Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Jan 2008
Respiratory-swallowing interactions during sleep in premature infants at term.
Non-nutritive swallowing occurs frequently during sleep in infants and is vital for fluid clearance and airway protection. Swallowing has also been shown to be associated with prolonged apnea in some clinical populations. What is not known is whether swallowing contributes to apnea or may instead help resolve these clinically significant events. ⋯ They did not trigger the respiratory pause, however, as most swallows (66%) occurred after respiratory pause onset and were often tightly linked to arousal from sleep. Swallows not associated with respiratory pauses (other than the respiratory inhibition to accommodate swallowing) and arousal occurred consistently during the expiratory phase of the breathing cycle. Results suggest that swallowing and associated arousal serve an airway protective role during sleep and medically stable preterm infants exhibit the mature pattern of respiratory-swallowing coordination by the time they reach term.
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Respir Physiol Neurobiol · Nov 2007
Randomized Controlled Trial Clinical TrialEffect of sildenafil on hypoxia-induced changes in pulmonary circulation and right ventricular function.
Hypoxia leads to pulmonary vasoconstriction in healthy men. However, the consequences on right ventricular function are not known. The effects of hypoxia on systolic pulmonary artery pressure (sPAP) and right ventricular function index (TEI) were assessed by Doppler echocardiography. ⋯ At 5245 m sPAP was 29.1(1.7) and TEI was 0.43(0.05) in the placebo group, while in the sildenafil group, both sPAP and TEI were reduced to 22(1.5) mm Hg and 0.23(0.03) (each p<0.005), respectively. We conclude that in healthy individuals, exposure to acute hypoxia and sojourns at high altitude result in a small but significant increase in sPAP accompanied by an impairment of right ventricular function. Sildenafil significantly decreases sPAP and improves right ventricular function.
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Respir Physiol Neurobiol · Nov 2007
Poor compensatory hyperventilation in morbidly obese women at peak exercise.
This study was designed to compare differences in pulmonary gas exchange at rest and at peak exercise in two groups of women: (1) physically active, non-obese women and (2) women with morbid obesity. Fourteen morbidly obese women (body mass index or BMI=49+/-7 kg/m2; peak oxygen consumption or VO2 peak=14+/-2 ml/(kg min)) and 14 physically active non-obese women (BMI=22+/-2 kg/m2; VO2 peak=50+/-6 ml/(kg min)) performed an incremental, ramped exercise test to exhaustion on a cycle ergometer. Arterial blood was sampled at rest and at peak exercise. ⋯ Only the non-obese women showed a decrease in PaCO2 rest to peak exercise (-5+/-3 mmHg). The slope between heart rate and VO2 during exercise was higher in the morbidly obese compared to non-obese women indicating that for the same absolute increase in VO2 a larger increase in heart rate is needed, demonstrating poorer cardiac efficiency in obese women. In conclusion, morbidly obese women have poorer exercise capacity, cardiac efficiency, and compensatory hyperventilation at peak exercise, and poorer gas exchange at rest compared to physically active, non-obese women.
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Respir Physiol Neurobiol · Sep 2007
Review Historical ArticleRespiratory physiology of high-altitude anurans: 55 years of research on altitude and oxygen.
In a 1951 paper, perhaps the first one addressing adjustments of respiratory physiology in high-elevation anurans, L. C. Stuart tested the hypothesis that hemoglobin values were higher in the high-elevation Bufo bocourti than in the low-elevation species Bufo marinus. ⋯ We start with the early search for evidence of physiological adjustments that took place in the 1960s, move to the studies with Telmatobius that dominated the 1970s and the 1980s, continue with the contributions of experimental physiology that characterized the 1990s, and finish with the discovery of mechanisms enhancing hemoglobin oxygen affinity in high-elevation anurans (2000s). When analyzing the last mentioned topic, we highlight the contributions by the late Professor Carlos Monge, to whom we dedicate this paper. Finally, we discuss the current state of the field, and propose directions for further studies.
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Respir Physiol Neurobiol · Sep 2007
ReviewRole of the peripheral chemoreflex in the early stages of ventilatory acclimatization to altitude.
This review of ventilatory acclimatization to altitude/hypoxia (VAH) emphasizes the widely differing timescales that VAH is considered to encompass. The review concludes: (1) that early (24-48h) VAH is unlikely to arise as a reaction to the respiratory alkalosis that is normally associated with exposure to hypoxia; (2) that changes in peripheral chemoreflex function may be sufficiently rapid to explain early VAH; (3) that alterations in gene expression induced by hypoxia through the hypoxia-inducible factor (HIF) signalling pathway may underlie a major component of VAH; and (4) that compensatory adjustments to acid-base balance in response to the initial respiratory alkalosis may have more significance for the slower changes observed later in VAH.