Modulation of laryngeal and respiratory pump muscle activities with upper airway pressure and flow

Abstract

The hypothesis that upper airway (UA) pressure and flow modulate respiratory muscle activity in a respiratory phase-specific fashion was assessed in anesthetized, tracheotomized, spontaneously breathing piglets. We generated negative pressure and inspiratory flow in phase with tracheal inspiration or positive pressure and expiratory flow in phase with tracheal expiration in the isolated UA. Stimulation of UA negative pressure receptors with body temperature air resulted in a 10--15% enhancement of phasic moving-time-averaged posterior cricoarytenoid electromyographic (EMG) activity above tonic levels obtained without pressure and flow in the UA (baseline). Stimulation of UA positive pressure receptors increased phasic moving-time-averaged thyroarytenoid EMG activity above tonic levels by 45% from baseline. The same enhancement of posterior cricoarytenoid or thyroarytenoid EMG activity was observed with the addition of flow receptor stimulation with room temperature air. Tidal volume and diaphragmatic and abdominal muscle activity were unaffected by UA flow and/or pressure, whereas respiratory timing was minimally affected. We conclude that laryngeal afferents, mainly from pressure receptors, are important in modulating the respiratory activity of laryngeal muscles.

Laryngeal response to nasal ventilation in nonsedated newborn lambs

“…Reflexes originating from the upper airways can also be at play, secondary to loss of negative inspiratory pressure. Indeed, this negative inspiratory pressure normally increases posterior cricoarytenoid muscle activity in eupneic breathing (44). Finally, while passive hypocapnia reduces inspiratory CT EMG (24), this mechanism is most likely not involved in the present study, as explained previously for TA EMG.…”

“…Alternatively, increased afferent activity from positive pressure receptors in the upper airways (pharynx and/or larynx) (33,43) could be involved in the activation of inspiratory TA EMG, as suggested by recent results from experiments on isolated larynx in piglets (44). Involvement of other laryngeal receptors such as "flow" (thermal) receptors (43,44) during nIPPV is less likely, since insufflated air utilized in the present study was heated and humidified. Finally, while passive hyperventilation to hypocapnia using nIPPV has been shown to activate TA EMG during expiration (24), involvement of this mechanism would at best be marginal.…”

“…As recently reviewed (2), available but scarce data suggest that, while stimulation of slow adapting receptors inhibits TA EMG (5, 13), stimulation of rapidly adapting receptors or C fibers could enhance phasic TA EMG, although in the expiration phase (14,45). Alternatively, increased afferent activity from positive pressure receptors in the upper airways (pharynx and/or larynx) (33,43) could be involved in the activation of inspiratory TA EMG, as suggested by recent results from experiments on isolated larynx in piglets (44). Involvement of other laryngeal receptors such as "flow" (thermal) receptors (43,44) during nIPPV is less likely, since insufflated air utilized in the present study was heated and humidified.…”

Noninvasive ventilation and the upper airway: should we pay more attention?

“…Stella and England studied the effect of pressure and flow in isolated piglet upper airway [28]. They showed that the presence of negative pressure in the upper airway and flow during inspiration results in phasic respiratory activity of the posterior cricoarytenoid muscle above tonic levels, which results in glottic widening during inspiration and reduces resistance to airflow.…”

“…Furthermore, positive pressure and expiratory flow increased the thyroarytenoid activity for all stimuli, although constant room air applied to the upper airway results in more activity of the thyroarytenoid muscle than an oscillatory stimulus, implying that constant room air results in enhanced constriction of the glottis. Accordingly, both pressure and flow receptors play an important role in muscle activity of the upper airway during respiration [28,30]. …”