The effects of hormonal status on upper airway patency in normal female subjects during propofol anesthesia

Study ObjectiveTo determine the mechanical upper airway properties and compensatory neuromuscular responses to obstruction during propofol anesthesia in the follicular and luteal phases of the menstrual cycle.DesignProspective, randomized study.SettingUniversity-affiliated hospital.Subjects12 premenopausal female volunteers for studies of upper airway collapse throughout their menstrual cycle during the follicular phase (6 -10 days) and mid-late luteal phase (20 - 24 days).MeasurementsThe level of propofol anesthesia (1.5 - 2.0 μg/mL) required to suppress arousal responses was determined by Observer's Assessment of Alertness/Sedation scoring (level 2) and confirmed by bispectral index monitoring. Pressure-flow relationships were constructed to evaluate collapsibility (PCRIT) and up-stream resistance (RUS) during acute [Passive; hypotonic electromyography (EMG)] and sustained (Active; elevated EMG) changes in nasal mask pressure. The difference between passive PCRIT and active PCRIT (ΔPCRIT A-P) represented the magnitude of the compensatory response to obstruction.Main ResultsPassive PCRIT was significantly higher in the mid-late luteal phase (-4.7 cm H2O) than in the follicular phase (-6.2 cmH2O; P < 0.05). Active PCRIT significantly decreased compared with passive PCRIT in the follicular phase (-10.1 cm H2O) and in the mid-late luteal phase (-7.7 cm H2O) and (P < 0.05). No significant difference was noted in ΔPCRIT between the follicular (3.9 ± 2.9 cm H2O) and mid-late luteal phases (3.0 ± 2.6 cm H2O). No differences were seen in RUS between the menstrual phases for either the passive (P = 0.8) or active (P = 0.75) states.ConclusionsMenstrual phase has an effect on anatomical alterations (mechanical properties) in the hypotonic upper airway during propofol anesthesia.