Weight loss associated with exercise training restores ventilatory efficiency in obese children

The purpose of this study was to test the hypothesis that in obese children: 1) Ventilatory efficiency (VentE) is decreased during graded exercise; and 2) Weight loss through diet alone (D) improves VentE, and 3) diet associated with exercise training (DET) leads to greater improvement in VentE than by D. Thirty-eight obese children (10 +/- 0.2 years; BMI > 95(th) percentile) were randomly divided into two Study groups: D (n=17; BMI = 30 +/- 1 kg/m(2)) and DET (n = 21; 28 +/- 1 kg/m(2)). Ten lean children were included in a control group (10 +/- 0.3 years; 17 +/- 0.5 kg/m(2)). All children performed maximal treadmill testing with respiratory gas analysis (breath-by-breath) to determine the ventilatory anaerobic threshold (VAT) and peak oxygen consumption (VO(2) peak). VentE was determined by the VE/VCO(2) method at VAT. Obese children showed lower VO(2) peak and lower VentE than controls (p < 0.05). After interventions, all obese children reduced body weight (p < 0.05). D group did not improve in terms of VO(2) peak or VentE (p > 0.05). In contrast, the DET group showed increased VO(2) peak (p = 0.01) and improved VentE(Delta VE/VCO(2) = -6.1 +/- 0.9; p = 0.01). VentE is decreased in obese children, where weight loss by means of DET, but not D alone, improves VentE and cardiorespiratory fitness during graded exercise.

Effects of continuous vs interval exercise training on oxygen uptake efficiency slope in patients with coronary artery disease

The oxygen uptake efficiency slope (OUES) is a submaximal index incorporating cardiovascular, peripheral, and pulmonary factors that determine the ventilatory response to exercise. The purpose of this study was to evaluate the effects of continuous exercise training and interval exercise training on the OUES in patients with coronary artery disease. Thirty-five patients (59.3±1.8 years old; 28 men, 7 women) with coronary artery disease were randomly divided into two groups: continuous exercise training (n=18) and interval exercise training (n=17). All patients performed graded exercise tests with respiratory gas analysis before and 3 months after the exercise-training program to determine ventilatory anaerobic threshold (VAT), respiratory compensation point, and peak oxygen consumption (peak VO2). The OUES was assessed based on data from the second minute of exercise until exhaustion by calculating the slope of the linear relation between oxygen uptake and the logarithm of total ventilation. After the interventions, both groups showed increased aerobic fitness (P<0.05). In addition, both the continuous exercise and interval exercise training groups demonstrated an increase in OUES (P<0.05). Significant associations were observed in both groups: 1) continuous exercise training (OUES and peak VO2 r=0.57; OUES and VO2 VAT r=0.57); 2) interval exercise training (OUES and peak VO2 r=0.80; OUES and VO2 VAT r=0.67). Continuous and interval exercise training resulted in a similar increase in OUES among patients with coronary artery disease. These findings suggest that improvements in OUES among CAD patients after aerobic exercise training may be dependent on peripheral and central mechanisms.

STRUCTURAL AND FUNCTIONAL CORRELATES OF EXERCISE VENTILATORY INEFFICIENCY IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE PATIENTS WITH MILD-TO-MODERATE SPIROMETRIC ABNORMALITIES

