7.2 Respiration & Blood Pressure Assessment

7.2 Respiration & Blood Pressure Assessment

Core Clinical Mandate: Respiratory and blood pressure assessments measure pulmonary gas exchange and cardiovascular perfusion. Because respiration is partially controlled by the voluntary cerebral cortex, nurse aides must employ covert counting techniques to obtain an accurate, uninhibited rate. In measuring arterial blood pressure, aides must master manual sphygmomanometry—selecting precise cuff dimensions, locating the brachial artery, identifying radial obliteration pressure, inflating 30 mm Hg above obliteration, deflating at 2 to 3 mm Hg per second, and distinguishing Phase I and Phase V Korotkoff sounds—while enforcing strict limb contraindications.

Respiration Physiology, Terminology, and Covert Assessment

Respiration is the physiological process of gas exchange between the atmosphere and the body's cells, comprising the intake of oxygen ($O_2$) and the elimination of carbon dioxide ($CO_2$). One single respiration cycle consists of two distinct mechanical phases:

1. Inspiration (Inhalation): The diaphragm contracts and flattens downward while external intercostal muscles expand the rib cage upward and outward, creating negative intrathoracic pressure that pulls air into the lungs (chest rises).
2. Expiration (Exhalation): The diaphragm and intercostal muscles relax, allowing the elastic recoil of lung tissue to compress intrathoracic volume and expel air passively (chest falls).

Clinical Respiratory Terminology

• Normal Adult Resting Rate: 12 to 20 breaths per minute (bpm), characterized by regular, quiet, effortless, and unlabored movement.
• Eupnea: Normal, relaxed, rhythmic breathing within the 12 to 20 breaths/min range.
• Tachypnea: Abnormally rapid respiratory rate exceeding 20 breaths per minute. Associated with fever, pneumonia, asthma exacerbation, pulmonary embolism, hypoxemia, congestive heart failure, diabetic ketoacidosis, acute pain, and severe anxiety.
• Bradypnea: Abnormally slow respiratory rate below 12 breaths per minute. Associated with central nervous system depression, narcotic/opioid analgesics (e.g., morphine, oxycodone), sedatives, severe head trauma, increased intracranial pressure, and hypothermia.
• Apnea: The complete absence or temporary cessation of breathing. Periods of apnea lasting longer than 4 to 6 minutes lead to irreversible hypoxic brain death.
• Dyspnea: Difficult, painful, or labored breathing accompanied by a subjective sensation of severe shortness of breath ('air hunger'). Objective signs include nasal flaring, pursed-lip breathing, cyanosis, and the use of accessory neck and intercostal muscles.
• Orthopnea: The inability to breathe comfortably in a recumbent (flat or supine) posture. Residents with orthopnea require multiple pillows or must sit upright in High-Fowler's or the orthopneic position (leaning forward over a padded overbed table) to expand lung volume.
• Cheyne-Stokes Respirations: An irregular, cyclical breathing pattern characterized by a gradual increase in the rate and depth of breathing (crescendo), followed by a gradual decrease in rate and depth (decrescendo), terminating in a prolonged period of apnea lasting 10 to 60 seconds before the cycle repeats. Commonly observed in severe congestive heart failure, severe stroke, increased intracranial pressure, and as a classic sign of impending death during the active dying process.
• Kussmaul Respirations: Abnormally deep, rapid, sighing breaths without pause, characteristic of severe metabolic acidosis (classically diabetic ketoacidosis / DKA) as the body attempts to blow off volatile carbonic acid / carbon dioxide.
• Cyanosis: A bluish or dusky slate-gray discoloration of the skin, nail beds, lips, tongue, and oral mucous membranes resulting from excessive deoxygenated hemoglobin in the blood, indicating tissue hypoxia.

The CNA Covert Counting Technique

Unlike pulse or body temperature, respiration is controlled by both involuntary centers in the brainstem (the medulla oblongata and pons, which monitor arterial carbon dioxide and pH levels) and voluntary pathways in the cerebral cortex. If a resident becomes conscious that a caregiver is observing and counting their breathing, they will involuntarily or intentionally alter their breathing pattern—holding their breath, breathing deeper, or breathing faster.

To prevent this conscious alteration, the Certified Nurse Aide must use the covert counting technique:

1. Measure the resident's radial pulse as usual.
2. When the 30- or 60-second pulse count is finished, do NOT remove your fingers from the resident's wrist, do not alter your posture, and do not announce that you have finished taking the pulse.
3. Keep your fingers resting lightly over the radial artery (or gently rest the resident's arm or your hand across the resident's upper chest/shoulder) and unobtrusively shift your gaze toward the resident's chest and abdomen.
4. Observe the rise and fall of the chest wall. Count one full rise (inhalation) and one full fall (exhalation) as one single breath.
5. If respirations are regular and rhythmic, count for 30 seconds and multiply by 2. If breathing is irregular, labored, shallow, noisy (wheezing, stridor, or stertorous), or if performing an initial admission baseline assessment, count for a full 60 seconds.
6. Assess respiratory characteristics: Rate (breaths/min), Depth (normal, shallow, or deep), and Rhythm (regular vs. irregular).

