Pulmonary hypertension/Repetitorium

Pulmonary hypertension is a chronic increase in mean capillary pressure in the pulmonary artery above 22 torr (mmHg). This happens due to increased resistance or flow in the pulmonary basin.

Division

precapillary vs. postcapillary
acute vs. chronic

Physiology of the pulmonary canal

The pulmonary canal is a low-pressure system into which the heart pumps blood at a pressure of 25 torr from the right ventricle through the pulmonary artery. In diastole, the pressure drops to about 5 torr; therefore, the mean pressure in the lung is 15 torr. On the venous side of the river bed, the pressure is equal to the pressure in the left heart atrium. Since direct pressure measurement in the left atrium is difficult to implement for practical reasons, an approximation is used, the so-called wedging pressure (direct pressure measurement at the level of the last arteriole in which the catheter is "wedged"). Under physiological circumstances, the wedging pressure reaches about 5 torr. If there is an increase in pressure in any (arterial or venous) part of the riverbed, we speak of Pulmonary arterial hypertension. This condition tends to spread to the entire river basin. Unlike the systemic circulation, where hypoxia leads to vasodilation, the pulmonary vessels contract in response to the reduced partial pressure of O 2 , thereby increasing the resistance to blood flow in the given area, and this is subsequently redirected to the part with a higher p O 2 (hypoxic pulmonary Vasoconstriction).

Precapillary pulmonary hypertension

Acute

pulmonary embolism

Chronic

Congenital heart defects (defects with left-right shunt)

obstructive and restrictive lung diseases (combination of changes in the mechanical properties of the lungs, destruction of the pulmonary bed, alveolar hypoxia → hypoxic pulmonary vasoconstriction, alveolar hypercapnia, increased blood viscosity − compensatory polyglobulia at chronically reduced p O2)
morphological changes of pulmonary vessels
compensatory formation in postcapillary pulmonary hypertension

Postcapillary pulmonary hypertension

left heart failure
venous congestion in the lungs (pulmonary edema )
asthma cardiale: attacks of shortness of breath (especially at night) in patients with heart failure

Consequences of pulmonary hypertension on the systemic circulation

Cor pulmonale: hypertrophy and dilatation of the right heart caused by chronic arterial hypertension in the pulmonary artery as a result of lung disease (cor pulmonale chronicum). Cor pulmonale acutum: pulmonary embolism leads to acute failure of the right heart, which is unable to "push" blood through the obstruction.

Links

Source

VÍZEK, Martin. Repetitorium [online]. [cit. 2012-01-08]. <https://web.archive.org/web/20130512032641/http://pf.lf2.cuni.cz/vyuka/repetitorium.html>.

References

GUYTON, Arthur C – HALL, John E. Textbook of Medical Physiology. 11. edition. Elsevier, 2006. 0 pp. 11; ISBN 978-0-7216-0240-0.