|Year : 2022 | Volume
| Issue : 1 | Page : 30-35
Comparison of oxygen delivery methods during monitored anaesthesia care for flexible endoscopy procedures
Shivangi Harish Agrawal1, Birva Khara2
1 Department of Anaesthesia, SMIMER Hospital and Medical College, Surat, Gujarat, India
2 Shree Krishna Hospital, Anand, Gujarat, India
|Date of Submission||24-Oct-2021|
|Date of Acceptance||13-Mar-2022|
|Date of Web Publication||31-Mar-2022|
Dr. Shivangi Harish Agrawal
11, Akshardham Society, Gangeshwar Mahadev Road, Adajan, Surat - 395 009, Gujarat
Source of Support: None, Conflict of Interest: None
Introduction: Endoscopic procedures are usually performed under monitored anaesthesia care. Hypoxia could occur due to the sedative effects of drugs used during flexible endoscopic procedures and sharing of airway between endoscopist and anaesthesiologist. Administration of oxygen could reduce the incidence of hypoxia. Aims and Objectives: We aimed to study whether delivery of oxygen through nasal prongs or through a T-piece without an after-burner connected to a nasopharyngeal airway could reduce the incidence of hypoxia during monitored anaesthesia care for flexible endoscopic procedures. While our primary objective was to compare the incidence of hypoxia (oxygen saturation [SpO2] < 90% lasting for at least 15 s), our secondary objectives were to compare the level of sedation and incidence of adverse events. Patients and Methods: Sixty six patients (33 in each group) aged between 18 and 80 years were randomly allocated to one of two groups to receive oxygen through nasal prongs or through a T-piece without an after-burner connected to a nasopharyngeal airway. Drug requirement, SpO2 and adverse events were monitored pre-procedure and every 5 min thereafter till the end of the procedure. Results: There was no statistically significant difference in the mean SpO2 (P > 0.05), but the incidence of hypoxia was less in patients receiving oxygen through nasal prongs as compared to patients receiving oxygen through a T-piece without an after-burner connected to a nasopharyngeal airway (P < 0.05). Adverse events were found to be comparable between two groups. Conclusion: During flexible endoscopy under monitored anaesthesia care, oxygen delivery through nasal prongs results in a lower incidence of hypoxia as compared to oxygen delivery through a T-piece without an after-burner connected to a nasopharyngeal airway.
Keywords: Flexible endoscopic procedure, hypoxia, monitored anaesthesia care, nasal prongs, T-piece without after-burner connected to nasopharyngeal airway
|How to cite this article:|
Agrawal SH, Khara B. Comparison of oxygen delivery methods during monitored anaesthesia care for flexible endoscopy procedures. Airway 2022;5:30-5
|How to cite this URL:|
Agrawal SH, Khara B. Comparison of oxygen delivery methods during monitored anaesthesia care for flexible endoscopy procedures. Airway [serial online] 2022 [cited 2022 May 20];5:30-5. Available from: https://www.arwy.org/text.asp?2022/5/1/30/342369
| Introduction|| |
During upper gastrointestinal endoscopy, a flexible endoscope is passed through the mouth and throat into the oesophagus and stomach allowing examination of the upper gastrointestinal tract. Similarly, an endoscope can be passed retrograde into the large intestine through the rectum for the diagnosis of conditions affecting the lower digestive tract. Flexible endoscopic procedures have now become commonplace.
In this modern era, flexible endoscopy under monitored anaesthesia care is preferred by patients as it increases patient comfort during flexible endoscopy and follow-up examinations. Although endoscopic procedures are semi-invasive and safe, they have several disadvantages such as nausea, vomiting, bleeding and anxiety. Adequate sedation and analgesia are requirements of diagnostic and therapeutic procedures. This is a challenging task both for the anaesthesiologist and the gastroenterologist as the main concern is sharing of the airway with relatively simple monitoring and rescue equipment. The associated risks are even higher than for general anaesthesia administered in the operating room.
