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Swan-Ganz catheterization: Interpretation of tracings

INTRODUCTION

The flow-directed pulmonary artery catheter (ie, Swan-Ganz catheter) permits the clinician to measure pressures and sample blood from the right atrium, right ventricle, and pulmonary artery [1,2]. In addition, the left atrial pressure can be indirectly measured by inflating a balloon at the tip of the catheter and allowing the balloon to occlude a branch of the pulmonary artery. The pressure measured during occlusion is an indirect assessment of the left atrial pressure. It is called the pulmonary artery wedge pressure, pulmonary artery occlusion pressure, or pulmonary capillary wedge pressure.

Pulmonary arterial catheterization is used for the diagnosis and management of a range of conditions in critically ill patients (table 1). Observation of pressure waveforms permits assessment of mechanical events related to the atria and ventricles, intravascular volume status, cardiac tamponade, cardiac constriction, restrictive cardiomyopathy, mitral valvular regurgitation, tricuspid valvular regurgitation, and intracardiac shunts (eg, atrial or ventricular septal defects). In addition, it may differentiate among the types of shock (eg, cardiogenic, distributive, hypovolemic) and identify etiologies of respiratory and cardiac failure.

The effect of invasive hemodynamic monitoring on outcomes in critical illness is controversial [3-6]. As a result, use of the pulmonary artery catheter has declined in the United States [7]. The impact of pulmonary artery catheterization on outcomes is discussed separately. (See "Swan-Ganz catheterization: Indications and complications", section on 'Effect on survival'.)

Interpretation of Swan-Ganz catheter pressure tracings is described here. Indications, catheter insertion, risks, benefits, efficacy, and outcomes are presented separately. (See "Insertion of Swan-Ganz catheters" and "Swan-Ganz catheterization: Indications and complications".)

ZEROING AND REFERENCING

The catheter must be appropriately zeroed and referenced for accurate diagnostic information to be obtained. Although zeroing and referencing are done in one step, they represent two separate processes:
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