Mechanisms and consequences of excess exercise ventilation in fibrosing interstitial lung disease

The causes and consequences of excess exercise ventilation (EEV) in patients with fibrosing interstitial lung disease (f-ILD) were explored. Twenty-eight adults with f-ILD and 13 controls performed an incremental cardiopulmonary exercise test. EEV was defined as ventilation-carbon dioxide output (⩒E-⩒CO2) slope ≥36 L/L. Patients showed lower pulmonary function and exercise capacity compared to controls. Lower DLCO was related to higher ⩒E-⩒CO2 slope in patients (P<0.05). 13/28 patients (46.4%) showed EEV, reporting higher dyspnea scores (P=0.033). Patients with EEV showed a higher dead space (VD)/tidal volume (VT) ratio while O2 saturation dropped to a greater extent during exercise compared to those without EEV. Higher breathing frequency and VT/inspiratory capacity ratio were observed during exercise in the former group (P<0.05). An exaggerated ventilatory response to exercise in patients with f-ILD is associated with a blunted decrease in the wasted ventilation in the physiological dead space and greater hypoxemia, prompting higher inspiratory constraints and breathlessness.

The pulmonary function laboratory in the investigation of dyspnea of unknown origin

Chronic dyspnea (i.e., dyspnea for at least 3 months) negatively impacts the health-related quality of life of ~10% of the general population. In a sizable fraction of these individuals, the underlying cause remains unclear after detailed clinical assessment, basic pulmonary function tests, and chest imaging, characterizing dyspnea of unknown origin (DUO). The “lung doctor” is frequently called to assess these patients for diagnostic clarification, an endeavor fraught with complexities in most circumstances.

Effects of Home-Based Electrical Stimulation on Plasma Cytokines Profile, Redox Biomarkers, and Metalloproteinases in the Heart Failure with Reduced Ejection Fraction: A Randomized Trial

Background: Low-frequency electrical stimulation (LFES) is an adjuvant method for heart failure (HF) patients with restrictions to start an exercise. However, the impact on molecular changes in circulating is unknown. We investigated the effects of 10 weeks of home-based LFES on plasma cytokines profile, redox biomarkers, metalloproteinases (MMPs) activity, and exercise performance in HF patients. Methods: Twenty-four HF patients (52.45 ± 9.15 years) with reduced ejection fraction (HFrEF) (EF < 40%), were randomly assigned to a home-based LFES or sham protocol. Plasma cytokines profile was assessed through interleukins, interferon-gamma, and tumor necrosis factor levels. Oxidative stress was evaluated through ferric reducing antioxidant power, thiobarbituric acid-reactive substances, and inducible nitric oxide synthase. The MMPs activity were analyzed by zymography. Cardiorespiratory capacity and muscle strength were evaluated by cardiopulmonary test and isokinetic. Results: LFES was able to increase the active-MMP2 activity post compared to pre-training (0.057 to 0.163, p = 0.0001), while it decreased the active-MMP9 (0.135 to 0.093, p = 0.02). However, it did not elicit changes in cytokines, redox biomarkers, or exercise performance (p > 0.05). Conclusion: LFES protocol is a promising intervention to modulate MMPs activity in HFrEF patients, although with limited functional effects. These preliminary responses may help the muscle to adapt to future mechanical demands dynamically.

Sleep quality and architecture in COPD: the relationship with lung function abnormalities

OBJECTIVE

Impaired respiratory mechanics and gas exchange may contribute to sleep disturbance in patients with COPD. We aimed to assess putative associations of different domains of lung function (airflow limitation, lung volumes, and gas exchange efficiency) with polysomnography (PSG)-derived parameters of sleep quality and architecture in COPD.

METHODS

We retrospectively assessed data from COPD 181 patients ≥ 40 years of age who underwent spirometry, plethysmography, and overnight PSG. Univariate and multivariate linear regression models predicted sleep efficiency (total sleep time/total recording time) and other PSG-derived parameters that reflect sleep quality.

