Impact of microcirculatory video quality on the evaluation of sublingual microcirculation in critically ill patients.

Abstract

We aimedto assess the impact of image quality on microcirculatory evaluation with sidestream dark-field (SDF) videomicroscopy in critically ill patients and explore factors associated with low video quality. This was aretrospective analysis of a single-centre prospective observational study. Videos of the sublingual microcirculation were recorded using SDF videomicroscopy in 100 adult patients within 12h from admittance to the intensive care unit and every 24h until discharge/death. Parameters of vessel density and perfusion were calculated offline for small vessels. For all videos, a quality score (-12=unacceptable, 1=suboptimal, 2=optimal) was assigned for brightness, focus, content, stability, pressure and duration. Videos with a total score ≤8 were deemed as unacceptable. A total of 2455 videos (853 triplets) was analysed. Quality was acceptable in 56% of videos. Lower quality was associated with worse microvascular density and perfusion. Unreliable triplets (≥1 unacceptable or missing video, 65% of total) showed lower vessel density, worse perfusion and higher flow heterogeneity as compared to reliable triplets (p<0.001). Quality was higher among triplets collected by an extensively-experienced investigator or in patients receiving sedation or mechanical ventilation. Perfused vessel density was higher in patients with Glasgow Coma Scale (GCS) ≤8 (18.9±4.5 vs. 17.0±3.9mm/mm2 in those with GCS >8, p<0.001) or requiring mechanical ventilation (18.0±4.5 vs. 17.2±3.8mm/mm2 in not mechanically ventilated patients, p=0.059). We concluded thatSDF video quality depends on both the operator's experience and patient's cooperation. Low-quality videos may produce spurious data, leading to an overestimation of microvascular alterations.