Patients
The study enrolled patients scheduled for EGD under sedation at the outpatient department of the first affiliated hospital of USTC between April 2020 and December 2020. The indications of upper endoscopies were gastroesophageal reflux, abdominal pain, gastrointestinal bleeding and anemia. All subjects conformed to the following inclusion criteria: male or female patients; age between 65 and 80 years; American Society of Anesthesiology (ASA) score I–II physical status; and ability to fill out a survey form and give informed consent. Exclusion criteria were: psychiatric and neurological history; severe cardiovascular or pulmonary diseases; body mass index (BMI) > 30 kg/m2; sleep apnea; impaired kidney or liver function; long-time opioid or antipsychotic medication history; acute upper gastrointestinal bleeding; allergic to propofol or the emulsifier content; and an expected upper endoscopy duration more than 30 min. This protocol was approved by the Medical Ethics Committee of the First Affiliated Hospital of University of Science and Technology of China (USTC). All patients gave their written informed consent. The study was conducted according to the Declaration of Helsinki.
All the investigators and the anaesthetists participated in standardized training for the operation of the innovative endoscopic oropharyngeal airway, including the mechanism of action for its use in EGD, and management of the adverse events. Based on a random number table generated by a computer, eligible patients were randomized in a 1:1 ratio to two groups with block sizes of 2: mouthpiece group or airway group. The patients were unaware of group assignment.The randomization sequence was kept in sealed opaque, identical envelopes. The envelopes were opened just before preparation of the mouthpiece or airway. Dosing of anesthetic medications was at the discretion of the anaesthetists. Outcome assessment was performed by the investigator. One of the investigators placed the device and managed airway.
Sedation methods
All patients were fasted for 8 h before the upper endoscopy. 10 ml of dyclonine glue was taken orally 30 min before EGD. The venous channel was established in the upper limb. The subjects were placed in the left lateral decubitus position. Electrocardiography, pulse oxygen saturation, heart rate and blood pressure (cuff placed on the left upper arm) were continuously monitored during the procedure. A conventional mouthpiece was used in mouthpiece group for endoscope, while placed an innovative endoscopic oropharyngeal airway commercialized as Endoscopy Protector in airway group (45–70 kg, medium size; 60–100 kg, large size) (Dami Medical Technology Co.,Ltd, Hefei, China.). The nasal catheter was placed in the two groups before the venous anesthesia and both groups were given oxygen at the same rate of 5 L/min for 1 min.
Patients in two groups were given intravenous 1.0% propofol (batch number: 1912296; Fresenius Kabi, Graz, Austria) at an induction dose of 1.5 mg/kg over a 1 min period followed by a maintenance dose at 2–5 mg/kg/h [2]. EGD was performed after the patient’s consciousness disappeared and the eyelash reflex disappeared. After the nasal oxygen tube was placed from nostril to the mouthpiece, the subjects in mouthpiece group received the gastroscope. In the airway group, after the novel oropharyngeal airway being soaked in normal saline for 10 s for the super-slip material on the surface being activated, it was inserted into the transparent mouthpiece (Fig. 3). And the nasal oxygen tube was placed from nostril to the airway channel of the novel oropharyngeal airway and the upper endoscopy began (Fig. 3). All the procedures were performed by the same endoscopist. Spontaneous respiration was maintained during the procedure.
Monitoring and management of adverse events
All patients undergoing EGD under sedation were evaluated according to the Ramsay Sedation Scale (RSS) [12], which was maintained at > 4 during upper endoscopy. If a patient showed be in discomfort or exhibited restlessness, an additional 10 mg of propofol was given as a bolus injection and the maintenance infusion rate was increased by 1 mg/kg/h. If an adverse event was appeared, the dose of maintenance sedation was decreased. Under the supply of 100% O2 5 L/min via nasal cannula, when the patient’s blood oxygen saturation was less than 90%, the mandible was lift up to maintain upper airway patency and the oxygen flow was enhanced. When the patient’s blood oxygen saturation was less than < 85%, suspend endoscopy and quickly pulled out gastroscope to hold up the oxygen mask to assist breathing. Tracheal intubation for mechanical ventilation was performed if necessary. When the sound of airflow through secretions were found or choke occurred during the procedure, sputum suction were recommended for immediate implementation. The effective suction secretion and reflux was defined as that airway was patency and pulse oxygen saturation could be promoted after suction. Subclinical respiratory depression: if pulse oxygen saturation of 90–94% [13]. Hypoxemia: desaturation events were defined as mild (if pulse oxygen saturation of 85–89%) and moderate (if pulse oxygen saturation < 85%) [14, 15]. Bradycardia: if the heart rate is less than 50 bpm during EGD, a 0.5 mg dose of atropine were given intravenously. Hypotension: if the systolic blood pressure drops more than 20% of the baseline or less than 90 mmHg, 20 μg dose of phenylephrine was given.
Assessments
Heart rate (HR), mean arterial pressure (MAP) and pulse oxygen saturation of patients were recorded before anesthesia, during EGD and after EGD. The recorded pulse oxygen saturation during EGD was minimum value in the period. Endoscopy entry time, first successful entry rate, duration of endoscopy, the dose of sedation and recovery time were recorded. The incidence of emergency management and adverse reactions were recorded. Airway interventions during procedure (including lifting the mandible, hyperbaric oxygen supply, pause Endoscopy, assisted ventilation and gastroscope withdraw) were recorded.
The novel oropharyngeal airway was taken away after the gastroscope was pulled out from esophagus in airway group. The patient was transferred to the PACU (post-anesthesia care unit) after the procedure was completed. The transparent mouthpiece and conventional mouthpiece were also taken out after the patients became conscious. The subjects were followed up 1 h later, receiving an Aldrete score after anesthesia with a score of 9 or higher [16], and may be discharged with the company of relatives and friends. The satisfaction of the physician and patient were assessed using a 10-point scale as follows: poor, 1–4; fair, 5–7; good, 8–10.
The primary outcome was the incidence of the minimum pulse oxygen saturation < 90% and minimum pulse oxygen saturation. The secondary outcomes were endoscopy entry time, first successful entry rate, duration of upper endoscopy, recovery time, sedation dose (propofol) and the incidences of adverse reactions. The adverse reactions were tongue retraction, cough, body movements, hiccups, reflux and aspiration. The recovery time includes the awakening time and the time from awakening to leave. The awakening time is defined as the time from the end of the procedure to the acquisition of an Aldrete score of 9 or higher.
Sample size calculation
A previous study showed that the minimum pulse oxygen saturation < 90% in aged patients using nasal catheter and a conventional mouthpiece undergoing upper endoscopy under sedation was 15.9% and a reduction to 6.2% respectively using endoscopic mask [7]. Based on our pilot study, we assumed the 14.0% incidence of the minimum pulse oxygen saturation < 90% in aged patients using a conventional mouthpiece and a clinically important reduction to 5.0% happened with using the innovative endoscopic oropharyngeal airway. The required sample size was calculated to be 166 patients per group (α = 0.05 and β = 0.2). To account for potential dropouts, 366 patients were recruited. Analysis was conducted on an intention-to-treat basis.
Statistical analysis
Data were presented as means ± standard deviation for normally distributed data and median and range for skewed data. Absolute numbers were presented as percentages of participants. Depending on the distribution of the data, continuous variables were compared using a 2-tailed Student t test or Mann–Whitney U test. Categorical variables were compared using the Pearson chi-square test or Fisher exact test. A P < 0.05 was considered statistically significant. For statistical analysis, we used SPSS version 24.0 (SPSS Inc., Chicago, IL).