RESULTS

The severity of COPD was widely distributed in the sample (post-bronchodilator FEV1 ranging from 25% to 128% of predicted): mild COPD (40.3%), moderate COPD (43.1%), and severe-very severe COPD (16.6%). PSG unveiled a high proportion of obstructive sleep apnea (64.1%) and significant nocturnal desaturation (mean pulse oximetry nadir = 82.2% ± 6.9%). After controlling for age, sex, BMI, apnea-hypopnea index, nocturnal desaturation, comorbidities, and psychotropic drug prescription, FEV1/FVC was associated with sleep efficiency (β = 25.366; R2 = 14%; p < 0.001), whereas DLCO predicted sleep onset latency (β = -0.314; R2 = 13%; p < 0.001) and rapid eye movement sleep time/total sleep time in % (β = 0.085; R2 = 15%; p = 0.001).

CONCLUSIONS

Pulmonary function variables reflecting severity of airflow and gas exchange impairment, adjusted for some potential confounders, were weakly related to PSG outcomes in COPD patients. The direct contribution of the pathophysiological hallmarks of COPD to objectively measured parameters of sleep quality seems to be less important than it was previously assumed.

Oxygen supplementation during exercise improves leg muscle fatigue in chronic fibrotic interstitial lung disease

BACKGROUND

Exercise-induced hypoxaemia is a hallmark of chronic fibrotic interstitial lung disease (f-ILD). It remains unclear whether patients' severe hypoxaemia may exaggerate locomotor muscle fatigue and, if so, to what extent oxygen (O₂) supplementation can ameliorate these abnormalities.

METHODS

Fifteen patients (12 males, 9 with idiopathic pulmonary fibrosis) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) while breathing medical air. Fifteen age-matched and sex-matched controls cycled up to patients' Tlim. Patients repeated the exercise test on supplemental O₂ (42%±7%) for the same duration. Near-infrared spectroscopy assessed vastus lateralis oxyhaemoglobin concentration ((HbO₂)). Pre-exercise to postexercise variation in twitch force (∆Tw) induced by femoral nerve magnetic stimulation quantified muscle fatigue.

RESULTS

Patients showed severe hypoxaemia (lowest O₂ saturation by pulse oximetry=80.0%±7.6%) which was associated with a blunted increase in muscle (HbO₂₎ during exercise vs controls (+1.3±0.3 µmol vs +4.4±0.4 µmol, respectively; p<0.001). Despite exercising at work rates ∼ one-third lower than controls (42±13 W vs 66±13 W), ∆Tw was greater in patients (∆Tw/external work performed by the leg muscles=-0.59±0.21 %/kJ vs -0.25±0.19 %/kJ; p<0.001). Reversal of exertional hypoxaemia with supplemental O₂ was associated with a significant increase in muscle (HbO₂₎, leading to a reduced decrease in ∆Tw in patients (-0.33±0.19 %/kJ; p<0.001 vs air). Supplemental O₂ significantly improved leg discomfort (p=0.005).

CONCLUSION

O₂ supplementation during exercise improves leg muscle oxygenation and fatigue in f-ILD. Lessening peripheral muscle fatigue to enhance exercise tolerance is a neglected therapeutic target that deserves clinical attention in this patient population.

Effects of high- and moderate-intensity exercise on central hemodynamic and oxygen uptake recovery kinetics in CHF-COPD overlap

The oxygen uptake (V˙O₂) kinetics during onset of and recovery from exercise have been shown to provide valuable parameters regarding functional capacity of both chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients. To investigate the influence of comorbidity of COPD in patients with CHF with reduced ejection fraction on recovery from submaximal exercise, 9 CHF-COPD male patients and 10 age-, gender-, and left ventricle ejection fraction (LVEF)-matched CHF patients underwent constant-load exercise tests (CLET) at moderate and high loads. The V˙O₂, heart rate (HR), and cardiac output (CO) recovery kinetics were determined for the monoexponential relationship between these variables and time. Within-group analysis showed that the recovery time constant of HR (P<0.05, d=1.19 for CHF and 0.85 for CHF-COPD) and CO (P<0.05, d=1.68 for CHF and 0.69 for CHF-COPD) and the mean response time (MRT) of CO (P<0.05, d=1.84 for CHF and 0.73 for CHF-COPD) were slower when moderate and high loads were compared. CHF-COPD patients showed smaller amplitude of CO recovery kinetics (P<0.05) for both moderate (d=2.15) and high (d=1.07) CLET. Although the recovery time constant and MRT means were greater in CHF-COPD, CHF and CHF-COPD groups were not differently affected by load (P>0.05 in group vs load analysis). The ventilatory efficiency was related to MRT of V˙O₂ during high CLET (r=0.71). Our results suggested that the combination of CHF and COPD may further impair the recovery kinetics compared to CHF alone.

