Optimal tracheal tube cuff inflation in infants: Implications for mechanical ventilation and respiratory mechanics

Uncuffed tracheal tubes (TT) are used to intubate infants and children to avoid laryngotracheal tissue injury. The geometric mismatch resulting from such intubation limits the efficacy of mechanical ventilation, and reliability of derived respiratory mechanical properties. This study tested the hypotheses that (1) normal stresses applied to the cuff surface by leak flows during ventilation result in intracuff pressure (P-cuff) fluctuations proportionate to leak magnitudes, and (2) these fluctuations reach a steady minimum when cuff volume reaches a critical value (V-crit) at which the TT-airway mismatch is removed. Physical model and piglet measurements showed that, during simultaneous cuff inflation and mechanical ventilation, P-cuff consisted of a leak-dependent (P-cuff,P-l) component that cycles with the ventilator superimposed on a ramp rise due to cuff inflation. The breath-to-breath peak P-cuff,P-l(max P-cuff,P-l) decreased as leak flows are reduced, and these were relatively greater for higher ventilator flows and when the load impedance is increased such as by disease. These results describe a reproducible method of TT cuff inflation that removes leaks without increased risk of laryngotracheal tissue injury. Moreover, inflation of the TT cuff more securely improved ventilation efficacy and allowed for accurate respiratory mechanics. (C) 2001 Biomedical Engineering Society.