Exercise intolerance in post-COVID19 survivors after hospitalization

Rationale

Post-COVID19 survivors frequently have dyspnea that can lead to exercise intolerance and lower quality of life. Despite recent advances, the pathophysiological mechanisms of exercise intolerance in the post-COVID19 patients remain incompletely characterized.

Objectives

To clarify the mechanisms of exercise intolerance in post-COVID19 survivors after hospitalization.

Methods

Prospective study evaluated consecutive patients previously hospitalized due to moderate-to-severe/critical COVID19. Within 90±10 days (mean±sd) of COVID19 acute symptoms onset, patients underwent a comprehensive cardiopulmonary assessment, including a cardiopulmonary exercise testing with earlobe arterialized capillary blood gas analysis.

Measurements and Main Results

Eighty-seven patients were evaluated, their mean±sdpeak oxygen consumption were 19.5±5.0 ml kg−1·min−1, and the tertiles were: ≤17.0, 17.1–22.2 and ≥22.3 ml kg−1·min−1. Hospitalization severity was similar among the three groups; however, at the follow-up visit, they reported a greater sensation of dyspnea, along with indices of impaired pulmonary function, and abnormal ventilatory, gas-exchange and metabolic responses during exercise compared to patients with peak oxygen consumption >17 ml kg−1·min−1. By multivariate logistic regression analysis (ROC curve analysis) adjusted for age, sex and pulmonary embolism, a peak dead space fraction of tidal volume ≥29 and a resting forced vital capacity ≤80%predicted were independent predictors of reduced peak oxygen consumption.

Conclusions

Exercise intolerance in the post-COVID19 survivors was related to a high dead space fraction of tidal volume at peak exercise and a decreased resting forced vital capacity, suggesting that both pulmonary microcirculation injury and ventilatory impairment could influence aerobic capacity in this patient population.

Risk prediction for Obstructive Sleep Apnea prognostic in Obese patients referred for bariatric surgery

OBJECTIVES

(i) To assess the anthropometric measurements, along with the clinical characteristics and quality of life profiles of the studied patients; (ii) To determine the occurrence and severity of Obstructive Sleep Apnea (OSA), using polysomnography; and (iii) To identify the best anthropometric and clinical indicators to predict OSA in obese patients who are candidates for bariatric surgery.

METHODS

a prospective observational study conducted in a private clinic, using consecutive sampling of patients eligible for bariatric surgery with a BMI ≥ 40, or with a BMI of ≥ 35 kg/m² accompanied by comorbidities associated with obesity.

RESULTS

Sixty patients were initially selected, of whom 46 agreed to take part in the preoperative evaluation. OSA was observed in 76% of patients, 59% of whom had moderate-to-severe OSA, with a predominance of men in these groups. Among the variables suggesting statistical difference between groups, waist-to-hip ratio (WHR) was the only clinical factor associated with scores the apnea hypopnea index (AHI) ≥ 15, with a cut-off value of 0.95. The results showed that patients scoring above 0.95 are three times more likely to have moderate-to-severe apnea.

CONCLUSION

The best risk factor for the prognostic of moderate-to-severe OSA was presenting a WHR score with a cut-off value of 0.95 or above.

Proportional Assist Ventilation Improves Leg Muscle Reoxygenation After Exercise in Heart Failure With Reduced Ejection Fraction

Background

Respiratory muscle unloading through proportional assist ventilation (PAV) may enhance leg oxygen delivery, thereby speeding off-exercise oxygen uptake ( V . ⁢ O 2 ) kinetics in patients with heart failure with reduced left ventricular ejection fraction (HFrEF).

Methods

Ten male patients (HFrEF = 26 ± 9%, age 50 ± 13 years, and body mass index 25 ± 3 kg m²) underwent two constant work rate tests at 80% peak of maximal cardiopulmonary exercise test to tolerance under PAV and sham ventilation. Post-exercise kinetics of V . ⁢ O 2 , vastus lateralis deoxyhemoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy, and cardiac output (Q _T ) by impedance cardiography were assessed.

Results

PAV prolonged exercise tolerance compared with sham (587 ± 390 s vs. 444 ± 296 s, respectively; p = 0.01). PAV significantly accelerated V . ⁢ O 2 recovery (τ = 56 ± 22 s vs. 77 ± 42 s; p < 0.05), being associated with a faster decline in Δ[deoxy-Hb + Mb] and Q _T compared with sham (τ = 31 ± 19 s vs. 42 ± 22 s and 39 ± 22 s vs. 78 ± 46 s, p < 0.05). Faster off-exercise decrease in Q _T with PAV was related to longer exercise duration (r = -0.76; p < 0.05).

Conclusion

PAV accelerates the recovery of central hemodynamics and muscle oxygenation in HFrEF. These beneficial effects might prove useful to improve the tolerance to repeated exercise during cardiac rehabilitation.

