A 56-year-old woman is evaluated for fatigue and dyspnea on exertion. Past medical history includes hypertension and systemic sclerosis. Blood pressure is 135/80 mm Hg and pulse is 68/min. Cardiac examination reveals loud second heart sounds with no murmurs. Lungs are clear to auscultation. Further evaluation with a catheterization procedure is performed, during which a balloon-tipped catheter is advanced into the pulmonary artery. A branch of the pulmonary artery is occluded by the balloon, and the pressure beyond the point of occlusion is measured. The pressure reading from the procedure most likely corresponds to which of the following pressures?

Question

A 56-year-old woman is evaluated for fatigue and dyspnea on exertion.  Past medical history includes hypertension and systemic sclerosis.  Blood pressure is 135/80 mm Hg and pulse is 68/min.  Cardiac examination reveals loud second heart sounds with no murmurs.  Lungs are clear to auscultation.  Further evaluation with a catheterization procedure is performed, during which a balloon-tipped catheter is advanced into the pulmonary artery.  A branch of the pulmonary artery is occluded by the balloon, and the pressure beyond the point of occlusion is measured.  The pressure reading from the procedure most likely corresponds to which of the following pressures?

Quizplus · Accepted Answer

Pulmonary artery catheters (PACs; also called Swan-Ganz or right heart catheters) are used to diagnose pulmonary hypertension and occasionally for management of critically ill patients. During pulmonary artery catheterization, the balloon at the distal tip of the catheter is inflated, and the catheter is advanced forward through the right atrium, right ventricle, and pulmonary artery and finally into a branch of the pulmonary artery. Once lodged in a pulmonary artery branch, the inflated balloon obstructs forward blood flow, creating a continuous static column of blood between the catheter tip and left atrium. The pressure measured at the catheter tip at this time is called the pulmonary artery occlusion pressure (PAOP; or pulmonary capillary wedge pressure [PCWP]) and closely reflects left atrial and left ventricular end-diastolic pressures. (Choices A and C) Direct measurement of intrapleural pressure (pleural manometry) can be obtained by placing a catheter in the pleural space during thoracentesis, whereas mean airway pressure is measured during mechanical ventilation. PACs do not measure intrapleural or mean airway pressure. (Choice D) Mean arterial pressure is measured by placing an arterial catheter directly in central arterial circulation (common femoral or radial artery) and reflects the average aortic pressure (perfusion pressure). (Choice E) Pulse pressure refers to the difference between systemic arterial systolic and diastolic blood pressure. (Choices F and G) Right atrial and right ventricular systolic pressures can be measured directly by PACs by placing the catheter in the respective chambers. Educational objective: Pulmonary artery occlusion pressure is measured at the distal tip of the pulmonary artery catheter after an inflated balloon occludes blood flow through a pulmonary artery branch. It closely corresponds to left atrial and left ventricular end-diastolic pressure. __________ References: Catheterization of the heart in man with use of a flow-directed balloon-tipped catheter. (http://www.ncbi.nlm.nih.gov/pubmed/5434111)

A 56-Year-Old Woman Is Evaluated for Fatigue and Dyspnea on Exertion