Understanding Vital Signs & Oxygen Saturation

• Vital signs include heart rate (HR), oxygen saturation (SpO2), non-invasive blood pressure (NIBP), respiratory rate (RR), and body temperature (BT).
• In the image, these values are HR: 62 BPM, SpO2: 99%, NIPB: 102/67 mmHg, RR: 22 RPM, and BT: 36.6°C.

Saturation

• Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin in the blood.
• SpO2 = HbO2 / (HbO2 + Hb)
• There are different types of oxygen saturation: venous (SvO2), tissue (StO2), and peripheral (SpO2).
• Peripheral oxygen saturation (SpO2) is measured using pulse oximetry.

Pulse Oximetry

• Pulse oximetry is a method used to measure the percentage of oxygen the blood is carrying.
• Normal arterial blood oxygen saturation levels in humans are 95-100%.
• A level below 90% is considered low and is called hypoxemia.
• Conditions that affect oxygen saturation include COPD, asthma, heart disease, anemia, collapsed lung, pulmonary embolism, and congenital heart defects.

Blood Pressure (BP)

• Blood pressure is the pressure or tension exerted on the arterial walls as blood pulsates through them.
• Factors affecting BP include age, exercise, stress, race, genetics, food, obesity, smoking, alcohol, and disease.

Types of BP Measurement Tools

• Sphygmomanometer: Has a calibrated glass tube containing mercury.
• Aneroid: Has a calibrated dial with a needle that points to numbers on the face of the dial.
• Electronic or digital: Uses a digital display and usually includes the pulse rate.

Blood Pressure Measurement Procedure

• Rest the patient for five minutes before measurement.
• For ambulant patients, measurements are normally made with the patient seated, and either arm can be used.
• Support the patient's arm comfortably at about heart level, with the arm exposed.
• Ensure there is no air trapping in the cuff before inflation.
• Place the manometer at heart level and ensure it is positioned straight and at eye level.
• Wrap the cuff 2.5 cm above the antecubital area over the brachial artery.
• A blood pressure cuff that is too small or too large can affect readings.
• Palpate the radial pulse and pump until no pulse is felt to estimate preliminary systolic pressure.
• Clean the stethoscope earpieces and diaphragm before use, and make sure the sound is clear and not muffled when placing earpieces into the ears.
• Place the diaphragm over the brachial pulse.

Measuring Blood Pressure

• Pump the cuff 20-30 mmHg above the previous preliminary systolic readings.
• Slowly deflate the cuff and listen to both systolic and diastolic readings using a stethoscope.
• Systolic pressure is the pressure at which the first clear tapping sounds (Korotkoff sounds) are heard.
• Diastolic pressure is the pressure at which the sounds disappear completely.
• Korotkoff sounds include Phase 1 (a sharp "thud"), Phase 2 (a blowing or swishing sound), Phase 3 (a softer thud than phase 1), Phase 4 (a softer blowing sound that disappears), and Phase 5 (silence).
• The highest normal blood pressure reading is 120/80 mmHg.
• Factors affecting blood pressure readings include cuff size, cuff placement over clothing, back/feet support, leg crossing, rest time before measurement, patient talking, labored breathing, full bladder, and arm position relative to heart level.
• Ensure the cuff is fully deflated after measurement.
• Document the reading after the procedure.

Hypertension Guidelines

• According to 2017 ACC/AHA guidelines, hypertension is defined as ≥ 130/80 mmHg, while in 2023 ESH guidelines, it is ≥ 140/90 mmHg.
• Normal BP ranges (mmHg) differ between the 2017 ACC/AHA (Normal: <120/80, Elevated: 120-129/<80) and 2023 ESH (Optimal: <120/80, Normal: 120-129/80-84, High-Normal: 130-139/85-89) guidelines.
• Hypertensive BP ranges differ as well, with 2017 ACC/AHA defining Hypertension Stage 1 as 130-139/80-89 and Stage 2 as ≥ 140/90, while the 2023 ESH defines Hypertension Grade 1 as 140-159/90-99, Grade 2 as 160-179/100-109, and Grade 3 as ≥ 180/110.

Hypotension

• Hypotension is defined as blood pressure below the normal range consistently i.e. B/P < 90/60 mmHg.
• A drop in blood pressure may result from loss of blood, loss of vascular tone, or cardiac pumping problems.