Cardiopulmonary Rehabilitation, Tilt-Table Testing & Hemodynamic Monitoring

Objectives 4.1 / 5.1 / 6.1 — Understand VO2 max, cardiac rehab phases, tilt-table testing, hemodynamic catheter types and placement, normal pressure values, and calculations for CO, CI, SVR, and PVR.

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Unit 4: Cardiopulmonary Rehabilitation

Importance of Cardiopulmonary Rehabilitation

Exercise training was introduced after the 1950s, undoing the restricted physical activity that had previously been prescribed after cardiac surgeries.

Key benefits of cardiac rehabilitation:

• 15% reduction in mortality and recurrent myocardial infarctions in patients who exercise
• Counseling to improve psychological well-being
• Reduced cigarette smoking
• Increased adherence to medications and diet

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VO2 Max

VO2 max is the maximal amount of oxygen that an individual can transport during exercise before being limited by fatigue or dyspnea.

• An easily reproducible test that allows the healthcare provider to indirectly measure maximal cardiac pump capacity
• VO2 is directly related to Q (cardiac output) and SV (stroke volume)

Exercise and VO2 Max

Exercise has a direct link to an individual's VO2 max. During cardiac rehabilitation:

• Regular exercise training increases VO2 max
• This also increases VO2 submaximal, which decreases dyspnea and fatigue during everyday activities

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Cardiac Rehabilitation Phases

Cardiac rehabilitation is divided into three phases based on the patient's clinical status. Activities include walking, jogging, and basic light weights/resistance training for approximately 20 minutes, 3 times per week throughout the different phases.

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Unit 5: Tilt-Table Testing

Purpose

The tilt-table test identifies patients who have a vasodepressor or cardio-inhibitory response as a cause of syncope (passing out when standing too quickly due to a heart condition or vasovagal response).

Orthostatic hypotension is one of the primary causes of syncope while standing up and can be determined by tilt-table testing.

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Procedure

1. Patient is placed on a tilt table in the supine position
2. The table is tilted upright to a maximum of 60–80 degrees for 20–45 minutes
3. If there is no reaction to the tilt:
   • Intravenous isoproterenol may be administered as a bolus to provoke syncope
   • Causes a vasodepressor response (decrease in heart rate and blood pressure)

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Unit 6: Hemodynamic Monitoring

Hemodynamic Catheters

Three common indwelling catheters used for hemodynamic monitoring:

Patients requiring these catheters typically have advanced cardiac disease, advanced lung disease, or massive trauma.

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Arterial Lines (A-Lines)

Arterial lines are used for:

• Obtaining arterial blood gases (ABGs)
• Continuously monitoring blood pressure

Placement: Usually inserted in the radial or femoral artery.

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Central Venous Pressure (CVP) Catheter

CVP catheters measure the pressure as blood fills the right side of the heart from the central veins (Superior/Inferior Vena Cava) — this assesses right-sided heart function.

• Access begins in large central vessels — usually the jugular vein or subclavian vein (under the clavicle)
• Also known as a "Central Line"
• The catheter tip ends in the right atrium — hence its ability to assess right-sided heart function
• Can also deliver drugs and fluids (similar to an IV)

CVP Catheter Types

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Pulmonary Artery Pressure (PAP) Catheter — Swan-Ganz

Also called a balloon-tipped flow-directed catheter. Sits within the pulmonary artery and can measure more than one pressure simultaneously.

Swan-Ganz Port Colors

PAP Catheter Indications

Helpful in identifying:

• Shock (cardiogenic, hypovolemic, septic)
• Left ventricular failure
• Myocardial infarction (MI)
• Pulmonary vascular disease
• Pulmonary edema
• ARDS

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Strain-Gauge Pressure Transducer

The device that converts pressures measured by catheters into interpretable numbers is called the strain-gauge pressure transducer — the values appear on the bedside vitals monitor.

• Physical strain on the diaphragm changes the amount of electricity flowing through the wires
• By measuring changes in electrical flow, there is an indirect measurement of pressure

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Hemodynamic Pressure Values

MAP — Mean Arterial Pressure

Measured via an A-line.

MAP Evaluation:

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CVP — Central Venous Pressure

• Measures right atrial preload — the pressure as blood fills the right side of the heart
• Preload is the pressure that stretches the chamber walls as blood fills
• Measured by CVP catheter or Swan-Ganz catheter

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PCWP — Pulmonary Capillary Wedge Pressure

• Helpful in discriminating between cardiogenic and non-cardiogenic pulmonary edema (e.g., ARDS)
• Requires the technician to inflate a balloon within the pulmonary artery
• Can be dangerous — if not deflated, it causes turbulent flow and increased likelihood of clotting

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Cardiac Output (CO)

CO = SV × HR

(Stroke Volume × Heart Rate)

• Stroke volume (SV) = volume of blood pumped out of the left ventricle per beat
• CO is measured in L/min
• Stroke volume can be measured with an echocardiogram

Thermodilution Method for CO

Swan-Ganz catheters can calculate CO using the thermodilution method:

1. A solution of 10 mL dextrose (D5W) or saline is injected
2. The solution travels through the normal pathway of the heart
3. Because the solution is cooler than blood, a temperature difference is recorded
4. This temperature difference is used to calculate CO

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Cardiac Index (CI)

CI = CO ÷ BSA

(Cardiac Output ÷ Body Surface Area)

• Used to determine if the heart is supplying the body with enough oxygen and nutrients
• A more accurate indicator of cardiac function than CO alone

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SVR & PVR

Systemic Vascular Resistance (SVR) and Pulmonary Vascular Resistance (PVR) calculate the resistance to blood flow through the systemic and pulmonary circulations, respectively.

The factor 80 is used as a correction factor to convert mmHg into dynes·sec/cm⁵ — the standard unit for vascular resistance.

Formulas

Variable Key