Active glottal closure during anoxic gasping in lambs

Thuot, François; Lemaire, D; Dorion, Dominique; Létourneau, Patrick; Praud, Jean‐Paul

doi:10.1016/s0034-5687(01)00272-9

Cited by 22 publications

(19 citation statements)

References 24 publications

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“…To date, nHFOV is the only condition during which continuous active glottal closure was absent during central apneas in our neonatal ovine models. This cannot be related to the absence of hypocapnia since the latter was obviously absent in anoxic gasping [28]. Hence, it is rather related to afferent messages originating from airway and/or thoracic wall mechanoreceptors stimulated by the constant positive pressure (MAP at 8 cm H 2 O) and/or ventilator oscillations.…”

Section: Discussionmentioning

confidence: 99%

Laryngeal Muscle Activity during Nasal High-Frequency Oscillatory Ventilation in Nonsedated Newborn Lambs

et al. 2015

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Background: We have previously shown that nasal pressure support ventilation (nPSV) can lead to an active inspiratory laryngeal narrowing in lambs. This, in turn, can limit lung ventilation and divert air into the digestive system, with potentially deleterious consequences. On the other hand, nasal high-frequency oscillatory ventilation (nHFOV) is particularly attractive in newborns, especially since, unlike nPSV, it does not require synchronization with the patient's inspiratory efforts. Objectives: The main aim of the present study was to test the hypothesis that glottal constrictor muscle activity (EMG) does not develop during nHFOV. A secondary objective was to study laryngeal EMG during nHFOV-induced central apneas. Methods: Polysomnographic recordings were performed in 7 nonsedated lambs which were ventilated with increasing levels of nPSV and nHFOV at both 4 and 8 Hz, in random order. States of alertness, diaphragm and glottal muscle EMG, SpO₂, and respiratory movements were continuously recorded. Results: While phasic inspiratory glottal constrictor EMG appeared with increasing nPSV levels in 6 out of 7 lambs, it was never observed with nHFOV. In addition, nHFOV at 4 Hz dramatically inhibited central respiratory drive in 4/7 lambs, with 64-100% of recording time spent in central apnea in 3 lambs. No glottal constrictor EMG was observed during these central apneas. Conclusion: nHFOV does not induce glottal constrictor muscle EMG in nonsedated newborn lambs, in contrast to nPSV. This may be an additional advantage of nHFOV relative to nPSV.

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Section: Discussionmentioning

confidence: 99%

Laryngeal Muscle Activity during Nasal High-Frequency Oscillatory Ventilation in Nonsedated Newborn Lambs

et al. 2015

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“…Conversely, phasic inspiratory TA EMG is rare with eupneic breathing (37) and has been observed only in limited experimental or pathological conditions such as anoxic gasping (15,30,46), hypoxia (9), C fiber stimulation by capsaicin (31), upper airway occlusion (21), or in patients with amyotrophic lateral sclerosis (16). Consequences and mechanisms of phasic inspiratory TA EMG in the above conditions are unclear.…”

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confidence: 99%

Laryngeal response to nasal ventilation in nonsedated newborn lambs

Moreau-Bussière¹,

Samson²,

St-Hilaire³

et al. 2007

Journal of Applied Physiology

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Although endoscopic studies in adult humans have suggested that laryngeal closure can limit alveolar ventilation during nasal intermittent positive pressure ventilation (nIPPV), there are no available data regarding glottal muscle activity during nIPPV. In addition, laryngeal behavior during nIPPV has not been investigated in neonates. The aim of the present study was to assess laryngeal muscle response to nIPPV in nonsedated newborn lambs. Nine newborn lambs were instrumented for recording states of alertness, electrical activity [electromyograph (EMG)] of glottal constrictor (thyroarytenoid, TA) and dilator (cricothyroid, CT) muscles, EMG of the diaphragm (Dia), and mask and tracheal pressures. nIPPV in pressure support (PS) and volume control (VC) modes was delivered to the lambs via a nasal mask. Results show that increasing nIPPV during wakefulness and quiet sleep led to a progressive disappearance of Dia and CT EMG and to the appearance and subsequent increase in TA EMG during inspiration, together with an increase in trans-upper airway pressure (TUAP). On rare occasions, transmission of nIPPV through the glottis was prevented by complete, active glottal closure, a phenomenon more frequent during active sleep epochs, when irregular bursts of TA EMG were observed. In conclusion, results of the present study suggest that active glottal closure develops with nIPPV in nonsedated lambs, especially in the VC mode. Our observations further suggest that such closure can limit lung ventilation when raising nIPPV in neonates. thyroarytenoid muscle; cricothyroid muscle; diaphragm; states of alertness; intermittent positive-pressure ventilation NASAL INTERMITTENT positive-pressure ventilation (nIPPV) is increasingly used in the neonatal period (12) as treatment for respiratory distress syndrome (22) and apneas of prematurity (3,27) and as a bridge between endotracheal tube ventilation and spontaneous ventilation (6,19). Previous studies using endoscopic observations in adult humans have shown that laryngeal closure can occur during nIPPV, especially in the volume control (VC) mode (17, 18, 34 -36). In addition, laryngeal closure appears to increase with increasing ventilatory support, together with decreasing subglottal (alveolar) ventilation (40). Such laryngeal behavior is of high clinical importance since it has been linked to falls in oxygen saturation when increasing nIPPV during sleep in adult humans (7) and could divert positive pressure from the airways, leading to increased gastric distension (11). However, although the glottal closure observed endoscopically during nIPPV suggests an active contraction of glottal constrictor muscles, there are, to our knowledge, no data on glottal muscle electromyograms (EMG) during nIPPV. Moreover, there are no currently available studies on laryngeal dynamics during nIPPV in the neonatal period. Thus the aim of the present study was to test the hypotheses that 1) glottal narrowing during nIPPV is also present in the neonatal period, especially in the VC mode; and 2) glottal...

