Anesthesia in the News
  • How to Reduce Hypoxia and Airway Maneuvers During GI Procedures

    According to a 2019 report from healthcare market research and consulting firm iData, over 51 million gastrointestinal (GI) procedures are performed annually in the US with an anticipated rate of growth of 2.6% annually.  Most take place in an outpatient setting in an ambulatory surgery/procedure center, commonly under intravenous (IV) sedation both to enhance patient comfort and to accomplish a more thorough clinical exam.

    Propofol is becoming increasing popular for intravenous sedation in GI laboratory procedures, with many facilities using it exclusively (Bannert et al., 2012; Lee et al., 2018).  However, airway obstruction and subsequent hypoxemia is a chief complication of any sedation agent—including propofol.

    Risks, modifiable and not

    Studies have found an elevated risk of airway obstruction or hypoxemia patients diagnosed with obesity (body mass index [BMI] of >30 kg/m2) or obstructive sleep apnea (OSA) (King et al., 2017; Lee et al., 2018; Riccio, Sarmiento, Minhajuddin, Nasir, & Fox, 2019).  Berry and colleagues defined OSA in their 2012 published work as apnea occurring during sleep for ≥10 seconds or hypopnea with respiratory excursions dropping by ≥30%.

    Unmodifiable risk factors for OSA include male gender, advancing age, and race.  Dudley et al. cite in their 2016 research that “Among African Americans, Native Americans, and Hispanics, OSA prevalence is increased, likely due in part to obesity.”  Modifiable risk factors of OSA include obesity; chronic narcotic, benzodiazepine, and alcohol use; endocrine disorders; smoking; and nasal pathology or chronic congestion.

    The investigators’ intent

    Against the background of the nation’s ongoing obesity epidemic, a Pittsburgh-based team of 3 CRNAs; 2 MDs; and an advanced practice nurse, sleep researcher, and professor at the University of Pittsburgh School of Nursing, launched a small quality improvement study enrolling 27 patients.  Their aim was to determine whether the use of a high-flow nasal cannula (HFNC) was associated with a decreased incidence of hypoxia or airway obstruction in patients graded with a STOP-BANG (SB) score of ≥5 who underwent propofol sedation in the gastrointestinal laboratory.

    According to Sharma and colleagues’ 2022-published continuing education activity, nasal HFNC therapy is an oxygen supply system capable of delivering up to 100% humidified and heated oxygen at a flow rate of up to 60 liters per minute.  “All settings are controlled independently,” the authors state, “allowing for greater confidence in the delivery of supplemental oxygen as well as better outcomes when used.”

    Patients can quickly be screened for OSA in the preprocedural area using the (SB) assessment (Chung et al., 2008).

    8 elements of STOP-BANG

    The SB questionnaire was used to screen patients with undiagnosed OSA in the preprocedural setting.  The SB scoring model calls for clinicians to note 8 different patient characteristics and to assign 1 point for each affirmative response:

    STOP-BANG

    Snore Loudly?

    Tired during the day?

    Observed stop breathing during sleep

    High Blood Pressure diagnosis

    BMI >35kg/m2

    Age >50 years

    Neck circumference >43cm (17 inches) for males/ 41 cm (16 inches) for females

    Male Gender

    Chung and colleagues’ 2008 prospective validation study demonstrated that a positive SB (score ≥3) has a sensitivity of 83.6% and 92.9% in predicting an AHI (apnea-hypopnea index) score of >5 (mild sleep apnea) and an AHI of ≥15 (moderate to severe sleep apnea.

    Study steps

    In their study, the Pittsburgh investigators had 3 specific objectives.  They sought to:

    • identify patients ≥18 years eligible for HFNC in the pre-procedure area utilizing the SB grading during pre-anesthesia assessment;
    • deploy HFNC on patients with an SB score ≥5; and
    • determine whether the use of an HFNC would decrease the incidence of hypoxia, apnea, and the need for airway maneuvers.

    The project team calculated an SB score for all outpatients undergoing either an esophagogastroduodenoscopy (EGD), esophageal ultrasound (EUS), or colonoscopy during their preanesthetic assessment.

    They devised a checklist to document typical airway maneuvers for addressing hypoxia in their study cohort including manual manipulation of the airway (eg, jaw thrust and chin lift), insertion of an oropharyngeal airway or nasopharyngeal airway, or abandonment of the monitored anesthesia care sedation technique via a conversion to a general anesthetic with or without endotracheal intubation.  The authors noted that each of these actions are reactive in nature, that is, “the presence of hypoxia or airway obstruction is required for them to be used.”

    Patients were transported to the procedure room and noninvasive standard monitoring was applied.  An HFNC unit was placed in standard fashion prior to initiation of propofol sedation set at a fraction of inspired oxygen (Fio2) of 100% and flow rate of 70 L/min.  No other sedative adjuncts were utilized and the specific dose of propofol was administered based on the clinical judgment of the CRNA.

    When the procedure was complete, the project team collected specific demographic and medical data about the patient (eg, age, gender, SB score, hypertension, diabetes, stroke, etc.) and interviewed the treating CRNA to ascertain if any hypoxia had occurred or if the need had arisen to perform any airway maneuvers.  In addition, the total amount of propofol administered was noted.

    Utilizing descriptive and inferential statistics, the data obtained from this project were compared to “the historical comparison group of patients with SB ≥5.”  Patients were classified as “no HFNC” and “HFNC” and subsequent data were reported as a frequency and percentage of the total number (%) or mean ± standard deviation.  The baseline data from a previous project had determined that 22% of the patients undergoing GI procedures in the study facility were at high risk for OSA with an SB score ≥5 and, of those patients, 50% had required some type of airway maneuver.

    ‘Proactive rather than reactive’

    In this study, the SB scores for all patients in both the “no HFNC” and “HFNC” groups were ≥5.

    Compared to the previous project group of patients for whom HFNC was not used and in whom the incidence of hypoxia, apnea, or the need for airway maneuvers occurred was measured, in this project the HFNC group required an airway maneuver in only 18.5% of patients (n = 5) (p = .021) versus 53.3% in the “no HFNC” cohort (n = 8).

    No significant group differences were found for incidence of hypoxia or apnea.  Apnea ≥10 seconds was seen in only 3.7% (n = 1) of the “HFNC” group, and no hypoxia of SpO2 ≤92% was observed in either group.

    Further, only the “no HFNC” group required placement of an oral airway (20%, n = 3) or nasal airway (6.7%, n = 1) and neither group had an unplanned intubation.

    While stipulating its small size and lack of power analysis performed, as their study was designed as a quality improvement project, the authors conclude that their findings demonstrated that “any patient with an SB score ≥5 can have [HFNC] used; thus, being proactive rather than reactive in the treatment of hypoxia.”

    “In this quality improvement project,” the authors wrote, “we showed that HFNC may be effective in reducing the need for airway maneuvers and associated hypoxia in patients with a high risk of OSA undergoing propofol-assisted procedures.”

    They state that, due to the prevalence of obesity, undiagnosed OSA will continue to increase in the general population (Fryar, Carroll, & Ogden, 2016).  As such, they suggest that there will be ongoing opportunities for use of the SB score for OSA screening and for implementation of therapies like HFNC to prevent hypoxia in patients undergoing procedural sedation.

    You can locate the link to full study, “Decreasing the Incidence of Hypoxia and Airway Maneuvers During GI Procedures.” Gastroenterol Nurs. 2022;45(3):167-173., at https://pubmed.ncbi.nlm.nih.gov/35657356/

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