Respiratory-related evoked potential elicited in tracheostomised lung transplant patients

Abstract

The present study investigated the role of removal of upper airway and lung vagal afferents in the respiratory-related evoked potential (RREP) response to inspiratory occlusions in two patients with a tracheostomy, who had undergone double lung transplantation (DLT).The patients were 1.5 and 3 months post-DLT and surgical placement of the tracheostomy. RREP recordings in response to inspiratory occlusions were obtained under four conditions: mouth breathing ignore trial; mouth breathing attend trial; tracheostomy breathing attend trial; and tracheostomy breathing ignore trial.The RREP peak components, Nf, P1 and N1, were present in both mouth and tracheostomy ignore breathing trials. The P300 was present in both mouth and tracheostomy attend trials. RREP peak latencies were similar between conditions. The peak amplitudes were greater with mouth breathing due to greater occlusion-related inspiratory pressure.These results demonstrate that the respiratory-related evoked potential can be elicited with inspiratory occlusion in the absence of mouth, upper airway and lung vagal afferent input. This suggests that inspiratory occlusion can elicit cortical activity with activation of inspiratory pump mechanoreceptors.KEYWORDS: Cerebral cortex, inspiratory occlusion, respiratory muscles W hen ventilation is obstructed, stimulated, challenged or attended to, these changes induce cognitive awareness of breathing. Cognitive awareness of the mechanical status of ventilation is essential for patient respiratory self-management and requires that respiratory-related afferent information be made available to regions of the cerebral cortex that permit conscious awareness of, and attention to, breathing. The respiratory-related evoked potential (RREP) is a unique measure of cerebral cortical activity elicited by breathing against a mechanical load. It provides quantification of both the initial arrival and processing of afferent information at the primary sensory cortex and its subsequent cognitive processing by other associative cortical areas. These neural processes result in patients orienting attention towards ventilation, fear, anxiety, sleep state and behaviour. Induced awareness of ventilation is of profound protective importance, alerting the patient to disrupted ventilation. Failure of cognitive awareness of respiratory mechanical changes is one cause of life-threatening asthmatic attacks [1][2][3]. It is likely that the RREP is mediated by multiple respiratory mechanoreceptor populations; however, the afferents mediating the RREP remain unknown.The RREP has been elicited via inspiratory occlusion, inspiratory loads and negative pressures applied during an inspiration [4][5][6][7][8]. The RREP has been recorded from scalp electrodes in humans and subdural electrodes in lambs [4,9]. The short-latency P1 peak of the RREP is generated in the somatosensory cortex [9,10]. The P1 peak of the RREP can be elicited via inspiratory occlusion in humans with lung vagal denervation [8]. However, it is not known whether inspir...

Abnormal respiratory‐related evoked potentials in untreated awake patients with severe obstructive sleep apnoea syndrome

“…Indeed, such a finding is in line with the lack of effect of upper airway anaesthesia on the RREPs (Redolfi et al, 2005). It is also in line with the likely redundant nature of these potentials that are considered by some to have multiple sources in the respiratory system (Davenport et al, 2006).…”

“…, 2005). It is also in line with the likely redundant nature of these potentials that are considered by some to have multiple sources in the respiratory system (Davenport et al. , 2006).…”

Cortical Processing of Respiratory Occlusion Stimuli in Children with Central Hypoventilation Syndrome

“…The results from the present study are more supportive of those reported by Davenport and colleagues, because P1 and Nf components were visible in both conditions in all three patients. As reported in Davenport and colleagues' study (19), there appeared to be a tendency for the components to be smaller in the tracheostomy condition, although this could not be tested statistically due to the small sample size. Also in agreement with the study conducted by Davenport and colleagues (19), the average occlusion pressure response was slightly smaller in the tracheotomy condition, and thus may have contributed to the smaller RREP components.…”

“…Interestingly, however, the same group reported no impact of upper airway anesthesia on the RREP (18). Davenport and colleagues (19) reported data from two double-lung transplant patients and compared mouthpiece with tracheostomy occlusions in the patients and with mouthpiece occlusions in nine control subjects. Patients demonstrated P1, Nf, and P300 components in response to the tracheostomy occlusions, although they had reduced amplitudes relative to the components seen in response to mouthpiece occlusions, a result that the authors attributed to the reduced occlusion-related pressure change elicited in the tracheostomy condition.…”

“…The RREP method provides a unique way to investigate the neural integration mechanisms mediating respiratory load perception during both wakefulness (4,(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and sleep (12,14,16,23,24).…”