Vital Signs: Oxygen Saturation, Pulse, and Blood Pressure

Pulse Oximetry and Oxygen Saturation ($SpO_2$)

• Placement and Site Rotation     * Common placement sites for pulse oximetry sensors include the fingers and the earlobe.     * In a clinical setting like the Emergency Room (ER), sensors are often taped or clipped to one location and not rotated.     * In mobile vitals monitoring (e.g., using a portable device), it is recommended to check different fingers to ensure all sites are perfusing properly.
• Factors Affecting Oxygen Saturation     * Chronic conditions such as Pneumonia, Chronic Obstructive Pulmonary Disease (COPD), emphysema, and asthma can cause a decrease in oxygen saturation.     * Acute conditions, including pulmonary swelling or structural physiological changes in the lungs, also affect the body's ability to maintain normal oxygen levels.
• Clinical Symptoms of Low Oxygen ($Hypoxia$)     * Tachycardia: An increased heart rate as the body attempts to push oxygenated blood through the system faster.     * Tachypnea: An increased respiratory rate to take in more oxygen.     * Low $O_2$ Saturation: Observed directly on the pulse oximeter.     * Restlessness: A common early sign, particularly frequent in pediatric asthma cases.     * Neurological Changes: As levels drop further, patients exhibit decreased mental alertness and increased confusion due to decreased oxygen perfusion to brain tissue.
• Nursing Interventions for Low $O_2$ Saturation     * Deep Breathing: Encourage the patient to take deep, purposeful breaths.     * Positioning (Fowler’s Positions):         * Semi-Fowler’s: Head of the bed elevated to $45^{\circ}$.         * High Fowler’s: Head of the bed elevated to $90^{\circ}$.     * Oxygen Administration:         * Nasal Cannula: First-line intervention consisting of two prongs in the nose and tubing around the ears; commonly used for nursing home patients.         * Mask: Used if the nasal cannula is insufficient; provides higher flow oxygen.
• Signs of Improvement in Oxygenation     * Pink Mucous Membranes: Improvement is marked by healthy color in the lips and gums.         * Pallor: Lack of color in mucous membranes.         * Cyanosis: A blue tint to mucous membranes or skin around the mouth, signaling a significant drop in oxygen.     * Mental Status: Return of alertness and resolution of confusion.     * Objective Data: Pulse oximeter readings increasing to over $95\%$.

Physiology and Assessment of Pulse

• Definition: The pulse is the tactile beating of the heart as felt through the arteries as they move blood away from the heart.
• Expected Range: The normal pulse range for an adult is $60$ to $100\,\text{beats per minute (bpm)}$.
• Factors Influencing Pulse Rate     * Body Position: Moving/walking increases the rate compared to resting/lying down.     * Age: Pulse rate typically decreases with age.     * Basal Activity Level:         * Decreasing overall activity level over time causes the baseline pulse to go up.         * Athletes: Often have a decreased resting heart rate ($Bradycardia$). Rates of $44\,\text{bpm}$, $48\,\text{bpm}$, or $52\,\text{bpm}$ can be normal for highly athletic individuals because their heart pumps more efficiently with each beat.     * Health Conditions and Temperature: Hypertension can increase heart rate, and fever (high body temperature) also increases the heart rate.

The Eight Major Pulse Sites

1. Carotid: Located on either side of the neck between the trachea and the sternocleidomastoid muscle. Used primarily in CPR and emergency situations as it is a central pulse and remains palpable longer than peripheral pulses.
2. Temporal: Located at the temples, lateral to the eyes. Most commonly used in infants because their skin is thin enough to see the pulsation.
3. Brachial: Located in the antecubital fossa (the inside of the elbow). This site is used as the marker for placing blood pressure cuffs.
4. Radial: Located on the thumb side of the wrist. This is the most common site for routine vital sign checks.
5. Femoral: Located in the groin, midway between the hip and pubic bone. Requires deeper palpation due to muscle/fat tissue. Used for CPR (by some providers), central line access, and cardiac catheterization.
6. Popliteal: Located behind the knee, slightly toward the midline (the side of the big toe). Used to assess blood flow to the lower extremities, specifically for patients with diabetes or those with Below the Knee Amputations (BKA) to check the health of the stump tissue.
7. Posterior Tibial: Located behind the ankle. Useful for assessing circulation to the foot.
8. Dorsalis Pedis: Located on the top of the foot between the first and second metatarsals. This pulse is often faint and may require a Doppler to locate.

