3. | RESULTS
We prospectively studied 32 infants: 17 receiving MD-nCPAP and 15 receiving bCPAP. Patient demographic and clinical characteristics are summarized in Table 1 and Table 2. There were no significant differences between the MD-nCPAP and bCPAP groups in any characteristic except corrected GA (median corrected GA in MD-nCPAP = 32 (IQR: 31 to 33), in bCPAP = 30 (IQR: 29 to 31), P = 0.006). Lung US Score (LUS), PEEP and FiO2 were not different between the groups, suggesting that the degrees of pulmonary impairment were similar.
Gastric emptying rates calculated as percentage emptied per minute (%emptied/min) from the values obtained by both ACSA and spheroid US methods at different time intervals were compared between MD-nCPAP and bCPAP groups. There were no significant differences in the rates measured by either ACSA or spheroid methods and between the MD-nCPAP and bCPAP groups, either as the emptying rate across the entire feeding duration or as individual early and late emptying rates (Figure 2a, 2b). The ACSA method demonstrated significantly faster gastric emptying in the early phase compared to the late phase in the 25+0 to 27+6 weeks GA group (Bonferroni adjusted p-value = 0.0008) but not in the 28+0 to 34+6 weeks GA group (Bonferroni adjusted p-value = 1), irrespective of ventilation group after accounting for multiple testing among paired comparisons (Figure 2a) . The spheroid method rate demonstrated significantly faster emptying in the early phase than in the late phase (p < 0.0001) for all infants, irrespective of ventilation group and GA group (Figure 2b).
Residual gastric contents prior to the next feeding were calculated to be 42.4% in the MD-nCPAP group and 31.9% in bCPAP group when using ACSA measurements, and 23.8% and 25.8% respectively when using spheroid method. Comparison of these residual gastric contents showed no significant difference between the MD-nCPAP and bCPAP groups by either ACSA (Figure 3a) or spheroid method (Figure 3b). None of the studied patients had emesis or measurable regurgitation.