Automated determination of sublingual microcirculatory function in healthy volunteers

Despite recognition of its importance in the pathophysiology of sepsis,1 microcirculation is not monitored routinely in clinical practice. Video-microscopic techniques provide in vivo visualisation of microcirculation, allowing direct measurement of capillary density, perfusion, and flow dynamics. The CytoCam-IDF system (Braedius Medical, NL) allows bedside automated microcirculatory analysis at the point of acquisition. There are presently no validated ranges for automatically generated microvascular variables in health or disease. The aim of this study was to establish normal ranges for application in future studies researching the usefulness of this technique as an early diagnostic tool in sepsis or other conditions. We carried out a single-centre observational cohort study in adult patients and healthy volunteers free from acute illness. Participants were recruited in age-based groups: 18–34, 35–54, and ≥55 yr. Sublingual microvascular recordings were obtained using the CytoCam-IDF system and analysed using CytoCamTools V1.72 and V2.0. At least five recordings were taken from each subject. After acquisition, videos were assessed for quality according to the method described by Damiani and colleagues.2 Only subjects with a ‘reliable triplet’ of recordings available (three good or excellent recordings) were included for analysis. Measurements included total vessel density, perfused vessel density, proportion of perfused vessels, and the proprietary ‘average perfused speed indicator’. Forty-seven participants (51%) were included for analysis (Table 3).Table 3Age-specific microcirculatory measurements expressed as mean (standard deviation). APSI, average perfused speed indicator; PPV, proportion of perfused vessels; PVD, perfused vessel density; TVD, total vessel density18–34 yr (n=14)35–54 yr (n=16)≥55 yr (n=17)TVD20.3 (2.7)32.1 (9.5)20.6 (2.9)27.7 (6.7)21.8 (3.1)30.3 (10.5)PVD10.1 (2.8)30.2 (9.0)8.46 (4.80)25.8 (4.5)7.41 (3.30)27.5 (8.6)APSI5.00 (0.72)6.55 (0.67)5.21 (1.91)6.61 (0.57)5.50 (1.79)6.66 (0.67)PPV50.5 (13.5)96.9 (4.9)40.2 (20.6)96.5 (5.8)34.2 (14.7)96.0 (6.4)SoftwareV1.7V2V1.7V2V1.7V2 Open table in a new tab This is the first study to report age-specific normal values for automatically derived microvascular measurements using CytoCamTools V1.72 or V2.0. Whilst it was not powered nor designed to make comparisons between age groups or analysis methods, the data suggest that CytoCamTools V2.0 detects a greater total number of vessels and finds a greater number of these vessels perfused, and therefore, may represent a step forward from the previous software. There were no clear differences in the baseline microcirculatory measurements in healthy adults of different ages. The study also highlights the difficulty of achieving high-quality recordings in awake volunteers as has been noted in previous studies, which remains a challenge in bringing this technology into use in the clinical setting. National Institute of Academic Anaesthesia/Royal College of Anaesthetists small grants (Ernest Leach Research Fund).