Postintubation tracheal injuries in critically ill patients - proposal for an additional prophylactic approach
- Z Vukcevic1
© Current Science Ltd 1997
Published: 1 March 1997
The use of endotracheal intubation for respiratory support of critically ill patients is a standard, life saving form of therapy. The lesions produced in the trachea by the erosive or cicatrical response to injury by intubation are still the most common tracheal injuries requiring treatment. It was demonstrated in many studies that there is a pressure necrosis type of injury occuring at points of tube-tissue interfacing. Severe trauma and hypovolemia with tissue hypoperfusion ischemia will markedly shorten the length of `safe intubation', and make tracheal tissue more susceptible to injury. In the setting of critical illness there is a clear analogy between pressure (decubitus) ulcers and tracheal postintubation pressure necrosis injuries. Similarly to decubitus ulcers, most of the tracheal pressure ulcers are due to prolonged, unrelieved pressure on delicate airway structures. When these pressures exceed the capillary-arteriolar blood pressure (ca 30 mmHg) tissue ischemia can lead to a sequence of inflammation-ulceration-granulation and stenosis. Inflation of an endotracheal tube cuff to the minimum pressure that creates a seal during routine positive pressure ventilation (at least 20 mmHg) reduces tracheal blood flow at the cuff site by 75%. Further cuff inflation or arteriolar hypotension can totally eliminate mucosal blood flow.
The concept of the Double Cuff Pressure Relieving Endotracheal Tube seems to be a logical response to the analogy between decubitus and tracheal pressure injuries. By simultaneously inflating and deflating Cuff 1 and Cuff 2, as a part of critical care routine, the pressure on delicate tracheal tissue could be intermittently completely alleviated and arteriolar-capillary blood flow at the points of cuff-tissue interfacing restored. Furthermore, the diffusion of frequently used anesthetic nitrous oxide into endotracheal tube cuffs, with consequent increase in the pressure against the tracheal mucosa, could also be easily addressed by this modified endotracheal tube.