Optimal positive airway pressure predicts oral appliance response to sleep apnoea

Patients with less severe obstructive sleep apnoea (OSA) are usually prescribed oral appliances and/or smaller optimal nasal continuous positive airway pressure (P_nCPAP) in nCPAP therapy. We hypothesised that OSA patients with greater P_nCPAP would not respond favourably to oral appliances. Oral appliances were inserted in nCPAP users after washing-out the nCPAP effect. Follow-up polysomnography was undertaken with the adjusted oral appliance in place. The predictability of P_nCPAP was evaluated with receiver-operating characteristic (ROC) curves. The median baseline apnoea/hypopnoea index (AHI) was reduced with the oral appliance from 36 to 12 events·h⁻¹ in 35 patients. When responders were defined as patients showing a follow-up AHI of <5 events·h⁻¹ with >50% reduction in baseline AHI, the area under the ROC curve for P_nCPAP was 0.76. The best cut-off value of P_nCPAP turned out to be 10.5 cmH₂O with a high negative predictive value (0.93) and a low negative likelihood ratio (0.18). OSA patients with a P_nCPAP of >10.5 cmH₂O are unlikely to respond to oral appliance therapy. This prediction is clinically helpful to both OSA patients and medical personnel in discussing oral appliances as a temporary substitute and/or alternative for nCPAP.