Background: Individuals with chronic obstructive pulmonary disease (COPD) have higher than normal ventilatory equivalents for carbon dioxide (VE/VCO2) during exercise. There is growing evidence that emphysema on thoracic computed tomography (CT) scans is associated with poor exercise capacity in COPD patients with only mild-to-moderate airflow obstruction. We hypothesized that emphysema is an underlying cause of microvascular dysfunction and ventilatory inefficiency, which in turn contributes to reduced exercise capacity. We expected ventilatory inefficiency to be associated with a) the extent of emphysema; b) lower diffusing capacity for carbon monoxide; c) a reduced pulmonary blood flow response to exercise; and d) reduced exercise capacity. Methods: In a cross-sectional study, 19 subjects with mild-to-moderate COPD (mean ± SD FEV1= 82 ± 13% predicted, 12 GOLD grade 1) and 26 age-, sex-, and activity-matched controls underwent a ramp-incremental symptom-limited exercise test on a cycle ergometer. Ventilatory inefficiency was assessed by the minimum VE/VCO2 value (nadir). A subset of subjects also completed repeated constant work rate exercise bouts with non-invasive measurements of pulmonary blood flow. Emphysema was quantified as the percentage of attenuation areas below -950 Housefield Units on CT scans. An electronic scoresheet was used to keep track of emphysema sub-types. Results: COPD subjects typically had centrilobular emphysema (76.8 ± 10.1% of total emphysema) in the upper lobes (upper/lower lobe ratio= 0.82 ± 0.04). They had lower peak oxygen uptake (VO2), higher VE/VCO2 nadir and greater dyspnea scores than controls (p<0.05). Lower peak O2 and worse dyspnea were found in COPD subjects with VE/VCO2 nadirs ≥ 30. COPD subjects had blunted increases in pulmonary blood flow from rest to iso-VO2 exercise (p<0.05). Higher VE/VCO2 nadir in COPD subjects correlated with emphysema severity (r= 0.63), which in turn correlated with reduced lung diffusing capacity (r= -0.72) and blunted changes in pulmonary blood flow from rest to exercise (r= -0.69) (p<0.01). Conclusions: Ventilation “wasted” in emphysematous areas is associated with reduced exercise ventilatory efficiency in mild-to-moderate COPD. Exercise ventilatory inefficiency links structure (emphysema) and function (gas transfer) to a key clinical outcome (reduced exercise capacity) in COPD patients with modest spirometric abnormalities.

Valor Prognóstico da Normalização da Resposta Ventilatória ao Exercício para o Consumo Máximo de Oxigénio na Insuficiência Cardíaca

Cardiopulmonary exercise testing (CPET) is an objective method for assessment of functional capacity and for prognostic stratification of patients with chronic heart failure (CHF). In this study, we analyzed the prognostic value of a recently described CPET-derived parameter, the minute ventilation to carbon dioxide production slope normalized for peak oxygen consumption (VE/VCO2 slope/pVO2). METHODS: We prospectively studied 157 patients with stable CHF and dilated cardiomyopathy who performed maximal CPET using the modified Bruce protocol. The prognostic value of VE/VCO2 slope/pVO2 was determined and compared with traditional CPET parameters. RESULTS: During follow-up 37 patients died and 12 were transplanted. Mean follow-up in surviving patients was 29.7 months (12-36). Cox multivariate analysis revealed that VE/VCO2 slope/pVO2 had the greatest prognostic power of all the parameters studied. A VE/VCO2 slope/pVO2 of > or = 2.2 signaled cases at higher risk. CONCLUSION: Normalization of the ventilatory response to exercise for peak oxygen consumption appears to increase the prognostic value of CPET in patients with CHF.

Fluido Torácico Total. Um Possível Determinante da Eficácia Ventilatória em Doentes com Insuficiência Cardíaca

