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lab report on blood pressure using a spignomanometer

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sphygmomanometer blood pressure measurement technique

Clinical photograph demonstrating the auscultatory method of blood pressure measurement in a research or clinical setting. The image is divided into two highlighted sections: (a) shows a Welch Allyn DS66 aneroid sphygmomanometer, featuring a circular gauge with a black face and white numerical scale, connected to a black rubber inflation bulb held by a researcher. (b) displays a dark blue reusable adult blood pressure cuff (Welch Allyn) secured around the subject's left upper arm. A stethoscope chest piece is placed over the brachial artery beneath the distal edge of the cuff to detect Korotkoff sounds. The researcher is shown wearing the stethoscope and manually inflating the cuff. This visual illustrates the gold standard for non-invasive blood pressure monitoring used to validate novel pulse wave sensors and algorithms. Key educational concepts include proper cuff placement, manual sphygmomanometry technique, and clinical cardiovascular assessment.

Clinical photograph demonstrating the auscultatory method of blood pressure measurement in a research or clinical setting. The image is divided into two highlighted sections: (a) shows a Welch Allyn DS66 aneroid sphygmomanometer, featuring a circular gauge with a black face and white numerical scale, connected to a black rubber inflation bulb held by a researcher. (b) displays a dark blue reusable adult blood pressure cuff (Welch Allyn) secured around the subject's left upper arm. A stethoscope chest piece is placed over the brachial artery beneath the distal edge of the cuff to detect Korotkoff sounds. The researcher is shown wearing the stethoscope and manually inflating the cuff. This visual illustrates the gold standard for non-invasive blood pressure monitoring used to validate novel pulse wave sensors and algorithms. Key educational concepts include proper cuff placement, manual sphygmomanometry technique, and clinical cardiovascular assessment.

This clinical photograph displays a comparative analysis of sphygmomanometer devices used for blood pressure measurement. Panel (a) shows the 'Merkfree' alpha-prototype, a mercury-free sphygmomanometer featuring a white 3D-printed thermoplastic (PLA) enclosure. The design includes a horizontal base compartment containing a black rubber inflation bulb and tubing, and a vertical measuring scale with high-contrast markings calibrated for mmHg. The device utilizes Galinstan, a non-toxic liquid metal alloy, as the measuring fluid within a glass tube, maintaining the traditional vertical column interface. Panel (b) provides a technical comparison between the Merkfree prototype and a standard Mercurial Sphygmomanometer (MS). Both devices are connected via a T-connector joint to a single inflation bulb and blood pressure cuff (visible in the foreground) to ensure simultaneous pressure application during validation trials. The comparison highlights differences in enclosure materials—white polymer for the prototype versus metallic for the conventional unit—while demonstrating the similar structural logic intended to maintain clinician familiarity and reduce rounding-off errors through improved scale calibration.

This clinical photograph displays a comparative analysis of sphygmomanometer devices used for blood pressure measurement. Panel (a) shows the 'Merkfree' alpha-prototype, a mercury-free sphygmomanometer featuring a white 3D-printed thermoplastic (PLA) enclosure. The design includes a horizontal base compartment containing a black rubber inflation bulb and tubing, and a vertical measuring scale with high-contrast markings calibrated for mmHg. The device utilizes Galinstan, a non-toxic liquid metal alloy, as the measuring fluid within a glass tube, maintaining the traditional vertical column interface. Panel (b) provides a technical comparison between the Merkfree prototype and a standard Mercurial Sphygmomanometer (MS). Both devices are connected via a T-connector joint to a single inflation bulb and blood pressure cuff (visible in the foreground) to ensure simultaneous pressure application during validation trials. The comparison highlights differences in enclosure materials—white polymer for the prototype versus metallic for the conventional unit—while demonstrating the similar structural logic intended to maintain clinician familiarity and reduce rounding-off errors through improved scale calibration.

Clinical photograph of a patient's hand being used to assess hand grip strength using a modified mercury sphygmomanometer. The setup includes a dark blue blood pressure cuff that has been rolled into a cylindrical shape to fit the patient's palm, connected via blue flexible tubing to a hand-held inflation bulb and a vertical mercury-filled column scale. The scale is mounted on a metallic base and shows numerical gradations for pressure measurement in mmHg. This clinical assessment technique is often utilized in postoperative hand rehabilitation, such as after ulnar claw hand deformity correction, to provide a reproducible and reliable measurement of functional grip strength. The photograph captures the educational application of standard diagnostic equipment for monitoring recovery in orthopedic and plastic surgery contexts.