Monitored anaesthesia care is the term used to describe specific anaesthesia services for diagnostic or therapeutic procedures performed under local anaesthesia along with sedation and analgesia. Monitored anaesthesia care involves three basic components – safe conscious sedation, measures to alleviate anxiety and effective pain control. Monitored anaesthesia care leads to less physiological disturbances and more rapid recovery than general anaesthesia. It is suitable for daycare procedures. Delivery of monitored anaesthesia care requires skill and expertise to rescue an airway or convert to general anaesthesia if required. Monitored anaesthesia care includes support of vital functions; management of possible intraoperative derangements such as hypoxia, body movements, coughing and bleeding and provision of appropriate counselling. Sedation ranges from mild sedation (anxiolysis) to moderate sedation (conscious sedation) to deep sedation (where the patient can be aroused only by painful stimuli).
Assessment of depth of sedation is important as it helps in titrating drug administration to prevent both awareness and excessive anaesthetic depth. Conscious sedation is a term representing purposeful responsiveness to visual or auditory stimulation, with adequate spontaneous respiration and maintenance of airway patency and minimal changes in cardiovascular functions. Close observation is performed to a level that preserves spontaneous breathing and airway reflexes. The main priority is early detection and treatment of abnormal respiratory movements and cessation of respiration which compromise oxygen levels in blood.
Patients often do not manifest with classical signs and symptoms of hypoxia under monitored anaesthesia care as they are sedated and their reflexes are blunted. Pulse oximetry that allows measurement of oxygen saturation (SpO2) has facilitated intervention before any complications such as bradycardia, hypotension, cardiac dysrhythmias or cardiac arrest sets in. SpO2 is an indirect measure of partial pressure of oxygen in arterial blood (PaO2). Possible causes of a fall in SpO2 during endoscopic procedures include hypoventilation due to drugs or physical presence of the endoscope, ventilation-perfusion mismatching or shunting due to aspiration of secretions, supine position of the patient or a combination of these factors.
Oxygen delivery through nasal prongs is an effective and safe method to administer supplemental oxygen during monitored anaesthesia care. A nasopharyngeal airway is a simple device that can be conveniently inserted to ensure a patent airway. Maintaining airway patency is the foremost task in any procedure where a definitive airway (such as a cuffed endotracheal tube) is not in place. Airway patency can be achieved by head tilt-chin lift or jaw thrust manoeuvres. If airway patency is not achieved by these simple manoeuvres, breaths may be delivered using bag and mask after temporarily suspending the flexible endoscopic procedure.
We conducted a prospective, randomised study comparing oxygen delivery through nasal prongs or through a T-piece without an after-burner connected to a nasopharyngeal airway in patients undergoing monitored anaesthesia care for flexible endoscopic procedures. We proposed to evaluate whether either of these two techniques of administering oxygen would reduce the incidence of hypoxia. We specifically looked at the efficacy and safety of these two devices, potential adverse events and satisfaction of the patient, endoscopist and anaesthesiologist.
| Patients and Methods|| |
This prospective, randomised study was started after obtaining approval from the Human Research and Ethical Committee. The study was also registered with the Clinical Trials Registry–India (CTRI No/2020/03/023855).
A sample size of 66 patients (33 in each group) was calculated on the basis of a pilot study whose primary outcome parameter was SpO2. WINPEPI (PEPI-for-Windows) software Version 11.65 (2016) (http://www. brixtonhealth.com/pepi4windows ) was used to generate a random assignment table. Patients undergoing flexible endoscopic procedures under monitored anaesthesia care were randomly divided into two groups on the basis of which the specific oxygen delivery device was used. While Group A patients received oxygen through nasal prongs, Group B patients received oxygen through a T-piece without an after-burner connected to a nasopharyngeal airway.
The study included patients aged 18–80 years belonging to the American Society of Anesthesiologists (ASA) Physical Status I–IV with no significant difference in age, gender, body mass index, ASA grading, comorbidities and mean duration of flexible endoscopic procedures. After a thorough preanaesthetic evaluation, written informed consent was obtained from patients before the procedure after a detailed explanation of the study protocol. Patients who did not have an adequate period of fasting, those on anticoagulants or who had a deranged coagulation profile, those with allergy to local anaesthetics, those with nasal deformities and those who were already intubated or tracheostomised were excluded from the study.