CRITICAL VS ESTIMATED HEART RATE IN ELDERLY SUBJECTS

ABSTRACT Introduction: Heart rate (HR) has been a simple and easy-to-use physiological parameter widely used to determine exercise intensity. The critical power fatigue limit model, known as the critical heart rate (CHR), can be extrapolated to HR. However, an estimate for a CHR mathematical model has not yet been extrapolated for upper limb exercise in the elderly. Objective: To compare the mathematical model previously used to estimate CHR with the heart rate values at the critical power (CP) during arm-ergometer exercises in elderly subjects. Methods: After an initial maximum-incremental exercise test on a cycle arm-ergometer, seven elderly people performed four high-intensity constant-load tests to the limit of tolerance (Tlim), to determine CP and critical heart rate (CHR). For each power output, the heart rate of the last five seconds (HRlim) and total time to exhaustion (in minutes) were obtained. The slope coefficients of the regression lines between HRlim and Tlim were defined as CHR, and between Wlim and Tlim as CP. A square-wave test was performed on a different day, in the power determined as equivalent to CP, and the heart rate at CP (CPHR) was assessed. Results: The HR-Tlim relationship was found to be hyperbolic in all subjects, who were able to sustain upper-limb exercise at CP for 20 min. CP attained 66.8±9.4% of peak work rate in the ramp test. The real average HR measured in the CP test was strikingly similar to the CHR calculated by the mathematical model of PC (137.6±16.9 versus 139.7±13.3bpm, respectively, p=0.53). There was strong correlation between the real and the estimated CHR. Conclusion: This study indicated that the maximal sustainable exercise intensity can be based on a physiological variable such as HR, and the CHR test can define exercise endurance, which can be useful in performance assessment and training prescription. Level of evidence II; Diagnostic studies – Investigating a diagnostic test.

Incremental step test in patients with pulmonary hypertension

Cardiopulmonary exercise testing (CPET) on a treadmill or cycle ergometer provides an integrated assessment of the cardiorespiratory system during exertion and is widely used in clinical practice. An incremental step test (IST) can be an alternative for eliciting maximal exercise responses. Therefore, 20 patients with pre-capillary PH (65% female, 41 ± 15 yrs) randomly performed a symptom-limited CPET on a cycle ergometer and IST. Metabolic, cardiovascular, ventilatory and gas exchange variables were recorded during both tests. There was a greater desaturation and higher V̇O_2PEAK in IST compared to CPET. The V̇O_2GET, HR _PEAK (% pred), ΔV̇E/ΔV̇CO₂ and ΔHR/ΔV̇O₂ were similar in both IST and CPET. By linear regression analyses, the work performed on IST [W = (mass × 9,8 m/s2 x vertical distance)] was a predictor of peak V̇O₂ independent of the gender and age (r² = 077, p = 0001). In conclusion, IST elicited higher peak cardiopulmonary responses and has a good agreement with known severity markers in patients with pre-capillary PH.

Critical power for the upper limb in patients with chronic obstructive pulmonary disease: A pilot study

PURPOSE

To investigated the impact of the ventilatory constraints in the power-duration relationship for upper limbs exercise in patients with chronic obstructive pulmonary disease (COPD).

METHODS

Eight patients with COPD and eight healthy subjects performed an arm incremental test on cycle ergometer and four constant workload tests (100%, 90%, 80% and 70% of peak workload). The power-duration (or critical power - CP) estimative was determined. The inspiratory capacity was measured before and after each test.

RESULTS

There was no significant difference in the CP between patients and controls. Also, the curvature constant (W_AT, work do able above CP) was similar between patients and control subjects. Finally, the limits of tolerance for all constant workload tests in the patients with COPD were closely associated with the presence of dynamic hyperinflation and ventilatory reserve.

CONCLUSION

Despite patients typically showed more ventilatory stress compared with control subjects, the ventilatory constraints did not limit the sustained upper limbs exercise at the critical power.

Increased rate of osteoporosis, low lean mass, and fragility fractures in COPD patients: association with disease severity

A very high rate of osteoporosis, fractures, and low lean mass was observed in patients with chronic obstructive pulmonary disease (COPD). Disease severity was associated with bone and muscle adverse outcomes, while age ≥ 63.5 years old, low lean mass, higher iPTH, and a T-score below - 2.5 were all associated with higher risk of fracture.

INTRODUCTION

Osteoporosis is frequently neglected in patients with COPD. We aimed at evaluating the rate of osteoporosis, fractures, and low lean mass in patients with COPD.

METHODS

Ninety-nine patients with COPD (53 women, 64.5 ± 9.6 years old, and 46 men, 65.9 ± 8.0 years old) underwent bone densitometry (DXA) with body composition analyses. Healthy individuals (N = 57) not exposed to tobacco matched by sex, age, and body mass index (BMI) were used as controls. Spirometry, routine laboratory workout, and conventional thoracolumbar radiography surveying for vertebral deformities were performed in all patients.

RESULTS

Osteoporosis was found in 40.4% of the COPD patients against only 13.0% of the healthy controls (p = 0.001). Vertebral fractures were seen in 24.4% of the men and 22.0% of the women with COPD. Disease severity (GOLD 3 and 4) was significantly associated with higher risk of vitamin D deficiency (p = 0.032), lower BMD (both men and women at all sites), higher frequency of osteoporosis (in women at all sites), lower skeletal mass index, and higher rate of low lean mass (in both men and women) than healthy controls and COPD patients with milder disease (GOLD 1 and 2). Age was a main predictor of vertebral fractures (OR = 1.164 (1.078-9.297); p < 0.001), while high plasma iPTH (OR = 1.045 (1.005-1.088); p = 0.029) and low ALM (OR = 0.99965 (0.99933-0.99997); p = 0.031) were predictors of non-vertebral fractures.

CONCLUSION

Highly prevalent in COPD, osteoporosis and low lean mass were associated with FEV_1% < 50%. Age, low lean mass, high iPTH, and low bone mass were all significantly associated with fractures in COPD patients.

