Synonyms in a broader sense
Acute respiratory distress syndrome, acute lung failure, shock lungAcute respiratory distress syndrome (ARDS) is an acute lung injury in previously lung-healthy patients, caused by direct (located in the lung) or indirect (systemic, but not cardiac) causes. ARDS is defined as follows: A distinction is made between acute lung failure (ARDS) and ALI (= acute lung injury). ALI is the milder form and only differs from acute lung failure in its definition by an oxygenation index between 200 -300 mmHg.
- Acute onset
- Fluid accumulations (=infiltrates) in both sides of the lung (=bilateral), visible in an x-ray of the upper body (x-ray thorax in the posterior-anterior beam path)
- Index for oxygen saturation (= oxygenation index) PaO2 /FiO2 < 200mmHg
- This is also known as the Horowitz oxygenation index and indicates the quotient of the oxygen partial pressure in the arterial blood (i.e. blood leaving the heart and enriched with oxygen) and the proportion of oxygen in the air we breathe in. The quotient is normally 500 mmHg. – Pulmonary capillary occlusion pressure (= PCWP, wedge pressure) < 18 mmHg and no indication of increased pressure in the left heart. – The wedge pressure reflects the pressure in the left heart and is measured using a right heart catheter. The normal range is between 5 – 16 mmHg.
Frequency
Uniform data on acute respiratory failure are missing. The data are between 5 – 50 /100000/year. In intensive care, about 30% of patients are affected.
A distinction is made between direct and indirect lung damage (acute lung failure): Indirect causes are:
- Inhalation (= aspiration) of stomach contents or fresh/salt water (“near-drinking”)
- Inhalation of toxic (=toxic) gases, such as flue gas
- Inhalation of hyperbaric oxygen
- Poisoning (= intoxication) with anaesthetics
- As a result of pneumonia requiring artificial respiration (= pneumonia)
- Sepsis ( blood poisoning )
- Burns
- Polytrauma
- Fat embolism
- Replacement of blood volume by donated blood (= mass transfusion)
- Acute pancreatitis (= inflammation of the pancreas)
- Shock
- Bone marrow / stem cell transplantation
The pancreas is located in the body at the beginning of the digestive tract. It releases many enzymes that are needed to break down and digest the food that is taken in. The pancreas can become inflamed as a result of medication, metabolic disorders, infections or a build-up of bile.
As a result, the digestive enzymes, which are normally safely packaged, enter the pancreatic tissue and destroy it. An acute inflammation can cause severe pain in the upper abdomen, usually accompanied by fever and a clearly distended abdomen. A complication of this disease can be acute lung failure.
The permanent inflammation of the pancreas leads to a so-called consumption coagulopathy. The blood clotting system is permanently activated by constant small bleedings. After a certain period of time, the coagulation factors are used up and more severe bleeding occurs because the blood no longer coagulates.
The first phase of this consumption coagulopathy is accompanied by the formation of many small blood clots, which can disturb the blood flow in other organs. The lung is particularly susceptible to interrupted blood flow and reacts with acute lung failure. The course of acute lung failure (ARDS) can be divided into 3 stages, which lead to a massive disruption of lung tissue:
- Exudative phase: the wall between the alveoli and the blood vessels is damaged, increasing the permeability of proteins and fluid.
Fluid accumulations (=oedema) form in the lungs. – Early proliferative phase: The lung cells (pneumocytes type II) perish, resulting in a lack of a surfactant, which allows fluid to enter the alveoli. An alveolar pulmonary oedema is formed.
Furthermore, thin walls (=membranes) form between the alveoli and the connecting branches of the air-conducting pathways. Small blood clots (=microthrombi) form in the small blood vessels. This stage is reversible.
- Late proliferative phase: The lung is remodeled by incorporating more connective tissue (=fibrosis). This also affects the wall between lung and blood. This thickens up to five times, making both blood circulation and the transfer of oxygen into the bloodstream more difficult. This stage is irreversible and often fatal.