Association of Oscillatory Ventilation during Cardiopulmonary Test to Clinical and Functional Variables of Chronic Heart Failure Patients

Objective

The aim of this study is to characterize the presence of exercise oscillatory ventilation (EOV) and to relate it with other cardiopulmonary exercise test (CET) responses and clinical variables.

Methods

Forty-six male patients (age: 53.1±13.6 years old; left ventricular ejection fraction [LVEF]: 30±8%) with heart failure were recruited to perform a maximal CET and to correlate the CET responses with clinical variables. The EOV was obtained according to Leite et al. criteria and VE/VCO₂ > 34 and peak VO₂ < 14 ml/kg/min were used to assess patients' severity.

Results

The EOV was observed in 16 of 24 patients who performed the CET, as well as VE/VCO₂ > 34 and peak VO₂ < 14 ml/kg/min in 14 and 10 patients, respectively. There was no difference in clinical and CET variables of the patients who presented EOV in CET when compared to non-EOV patients. Also, there was no difference in CET and clinical variables when comparing patients who presented EOV and had a VE/VCO₂ slope > 34 to patients who just had one of these responses either.

Conclusion

The present study showed that there was an incidence of patients with EOV and lower peak VO₂ and higher VE/VCO₂ slope values, but they showed no difference on other prognostic variables. As well, there was no influence of the presence of EOV on other parameters of CET in this population, suggesting that this variable may be an independent marker of worst prognosis in HF patients.

A practical approach to assess leg muscle oxygenation during ramp-incremental cycle ergometry in heart failure

Heart failure is characterized by the inability of the cardiovascular system to maintain oxygen (O₂) delivery (i.e., muscle blood flow in non-hypoxemic patients) to meet O₂ demands. The resulting increase in fractional O₂ extraction can be non-invasively tracked by deoxygenated hemoglobin concentration (deoxi-Hb) as measured by near-infrared spectroscopy (NIRS). We aimed to establish a simplified approach to extract deoxi-Hb-based indices of impaired muscle O₂ delivery during rapidly-incrementing exercise in heart failure. We continuously probed the right vastus lateralis muscle with continuous-wave NIRS during a ramp-incremental cardiopulmonary exercise test in 10 patients (left ventricular ejection fraction <35%) and 10 age-matched healthy males. Deoxi-Hb is reported as % of total response (onset to peak exercise) in relation to work rate. Patients showed lower maximum exercise capacity and O₂ uptake-work rate than controls (P<0.05). The deoxi-Hb response profile as a function of work rate was S-shaped in all subjects, i.e., it presented three distinct phases. Increased muscle deoxygenation in patients compared to controls was demonstrated by: i) a steeper mid-exercise deoxi-Hb-work rate slope (2.2±1.3 vs 1.0±0.3% peak/W, respectively; P<0.05), and ii) late-exercise increase in deoxi-Hb, which contrasted with stable or decreasing deoxi-Hb in all controls. Steeper deoxi-Hb-work rate slope was associated with lower peak work rate in patients (r=–0.73; P=0.01). This simplified approach to deoxi-Hb interpretation might prove useful in clinical settings to quantify impairments in O₂ delivery by NIRS during ramp-incremental exercise in individual heart failure patients.

Influence of heart failure on resting lung volumes in patients with COPD

Objective:

To evaluate the influence of chronic heart failure (CHF) on resting lung volumes in patients with COPD, i.e., inspiratory fraction-inspiratory capacity (IC)/TLC-and relative inspiratory reserve-[1 − (end-inspiratory lung volume/TLC)].

