PubMed · 4102981
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1971-05-22. Bromhexine.. https://pubmed.ncbi.nlm.nih.gov/4102981/
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Eupnoeic breathing in mammals is dependent on the co-ordinated activity of cranial and spinal motor outputs to both ventilate the lungs and adjust respiratory airflow, which they do by regulating upper-airway resistance. We investigated the role of central glycinergic inhibition in the co-ordination of cranial and spinal respiratory motor outflows. We developed an arterially perfused neonatal rat preparation (postnatal age 0-4 days) to assess the effects of blocking glycine receptors with systemically administered strychnine (0.5-1 microM). We recorded respiratory neurones located within the ventrolateral medulla, inspiratory phrenic nerve activity (PNA) and recurrent laryngeal nerve activity (RLNA), as well as dynamic changes in laryngeal resistance. Central recordings of postinspiratory neurones revealed an earlier onset in firing relative to the onset of inspiratory PNA after exposure to strychnine (260 +/- 38.9 vs. 129 +/- 26.8 ms). After glycine receptor blockade, postinspiratory neurones discharged during the inspiratory phase. Strychnine also evoked a decrease in PNA frequency (from 38.6 +/- 4.7 to 30.7 +/- 2.8 bursts min(-1)), but amplitude was unaffected. In control conditions, RLNA comprised inspiratory and postinspiratory discharges; the amplitude of the latter exceeded that of the former. However, after administration of strychnine, the amplitude of inspiratory-related discharge increased (+65.2 +/- 15.2 %) and exceeded postinspiratory activity. Functionally this change in RLNA caused a paradoxical, inspiratory-related glottal constriction during PNA. We conclude that during the first days of life in the rat, glycine receptors are essential for the formation of the eupnoeic-like breathing pattern as defined by the co-ordinated activity of cranial and spinal motor inspiratory and postinspiratory activities.
On the basis of two observations that avoiding prone sleeping decreased incidence of sudden infant death syndrome and that obstructive sleep apnea is closely linked with the syndrome, we hypothesized that the prone position may increase upper airway collapsibility in infants and small children. Passive pharyngeal collapsibility of 19 infants and small children (10-101 weeks old) was examined in three postures: supine with face straight up, supine with neck rotated, and prone with neck rotated. The collapsibility was evaluated with the maximal distension of the most collapsible region, pharyngeal stiffness, and pharyngeal closing pressure, estimated from static pressure-area relationship of the passive pharynx. No significant changes in pharyngeal stiffness were detected; however, maximal distension was reduced in the prone position (mean +/- SD, 0.56 +/- 0.26 versus 0.44 +/- 0.20 cm(2); supine with face straight up versus prone position, p < 0.05). Pharyngeal closing pressure increased at neck rotation in the supine position (-4.5 +/- 2.4 versus -2.8 +/- 2.3 cm H(2)O; supine with face straight up versus supine with neck rotated, p < 0.05), and a further increase was observed in the prone position (-0.3 +/- 2.9 cm H(2)O, p < 0.05 versus supine with neck rotation). Pharyngeal closing pressure in the prone position was above atmospheric pressure in half of our subjects, whereas all subjects had negative pharyngeal pressure in the supine position. We conclude that the prone position increases upper airway collapsibility, although the mechanism is yet unclear.
OBJECTIVE: In this study, we would like to show that anterior rhinometry measurement of nasal resistance would be a simple and useful test to identify severe obstructive sleep apnea (OSA) in a population of children affected by adenotonsillar hypertrophy. METHODS: Seventy-three consecutive children (44 males; mean age 5.4+/-1.2 years) with adenotonsillar hypertrophy, who complained sleep-disordered breathing, were studied. All the parents completed a questionnaire concerning the children's sleeping habits and sleep complaints before consultation; each child underwent a general paediatric examination and an evaluation of craniofacial features and upper airway patency. In all 73 children polysomnography was performed and anterior rhinometry nasal patency was measured. RESULTS: The diagnosis of OSA was confirmed in 44/73 patients (60%). Total nasal resistance showed a significant direct correlation with apnea hypopnea index, arousal index, snoring time, percentage of sleep time spent at SaO(2)<90% and a significant inverse correlation with total sleep time, sleep efficiency and the mean of SaO(2)% during sleep. Total nasal resistance was significantly related to snoring, mouth breathing and daytime sleepiness. The receiver operator characteristics (ROC) curve indicates that in the range of age of our sample a nasal resistance value of 0.59 Pa/cm(3)/s has a sensitivity of 91% and specificity of 96% for identifying the children with adenotonsillar hypertrophy affected by OSA. CONCLUSIONS: Our study shows that in children with adenotonsillar hypertrophy nasal resistance seems to be risk factor for OSA. The anterior rhinometry appears as a useful tool in routine evaluation of sleep-disordered breathing in these patients.