Apneic oxygenation is a physiological process where, in the presence of a patent airway, oxygen moves into the lungs secondary to aventilatory mass flow. Difference in the alveolar rates of oxygen absorption and carbon dioxide excretion results in a negative pressure gradient that drives this gaseous movement.1 Even though apneic oxygenation can maintain oxygen saturation, it cannot effect adequate carbon dioxide removal, and because of this, previous studies have demonstrated complications of acidosis, ventricular arrhythmias, and death.2,3
Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) is a novel airway technique and consists of high-flow humidified nasal oxygen therapy, up to 70 L/min, delivered with OptiFlow (Fisher and Paykel Healthcare Limited, Auckland, New Zealand). It extends apnea times, maintains oxygen saturation and is more effective in carbon dioxide clearance compared to apneic oxygenation (0.15 vs 0.35–0.45 kPa/min).4 Elucidation of the underlying mechanism of oxygenation is still not fully clear. Certainly, apneic oxygenation contributes but washout of the nasopharyngeal dead space, provision of a continuous positive airway pressure that decreases shunt, and a reduction in the work of breathing may be other factors.4,5
High-flow nasal cannulae or THRIVE has been increasingly adopted in multiple different clinical settings. It has been studied in the emergency and intensive care environments and has been used to facilitate awake fiberoptic intubation, bronchoscopy and dental extractions under sedation.6–8 Here, we present a patient with clinically relevant airway compromise who underwent emergent surgical tracheostomy under local anesthetic and sedation with THRIVE. Written consent was obtained from the patient for the publication of this case report.
A 35-year-old man presented with a 6-day history of a sore throat and increasing dysphagia, hoarse voice and left neck pain. His past medical history included a palindromic arthritis with a predominance of synovitis in his right wrist for which he was taking hydroxychloroquine. His body mass index was 25.3 kg/m2, and other than being a smoker, his medical history was unremarkable.
Bedside observations pointed toward a source of sepsis. He was systemically unwell with an initial heart rate of 163 beats/min, blood pressure of 125/96 mm Hg, oxygen saturation of 93% on room air, respiratory rate of 20 breaths/min, and tympanic temperature of 39.9°C. On examination, he was leaning forward and drooling saliva. Mild inspiratory stridor was present. Chest auscultation was normal. Further airway assessment showed good mouth opening, the ability to protrude his lower incisors anterior to this upper incisors, inflammation of his posterior pharynx, and a Mallampati score of II. The left neck was tender and neck movement was limited by pain.
Flexible nasoendoscopy revealed a bulging left pharyngeal wall, a thickened left aryepiglottic fold covered with white membranes, and an erythematous and slightly thickened epiglottis. The glottic aperture could not be visualized. Computed tomography of the neck demonstrated a left parapharyngeal abscess extending from below the left tonsil to the level of the false vocal cords. Critical tracheal narrowing was noted secondary to the abscess, and crucially, the maximum diameter of the trachea at the level of the thyroid cartilages was approximately 4 mm (Figure 1). Reactive cervical nodes were also found.
Application of oxygen at 15 L/min was started via facemask, and 10 mg oral morphine, 1.5 g cefuroxime, 8 mg dexamethasone, and IV fluids were administered. To prevent loss of the airway, a multidisciplinary decision was made with the ear, nose, and throat surgeons to undertake an emergent surgical tracheostomy. Orotracheal intubation, including a fiberoptic technique, was considered but the critical narrowing of the trachea coupled with abnormal airway anatomy, midline shift, friable tissues, edema, and pus was felt to preclude the atraumatic passage of any size of endotracheal tube.
Electrocardiographic, pulse oximetric, and noninvasive blood pressure monitoring were established in the operating room. Labetalol was used to reduce the blood pressure, which had increased to 182/105 mm Hg before THRIVE was started. In a head-up inclination of 40°, the patient was then preoxygenated with THRIVE using the OptiFlow nasal cannulae at a rate of 30 L/min for 15 minutes. Sitting position was maintained throughout the procedure, and THRIVE was continued at the same rate of 30 L/min until establishment of a definitive airway.
Before surgical incision, 2 mg midazolam and 40 μg fentanyl were administered in divided doses to provide analgesia and reduce anxiety. The site of the planned incision was infiltrated with a solution containing lidocaine 2% with a 1:100,000 concentration of epinephrine followed by a standard horizontal incision. Further sedation was needed at this point as the patient became agitated and remained hypertensive. Infusions of propofol at 0.02 mg/kg/min and remifentanil at 0.05 μg/kg/min were commenced while verbal contact was maintained with the patient at this time.
