Baseline Digital Perfusion
Healthy resting blood flow keeps fingers warm and pink.
- 100%: Resting digital flow (normalized baseline)
- 34°C: Skin temperature (warm capillary bed)
- Relaxed: Vessel tone (normal sympathetic tone)
- ~5%: Raynaud prevalence (general population)
Normal digital circulation
Arterioles stay open, capillaries fully perfused, tissue oxygenated.
Sympathetic vascular tone
Baseline nerve signaling keeps vessel diameter steady and responsive.
Vasospasm Trigger — Cold or Stress Onset
Cold exposure or stress fires an exaggerated sympathetic vasospasm.
- <60s: Onset latency (cold-to-constriction)
- Hyperactive: Alpha-2 receptors (digital artery smooth muscle)
- Cold, stress: Common triggers (emotional or thermal)
- Rapid: Flow drop rate (seconds to minutes)
Sympathetic overdrive
Alpha-2c receptors overreact, clamping digital artery smooth muscle.
Rapid arterial narrowing
Vessel lumen narrows sharply, cutting inflow within seconds.
White Phase — Ischemic Pallor
Near-total flow cutoff leaves the finger pale and numb.
- <10%: Blood flow (of baseline)
- Chalk white: Skin color (ischemic pallor)
- Numbness: Sensation (reduced nerve perfusion)
- 2–10 min: Typical duration (severity dependent)
Arterial shutdown
Digital artery nearly closed, capillary bed drains of blood.
Ischemic symptoms
Pallor, coldness, and numbness follow the flow collapse.
Blue Phase — Cyanotic Pooling
Trapped deoxygenated blood stagnates, turning the finger blue.
- ~10–20%: Blood flow (sluggish, stagnant)
- Low: Oxygen saturation (deoxyhemoglobin dominant)
- Cyanotic blue: Skin color (venous stasis)
- Tingling: Sensation (partial reperfusion signals)
Venous stasis pooling
Residual trapped blood desaturates, deepening the cyanotic tint.
Tingling nerve signals
Partial capillary trickle sparks tingling as tissue starves.
Red Phase — Reactive Hyperemia
Vasospasm releases and blood surges back, flushing the finger red.
- 150–200%: Peak blood flow (rebound overshoot)
- Bright red: Skin color (reactive hyperemia)
- Throbbing pain: Sensation (reperfusion nerve firing)
- ~15–20 min: Recovery time (total attack duration)
Reflow surge
Vessel reopens fast, flooding tissue with oxygenated blood.
Return to baseline
Flow overshoot settles back to normal within minutes.