Clinical usefulness of end-tidal CO2 profiles during incremental exercise in patients with chronic thromboembolic pulmonary hypertension

INTRODUCTION

Great ventilation to carbon dioxide output (ΔV˙E/ΔV˙CO₂) and reduced end-tidal partial pressures for CO₂ (PetCO₂) during incremental exercise are hallmarks of chronic thromboembolic pulmonary hypertension (CTEPH) and idiopathic pulmonary arterial hypertension (IPAH). However, CTEPH is more likely to involve proximal arteries, which may lead to poorer right ventricle-pulmonary vascular coupling and worse gas exchange abnormalities. Therefore, abnormal PetCO₂ profiles during exercise may be more prominent in patients with CTEPH and could be helpful to indicate disease severity.

METHODS

Seventy patients with CTEPH and 34 with IPAH underwent right heart catheterization and cardiopulmonary exercise testing. According to PetCO₂ pattern during exercise, patients were classified as having an increase or stabilization in PetCO₂ up to the gas exchange threshold (GET), an abrupt decrease in the rest-exercise transition or a progressive and slow decrease throughout exercise. A subgroup of patients with CTEPH underwent a constant work rate exercise test to obtain arterial blood samples during steady-state exercise.

RESULTS

Multivariate logistic regression analyses showed that progressive decreases in PetCO₂ and SpO₂ were better discriminative parameters than ΔV˙E/ΔV˙CO₂ to distinguish CTEPH from IPAH. This pattern of PetCO₂ was associated with worse functional impairment and greater reduction in PaCO₂ during exercise.

CONCLUSION

Compared to patients with IPAH, patients with CTEPH present more impaired gas exchange during exercise, and PetCO₂ abnormalities may be used to identify more clinically and hemodynamically severe cases.

Update on the use of portable monitoring system for the diagnosis of sleep apnea in specific population

The prevalence and severity of obstructive sleep apnea (OSA) is higher in specific population: children, elderly, obese and patients with pulmonary and cardiovascular diseases, compared to the general population. OSA is associated with greater morbidity and mortality in these patients. Although full-night polysomnography is still the gold standard diagnostic sleep study for OSA, it is a time consuming, expensive and technically demanding exam. Over the last few years, there is growing evidence on the use of portable monitors (PM) as an alternative for the diagnosis of OSA. These devices were developed specially for sleep evaluation at home, at a familiar environment, with easy self-application of monitoring, unattended. The use of PM is stablished for populations with high pre-test probability of OSA. However, there is a lack of studies on the use of PM in age extremes and patients with comorbidities. The purpose of this review is to present the studies that evaluated the use of PM in specific population, as well as to describe the advantages, limitations and applications of these devices in this particular group of patients. Although the total loss rate of recordings is variable in different studies, the agreement with full-night polysomnography justifies the use of PM in this population.

Screening of miners and millers at decreasing levels of asbestos exposure: comparison of chest radiography and thin-section computed tomography

BACKGROUND

Chest radiography (CXR) is inferior to Thin-section computed tomography in the detection of asbestos related interstitial and pleural abnormalities. It remains unclear, however, whether these limitations are large enough to impair CXR´s ability in detecting the expected reduction in the frequency of these asbestos-related abnormalities (ARA) as exposure decreases.

METHODS

Clinical evaluation, CXR, Thin-section CT and spirometry were obtained in 1418 miners and millers who were exposed to progressively lower airborne concentrations of asbestos. They were separated into four groups according to the type, period and measurements of exposure and/or procedures for controlling exposure: Group I (1940-1966/tremolite and chrysotile, without measurements of exposure and procedures for controlling exposure); Group II (1967-1976/chrysotile only, without measurements of exposure and procedures for controlling exposure); Group III (1977-1980/chrysotile only, initiated measurements of exposure and procedures for controlling exposure) and Group IV (after 1981/chrysotile only, implemented measurements of exposure and a comprehensive procedures for controlling exposure).

RESULTS

In all groups, CXR suggested more frequently interstitial abnormalities and less frequently pleural plaques than observed on Thin-section CT (p<0.050). The odds for asbestosis in groups of decreasing exposure diminished to greater extent at Thin-section CT than on CXR. Lung function was reduced in subjects who had pleural plaques evident only on Thin-section CT (p<0.050). In a longitudinal evaluation of 301 subjects without interstitial and pleural abnormalities on CXR and Thin-section CT in a previous evaluation, only Thin-section CT indicated that these ARA reduced as exposure decreased.

CONCLUSIONS

CXR compared to Thin-section CT was associated with false-positives for interstitial abnormalities and false-negatives for pleural plaques, regardless of the intensity of asbestos exposure. Also, CXR led to a substantial misinformation of the effects of the progressively lower asbestos concentrations in the occurrence of asbestos-related diseases in miners and millers.