Clinical photograph of a patient's hand being used to assess hand grip strength using a modified mercury sphygmomanometer. The setup includes a dark blue blood pressure cuff that has been rolled into a cylindrical shape to fit the patient's palm, connected via blue flexible tubing to a hand-held inflation bulb and a vertical mercury-filled column scale. The scale is mounted on a metallic base and shows numerical gradations for pressure measurement in mmHg. This clinical assessment technique is often utilized in postoperative hand rehabilitation, such as after ulnar claw hand deformity correction, to provide a reproducible and reliable measurement of functional grip strength. The photograph captures the educational application of standard diagnostic equipment for monitoring recovery in orthopedic and plastic surgery contexts.

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I now have everything needed to write a complete, authoritative lab report. Here it is:

Lab Report: Measurement of Blood Pressure Using a Sphygmomanometer

Course: Medical/Nursing Sciences Date: July 27, 2026 Subject: Cardiovascular Physiology - Clinical Skills

1. Aim

To measure arterial blood pressure non-invasively using a mercury or aneroid sphygmomanometer by the auscultatory method, to identify Korotkoff sounds, to record systolic and diastolic pressures, and to classify the recorded readings according to established clinical guidelines.

2. Learning Objectives

  • Understand the physiological basis of blood pressure measurement
  • Correctly identify the five phases of Korotkoff sounds
  • Accurately record systolic and diastolic blood pressure values
  • Classify blood pressure readings using the ACC/AHA classification system

3. Background / Theory

Blood pressure (BP) is the lateral force exerted per unit area by blood against the arterial wall, expressed in millimetres of mercury (mmHg). It has two components:
  • Systolic Blood Pressure (SBP): the peak pressure during ventricular contraction
  • Diastolic Blood Pressure (DBP): the minimum pressure during ventricular relaxation
Blood pressure is the product of cardiac output and total peripheral resistance. It is regulated by cardiac function, blood volume, vascular tone, and the autonomic nervous system.

The Sphygmomanometer

The sphygmomanometer (from Greek: sphygmos = pulse; manos = thin/sparse; metron = measure) consists of:
  1. An inflatable cuff with an inner pneumatic bladder
  2. A rubber inflation bulb with a valve
  3. A manometer (mercury column or calibrated aneroid gauge) to read pressure in mmHg
  4. A release valve for controlled deflation
The device was invented by Scipione Riva-Rocci in 1896. Nikolai Korotkoff refined the technique in 1905 by introducing auscultation of arterial sounds, which are now named after him. - Tintinalli's Emergency Medicine, Comprehensive Study

The Auscultatory Method and Korotkoff Sounds

When the cuff is inflated above systolic pressure, the brachial artery is fully occluded and no blood flow occurs. As cuff pressure is slowly released, blood forces through the partially compressed vessel, producing turbulent flow - this turbulence creates vibrations in the arterial wall detected as sound through a stethoscope placed over the brachial artery at the antecubital fossa. - Guyton & Hall Textbook of Medical Physiology
The sounds heard during deflation are divided into five phases:
PhaseSound CharacterClinical Significance
Phase ISharp tapping / thumpingFirst sound heard = Systolic BP
Phase IIBlowing or swishing murmurTurbulent flow as cuff partially occludes artery
Phase IIILouder, rhythmical thumpingFlow increasing through wider opening
Phase IVMuffled, softer soundsCuff pressure approaching diastolic level
Phase VComplete silence (disappearance)Diastolic BP (clinically used in most cases)
Sphygmomanometry diagram showing cuff placement on arm, five phases of Korotkoff sounds, and relationship between cuff pressure and arterial pressure
Figure: Sphygmomanometry - the five phases of Korotkoff sounds and their relationship to arterial pressure. - Medical Physiology (Boron & Boulpaep)
Note on diastolic reading: Most clinicians use Phase V (disappearance) as the diastolic pressure. However, in children, pregnant women, patients with aortic regurgitation, or after exercise, Phase IV (muffling) is used because sounds may persist even at very low pressures. - Ganong's Review of Medical Physiology, 26th Edition
The auscultatory method is accurate to within approximately 10% of direct intra-arterial catheter measurements. - Guyton & Hall Textbook of Medical Physiology

