Results
A total of 104 point of care US were performed to 66 infants at a median
(IQR) GA 30 (29–31) weeks. Infants were classified into two groups
based on the outcome of extubation trials; succeeded vs failed
extubation. The two groups were comparable in demographic and clinical
characteristics (Table 1). LUS differed significantly between the two
groups (p=0.022) whereas LVEI did not differ between groups (Table 1).
Table 2 shows the respiratory characteristics of both groups; mean
airway pressure, duration of mechanical ventilation and of oxygen
therapy were significantly higher in group-2 compared to group-1. Other
ventilator parameters were comparable between the two groups.
OSI was different between those who succeeded and failed extubation: 2.1
(1.5 - 2.6) vs 3.4 (2.7-4.7), respectively; p <0.0001.
Duration of mechanical ventilation was significantly increased in
infants who failed extubation: 5 (5 - 8) days vs 8.5 (8 - 9) days,
p<0.0001. Comparisons of the study population based on LUS
severity are presented in supplemental tables (Tables S1 and S2).
Multivariate logistic regression was performed with extubation success
as the dependent outcome and LUS, LVEI and duration of mechanical
ventilation as covariates. In this model, LVEI remained insignificant
(p=0. 817).
LUS was able to predict extubation success at day3 (area under the curve
0.71, 95% CI: 0.55 – 0.88, p=0.023) and at day 7 (area under the curve
= 0.92, 95% CI: 0.82 – 1.0, p<0.001) (Figure 3). Table 3
presents predictive values for extubation success with LUS cut off
points at the highest sensitivity and specificity on days 3 and 7. LVEI
did not predict extubation success in ROC analysis (area under the curve
= 0.52, 95% CI: 0.32 – 0.71, p= 0.87) (Figure 3). The predictive
values for extubation success with LEVI are presented in Table 3. Using
DeLong test, the predictive values for LUS and LVEI were compared and
was found insignificant (p=0.19).
LVEI, measured at end-systole, correlated with PAP (r=0.66, 95% CI:
0.50 – 0.78, p<0.001) and with internal diameter of the
ductus arteriosus (r=0.25,95% CI: 0.01-0.46, p=0.04). (Supplement
Figures S1-S4). A total of 32 infants had PPHN with PAP >35
mmHg. There was no difference in PAP among infants who succeeded and
failed extubation (p=0.27), Table 1.