Effect of L-carnitine on exercise performance in patients with mitochondrial myopathy

Exercise intolerance due to impaired oxidative metabolism is a prominent symptom in patients with mitochondrial myopathy (MM), but it is still uncertain whether L-carnitine supplementation is beneficial for patients with MM. The aim of our study was to investigate the effects of L-carnitine on exercise performance in MM. Twelve MM subjects (mean age±SD=35.4±10.8 years) with chronic progressive external ophthalmoplegia (CPEO) were first compared to 10 healthy controls (mean age±SD=29±7.8 years) before they were randomly assigned to receive L-carnitine supplementation (3 g/daily) or placebo in a double-blind crossover design. Clinical status, body composition, respiratory function tests, peripheral muscle strength (isokinetic and isometric torque) and cardiopulmonary exercise tests (incremental to peak exercise and at 70% of maximal), constant work rate (CWR) exercise test, to the limit of tolerance [Tlim]) were assessed after 2 months of L-carnitine/placebo administration. Patients with MM presented with lower mean height, total body weight, fat-free mass, and peripheral muscle strength compared to controls in the pre-test evaluation. After L-carnitine supplementation, the patients with MM significantly improved their Tlim (14±1.9 vs 11±1.4 min) and oxygen consumption (V˙O2) at CWR exercise, both at isotime (1151±115 vs 1049±104 mL/min) and at Tlim (1223±114 vs 1060±108 mL/min). These results indicate that L-carnitine supplementation may improve aerobic capacity and exercise tolerance during high-intensity CWRs in MM patients with CPEO.

Contrasting cardiopulmonary responses to incremental exercise in patients with schistosomiasis-associated and idiopathic pulmonary arterial hypertension with similar resting hemodynamic impairment

It has been reported that schistosomiasis-associated PAH (Sch-PAH) has a more benign clinical course compared with idiopathic PAH (IPAH). We therefore hypothesized that Sch-PAH subjects would present with less impaired cardiopulmonary and metabolic responses to exercise than IPAH patients, even with similar resting pulmonary hemodynamic abnormalities. The aim of this study was to contrast physiologic responses to incremental exercise on cycle ergometer between subjects with Sch-PAH and IPAH. We performed incremental cardiopulmonary exercise tests (CPET) in subjects newly diagnosed with IPAH (n = 9) and Sch-PAH (n = 8), within 1 month of the hemodynamic study and before the initiation of specific therapy for PAH. There were no significant between-group differences in cardiac index, pulmonary vascular resistance or mean pulmonary artery pressure. However, mean peak oxygen uptake (VO₂) was greater in Sch-PAH than IPAH patients (75.5±21.4 vs 54.1±16.1% predicted, p = 0.016), as well as the ratio of increase in VO₂ to work rate (8.2±1.0 vs 6.8±1.8 mL/min/W, p = 0.03). Additionally, the slope of the ventilatory response as a function of CO₂ output was lower in Sch-PAH (40.3±3.9 vs 55.6±19.8; p = 0.04), and the heart rate response for a given change in VO₂ was also diminished in Sch-PAH compared to IPAH (80.1±20.6 vs 123.0±39.2 beats/L/min; p = 0.02). In conclusion, Sch-PAH patients had less impaired physiological responses to exercise than IPAH subjects with similar resting hemodynamic dysfunction. Our data suggest a more preserved cardiopulmonary response to exercise in Sch-PAH which might be related to its better clinical course compared to IPAH.

Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V CW) = rib cage (V RC) + abdomen (V AB)] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) V CW increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V CW regulation as EEV CW increased non-linearly in 17/30 "hyperinflators" and decreased in 13/30 "non-hyperinflators" (P < 0.05). EEV AB decreased slightly in 8 of the "hyperinflators", thereby reducing and slowing the rate of increase in end-inspiratory (EI) V CW (P < 0.05). In contrast, decreases in EEV CW in the "non-hyperinflators" were due to the combination of stable EEV RC with marked reductions in EEV AB. These patients showed lower EIV CW and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIV CW regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

Is portable monitoring accurate in the diagnosis of obstructive sleep apnea syndrome in chronic pulmonary obstructive disease?

BACKGROUND

No scientific evidence supports the use of portable devices to diagnose obstructive sleep apnea syndrome (OSAS) in patients with co-morbities. Our aim was to evaluate the accuracy of a portable monitoring device (Stardust - STD) in the detection of patients with chronic obstructive pulmonary disease (COPD).

METHODS

Patients with COPD and clinical suspicion of OSAS were recruited for a prospective randomized study. The STD was used on two different nights: (1) at home (STDHome) and (2) at the sleep laboratory simultaneous with polysomnography (PSG-STDLab).

RESULTS

A total of 72 patients underwent the proposed recordings. Forty-six volunteers were excluded due to recording problems, and data from 26 subjects were analyzed. The mean age was (mean±SD) 62.8±8.5 years, 50% were male, and the mean forced expiratory volume in the first second was 55±11%. Significant intraclass correlation was observed between apnea-hypopnea index (AHI)-PSG vs. AHI-STDLab (r=0.61, p<0.0001) and AHI-STDHome (r=0.47, p<0.007). Kappa analysis also showed a significant agreement for severe group.

CONCLUSION

Despite the agreement found in a small number of patients between AHI, a large number of failures in the recording limits the use of this portable device for the diagnosis of OSAS in patients with COPD.

