 | Prep for USMLE |
| Forum | Resources | New Posts | Register | Login | » |
|
| Author | 4 Posts | |||||||||||||||||||||||||||||||
|
kris2c
Forum Senior Topics: 30 Posts: 108 |
A balloon-tipped catheter is placed into a small branch of the pulmonary artery in a patient. The lumen of the catheter opens distal to the balloon. The pressure measured from the catheter with the balloon deflated is 25/8 mm Hg. When the balloon is inflated, the pressure is 7 mm Hg and non-pulsatile. Which of the following pressures is being approximated when the balloon is inflated? A. Left atrial pressure B. Left ventricular end diastolic pressure C. Left ventricular peak systolic pressure D. Pulmonary artery pressure E. Right atrial pressure
|
Prep4USMLE.com
|
Advertisement
|
|
peekay
| Forum Guru Topics: 102 Posts: 587
D- PULMONARY ARTERY PRESSURE..
|
auubar
| Forum Senior Topics: 30 Posts: 182
left atrial pressure
|
kris2c
| Forum Senior Topics: 30 Posts: 108
The correct answer is A. When the balloon is deflated, the catheter simply measures the pulmonary artery pressure (choice D), which is pulsatile with systolic/diastolic values of 25/8 mm Hg. When the balloon is inflated, the catheter is "wedged" in a small branch of the pulmonary artery and the pressure that is measured is called the "pulmonary wedge pressure." Because inflation of the balloon obstructs all blood flow in the artery branch, the blood vessels distal to the point of obstruction also have no flow. One can think of these distal vessels as physical extensions of the catheter, as they allow blood pressure to be measured on the other side of the pulmonary circulation, i.e., in the left atrium. The pulmonary wedge pressure is usually a few mm Hg higher compared to the left atrial pressure, but the general opinion is that pulmonary wedge pressure is a reflection of events in the left atrium. It is usually not feasible to measure left atrial pressure directly in the normal human being because it is difficult to pass a catheter retrograde through the aorta and left ventricle. Therefore, the pulmonary wedge pressure provides an important clinical estimate of left atrial pressure. Be aware that pulmonary wedge pressure may also be called pulmonary capillary wedge pressure, pulmonary arterial wedge pressure, or simply wedge pressure. In many instances, the pulmonary wedge pressure can provide a reasonable estimate of left ventricular end diastolic pressure (choice B). However, a notable exception is during "mitral stenosis", in which the pressure in the left atrium (and therefore, the pulmonary wedge pressure) is much higher than the left ventricular end diastolic pressure because of the high resistance to blood flow through the stenosed valve. The left ventricular peak systolic pressure (choice C) occurs when the mitral valve is closed, making it impossible to be approximated using a catheter in the pulmonary artery. The right atrial pressure (choice E) cannot be measured or approximated from a catheter in the pulmonary artery.
|
|
| | |||||||||||||||||||
|
This thread is closed, so you cannot post a reply.
 Similar forum topicsCARDIO...... CARDIO......A pt. of acute MI CARDIO......A pt. of atrial fib.... | Related resources |
Advertise | Support | Premium | Contact |
Your Privacy Choices