Monitoring blood pressure regularly is essential in preventing and managing various health conditions including hypertension and heart disease. A device commonly used for this purpose is called the sphygmomanometer, often referred to as a blood pressure monitor. In this article, we will look into everything you need to know about sphygmomanometers, including what they are, how they work, the importance of blood pressure monitoring, and how to use these devices accurately.
What Is a Sphygmomanometer?
A sphygmomanometer is a medical device used to measure blood pressure. It consists of several components, including an inflatable cuff, a pressure gauge and a mechanism for inflating and deflating the cuff. The primary function of a sphygmomanometer is to determine the pressure of the blood against the walls of the arteries as the heart pumps it around the body.
Types of Sphygmomanometers
There are three main types of sphygmomanometers commonly used in clinical settings and for home blood pressure monitoring:
- Mercury Sphygmomanometer: This traditional type uses a column of mercury in a glass tube to measure blood pressure. It is considered highly accurate and serves as a reference standard for blood pressure measurement. However, due to environmental concerns and the potential hazards of mercury exposure, it’s use has decreased in recent years.
- Aneroid Sphygmomanometer: The aneroid sphygmomanometer is a popular alternative to the mercury model. It utilizes a small, flexible metal or plastic bellows to measure pressure. Aneroid sphygmomanometers are portable and more environmentally friendly. They require periodic calibration to maintain accuracy.
- Digital Sphygmomanometer: Digital sphygmomanometers are the most commonly used type for home blood pressure monitoring. They use electronic sensors and a digital display to provide blood pressure readings. Digital models are user-friendly and don’t require manual inflation or auscultation.
How Does a Sphygmomanometer Work?
A sphygmomanometer measures blood pressure using the principle of auscultation. Here’s a step-by-step explanation of how it works:
- Inflation: The cuff of the sphygmomanometer is wrapped around the upper arm or wrist (depending on the type of monitor used). The cuff is then inflated with air, which gradually compresses the underlying artery.
- Occlusion: As the cuff inflates, it applies pressure to the artery, temporarily obstructing or blocking blood flow.
- Deflation: The cuff is slowly deflated, allowing blood to flow back into the artery.
- Auscultation: During deflation, a stethoscope is placed over the artery being measured (typically the brachial artery in the upper arm). The healthcare provider or individual monitoring their blood pressure listens for the characteristic sounds of blood flow called Korotkoff sounds.
- Recording: The point at which the first sound (Korotkoff Phase I) is heard corresponds to the systolic blood pressure, which represents the pressure in the arteries when the heart contracts. The point at which the sounds disappear (Korotkoff Phase V) corresponds to the diastolic blood pressure, which represents the pressure in the arteries when the heart is at rest between beats.
Importance of Blood Pressure Monitoring
Monitoring blood pressure is important for several reasons:
- Early Detection of Hypertension: Regular blood pressure checks help identify hypertension (high blood pressure) in it’s early stages. Uncontrolled hypertension is a risk factor for heart disease, stroke, and other health problems.
- Managing Chronic Conditions: Individuals with conditions like diabetes, kidney disease, and heart disease must monitor their blood pressure to prevent complications.
- Medication Adjustment: For individuals taking antihypertensive medications, monitoring blood pressure helps healthcare providers adjust dosages as needed to maintain control.
- Lifestyle Modifications: Blood pressure monitoring can motivate individuals to make lifestyle changes such as adopting a heart healthy diet, exercising regularly, and reducing stress.
How to Use a Sphygmomanometer
Using a sphygmomanometer correctly is essential to obtain accurate blood pressure readings. Here’s a step by step guide on how to use a manual (aneroid) sphygmomanometer, which is commonly found in clinical settings:
Note: For digital sphygmomanometers, follow the manufacturer’s instructions provided with the device as the process may vary.
- A sphygmomanometer with an inflatable cuff and a pressure gauge
- A stethoscope
- A quiet environment free from distractions
- A comfortable chair for the individual whose blood pressure is being measured
Step 1: Prepare the Individual
- Ensure that the individual is seated comfortably in a relaxed position.
- Make sure their arm is supported at heart level, with the palm facing upward.
Step 2: Prepare the Equipment
- Place the stethoscope around your neck.
- Check the sphygmomanometer for any visible damage or defects.
- Ensure the pressure gauge is set to zero.
Step 3: Apply the Cuff
- Wrap the cuff around the individual’s upper arm, positioning it approximately 1-2 inches (2-3 cm) above the bend of the elbow.
- Secure the cuff tightly but not too tight. There should be enough room to slide two fingers between the cuff and the individual’s arm.
Step 4: Locate the Brachial Artery
Use your fingers to locate the brachial artery on the inner side of the arm, just below the cuff.
Step 5: Inflate the Cuff
- Hold the bulb (inflation bulb) in one hand and the pressure gauge in the other.
- Close the valve on the bulb by turning it clockwise.
- Squeeze the bulb to inflate the cuff until the pressure gauge reads around 30 mm Hg (millimeters of mercury) above the individual’s expected systolic pressure.
Step 6: Auscultate Blood Pressure
- Place the stethoscope’s chest piece over the brachial artery beneath the cuff.
- Slowly release the valve on the bulb by turning it counterclockwise.
- Listen carefully for the Korotkoff sounds.
- Note the reading on the pressure gauge when you hear the first distinct sound (Korotkoff Phase I). This is the systolic pressure.
- Continue deflating the cuff until the sounds disappear (Korotkoff Phase V). This is the diastolic pressure.
- Record both the systolic and diastolic pressures.
Step 7: Remove the Cuff
- Deflate the cuff fully by opening the valve on the bulb.
- Carefully remove the cuff from the individual’s arm.
Step 8: Interpret and Record Results
- Interpret the recorded values to determine the individual’s blood pressure.
- Document the systolic and diastolic pressures, along with the date and time of the measurement.
Step 9: Discuss the Results
If you are a healthcare provider, discuss the blood pressure reading with the individual and provide guidance or recommendations based on the results.