Skeletal muscle reoxygenation after high-intensity exercise in mitochondrial myopathy

This study addressed whether O(2) delivery during recovery from high-intensity, supra-gas exchange threshold exercise would be matched to O(2) utilization at the microvascular level in patients with mitochondrial myopathy (MM). Off-exercise kinetics of (1) pulmonary O(2) uptake VO(2P) (2) an index of fractional O(2) extraction by near-infrared spectroscopy (Δ[deoxy-Hb + Mb]) in the vastus lateralis and (3) cardiac output (Q'(T)) by impedance cardiography were assessed in 12 patients with biopsy-proven MM (chronic progressive external ophthalmoplegia) and 12 age- and gender-matched controls. Kinetics of VO(2P) were significantly slower in patients than controls (τ = 53.8 ± 16.5 vs. 38.8 ± 7.6 s, respectively; p < 0.05). Q'(T), however, declined at similar rates (τ = 64.7 ± 18.8 vs. 73.0 ± 21.6 s; p > 0.05) being typically slower than [Formula: see text] in both groups. Importantly, Δ[deoxy-Hb + Mb] dynamics (MRT) were equal to, or faster than, τVO(2P) in patients and controls, respectively. In fact, there were no between-group differences in τVO(2P)MRTΔ[deoxy-Hb + Mb] (1.1 ± 0.4 vs. 1.0 ± 0.2, p > 0.05) thereby indicating similar rates of microvascular O(2) delivery. These data indicate that the slower rate of recovery of muscle metabolism after high-intensity exercise is not related to impaired microvascular O(2) delivery in patients with MM. This phenomenon, therefore, seems to reflect the intra-myocyte abnormalities that characterize this patient population.

Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ) of oxygen consumption (VO(2)) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the VO(2) on-exercise mean response time (MRT) and the gas exchange threshold (GET). The ΔVO(2)/ΔWR slope was calculated up to GET (S(1)), above GET (S(2)) and over the entire linear portion of the response (S(T)). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak VO(2) and muscle performance were lower in patients than controls (P < 0.05). Patients had significantly lower ΔVO(2)/ΔWR than controls, especially the S(2) component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min(-1)·W(-1), respectively; P < 0.001). There were significant relationships between ΔVO(2)/ΔWR (S(T)) and muscle endurance, MRT-VO(2), GET and peak VO(2) in MM patients (P < 0.05). In fact, all patients with ΔVO(2)/ΔWR below 8 mL·min(-1)·W(-1) had severely reduced peak VO(2) values (<60% predicted). Moreover, patients with higher cardiopulmonary stresses during exercise (e.g., higher Δ ventilation/carbon dioxide output and Δ heart rate/ΔVO(2)) had lower ΔVO(2)/ΔWR (P < 0.05). In conclusion, a readily available, effort-independent index of aerobic dysfunction during dynamic exercise (ΔVO(2)/ΔWR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress.

Neuromuscular electrical stimulation improves exercise tolerance in chronic obstructive pulmonary disease patients with better preserved fat-free mass

BACKGROUND

High-frequency neuromuscular electrical stimulation increases exercise tolerance in patients with advanced chronic obstructive pulmonary disease (COPD patients). However, it is conceivable that its benefits are more prominent in patients with better-preserved peripheral muscle function and structure.

OBJECTIVE

To investigate the effects of high-frequency neuromuscular electrical stimulation in COPD patients with better-preserved peripheral muscle function.

DESIGN

Prospective and cross-over study.

METHODS

Thirty COPD patients were randomly assigned to either home-based, high-frequency neuromuscular electrical stimulation or sham stimulation for six weeks. The training intensity was adjusted according to each subject's tolerance. Fat-free mass, isometric strength, six-minute walking distance and time to exercise intolerance (Tlim) were assessed.

RESULTS

Thirteen (46.4%) patients responded to high-frequency neuromuscular electrical stimulation; that is, they had a post/pre Δ Tlim >10% after stimulation (unimproved after sham stimulation). Responders had a higher baseline fat-free mass and six-minute walking distance than their seventeen (53.6%) non-responding counterparts. Responders trained at higher stimulation intensities; their mean amplitude of stimulation during training was significantly related to their fat-free mass (r = 0.65; p<0.01). Logistic regression revealed that fat-free mass was the single independent predictor of Tlim improvement (odds ratio [95% CI] = 1.15 [1.04-1.26]; p<0.05).

CONCLUSIONS

We conclude that high-frequency neuromuscular electrical stimulation improved the exercise capacity of COPD patients with better-preserved fat-free mass because they tolerated higher training stimulus levels. These data suggest that early training with high-frequency neuromuscular electrical stimulation before tissue wasting begins might enhance exercise tolerance in patients with less advanced COPD.

Evaluation of the upper airway in obstructive sleep apnoea

The evaluation of the upper airway (UA) includes the physical examination of pharyngeal structures and a number of imaging techniques that vary from the mostly used lateral cephalometry and computed tomography to more sophisticated methods such as tri-dimensional magnetic resonance image (MRI). Other complex techniques addressing UA collapsibility assessed by measurement of pharyngeal critical pressure and negative expiratory pressure however are not routinely performed. These methods provide information about anatomic abnormalities and the level of pharyngeal narrowing or collapse while the patient is awake or asleep. Data suggest that individual patients have different patterns of UA narrowing. So, the best method for evaluating obstruction during obstructive events remains controversial. In general, in clinical practice physical examination including a systematic evaluation of facial morphology, mouth, nasal cavity and the pharynx as well as simple imaging techniques such as nasopharyngoscopy and cephalometry have been more routinely utilized. Findings associated with obstructive sleep apnoea (OSA) are UA narrowing by the lateral pharyngeal walls and enlargements of tonsils, uvula and tongue. Additionally cephalometry identifies the most significant craniofacial characteristics associated with this disease. MRI studies demonstrated that lateral narrowing of UA in OSA is due to parapharyngeal muscle hypertrophy and/or enlargement of non adipose soft tissues. The upper airway evaluation has indubitably contributed to understand the pathophysiology and the diagnosis of OSA and snoring. Additionally, it also helps to identify the subjects with increased OSA risk as well as to select the more appropriate modality of treatment, especially for surgical procedures.

Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF

Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O(2) pressure and decrease the rate of O(2) transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e.g., angiotensin-converting enzyme inhibitors and third-generation beta-blockers) may have improved microvascular O(2) delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O(2) uptake (Vo(2)) kinetics. We assessed the rate of change of pulmonary Vo(2) (Vo(2)(p)), (estimated) fractional O(2) extraction in the vastus lateralis (approximately Delta[deoxy-Hb+Mb] by near-infrared spectroscopy), and cardiac output (Qt) during high-intensity exercise performed to the limit of tolerance (Tlim) in 10 optimally treated sedentary patients (ejection fraction = 29 + or - 8%) and 11 controls. Sluggish Vo(2)(p) and Qt kinetics in patients were significantly related to lower Tlim values (P < 0.05). The dynamics of Delta[deoxy-Hb+Mb], however, were faster in patients than controls [mean response time (MRT) = 15.9 + or - 2.0 s vs. 19.0 + or - 2.9 s; P < 0.05] with a subsequent response "overshoot" being found only in patients (7/10). Moreover, tauVo(2)/MRT-[deoxy-Hb+Mb] ratio was greater in patients (4.69 + or - 1.42 s vs. 2.25 + or - 0.77 s; P < 0.05) and related to Qt kinetics and Tlim (R = 0.89 and -0.78, respectively; P < 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in "central" and "peripheral" circulatory adjustments still play a prominent role in limiting Vo(2)(p) kinetics and tolerance to heavy-intensity exercise in nontrained patients.

Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure

Blood flow requirements of the respiratory muscles (RM) increase markedly during exercise in chronic heart failure (CHF). We reasoned that if the RM could subtract a fraction of the limited cardiac output (QT) from the peripheral muscles, RM unloading would improve locomotor muscle perfusion. Nine patients with CHF (left ventricle ejection fraction = 26 ± 7%) undertook constant-work rate tests (70-80% peak) receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Δ%) in deoxy-hemoglobyn, oxi-Hb ([O2Hb]), tissue oxygenation index, and total Hb ([HbTOT], an index of local blood volume) in the vastus lateralis were measured by near infrared spectroscopy. In addition, QT was monitored by impedance cardiography and arterial O2 saturation by pulse oximetry (SpO2). There were significant improvements in exercise tolerance (Tlim) with PAV. Blood lactate, leg effort/Tlim and dyspnea/Tlim were lower with PAV compared with sham ventilation ( P < 0.05). There were no significant effects of RM unloading on systemic O2 delivery as QT and SpO2 at submaximal exercise and at Tlim did not differ between PAV and sham ventilation ( P > 0.05). Unloaded breathing, however, was related to enhanced leg muscle oxygenation and local blood volume compared with sham, i.e., higher Δ[O2Hb]% and Δ[HbTOT]%, respectively ( P < 0.05). We conclude that RM unloading had beneficial effects on the oxygenation status and blood volume of the exercising muscles at similar systemic O2 delivery in patients with advanced CHF. These data suggest that blood flow was redistributed from respiratory to locomotor muscles during unloaded breathing.

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.

Methacholine vs adenosine on intra and extrathoracic airway hyperresponsiveness in patients with cough variant asthma

BACKGROUND

Airway hyperresponsiveness (AHR) can be studied by bronchoprovocation test (BPT) using direct (methacholine - MCh) or indirect (adenosine 5'-monophosphate - AMP) stimuli. These two substances have not been compared in cough variant asthma (CVA).

OBJECTIVE

We designed a randomized, single-blind, cross-over study to compare AMP and MCh in the detection of CVA. Additionally, we examined whether assessment of extrathoracic airway hyperresponsiveness (EAHR) during MCh and AMP helped in the evaluation of CVA.

METHODS

Patients with CVA with previous positive MCh BPT performed challenges with AMP and MCh. The variables were: (i) a provocative dose producing a 20% fall in forced expiratory volume in 1 s (FEV(1)) value (PD(20)MCh); (ii) a provocative dose producing a 25% fall in the maximal mid-inspiratory flow (FIF(50)) from baseline (PD(25)MCh) for MCh; (iii) a provocative concentration producing a 20% fall in FEV(1) value (PC(20)AMP) and (iv) a provocative concentration producing a 25% fall in the FIF(50) from baseline (PC(25)AMP) for AMP.

RESULTS

All 113 patients with CVA responded to PD(20)MCh and 96% and 69% responded to PC(20)AMP, if we used PC(20) </= 200 mg/ml or PC(20) </= 100 mg/ml, respectively, with an excellent correlation between these two tests (r = 0.87 and 0.76, respectively). Extrathoracic AHR associated with AHR was found in 10% in MCh challenge and in 11% with AMP challenge and no patients had EAHR alone.

CONCLUSION

Adenosine challenges correlate well with MCh in patients with CVA. A minority (c. 10%) of CVA patients have EAHR as measured by these tests, while most had AHR as assessed with each of the challenge agents.

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.

