Influence of head extension, flexion, and rotation on collapsibility of the passive upper airway.
OBJECTIVE
To determine the effect of head posture on upper airway collapsibility and site of collapse of the passive human upper airway.


METHODS
Pharyngeal critical closing pressure (Pcrit) and site of airway collapse were assessed during head flexion, extension and rotation in individuals undergoing propofol anesthesia.


METHODS
Operating theatre of major teaching hospital.


METHODS
Fifteen healthy volunteers (8 male), including 7 who were undergoing surgery unrelated to the head or neck.


RESULTS
Applied upper airway pressure was progressively decreased to induce variable degrees of inspiratory flow limitation and to define Pcrit. Upper airway and oesophageal pressure transducers identified the site of collapse. Genioglossus muscle activity (EMGgg) was assessed using intramuscular fine wire electrodes inserted percutaneously. Data from 3 subjects were excluded from analysis due to persistent EMGgg. In the neutral posture Pcrit was -0.4 +/- 4.4 cm H2O and collapsed most frequently in the velopharyngeal region. Relative to neutral, Pcrit increased to 3.7 +/- 2.9 cm H2O (P < 0.01) and decreased to -9.4 +/- 3.8 cm H2O (P < 0.01) when the head was flexed and extended, respectively but was unchanged by rotation (-2.6 +/- 3.3 cm H2O; n = 10; P = 0.44). The site of collapse varied, in no consistent pattern, with change in head posture in 5 subjects.


CONCLUSIONS
Head posture has a marked effect on the collapsibility and site of collapse of the passive upper airway (measured by EMGgg) indicating that controlling head posture during sleep or recovery from anesthesia may alter the propensity for airway obstruction. Further, manipulating head posture during propofol sedation may assist with identification of pharyngeal regions vulnerable to collapse during sleep and may be useful for guiding surgical intervention.
West Australian Sleep Disorders Research Institute, Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia. Jennifer.Walsh@health.wa.gov.au
Jennifer H
JH
Walsh
Kathleen J
KJ
Maddison
Peter R
PR
Platt
David R
DR
Hillman
Peter R
PR
Eastwood
D000328:Adult; D000402:Airway Obstruction / Q000503:physiopathology*; D000768:Anesthesia, General; D004576:Electromyography; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007013:Hypopharynx / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009305:Nasopharynx / Q000503:physiopathology; D009960:Oropharynx / Q000503:physiopathology; D010609:Pharyngeal Muscles / Q000503:physiopathology; D012890:Sleep / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology; D055815:Young Adult