High-Flow Nasal Cannula and Desaturation Episodes in the Morbidly Obese Patients
Condition: Desaturation of Blood; Obesity; Colonoscopy; Sleep Apnea; High Flow Nasal Cannula
MeSH terms: Sleep Apnea Syndromes
Study type: Interventional

Summary: 
      It is standard practice in the United States and many parts of world to perform
      Gastrointestinal (GI) endoscopy with the patient under deep sedation. Obesity is accepted as
      a patient specific risk factor for hypoxic events during procedural sedation for GI
      endoscopic procedures. The Obese population has a higher prevalence of obstructive sleep
      apnea (OSA) which is characterized by repeated obstruction of the upper airway, and leads to
      apnea and desaturation. This prospective, randomized study was designed to compare the
      effectiveness of the high flow nasal cannula and the standard nasal cannula in morbidly obese
      (BMI > 40) patients receiving deep intravenous sedation during colonoscopies. This study will
      assess whether use of the high flow nasal cannula (HFNC) leads to less intraoperative
      desaturation events compared to the current standard of care.
    

Detailed description: 
      The prevalence of morbid obesity is increasing worldwide. As the severity of obesity
      increases, the incidence of diagnosed obstructive sleep apnea also rises. Studies have shown
      an incidence of sleep apnea as high as 64% in patients with a body mass index (BMI) over 40
      and 100% in patients with a BMI greater than 60. Patients with OSA have been shown to have
      significant desaturations under intravenous sedation due to airway narrowing and obstruction.
      Several studies have also shown that morbidly obese subjects, independent of a diagnosis of
      OSA, run a higher perioperative risk of adverse airway events, including hypoxia.

      Many morbidly obese subjects present to our institution for GI procedures under deep
      sedation. Providing anesthesia for this patient population is challenging and requires
      careful titration of drugs and superb airway management skills. The current standard of care
      for oxygen delivery in this setting is a Salter nasal cannula. There are no prospective,
      randomized studies that compare the use of a high flow humidified nasal cannula system and
      standard nasal cannula in morbidly obese patients presenting for colonoscopy under
      anesthesia.

      Humidified high flow nasal cannula (HFNC) oxygen therapy utilizes an air oxygen blend
      allowing from 21% to 100% FiO2 delivery and generates up to 60 L/min flow rates. The gas is
      heated (35 to 40 degree Celsius) and humidified through an active heated humidifier and
      delivered via a single limb heated inspiratory circuit (to avoid heat loss and condensation)
      to the subject through a large diameter nasal cannula. Theoretically, HFNC offers significant
      advantages in oxygenation and ventilation over conventional methods (9). Constant high flow
      oxygen delivery provides steady inspired oxygen fraction (FiO2) and decreases oxygen
      dilution. It also washes out physiologic dead space and generates positive end expiration
      pressure (PEEP) that augments ventilation. In the current narrative review, Sotello et al.
      summarized factors explained the improvement in respiratory parameters by using HFNC. (1)
      Washout of the nasopharyngeal dead space; (2) Reduction in inspiratory resistance associated
      with gas flow through the nasopharynx; (3) Improvement in respiratory mechanical parameters
      associated with gas temperature and state of humidification; (4) Reduction in metabolic work
      associated with gas conditioning; (5) Provision of mild distending pressure.

      Some studies have demonstrated a positive effect of HFNC on the apnea-hypopnea index (AHI)
      showing that use of HFNC could decrease hypoxic episodes in subjects with repetitive upper
      airway obstruction such as obstructive sleep apnea. The STOP-BANG questionnaire (SB) has been
      used successfully to screen patients undergoing therapeutic endoscopic procedures at higher
      risk for sedation-related adverse events.

      We are hypothesizing that the HFNC will help maintain a patent airway and improve gaseous
      exchange in the morbidly obese patients undergoing deep sedation for colonoscopies and will
      result in a significant decrease in intraoperative desaturation events, thus improving
      morbidity and overall safety for this subgroup.
    

Intervention name(s): The Comfort Flo system; The Salter nasal cannula
Intervention type(s): Device; Device
Intervention description(s): The Comfort Flo system will be used for the high flow nasal cannula during procedural sedation; A Salter nasal cannula will be used at 4L/ minute during the procedural sedation.
Other intervention name(s): High flow nasal cannula; Standard nasal cannula
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment