Your blood pressure cuff gives you two numbers. We turn those two numbers into eleven indices — each one revealing something different about your cardiovascular system that the raw reading alone cannot tell you.
This guide explains every index ExaHealth calculates, why each one matters, and what you can do if a reading falls outside the healthy range. Our analysis is grounded in the 2018 ESC/ESH Guidelines for the management of arterial hypertension and the 2017 ACC/AHA Hypertension Guidelines, supplemented by the original research papers behind each derived index.
The Basics: What Blood Pressure Actually Is
Blood pressure is the force your blood exerts against the walls of your arteries as your heart pumps it around your body. It is measured in millimeters of mercury (mmHg) and expressed as two numbers — for example, 120/80.
These two numbers capture a repeating cycle: your heart squeezes (systole), creating a pressure wave, then relaxes (diastole), and the pressure drops until the next beat. Every metric we calculate is derived from this cycle, your heart rate, or both.
The Silent Killer:
Blood pressure is often called the "silent killer" because dangerously high readings frequently produce no obvious symptoms. The only way to know your numbers is to measure them.
Primary Indices
Systolic Blood Pressure — The Top Number
What it is: The peak pressure in your arteries the instant your heart contracts and pushes blood into the aorta.
Why it matters: Systolic pressure is the single most important number for cardiovascular risk assessment in adults over 50. It reflects both the force of your heart and the stiffness of your large arteries.
| Range | Classification |
|---|---|
| Below 90 mmHg | Low — organs may not receive adequate blood flow |
| 90–120 mmHg | Normal — healthy arterial pressure |
| 121–139 mmHg | Borderline — your heart is working harder than ideal |
| 140–179 mmHg | Elevated — significant cardiovascular risk |
| 180+ mmHg | Critical — seek medical attention |
What drives it up: Arterial stiffness (which increases with age), high sodium intake, obesity, chronic stress, and sedentary lifestyle.
What brings it down: The DASH diet can reduce systolic pressure by 8–14 mmHg. Losing just 1 kg of body weight drops it by approximately 1 mmHg. Thirty minutes of daily brisk walking lowers it by 5–8 mmHg.
Diastolic Blood Pressure — The Bottom Number
What it is: The residual pressure in your arteries while your heart is resting and refilling between beats.
Why it matters: Diastolic pressure tells you about peripheral vascular resistance — how tightly your smaller arteries and arterioles are squeezing. For adults under 50, this number is actually a stronger predictor of cardiovascular events than systolic.
| Range | Classification |
|---|---|
| Below 60 mmHg | Low — may impair coronary blood flow |
| 60–80 mmHg | Normal — healthy baseline tension |
| 81–89 mmHg | Borderline — vessels offering more resistance than ideal |
| 90–109 mmHg | Elevated — heart working overtime against constricted vessels |
| 110+ mmHg | Critical — seek medical attention |
A crucial detail: Your heart muscle gets most of its own blood supply during diastole. So when diastolic pressure drops too low, the heart can literally starve itself of oxygen — even if systolic is fine.
Heart Rate — Your Cardiac Efficiency Meter
What it is: The number of times your heart beats per minute at rest.
Why it matters: A well-trained heart is physically larger and stronger. It ejects more blood per beat (higher stroke volume) and therefore needs fewer beats to circulate the same volume. That is why resting heart rate is one of the simplest indicators of cardiovascular fitness.
| Range | Classification |
|---|---|
| Below 50 bpm | Low — normal for athletes, check if not |
| 50–59 bpm | Borderline low — usually fine if fit |
| 60–100 bpm | Normal — healthy resting rate |
| 101–110 bpm | Borderline high — could indicate stress or deconditioning |
| 111+ bpm | Elevated — warrants investigation |
The fitness connection: Each 10 bpm increase in resting heart rate correlates with roughly a 20% increase in long-term cardiac risk. Athletes commonly have resting rates of 40–60 bpm. The most effective way to lower your resting rate is consistent aerobic exercise.
Derived Indices
These are calculated from your primary measurements. Each one isolates a specific aspect of cardiovascular function that raw systolic/diastolic numbers cannot show on their own.
