Peripheral vascular response to inspiratory breath hold in paediatric homozygous sickle cell disease

Abstract

There is increasing evidence that autonomic dysfunction in adults with homozygous sickle cell (haemoglobin SS) disease is associated with enhanced autonomic nervous system-mediated control of microvascular perfusion. However, it is unclear whether such differences are detectable in children with SS disease. We studied 65 children with SS disease [38 boys; median age 7.2 (interquartile range 5.1-10.6) years] and 20 control children without symptoms of SS disease [8 boys; 8.7 (5.5-10.8) years] and recorded mean arterial blood pressure (ABP) and daytime haemoglobin oxygen saturation (S(pO(2))). Cutaneous blood flux at rest (RBF) and during the sympathetically activated vasoconstrictor response to inspiratory breath hold (IBH) were measured in the finger pulp of the non-dominant hand using laser Doppler fluximetry. Local factors mediating flow motion were assessed by power spectral density analysis of the oscillatory components of the laser Doppler signal. The RBF measured across the two study groups was negatively associated with age (r = -0.25, P < 0.0001), ABP (r = -0.27, P = 0.02) and daytime S(pO(2)) (r = -0.30, P = 0.005). Children with SS disease had a higher RBF (P = 0.005) and enhanced vasoconstrictor response to IBH (P = 0.002) compared with control children. In children with SS disease, higher RBF was associated with an increase in the sympathetic interval (r = -0.28, P = 0.022). The SS disease status, daytime S(pO(2)) and age explained 22% of the variance in vasoconstrictor response to IBH (P < 0.0001). Our findings suggest that blood flow and blood flow responses in the skin of young African children with SS disease differ from those of healthy control children, with increased resting peripheral blood flow and increased sympathetic stimulation from a young age in SS disease. They further suggest that the laser Doppler flowmetry technique with inspiratory breath hold manoeuvre appears to be robust for use in young children with SS disease, to explore interactions between S(pO(2)), ABP and autonomic function with clinical complications, e.g. skin ulceration.

Figure 1

Skin blood flux in the pulp of the index finger of the non-dominant hand measured using laser Doppler fluximetry before and during three inspiratory breath holds (IBHs) each lasting 6 s  The start of each IBH is marked by the bar. A period of 3 min was allowed between each IBH. Abbreviations: RBF, resting blood flux; and MinBF, minimal blood flux.

Figure 2

Mean resting blood flux (RBF; A) and mean change in blood flux during inspiratory breath hold (IBH; B) expressed as a percentage change from baseline measured in African children with sickle cell (SS disease) (n= 65) and control children (n= 20)  Data are expressed as the median, range and 95% confidence interval; *P= 0.002 and **P < 0.0001.