Positive end-expiratory pressure improves elastic working pressure in anesthetized children

Abstract

Background: Positive end-expiratory pressure (PEEP) has been demonstrated to decrease ventilator-induced lung injury in patients under mechanical ventilation (MV) for acute respiratory failure. Recently, some studies have proposed some beneficial effects of PEEP in ventilated patients without lung injury. The influence of PEEP on respiratory mechanics in children is not well known. Our aim was to determine the effects on respiratory mechanics of setting PEEP at 5 cmH2O in anesthetized healthy children.

Methods: Patients younger than 15 years old without history of lung injury scheduled for elective surgery gave informed consent and were enrolled in the study. After usual care for general anesthesia, patients were placed on volume controlled MV. Two sets of respiratory mechanics studies were performed using inspiratory and expiratory breath hold, with PEEP 0 and 5 cmH2O. The maximum inspiratory and expiratory flow (QI and QE) as well as peak inspiratory pressure (PIP), plateau pressure (PPL) and total PEEP (tPEEP) were measured. Respiratory system compliance (CRS), inspiratory and expiratory resistances (RawI and RawE) and time constants (KTI and KTE) were calculated. Data were expressed as median and interquartile range (IQR). Wilcoxon sign test and Spearman's analysis were used. Significance was set at P < 0.05.

Results: We included 30 patients, median age 39 (15-61.3) months old, 60% male. When PEEP increased, PIP increased from 12 (11,14) to 15.5 (14,18), and CRS increased from 0.9 (0.9,1.2) to 1.2 (0.9,1.4) mL·kg- 1·cmH2O- 1; additionally, when PEEP increased, driving pressure decreased from 6.8 (5.9,8.1) to 5.8 (4.7,7.1) cmH2O, and QE decreased from 13.8 (11.8,18.7) to 11.7 (9.1,13.5) L·min- 1 (all P < 0.01). There were no significant changes in resistance and QI.

Conclusions: Analysis of respiratory mechanics in anesthetized healthy children shows that PEEP at 5 cmH2O places the respiratory system in a better position in the P/V curve. A better understanding of lung mechanics may lead to changes in the traditional ventilatory approach, limiting injury associated with MV.

Keywords: Mechanical ventilation; Pediatrics; Positive end-expiratory pressure; Respiratory mechanics.

Conflict of interest statement

Ethics approval and consent to participate

Institutional Review Board at Centro Hospitalario Pereira Rossell approved the study (#2852015).

Written informed consent to participate was obtained from the parents/guardians after preanesthetic interview by the PI of the study.

Consent for publication

Written consent was obtained from caregivers of included patients.

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

Individual value plot of driving pressure (cmH2O) with ZEEP and PEEP at 5 cmH2O in anesthetized healthy children

Fig. 2

Pressure – Volume loop (P/V curve) sketch summarizing findings of the study: Anesthetized children with ZEEP (panel a) and after setting PEEP at 5 cmH2O (panel b). PIP, PPL and Paw increased after addition of PEEP of 5 cmH2O (PIP’, PPL’,Paw’), but dP decreased (dP'). Given the same VT, CRS, represented as the angle of the diagonal line between PEEP and PPL, increased (CRS’). All of them are sign of a more efficient working pressures of the respiratory system better position in P/V curve. On (panel b) respiratory mechanics with ZEEP was added in gray tone as reference