Table of Contents  
Year : 2017  |  Volume : 10  |  Issue : 1  |  Page : 109-116

Nasopharyngeal airway for oxygenation and sevoflurane inhalation during endoscopic retrograde cholangiopancreatography in patients with obstructive sleep apnea

Department of Anesthesia, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Date of Web Publication3-Aug-2018

Correspondence Address:
Heba B El-Serwi
7 El Shahid Ahmed Wasfi St., 11341 Cairo
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1687-7934.238484

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Objectives The aim of this study was to evaluate applicability of nasopharyngeal airway (NPA) for the maintenance of patients’ oxygenation during sevoflurane inhalational anesthesia through NPA against propofol infusion and traditional endotracheal intubation (ETT).
Patients and methods The study included 111 patients with obstructive sleep apnea (OSA). Risk of OSA was evaluated preoperatively using the STOP-BANG Questionnaire. Patients were randomly allocated into three groups: group E received propofol infusion (50–150 μg/kg/min) with atracurium (0.3 mg/kg), group S received sevoflurane inhalation (1 MAC) through NPA, and group P was maintained on propofol infusion (50–150 μg/kg/min). The frequency and severity of hypoxemic attacks and the requirement for ETT in groups S and P were compared.
Results Sixty-four patients (57.7%) had mild, whereas and 47 patients (42.3%) had an iintermediate OSA grade on STOP-BANG score. At the end of endoscopic retrograde cholangiopancreatography, heart rate, mean arterial pressure, and mean PSaO2 measures were found significantly lower in all patients compared with baseline estimates. Concentration of PSaO2 was significantly lower in group P compared with groups E and S. The frequency of hypoxemic attacks was nonsignificantly higher with NPA compared with ETT and only five patients required ETT. The frequency of procedural sedation-related adverse events was nonsignificantly lower with NPA compared with ETT (27 vs. 32.4%). The frequency till full recovery was significantly longer in group E compared with groups S and P, with a significant difference in favor of group S. Patients’ satisfaction scorings were significantly higher in groups S and P compared with group E. Endoscopist satisfaction scorings were significantly higher in groups S and E compared with group P.
Conclusion NPA could be applied for the oxygenation of patients undergoing endoscopic retrograde cholangiopancreatography, even on those having OSA with an acceptable frequency of hypoxic attacks and conversion rate to ETT. Sevoflurane sedation was an advantageous alternative to propofol sedation for an early, easy recovery with less adverse events.

Keywords: endoscopic retrograde cholangiopancreatography, nasopharyngeal airway, propofol, sedation, sevoflurane

How to cite this article:
Said AM, El-Serwi HB. Nasopharyngeal airway for oxygenation and sevoflurane inhalation during endoscopic retrograde cholangiopancreatography in patients with obstructive sleep apnea. Ain-Shams J Anaesthesiol 2017;10:109-16

How to cite this URL:
Said AM, El-Serwi HB. Nasopharyngeal airway for oxygenation and sevoflurane inhalation during endoscopic retrograde cholangiopancreatography in patients with obstructive sleep apnea. Ain-Shams J Anaesthesiol [serial online] 2017 [cited 2023 Dec 5];10:109-16. Available from:

  Introduction Top

Gastrointestinal endoscopies are invasive and unpleasant procedures that are increasingly being used worldwide. Endoscopic retrograde cholangiopancreatography (ERCP) can be used not only as a diagnostic procedure but also as a treatment in most biliary tract and pancreatic diseases that include removal of common bile duct stones, stenting of biliary stricture and resolution of pancreatic duct disruption. Over the last decade, the number of ERCP procedures carried out worldwide has increased significantly [1],[2].

The importance of high-quality endoscopic procedures, increasing patient awareness and the expectation of painless examination have increased the need for procedural sedation. For the completion of the ERCP procedure, there are two basic choices of anesthesia available: sedation and general anesthesia [3].

According to the American Society of Anesthesiologists (ASA), sedation is defined as a continuum of progressive impairment in consciousness ranging from minimal to moderate sedation, deep sedation and general anesthesia [4]. The goals of sedation are to achieve a balance between the benefits of sedation against potentially preventable risks. Sedation reduces pain, discomfort, and stress, and can produce amnesia in patients undergoing unpleasant and prolonged procedures such as ERCP. In contrast, there are adverse effects of sedation that must be avoided such as patient aggravation, deep unarousable state, absence of purposeful response to physical and verbal stimulation, loss of protective airways reflexes, inability to maintain patent airway, hypoxemia/hypercarbia, and cardiovascular instability such as arrhythmia or hypotension [5].

