Journal of applied physiology
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Multiple breath nitrogen washout (MBNW) indices provide insight into ventilation heterogeneity globally [lung clearance index (LCI)] and within acinar (Sacin) and conducting (Scond) airways. Normal aging leads to an accelerated deterioration of Sacin in older adults, but little is known about the contribution of peripheral airway function to changes in pulmonary function indices reflecting expiratory airflow [forced expiratory volume in one second (FEV1)/forced vital capacity (FVC)] and gas trapping [residual volume (RV)/total lung capacity (TLC)] with aging. We aimed to examine associations between MBNW and FEV1/FVC as well as RV/TLC in healthy adults, and to determine if these relationships differ in older (≥50 yr) versus younger subjects (<50 yr). ⋯ NEW & NOTEWORTHY This study explores associations between multiple breath nitrogen washout (MBNW) and standard pulmonary function indices reflecting expiratory airflow [forced expiratory volume in one second (FEV1)/forced vital capacity (FVC)] and gas trapping [residual volume (RV)/total lung capacity (TLC)] in healthy adults across a wide range of ages. We have demonstrated statistically significant relationships between MBNW and FEV1/FVC as well as RV/TLC. These findings provide novel evidence of the contribution of peripheral airway function to changes in standard pulmonary function indices with aging.
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In vitro and in vivo anesthetized studies led to the conclusion that "deficiencies in one neuromodulator are immediately compensated by the action of other neuromodulators," which suggests an interdependence among neuromodulators. This concept was the focus of the 2018 Julius H. Comroe Lecture to the American Physiological Society in which I summarized our published studies testing the hypothesis that if modulatory interdependence was robust, breathing would not decrease during dialysis of antagonists to G protein-coupled excitatory receptors or agonists to inhibitory receptors into the ventral respiratory column (VRC) or the hypoglossal motor nuclei (HMN). ⋯ Bilateral dialysis of receptor antagonists or agonist in the VRC increased breathing, which does not support the concept that unchanged breathing with unilateral dialyses was due to contralateral compensation. In contrast, in the HMN neither unilateral nor bilateral dialysis of the excitatory receptor antagonists altered breathing, but unilateral dialysis of the opioid receptor agonist decreased breathing. We conclude: 1) there is site-dependent interdependence of neuromodulators during physiologic conditions, and 2) attributing physiologic effects to a specific receptor perturbation is complicated by local compensatory mechanisms.
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Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Therefore, our objective was to investigate whether impairment of CAN structures is involved in the pathophysiology of NOH. ⋯ Our result reveal that patients with autonomic dysfunction caused by postganglionic sympathetic impairment also have impaired activation of structures within the cortical autonomic network. Impaired activation is evident during a test of sympathetic, but not parasympathetic, activation. Impaired cortical autonomic networks associated with sympathetic activation may be involved in the pathophysiology of NOH.
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The validity and safety of using supramaximal verification (Smax) to confirm a maximal effort during cardiopulmonary exercise testing (CPET) in people with cystic fibrosis (CF) and/or those with severe disease has been questioned. Therefore, this study aimed to investigate these concerns in children, adolescents, and adults with mild-to-severe CF lung disease. Retrospective analysis of 17 pediatric and 28 adult participants with CF [age range: 9.2-62.9 y; forced expiratory volume in 1 s: 66.7% (range: 29.9%-102.3%); 30 men] who completed a routine ramp-incremental cycling test to determine peak oxygen uptake (V̇o2peak) was studied. ⋯ Given the clinical importance of aerobic fitness in people with CF, incorporating Smax is recommended to provide a safe and valid measure of V̇o2max in children, adolescents, and adults who span the spectrum of CF disease severity. NEW & NOTEWORTHY Incorporating supramaximal verification into cardiopulmonary exercise testing protocols did not increase the frequency of adverse events or perceived discomfort versus a single-phase incremental exercise test in people with mild-to-severe cystic fibrosis. Furthermore, a valid measure of maximal oxygen uptake (V̇o2max) was obtained from 85.7% of pediatric and 96.4% of adult exercise tests, whereas peak oxygen uptake underestimated aerobic fitness in comparison with V̇o2max in 21.4% of cases (by up to 24.4%).
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Evidence suggests that septic shock patients with chronic arterial hypertension may benefit from resuscitation targeted to achieve higher blood pressure values than other patients, possibly as a result of altered renal autoregulation. The effects of different vasopressor agents on renal autoregulation may be important in this context. We investigated the effects of arginine vasopressin (AVP) and norepinephrine (NE) on renal autoregulation in ovine septic shock. ⋯ After development of shock, the autoregulatory threshold was lower with AVP than with NE (59±5 vs. 65±7 mmHg, p=0.010). However, RBF was higher with NE both at the start of autoregulatory measurements (206±58 vs. 170±52 mL/min; p=0.050) and at the autoregulatory threshold (191±53 vs. 150±47 mL/min; p=0.008). As vasopressors may have different effects on renal autoregulation, blood pressure management in patients with septic shock should be individualized and take into account drug-specific effects.