Feasibility for evaluation of the efficacy of conventional ventilatory support in very low birth weight infants.

Morbidity and mortality analysis in prematurely born low birth weight (LBW) neonates, very low birth weight (VLBW) neonates and extremely low birth weight (ELBW) neonates forms the cornerstone in current pediatric decision-making from both medical and socioeconomic point of view. The successful introduction of artificial ventilation for neonatal respiratory failure treatment has changed tremendously the prognosis of many diseases with a fatal outcome. This retrospective observational longitudinal study was designed to evaluate the changes in the following main indices: mean airway pressure (MAP), oxygenation index (OI), arterial-to-alveolar oxygen tension ratio (a/A PO2), alveolar-arterial oxygen gradient (A-a)DO2, ventilation index and VEI in VLBW infants treated with conventional ventilatory support (CV), assess the information yield of these indices as indicators of gas exchange at each and every one moment of CV, and to analyze their feasibility, accuracy and real-time convenience as indicators of the adequacy of inhalation therapy and their role as an indispensable tool in constructing the optimal treatment regimen in VLBW infants. Forty-seven VLBW infants requiring ventilatory support within 24 hours of birth were enrolled in the study. Four of the infants survived and the remaining 43 died. The data collected were entered into a high-yield Neonatal Intensive Computer File and the indices were followed up sequentially and thoroughly analyzed as the primary outcome measures of the study. Our results show that: 1. The combination of indices we propose is a useful high-yield discriminating method for evaluating the efficacy of neonatal ventilatory support, arterial blood gas exchange and clinical status. 2. These indices allow early diagnosis of the changes in pulmonary mechanics, hemodynamics and blood saturation. 3. Using the combination of indices improves the diagnostic reliability and information yield of each one of them. 4. The twofold pattern of change of the indices in VLBW infants is well-recognized:--whereas a/A and OI change rapidly in the group of non-survivors reflecting the delicate balance in optimal gas-exchange using conventional methods in the survivors group there is a sustained tendency towards an increase in a/A values with a concomitant decrease in OI values. The airway pressure is constant in the presence of great fluctuations in OI values reflecting the breakdown in oxygenation at the high price paid for its sustenance in the nonsurvivors group whereas the mean airway pressure showed a gradual decrease in the survivors group and allowed early weaning from mechanical ventilation. (A-a)DO2 remained high in the non-survivors group thus reflecting a high-degree, practically constant shunting whereas the same index showed a tendency towards decrease in the survivors group. 5. These indices allow optimal management of neonatal ventilation and oxygenation and timely correction or a change of the ventilatory or/and oxygenation strategy. 6. This information forms the basis for prognostic conclusions regarding the current status or the survival of the neonates.