Sample LDF data during a 30-second breath hold in a 8-year-old child. Legend: 1 — the initial value of perfusion index; 2 — the onset of breath hold; 3 — the onset of perfusion index reduction; 4 — the minimum value of perfusion index; 5 — the offset of breath hold; 6 —the value of perfusion index after normal breathing was restored.

Note. Here and in table 2 data are presented as arithmetic mean ± standard deviation. М represents mean perfusion index; σ represents mean square deviation (mean blood flow modulation); KV represents the coefficient of variation of perfusion index (blood flow variability); NT — neurogenic tone; МТ — myogenic tone; SI — shunt index; А_max, (А_max/3σ) × 100 % and (А_max/М) × 100 % — maximum and normalized amplitudes. * — р <0.5; ** — р <0.01; *** — р <0.001 in comparison with the same parameters in children of an earlier age; PU — perfusion units; AU — arbitrary units.

Note. М_init is the initial value of perfusion index before the inspiratory breath hold; P_react is minimal perfusion during the respiratory test; M_rest is the value of perfusion index after normal breathing was restored; Т3–Т1 is a time interval between the onset of breath hold and the onset of microcirculatory flow reduction; Т4–Т3 is a time interval between the onset of microcirculatory flow reduction and the minimum value of perfusion index; Т5–Т4 is a time interval between the minimum value of perfusion index and breath recovery; CFR is capillary flow reserve; ∆М is perfusion index shift. * — р <0.05; ** — р <0.01; *** — р <0.001 when compared to the corresponding values in children of an earlier age.