Background: The surgical airway is the final pathway of the difficult airway algorithm and is often employed hastily amidst the chaos of difficult ventilation and desaturation. Apneic oxygenation via Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) can maintain oxygenation, providing the luxury of time in which to secure the difficult airway.
Case description: 57 Y male patient with recurrent squamous cell carcinoma of the larynx status post chemotherapy and radiation was scheduled for total laryngectomy.
Two months prior: Flexible laryngoscopy showed radiation changes to the pharynx and larynx, with moderate glottic edema. Video laryngoscopy revealed a grade 1 view. The patient was intubated with a 5.0 laser safe endotracheal tube and a small vocal cord tumor was removed.
Five days prior: Flexible laryngoscopy demonstrated moderate-severe glottic edema and interval growth of the L supraglottic mass with extension of tumor onto the superior surface of the L arytenoid complex.
The morning of surgery, the patient was comfortable, without respiratory distress or stridor. His oxygen saturation was 98% on RA. He endorsed new shortness of breath with ambulation. Imaging was reviewed with the ENT surgeons who agreed with our plan to induce the patient, place a supraglottic airway (AirQ) and to intubate the patient with a small fiberoptic scope through the AirQ.
The patient was preoxygenated to end tidal oxygen of 93%, induced, and an AirQ supraglottic airway was placed. Upon passing the fiberoptic scope, the glottic opening was noted to be smaller and more obstructed by tumor compared with 5 days prior. Two attempts to enter the glottis resulted in bleeding of friable tissue in the airway. After discussion with the surgeon, there was agreement to progress to tracheostomy. At this point, the patient became more difficult to ventilate. The THRIVE apparatus was requested and he was started on 70 L/min of humidified oxygen at 100% FiO2. Anesthesia was maintained with propofol and remifentanil. The procedure was technically difficult as the area was highly vascular. The patient's vital signs remained stable and his O2 saturation never fell below 100% during 25 minutes of apneic oxygenation. The end tidal CO2 upon resumption of tracheal ventilation was 53 mmHg--up from 29 mmHg before initiation of apnea.
Discussion:
This case could have become an airway catastrophe. However, apneic oxygenation allowed for calm and considered control of this difficult airway. THRIVE is based on the principle that in an apneic patient, approximately 200-250 mL/min oxygen will move from the alveoli into the blood, whereas only 8-20 mL/min of carbon dioxide moves into the alveoli. This leads to subatmospheric pressure in the alveoli, which generates flow of gas from the pharynx. The high flow fills the pharynx with high FiO2 gas and functions as an oxygen reservoir, as long as airway patency is maintained. As observed in this patient, PCO2 typically increases approximately 1 mmHg/min of apnea. The use of THRIVE in this case demonstrates the benefits of invoking this technology to prolong the apneic window to calmly and safely secure the difficult airway.
