Detection and neuromuscular response to respiratory loading in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is characterised by the repetitive narrowing or collapse of the upper airway during sleep. While anatomy is considered important in OSA pathogenesis it has been recognised that other factors must be involved. This thesis aimed to examine whether (i) sensory detection, and (ii) upper airway neuromuscular compensation, were impaired in awake OSA patients, in response to small negative pressure respiratory loads, close to the conscious detection threshold. It was reasoned that this may be important in OSA pathogenesis, as failure to detect and respond to minor airway patency threat may lead to worsening collapse which is difficult to remedy. Sensory detection was measured using the early P1 component of the respiratory related evoked potential (RREP). The RREP is the average cortical response to multiple presentations of the same respiratory stimulus and the P1 component is thought to represent arrival of somatosensory information at the cortex. The neuromuscular response was measured with genioglossus muscle intramuscular electromyogram (EMGgg). No significant differences were found between control and OSA participants in the threshold or the sensitivity of relationship between P1 amplitude and stimulus intensity. Also, there were no significant differences between control and OSA participants in the threshold or the sensitivity of the relationship between EMGgg amplitude and stimulus intensity. These results do not support the concept that a neuromuscular response deficit or a sensory detection deficit contribute to OSA pathogenesis. However, the neuromuscular results were confounded by a counterintuitive genioglossus suppression observed in a significant proportion of participants. This response was not more commonly observed in OSA participants and may be related to the centrally mediated protective reflex inhibition seen in other inspiratory muscles in response to sudden onset negative pressure. A methodological study examined the im