5 | LIMITATIONS
One weakness of this pilot study is its small sample size. Also, it was not possible to mask the type of CPAP to investigators performing US. Nevertheless, the likelihood of bias was minimized because data on CPAP and other clinical variables were not available to the investigators who analyzed the US images and performed the gastric volume calculations. Also, gastric emptying rates were calculated based on measurements during one feeding period, which may not be representative of all feeding periods. Still, pre-feeding residual measurements for two consecutive feedings (at the beginning and end of the US period) were similar, supporting the idea that gastric emptying rates are stable.