Ventilator Y-piece pressure compared with intratracheal airway pressure in healthy intubated children

J Clin Monit Comput. 2006 Apr;20(2):95-100. doi: 10.1007/s10877-006-9012-5. Epub 2006 May 16.

Abstract

Objective: Compare airway pressure measurements at the ventilator Y-piece of the breathing circuit (P( Y )) to intratracheal pressure measured at the distal end (P( T )) of the endotracheal tube (ETT) during mechanical ventilation and spontaneous breathing of intubated children.

Methods: Thirty children (age range 29 days to 5 years) receiving general anesthesia were intubated with an ETT incorporating a lumen embedded in its sidewall that opened at the distal end to measure P( T ). Peak inflation pressure (PIP) was measured at P( Y ) and P( T ) during positive pressure ventilation. Just before extubation, all measurements were repeated and imposed resistive work of breathing (WOBi) was calculated at both sites while breathing spontaneously.

Results: Average PIP was approximately 25% greater at P( Y ) (19.7 +/- 3.4 cm H(2)O) vs. P( T ) (15.0 +/- 2.9 cm H(2)O), p < 0.01. During spontaneous inhalation P( T ) was 59% lower ({bond}8.5 +/- 4.0 cm H(2)O) vs. P( Y ) ({bond}3.5 +/- 2.0 cm H(2)O), p < 0.01. WOBi measured at P( Y ) (0.10 +/- 0.02 Joule/L) was 86% less than WOBi measured at P( T ) (0.70 +/- 0.40 Joule/L), p < 0.01.

Conclusions: In healthy children P( Y ) significantly overestimates PIP in the trachea during positive pressure ventilation and underestimates the intratracheal airway pressure during spontaneous inhalation. During positive pressure ventilation P( T ) better assesses the pressure generated in the airways and lungs compared to P( Y ) because P( T ) also includes the difference in airway pressure across the ETT tube due to resistance. During spontaneous inhalation, P( T ) reflects the series resistance of the ETT and ventilator circuit, while P( Y ) reflects only the resistance of the ventilator circuit, accounting for the smaller decreases in pressure. Additionally, P( Y ) underestimates the total WOBi load on the respiratory muscles. Thus, P( T ) is a more accurate reflection of pulmonary airway pressures than P( Y ) and suggests that it should be incorporated into ventilator systems to more accurately trigger the ventilator and to reduce work of breathing.

MeSH terms

  • Anesthesia, General
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Intubation, Intratracheal / instrumentation*
  • Intubation, Intratracheal / methods*
  • Male
  • Positive-Pressure Respiration
  • Respiration*
  • Respiration, Artificial / instrumentation
  • Respiration, Artificial / methods*
  • Respiratory Insufficiency*
  • Respiratory Physiological Phenomena
  • Respiratory System
  • Ventilators, Mechanical