The medical term perfusion pressure refers to the pressure with which an organ or tissue structure to be supplied with blood is perfused. Mathematically, the amount of perfusion pressure results from the difference between the blood pressure in the arteries and the tissue pressure moving in the opposite direction. Depending on the area of the body, this results in a different value.
What is perfusion pressure?
The medical term perfusion pressure refers to that pressure with which an organ or tissue structure to be supplied is perfused. The term perfusion pressure is a technical term used in human medicine. It is used to indicate the pressure with which an organ or tissue is supplied with blood. Depending on the area of the body, there is a specific measured value, which has its own meaning as a subterm. As an example, the following values are distinguished:
- Pulmonary perfusion pressure: This is the perfusion pressure with which the lungs are supplied. It results from the difference between the mean value of the pulmonary artery pressure (PAD) and the pressure of the left arteries.
- Coronary perfusion pressure: The pressure of the coronary arteries, which supply blood to the heart muscle.
- Ocular perfusion pressure (OPD): this describes the perfusion pressure in the human eye. It results from the difference between intraocular pressure and arterial pressure.
- Cerebral perfusion pressure (CPP): the pressure with which the brain is perfused. It is derived from the difference between the pressure at which blood is pumped into the brain (MAP pressure) and the intracranial pressure.
Function and task
In medicine, perfusion pressure serves as one of the most significant indicators for determining human health. Although each person has an individual perfusion pressure, which varies depending on the specific situation, age and environment, significant conclusions about the state of health can be carried out based on average values. For example, the perfusion pressure of the eye, the ocular perfusion pressure (OPD), is an important factor for prognosis and diagnosis in glaucoma. This is because it is relevant to the supply and activity (or inactivity) of the optic nerve. In the case of not only transient disturbances of the ocular perfusion pressure (too low pressure), the ocular changes responsible for glaucoma are induced. Cerebral perfusion pressure (CPP), which indicates the rate of pressure to the brain, can also provide insightful information about a patient’s health. This is because adequate blood supply to the brain or the entire cranial region is essential. Inadequate supply can lead to death. These descriptions can also be applied to the pressure of the coronary arteries (coronary perfusion pressure). Undersupply can lead to cardiac arrest and ultimately death.
Diseases and medical conditions
Insufficient cerebral perfusion pressure (perfusion pressure of the brain) can cause a drop in pressure that eventually leads to insufficient blood flow to the brain or a complete cessation of blood flow. This so-called ischemia is usually due to a change in the blood vessels. Such can be the result of an embolism or thrombosis, for example. Ischemia can occur temporarily or be permanent. The longer it lasts, the greater the risk of persistent tissue damage. In bad cases, it is referred to as critical ischemia. Ischemia causes cellular metabolic impairment. It is often accompanied by a lack of oxygen. The processes set in motion by this can lead to the death of cells (cell death or necrosis) and thus trigger an infarction. Such an infarction is therefore not only possible in the area of the heart (myocardial infarction), but can also occur in the area of the brain (cerebral infarction or ischemic stroke). The consequences vary depending on the severity of the infarction. If immediate care is not provided, the infarction can be fatal. The period of time in which the pressure loss caused by ischemia can be tolerated without permanent damage (ischemia time) varies from organ to organ. According to the literature, the ischemia time of the brain is only a few minutes. For organs that can be transplanted (e.g. kidney, heart, liver, etc.) it is much longer, up to a maximum of 12 hours.Furthermore, a too low perfusion pressure in the eye (the ocular perfusion pressure) can promote the formation of a cataract (Latin: glaucoma). In essence, the term cataract is used as a collective term for various diseases of the eye. They all have in common that they damage the retina and thus impair the ability to see. Glaucoma often develops after the age of 40. The frequency increases with age. An untreated cataract leads to blindness. Early diagnosis and treatment is therefore of particular importance. The symptoms of glaucoma increase with the duration of the disease. At the beginning, they are hardly noticeable. Patients report an increased feeling of pressure in the eye. Frequently, there is also a reduction in vision. A narrowing of the visual field is also characteristic. This symptom is often accompanied by loss of contrast perception. A photophobia is also typical. In the course of cataract treatment, great care is taken to maintain adequate ocular perfusion pressure to prevent worsening of symptoms that have already occurred. Blood pressure is also influenced. The extent of therapy as well as the appropriate measures depend on the individual case. Surgery is possible, as is the administration of medications.