4. Apparatus / Materials

EquipmentSpecification
SphygmomanometerMercury or aneroid type, calibrated
StethoscopeStandard binaural, with diaphragm and bell
Blood pressure cuffStandard adult (bladder width ~12-13 cm); or appropriate size
SubjectAdult, rested for at least 5 minutes
Recording chartTo document readings
Pen/pencilFor documentation
Cuff sizing guideline (AHA recommendations): The pneumatic bladder should be 20% wider than the arm diameter, encircle at least 80% of the arm circumference, and be centred over the brachial artery. An undersized cuff overestimates blood pressure; an oversized cuff underestimates it. - Medical Physiology (Boron & Boulpaep)

5. Procedure

Pre-measurement preparation

  1. Ask the subject to rest quietly for at least 5 minutes before measurement. Avoid exercise, caffeine, smoking, or talking during this period.
  2. The subject should be seated comfortably with the arm supported at heart level (mid-sternal level), feet flat on the floor, and back supported.
  3. Remove any tight clothing from the upper arm.
  4. Select the appropriate cuff size.

Palpatory method (to estimate systolic pressure first)

  1. Locate the radial pulse at the wrist. Wrap the cuff snugly around the upper arm, 2-3 cm above the antecubital fossa, with the bladder centred over the brachial artery.
  2. Inflate the cuff while palpating the radial pulse. Note the pressure at which the radial pulse disappears.
  3. Inflate a further 20-30 mmHg above this level.
  4. Slowly deflate (2-3 mmHg/second). Note the pressure at which the radial pulse returns - this estimates the systolic pressure and prevents missing an auscultatory gap.

Auscultatory method (main measurement)

  1. Place the stethoscope diaphragm (or bell) gently but firmly over the brachial artery at the antecubital fossa (do not tuck it under the cuff).
  2. Inflate the cuff to 20-30 mmHg above the estimated systolic pressure from the palpatory step.
  3. Slowly release the valve at approximately 2-3 mmHg per second or per heartbeat.
  4. Systolic BP: Note the pressure reading on the manometer when the first tapping sound (Phase I Korotkoff) is heard.
  5. Continue deflating. Listen through phases II and III.
  6. Diastolic BP: Note the pressure reading when the sounds become muffled (Phase IV) or completely disappear (Phase V) - record both if there is a discrepancy.
  7. Deflate the cuff completely. Wait at least 1-2 minutes before repeating.
  8. Take two readings and record the average. If values differ by >5 mmHg, take a third measurement.
  9. Repeat on the other arm at the first visit and record both.

Documentation

  1. Record as: SBP / DBP mmHg (e.g., 118/76 mmHg), noting which arm was used, subject's position, time, and any relevant conditions.

6. Observations / Results Table

ParameterReading 1Reading 2Reading 3 (if needed)Average
Systolic BP (mmHg) - Right arm
Diastolic BP (mmHg) - Right arm
Systolic BP (mmHg) - Left arm
Diastolic BP (mmHg) - Left arm
Heart rate (beats/min)
Subject positionSitting / Supine
Time of measurement
Phase IV diastolic (if applicable)
Phase V diastolic (if applicable)
Sample result (to be replaced with actual readings):
  • Right arm: 118/76 mmHg (average of two readings)
  • Left arm: 116/74 mmHg
  • Heart rate: 72 bpm
  • Both readings within 10 mmHg of each other (acceptable)

7. BP Classification

Based on the ACC/AHA Blood Pressure Classification System for Adults (from Harrison's Principles of Internal Medicine, 22nd Edition, 2025):
CategorySystolic BP (mmHg)Diastolic BP (mmHg)
Normal< 120and< 80
Elevated120-129and< 80
Stage 1 Hypertension130-139or80-89
Stage 2 Hypertension≥ 140or≥ 90
Classification of sample result (118/76 mmHg): Normal blood pressure.

8. Discussion

Physiological significance of the readings

Systolic blood pressure reflects the peak force generated by left ventricular contraction. Diastolic blood pressure represents the elastic recoil of the arterial walls during ventricular relaxation and the resistance of the peripheral vasculature. Pulse pressure (SBP - DBP) reflects stroke volume and arterial compliance; normally 40-60 mmHg. Mean arterial pressure (MAP = DBP + 1/3 pulse pressure) approximates organ perfusion pressure.

Sources of error in sphygmomanometry

Source of ErrorEffect on ReadingHow to Avoid
Cuff too smallOverestimates BPUse correct cuff size
Cuff too looseOverestimates BPApply snugly
Arm above heart levelUnderestimates BPSupport at heart level
Arm below heart levelOverestimates BPElevate appropriately
Deflating too fast (>2-3 mmHg/sec)Underestimates systolic, overestimates diastolicSlow, steady deflation
Auscultatory gap not detectedUnderestimates systolicUse palpatory method first
Observer bias (digit preference)Rounds to nearest 0 or 5Use automated device or blind recording
"White coat hypertension"Overestimates true resting BPAutomated or home measurement
Recent exercise, caffeine, or stressOverestimates resting BPEnsure 5-minute rest

The auscultatory gap

An auscultatory gap is a period of silence between Phase I and Phase II sounds, most commonly seen in elderly patients with arteriosclerosis. If the cuff is not inflated above the true systolic pressure, the examiner may record a falsely low systolic value. Performing the palpatory method first prevents this error.

Clinical relevance

The ACC/AHA 2017 guidelines classify normal adult BP as below 120/80 mmHg. Hypertension is a major risk factor for stroke, myocardial infarction, heart failure, renal failure, and peripheral artery disease. A sustained difference of >10 mmHg between arms may indicate subclavian artery stenosis or aortic coarctation and warrants further investigation. - Harrison's Principles of Internal Medicine, 22nd Edition

9. Precautions

  1. Ensure the manometer is at eye level and calibrated to zero before use.
  2. Never inflate the cuff beyond 200-220 mmHg unnecessarily; prolonged occlusion causes discomfort and petechiae.
  3. Allow a minimum 1-2 minute rest between repeated measurements on the same arm.
  4. Do not measure on an arm with an arteriovenous fistula, lymphedema, axillary node dissection, or IV line.
  5. Ensure the stethoscope is not pressed under the cuff (produces artefact sounds).
  6. Mercury sphygmomanometers must be stored upright and handled carefully to prevent mercury spillage (environmental hazard).
  7. Inform the patient about the procedure before starting.

10. Conclusion

Blood pressure was successfully measured using the sphygmomanometer and auscultatory method. The five phases of Korotkoff sounds were identified, with Phase I marking the systolic pressure and Phase V (or Phase IV in special populations) marking the diastolic pressure. The readings were classified according to the ACC/AHA classification system. Accurate blood pressure measurement is a fundamental clinical skill that depends on correct technique, appropriate equipment sizing, and patient preparation. The auscultatory method gives values within 10% of direct intra-arterial measurements and remains the gold standard for clinical BP assessment.

11. References

  1. Guyton AC, Hall JE. Guyton and Hall Textbook of Medical Physiology. Elsevier; 2021. Chapter 15: Clinical Methods for Measuring Systolic and Diastolic Pressures.
  2. Boron WF, Boulpaep EL. Medical Physiology. Elsevier; 2017. Chapter 17: Blood Pressure Measurement by Sphygmomanometry.
  3. Barrett KE, Barman SM, Brooks HL, Yuan JX. Ganong's Review of Medical Physiology, 26th ed. McGraw-Hill; 2019. Chapter 31: Auscultatory Method.
  4. Loscalzo J et al. Harrison's Principles of Internal Medicine, 22nd ed. McGraw-Hill; 2025. Chapter 288: Blood Pressure Measurement.
  5. Tintinalli JE et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. McGraw-Hill. Sphygmomanometry.
  6. Cheung AK et al. International consensus on standardized clinic blood pressure measurement: A call to action. Am J Med. 2023;136:438.
Note on the diagram above: The figure from Medical Physiology (Boron & Boulpaep) illustrates the complete sphygmomanometry process - the left side shows cuff placement and stethoscope position over the brachial artery, while the right graphs show the five phases of Korotkoff sounds plotted against cuff pressure (red line) declining from above systolic to below diastolic. Phase I (tapping) corresponds to systolic; Phase IV (muffling) corresponds to diastolic.
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