High-dose inhaled beclomethasone treatment in patients with chronic cough: a randomized placebo-controlled study

BACKGROUND

It is important to determine whether chronic cough is associated with asthma and can be helped by treatment with inhaled corticosteroids.

OBJECTIVE

To compare the effects of beclomethasone and placebo in patients with chronic cough for at least 8 weeks after excluding those with cough due to postnasal drip and gastroesophageal reflux disease.

METHODS

A prospective, randomized, double-blind, placebo-controlled study comprising 64 patients was performed for 2 weeks. The active group received metered-dose inhaler chlorofluorocarbon-beclomethasone (1,500 microg/d), and the placebo group received identical-appearing placebo inhalers. All the participants completed a respiratory questionnaire and underwent bronchoprovocation testing (BPT) with methacholine and allergy skin testing. The primary outcome measure was a decrease in daily cough scores (symptom diary and visual analog scale) during the 2-week treatment period.

RESULTS

The active group comprised 44 patients and the placebo group 20 patients. Cough duration averaged 20 weeks. At the end of treatment 82% of the active group and 15% of the placebo group had complete resolution of cough. In the active group 22 patients (50%) had positive BPT results, and in the placebo group 10 patients (50%) had positive results. There was no correlation between treatment response and responses on the respiratory questionnaire, allergy skin testing, or BPT.

CONCLUSION

Therapy with high-dose inhaled beclomethasone provided an excellent response in a subgroup of patients with chronic cough that did not correlate with atopy or airway hyperresponsiveness.

Oxygen desaturation during a 4-minute step test: predicting survival in idiopathic pulmonary fibrosis

BACKGROUND AND AIM

PaO2 during exertion is a significant predictor of IPF survival. The aim of study was to assess oxygen desaturation for predicting survival in IPF patients at the end of a 4-minute step test.

METHODS

A longitudinal study was done in 59 patients with IPF from February 1998 to January 2005. Upon initial examination, lung function testing was performed, as were 4-minute step tests, in which patients stepped up and down on a 20-cm single step at a self-paced rate. In the final minute, oxygen saturation by pulse oximetry (SpO2) was measured.

RESULTS

Median survival was 58 months. SpO2 at rest and during stepping, dyspnea score, as well as FVC% and DLCO% were found to be significant predictors of mortality. Desaturation to 89% or less,correlated with a hazard ratio of 2.39 for IPF mortality (95% CI, 1.16-3.63; p < 0.0001). In patients with such desaturation, four-year survival was 39%, compared to 96% in those with no desaturation. In a multivariate Cox analysis, only SpO2 during stepping remained significant (p < 0.0001). A DLco < 45% of predicted (n=40 patients) correlated with a hazard ratio of 2.23 for mortality (95% CI, 0.73-3.71; p < 0.0001). When the analysis was repeated including DLco, SpO2 and DLco remained significant (p < 0.05).

CONCLUSION

Desaturation to 89% or less in a 4-min step test is a strong predictor of mortality in IPF patients.

[Asbestos-related diseases]

This chapter presents a bibliographic review of asbestos-related diseases. The latest diagnostic, radiological, computed tomography and lung function aspects of benign pleural disease, asbestosis, occupational lung cancer and mesothelioma are discussed.

Clinical, anthropometric and upper airway anatomic characteristics of obese patients with obstructive sleep apnea syndrome

BACKGROUND

Obese subjects are at increased risk of developing obstructive sleep apnea syndrome (OSAS). However, the individual role of local (i.e., upper airway-related) and general (clinical and whole-body anthropometric) characteristics in determining OSAS in obese patients is still controversial.

OBJECTIVES

To contrast the clinical, anthropometric and upper airway anatomical features of obese subjects presenting or not presenting with OSAS.

METHODS

Thirty-seven obese (BMI > or =30 kg/m(2)) males with OSAS and 14 age- and gender-matched obese controls underwent clinical and anthropometric (BMI, waist-to-hip ratio and neck circumference) evaluation. In a subgroup of subjects (18 and 11 subjects, respectively), magnetic resonance imaging (MRI) during wakefulness was used to study the upper airway anatomy.

RESULTS

OSAS patients showed significantly higher BMI, waist-to-hip ratio and neck circumference as compared to controls (p < 0.05). They also referred to nonrepairing sleep, impaired attention, and previous car accidents more frequently (p < 0.05). The transversal diameter of the airways (TDAW) at the retroglossal level by MRI was found to be an independent predictor of the presence and severity of OSAS (p < 0.05). Parapharyngeal fat increase, however, was not related to OSAS. A TDAW >12 mm was especially useful to rule out severe OSAS (apnea-hypopnea index >30, negative predictive value = 88.9%, likelihood ratio for a negative test result = 0.19).

CONCLUSIONS

MRI of the upper airway can be used in association with clinical and anthropometric data to identify obese males at increased risk of OSAS.

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.

