Background Skin blood flow is highly variable accounting for 5–33% of cardiac output (Kenny 2011), and is often one of the first organs to change during early shock. In children, capillary refill time (CRT) is a crucial component of cardiovascular assessment and, despite marked variability, it remains a useful predictor of significant illness in children (Tibby 1999, Craig 2010). To allow development of new technologies to assess cutaneous blood flow a simple but valid model of reduced perfusion is required.
Aims 1) Develop an acceptable paediatric model for reduced cutaneous perfusion, 2) Assess the ability of laser Doppler (LD) and green light photoplethysmography (gPPG) to detect these changes.
Participants and methods Healthy children (5–17 years) were recruited. Simultaneous forearm LD blood flow and gPPG CRT measurements were obtained at baseline (room temperature) and during localised cooling of the arm (4oC microenvironment). gPPG CRT was measured using a reflectance mode gPPG coupled with an automated pressure application system.
Results Ten children completed the study over a typical timeframe of 45 min. Median LD blood flow decreased significantly from baseline during the cold exposure (P < 0.01) whilst gPPG CRT increased (P < 0.05) (see Figure).
Conclusion This model appears to be both feasible and acceptable to children. Confirmation of reduced blood flow is observed using LD. Our automated CRT utilising gPPG appears useful in this model. After additional validation, the suitability and usefulness of automated CRT could be assessed in paediatric clinical trials with a view to improving recognition of early shock.