Role of phrenic nerve afferents in the control of breathing

Abstract

A long-held belief is that respiratory-related reflexes mediated by afferents in the diaphragm are weak or absent. However, recent data suggest that diaphragmatic afferents are capable of altering ventilatory motor drive as well as influencing perception of added inspiratory loads in humans. This review describes the sensory elements of the diaphragm, their central projections, and their functional significance in the control of respiratory muscle activation. The reflexes elicited by electrical stimulation of phrenic nerve afferents and the contribution of diaphragmatic afferents in respiratory load compensation and perception are considered. There is growing evidence that phrenic nerve afferents are activated under a variety of conditions. However, the significance of this input to the central nervous system is yet to be discerned.

Phrenic nerve afferents elicited cord dorsum potential in the cat cervical spinal cord

“…Although the PnA projection pathways to the cerebral cortex remain unknown, the present study supports a dorsal column mediated pathway that likely involves a multisynaptic thalamic relayed projection (Zhang et al, 2003). It has been shown in the previous studies (Frazier et al, 1991) that C-fiber afferents have much higher threshold and longer latency for PnA stimulation than group Ia, Ib and group II afferents. Conduction velocities for C-fibers are less than 1 m/s.…”

“…These results are consistent with PnA entering the cervical spinal cord, projecting to the dorsal horn, which then relays PnA to the brainstem, and projects phrenic afferent information to the somatosensory cortex via a thalamocortical pathway (Zifko et al, 1995;Zhang et al, 2003). The function of this putative pathway could be related to the proprioceptive control of respiratory muscles and respiratory movement control originating in the motor cortex (Frazier et al, 1991). Davenport et al (1985) proposed that the PnA projection to the postcruciate region of the cerebral cortex may play a role in higher brain center control of the respiratory pump.…”

Effects of airway occlusion on breathing muscle electromyogram signals, during isoflurane anaesthesia, with and without the effects of fentanyl and hypercapnia

“…24 Studies of airway occlusion suggest that diaphragm afferents may have a role in the responses to load. 25 Our findings do not support the presence of possible reflex actions during isoflurane anaesthesia.…”

Nocturnal pulse oximetry: a new approach to establish the appropriate time for non‐invasive ventilation in ALS patients

“…This finding confirms the power of the homeostatic mechanism controlled by peripheral chemoreceptors, which are not affected in ALS. 26,27 Nonetheless, even a small decrease in oxygen saturation overnight can be very important, and this parameter showed a positive predictive value for total survival (see Fig. 3).…”