Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Dec 2016
Intratidal recruitment/derecruitment persists at low and moderate positive end-expiratory pressure in paediatric patients.
In paediatric patients positive end-expiratory pressure (PEEP) is traditionally set lower than in adults. We investigated whether moderately higher PEEP improves respiratory mechanics and regional ventilation. Therefore, 40 children were mechanically ventilated with PEEP 2 and 5cmH2O. ⋯ A higher PEEP improved peripheral ventilation. In conclusion, mechanically ventilated paediatric patients undergo intratidal recruitment/derecruitment which occurs more prominently in younger than in older children. A PEEP of 5cmH2O does not fully prevent intratidal recruitment/derecruitment but homogenizes regional ventilation in comparison to 2cmH2O.
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Respir Physiol Neurobiol · Oct 2016
Respiratory autoresuscitation following severe acute hypoxemia in anesthetized adult rats.
In the present study we investigated the pattern and efficacy of respiratory autoresuscitation in spontaneously breathing adult male rats across three separate anesthetic backgrounds. Each animal was administered one of three injectable anesthetics to achieve a surgical plane of anesthesia: ketamine-xylazine (KET, n=10), pentobarbital (PEN, n=10), or urethane (URE, n=10). Animals were tracheostomized and equipped with a femoral artery catheter to record airflow and arterial pressures. ⋯ Ketamine-xylazine and pentobarbital anesthesia can be reliably and effectively used to create models for the study of autoresuscitation in adult rats. In contrast, urethane causes catastrophic failure of respiratory autoresuscitation, by delaying or outright preventing the elaboration of gasping breaths following anoxia-induced respiratory arrest. The neuronal and synaptic alterations accompanying urethane anesthesia may therefore provide a means of understanding potential pathological alterations in rhythm generation that can predispose the respiratory control system to failed autoresuscitation following an episode of acute severe hypoxemia.
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Respir Physiol Neurobiol · Jul 2016
Inspiratory muscle performance in endurance-trained elderly males during incremental exercise.
The aim of this study was to compare the inspiratory muscle performance during an incremental exercise of twelve fit old endurance-trained athletes (OT) with that of fit young athletes (YT) and healthy age-matched controls (OC). The tension-time index (TT0.1) was determined according to the equation TT0.1=P0.1/PImax×ti/ttot, where P0.1 is the mouth occlusion pressure, PImax the maximal inspiratory pressure and ti/ttot the duty cycle. ⋯ At maximal exercise, P0.1/PImax ratio and TT0.1 was still lower in the OT group than OC group and higher than YT group. This study showed lower inspiratory muscle performance attested by a higher (TT0.1) during exercise in the OT group than YT group, but appeared to be less marked in elderly men having performed lifelong endurance training compared with sedentary elderly subjects.
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Respir Physiol Neurobiol · Jun 2016
The role of the Kölliker-Fuse nuclei in the determination of abdominal motor output in a perfused brainstem preparation of juvenile rat.
The abdominal muscles are largely quiescent during normal breathing but may exhibit tonic activity or subtle respiratory modulation. The origin of baseline abdominal motor nerve activity (AbNA) if present remains uncharacterised. The contribution of the Kölliker-Fuse nucleus (KF) in the dorsolateral pons in the patterning and amplitude of AbNA was investigated using in situ perfused brainstem preparations of juvenile rats (n=12). ⋯ Interestingly, the type of AbNA exhibited correlated with postinspiratory duration. Targeted microinjections of GABA-A receptor agonist isoguvacine (10mM; 70nl) into KF however did not significantly modify pattern or amplitude of baseline AbNA in either Type besides the selective abolition of the postinspiratory phase and, consequently, postinspiratory modulation in AbNAwhen present. In sum, the KF is not a major contributorin setting baseline abdominal motor output.
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Respir Physiol Neurobiol · Jan 2016
Physiological responses to Tai Chi in stable patients with COPD.
We compared the physiological work, judged by oxygen uptake, esophageal pressure swing and diaphragm electromyography, elicited by Tai Chi compared with that elicited by constant rate treadmill walking at 60% of maximal load in eleven patients with COPD (Mean FEV1 61% predicted, FEV1/FVC 47%). Dynamic hyperinflation was assessed by inspiratory capacity and twitch quadriceps tension (TwQ) elicited by supramaximal magnetic stimulation of the femoral nerve was also measured before and after both exercises. The EMGdi and esophageal pressure at the end of exercise were similar for both treadmill exercise and Tai Chi (0.109±0.047 mV vs 0.118±0.061 mV for EMGdi and 22.3±7.1 cmH2O vs 21.9±8.1 cmH2O for esophageal pressure). ⋯ Both Tai Chi and treadmill exercise elicited a fall in IC at end exercise, indicating dynamic hyperinflation, but this was statistically significant only after treadmill exercise. TwQ decreased significantly after Tai Chi but not after treadmill. We conclude that Tai Chi constitutes a physiologically similar stimulus to treadmill exercise and may therefore be an acceptable modality for pulmonary rehabilitation which may be culturally more acceptable in some parts of the world.