Blood Pressure Physiology and AHA Classifications

Blood pressure (BP) is the lateral hydrodynamic force exerted by circulating blood against the internal walls of systemic arterial vessels during the cardiac cycle. It is determined by two hemodynamic variables: Cardiac Output (stroke volume multiplied by heart rate) and Systemic Vascular Resistance (the diameter and elasticity of arterial blood vessels).

Blood pressure is expressed as a fraction in millimeters of mercury (mm Hg):

• Systolic Blood Pressure (Top Number): The maximum pressure generated within the arterial tree during left ventricular contraction (systole), forcing a stroke volume of blood through the aortic valve into systemic circulation.
• Diastolic Blood Pressure (Bottom Number): The minimum baseline pressure sustained within the arterial system during left ventricular relaxation and filling (diastole), reflecting continuous vascular resistance and arterial recoil.
• Pulse Pressure: The mathematical difference between the systolic and diastolic pressures (e.g., in a BP of 120/80 mm Hg, the pulse pressure is 120 - 80 = 40 mm Hg).

American Heart Association (AHA) Blood Pressure Classifications

+---------------------------------------------------------------------------------------------------------+
|                                 AHA / ACC BLOOD PRESSURE CLASSIFICATIONS (ADULTS)                       |
+-----------------------+-----------------------------+-----+---------------------------------------------+
| Category              | Systolic Reading (mm Hg)    |     | Diastolic Reading (mm Hg)                   |
+-----------------------+-----------------------------+-----+---------------------------------------------+
| Normal                | Less than 120               | AND | Less than 80                                |
| Elevated              | 120 – 129                   | AND | Less than 80                                |
| Hypertension Stage 1  | 130 – 139                   | OR  | 80 – 89                                     |
| Hypertension Stage 2  | 140 or higher               | OR  | 90 or higher                                |
| Hypertensive Crisis   | Higher than 180             | AND/| Higher than 120                             |
|                       |                             | OR  | (Immediate emergency intervention required) |
+-----------------------+-----------------------------+-----+---------------------------------------------+

• Hypotension: Abnormally low blood pressure, standardly defined as a systolic reading less than 90 mm Hg and/or a diastolic reading less than 60 mm Hg. Symptoms include dizziness, lightheadedness, syncope (fainting), blurred vision, cold clammy skin, pallor, confusion, and reduced renal perfusion.
• Orthostatic (Postural) Hypotension: A sudden drop in systemic blood pressure that occurs when a resident rapidly changes position from lying down (supine) to sitting or standing. Gravitational pooling of blood in lower extremity capacitance veins reduces venous return to the heart, leading to cerebral hypoperfusion and high fall risk.
  • Diagnostic Criteria: A drop of ≥ 20 mm Hg in systolic blood pressure OR a drop of ≥ 10 mm Hg in diastolic blood pressure within 3 minutes of standing, accompanied by dizziness or compensatory tachycardia.
  • Assessment Protocol: Have the resident lie flat in bed for 5 minutes, then record BP and pulse. Have the resident sit on the edge of the bed with feet dangling; wait 1 to 3 minutes, then record BP and pulse. Assist the resident to stand; wait 1 to 3 minutes, then record BP and pulse. If the resident exhibits severe lightheadedness, immediately assist them back into a supine position with feet elevated to restore cerebral blood flow.

Manual Sphygmomanometry Technique and Korotkoff Sounds

Manual blood pressure measurement utilizes an aneroid sphygmomanometer (calibrated pressure gauge, inflatable rubber bladder, inflation bulb, and airflow release screw valve) and an acoustic stethoscope.

Equipment Sizing Rules and Measurement Errors

Selecting the correct cuff size is essential for clinical accuracy:

• Bladder Width: Must equal 40% of the mid-arm circumference.
• Bladder Length: Must encircle 80% (or 80% to 100%) of the upper arm circumference.
• Clinical Impact of Sizing Errors:
  • Cuff Too Narrow or Too Small: Requires excessive pneumatic pressure to compress the underlying brachial artery, yielding a falsely high blood pressure reading.
  • Cuff Too Wide or Too Large: Distributes pressure over an excessively broad area, yielding a falsely low blood pressure reading.
• Arm Positioning: The resident's arm must be fully supported at heart level (4th intercostal space). If the arm is positioned below heart level, hydrostatic fluid pressure adds to arterial pressure, producing a falsely high reading. If the arm is elevated above heart level, hydrostatic pressure opposes arterial flow, producing a falsely low reading.
• Leg Crossing: The resident must sit with both feet flat on the floor; crossed legs compress peripheral vasculature, elevating systolic pressure by 2 to 8 mm Hg.

