Peak inspiratory pressure lacks accuracy to estimate plateau pressure in infants with severe obstructive lower airway disease.

Purpose: In children with acute respiratory distress syndrome receiving mechanical ventilation, the peak inspiratory pressure (PIP) is close to plateau pressure (P) when inspiratory flow approaches zero. We aimed to evaluate the reliability of PIP to estimate P in infants with severe respiratory viral infection (SRVI), characterized by increased airway resistance, and the accuracy of an equational model to estimates P (eP) based on PIP.

Methods: This was a retrospective observational study including mechanically ventilated children (1 to 24 month old) with SRVI, whose respiratory mechanics measurements were performed to evaluate PIP and P The measured P was compared with the result of the equation: eP = PIP - [5.067 - (0.858 × static compliance) - (0.018 × inspiratory resistance) - (0.390 × pressure above positive-end expiratory pressure) + (4.989 × inspiratory time)].

Results: Thirty-seven patients were included, with a median age of 3 (2-5) months. They presented a high inspiratory and expiratory resistance (136 ± 43 and 168 ± 66 cmHO/L/s, respectively) and a moderate reduction in static compliance: 0.75 ± 0.3 mL/kg/cmHO. PIP overestimated P (33 ± 3 and 26 ± 5 cmHO, p = 0.01), with a mean difference of 7.3 ± 4 cmHO. Moreover, the Bland-Altman analysis demonstrated a mean difference between P and eP of 1.0 ± 4.0 cmHO, with 95% limits of agreement of -6.9 and 8.8.

Conclusions: A significant difference between PIP and P was observed in infants with SRVI. The equation model was inaccurate for estimating P based on PIP. Any estimation of P from PIP needs to consider the resistance component of the respiratory system.