Sedation was deepened to effect to facilitate tolerance of the procedure and resulted in subsequent hypoventilation with a decrease in both the rate and depth of respiration. Later into the procedure, the patient was uncomfortable, and we communicated this to the surgical team, indicating that further sedation to reduce distress might lead to apnea or complete airway obstruction. The surgical team made it clear that if this were to occur, they would be able to rapidly establish access to the trachea. Propofol was increased to 0.09 mg/kg/min while remifentanil remained at 0.05 μg/kg/min. Soon after, the rate of respiration fell further to 2 per minute but oxygen saturations continued to be well maintained for about 10 minutes. Subsequent complete airway obstruction occurred at the time of tracheal manipulation but a window was immediately made in the trachea just as desaturation to 89% ensued. Oxygen saturations then recovered. THRIVE had maintained the oxygen saturations between 98% and 100% for 40 minutes despite hypoventilation close to apnea caused by deep sedation.
Once the tracheostomy tube had been inserted, anesthesia and muscle relaxation were induced with bolus doses of propofol and rocuronium. Maintenance of anesthesia was achieved with sevoflurane. Mechanical ventilation was commenced, and the initial end-tidal carbon dioxide was found to be 43 mm Hg. Subsequent videolaryngoscopy demonstrated an abnormal larynx, edema, and pus (Figure 2).
Surgical tracheostomy is indicated in patients in whom supraglottic, glottic, or subglottic pathology precludes any other method or technique of safely securing the airway. In a 5-year retrospective review of emergent awake tracheostomies at a tertiary care center, local anesthesia was supplemented with conscious sedation in 64.7% of patients.9
Sedation can be indicated to facilitate tracheostomy insertion for multiple reasons. First, emergent tracheostomy can be difficult for the awake patient to tolerate because of anxiety, claustrophobia, and discomfort. Second, sedation decreases the catecholamine effects of anxiety and agitation on blood pressure and heart rate. Good surgical access and a relatively still operative field can reduce bleeding and the risk of the injury to nerve, tracheal, or vascular structures and increase the likelihood of a shorter surgical procedural time. In this particular patient, the tracheostomy procedure is unlikely to have been tolerated in the absence of sedation with the additional risks of continued hypertension and associated increased bleeding. Sedation however, even with judicious use, is not without risk and can precipitate complete loss of the airway. Good communication with the surgical team is essential when considering the decision to deepen sedation in shared critical airway cases.
THRIVE is not a definitive airway but is a holding maneuver for continued oxygenation until one is established. In spontaneously breathing patients, THRIVE can deliver continuous positive airway pressure and splint open collapsible airways.4 It is probable that THRIVE did result in effective gas flow across the narrowed glottis while the patient was sedated until the time of complete airway obstruction. In previous studies, it has proven effective in patients with airway pathology,4,7 and a case report has reported its successful use, albeit at a higher oxygen insufflation rate, to facilitate tracheostomy under sedation in a patient with a large oropharyngeal mass completely obscuring the glottis.10 Desaturation is likely to have occurred sooner without THRIVE, which provided more time for the surgical team to complete the tracheostomy procedure.
Research into THRIVE is still in its infancy. It is not clear what the optimal oxygen insufflation rate is. An oxygen insufflation rate of 30 L/min was selected to reduce the risk of causing agitation or discomfort, and the patient tolerated this well while being preoxygenated in the absence of any sedation. In our view, it is likely that the tracheostomy procedure itself rather than the application of THRIVE contributed toward the subsequent agitation of the patient. Greater oxygen insufflation rates could however be better tolerated by the sedated compared to the awake patient and result in a longer time to desaturation.
THRIVE is an adjunct that can be used to maintain oxygen saturations when patients are sedated with some prerequisites. Airway patency should be maintained if needed with basic opening maneuvers such as jaw thrust. Caution though must be exercised if it is felt that jaw thrust, for example, could adversely stimulate the patient, precipitate laryngospasm, and thereby obstruct the airway. It does not work in the presence of complete airway obstruction. Once the patient has desaturated, THRIVE cannot be relied on to increase oxygen saturations. It is not a rescue tool for oxygen desaturation unlike facemask ventilation. THRIVE is therefore not a panacea and should not be used in the absence of a meticulous airway assessment and sufficient expertise. A comprehensive airway strategy must be in place should the initial airway plan fails.
Name: Neel Desai, FRCA.
Contribution: This author helped prepare the draft of the manuscript.
Name: Anna Fowler, FRCA.
Contribution: This author helped revise the manuscript.
This manuscript was handled by: Hans-Joachim Priebe, MD, FRCA, FCAI.
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