Percutaneous transtracheal jet ventilation (PTTJV) provides emergency ventilatory support in patients who cannot be adequately ventilated with a bag-valve-mask device using oral or nasal airways, a laryngeal mask airway (LMA), or endotracheal tube.1-3 This includes patients with upper airway foreign bodies, upper airway neoplasms, maxillofacial trauma, laryngeal edema, or infection.2,4 It is used electively with general anesthesia for surgery involving the larynx and subglottic areas.5 PTTJV involves inserting a catheter-over-the-needle (i.e., angiocatheter) through the cricothyroid membrane and delivering oxygen to the lungs using a high-pressure oxygen delivery system.6
ANATOMY AND PATHOPHYSIOLOGY
Early studies of transtracheal ventilation used transtracheal catheters connected to 4 to 5 L/min of oxygen.7 Oxygenation with this apparatus was adequate, but patients quickly developed hypercarbia due to lack of ventilation.8 This “apneic oxygenation” also occurs in ventilation through a catheter attached to a bag-valve device.9 The low pressure and flow of oxygen generated by the bag-valve device results in increases in PaCO2 of 4 mmHg/min and the rapid development of respiratory acidosis.1,10 Numerous studies have since demonstrated that intermittent jets of pressurized 100% oxygen at 50 pounds per square inch (psi) allow for both oxygenation and adequate ventilation.10,11
The anterior neck provides direct access to the airway via the trachea as it extends from the larynx into the lungs (Figure 31-1). At the top of the laryngeal skeleton is the thyroid cartilage. It lies at the level of the fourth and fifth cervical vertebrae. The laryngeal prominence (i.e., Adam’s apple) of the thyroid cartilage is more prominent in men and is easily palpated. The cricoid cartilage lies just inferior to the thyroid cartilage at the level of the sixth cervical vertebra. It serves as the junction of the larynx and trachea. Multiple cartilaginous rings support the trachea. Between the cricoid and thyroid cartilages lies the cricothyroid membrane.
Airway structures of the neck.
The cricothyroid membrane is a palpable membranous depression just inferior to the laryngeal prominence and is the access site for PTTJV.12 The cricothyroid artery is a branch of the superior thyroid artery. It travels transversely across the cricothyroid membrane just below the thyroid cartilage. Placement of the catheter through the lower half of the cricothyroid membrane will prevent injury to this small artery.13
The Emergency Physician should attempt to insert the largest possible catheter based on the limited information obtained from palpation of the landmarks. The cricothyroid membrane is found at different distances from the skin that vary based on patient weight and neck circumference. The mean of depth distance is approximately 2.3 mm.14 Ultrasonography can be used to identify the landmarks if unable to palpate the cricothyroid membrane.14-16 It is ...