Each year, approximately 1% of the US population (2-3 million adults) experiences critical illness requiring placement of an endotracheal tube. While 60-80% of patients survive, more than half of survivors experience long-term problems with breathing, speaking, or swallowing. Identifying approaches that prevent long-term complications of critical illness is an urgent priority.
For every patient undergoing emergency tracheal intubation, clinicians select the size of endotracheal tube. The size of the endotracheal tube refers to the inner diameter of the tube. Smaller endotracheal tubes commonly used in adults have a diameter of 6.5 mm to 7.0 mm. Larger endotracheal tubes commonly used in adults have a diameter of 7.5 mm to 8.0 mm.
In current clinical care, some clinicians routinely use smaller endotracheal tubes while others routinely use larger endotracheal tubes. In a cohort of 2,652 patients enrolled in three recent trials conducted by our Pragmatic Critical Care Research Group (PCCRG), clinicians used a smaller endotracheal tube for 44.5% of patients and a larger endotracheal tube for 55.5%. While height and sex are the primary determinants of the diameter of a patient's trachea, these variables explain only 12% of the variation in the size of endotracheal tube clinicians use in current clinical care. This suggests that selection of endotracheal tube size in clinical practice is not "personalized" to the characteristics of the patient, but instead varies based on factors like the specialty of the clinician, the practice patterns of the hospital, and the region of the country.
Whether using a smaller vs larger endotracheal tube affects any patient outcome is unknown. Some experts have hypothesized that use of larger endotracheal tubes may cause acute injury to the larynx, which for some patients could progress to permanent scarring, impairing breathing, speaking, and swallowing. Thus, some experts currently recommend using smaller endotracheal tubes. Other experts hypothesize that the use of larger endotracheal tubes may reduce resistance to gas flow, reducing patients' work of breathing during spontaneous breathing trials, and making it easier to pass suction catheters, obtain diagnostic samples, and clear secretions. Such experts, therefore, currently recommend using larger endotracheal tubes in hopes that doing so might shorten the duration of invasive mechanical ventilation or even decrease the risk of death during critical illness. No randomized trials have ever compared smaller versus larger endotracheal tube sizes among critically ill adults. Only one observational study has evaluated the effect of endotracheal tube size on outcomes of critical illness. It suggested that smaller endotracheal tubes had no effect on survival to hospital discharge but could not exclude the possibility that endotracheal tube size might affect the duration of invasive mechanical ventilation. The study prompted published responses highlighting the lack of long-term outcomes and the biases inherent to observational studies, noting that the effects of smaller versus larger endotracheal tubes could only be proven with a randomized trial.
Because millions of critically ill adults receive either a smaller or larger endotracheal tube during tracheal intubation in an ED or ICU each year, and no prior randomized trial has evaluated the effect of endotracheal tube size on long-term outcomes (breathing, speaking, and swallowing) or short-term outcomes (duration of invasive mechanical ventilation and survival), a multicenter randomized trial is needed.