The Two-Step Manual Blood Pressure Procedure

+---------------------------------------------------------------------------------------------------------+
|                                 TWO-STEP BLOOD PRESSURE ASSESSMENT PROTOCOL                             |
+---------------------------------------------------------------------------------------------------------+
| Step 1: Determine Radial Obliteration Pressure                                                          |
| - Palpate brachial artery; wrap cuff smoothly 1 inch above antecubital space.                           |
| - Palpate radial pulse while rapidly inflating cuff until pulse disappears (e.g., at 120 mm Hg).        |
| - Inflate 10 mm Hg higher to confirm, then deflate completely. Wait 30 seconds.                         |
+---------------------------------------------------------------------------------------------------------+
| Step 2: Auscultate Blood Pressure with Stethoscope                                                      |
| - Place stethoscope diaphragm lightly over brachial artery pulse (never tuck under cuff).               |
| - Rapidly inflate cuff to 30 mm Hg ABOVE obliteration pressure (e.g., 120 + 30 = 150 mm Hg).            |
|   * Rationale: Prevents underestimating systolic pressure due to an auscultatory gap.                  |
| - Open valve slowly; deflate at 2 to 3 mm Hg per second.                                                 |
| - Phase I (First clear rhythmic tapping sound)  = SYSTOLIC PRESSURE.                                    |
| - Phase V (Point of complete cessation/silence) = DIASTOLIC PRESSURE.                                   |
| - Deflate 10-20 mm Hg further to verify silence, then rapidly exhaust remaining air.                     |
+---------------------------------------------------------------------------------------------------------+

• Understanding the Auscultatory Gap: In many elderly hypertensive residents, an auscultatory gap occurs—a temporary, abnormal silent interval where Korotkoff sounds vanish below true systolic pressure and reappear at a lower pressure level. If an aide inflates the cuff to an arbitrary number (e.g., 140 mm Hg) without determining radial obliteration, they may inflate directly into the silent gap and mistake the reappearance of sound as the systolic pressure, dangerously underestimating the true systolic reading by 20 to 40 mm Hg. Inflating 30 mm Hg above the palpated obliteration pressure guarantees that inflation starts well above the true systolic pressure, completely eliminating this error.
• Korotkoff Sounds Breakdown:
  • Phase I: The onset of faint, clear, repetitive tapping sounds that gradually increase in intensity. The first tapping sound marks the Systolic Pressure.
  • Phase II: A soft swishing, murmuring, or blowing sound caused by turbulent blood flow through the partially compressed artery.
  • Phase III: Crisp, loud, distinct knocking sounds.
  • Phase IV: Distinct muffling of sounds, changing from sharp knocks to a dull, soft murmur as the artery remains open during diastole.
  • Phase V: The point of complete disappearance (cessation) of sound. This exact numerical marking denotes the Diastolic Pressure in adult residents.

Extremity Contraindications for Blood Pressure Assessment

A Certified Nurse Aide must never place a blood pressure cuff on an extremity that exhibits any of the following clinical contraindications:

1. Mastectomy with Axillary Lymph Node Dissection: Surgical excision of axillary lymph nodes impairs lymphatic drainage from the entire ipsilateral arm. Inflating a blood pressure cuff produces high compressive pressure that can crush fragile, regenerating lymphatic vessels, precipitating severe, irreversible lymphedema (chronic, disfiguring arm swelling) and secondary cellulitis. If the resident had a bilateral mastectomy, the aide must consult the charge nurse for alternative orders (e.g., thigh blood pressure measurement).
2. Arteriovenous (AV) Fistula, Shunt, or Graft for Hemodialysis: Dialysis vascular access sites involve a surgically constructed direct anastomosis between an artery and a vein. Placing a blood pressure cuff on an arm with an AV fistula compresses the fragile vascular conduit, predisposing to acute thrombosis (clotting), complete occlusion, or vessel rupture, permanently destroying the resident's access line for life-saving dialysis.
3. Active Intravenous (IV) Infusion or PICC Line: Cuff inflation exerts pressure exceeding venous pressure, causing retrograde blood flow into the IV catheter, catheter occlusion from clotting, mechanical dislocation of the cannula, or extravasation/infiltration of caustic medications into surrounding subcutaneous tissues.
4. Orthopedic Cast, Splint, or Traction: Prevents proper cuff application and vascular compression, while compressive force risks displacing healing fractures.
5. Paretic or Hemiplegic Arm (Post-Stroke / CVA): Neuromuscular denervation and impaired vasomotor tone in a stroke-affected extremity cause abnormal vascular resistance, yielding inaccurate blood pressure readings, while compromised sensory perception places the resident at risk for unnoticed tissue ischemia from cuff compression.
6. Open Wounds, Severe Burns, Cellulitis, or Skin Grafts: Increases pain and bacterial cross-contamination.