Journal of Applied Physiology
8750-7587
1522-1601
Mỹ
Cơ quản chủ quản: American Physiological Society , AMER PHYSIOLOGICAL SOC
Lĩnh vực:
Physiology (medical)PhysiologyMedicine (miscellaneous)Sports Science
Các bài báo tiêu biểu
Effect of CPAP on respiratory effort and dyspnea during exercise in severe COPD Recent work has demonstrated the ability of continuous positive airway pressure (CPAP) to relieve dyspnea during exercise in patients with severe chronic obstructive pulmonary disease (COPD). The present study examined the effects of CPAP (7.5-10 cmH2O) on the pattern of respiratory muscle activation and its relationship to dyspnea during constant work load submaximal bicycle exercise [20 +/- 4.8 (SE) W] in eight COPD patients (forced expiratory volume in 1 s = 25 +/- 3% predicted). Tidal volume, respiratory rate, minute ventilation, and end-expiratory lung volume increased with exercise as expected. There was no change in breathing pattern, end-expiratory lung volume, or pulmonary compliance and resistance with the addition of CPAP. CPAP reduced inspiratory muscle effort, as indicated by the pressure-time integral of transdiaphragmatic (integral of Pdi.dt) and esophageal pressure (integral of Pes.dt, P less than 0.01 and P less than 0.05, respectively). In contrast, the pressure-time integral of gastric pressure (integral of Pga.dt), used as an index of abdominal muscle recruitment during expiration, increased (P less than 0.01). Dyspnea improved with CPAP in five of the eight patients. The amelioration of dyspnea was directly related to reductions in integral of Pes.dt (P less than 0.001) but inversely related to increases in integral of Pga.dt (P less than 0.01). In conclusion, CPAP reduces inspiratory muscle effort during exercise in COPD patients. However, the expected improvement in dyspnea is not seen in all patients and may be explained by more marked increases in expiratory muscle effort in some individuals.
Tập 69 Số 1 - Trang 179-188 - 1990
Ozone-induced airway hyperresponsiveness and loss of neuronal M2 muscarinic receptor function The effect of acute ozone exposure on the function of efferent parasympathetic nerves, M3 muscarinic receptors on airway smooth muscle, and inhibitory M2 muscarinic receptors on the parasympathetic nerves was studied. Immediately after exposure to 2.0 ppm ozone for 4 h, guinea pigs became hyperresponsive to electrical stimulation of the vagus nerves. The normal airway response to intravenous cholinergic agonists at this time demonstrates normal M3 receptor function. M2 muscarinic receptors on the nerves, which normally inhibit release of acetylcholine, were dysfunctional after ozone exposure, as demonstrated by the failure of the muscarinic agonist pilocarpine to inhibit, and the failure of the M2 antagonist gallamine to potentiate, vagally mediated bronchoconstriction. Thus, loss of inhibitory M2 muscarinic receptor function after ozone exposure potentiates release of acetylcholine from the vagus nerves, increasing vagally mediated bronchoconstriction. By 14 days, postozone responses to vagal nerve stimulation were not different from those of air-exposed animals and the function of the neuronal M2 muscarinic receptor was normal, confirming that ozone-induced hyperresponsiveness is reversible.
Tập 76 Số 3 - Trang 1088-1097 - 1994
Total respiratory tract deposition of fine micrometer-sized particles in healthy adults: empirical equations for sex and breathing pattern Accurate dose estimation under various inhalation conditions is important for assessing both the potential health effects of pollutant particles and the therapeutic efficacy of medicinal aerosols. We measured total deposition fraction (TDF) of monodisperse micrometer-sized particles [particle diameter (Dp ) = 1, 3, and 5 μm in diameter] in healthy adults (8 men and 7 women) in a wide range of breathing patterns; tidal volumes (Vt) of 350–1500 ml and respiratory flow rates (Q̇) of 175–1,000 ml/s. The subject inhaled test aerosols for 10–20 breaths with each of the prescribed breathing patterns, and TDF was obtained by monitoring inhaled and exhaled aerosols breath by breath by a laser aerosol photometer. Results show that TDF varied from 0.12–0.25, 0.26–0.68, and 0.45–0.83 for Dp = 1, 3, and 5 μm, respectively, depending on the breathing pattern used. TDF was comparable between men and women for Dp = 1 μm but was greater in women than men for Dp = 3 and 5 μm for all breathing patterns used ( P < 0.05). TDF increased with an increase in Vt regardless of Dp and Q̇ used. At a fixed Vt TDF decreased with an increase in Q̇ for Dp = 1 and 3 μm but did not show any significant changes for Dp = 5 μm. The varying TDF values, however, could be consolidated by a single composite parameter (ω) consisting of Dp , Vt, and Q̇. The results indicate that unifying empirical formulas provide a convenient means of assessing deposition dose of particles under varying inhalation conditions.
