Journal of applied physiology
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Randomized Controlled Trial Clinical Trial
High-intensity interval training vs. moderate-intensity continuous exercise training in heart failure with preserved ejection fraction: a pilot study.
Heart failure with preserved ejection fraction (HFpEF) is a major cause of morbidity and mortality. Exercise training is an established adjuvant therapy in heart failure; however, the effects of high-intensity interval training (HIIT) in HFpEF are unknown. We compared the effects of HIIT vs. moderate-intensity aerobic continuous training (MI-ACT) on peak oxygen uptake (V̇o₂peak), left ventricular diastolic dysfunction, and endothelial function in patients with HFpEF. ⋯ A trend for reduced left atrial volume index was observed following HIIT compared with MI-ACT (-3.3 ± 6.6 vs. +5.8 ± 10.7 ml/m(2); P = 0.06). In HFpEF patients 4 wk of HIIT significantly improved V̇o₂peak and left ventricular diastolic dysfunction. HIIT may provide a more robust stimulus than MI-ACT for early exercise training adaptations in HFpEF.
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Sex and age affect the pulmonary circulation. Whether there may be racial differences in pulmonary vascular function is unknown. Thirty white European Caucasian subjects (15 women) and age and body-size matched 30 black sub-Saharan African subjects (15 women) underwent a cardiopulmonary exercise test and exercise stress echocardiography with measurements of pulmonary artery pressure (PAP) and cardiac output (CO). ⋯ In men only, the slopes of mPAP-CO relationships were inversely correlated to V̇o2max (P < 0.01). Thus the pulmonary circulation is intrinsically less distensible in black sub-Saharan African men compared with white Caucasian Europeans men, and this is associated with a lower exercise capacity. This study did not identify racial differences in pulmonary vascular function in women.
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We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation in eight anaesthetized, paralyzed, and mechanically ventilated New Zealand White rabbits. Regional specific ventilation (sV̇) was measured by K-edge subtraction synchrotron computed tomography during xenon washin. Lung regions were classified as poorly aerated (PA), normally aerated (NA), or hyperinflated (HI) based on regional density. ⋯ Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. continuous positive airway pressure and early "rescue" surfactant therapy in very immature infants.
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Alveolar overdistension and mechanical stresses generated by repetitive opening and closing of small airways and alveoli have been widely recognized as two primary mechanistic factors that may contribute to the development of ventilator-induced lung injury. A long-duration exposure of alveolar epithelial cells to even small, shear stresses could lead to the changes in cytoskeleton and the production of inflammatory mediators. In this paper, we have made an attempt to estimate in situ the magnitudes of mechanical stresses exerted on the alveolar walls during repetitive alveolar reopening by using a tape-peeling model of McEwan and Taylor (35). ⋯ In addition, we have conceived of a geometrical model of alveolar opening to make a prediction of the positive end-expiratory pressure (PEEP) required to splint open a collapsed alveolus, which as shown by our results, covers a wide range of pressures, from several centimeters to dozens of centimeters of water, strongly depending on the underlying pulmonary conditions. The establishment of adequate regional ventilation-to-perfusion ratios may prevent recruited alveoli from reabsorption atelectasis and accordingly, reduce the required levels of PEEP. The present study and several recent animal experiments likewise suggest that a lung-protective ventilation strategy should not only include small tidal volume and plateau pressure limitations but also consider such cofactors as ventilation frequency and inflation rate.
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Patients with chronic obstructive pulmonary disease (COPD) exhibit increases in lung volume due to expiratory airflow limitation. Increases in lung volumes may affect upper airway patency and compensatory responses to inspiratory flow limitation (IFL) during sleep. We hypothesized that COPD patients have less collapsible airways inversely proportional to their lung volumes, and that the presence of expiratory airflow limitation limits duty cycle responses to defend ventilation in the presence of IFL. ⋯ In response to IFL, inspiratory duty cycle increased more (P = 0.03) in COPD patients (0.40 to 0.54) than in controls (0.41 to 0.51) and led to a marked reduction in expiratory time from 2.5 to 1.5 s (P < 0.01). COPD patients have a less collapsible airway and a greater, not reduced, compensatory timing response during upper airway obstruction. While these timing responses may reduce hypoventilation, it may also increase the risk for developing dynamic hyperinflation due to a marked reduction in expiratory time.