Pulse Pressure — Arterial Stiffness Indicator
Formula: Systolic minus Diastolic (e.g., 120 − 80 = 40 mmHg)
What it reveals: Pulse pressure captures the "stretch" of each heartbeat. Young, elastic arteries absorb the pressure wave smoothly and keep pulse pressure narrow. Stiff, aging, or atherosclerotic arteries amplify the wave and widen the gap.
| Range | Classification |
|---|---|
| Below 30 mmHg | Low — may indicate weak cardiac output or reduced blood volume |
| 30–50 mmHg | Normal — healthy arterial compliance |
| 51–60 mmHg | Borderline — early sign of arterial stiffness |
| 61+ mmHg | Elevated — independent cardiovascular risk factor |
Why you should track it: A widening pulse pressure over months is one of the earliest signs of atherosclerosis — often detectable before systolic pressure rises significantly. It is an independent risk factor for heart attack and stroke, especially after age 50.
Mean Arterial Pressure (MAP) — True Organ Perfusion Pressure
Formula: Diastolic + (Pulse Pressure ÷ 3)
What it reveals: Unlike systolic and diastolic, which are momentary peaks and valleys, MAP represents the sustained average pressure that actually drives blood through your organs. Doctors in critical care use MAP as their primary hemodynamic target.
| Range | Classification |
|---|---|
| Below 60 mmHg | Critical — organs losing adequate perfusion |
| 60–69 mmHg | Low — borderline organ perfusion |
| 70–100 mmHg | Normal — optimal organ blood flow |
| 101+ mmHg | Elevated — sustained pressure damaging vessel linings |
The formula explained: The calculation weights diastole more heavily because your heart spends roughly two-thirds of each cardiac cycle relaxed. This makes MAP the most physiologically accurate single number for understanding whether your brain, kidneys, and heart are getting the blood flow they need.
Circulation Index — Vascular Efficiency Ratio
Formula: Pulse Pressure ÷ Systolic Pressure
What it reveals: What fraction of each heartbeat's peak pressure is "pulsatile" versus steady baseline. It is a window into arterial compliance and cardiac efficiency — how smoothly your cardiovascular system converts each heartbeat into forward blood flow.
| Range | Classification |
|---|---|
| Below 0.25 | Low — may indicate low cardiac output |
| 0.25–0.40 | Normal — balanced pulsatile and steady flow |
| Above 0.40 | Elevated — reduced arterial compliance |
Kerdo Index — Autonomic Nervous System Balance
Formula: (1 − Diastolic ÷ Heart Rate) × 100
What it reveals: The Kerdo Index uses the relationship between blood vessel tension (diastolic) and heart speed (rate) to estimate your autonomic balance — the invisible push-and-pull between your "fight-or-flight" sympathetic system and your "rest-and-digest" parasympathetic system.
| Range | Classification |
|---|---|
| Below −10 | Parasympathetic dominant — deep recovery/relaxation |
| −10 to +10 | Balanced — autonomic equilibrium |
| Above +10 | Sympathetic dominant — stressed/alert state |
Why this matters beyond BP: Your autonomic balance affects heart rhythm, digestion, sleep quality, immune function, and hormonal regulation. Chronic sympathetic dominance is linked to elevated cortisol, poor sleep, and increased cardiovascular risk over time. This index makes that invisible stress load visible.
First described by I. Kerdo in Acta Neurovegetativa, 1966.
Robinson's Index (Rate-Pressure Product) — Cardiac Oxygen Demand
Formula: (Systolic × Heart Rate) ÷ 100
What it reveals: The literal energy cost of keeping your heart beating. It multiplies the pressure your heart must pump against by how often it pumps, estimating myocardial oxygen consumption. Think of it as a fuel gauge for your heart.
| Range | Classification |
|---|---|
| 50–84 | Excellent — very efficient heart (typical of athletes) |
| 85–99 | Good — healthy cardiovascular conditioning |
| 100–114 | Fair — room for improvement |
| 115+ | Elevated — heart consuming excess oxygen at rest |
The fitness tracker you didn't know you had: Robinson's Index responds directly to fitness improvements. As you train, your resting heart rate drops and your blood pressure stabilizes — both pushing the score down. Watching this number decline over weeks is one of the clearest signals that your cardiovascular conditioning is improving.
Based on the original research by B.F. Robinson, Circulation, 1967.
Kvas Coefficient — Cardiovascular Endurance
Formula: Heart Rate ÷ Pulse Pressure
What it reveals: The balance between how fast your heart beats and how much pressure each beat creates. Within the normal range, it reflects how well your cardiovascular system adapts to the demands placed on it.
| Range | Classification |
|---|---|
| 5–11 | Low — increased peripheral resistance |
| 12–20 | Normal — healthy cardiovascular endurance |
| 21–35 | High — may indicate low pulse pressure relative to rate |
Why it responds to training: As cardiovascular endurance improves, heart rate decreases while pulse pressure stabilizes — both pushing the coefficient toward the optimal range. This makes it one of the most fitness-responsive indices we track, often showing changes within 4–8 weeks of consistent exercise.