Tập 101 Số 2 - Trang 401-412 - 2006
Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington’s disease Hausdorff, Jeffrey M., Susan L. Mitchell, Renée Firtion, C. K. Peng, Merit E. Cudkowicz, Jeanne Y. Wei, and Ary L. Goldberger. Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington’s disease. J. Appl. Physiol. 82(1): 262–269, 1997.—Fluctuations in the duration of the gait cycle (the stride interval) display fractal dynamics and long-range correlations in healthy young adults. We hypothesized that these stride-interval correlations would be altered by changes in neurological function associated with aging and certain disease states. To test this hypothesis, we compared the stride-interval time series of 1) healthy elderly subjects and young controls and of 2) subjects with Huntington’s disease and healthy controls. Using detrended fluctuation analysis, we computed α, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. The scaling exponent α was significantly lower in elderly subjects compared with young subjects (elderly: 0.68 ± 0.14; young: 0.87 ± 0.15; P < 0.003). The scaling exponent α was also smaller in the subjects with Huntington’s disease compared with disease-free controls (Huntington’s disease: 0.60 ± 0.24; controls: 0.88 ± 0.17; P < 0.005). Moreover, α was linearly related to degree of functional impairment in subjects with Huntington’s disease ( r = 0.78, P < 0.0005). These findings demonstrate that stride-interval fluctuations are more random (i.e., less correlated) in elderly subjects and in subjects with Huntington’s disease. Abnormal alterations in the fractal properties of gait dynamics are apparently associated with changes in central nervous system control.
Tập 82 Số 1 - Trang 262-269 - 1997
Oxidative protein damage is associated with poor grip strength among older women living in the community Grip strength, an indicator of muscle strength, has been shown to be a predictor of poor outcomes among older adults. Protein carbonylation, an indicator of oxidative damage to proteins, leads to cellular dysfunction and a decline in tissue function. Oxidative stress has been implicated in the pathogenesis of sarcopenia. The objective was to determine whether serum protein carbonyl concentrations are associated with grip strength in older women living in the community. A cross-sectional study was conducted in 672 women, aged 65 and older, from the Women's Health and Aging Study (WHAS) I, the one-third most disabled women residing in the community in Baltimore, MD. Protein carbonyl and grip strength were measured in each patient. In a multivariate analysis adjusting for age, race, body mass index, and Mini-Mental Status Examination score, protein carbonyls (nmol/mg) were associated with grip strength (β = −6.77, P < 0.01). The statistical association was unchanged after the analysis adjusted for hypertension, congestive heart failure, and depression. Ordered logistic regression models adjusted for the above factors showed that protein carbonyls are associated with increased odds of being in the lower quartiles of grip strength (odds ratio 8.74, 95% confidence interval 1.06–71.89, P = 0.043). These results suggest oxidative protein damage is independently associated with low grip strength among older women living in the community. Increased oxidative stress may be contributing to loss of muscle strength in older adults.
Tập 103 Số 1 - Trang 17-20 - 2007
Smaller organ mass with greater age, except for heart Autopsy/cadaver data indicate that many organs and tissues are smaller in the elderly compared with young adults; however, in vivo data are lacking. The aim of this study was to determine whether the mass of specific high-metabolic-rate organs is different with increasing age, using MRI. Seventy-five healthy women (41 African-Americans and 34 Caucasians, age range 19–88 yr) and 36 men (8 African-Americans and 28 Caucasians, age range 19–84 yr) were studied. MRI-derived in vivo measures of brain, heart, kidneys, liver, and spleen were acquired. Left ventricular mass (LVM) was measured by either echocardiography or cardiac gated MRI. Total body fat mass and fat-free mass (FFM) were measured with a whole body dual-energy X-ray absorptiometry (DXA) scanner. Multiple regression analysis was used to investigate the association between the organ mass and age after adjustment for weight and height (or DXA measures of FFM), race, sex, and interactions among these variable. No statistically significant interaction was found among age, sex, and race in any regression model. Significant negative relationships between organ mass and age were found for brain ( P < 0.0001), kidneys ( P = 0.01), liver ( P = 0.001), and spleen ( P < 0.0001). A positive relationship between LVM and age was found after adjustment for FFM ( P = 0.037). These findings demonstrate that age has a significant effect on brain, kidneys, liver, spleen, and heart mass. The age effect was independent of race and sex.
