Determination of Arterial Blood Pressure and Pulse Rate in Humans
Introduction
Arterial blood pressure (BP) and pulse rate (heart rate) are vital physiological parameters that provide critical information about cardiovascular health. Blood pressure measures the force exerted by circulating blood against arterial walls, while pulse rate indicates the number of heartbeats per minute. Accurate determination of these parameters is essential for diagnosing and managing conditions such as hypertension, hypotension, and arrhythmias.
1. Blood Pressure (BP) Measurement
1.1 Definition and Components
Blood pressure is recorded as two values:
-Systolic BP:
Maximum pressure during ventricular contraction (normal: ~120 mmHg).
- Diastolic BP:
Minimum pressure during ventricular relaxation (normal: ~80 mmHg).
Classification of BP (AHA Guidelines):
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|. |. | |
| Normal | <120 | <80 |
| Elevated | 120-129 | <80 |
1.2 Methods of BP Measurement
A. Direct (Invasive) Method
-Procedure:
A catheter is inserted into an artery (e.g., radial or femoral artery) and connected to a pressure transducer.
-Advantages: Highly accurate, continuous monitoring.
- Disadvantages: Invasive, risk of infection, used mainly in ICUs.
B. Indirect (Non-Invasive) Methods
1. Auscultatory Method (Manual Sphygmomanometer):
- Equipment: Mercury/aneroid sphygmomanometer + stethoscope.
- Steps:
1. Place the cuff on the upper arm at heart level.
2. Inflate cuff to ~180 mmHg (occludes brachial artery).
3. Slowly deflate while listening for Korotkoff sounds via stethoscope.
- First sound (Systolic BP): Turbulent blood flow resumes.
- Disappearance of sound (Diastolic BP): Smooth blood flow returns.
2. Oscillometric Method (Digital BP Monitor)
- Principle: Detects pressure oscillations caused by arterial pulsations.
- Advantages: Automated, user-friendly.
- Limitations: Less accurate in arrhythmias.
3. Palpatory Method (Only Systolic BP)
- Procedure:
- Inflate cuff until radial pulse disappears.
- Slowly deflate until pulse returns (systolic BP only).
1.3 Factors Affecting BP Readings
- White Coat Hypertension: Elevated BP due to anxiety in clinical settings.
- Cuff Size: Incorrect sizing leads to false readings.
- Body Position: BP is lower when lying down than sitting/standing.
- Caffeine/Exercise: Temporarily increases BP.
2. Pulse Rate Measurement
2.1 Definition and Normal Range
- Pulse rate: Number of arterial pulsations per minute (normal adult: 60–100 bpm).
- Tachycardia: >100 bpm.
- Bradycardia: <60 bpm.
2.2 Common Pulse Sites
1. Radial Artery - (wrist) – Most common.
2. Carotid Artery -(neck) – Used in emergencies.
3. Brachial Artery -(elbow) – Used for infants.
4. Femoral Artery-(groin).
5. Dorsalis Pedis (foot) – Checks peripheral circulation.
2.3 Methods of Measuring Pulse Rate
A. Manual Palpation
- Steps:
1. Place two fingers (not thumb) on the pulse site.
2. Count beats for 30 seconds × 2 (or 60 sec for irregular rhythms).
B. Electronic Methods
- Pulse Oximeter: Measures SpO₂ and pulse rate via fingertip sensor.
- ECG (Electrocardiogram): Most accurate for heart rate detection.
2.4 Factors Affecting Pulse Rate
- Exercise: Increases heart rate.
- Stress/Anxiety: Elevates pulse.
- Medications: Beta-blockers lower heart rate.
- Fever/Infection: Increases pulse.
3. Clinical Significance
3.1 Blood Pressure Abnormalities
- Hypertension: Risk factor for stroke, heart attack, kidney disease.
- Hypotension: May cause dizziness, fainting (shock, dehydration).
3.2 Pulse Rate Abnormalities
-Tachycardia: May indicate fever, anemia, or arrhythmias.
- Bradycardia: Common in athletes, but may signal heart block.
4. Conclusion
Accurate measurement of arterial BP and pulse rate is essential for cardiovascular assessment. While manual methods (auscultation, palpation) remain gold standards, digital devices provide convenience. Understanding these parameters helps in early detection and management of cardiovascular disorders.
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