Presented at the Neonatal Society 2003 Spring Meeting.
Cheema IU1, Sinha AJ2, Kempley ST2, Ahluwalia JS1
1 Box 226, NICU, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ. UK
2 NICU, The Royal London Hospital, White Chapel, London SE1
Background: Abnormal levels of arterial CO2 in newborn infants may be associated with adverse neurological and pulmonary outcomes (1, 2). Arterial CO2 is inversely proportional to alveolar ventilation, for which minute volume is a proxy measure. In order to alter minute volume during conventional pressure-limited ventilation, clinicians vary either the differential pressure and hence the tidal volume (VT), or the ventilator rate. Clinically, tidal volume delivered by the ventilator is judged by visual assessment of chest excursion. Under these conditions determining the correct tidal volume, is a subjective process.
Aim: To determine whether use of a volume-oriented approach to ventilation compared to conventional ventilation would reduce the incidence of out-of-range arterial CO2 values (< 5 or > 7 kPa) obtained from the first arterial blood gas following admission to a NICU.
Methods: Study was carried out in two tertiary NICUs and was approved by the local research ethics committees of the two institutions. Infants < 34 weeks’ gestation, requiring IPPV from birth were randomized, after initial stabilization on synchronized intermittent positive pressure ventilation (SIPPV), to either further SIPPV (SIPPV group) or SIPPV plus Volume Guarantee (VG group). After randomisation the ventilator settings for infants in the SIPPV group remained unchanged from those used for stabilization. Infants in the VG group received a set tidal volume of 4 ml/kg, with the peak inspiratory pressure (PIP) limit set to 4 cm higher than that used during their initial stabilisation. The study end point was the arterial blood gas analysis done after arterial catheterisation.
Results: A total of forty infants were randomised to SIPPV or VG.
Conclusion: There is a significant difference in the mean first PaCO2, with the SIPPV group mean lower than the BAPM recommendation. Reduction in the incidence of out of range CO2values seen in the VG group did not reach statistical significance. VG modality could be used to avoid hypocarbia in conditions of rapidly improving lung compliance
References
1. Greisen G, Munck H, Lou H. Severe hypocarbia in preterm infants and neurodevelopmental deficit. Acta Paedtiatr Scand 76 : 401-404, 1987.
2. Dreyfuss D, Solar P, Basset G, Saumon G. High inflation pressure pulmonary edema: Respective effects of high airway pressure, high tidal volume, and positive end-expiratory pressure. Am Rev Respir Dis 1988; 137: 1159-1164.