Pre-procedural preparation included nil by mouth for solids for 8 h and for clear fluids for 2 h. Patients were administered 4% lignocaine gargle and 10% topical lignocaine as is the recommendation for patients scheduled to undergo upper gastrointestinal endoscopy. An intravenous line was secured and intravenous fluids were started. All anaesthetic equipment were checked and made available in the procedure room. This included nasal prongs and a T-piece without an after-burner attached to a nasopharyngeal airway for oxygen administration. Patients were brought into the procedure room and instructed regarding proper use of the oxygen delivery device. After placing them supine on the procedure table, monitoring of electrocardiogram, noninvasive blood pressure and pulse oximeter was established. SpO2 readings were obtained while breathing room air. Nasal prongs were positioned in Group A patients and oxygen flow was started at 6 l/min (LPM). Once patients in Group B had reached a desired level of sedation using injection fentanyl (2 ug/kg), injection propofol 1 mg/kg, injection ketamine 1 mg/kg (checked by the absence of eye lash reflex and no active body movements), a nasopharyngeal airway well lubricated with lignocaine gel was inserted, a T-piece without an after-burner was attached using a 15-mm endotracheal tube connector and oxygen flow was started at 6 LPM. SpO2 was monitored every 5 min up to 60 min and beyond if the procedure was prolonged. The Ramsay Sedation Scale was used and a score of > 4 was maintained during the procedure. For our study, we defined hypoxia as an SpO2 < 90% lasting for at least 15 s. Adverse events were noted and dealt with as indicated in [Table 1].
At the end of the procedure, it was ensured that all patients responded to verbal commands, specifically corresponding to Ramsay Sedation Score of 3. Patients were then shifted to the recovery room and the satisfaction of the patient and endoscopist were noted.
| Results|| |
The study conducted over a period of 18 months included sixty-six patients of either gender aged 18–80 years belonging to ASA Physical Status I–IV posted for elective flexible endoscopic procedures under monitored anaesthesia care. They were randomly allocated into one of two groups on the basis of which a specific oxygen delivery device was chosen. Patients in Group A received oxygen at 6 LPM through nasal prongs while those in Group B received oxygen at 6 LPM through a T-piece without an after-burner connected to a nasopharyngeal airway. Drug requirement, SpO2 and adverse events (such as body movement, cough or nasopharyngeal injury) were monitored pre-procedure and every 5 min thereafter till the end of the procedure.
Comparison between the 2 groups revealed a statistically significant difference in hypoxia between two groups (P < 0.05) with patients receiving oxygen through nasal prongs showing a lower incidence of hypoxia [Figure 1] and [Table 2].
|Figure 1: Mean oxygen saturation in study groups. Group A: Nasal prongs. Group B: T-piece without an after-burner connected to nasopharyngeal airway|
Click here to view
| Discussion|| |
We compared two groups of patients. Patients in Group A received oxygen through nasal prongs and those in Group B received oxygen through a T-piece without an after-burner attached to a nasopharyngeal airway as mentioned earlier. Oxygen is usually supplemented during endoscopic procedures because of several factors that contribute to hypoxia such as loss of tone of airway musculature (resulting in falling back of the tongue), epiglottis obstructing the airway, laryngospasm during insertion of an endoscope if adequate depth of sedation has not been achieved and growth over cricoid region causing obstruction at the level of the larynx. Effective provision of supplemental oxygen during flexible endoscopy is challenging as the patient's mouth is open to facilitate passage of the endoscope.
In our study, we connected a T-piece without an after-burner to the nasopharyngeal airway through an endotracheal tube connector, but in another study quoted in literature, oxygen was delivered during endoscopy through nasal cannula while a nasopharyngeal airway was simultaneously inserted for airway protection. SpO2, drug requirement and adverse events (such as body movements, coughing, nasopharyngeal injury) were monitored pre-procedure and every 5 m till the end of procedure. We observed that the mean SpO2 between the groups showed no statistically significant difference. However, when adverse events such as hypoxia were compared between the two methods of oxygen delivery, a statistically significant difference (P < 0.05) was found between the two techniques of oxygen delivery, with the nasal prongs proving to be better.
It was hence concluded from this study that oxygen delivery through nasal prongs and oxygen delivery through T-piece without an after-burner through nasopharyngeal airway were comparable in terms of mean SpO2 during flexible endoscopic procedure under monitored anaesthesia care.
