A heterogeneity index of microcirculatory blood flow was also calculated as the difference between maximal and minimal PPV values in five different mucosa areas divided by its own mean value (see Additional file 1). According to the consensus for the evaluation of microcirculation, we calculated the proportion of small vessels perfused (PPV), the total vascular density (TCD) and the functional capillary density (FCD). Continuous flows were considered as normal while intermittent and stopped flows were considered as abnormal. A cutoff value of 20 μm was used to classify vessels as large or small. Sublingual microcirculation assessmentĪ sidestream dark-field (SDF) imaging device (Micro Scan MicroVision Medical, Amsterdam, the Netherlands) was used to explore the sublingual microcirculation simultaneously to dead-space fraction measurements, ventilatory mechanics and oxygenation parameters at both inclusion and 24 h after. V D/ V T was calculated from the CO 2 production ( \(V_\) performed by the module were automatically corrected for circuit compression, as described elsewhere.
After 60 min of stabilization, hemodynamics and respiratory mechanics were recorded and blood gases collected. PEEP was set targeting the best respiratory-system compliance after a PEEP-decremental recruitment maneuver. Methodsįorty-two consecutive patients with early moderate and severe ARDS were included.
We sought to evaluate the relationships between dynamic variations in V D/ V T and extra-pulmonary microcirculatory blood flow detected at sublingual mucosa hypothesizing that an altered microcirculation, which is a generalized phenomenon during severe inflammatory conditions, could influence ventilation/perfusion mismatching manifested by increases in V D/ V T fraction during early stages of ARDS.
Although increased dead-space ventilation ( V D/ V T) has been described in ARDS, its mechanism is not clearly understood. Ventilation/perfusion inequalities impair gas exchange in acute respiratory distress syndrome (ARDS).
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