Pulmonary vascular resistance

Of the pulmonary vascular resistance (PVR) is the flow resistance of the blood vessels in the pulmonary circulation. He will too pulmonary vascular resistance called and serves to regulate the blood flow.

What is Pulmonary Vascular Resistance?

The pulmonary vascular resistance is only around a tenth as great as the total peripheral resistance of the great body circulation. Accordingly, the arterial blood pressure in the lungs only reaches a nominal value of 20/8 mmHg.

The pulmonary circulation (small circulation) transports the blood from the heart to the lungs and returns it from there. In the process, oxygen-poor blood is enriched and the lungs are ventilated at the same time. This blood is drained from the right ventricle via both pulmonary arteries. They divide into smaller and smaller vessels and finally go into the capillaries (hair vessels).

The alveoli, which are enclosed by the hair vessels, then exchange the carbon dioxide in the blood for oxygen by diffusion. The enriched blood returns to the left atrium of the heart via the pulmonary veins. The bronchial arteries are also part of this circuit, as they supply the lungs with oxygenated blood.

When the oxygen concentration in the blood in the pulmonary arteries falls, they narrow (vasoconstriction), which increases pulmonary vascular resistance. In other areas of the lungs it decreases accordingly. The ventilation of the lungs is organized through this reciprocal mechanism.

Function & task

The vascular resistance in the lungs is dependent on the respective diameter of the vascular segment and the flow rate of the blood. The viscosity of the blood is just as important for the PVR. The longer a vessel, the greater the vascular resistance.

If the radius of a vessel halves on its way, the resistance increases by sixteen times. If the vascular resistance increases, for example due to a narrowing (stenosis), the blood flow to the lungs worsens. If this only affects short sections of the respective vessel, it can usually be compensated for. In the case of large stenoses, however, symptoms of the disease soon appear.

The best ways to prevent possible high blood pressure in the lungs arise with timely and effective treatment of the various chronic diseases that can precede it. Therefore, the recommended preventive examinations are advisable in these cases. This is particularly true if one of the known pre-existing conditions of pulmonary hypertension has occurred or is at increased risk.

Regular measurements of the vascular resistance or the pulmonary blood pressure are possible at any time without major technical requirements.

Illnesses & ailments

If the vascular resistance increases continuously and increases the blood pressure in the pulmonary circulation, pulmonary hypertension develops. It may be followed by a so-called right heart failure, in which the atrium and ventricle on the right side of the heart are weakened and are supposed to refresh the blood from the pulmonary circulation.

The mean blood pressure in the pulmonary artery (pulmonary artery) increases in hypertension from its normal value between 12 and 16 mmHg to more than 25 mmHg at rest. When the patient is lightly exerted, the first symptoms become noticeable between 30 and 40 mmHg. From a pulmonary blood pressure of 50 to 70 mmHg, the heart load increases sharply and the person concerned feels a significant decrease in physical performance.

Circulatory problems and weaknesses can occur. Serious dangers arise with a pulmonary arterial blood pressure of more than 100 mmHg.

In acute pulmonary hypertension, the pulmonary arteries become extremely narrow and their vascular muscles thicken at the same time. The cross-section of the vessel becomes alarmingly small. If the hypertension is chronic, the vascular muscles also swell, but these are also gradually converted into connective tissue. The efficiency of the arteries decreases, the lungs can only absorb less oxygen and the pulmonary vascular resistance increases as a result.

People affected by this usually notice symptoms such as sore throat, shortness of breath, weakness, circulatory disorders and feelings of fainting. Also known are bluish skin discolorations on various parts of the body (cyanosis), water retention and temporary fading on hands and feet due to insufficient blood circulation (Raynaud's syndrome).

In many cases, pulmonary hypertension arises from previous lung diseases (embolism, fibrosis), calcifications in the respiratory tract, asthma, AIDS and congenital or acquired heart defects.

In therapy, the primary disease must first be cured. If this succeeds, there is a chance of successful treatment of pulmonary hypertension. However, very often only risky and medically controversial drug treatment steps are feasible or there are major obstacles to the approval of special drugs.

It was also suspected for a long time that certain drugs used to suppress appetite could promote pulmonary hypertension. In special cases of pulmonary high blood pressure, long-term therapy with oxygen may be successful.

Transplants in the heart / lung area have been tried and tested, but these must always be carefully tailored to the patient's state of health. If primary heart disease is present, the treatment options are very limited.

Without therapy, life expectancy with high blood pressure in the lungs is on average less than three years. A frequent cause of death is right cardiac decompensation (right heart failure), which is usually associated with very severe cardiac arrhythmias. For these reasons, early operations are desirable in children with congenital heart defects in order to be able to rule out the development of pulmonary hypertension with some certainty.

Anyone who suffers from pulmonary hypertension should in any case avoid greater physical exertion and, if possible, not stay at an altitude of more than 2000 meters.