Tập 106 Số 6 - Trang 1780-1784 - 2009
Effects of metabolism and anesthesia on pulmonary ventilation Pulmonary ventilation and oxygen consumption of three groups of cats, anesthetized, decerebrated and anesthetized decerebrate, were measured before and after metabolic stimulation by 2:4-dinitrophenol. It was found that anesthesia does not alter quantitatively the respiratory response to an increase in metabolism. Comparison with earlier data shows that a unit increase in oxygen consumption produces a similar response in ventilation in man, dogs and cats, anesthetized or normal. This finding supports the theory that the muscles embody ‘metaboreceptors’ sensitive to metabolic activity which stimulate respiration in exercise. It is postulated that the classical ‘blood-gas’ control of breathing is of minor importance under normal conditions and that the variations in ventilation required during light and moderate exercise are brought about by neural mechanism only. Submitted on June 30, 1958
Tập 14 Số 1 - Trang 102-104 - 1959
Control of respiratory frequency Previous work has shown that for a given level of alveolar ventilation there is a particular respiratory frequency which is least costly in terms of respiratory work. There is also a particular frequency, usually a different one, which is least costly in terms of average force of the respiratory muscles. Evidence is presented that in the resting guinea pig and in man at rest and during exercise natural breathing takes place at frequencies approximating the second optimum. From additional observations on the effects of changing the mechanical characteristics of the respiratory system on respiratory frequency it is concluded that the principal site of the sensory end of the control mechanism is in the lungs. Submitted on November 19, 1959
Tập 15 Số 3 - Trang 325-336 - 1960
Role of tissue hypermetabolism in stimulation of ventilation by dinitrophenol Several authors have hypothesized that tissue hypermetabolism accounts for increases in ventilation (VE) elicited by 2,4-dinitrophenol. However, some data in the literature indicate that stimulation of VE by isomers of dinitrophenol is unrelated to tissue metabolic rate. To test this latter concept, we compared three different isomers of dinitrophenol (i.e., 2,4-dinitrophenol (2,4-DNP), 2,5-dinitrophenol (2,5,-DNP), 2,6-dinitrophenol (2,6-DNP) with respect to stimulation of VE and with respect to stimulation of oxygen consumption (VO2). In all experiments, 3–4 mg/kg of one dinitrophenol isomer was administered to chloralose anesthetized dogs by intra-arterial infusion. 2,4-DNP elicited large increments in both VE and VO2, 2,6-DNP elicited moderate increments in both VE and VO2, whereas 2,5-DNP elicited small increments in both VE and VO2. These observations demonstrate a correlation between ventilatory and metabolic changes affected by isomers of dinitrophenol. Accordingly, these results are consistent with the hypothesis that ventilatory stimulation by congeners of dinitrophenol is related to tissue hypermetabolism.
Tập 43 Số 1 - Trang 72-74 - 1977
Ventilatory response to muscular exercise: observations regarding a humoral pathway To assess the role of humoral mechanisms in eliciting the hyperpnea of muscular exercise, anesthetized dogs underwent complete spinal transection at the second lumbar level (L2). Muscular exercise of the denervated hindlimbs was then induced by electrical stimulation. Coincident with hindlimb muscle contraction, oxygen consumption (VO2) increased 173% and ventilation (VE) increased 163%; no statistically significant changes occurred in arterial carbon dioxide tension (PCO2), arterial pH, or arterial oxygen saturation. Similar results were obtained after peripheral chemodenervation and vagotomy plus spinal transection. In order to evaluate the possibility that extracranial receptors mediate the increases in VE elicited by exercise-induced humoral factors, heads of vagotomized L2 spinal-transected dogs were perfused entirely by a support dog with blood of unchanging gas composition via both carotid and both vertebral arteries. The carotid bodies lay within the region of the perfused head; the aortic bodies were denervated. These L2 spinal-transected head-perfused animals still responded to hindlimb exercise with a 156% increase in VO2 and a 122% increase in VE. We conclude that muscular exercise can stimulate VE via humoral factors other than usual chemical stimuli in arterial blood (i.e., PCO2, pH, or O2 saturation). Extracranial receptors (other than conventional peripheral arterial chemoreceptors) appear to mediate a major portion of the increase in VE elicited by exercise-induced humoral factors.
Tập 47 Số 1 - Trang 126-137 - 1979