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“…This coupled with a forced inspiratory effort would provide adequate ventilation (12). Thus, this pattern can be seen as an attempt of the respiratory network to overcome hypoxia and may play a crucial role for autoresuscitation (12,26).…”

Section: Discussionmentioning

confidence: 99%

“…However, the question as to what happens to glottal constrictor activity early in expiration during hypoxia-induced gasping is raised. On the basis of previous reports, this seems to be inconsistent (11)(12)(13) and may relate to the severity and the length of exposure to hypoxia/anoxia. In one study, gasping during severe hypoxia was reported to be accompanied by a massive reduction or total abolishment of postinspiratory motor activity destined for the upper airway (11,14).…”

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confidence: 93%

Dynamic Changes in Glottal Resistance during Exposure to Severe Hypoxia in Neonatal Rats In Situ

Dutschmann

Paton

2005

Pediatr Res

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The neural control of respiratory airflow via the vocal fold is characterized by inspiratory abduction and postinspiratory (early expiratory) adduction causing decreases and increases in glottal resistance, respectively. The postinspiratory increase in glottal resistance plays a major role in braking the speed of expiratory airflow, to act against the high recoil pressure of the neonatal rat lung. In the present study, we investigated changes in upper airway patency during severe hypoxia in neonatal rats. We measured dynamic changes in subglottal pressure during normoxic and hypoxic conditions in an arterially perfused brainstem preparation in which we could control gas tensions accurately. Initially, hypoxia (5% O 2 , 5% CO 2 , and 90% nitrogen) produced an excitatory response in phrenic nerve activity accompanied by augmentation of both inspiratory-related glottal dilation and postinspiratory glottal constriction. Later, during the early stages of hypoxia-induced respiratory depression and initiation of gasping, we observed a massive reduction of the respiratory modulation of glottal resistance. In most preparations, this was transient and replaced by a paradoxic inspiratory-related glottal constriction. We propose that during severe hypoxia in the in situ preparation, paradoxic inspiratory glottal constriction can be observed during gasping, and this may impair ventilation despite the persistence of rhythmic contractions of the respiratory muscles. The latter is of clinical interest, because this may relate to the finding of cot death victims who died as a result of upper airway obstruction but without apparent apnea or rebreathing. Classically, hypoxia triggers a biphasic respiratory response that consists of an initial augmentation, then a marked depression of ventilation; this is followed by gasping until death (1). The characteristics of the hypoxic ventilatory response undergoes postnatal maturation (2). For example, in neonates, the early increase in respiration in response to hypoxia is less pronounced (2). However, neonates have a remarkable tolerance to hypoxia and robust mechanisms for autoresuscitation after hypoxia-induced respiratory depression (3-5). A major component for successful autoresuscitation is gasping (4,5), a breathing pattern triggered during marked hypoxia or anoxia. Because hypoxia is a common complication in the human neonate (3), a knowledge of the precise physiologic response to hypoxia is of clinical interest.Gasping is a unique breathing pattern defined as having a decrementing inspiratory discharge (as opposed to the augmenting pattern of eupnea) and a synchronization of inspiratory discharges in cranial (vagal, hypoglossal) and phrenic motor outflows (6 -8). In eupnea, there is a highly coordinated initiation of the motor pattern sequence of upper airway and respiratory pump motor activity such that the latter is temporally delayed so that decrease of upper airway resistance can precede the onset of lung inflation. This being the case, the respiratory cycle can be divided in...

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Active glottal closure during anoxic gasping in lambs

Cited by 22 publications

References 24 publications

Laryngeal Muscle Activity during Nasal High-Frequency Oscillatory Ventilation in Nonsedated Newborn Lambs

Laryngeal Muscle Activity during Nasal High-Frequency Oscillatory Ventilation in Nonsedated Newborn Lambs

Laryngeal response to nasal ventilation in nonsedated newborn lambs

Dynamic Changes in Glottal Resistance during Exposure to Severe Hypoxia in Neonatal Rats In Situ

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