A eficácia ventilatória, avaliada por prova de esforço cardiorrespiratória (PECR), tem um importante valor prognóstico em doentes (dts) com insuficiência cardíaca crónica (ICC) por disfunção sistólica ventricular esquerda (DSVE). Os seus determinantes mantêm-se, contudo, controversos. Objectivo: Investigar a eventual correlação entre parâmetros de eficácia ventilatória, obtidos por PECR, e o valor do fluido torácico total (FTT), avaliado por bioimpedância eléctrica torácica (BET), em dts com ICC por DSVE. Métodos: Estudámos 120 dts com ICC por DSVE, referenciados ao nosso laboratório para PECR — 76% do sexo masculino, idade 52,1 ± 12,1 anos, 37% de etiologia isquémica, fracção de ejecção ventricular esquerda 27,6 ± 7,9%, 83% em ritmo sinusal, 96% sob iECA e/ou ARAII, 79% sob beta-bloqueante e 20% tratados com dispositivo de ressincronização cardíaca. Os dts efectuaram PECR, em tapete rolante, protocolo de Bruce modificado,sendo considerados para análise, como parâmetro de capacidade funcional, o consumo de oxigénio de pico (VO2p) e, como parâmetros de eficácia ventilatória, o declive (d) da relação entre ventilação minuto(VE) e produção de CO2 (VCO2) e o valor do VE/VCO2 no limiar anaeróbico (LANA). Os estudos por BET, média de 20 minutos de aquisição, foram efectuados após 15 minutos de repouso, em posição supina, imediatamente antes das PECR, sendo analisado o valor do FTT. Resultados: O valor do FTT variou entre 20,6 e 45,8 kOhm−1, média = 32,2, DP = 5,7, mediana = 32,7, o de VO2p entre 8,9 e 40,6 ml/kg/min, média = 21,0, DP = 6,2, mediana = 20,2, o do dVE/VCO2 entre 19,8 e 60,7, média = 30,7, DP = 7,9, mediana = 29,1 e o do VE/VCO2 no LANA entre 21 e 62,média = 33,1, DP = 7,5, mediana = 31,5. Por regressão linear, o FTT não se correlacionou com o VO2p — r = 0,05, p = 0,58 — mas apresentou correlação com os parâmetros de eficácia ventilatória analisados: r = 0,20, p = 0,032, r² = 0,04 com dVE/VCO2 e r = 0,25, p = 0,009, r² = 0.06 com VE/VCO2 no LANA. Conclusão: O FTT correlaciona-se com os parâmetros de eficácia ventilatória, avaliados por PECR, em dts com ICC por DSVE, o que indica que poderá ser um dos seus determinantes.

Effect of continuous and interval exercise training on the PETCO2 response during a graded exercise test in patients with coronary artery disease

OBJECTIVE: The purpose of this study was to evaluate the following: 1) the effects of continuous exercise training and interval exercise training on the end-tidal carbon dioxide pressure (PETCO2) response during a graded exercise test in patients with coronary artery disease; and 2) the effects of exercise training modalities on the association between PETCO2 at the ventilatory anaerobic threshold (VAT) and indicators of ventilatory efficiency and cardiorespiratory fitness in patients with coronary artery disease. METHODS: Thirty-seven patients (59.7 +/- 1.7 years) with coronary artery disease were randomly divided into two groups: continuous exercise training (n = 20) and interval exercise training (n = 17). All patients performed a graded exercise test with respiratory gas analysis before and after three months of the exercise training program to determine the VAT, respiratory compensation point (RCP) and peak oxygen consumption. RESULTS: After the interventions, both groups exhibited increased cardiorespiratory fitness. Indeed, the continuous exercise and interval exercise training groups demonstrated increases in both ventilatory efficiency and PETCO2 values at VAT, RCP, and peak of exercise. Significant associations were observed in both groups: 1) continuous exercise training (PETCO(2)VAT and cardiorespiratory fitness r = 0.49; PETCO(2)VAT and ventilatory efficiency r = -0.80) and 2) interval exercise training (PETCO(2)VAT and cardiorespiratory fitness r = 0.39; PETCO(2)VAT and ventilatory efficiency r = -0.45). CONCLUSIONS: Both exercise training modalities showed similar increases in PETCO2 levels during a graded exercise test in patients with coronary artery disease, which may be associated with an improvement in ventilatory efficiency and cardiorespiratory fitness.