Suitable drugs and their dosage for sedation have been debated, and a variety of different drugs have been used around the world; consequently, the search for an appropriate sedation regimen continues [6]. Moreover, the anesthesia community is still divided as to the appropriate airway management in patients undergoing ERCP. Increasingly, gastroenterologists are comfortable with deep sedation normally using propofol without endotracheal intubation (ETT) [7].

However, propofol is primarily an anesthetic agent; however, its use in a sedative capacity has resulted in the extensive off-label administration of this drug by gastroenterologists and other nonanesthesia personnel. This has created controversy and enabled the gastroenterology community to gather evidence and campaign for US Food and Drug Administration approval to administer propofol to patients undergoing ERCP and other endoscopic procedures. Moreover, there are no comprehensive reviews addressing the various pros and cons of an unintubated airway management [8],[9].

Thus, the current study aimed to evaluate the applicability of nasopharyngeal airway (NPA) for maintenance of patients’ oxygenation during sevoflurane inhalational anesthesia through the airway against propofol infusion compared with traditional ETT as a gold-standard procedure.

  Patients and methods Top

The current prospective comparative study was conducted at the Anesthesia Department, Ain Shams University Hospital and some private hospitals between January 2012 and October 2014. After approval of the study protocol by the Local Ethical Committee and obtaining fully written informedconsent from patients, all patients assigned for ERCP, either diagnostic or therapeutic were enrolled for clinical evaluation and grading of their obstructive sleep apnea (OSA), if present, using the STOP-BANG Sleep Apnea Questionnaire [10] as shown in [Table 1].
Table 1 STOP-BANG Sleep Apnea Questionnaire [10]

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Enrolment criteria included the presence of OSA of low-to-intermediate risk on the STOP-BANG Questionnaire, ASA grade I–II, assigned for ERCP and fulfilling preprocedure requirements, free of any contraindication for inhalational anesthesia and fulfilling surgical requirement if a shift to surgical interference is required.

All enrolled patients underwent detailed history taking including demographic data for age, sex, body weight, height and calculation of BMI defined as weight in kilograms divided by the square of the height in meters [11]. Patients were graded according to the international classification of BMI as follows: underweight (BMI<18.5 kg/m2); normal weight (BMI=18.5–24.99 kg/m2); overweight (BMI=25–29.99 kg/m2); obese (BMI>30 kg/m2) [12],[13].

Patients were randomly divided into three groups using sealed envelopes chosen by patient: group E had ETT and groups P and S had NPA intubation.

Anesthetic procedure

Before induction, patients were preoxygenated using 100% oxygen by breathing into tightly held face mask of appropriate size to achieve the highest possible preinduction blood oxygen saturation. Baseline arterial blood pressures, heart rate (HR), respiratory rate and arterial O2 saturation (PSaO2) were recorded non-invasively and monitored continuously throughout the procedure time. Venous access was secured on the non-dependent arm, usually the right arm as the procedure will be conducted while patients were in the left-lateral or semi-prone position.

All patients were induced in the ssupine position. For all patients, anesthesia was induced using propofol infusionat a dose of 1.5–2 μg/kg and fentanyl at a dose of 1 μg/kg. Then, anesthesia was maintained in group P using propofol infusion at a dose of 50–150 μg/kg/min. For group S, anesthesia was maintained with sevoflurane inhalation (1 MAC) through the NPA. For both groups, patients were allowed for spontaneous ventilation through NPA of appropriate size connected to a closed circuit to maintain arterial O2 saturation (PSaO2) of at least 95%. For group E, ETT was facilitated using atracurium in at a dose of 0.5 mg/kg and propofol infusion was maintained at rate of 50–150 μg/kg/min and incremental dose of atracurium (0.3 mg/kg).

Once adequate jaw relaxation was achieved, topical lidocaine 10% was sprayed on the oropharynx, an endoscopy probe was inserted and patients were transferred to the semi-prone or left-lateral position according to the endoscopist’s preference. Patients were monitored non-invasively for arterial blood pressures, HR, respiratory rate and PSaO2.

