Hysteroscopy is used to examine and treat uterine diseases. Because of severe pain due to uterine distention and cervical dilatation, deep sedation usually be provided during this procedure. Respiratory depression and upper airway obstruction are main respiratory complications during deep sedation. Face mask and nasopharyngeal airway are main airway management during deep sedation. Oxygen reserve index is a non-invasive parameter, it reflects the moderate hyperoxia statues. In this study, investigators compare the effect of face mask and nasopharyngeal airway management on oxygenation during deep sedation in participants undergoing hysteroscopy. Investigators also investigate whether oxygen reserve index monitoring reduce the incidence of hypoxemia.

Randomization:

Participants are divided into four groups: face mask airway management without oxygen reserve index (ORi) monitoring group (FM-ORi group), face mask airway management with ORi monitoring group (FM+ORi group), nasopharyngeal tube airway management without ORi monitoring group (NT-ORi group), nasopharyngeal tube with ORi monitoring group (NT+ORi group).

Deep sedation process:

Participants fasting solid and liquid for 8 and 4 hours respectively. Electrocardiogram (ECG), oxygen saturation (SpO2), blood pressure (BP) and bispectral index (BIS) were monitored. Sufentanil 5 μg injected for 30 seconds, followed by target-control infusion of propofol (plasma target concentration 3-6 ug/ml) to maintain BIS between 50-70. Criteria for deep sedation: participants have purposeful response after repeated and/or painful stimulation, there is minimal effect on hemodynamic stability.

Airway management:

In FM-ORi and FM+ORi group, participants spontaneous inhaled oxygen through face mask at a flow rate of 5 L/min. in FM-ORi group, assist ventilation through face mask was performed when SpO2 dropped to 95%, it lasted for another 10 seconds when SpO2 restored to 100%. In FM+ORi group, assist ventilation through face mask was performed when ORi dropped to 0.1, it lasted for another 10 seconds when ORi restored to 0.1.

In NT-ORi and NT+ORi group, participants spontaneous inhaled oxygen through face mask before induction and through nasopharyngeal tube after consciousness disappear at a flow rate of 5 L/min. in NT-ORi group, assist ventilation through face mask was performed when SpO2 dropped to 95%, it lasted for another 10 seconds when SpO2 restored to 100%. In NT+ORi group, assist ventilation through face mask was performed when ORi dropped to 0.1, it lasted for another 10 seconds when ORI restored to 0.1.

Inclusion Criteria:

• Female, 18-60 years old
• Scheduled for hysteroscopy
• Predict operation duration more than 10 minutes

Exclusion Criteria:

• Participants refuse
• Predict the presence of difficult airway
• Combined with obstructive sleep apnea syndrome
• Combined with upper respiratory tract infection, and/or pulmonary inflammation
• Combined with chronic obstructive pulmonary disease
• Combined with asthma
• Body mass index (BMI) >30 kg/m2
• Coagulation dysfunction, and/or undergo anticoagulant therapy
• Nasal deformity
• Pregnancy, positive urine pregnancy test

Investigators have no plan to make individual participant data available to other researchers