Inspiratory Muscle Training Reduces Sympathetic Nervous Activity and Improves Inspiratory Muscle Weakness and Quality of Life in Patients With Chronic Heart Failure A CLINICAL TRIAL

PURPOSE: To evaluate the effect of inspiratory muscle training (IMT) on cardiac autonomic modulation and on peripheral nerve sympathetic activity in patients with chronic heart failure (CHF). METHODS: Functional capacity, low-frequency (LF) and high-frequency (HF) components of heart rate variability, muscle sympathetic nerve activity inferred by microneurography, and quality of life were determined in 27 patients with CHF who had been sequentially allocated to 1 of 2 groups: (1) control group (with no intervention) and (2) IMT group. Inspiratory muscle training consisted of respiratory exercises, with inspiratory threshold loading of seven 30-minute sessions per week for a period of 12 weeks, with a monthly increase of 30% in maximal inspiratory pressure (PImax) at rest. Multivariate analysis was applied to detect differences between baseline and followup period. RESULTS: Inspiratory muscle training significantly increased PImax (59.2 +/- 4.9 vs 87.5 +/- 6.5 cmH(2)O, P = .001) and peak oxygen uptake (14.4 +/- 0.7 vs 18.9 +/- 0.8 mL.kg(-1).min(-1), P = .002); decreased the peak ventilation (V. E) +/- carbon dioxide production (V-CO2) ratio (35.8 +/- 0.8 vs 32.5 +/- 0.4, P = .001) and the (V) over dotE +/-(V) over dotCO(2) slope (37.3 +/- 1.1 vs 31.3 +/- 1.1, P = .004); increased the HF component (49.3 +/- 4.1 vs 58.4 +/- 4.2 normalized units, P = .004) and decreased the LF component (50.7 +/- 4.1 vs 41.6 +/- 4.2 normalized units, P = .001) of heart rate variability; decreased muscle sympathetic nerve activity (37.1 +/- 3 vs 29.5 +/- 2.3 bursts per minute, P = .001); and improved quality of life. No significant changes were observed in the control group. CONCLUSION: Home-based IMT represents an important strategy to improve cardiac and peripheral autonomic controls, functional capacity, and quality of life in patients with CHF.

Exercise training reverses exertional oscillatory ventilation in heart failure patients

Exertional oscillatory ventilation (EOV) is an ominous prognostic sign in chronic heart failure (CHF), but little is known about the success of specific therapeutic interventions. Our aim was to study the impact of an exercise training on exercise capacity and cardiopulmonary adaptation in stable CHF patients with left ventricular systolic dysfunction and EOV. 96 stable CHF patients with EOV were included in a retrospective analysis (52 training versus 44 controls). EOV was defined as follows: 1) three or more oscillatory fluctuations in minute ventilation (V'(E)) during exercise; 2) regular oscillations; and 3) minimal average ventilation amplitude ≥5 L. EOV disappeared in 37 (71.2%) out of 52 patients after training, but only in one (2.3%) out of 44 without training (p<0.001). The decrease of EOV amplitude correlated with changes in end-tidal carbon dioxide tension (r= -0.60, p<0.001) at the respiratory compensation point and V'(E)/carbon dioxide production (V'(CO(2))) slope (r=0.50, p<0.001). Training significantly improved resting values of respiratory frequency (f(R)), V'(E), tidal volume (V(T)) and V'(E)/V'(CO(2)) ratio. During exercise, V'(E) and V(T) reached significantly higher values at the peak, while f(R) and V'(E)/V'(CO(2)) ratio were significantly lower at submaximal exercise. No change was noted in the control group. Exercise training leads to a significant decrease of EOV and improves ventilatory efficiency in patients with stable CHF.

Effects of inspiratory muscle training in patients with heart failure with preserved ejection fraction