Methods:

This was a prospective study involving 56 patients with COPD-24 (23 males/1 female) with COPD+CHF and 32 (28 males/4 females) with COPD only-who, after careful clinical stabilization, underwent spirometry (with forced and slow maneuvers) and whole-body plethysmography.

Results:

Although FEV₁, as well as the FEV₁/FVC and FEV₁/slow vital capacity ratios, were higher in the COPD+CHF group than in the COPD group, all major "static" volumes-RV, functional residual capacity (FRC), and TLC-were lower in the former group (p < 0.05). There was a greater reduction in FRC than in RV, resulting in the expiratory reserve volume being lower in the COPD+CHF group than in the COPD group. There were relatively proportional reductions in FRC and TLC in the two groups; therefore, IC was also comparable. Consequently, the inspiratory fraction was higher in the COPD+CHF group than in the COPD group (0.42 ± 0.10 vs. 0.36 ± 0.10; p < 0.05). Although the tidal volume/IC ratio was higher in the COPD+CHF group, the relative inspiratory reserve was remarkably similar between the two groups (0.35 ± 0.09 vs. 0.44 ± 0.14; p < 0.05).

Conclusions:

Despite the restrictive effects of CHF, patients with COPD+CHF have relatively higher inspiratory limits (a greater inspiratory fraction). However, those patients use only a part of those limits, probably in order to avoid critical reductions in inspiratory reserve and increases in elastic recoil.

Microvascular oxygen extraction during maximal isometric contraction in patients with chronic obstructive pulmonary disease

Abstract Introduction: COPD presents decrease in oxidative metabolism with possible losses of cardiovascular adjustments, suggesting slow kinetics microvascular oxygen during intense exercise. Objective: To test the hypothesis that chronic obstructive pulmonary disease (COPD) patients have lower muscle performance in physical exercise not dependent on central factors, but also greater muscle oxygen extraction, regardless of muscle mass. Methods: Cross-sectional study with 11 COPD patients and nine healthy subjects, male, paired for age. Spirometry and body composition by DEXA were evaluated. Muscular performance was assessed by maximal voluntary isometric contraction (MVIC) in isokinetic dynamometer and muscle oxygen extraction by the NIRS technique. Student t-test and Pearson correlation were applied. A significance level of p<0.05 was adopted. Results: Patients had moderate to severe COPD (FEV1 = 44.5 ± 9.6% predicted; SpO2 = 94.6 ± 1.6%). Lean leg mass was 8.3 ± 0.9 vs. 8.9 ± 1.0 kg (p =0.033), when comparing COPD and control patients, respectively. The decreased muscle oxygen saturation corrected by muscle mass was 53.2% higher (p=0.044) in the COPD group in MVIC-1 and 149.6% higher (p=0.006) in the MVIC-2. Microvascular extraction rate of oxygen corrected by muscle mass and total work was found to be 114.5% higher (p=0.043) in the COPD group in MVIC-1 and 210.5% higher (p=0.015) in the MVIC-2. Conclusion: COPD patients have low muscle performance and high oxygen extraction per muscle mass unit and per unit of work. The high oxygen extraction suggests that quantitative and qualitative mechanisms can be determinants of muscle performance in patients with COPD.

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.

Relationship between linear and nonlinear dynamics of heart rate and impairment of lung function in COPD patients

BACKGROUND

In chronic obstructive pulmonary disease (COPD), functional and structural impairment of lung function can negatively impact heart rate variability (HRV); however, it is unknown if static lung volumes and lung diffusion capacity negatively impacts HRV responses. We investigated whether impairment of static lung volumes and lung diffusion capacity could be related to HRV indices in patients with moderate to severe COPD.

METHODS

Sixteen sedentary males with COPD were enrolled in this study. Resting blood gases, static lung volumes, and lung diffusion capacity for carbon monoxide (DLCO) were measured. The RR interval (RRi) was registered in the supine, standing, and seated positions (10 minutes each) and during 4 minutes of a respiratory sinus arrhythmia maneuver (M-RSA). Delta changes (Δsupine-standing and Δsupine-M-RSA) of the standard deviation of normal RRi, low frequency (LF, normalized units [nu]) and high frequency (HF [nu]), SD1, SD2, alpha1, alpha2, and approximate entropy (ApEn) indices were calculated.