Grading Pulse Strength

Pulses are graded on a scale from $0$ to $4$ based on the strength/force of the beat, not the rate:

• $0$: Absent (dead or limb requires immediate amputation; no perfusion).
• $1$: Weak (thready, hard to palpate).
• $2$: Normal (expected strength, easily felt with light pressure).
• $3$: Strong.
• $4$: Bounding (visible pulsation through the skin, common in bodybuilders or during intense exertion, but generally puts too much pressure on vessels).

Advanced Pulse Assessment: Tachycardia and Bradycardia

• Tachycardia: Heart rate greater than $100\,\text{bpm}$.     * Causes: Exercise, anxiety, fever, pain, hypoxia, hyperthyroidism.     * Stimulants: Caffeine (coffee, tea, Celsius), nicotine, cocaine, and chocolate (especially dark chocolate which contains caffeine).     * Symptoms: Racing feeling in the chest or anxiety-like sensations.
• Bradycardia: Heart rate less than $60\,\text{bpm}$.     * Causes: Congenital abnormalities, heart failure, heart muscle damage (post-MI/heart attack), hypothyroidism.     * Valsalva Maneuver: The process of bearing down or exhaling with the mouth closed. This triggers the vagus nerve and drops the heart rate. Patients often accidentally activate this while straining on the toilet, causing them to pass out.     * Symptoms: Dizziness, fatigue, Shortness of Breath (SOB), chest pain, and confusion.

Pulse Deficit Assessment

• Definition: A pulse deficit occurs when the peripheral pulse rate is different from the heart's actual beat rate, indicating perfusion issues.
• Procedure:     1. Requires two nurses.     2. One nurse listens to the Apical Pulse using a stethoscope for one full minute.     3. The second nurse palpates the Radial Pulse simultaneously for the same minute.
• Apical Pulse Site: Located on the patient's left side, midclavicular line, at the fifth intercostal space (between the ribs).
• Interpretation: A difference of $5$ or more between the apical and radial pulses is concerning and requires rechecking and reporting to a physician or RN.

Blood Pressure (BP) Fundamentals

• Systolic Blood Pressure (SBP): The top number; measures the maximum force when the heart pumps blood out.
• Diastolic Blood Pressure (DBP): The bottom number; measures the pressure when the heart is relaxed and refilling.
• Standard Target: Traditionally $120/80\,\text{mmHg}$ according to textbooks. However, the American Cardiological Association now leans toward $115/75\,\text{mmHg}$ to prevent kidney damage. $120\text{s}$ are increasingly flagged as prehypertensive.
• BP Cuff Sizing Rules:     * Length: Should be about $80\%$ of the patient's arm circumference.     * Width: Should be about $40\%$ of the patient's arm circumference.
• Placement and Contraindications:     * Place the cuff above the antecubital fossa (AC), lining the "artery" marker with the brachial artery.     * Left side is preferred (direct line to the heart).     * Contraindications: Avoid arms with IVs, dialysis access (fistulas/grafts), history of breast cancer (mastectomy), or lymphedema.
• Measurement Errors:     * Arm position: Too low causes a false low reading; too high causes a false high reading. Arm should be at heart level.     * Cuff Sizing:         * Cuff too small/tight: Causes a false high reading.         * Cuff too large: Causes a false low reading.

Questions & Discussion

• Q: Does marijuana affect heart rate?     * A: It is generally considered a nervous system depressant and can slow the body down, though its effects on different systems are complex. It also naturally lowers and regulates blood sugar.
• Q: Does pulse grade change the rate?     * A: No. The grade ($0$-$4$) reflects strength, while the rate ($\text{bpm}$) reflects the speed of the heartbeat.
• Q: What is an AKA and BKA?     * A: AKA stands for Above the Knee Amputation; BKA stands for Below the Knee Amputation. The popliteal pulse is vital for BKA patients to ensure the stump is perfusing.
• Q: Can you take BP on a patient lying on their side?     * A: It is not ideal for an accurate reading. The patient should be sitting up or lying back to ensure an accurate measurement.
• Q: How do I find the Apical Pulse?     * A: Find the left midclavicular line (midpoint of the collarbone) and count down to the fifth intercostal space.