted peak HR (PHR) and HR reserve (HRR)--are comparable with the ranges of intensity that are commonly used for target exercise training in control subjects.

METHODS

The authors evaluated 26 patients with stable COPD (forced expiratory volume in 1 second = 1.17 +/- 0.28 L) who were submitted for spirometric evaluation, and, after familiarization, to a symptom-limited ramp-incremental cardiopulmonary exercise testing on a cycle ergometer.

RESULTS

The authors were able to identify [symbol: see text]L in only 18 patients (69%). The HR [symbol: see text]L corresponded to wide range of exercise intensities according to the three methods (ranging from 70-95% AHR, 50-90% PHR, and 35-60% HRR). However, most of the subjects would be trained within +/- 5% HR [symbol: see text]L if they had been exercised at 80 to 85% AHR and 40 to 45% HRR; these values correspond to higher (AHR) and lower (HRR) intensities than usually recommended for healthy subjects.

CONCLUSIONS

Considering that [symbol: see text]L was not identified in approximately one third of the patients and there was ample variability on HR [symbol: see text]L as %AHR, %PHR, and %HRR, the use of HR and [symbol: see text]L targets for routine exercise prescription does not seem to be clinically justifiable in patients with COPD submitted to pulmonary rehabilitation.

Determinants of the exercise endurance capacity in patients with chronic obstructive pulmonary disease. The power-duration relationship

To characterize the determinants of the power-duration (W-t) relationship in patients with chronic obstructive pulmonary disease (COPD), we evaluated 8 nonhypoxemic patients (FEV(1) = 1.27 +/- 0.26 L) and 10 healthy controls. After an initial maximum-incremental exercise test on cycle ergometer (peak), the subjects underwent four high-intensity constant-load tests to the limit of tolerance (t), each on different days. The W-t relationship was found to be hyperbolic in both groups. Absolute values of both the critical power asymptote (theta(F)) and the curvature constant (W') were lower in patients than in control subjects. However, when expressed as percentage of peak work rate theta(F) was significantly higher in patients compared with control subjects (81.8 +/- 3.3% versus 67.5 +/- 3.7%, respectively, p < 0.01). There were severe reductions in t in the patients that were consistently associated with higher breathlessness scores and V E/MVV ratios. Interestingly, all patients were able to sustain exercise at theta(F) for 20 min despite near-maximum physiological and subjective stresses. We conclude that the reductions of both parameters of the hyperbolic W-t relationship (theta(F) and W') in patients with COPD were due to the ventilatory constraints and their sensory consequences. Importantly, theta(F) separated a "sustainable" from a "nonsustainable" exercise-intensity domain: this parameter consistently occurred closer to peak work rate in patients than the healthy control subjects.

The effect of age on the power/duration relationship and the intensity-domain limits in sedentary men

The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W), at least in active and younger individuals [i.e. (W - thetaF)t = W', where thetaF is the critical power asymptote and W' is the curvature constant]. Little is known, however, about the combined effects of age and sedentarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60-75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, muVO2), estimated lactate threshold (VO2thetaL), VO2thetaF, and W' (P < 0.05). Interestingly, however, both VO2thetaL and VO2thetaF, when expressed as a percentage of muVO2, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the "moderate", sub-thetaL exercise-intensity domain (+30.4%), mainly at the expense of the "very-heavy", supra-thetaF domain (-56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (thetaF) and anaerobic (W') determinants of the W/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity.

Oxygen cost for cycling as related to leg mass in males and females, aged 20 to 80

In order to evaluate the determinants of the metabolic cost for cycle ergometry, we analyzed the relationship between VO2 and leg mass (LM) and total body mass (TBM) in 71 randomly-selected sedentary subjects (34 men), aged 20 to 80. Participants performed constant work rate (WR) tests at 0, 25, and 50 W (at 60 rpm) for 6 minutes in a randomized sequence: gross VO2, gross efficiency, and work efficiency were related to TBM and LM as assessed by dual energy x-ray absorptiometry. We found that gross VO2 and gross efficiency were more strongly related to LM than TBM but work efficiency values were independent of both (P>0.05). Significantly higher values of VO2TBM were found in subjects with large LM/TBM ratios and vice-versa; VO2/LM, however, did not change with anthropometric characteristics. Gross VO2 (mL/min) was predicted by a LM-based equation (10.6 [WR, W] + 16.8 [LM, kg] +75) with a mean error below 5%: this equation predicted the cost more accurately than previous TBM-based formulations (P<0.01). We conclude that leg mass actually provides the preferred frame of reference for predicting the oxygen cost for cycle ergometry at 60 rpm in sedentary subjects, independent of age or gender.