RESULTS

HF, LF, SD1, SD2, and alpha1 deltas significantly correlated with forced expiratory volume in 1 second, DLCO, airway resistance, residual volume, inspiratory capacity/total lung capacity ratio, and residual volume/total lung capacity ratio. Significant and moderate associations were also observed between LF/HF ratio versus total gas volume (%), r=0.53; LF/HF ratio versus residual volume, %, r=0.52; and HF versus total gas volume (%), r=-0.53 (P<0.05). Linear regression analysis revealed that ΔRRi supine-M-RSA was independently related to DLCO (r=-0.77, r (2)=0.43, P<0.05).

CONCLUSION

Responses of HRV indices were more prominent during M-RSA in moderate to severe COPD. Moreover, greater lung function impairment was related to poorer heart rate dynamics. Finally, impaired lung diffusion capacity was related to an altered parasympathetic response in these patients.

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.

Can bronchodilators improve exercise tolerance in COPD patients without dynamic hyperinflation?

OBJECTIVE

To investigate the modulatory effects that dynamic hyperinflation (DH), defined as a reduction in inspiratory capacity (IC), has on exercise tolerance after bronchodilator in patients with COPD.

METHODS

An experimental, randomized study involving 30 COPD patients without severe hypoxemia. At baseline, the patients underwent clinical assessment, spirometry, and incremental cardiopulmonary exercise testing (CPET). On two subsequent visits, the patients were randomized to receive a combination of inhaled fenoterol/ipratropium or placebo. All patients then underwent spirometry and submaximal CPET at constant speed up to the limit of tolerance (Tlim). The patients who showed ΔIC(peak-rest) < 0 were considered to present with DH (DH+).

RESULTS

In this sample, 21 patients (70%) had DH. The DH+ patients had higher airflow obstruction and lower Tlim than did the patients without DH (DH-). Despite equivalent improvement in FEV1 after bronchodilator, the DH- group showed higher ΔIC(bronchodilator-placebo) at rest in relation to the DH+ group (p < 0.05). However, this was not found in relation to ΔIC at peak exercise between DH+ and DH- groups (0.19 ± 0.17 L vs. 0.17 ± 0.15 L, p > 0.05). In addition, both groups showed similar improvements in Tlim after bronchodilator (median [interquartile range]: 22% [3-60%] vs. 10% [3-53%]; p > 0.05).

CONCLUSIONS

Improvement in TLim was associated with an increase in IC at rest after bronchodilator in HD- patients with COPD. However, even without that improvement, COPD patients can present with greater exercise tolerance after bronchodilator provided that they develop DH during exercise.

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.

Comportamento da hiperinsuflação dinâmica em teste em esteira rolante em pacientes com DPOC moderada a grave

OBJETIVO: Caracterizar a presença, extensão e padrões de hiperinsuflação dinâmica (HD) durante teste em esteira rolante em pacientes com DPOC moderada a grave. Métodos: Estudo transversal com 30 pacientes não hipoxêmicos (VEF1= 43 ± 14% do previsto) submetidos a teste cardiopulmonar de exercício em esteira rolante em velocidade constante (70-80% da velocidade máxima) até o limite da tolerância (Tlim). Manobras seriadas de capacidade inspiratória (CI) foram utilizadas para avaliação da HD. RESULTADOS: Dos 30 pacientes estudados, 19 (63,3%) apresentaram HD (grupo HD+), que apresentaram maior comprometimento funcional em repouso do que os pacientes sem HD (grupo HD-). Nenhuma das variáveis obtidas relacionou-se com a tolerância ao exercício no grupo HD-, enquanto Tlim, CI e percepção de dispneia ao esforço foram significativamente correlacionados no grupo HD+ (p < 0,05). No grupo HD+, 7 e 12 pacientes, respectivamente, apresentaram padrão progressivo e estável de HD (ΔCI Tlim,2min = -0,28 ± 0,11 L e 0,04 ± 0,10 L; p < 0,01). Pacientes com padrão progressivo de HD apresentaram maior relação percepção de dispneia/Tlim e menor tolerância ao exercício do que aqueles com padrão estável (354 ± 118 s e 465 ± 178 s, respectivamente; p < 0,05). CONCLUSÕES: A HD não é um fenômeno universal durante a caminhada em pacientes com DPOC, mesmo que apresentem obstrução ao fluxo aéreo de graus moderado a acentuado. Nos pacientes que apresentaram HD, um padrão progressivo de HD teve maior repercussão na tolerância ao exercício do que um padrão estável de HD.