BACKGROUND Heart failure with preserved ejection fraction (HFpEF) is remarkably common in elderly people with highly prevalent comorbid conditions. Despite its increasing in prevalence, there is no evidence-based effective therapy for HFpEF. We sought to evaluate whether inspiratory muscle training (IMT) improves exercise capacity, as well as left ventricular diastolic function, biomarker profile and quality of life (QoL) in patients with advanced HFpEF and nonreduced maximal inspiratory pressure (MIP). DESIGN AND METHODS A total of 26 patients with HFpEF (median (interquartile range) age, peak exercise oxygen uptake (peak VO2) and left ventricular ejection fraction of 73 years (66-76), 10 ml/min/kg (7.6-10.5) and 72% (65-77), respectively) were randomized to receive a 12-week programme of IMT plus standard care vs. standard care alone. The primary endpoint of the study was evaluated by positive changes in cardiopulmonary exercise parameters and distance walked in 6 minutes (6MWT). Secondary endpoints were changes in QoL, echocardiogram parameters of diastolic function, and prognostic biomarkers. RESULTS The IMT group improved significantly their MIP (p < 0.001), peak VO2 (p < 0.001), exercise oxygen uptake at anaerobic threshold (p = 0.001), ventilatory efficiency (p = 0.007), metabolic equivalents (p < 0,001), 6MWT (p < 0.001), and QoL (p = 0.037) as compared to the control group. No changes on diastolic function parameters or biomarkers levels were observed between both groups. CONCLUSIONS In HFpEF patients with low aerobic capacity and non-reduced MIP, IMT was associated with marked improvement in exercise capacity and QoL.

AltitudeOmics : impaired pulmonary gas exchange efficiency and blunted ventilatory acclimatization in humans with patent foramen ovale after 16 days at 5,260 m.

A patent foramen ovale (PFO), present in ∼40% of the general population, is a potential source of right-to-left shunt that can impair pulmonary gas exchange efficiency [i.e., increase the alveolar-to-arterial Po2 difference (A-aDO2)]. Prior studies investigating human acclimatization to high-altitude with A-aDO2 as a key parameter have not investigated differences between subjects with (PFO+) or without a PFO (PFO-). We hypothesized that in PFO+ subjects A-aDO2 would not improve (i.e., decrease) after acclimatization to high altitude compared with PFO- subjects. Twenty-one (11 PFO+) healthy sea-level residents were studied at rest and during cycle ergometer exercise at the highest iso-workload achieved at sea level (SL), after acute transport to 5,260 m (ALT1), and again at 5,260 m after 16 days of high-altitude acclimatization (ALT16). In contrast to PFO- subjects, PFO+ subjects had 1) no improvement in A-aDO2 at rest and during exercise at ALT16 compared with ALT1, 2) no significant increase in resting alveolar ventilation, or alveolar Po2, at ALT16 compared with ALT1, and consequently had 3) an increased arterial Pco2 and decreased arterial Po2 and arterial O2 saturation at rest at ALT16. Furthermore, PFO+ subjects had an increased incidence of acute mountain sickness (AMS) at ALT1 concomitant with significantly lower peripheral O2 saturation (SpO2). These data suggest that PFO+ subjects have increased susceptibility to AMS when not taking prophylactic treatments, that right-to-left shunt through a PFO impairs pulmonary gas exchange efficiency even after acclimatization to high altitude, and that PFO+ subjects have blunted ventilatory acclimatization after 16 days at altitude compared with PFO- subjects.

Circulatory and Ventilatory Power: Characterization in Patients with Coronary Artery Disease

Background:Circulatory power (CP) and ventilatory power (VP) are indices that have been used for the clinical evaluation of patients with heart failure; however, no study has evaluated these indices in patients with coronary artery disease (CAD) without heart failure.Objective:To characterize both indices in patients with CAD compared with healthy controls.Methods:Eighty-seven men [CAD group = 42 subjects and healthy control group (CG) = 45 subjects] aged 40–65 years were included. Cardiopulmonary exercise testing was performed on a treadmill and the following parameters were measured: 1) peak oxygen consumption (VO2), 2) peak heart rate (HR), 3) peak blood pressure (BP), 4) peak rate-pressure product (peak systolic HR x peak BP), 5) peak oxygen pulse (peak VO2/peak HR), 6) oxygen uptake efficiency (OUES), 7) carbon dioxide production efficiency (minute ventilation/carbon dioxide production slope), 8) CP (peak VO2 x peak systolic BP) and 9) VP (peak systolic BP/carbon dioxide production efficiency).Results:The CAD group had significantly lower values for peak VO2 (p < 0.001), peak HR (p < 0.001), peak systolic BP (p < 0.001), peak rate-pressure product (p < 0.001), peak oxygen pulse (p = 0.008), OUES (p < 0.001), CP (p < 0.001), and VP (p < 0.001) and significantly higher values for peak diastolic BP (p = 0.004) and carbon dioxide production efficiency (p < 0.001) compared with CG. Stepwise regression analysis showed that CP was influenced by group (R2 = 0.44, p < 0.001) and VP was influenced by both group and number of vessels with stenosis after treatment (interaction effects: R2 = 0.46, p < 0.001).Conclusion:The indices CP and VP were lower in men with CAD than healthy controls.

