The Pulmonary Circulation and Pulmonary Vascular Disease Flashcards Preview

Pulmonology > The Pulmonary Circulation and Pulmonary Vascular Disease > Flashcards

Flashcards in The Pulmonary Circulation and Pulmonary Vascular Disease Deck (18):
1

Describe the major functions of the pulmonary circulation

The pulmonary circulation sits between the right and left ventricles. Its main function is to facilitate the delivery of blood under low pressure to the microcirculation which allows for adequate exchange of carbon dioxide and oxygen. It also contributes to water and solute balance in the lung

2

Describe the major determinants of blood flow distribution in the lung

Three pressures are important in determining pulmonary blood flow: 1) alveolar pressure (PA), 2) pulmonary arterial pressure (Pa), and 3) pulmonary venous pressure (Pv). The relative magnitude of these pressures passively regulates pulmonary blood flow and has traditionally been classified into three different physiologic zones

3

Define the three physiologic zones of the lung

Zone 1: the region where PA exceeds Pa which in turn exceeds Pv (PA> Pa> Pv). Blood flow is minimal. In an upright person this can be found in the apices of the lung, but is minimal in a healthy individual

Zone 2: part of the lung in which pulmonary arterial pressure exceeds alveolar pressure, but alveolar pressure exceeds venous pressure (Pa> PA> Pv). The driving pressure is the difference between arterial and alveolar pressure. Flow is greater than in zone 1, but less than in zone 3

Zone 3: part of the lung in which pulmonary arterial and venous pressure exceeds alveolar pressure (Pa> Pv> PA). The driving pressure is the difference between arterial and venous pressure without contribution from alveolar
pressure. The region of greatest blood flow.

4

Explain determinants of water and solute balance in the lung

The hydrostatic pressure gradient (Pmv-Pi) drives fluid from the pulmonary microcirculation into the interstitium. The hydrostatic pressure gradient is opposed by the oncotic pressure gradient (∏mv -∏i) which favors movement in the opposite direction (back into the microcirculation).

The filtration coefficient (Kf) determines the relationship between the net driving pressure and the rate of flow of fluid across the endothelium (high K= porous)

The osmotic reflection coefficient (σ) determines the relative contribution of the oncotic pressure gradient to the net driving pressure across the endothelial membrane.

5

Define pulmonary hypertension and its causes

A pulmonary hypertension is a pathologic state characterized by an increase in pulmonary arterial pressure as a consequence of an increased resistance to blood flow through the lungs

Normal pulmonary arterial pressure is 25/10 mmHg with a mean of 15 mmHg. Elevation of mean pulmonary pressure above 25mmHg is diagnostic of pulmonary hypertension

6

Recognize the Dana-Point classification of pulmonary hypertension

Group 1 pulmonary arterial hypertension (PAH)
Group 1’ pulmonary veno-occlusive diseases (PVOD)
Group 2 PH due left heart diseases
Group 3 PH due to hypoxic lung diseases
Group 4 PH due to pulmonary thrombo- embolism
Group 5 PH due multifactorial mechanism

7

Describe the therapeutic treatment options for PAH

There are currently 3 classes of FDA-approved medications for the treatment of PAH (4 if you include calcium channel blockers). All are pulmonary artery vasodilators, thus decreasing right ventricular afterload and improving right heart function
1) Endothelin pathway (ER-a and ER-b)
2) Nitric oxide pathway (mediated via cGMP) phosphodiesterase-5 (PDE5) inhibitors (PDE5i)
3) Prostacyclin pathway: upregulate cAMP
4) Calcium channel blockers

8

Explain determinants of water and solute balance in the lung

x

9

Explain determinants of water and solute balance in the lung and types of pulmonary edema

x

10

Define pulmonary hypertension and its causes

x

11

Recognize the Dana-Point classification of pulmonary hypertension

x

12

Describe the clinical presentation, diagnostic evaluation and treatment of acute pulmonary embolism.

x

13

Describe the therapeutic treatment options for PAH

x

14

Hemodynamic pulmonary edema

Also called hydrostatic or cardiogenic pulmonary edema
Lung is overwhelmed by modest increases in pulmonary vascular pressure. The most common cause is acute or chronic left heart failure. Renal failure can result in hemodynamic pulmonary edema if the ability of the
kidneys to excrete urine is reduced.

Usually diagnosed by a correlation of clinical findings with characteristic chest radiographic abnormalities. The patient
complains of dyspnea on exertion and orthopnea. Treatment is diuretics.

15

Permeability Pulmonary Edema

Also called non-cardiogenic or non-hydrostatic pulmonary edema. Due to increased permeability is caused by acute widespread injury to the pulmonary microvascular endothelium. Acute injury to the pulmonary microcirculation increases the filtration coefficient (Kf) and decreases the osmotic reflection coefficient (σ) so that fluid leaks into the lungs at a rate that is disproportionately high relative to the net driving / hydrostatic pressure

Presents 6-24 hours after acute lung injury. Diuretics are NOT effective

16

Describe the diagnostic evaluation of acute pulmonary embolism.

CXR is most often normal. Areas of atelectasis or a pleural effusion may be seen. Occasionally a wedge shaped infiltrate representing an infarct, called “hampton’s
hump”. The EKG may be helpful in suggesting RV strain, but most commonly only shows tachycardia. Laboratory tests include an increased A-a gradient (on arterial blood gas) suggesting alterations in V/Q ratio. Positive D-dimer.

The "Gold standard" is pulmonary angiography. Can also do CT or Echo

17

Describe the treatment of acute pulmonary embolism.

heparin and warfarin
Thrombolytic therapy is generally considered for patients with significant hemodynamic compromise and/or evidence of acute right heart strain
inferior vena caval filter or acute surgical thrombectomy

18

Describe the clinical presentation of acute pulmonary embolism.

On history, the presence of shortness of breath, chest pain, and hypoxemia is unfortunately non-specific.