Functional Cardiovascular Index (FCI) — Whole-Person Assessment
Formula: 0.011×HR + 0.014×SBP + 0.008×DBP + 0.009×Weight − 0.009×Height + 0.014×Age − 0.27
What it reveals: FCI goes beyond blood pressure. Originally developed by R.M. Baevsky for assessing cosmonauts' cardiovascular readiness in space medicine, it estimates your "adaptive potential" — how much reserve capacity your cardiovascular system has beyond what is needed for daily life.
| Range | Classification |
|---|---|
| 1.0–2.0 | Excellent — strong adaptive reserve |
| 2.1–2.5 | Good — satisfactory adaptation |
| 2.6–3.0 | Satisfactory — system under some strain |
| 3.1–3.5 | Poor — reduced adaptive capacity |
| 3.6+ | Critical — cardiovascular system significantly strained |
Why this catches what BP misses: You can have a perfectly normal 120/80 reading and still have a poor FCI if you are overweight, older, or have a high resting heart rate. Because FCI accounts for age and body composition, it provides a fairer assessment than raw blood pressure numbers alone.
Based on Baevsky et al., Cardiology, 1987.
Blood Circulation Efficiency (BCE) — Total Circulatory Output
Formula: Pulse Pressure × Heart Rate
What it reveals: BCE estimates the total circulatory work your heart performs each minute — combining how hard it pushes (pulse pressure) with how often it pushes (heart rate). It is a simplified proxy for minute volume that does not require specialized equipment.
| Range | Classification |
|---|---|
| Below 2600 | Low — may indicate reduced circulatory drive |
| 2600–4200 | Normal — balanced circulatory output |
| 4201–5500 | Borderline — heart working harder than necessary |
| 5501+ | Elevated — sustained cardiovascular overwork |
How to Get Accurate Readings
The quality of every index we calculate depends on the quality of your measurement. Here is how to get reliable readings consistently:
Before Measuring
- Wait at least 30 minutes after caffeine, smoking, or exercise
- Empty your bladder — a full bladder can raise BP by 10 points
- Sit quietly for 5 minutes
During Measurement
- Sit with your back supported, feet flat on the floor, legs uncrossed
- Place the cuff on bare skin at heart level
- Keep your arm relaxed, palm facing up
- Do not talk during the reading
- Take two readings with a brief rest between them
For Best Results
- Measure at the same times each day (morning and evening)
- Use the same arm consistently
- Record your readings immediately — trends matter more than any single number
A single reading is a snapshot. Real insight comes from patterns over days and weeks. Track consistently, and the trends will tell you more than any individual measurement ever could.
When to See a Doctor
While ExaHealth provides detailed analysis to help you understand your cardiovascular health, our interpretations are educational tools — they are not medical diagnoses.
Seek medical attention if:
- Your systolic pressure is consistently above 140 mmHg or below 90 mmHg
- Your diastolic pressure is consistently above 90 mmHg or below 60 mmHg
- You experience dizziness, severe headaches, chest pain, or shortness of breath alongside abnormal readings
- Multiple derived indices consistently fall outside normal ranges
Bring your data to your doctor. The trends and indices ExaHealth tracks can be valuable context for clinical decisions — but only a healthcare professional can diagnose and treat hypertension.
Scientific References
Our analysis methodology is grounded in the following peer-reviewed guidelines and research:
- Williams B, et al. 2018 ESC/ESH Guidelines for the management of arterial hypertension. European Heart Journal, 39(33), 3021–3104.
- Whelton PK, et al. 2017 ACC/AHA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. Hypertension, 71(6), e13–e115.
- Walker HK, Hall WD, Hurst JW (eds). Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition. Butterworths, Boston, 1990.
- Kerdo I. Ein aus Daten der Blutzirkulation kalkulierter Index zur Beurteilung der vegetativen Tonuslage. Acta Neurovegetativa, 29(2), 250–268, 1966.
- Robinson BF. Relation of heart rate and systolic blood pressure to the onset of pain in angina pectoris. Circulation, 35(6), 1073–1083, 1967.
- Baevsky RM, et al. Assessment of adaptation potential of the circulatory system in space medicine. Cardiology, 27(6), 78–82, 1987.
Track your blood pressure trends with ExaHealth. Log your readings and understand your patterns — because the numbers over time tell a story that a single reading never can.