Physiologic response to changing positive end-expiratory pressure during neurally adjusted ventilatory assist in sedated, critically ill adults

Neurally adjusted ventilatory assist (NAVA) delivers airway pressure (Paw) in proportion to neural inspiratory drive as reflected by electrical activity of the diaphragm (EAdi). Changing positive end-expiratory pressure (PEEP) impacts respiratory muscle load and function and, hence, EAdi. We aimed to evaluate how PEEP affects the breathing pattern and neuroventilatory efficiency during NAVA.

Ventilatory response to nitrogen multiple-breath washout in infants

BACKGROUND Nitrogen multiple-breath washout (N2 MBW) using 100% oxygen (O2 ) has regained interest to assess efficiency of tracer gas clearance in, for example, children with Cystic Fibrosis (CF). However, the influence of hyperoxia on the infants' respiratory control is unclear. We assessed safety and impact on breathing pattern from hyperoxia, and if exposure to 40% O2 first induces tolerance to subsequent 100% O2 for N2 MBW. METHODS We prospectively enrolled 39 infants aged 3-57 weeks: 15 infants with CF (8 sedated for testing) and 24 healthy controls. Infants were consecutively allocated to the protocols comprising of 100% O2 or 40/100% O2 administered for 30 breaths. Lung function was measured using an ultrasonic flowmeter setup. Primary outcome was tidal volume (VT ). RESULTS None of the infants experienced apnea, desaturation, or bradycardia. Both protocols initially induced hypoventilation. VT temporarily declined in 33/39 infants across 10-25 breaths. Hypoventilation occurred independent of age, disease, and sedation. In the new 40/100% O2 protocol, VT returned to baseline during 40% O2 and remained stable during 100% O2 exposure. End-tidal carbon dioxide monitored online did not change. CONCLUSION The classical N2 MBW protocol with 100% O2 may change breathing patterns of the infants. The new protocol with 40% O2 induces hyperoxia-tolerance and does not lead to changes in breathing patterns during later N2 washout using 100% O2 . Both protocols are safe, the new protocol seems an attractive option for N2 MBW in infants. Pediatr Pulmonol. © 2013 Wiley Periodicals, Inc.

Intermittent Fasting Induces Hypothalamic Modifications Resulting In Low Feeding Efficiency, Low Body Mass And Overeating.

Intermittent fasting (IF) is an often-used intervention to decrease body mass. In male Sprague-Dawley rats, 24 hour cycles of IF result in light caloric restriction, reduced body mass gain, and significant decreases in the efficiency of energy conversion. Here, we study the metabolic effects of IF in order to uncover mechanisms involved in this lower energy conversion efficiency. After 3 weeks, IF animals displayed overeating during fed periods and lower body mass, accompanied by alterations in energy-related tissue mass. The lower efficiency of energy use was not due to uncoupling of muscle mitochondria. Enhanced lipid oxidation was observed during fasting days, whereas fed days were accompanied by higher metabolic rates. Furthermore, an increased expression of orexigenic neurotransmitters AGRP and NPY in the hypothalamus of IF animals was found, even on feeding days, which could explain the overeating pattern. Together, these effects provide a mechanistic explanation for the lower efficiency of energy conversion observed. Overall, we find that IF promotes changes in hypothalamic function that explain differences in body mass and caloric intake.