There was no difference in demographic profile or ASA physical status between the two groups. In either group, even the development of hypoxia (defined in our study as a drop in SpO2 to < 90% for more than 15 s) did not necessitate interruption of procedure or removal of the endoscope in the middle of procedure as hypoxia was immediately detected and treated with simple manoeuvres such as head tilt-chin lift or jaw thrust. Effectiveness of such corrective actions was not specified in other studies.,
In our study, a larger number of patients had hypoxia when they received oxygen through T-piece without an after-burner through nasopharyngeal airway. However, other studies quoted in literature differ in their outcome concerning hypoxia despite the same oxygen delivery devices being used during endoscopic procedures under monitored anaesthesia care.,
Xiao et al. conducted a study to evaluate the efficacy and safety of the nasopharyngeal airway relative to nasal oxygen tube in obese patients undergoing painless gastroscopy. They stated that oxygen delivery through nasopharyngeal airway is better than nasal prongs. King et al. provided oxygen supplementation through nasal prongs during general anaesthesia provided for gastrointestinal endoscopy procedures. A subgroup of patients who had a nasopharyngeal airway placed in addition had fewer episodes of hypoxaemia as compared to those who had oxygen supplementation through nasal prongs alone.
The causes of displacement of a nasopharyngeal airway may be the introduction of an endoscope and frequent change in position of head and neck. Most recent guidelines recommend the use of a nasopharyngeal airway only in those cases of hypoxic events that cannot be managed by simple manoeuvres such as an increment in oxygen supplementation through nasal tube or a chin lift manoeuvre. In our study, a nasopharyngeal airway of appropriate size was selected and was placed in patients who were randomly allocated to receive oxygen through it using a T-piece without an after-burner. Placement of a nasopharyngeal airway helps in preventing the tongue from falling back onto the posterior pharyngeal wall in sedated patients. The main difference in our study as compared to other studies, was that we connected a T-piece without an after-burner to the nasopharyngeal airway. The previously conducted studies used nasopharyngeal airway for protection of airway and oxygen delivery was using a nasal cannula. In our study, no patient needed bag and mask ventilation for maintaining SpO2, none required intubation and flexible endoscopic procedure was not interrupted or stopped in view of possibly developing hypoxia.
Müller et al. evaluated the safety and efficacy of routine insertion of nasopharyngeal airway during sedation for gastrointestinal endoscopy. The primary outcome measure was SpO2 < 90% (respiratory depression). It was observed that respiratory depression as indicated by an SpO2 < 90% (13.5% vs 1.9%, P = 0.002) occurred more frequently in patients without nasopharyngeal airway than in those with a nasopharyngeal airway. It was concluded that the routine placement of a nasopharyngeal airway can reduce the frequency of hypoxaemic events during sedation for endoscopic procedures. The technique of oxygen delivery in both the groups was not specified. In these studies, patients undergoing flexible endoscopic procedure were selected and divided into 2 groups.,, Both the groups received oxygen through nasal prongs and a nasopharyngeal airway was inserted in the intervention group. This is different from our study as we had delivered oxygen through nasal prongs in one group and in the other group, we inserted a nasopharyngeal airway connected to a T-piece without an after-burner, making it different from other studies that have been quoted. The nasopharyngeal airway prevented the occurrence of hypoxia in patients undergoing flexible endoscopies under anaesthesia in the reference studies.,, However, in our study, we observed that when oxygen was delivered through nasopharyngeal airway which was connected to T-piece without an after-burner through an endotracheal tube connector, more number of patients had hypoxia than when oxygen was delivered through nasal prongs. Our findings need to be confirmed with a study including a larger number of patients. For all patients, Ramsay sedation score was maintained > 4 during the endoscopic procedure. The overall experience of anaesthesia was satisfactory for both the patient and the endoscopist.
We believe our study had a limitation in that FIO2 was not monitored, and hence, we could not specifically quantify the degree of oxygen supplementation.
| Conclusion|| |
During flexible endoscopy under monitored anaesthesia care, oxygen delivery through nasal prongs results in a lower incidence of hypoxia as compared to oxygen delivery via a T-piece without an after-burner connected to a nasopharyngeal airway.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]