Predicting the Need for Ventilation in Term and Near-Term Neonates

To determine whether the need for respiratory support can be predicted by oxygen requirement within the first 72 h in term and near-term infants. Methods: To mimic the population of infants that would often be delivered outside a tertiary centre we studied a retrospective cohort of infants greater than or equal to 32 weeks requiring oxygen, divided into three groups: cot oxygen only, nasal continuous positive airway pressure (NCPAP) only, or intermittent positive pressure ventilation (IPPV). We recorded each infant's peak fraction of inspired oxygen (FiO2) - i.e. FiO 2 in the first 72 h in the cot oxygen only group or maximum FiO2 prior to commencing the highest level of respiratory support. The peak FiO2 was used as a diagnostic test to predict any respiratory support or IPPV-sensitivity and specificity were calculated and receiver operating characteristic (ROC) curves plotted (FiO2 0.21-1.00) to identify the best balance point for prediction. Results: The cohort included 592 infants: 516 cot oxygen only, 46 NCPAP only and 30 IPPV. The proportion ventilated increased with increasing peak FiO2 - above 0.45 the proportion of infants ventilated exceeded 50%. To predict any respiratory support, the cut-point balancing sensitivity and specificity was a FiO2 greater than or equal to 0.35-58/136 required respiratory support (sensitivity = 0.76, specificity = 0.85, positive predictive value (PPV) = 43%, negative predictive value (NPV) = 96%). To predict IPPV the cut-point was a FiO2 greater than or equal to 0.5-28/47 treated with IPPV (sensitivity = 0.93, specificity = 0.97, PPV = 60%, NPV = 100%). Conclusion: The need for respiratory support can be predicted by oxygen requirement within the first 72 h in term and near-term infants with reasonable sensitivity and excellent specificity

Fast versus slow ventilation for neonates

To investigate the effect of ventilation rate on respiratory mechanics, 21 neonates ventilated in the neonatal period for various reasons were studied while being ventilated at 30 and 80 breaths/min. Dynamic respiratory system elasticity (ERS), dynamic respiratory system resistance (RRS), and alveolar pressure at end expiration (EEP) were calculated by using multilinear regression to fit the equation of motion of a linear single-compartment model. Technically satisfactory data were obtained from 13 neonates. With the fast ventilation rate, tidal volume and RRS decreased by a mean of 41.3% (p < 0.01) and 17.5% (p < 0.01), respectively, ERS and EEP increased by a mean of 8.3% (p < 0.05) and 22.2% (p < 0.01), respectively. Fast ventilation produced a shorter effective time constant during expiration, limiting the changes in EEP and, hence, in end-expiratory lung volume. The same changes in respiratory mechanics were also observed in neonates who did not show an increase in EEP even at high frequency. These neonates had a high elastance and time constant short enough to ensure adequate lung emptying. These results suggest that the respiratory mechanics of ventilated neonates are frequency dependent and that neonates with higher ERS, such as those with hyaline membrane disease, can cope with fast rate ventilation without developing dynamic hyperinflation