Relationship of neonatal endotracheal tube size and airway resistance.
BACKGROUND
Infants receiving mechanical ventilation require narrow-lumen, small-diameter endotracheal tubes.


OBJECTIVE
Compare the resistances of endotracheal tubes used in the neonatal intensive care unit.


METHODS
Endotracheal tubes of internal diameter 2.5, 3.0, 3.5, and 4.0 mm were tested with a standard neonatal ventilator and a test lung. An endotracheal tube of each diameter was cut to 12 cm and connected to a flow transducer at one end and the test lung at the other. Serial measurements of resistance were made at various flows (6, 8, 10, and 12 L/min) and ventilator rates (30-90 breaths/min) encompassing the ranges of clinical practice. Analysis of variance was performed for each tube size, comparing resistance to flows and ventilator rates.


RESULTS
Resistance was significantly higher with the 2.5 mm tube than with the others. There was also a consistent trend, in all the tube sizes, towards higher resistance as flow was increased.


CONCLUSIONS
The higher resistance of the 2.5 mm tube may be detrimental to extremely low birthweight infants kept on mechanical support merely "to grow." The higher resistance may increase the work of breathing and thus increase caloric expenditure and impede growth.
Department of Pediatrics, Division of Neonatal-Perinatal Medicine, Unviersity of Michigan Health System, Ann Arbor, Michigan, USA.
Melisa J
MJ
Oca
Michael A
MA
Becker
Ronald E
RE
Dechert
Steven M
SM
Donn
D000403:Airway Resistance; D000704:Analysis of Variance; D016001:Confidence Intervals; D003422:Critical Care / Q000379:methods; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D006801:Humans; D007224:Infant Care / Q000379:methods*; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D008297:Male; D011336:Probability; D012121:Respiration, Artificial / Q000295:instrumentation*; D018570:Risk Assessment