Outcome measures

Primary outcomes involved the following:

  1. The frequency of episodes of hypoxemia defined as a pulse oximetry less than 90% for any duration, and hypopnea/apnea defined as less than 6 breaths/min based on capnography, which may have occurred with or without hypoxemia.
  2. The frequency of the need for ETT.
  3. The frequency of hypotensive attacks, defined as a systolic blood pressure of less than 90 mmHg or a decrease of greater than 25% from baseline.

Secondary outcome involved the following:

  1. Procedural duration and duration till full recovery.
  2. Frequency of postprocedural complications related to anesthesia.
  3. Patients and endoscopists’ satisfaction scoring using the four-grade verbal analogue scale: unsatisfactory, good, satisfactory and very satisfactory.

Statistical analysis

The sample power was calculated according to Kraemer and Theimann [14] using their proposed figure, which showed that the sample size for 60% power would require an N of 31 per group and 80% power would require an N of 51 per group. This hypothesis was documented by Murphy and Myors [15]. Considering that patients assigned for ERCP and had OSA are not frequent, from a standard nomogram, a sample size of 31 patient per group was determined to be sufficient to yield the trial greater than 60% power to detect a difference at the 5% significance level. Obtained data were presented as mean±SD, ranges, numbers and ratios. Results were analyzed using the paired t-test for within group variability, the Wilcoxon; ranked test for unrelated data (Z-test) the χ2 −test paired t-test for variability between groups. Statistical analysis was conducted using SPSS (SPSS, Inc., Chicago, IL, USA) (version 15, 2006) for Windows statistical package. P value less than 0.05 was considered statistically significant.

  Results Top

The study included 111 patients (37 patients/group): 78 male and 33 female, with a mean age of 46.3±14.6 (range: 25–75) years. The majority of the patients were obese, with a mean BMI of 33.5±3.2 kg/m2 (range: 23.7–41.2 kg/m2). Sixty-four patients (57.7%) had mild OSA and 47 patients (42.3%) had a moderate grade on the STOP-BANG score. Seventy-six (68.5%) and 35 patients (31.5%) were of ASA grades I and II, respectively. Twenty-two patients were assigned for therapeutic ERCP and 89 for diagnostic ERCP. There was a non-significant (P>0.05) difference between the studied groups with regard to enrolment data as shown in [Table 2].
Table 2 Patients’ enrolment data

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Baseline hemodynamic data showed a nonsignificant (P>0.05) difference between the studied groups. At the end of ERCP, all patients showed a significant (P<0.05) decrease in HR compared with their baseline HR. However, patients of group S showed a significantly (P<0.05) higher HR at the end of the procedure compared with patients of group P ([Figure 1]).
Figure 1 Mean heart rate (HR) of the sstudied groups estimated at the end of endoscopic retrograde cholangiopancreatography (ERCP) compared with baseline measures. +Significant vs. baseline; *Significant vs. group E.

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Systolic, diastolic, and mean arterial pressure measures of all studied patients were significantly (P<0.05) decreased at the end of ERCP compared with baseline measures. Despite this decrease, the difference between the three groups was nonsignificant (P>0.05) ([Figure 2]). Hypotension was recorded in seven patients maintained on NPA (9.5%); two in group S and five in group P, as against six patients in group E with a nonsignificantly (P>0.05) higher frequency among those maintained on NPA. The frequency of hypotensive attacks was significantly (P<0.05) lower in group S compared with groups E and P and was nonsignificantly (P>0.05) lower in group P compared with group E ([Table 3]).
Figure 2 Mean mean arterial pressure (MAP) of the studied groups estimated at the end of endoscopic retrograde cholangiopancreatography (ERCP) compared with baseline measures. +Significant vs. baseline.

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Table 3 Hemodynamic data of the studied groups at the end of procedure compared with baseline data

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The mean baseline PSaO2 showed nonsignificant (P>0.05) difference among the studied patients. However, the mean PSaO2 estimated at the end of the procedure was significantly (P<0.05) lower in all studied patients compared with their baseline concentration. The concentration estimated in patients of group P was significantly (P<0.05) lower compared with that in groups E and S with nonsignificantly (P>0.05) lower concentration in patients of group S compared with group E ([Figure 3]).
Figure 3 Mean arterial blood oxygen saturation of the studied patients estimated at the end of endoscopic retrograde cholangiopancreatography (ERCP) compared with baseline measures. +Significant versus baseline; *Significant vs. group P.

