All adult intubated patients in critical care were eligible for inclusion using an emergency waiver of consent. A minimum of four standardized video clips were taken by an investigator using an incident dark field (IDF) video-microscope (Cytocam, Braedius Medical, NL) who subsequently calculated a POEM score and recorded the time taken. On completion a second investigator blinded to the results of the first repeated this process. At a later stage (>1 month) investigators re-scored their own and their co-investigators images. Scores were analysed using Cohens weighted Kappa score to provide intra-user, inter-user and test-retest reliability. A kappa statistic was also calculated for test-retest reliability for POEM score 1-3 against POEM score 4-5 which is the threshold for fluid administration used in an ongoing interventional study (Clinical Trials.gov ID).