Postnatal respiratory compliance among premature ventilated neonates associated with variable timing and dosing of antenatal steroids.

BACKGROUND: Antenatal steroids (ANSs) improve the respiratory compliance of premature infants. Many premature neonates are born before the administration of a complete course of ANS. OBJECTIVE: The objective of this study was to evaluate the respiratory system compliance (Crs) of premature (≤ 32 weeks gestation), intubated neonates in relation to the dose, and timing of ANS administration. STUDY DESIGN: Neonates (n = 61) were divided into four groups based on the dose and timing of ANS exposure: Group 1: no ANS; Group 2: partial course (one dose of betamethasone); Group 3: complete course (two doses of betamethasone administered within 2 weeks of delivery); and Group 4: remote course (two doses of betamethasone administered > 2 weeks before delivery). Crs was measured by single-breath occlusion technique. RESULTS: Indexed respiratory compliance ± standard error of the mean (mL/cmH2O/kg) adjusted for gestational ages were 0.359 ± 0.074, 0.366 ± 0.080, 0.625 ± 0.038, and 0.505 ± 0.060 for Groups 1 to 4, respectively. The mean indexed Crs in complete ANS was significantly higher than that of no ANS (0.266 ± 0.085; p = 0.016) as well as partial ANS group (0.259 ± 0.086; p = 0.025). CONCLUSIONS: Crs after birth was significantly higher among premature intubated neonates born to mothers who received a complete course of ANS within 2 weeks, compared with no ANS or a partial course of ANS.

Aerosol delivery during high frequency jet ventilation: an MRI evaluation.

BACKGROUND: We have previously demonstrated aerosol delivery during conventional and high frequency oscillatory (HFOV) ventilation using magnetic resonance imaging (MRI) in piglets. There are no reports on aerosol delivery during high frequency jet ventilation (HFJV). OBJECTIVE: To compare delivery of aerosolized gadopentetate dimeglumine (Gd-DTPA) in 3 neonatal ventilator circuits: conventional mechanical ventilation, HFOV, and HFJV. METHODS: Aerosols of Gd-DTPA (0.025 mol/L) generated using a jet nebulizer placed in the inspiratory limb of each ventilator were delivered into an in vitro lung model simultaneously. Multi-slice T1-weighted spin-echo sequence scans were obtained prior to and after 10 and 20 min of cumulative aerosol delivery. Gd-DTPA concentration was calculated from signal intensity changes, and the total amount of Gd-DTPA was estimated. RESULTS: Gd-DTPA was visualized in the lung model at 10 and 20 min for all 3 ventilators. Gd-DTPA delivery was highest with conventional mechanical ventilation (1.92 µmol at 10 min, 2.89 µmol at 20 min), followed by HFJV (1.59 µmol at 10 min, 1.98 µmol at 20 min) and HFOV (0.79 µmol at 10 min, 1.00 µmol at 20 min). CONCLUSIONS: This is the first report of effective aerosol delivery in a neonatal HFJV circuit. Future studies are needed for more accurate quantification of aerosol deposition.

Role of spontaneous breathing trial in predicting successful extubation in premature infants.

BACKGROUND: The ability of clinicians to predict successful extubation in mechanically ventilated premature neonates is limited. Identifying objective criteria for predicting successful extubation may reduce the incidence of failed extubation and the duration of mechanical ventilation. OBJECTIVE: To evaluate the validity of objective measures of lung function and spontaneous breathing trial (SBT) in predicting successful extubation among premature neonates with attempted extubations within the first 3 weeks of life. METHODS: Respiratory compliance (Crs) along with SBT was performed prior to elective extubations within 3 weeks of age in premature infants ≤ 32 weeks. Extubation was considered successful if patients remained extubated for > 72 hr. Ventilator settings including mean airway pressure (MAP), set rate, and fraction of inspired oxygen (FiO2) 24 hr after re-intubation were compared with pre-extubation settings, in patients requiring re-intubation. RESULTS: Thirty-nine of 49 infants (80%) were successfully extubated. Of 41 babies who passed SBT, only 5 infants failed extubation. SBT had 92% sensitivity, 50% specificity, 88% positive predictive, and 63% negative predictive value for successful extubation. Crs was comparable between infants who were successfully extubated and those who were not. CONCLUSIONS: A SBT prior to extubation may be a practical objective adjunct in predicting successful extubation in ventilated premature infants.