High-Flow Heated and Humidified Oxygen Therapy and Gastric Distension
Condition: Gastric Distention
MeSH terms: Dilatation, Pathologic
Study type: Interventional

Summary: 
      High Flow Heated and Humidified Nasal Oxygen therapy (HFHHNO) has been increasingly used in
      emergency medicine to assist patients with short term respiratory failure and to provide
      adequate oxygen to the body prior to intubation.

      Gastric distension which is the bloating of the stomach due to air being pumped into it is a
      concern for anesthesiologists as it increases the risk of nausea and vomiting during surgery
      (aspiration).

      The objective of this study is use an ultrasound machine to measure the volume of fluid in
      the stomach before and after HFNO is used in a standard clinical manner.
    

Detailed description: 
      High Flow Heated and Humidified Nasal Oxygen therapy (HFHHNO) is being increasingly used in
      the emergency medicine and intensive care settings to manage patients with acute hypoxemic
      respiratory failure, and to optimize pre-oxygenation prior to intubation in patients with
      mild-to-moderate hypoxemia.

      More recently, there have been reports of applications in the anesthesia perioperative
      setting. In fact, it is possible that the single greatest potential advantages of HFHHNO for
      anesthesia practice is that (unlike face mask and CPAP devices) oxygen administration can be
      maintained during periods of apnea with the potential to significantly prolong the apnea time
      available for safe and effective airway management.

      However, the low levels of positive airway pressure associated with HFHHNO has raised the
      question of whether prolonged use could result in gastric insufflation thus increasing the
      risk of regurgitation and aspiration with an unprotected airway. Gastric distension is a
      concern for anesthesiologists because it leads to the activation of a
      parasympathetically-mediated reflex through the vagus nerve that leads to secretion of
      acetylcholine by enteric neurons. In turn, increased acetylcholine activates M3 receptors on
      parietal cells resulting in increased secretion of gastric acid. The combination of an
      increased volume of gastric secretions and high intraluminal pressure may place patients at
      risk of pulmonary aspiration.

      The primary objective will be any change in gastric fluid volume from the baseline to each
      scan following HFHHNO therapy. Participants will undergo an abdominal ultrasound scan prior
      to any oxygen therapy to provide a baseline. One 30-minute session of oxygen therapy will
      follow(up to 60-70 L/min). After session, another ultrasound scan will take place, identical
      to the baseline to obtain the same measurements. From the images taken by the ultrasound, a
      mathematical model can be applied to calculate the gastric volume (and any change).

      The secondary outcome will be the incidence of "gastric air distension" defined by
      qualitative ultrasound as a distended antrum with air content that blurs the posterior
      gastric wall.
    

Intervention name(s): High-Flow Heated and Humidified Oxygen Therapy (HFHHNO)
Intervention type(s): Device
Intervention description(s): Participants will undergo one session of high-flow heated and humidified oxygen therapy (HFHHNO) (up to 60-70 litre/min). They will undergo a gastric ultrasound scan after session of HFHHNO therapy.
Intervention model: Single Group Assignment
Intervention model description: Every participant will recieve one HFHHNO session, will get 30 mins of oxygen up to 60-70 L/min.
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: Gastric Ultrasound; Gastric Distension; Gastric Volume; Gastric Fluid Volume; High-flow oxygen therapy; HFHHNO; Healthy volunteer