Factors that can affect blood pressure readings

Blood pressure is a vital sign for human well-being for a doctor. Measurement of blood pressure is an easy technique. But there are some precautions to be taken. If anyone finds that his or her blood pressure increased during a routine check-up, some factors should be excluded.

A doctor also needs to be concerned about the factors associated with inappropriate blood pressure readings.

These factors can be grouped in-

Patients related factors that affect blood pressure readings.
Doctor or health service provider-related factors that affect blood pressure readings.
Faulty techniques that are affecting blood pressure readings.

Patient-related factors that affect blood pressure:

Whitecoat hypertension: About 20% of the patients develop white coat hypertension while visiting a doctor. (http://www.webmd.com/anxiety-panic/features/beyond-white-coat-syndrome). It is due to anxiety and a fear of disease during a health check-up.
Anxiety and emotional condition: A patient's anxiety and emotional state may be responsible for the variance of hypertension. It is due to sympathetic activation, which causes vascular contraction and increases peripheral resistance of blood flow and increases blood pressure. So, a relaxed stat is required to get an accurate blood pressure reading.
Certain habits may raise blood pressure: Some practices may increase blood pressure. Like-
- Within 30 minutes of a cigarette intake, blood pressure will be increased. Sympathetic activation, vasoconstriction, etc., may play the role to cause this temporary spike in blood pressure. Smoking causes a rise in blood pressure about 8-9 mm Hg (Mercury) within 30 minutes.
- Sleep apnea also causes the same type of episode of increasing blood pressure for a short period.
- A small amount of alcohol intake can lower blood pressure. But chronic alcoholism and a large amount of alcohol intake are responsible for developing permanent hypertension.
- Caffeine also increases blood pressure. It is better to measure blood pressure at least 30 minutes after taking a tea or coffee.
Measuring blood pressure without taking a minimum of 3-5 minutes of rest: If a patient comes to the clinic or a health care provider and blood pressure is recorded instantly, it may be raised. Exertion and activities also activate the sympathetic action and cause a rise in blood pressure. Thats why at least 3 -5 minutes of rest is required before measuring blood pressure.
Talking or other activities during blood pressure measurement: If a patient talks during blood pressure recording with a doctor or nurse his or her systolic blood pressure measurement may increase 10 to 15mmHg. The patient should stay calm and quiet during Blood Pressure measurement.
Body temperature: Cold environment and cold body may raise blood pressure. A cold environment causes vasoconstriction and increases blood pressure.
With the full urinary bladder: If a patient’s blood pressure is measured with a full urinary bladder, his or her systolic blood pressure may rise 10-15 mm of Hg. (Reference: Marx GertieF, Orkin LouisR. Overdistention of the urinary bladder during and after anaesthesia. Can Anaes Soc J Sep 1966; 13:5: 500-504.)

Doctor or health service provider-related factors that affect blood pressure readings:

Skill: If a health service provider, who is measuring blood pressure, has lacked proper skill, he or she can give wrong readings. So It is very important to measure blood pressure by a skilled health professional if anyone finds abnormal blood pressure home measurement.

Health condition: If a health service provider has a certain health condition causing a mental disturbance or temporary hearing impairment may give a false reading. Even the surrounding environment play a role to record incorrect blood pressure.

Faulty techniques affecting blood pressure readings:

Small-sized cuff: It is essential to make sure the right-sized blood pressure measuring cuff is used on the patient’s upper arm when recording blood pressure. Most of the time, cuff size is overlooked, and accurate reading is not found. Few studies have shown that using a small blood pressure cuff can increase patient's systolic blood pressure to 10 to 40 mmHg. (Reference- Campbell NormanRC, McKay DonaldW. Accurate blood pressure measurement: Why does it matter? CMAJ 1999; 161(3): 277-278.)
Using of blood pressure cuff over Clothing^: During blood pressure measurement, the cuff should always be placed directly on the surface of the upper arm. Because clothing can vary a systolic blood pressure from 10 to 50 mmHg. (Reference- O’Brien Eoin, Asmar Roland, Beilin Lawrie, Imai Yutaka, Mallion Jean-Michel, Mancia Giuseppe, Mengden Thomas, Myers Martin, Padfield Paul, Palatini Paolo, Parati Gianfranco, Pickering Thomas, Redon Josep, Staessen Jan, Stergiou George, Verdecchia Paolo. European Society of Hypertension recommendations for conventional, ambulatory and home blood pressure measurement. J Hypertens 2003; 21: 821-848.)

Crossed led: During blood pressure measurement, a patient should always be seated in a comfortable chair with uncrossed legs. Crossing your leg may raise systolic blood pressure by 2 to 8 mmHg. (Reference- Adiyaman Ahmet, Tosun Nevin, Elving LammyD, Deinum Jaap, Lenders JacquesWM, Thien Theo. The effect of crossing legs on blood pressure. Blood Press Monit June 2007; 12:3: 189-193)
Arm position: The positioning of the upper arm below the heart level will also result in higher measurements, whereas positioning the upper arm above the heart level will give lower measurements. These differences can increase/decrease systolic blood pressure 2mmHg for every inch above/below the heart level. (Reference- Rastam I, Prineas RJ, Gomez-Marin O. Ration of cuff width/arm circumference as a determinant of arterial blood pressure measurements in adults.)
Back support: During the measurement of blood pressure back of the patient should be supported. Diastolic blood pressure measurement may be raised by 6 mm of Hg if a patient has an unsupported back. (Referance- Cushman WilliamC, Cooper KarenM, Horne RichardA, Meydrech EdwardF. Effect of back support and stethoscope head on seated blood pressure determinations. Am J Hypertens 1990; 3: 240-241.)

These are common essential factors that can impair a blood pressure reading. Other factors like pain, laboured breathing by patients etc., are also responsible for inappropriate blood pressure readings. So, these factors should be kept in mind to get an accurate blood pressure reading. Otherwise, blood pressure measurement and its treatment may hamper.

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Factors that can affect blood pressure readings