Body processes

Intra-abdominal pressure – function, function and diseases

Intra-abdominal pressure

The intra-abdominal pressure , also called IAP for short and in medical jargon, describes a breathing-dependent pressure that is present within the abdominal cavity . In a healthy person, this pressure is around a measured value of 0 to 5 mmHg. If the intra-abdominal pressure is too high, arterial blood flow may be reduced.

What is intra-abdominal pressure?

In specialist medicine, the IAP is understood as the pressure that prevails inside the abdominal cavity. This pressure is measured in millimeters of mercury (mmHg for short) at the end of the breathing cycle ( expiration ). In a healthy adult, this pressure is typically between 0 and 5 mmHg. If the value is over 5, medicine speaks of a slightly increased value, although this does not always have to be harmful to health. Only when the value exceeds 12 mmHg and lasts for more than twelve hours is it usually referred to as increased intra-abdominal pressure, which is dangerous to health.

However, a very high or long-term elevated IAP can have a negative impact on blood circulation . The result can be malfunctions or even damage to the abdominal organs.

On the other hand, if the intra-abdominal pressure is above 20 mmHg for too long, there may even be a noticeable decrease in arterial blood flow. This primarily affects the abdominal organs, but also partially the venous return flow to the heart .

Function & task

The intra-abdominal pressure is the pressure that permanently prevails in the abdominal cavity of humans (and also of many other vertebrates). This pressure is measured with the patient lying flat. In a healthy person, this value should normally be below 5 mmHg.

However, various diseases can cause the pressure to rise permanently to up to 7 mmHg, without there being a direct medical impact on the body. The level of intra-abdominal pressure depends on the patient’s breathing and physical condition.

But what is the function of intra-abdominal pressure in the body? Various studies show that the intra-abdominal pressure increases during physical exertion such as lifting heavy loads. This relieves the organs , but also the spine and the intervertebral discs . In this case, the increasing pressure acts like a shock absorber acting inside the body.

Furthermore, the intra-abdominal pressure supports things like digestion – even if only indirectly. Because sports exercises, such as abdominal exercises, which increase the pressure inside the abdomen, have been shown to work more effectively when the rectum is subjected to minimally increased pressure.

On the other hand, the internal organs, the spine and the intervertebral discs can also be damaged or their function impaired if the pressure is too high and lasts too long. While optimal or normal pressure in the abdominal cavity ensures that the organs are not supplied with too much blood , excessive pressure quickly ensures that they are undersupplied. In addition, the intra-abdominal pressure also puts pressure on the organs – which in turn can lead to organ damage or malfunction if the elevated IAP lasts for too long.

Diseases & Ailments

Intra-abdominal pressure in a healthy adult ranges from about 0 to 5 mmHg. However, some diseases can cause the pressure to rise to a value of up to 7 mmHg even in normal conditions. In addition, medicine only speaks of a health risk from a value of at least 12 mmHg.

Intra-abdominal pressure can increase for a variety of reasons. A common example is physical stress, such as that which can occur during sports or lifting. However, the intra-abdominal pressure can also increase due to various diseases or injuries.

Common causes of rising or elevated intra-abdominal pressure are injuries such as abdominal trauma, an abdominal abscess , a mesenteric infarction (also known as an intestinal infarction), a buildup of air in the abdominal cavity (commonly known as pneumoperitoneum), an obstruction of the intestine ( called an ileus ), or bleeding in the abdomen.

Injuries and diseases like these can usually be diagnosed or ruled out by measuring the intra-abdominal pressure. The IAP is measured in the flat position over the urethra . The bladder must be empty for this.

A distinction is made between four stages of increased intra-abdominal pressure: Grade I to IV. Medicine speaks of increased pressure of Grade I when the value is between 12 and 15 mmHg. Grade II is a value between 16 and 20 mmHg. Grade III denotes an intra-abdominal pressure that ranges between 21 and 25 mmHg. On the other hand, grade IV is an elevated pressure that is higher than 25 mmHg.

A pressure above 20 mmHg can already lead to severe health impairments. For example, abdominal compartment syndrome can develop. This means that the pressure inside the abdomen ensures that the blood flow to the organs is reduced.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.