From the Guidelines
Pulmonary artery catheter pressures are interpreted by analyzing several key measurements that reflect cardiac function and volume status, with a focus on right atrial pressure, pulmonary artery pressure, and pulmonary artery wedge pressure, as outlined in the 2016 European Society of Cardiology guidelines 1. To interpret these values, first assess right atrial pressure (RAP) which reflects right heart preload and central venous pressure. Next, evaluate pulmonary artery pressure (PAP) which indicates pulmonary vascular resistance and left heart function. The pulmonary artery wedge pressure (PAWP) serves as a surrogate for left atrial pressure and left ventricular end-diastolic pressure, reflecting left heart preload.
- Key measurements include:
- Right atrial pressure (RAP, normal 2-6 mmHg)
- Pulmonary artery pressure (PAP, normal 15-30/8-15 mmHg)
- Pulmonary artery wedge pressure (PAWP, normal 6-12 mmHg)
- Cardiac output can be calculated using thermodilution techniques, with normal values ranging from 4-8 L/min, as noted in the study on acute heart failure 1. Elevated RAP suggests right heart failure or volume overload, while elevated PAWP indicates left heart failure or volume overload. A significant difference between PAP and PAWP (>10-12 mmHg) suggests pulmonary hypertension, as defined in the 2016 guidelines for the diagnosis and treatment of pulmonary hypertension 1. When interpreting these values, always consider them in the clinical context of the patient's condition, including their volume status, cardiac function, and response to interventions, rather than relying solely on isolated numbers, as emphasized in the study on experts' opinion on management of hemodynamics in ARDS patients 1.
From the Research
Interpreting PA Catheter Pressures
PA catheter pressures are interpreted to determine the etiology of various conditions such as shock, lactic acidosis, and pulmonary edema, as well as to guide fluid and vasoactive therapy 2. The interpretation of these pressures requires a thorough understanding of the indications, contraindications, complications, and pitfalls of data interpretation.
Key Considerations
- The pulmonary artery catheter (PAC) provides hemodynamic data that is widely used diagnostically and therapeutically in the care of critically ill patients 2.
- The use of the PAC has not been shown to provide outcomes benefit, and there is some evidence to suggest that placement of the PAC may actually be detrimental 2.
- The classical PAC has evolved to provide continuous data on cardiac output, oxygen supply and-demand balance, as well as right ventricular (RV) performance 3.
- The interpretation of waveforms and other data obtained from the PAC requires careful analysis to avoid misinterpretation, which can lead to incorrect diagnosis and treatment 2, 3.
Waveform Analysis
- The dicrotic notch pressure has been shown to be closely related to mean pulmonary artery pressure in critically ill patients, and can be used as a reliable indicator of mean PA pressure 4.
- The use of a Swan-Ganz catheter can provide accurate measurements of mean PA pressure and dicrotic notch pressure, and can help to identify unsuspected distal catheter migration 5, 4.
- The size of the catheter used can affect the pressures recorded in small pulmonary veins, and smaller catheters may provide more accurate measurements 6.
Clinical Applications
- PA catheter pressures can be used to guide fluid and vasoactive therapy in critically ill patients 2.
- The PAC can provide valuable information on cardiac output, oxygen supply and-demand balance, and right ventricular performance, which can help to inform treatment decisions 3.
- The use of a PAC can help to identify complications such as pulmonary hypertension and cardiac abnormalities, and can guide treatment to prevent these complications 2.