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.

Effects of aerobic training during hemodialysis on heart rate variability and left ventricular function in end-stage renal disease patients

INTRODUCTION

Decreased heart rate variability (HRV) in patients with end stage renal disease (ESRD) undergoing hemodialysis is predictive of cardiac death, especially due to sudden death.

OBJECTIVE

To evaluate the effects of aerobic training during hemodialysis on HRV and left ventricular function in ESRD patients.

METHODS

Twenty two patients were randomized into two groups: exercise (n = 11; 49.6 ± 10.6 years; 4 men) and control (n = 11; 43.5 ± 12.8; 4 men). Patients assigned to the exercise group were submitted to aerobic training, performed during the first two hours of hemodialysis, three times weekly, for 12 weeks. HRV and left ventricular function were assessed by 24 hours Holter monitoring and echocardiography, respectively.

RESULTS

After 12 weeks of protocol, no significant differences were observed in time and frequency domains measures of HRV in both groups. The ejection fraction improved non-significantly in exercise group (67.5 ± 12.6% vs. 70.4 ± 12%) and decreased non-significantly in control group (73.6 ± 8.4% vs. 71.4 ± 7.6%).

CONCLUSION

A 12-week aerobic training program performed during hemodialysis did not modify HRV and did not significantly improve the left ventricular function.

[Influence of current smoking on adherence and responses to pulmonary rehabilitation in patients with COPD]

OBJECTIVE

To investigate the modulating effects of current smoking on adherence and responses to pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In a prospective study, 18 ex-smokers and 23 current smokers (GOLD stages II-III) were enrolled in a 12-week multidisciplinary, supervised PR program. The patients were assessed clinically and as to subjective variables (dyspnea and health-related quality of life) and objective variables (body composition, pulmonary function and 6-min walking distance). The degree of nicotine dependence in current smokers was assessed by the Fagerström test. Program completion defined PR 'adherence'.

RESULTS

There was a significant association between current smoking and non-adherence to PR with 30.4% vs. 11.1% and odds ratio=2.9 (1.6-4.1; p<0.01). However, the current smokers who completed the program (n=16) had a similar absentee rate to the ex-smokers, as well as similar gains in the subjective (quality of life) and objective (walked distance) items. Additionally, there was a significant reduction in daily cigarette consumption and in the degree of nicotine dependence in current smokers (p<0.05).

CONCLUSIONS

Although current smoking is negatively related to PR adherence, COPD smokers who complete the PR can have similar gains in functionality and quality of life compared to ex-smokers. Moreover, PR may be related to decreased nicotine dependence, even without a formal smoking withdrawal program.

Segurança e eficácia do treinamento físico na insuficiência renal crônica

A doença renal crônica acarreta alterações em todos os sistemas corporais. Os pacientes cursam com marcada redução do condicionamento cardiorrespiratório, alterações musculares, reduzida performance física e pior qualidade de vida. A atividade física tem sido cada vez mais utilizada como forma de tratamento para essa população. Programas de treinamento físico aeróbio e/ou resistidos de moderada ou baixa intensidade no período interdialítico e durante a hemodiálise têm sido utilizados. Entretanto, os benefícios dessas intervenções no doente renal crônico, a escolha mais apropriada do tipo de treinamento e a segurança da aplicabilidade de atividades específicas não estão bem esclarecidos. Esta revisão tem como objetivo abordar os aspectos relacionados com o tipo de treinamento, período em que este é realizado, assim como os possíveis benefícios que o treinamento físico pode induzir nessa população.

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.