Abstract
In mechanically ventilated preterm infants, adequate FRC must be maintained in order to avoid collapse of alveoli and ensure adequate oxygenation. PEEP as well as mean airway pressure may play a role in establishing and maintaining FRC. We have investigated 1) how adjustments of PEEP correlate to changes of FRC, 2) how long FRC takes to stabilize after adjustments of PEEP and 3) whether FRC depends more on PEEP or on MAP.
Methods: 8 neonates ventilated because of respiratory distress syndrome (n=6) or recurrent apnea (n=2) were studied (gest. age 26-34 wks (range), 28 wks (median), birthweight 550-2150g, 780g, age at measurement 2-35 days, 7 days, weight 880-2040g, 1020g). FRC was measured by means of the SF6-washout technique. PEEP was systematically varied, starting from the clinically selected value. Further, MAP was changed independently of PEEP by adjusting inspiratory time.
Results: 1) With variable PEEP, FRC was between 5.7 and 36.0 ml/kg of body weight (median 16.5). 2) Adjustments of PEEP correlated well with changes of FRC (2.3 ml kg−1 cmH2O−1, r=0.81). 3) Changes of MAP also showed a good correlation with changes of FRC (2.7 ml kg−1 cmH2O−1, r=0.77), because PEEP and MAP are interrelated. 4) When MAP was changed independently of PEEP by adjusting inspiratory time, no significant effect could be demonstrated. 5) After adjustments of PEEP, FRC took between 2 and 16 minutes for stabilization on a new level (median 8). This time could not be predicted from any other value.
Conclusions: 1) PEEP had a much stronger influence on FRC than MAP. 2) Stabilization ol FRC after adjustments of PEEP took up to 16 minutes. 3) Investigating pulmonary function, the selected PEEP and the time needed for stabilization of FRC after modification of PEEP has to be considered.
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Thome, U., Dinger, J., Töpfer, A. et al. 229 THE DEPENDENCY OF FUNCTIONAL RESIDUAL CAPACITY (FRC) ON POSITIVE ENDEXSPIRATORY PRESSURE (PEEP) AND MEAN AIRWAY PRESSURE (MAP). Pediatr Res 36, 41 (1994). https://doi.org/10.1203/00006450-199407000-00229
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DOI: https://doi.org/10.1203/00006450-199407000-00229