WBR0990: Difference between revisions
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|Explanation=In this question we are asked to calculate the pulmonary vascular resistance for this patient. Recall that the resistance of a vessel can be calculated by the change in pressure across the segment divided by the flow (R=P/Q). Generally, the pulmonary capillary wedge pressure is a good estimate of the pressure in the left atrium. Therefore, pulmonary vascular resistance is given by the formula: | |Explanation=In this question we are asked to calculate the pulmonary vascular resistance for this patient. Recall that the resistance of a vessel can be calculated by the change in pressure across the segment divided by the flow (R=P/Q). Generally, the pulmonary capillary wedge pressure is a good estimate of the pressure in the left atrium. Therefore, pulmonary vascular resistance is given by the formula: | ||
[[File:PVREqn101814.png]] | |||
Plugging in values from the above case we get the following: | Plugging in values from the above case we get the following: | ||
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Normal values for pulmonary vascular resistance range from 0.25–1.6 mmHg·min/L. | Normal values for pulmonary vascular resistance range from 0.25–1.6 mmHg·min/L. | ||
|AnswerA=0.72 mmHg·min/L | |AnswerA=0.72 mmHg·min/L | ||
|AnswerAExp= | |AnswerAExp=See calculation in the explanation | ||
|AnswerB=1.39 mmHg·min/L | |AnswerB=1.39 mmHg·min/L | ||
|AnswerBExp= | |AnswerBExp=See calculation in the explanation | ||
|AnswerC=11.25 mmHg·min/L | |AnswerC=11.25 mmHg·min/L | ||
|AnswerCExp= | |AnswerCExp=See calculation in the explanation | ||
|AnswerD=13.9 mmHg·min/L | |AnswerD=13.9 mmHg·min/L | ||
|AnswerDExp= | |AnswerDExp=This result can be achieved by dividing the difference in systolic and diastolic aortic pressures and dividing by the cardiac output (3.6L/min) | ||
|AnswerE=20.83 mmHg·min/L | |AnswerE=20.83 mmHg·min/L | ||
|AnswerEExp= | |AnswerEExp=See calculation in the explanation | ||
|EducationalObjectives=Pulmonary vascular resistance is given by the change in pressure across the pulmonary vasculature divided by the cardiac output. | |EducationalObjectives=Pulmonary vascular resistance is given by the change in pressure across the pulmonary vasculature divided by the cardiac output. | ||
|References=First Aid 2014 page 599 | |References=First Aid 2014 page 599 | ||
Revision as of 00:20, 20 October 2014
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Pulmonology |
| Prompt | [[Prompt::An attending in the cardiac intensive care unit at major academic medical center is teaching a resident about the pulmonary vasculature. A patient with a history of hypertrophic cardiomyopathy is recovering from an anterior myocardial infarction and the following values are measured.
Pulmonary artery pressure (mean): 15 Pulmonary capillary wedge pressure (mean): 10 Aortic systolic pressure: 140 Aortic diastolic pressure: 90 Heart rate: 90 per minute Stroke Volume: 40 mL Which of the following corresponds to the pulmonary vascular resistance in this patient?]] |
| Answer A | AnswerA::0.72 mmHg·min/L |
| Answer A Explanation | AnswerAExp::See calculation in the explanation |
| Answer B | AnswerB::1.39 mmHg·min/L |
| Answer B Explanation | AnswerBExp::See calculation in the explanation |
| Answer C | AnswerC::11.25 mmHg·min/L |
| Answer C Explanation | AnswerCExp::See calculation in the explanation |
| Answer D | AnswerD::13.9 mmHg·min/L |
| Answer D Explanation | AnswerDExp::This result can be achieved by dividing the difference in systolic and diastolic aortic pressures and dividing by the cardiac output (3.6L/min) |
| Answer E | AnswerE::20.83 mmHg·min/L |
| Answer E Explanation | AnswerEExp::See calculation in the explanation |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::In this question we are asked to calculate the pulmonary vascular resistance for this patient. Recall that the resistance of a vessel can be calculated by the change in pressure across the segment divided by the flow (R=P/Q). Generally, the pulmonary capillary wedge pressure is a good estimate of the pressure in the left atrium. Therefore, pulmonary vascular resistance is given by the formula:
Plugging in values from the above case we get the following: (15 mmHg - 10 mmHg)/(90 beats/minute*(.040 L/min))=5/3.60=1.39 mmHg·min/L.
|
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Lung, WBRKeyword::Vasculature, WBRKeyword::Pulmonary hypertension, WBRKeyword::Hemodynamics, WBRKeyword::Hemodynamic |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