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Hypoxemic attacks, defined as PSaO2 less than 90%, were encountered in 10 patients (13.5%) maintained on NPA and showed a nonsignificantly (P>0.05) higher frequency compared with the frequency reported in group E (10.8%). Moreover, the frequency of patients had PSaO2 in the range of 90–95% was also nonsignificantly (P>0.05) higher in patients maintained on NPA compared with intubated patients (20.3 vs. 13.5%) ([Table 4]).
Table 4 PSaO2 concentration of the studied groups estimated at the end of procedure compared with baseline data

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Awareness during the procedure was reported in seven patients; two intubated and five in NPA patients with nonsignificantly (P>0.05) higher frequency among those maintained on NPA and a nonsignificantly (P>0.05) higher frequency in group S compared with group P. Five patients required ETT; two in group S and three in group P, with a nonsignificant (P>0.05) difference in favor of group S. Collectively, sedoanesthetic-related adverse events were encountered in 20 patients at for a frequency of 27% among those maintained on NPA, whereas they occurred in 12 intubated patients for at a frequency of 32.4% with nonsignificantly (P>0.05) lower frequency in patients maintained on NPA.

The duration of the procedure of ERCP showed a non-significant (P>0.05) difference between the studied groups, whereas the duration till full recovery was significantly (P<0.05) longer in group E compared with groups S and P, with a significantly (P<0.05) shorter recovery duration in group S compared with group P ([Figure 4]).
Figure 4 Mean±SD recovery time of the studied groups. +Significant difference versus group E; *Significant difference versus group P.

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Patients’ satisfaction scorings were significantly (P<0.05) higher in groups S and P compared with group E with a nonsignificantly (P>0.05) higher scoring among patients of group S compared with group P ([Figure 5]).
Figure 5 Patients distribution according to the extent of satisfaction with the applied sedation procedure. +Significant vs. group E.

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Endoscopists found the procedure applied in group E to be the most satisfactory, followed by that provided in group S, and lastly group P. The stisfaction scoring of endoscopists for procedural sedation was significantly (P<0.05) higher in groups E and S compared with group P, with a non-significantly (P>0.05) higher scoring for group E compared with group S ([Table 5] and [Figure 6]).
Table 5 Satisfaction scoring by the applied anesthetic procedure

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Figure 6 Endoscopist satisfaction scoring by the applied sedation procedure per patient. +Significant vs. group P.

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  Discussion Top

Determination of OSA severity relied on the preoperative STOP-BANG questionnaire, which defined 64 patients (57.7%) with mild OSA and 47 patients (42.3%) with moderate OSA grades; thus, the applied could be used to differentiate patients preoperatively. This opinion was supported by Evans et al., [16] who found the STOP-Bang Questionnaire is easy to implement in a preoperative clinical setting, despite not being useful in identifying patients at risk for right-sided heart dysfunction. Also, Pavarangkul et al. [17] found that the STOP-BANG questionnaire is a good screening, tool but may need some adjustment for the Asian population. Moreover, Dimitrov and Macavei [18] documented that the ASA checklist, Berlin Questionnaire and STOP-Bang Questionnaire may be able to risk stratify patients for peri- and postoperative complications.

Collectively, anesthetic-related adverse events were encountered in 32 patients at a frequency of 27 against 32.4% among those maintained on NPA and ETT, respectively. Five out of 74 patients in NPA groups required ETT at a frequency of 6.8%. These findings indicated the feasibility and safety of maintaining patients on NPA during ERCP, without the need for tracheal intubation with its sequlae of coughing on the tube, a shortened recovery time, post-anesthetic throat problems and spared extubation time. Procedural sedation through NPA provided patient and endoscopist satisfaction rates approaching those obtained with ETT.

In line with the reported success of applied sedo-anesthetic procedures, Goudra et al. [19] retrospectively studied 653 patients who underwent outpatient ERCP with natural airway and found only 45 patients to have transient de-saturation below 95% without any residual sequlae and concluded that optimal oxygenation and airway patency was maintained with a high degree of success using simple airway maneuvers or conduit devices (nasal/oral trumpet) with oxygen supplementation in all patients.