A prospective longitudinal study of clinical characteristics, laboratory findings, diagnostic spectrum and outcomes of specific therapy in adult patients with chronic cough in a general respiratory clinic

Chronic cough with established diagnostic protocols has been well described in secondary and tertiary centres. Little information is available about adult patients to a general respiratory clinic where no such protocols exist. The objective of this study is to determine clinical characteristics, laboratory findings, diagnostic spectrum and outcomes of specific therapy in adult patients with chronic cough in a general respiratory clinic. In this prospective, longitudinal, descriptive study for patients with chronic cough defined as more than 8 weeks, we studied, according to a questionnaire, chest radiography, spirometry and reversibility, methacholine challenge and other measures. Treatment was prescribed on the basis of diagnosis informed by investigation results.We evaluated 147 patients (102 females) of a mean age of 48 years and complaining of cough an average of 24 weeks. On the basis of a successful response to treatment, the causes of cough were determined in 92% and the frequencies were asthma in 39%, COPD in 11%, chronic upper airway cough syndrome (CUACS) in 9%, gastro-oesophageal reflux disease (GERD) in 9% and no diagnosis in 8%. Cough was due to one condition in 82%. Our treatment success rate was 92%. The most frequent causes of chronic cough (asthma, COPD, CUACS and GERD) could be determined in a general respiratory clinic with a sequential approach. The frequencies are different from those in a tertiary cough clinic, but outcome of specific therapy is successful in our patients.

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.

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.

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.

Identification of rounded atelectasis in workers exposed to asbestos by contrast helical computed tomography

Rounded atelectasis (RA) is a benign and unusual form of subpleural lung collapse that has been described mostly in asbestos-exposed workers. This form of atelectasis manifests as a lung nodule and can be confused with bronchogenic carcinoma upon conventional radiologic examination. The objective of the present study was to evaluate the variation in contrast uptake in computed tomography for the identification of asbestos-related RA in Brazil. Between January 1998 and December 2000, high-resolution computed tomography (HRCT) was performed in 1658 asbestos-exposed workers. The diagnosis was made in nine patients based on a history of prior asbestos exposure, the presence of characteristic (HRCT) findings and lesions unchanged in size over 2 years or more. In three of them the diagnosis was confirmed during surgery. The dynamic contrast enhancement study was modified to evaluate nodules and pulmonary masses. All nine patients with RA received iodide contrast according to weight. The average enhancement after iodide contrast was infused, reported as Hounsfield units (HU), increased from 62.5+/-9.7 to 125.4+/-20.7 (P < 0.05), with a mean enhancement of 62.5+/-19.7 (range 40 to 89) and with a uniform dense opacification. In conclusion, in this study all patients with RA showed contrast enhancement with uniform dense opacification. The main clinical implication of this finding is that this procedure does not permit differentiation between RA and malignant pulmonary neoplasm.

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.

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.

The variability of the apnoea-hypopnoea index

This study was designed to evaluate the variability of the apnoea-hypopnoea index (AHI) in 20 patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS) and to determine possible relationships of this variability with other polysomnographic parameters. The subjects were recorded on four consecutive nights. The mean AHI values were not significantly altered throughout the four recording nights (P=0.67). The intraclass correlation coefficient of the AHI on the four nights was 0.92. However, the Bland and Altman plot showed that, individually, the AHI presented an important variability, which was not related to its initial value. In regard to the OSAHS severity, 50% of the patients changed the classification from the first to the subsequent nights. Thirteen of the 20 patients (65%) presented a variation in the AHI value equal or higher than 10 events h(-1). When we evaluated the AHI mean values for a specific body position and sleep stage, no difference was observed among the nights. In both supine and lateral-ventral decubitus, higher AHI was observed during Stages 1 and 2 than the other stages. Additionally, the AHI during Stages 1 and 2 and REM sleep was higher on the supine than on the lateral-ventral decubitus. The AHI in OSAHS patients presented a good correlation among the four recording nights; however, a significant individual variability should be considered, especially when AHI is applied in OSAHS classification or as a criterion of therapeutic success.

Acute effect of nasal continuous positive air pressure on the ventilatory control of patients with obstructive sleep apnea

BACKGROUND

Sleep fragmentation can decrease the awake ventilatory control. Since patients with obstructive sleep apnea (OSA) patients exhibit sleep fragmentation linked to respiratory events, their ventilatory control could be impaired. However, most of these patients are also obese, which could conversely increase the ventilatory control. The effect of nasal continuous positive airway pressure (CPAP) on the awake ventilatory control in normocapnic OSA patients is unclear.

OBJECTIVES

To study the acute effect of nasal CPAP on the awake ventilatory control in normocapnic OSA patients.

METHODS

12 normocapnic OSA patients, with an apnea/hypopnea index (AHI) >15 with moderate obesity (body mass index: 33.5 kg/m2) and normal pulmonary function tests were submitted to two polysomnography studies (diagnostic and for CPAP titration). Before and after 3 consecutive nights of nasal CPAP we analyzed the hypersomnia score and the ventilatory and the mouth occlusion pressure (P.1) responses at rest (breathing room air and a mixture of 8% CO2 + 40% O2).

RESULTS

The respiratory drive of OSA patients as evaluated by P.1 was in the range of the controls of our laboratory. After nasal CPAP, a significant decrease in AHI (mean: 51.9-9.4/h) and arousal (mean: 88.7-43/h) occurred, as well as improvement in nocturnal oxyhemoglobin. There was a marginal increase in DeltaV(E)/DeltaP(ET)CO2 (mean: 1.41-1.87 liters/min/ mm Hg, p = 0.09) and a significant rise in P.1/DeltaP(ET)CO2 (mean: 0.29-0.43 cm H2O/mm Hg), a better indicator of ventilatory drive.

CONCLUSIONS

Normocapnic OSA patients increased their awake ventilatory drive response to a hypercapnic and hyperoxic mixture with the use of 3 consecutive nights of nasal CPAP.

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.