Influence of head and neck position on the performance of supraglottic airway devices: A systematic review and meta-analysis

BACKGROUND: Changes in head and neck position may significantly affect the performance of supraglottic airway devices (SADs) by altering the pharyngeal structure. PURPOSE: This systematic review and meta-analysis aimed to elucidate the effect of changes in head and neck position on performance of SADs. DATA SOURCE: Bibliographic databases, including PubMed, EMBASE, the Cochrane library, and the Web of Science. STUDY ELIGIBILITY CRITERIA: Prospective studies investigating the effects of head and neck positions on the performance of SADs. METHODS: A random effect model was applied in the all analyses. Subgroup analysis was performed according to the type of device and the age of patient. The oropharyngeal leak pressure was the primary outcome measure. Secondary outcome measures included peak inspiratory pressure, fibreoptic view, and ventilation score (PROSPERO, CRD42017076971). RESULTS: Seventeen studies met the eligibility criteria. Overall, the oropharyngeal leak pressure significantly increased (mean difference 4.07 cmH(2)O; 95% confidence interval 3.30 to 4.84) during neck flexion with adverse effects on ventilation and fibreoptic view. Conversely, the oropharyngeal leak pressure decreased (mean difference −4.05; 95% confidence interval −4.90 to −3.20) during neck extension with no significant effect on ventilation or fibreoptic view. Rotation of the head and neck did not significantly affect SAD performance. CONCLUSIONS: The reduced oropharyngeal leak pressure in the extended neck position was not associated with impaired ventilation except with the air-Q self-pressurizing airway. The flexed neck position significantly worsens ventilation and the alignment between the SAD and glottis despite improving the seal except with the air-Q self-pressurizing airway and LMA Proseal.