Döbrönte et al. [20] reported an oxygen saturation of less than 90% in 19.1% of all patients who underwent endoscopy, and that it occurred most often during ERCP (31.2%); procedure-related risk factors were long procedure duration, premedication with pethidine (31.3%), and combined sedoanalgesia with pethidine and midazolam (34.38%); patient-related risk factors were age over 60 years, obesity, consumption of hypnotics or sedatives, severe cardiopulmonary state and ASA III and IV grades.

Bannert et al. [21] prospectively assessed the safety of anesthesia-directed deep sedation (ADDS) in nonintubated patients compared with general endotracheal anesthesia during an ERCP and reported a conversion rate of 3.7% (16/393) 25% of the converted ADDS cases (4/16) were ASA IV and intraprocedure events occurred in 35.6% of general endotracheal anesthesia and 25.7% of ADDS cases, without significant complications.

Sethi et al. [22] retrospectively found that monitored anesthesia care without ETT is a safe and efficacious sedation approach for most patients undergoing single-balloon enteroscopy; iintraprocedure sedation-related adverse events occurred in 17% of cases and most were transient hypotension requiring pharmacologic intervention in 11.8% of procedures, but were more frequent in longer procedures.

Propofol sedation with NPA oxygenation provided a satisfactory outcome that was comparable to that with propofol sedation with ETT oxygenation, indicating the feasibility and safety of such a sedation protocol. This outcome coincided with that previously reported in the literature that propofol is a safe and effective sedative agent for upper endoscopy [23],[24],[25] and for ERCP [26],[27],[28].

However, the results obtained showed superiority of sedo-anesthesia using sevoflurane inhalational anesthesia through NPA with regard to hemodynamic stability manifested as a low frequency of hypotensive attacks with a significant difference against patients of group E (5.4 vs. 16.2%) and group P (5.4 vs. 13.5%). Moreover, the frequency of oxygen saturation of less than 90% and the need for ETT were nonsignificantly lower with sevoflurane compared with propofol in patients maintained on NPA.

These findings indicated the effectiveness and safety of sevoflurane inhalation through NPA as procedural sedation during ERCP. In line with these findings, Ye et al. [29] documented that propofol is widely used for the sedation of patients who underwent lower gastrointestinal endoscopy, but it may cause some allergic reaction and inhaled sevoflurane may provide a satisfactory and safe alternative for adult outpatients’ endoscopy. Also, Syaed El Ahl [30] documented that for geriatric colonoscopy, sevoflurane-based sedation techniques may be a safe and effective alternative to propofol which is associated with more frequent apnea attacks, need for airway intervention and the need for general anesthesia.

Unfortunately, search of the literature yielded no similar trials for inhalational sedation with sevoflurane through NPA during ERCP; however, the reported superiority over propofol sedation was in line with that reported previously for other applications of procedural sedation, irrespective of indication and patients’ conditions. Hellström et al. [31] found that sevoflurane sedation after cardiac surgery leads to shorter wake-up times and quicker cooperation compared with propofol, with no differences in ICU stay, adverse memories or recovery events. Nishiyama [32] reported that propofol might induce bronchoconstriction with a higher incidence in allergic patients than in non-allergic patients and also in comparison with sevoflurane. Choi et al. [33] found that sevoflurane anesthesia during interventional neuroradiology was associated with faster recovery, less patient movement during the procedure and a more stable hemodynamic response compared with propofol. Marcos-Vidal et al. [34] documented that postoperative sedation with sevoflurane after cardiac surgery with cardiopulmonary bypass is a valid alternative to propofol; it does not increase the number of side effects related to kidney damage in patients with no prior renal disease and reduced troponin T levels.

The results obtained could be considered as a step for the application of NPA for the oxygenation of patients undergoing ERCP, even in those who had OSA, with an acceptable frequency of hypoxic attacks and conversion rate to ETT. Sevoflurane sedation was advantageous as an alternative to propofol sedation during ERCP for earlier and easier recovery with less sedation-related adverse events. Wider studies were advocated the documentation of these results in patients with advanced ASA grades.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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