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

Abstract

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.

Non-invasive high-frequency oscillatory ventilation in neonates: review of physiology, biology and clinical data

“…Thus, patient-ventilator interaction could be better during NHFOV than with conventional NIV. However, the same study showed suppression of central respiratory drive when nasal-mask-delivered NHFOV was applied at 4 Hz 23. This effect was not mediated by hypocarbia and could be linked to several phenomena, such as an increase in vagal pulmonary stretch receptor activity24 or thoracic wall afferent activity 25.…”

“…This is an advantage given the difficulties in achieving good synchronisation during neonatal NIV and because a poor patient-ventilator interaction may significantly decrease ventilation efficiency 22. Interestingly, an animal study showed that, in contrast to non-invasive pressure support ventilation, NHFOV did not induce phasic inspiratory glottal constriction and conversely did not decrease inspiratory glottal dilatation 23. Thus, patient-ventilator interaction could be better during NHFOV than with conventional NIV.…”

High-frequency ventilation for non-invasive respiratory support of neonates

“…During normal spontaneous breathing, laryngeal muscles act in synchrony to open the upper airway during inspiration, decreasing resistance and easing the flow of gas through the glottis [33]. Recent studies have demonstrated that normal muscle activity during inspiration is markedly altered with the application of pressure-supported NIPPV (Table 4) [33–35]. NIPPV induces an increase in inspiratory constrictor (thryoarytenoid) muscle activity while suppressing normal inspiratory dilator (cricothyroid) muscle activity, with these effects augmented as NIPPV support is increased [33–35].…”

“…Recent studies have demonstrated that normal muscle activity during inspiration is markedly altered with the application of pressure-supported NIPPV (Table 4) [33–35]. NIPPV induces an increase in inspiratory constrictor (thryoarytenoid) muscle activity while suppressing normal inspiratory dilator (cricothyroid) muscle activity, with these effects augmented as NIPPV support is increased [33–35]. Contrary to the effect of NIPPV, the application of HFNV was shown not to increase inspiratory constrictor muscle activity while maintaining normal dilator muscle activity [35] (Table 4).…”

“…NIPPV induces an increase in inspiratory constrictor (thryoarytenoid) muscle activity while suppressing normal inspiratory dilator (cricothyroid) muscle activity, with these effects augmented as NIPPV support is increased [33–35]. Contrary to the effect of NIPPV, the application of HFNV was shown not to increase inspiratory constrictor muscle activity while maintaining normal dilator muscle activity [35] (Table 4). Furthermore, in support of improving V T delivery at lower high-frequency rates, HFNV at 4 Hz (compared to 8 Hz) was accompanied by lower rates of spontaneous breathing, often apneic in nature, while maintaining normal pCO 2 values [35].…”