The Illness of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome is also known as ARDS.  It is a very serious lung disease that is actually a reaction to an initial insult to the lungs.  There is an inflammatory reaction to the lung tissue that results in poor gas exchange and a release of inflammatory chemicals into the bloodstream.  Multiple organ failure is not out of the question and the lethality rate is high.
Acute respiratory distress syndrome is often called adult respiratory distress syndrome to keep it separate from a related condition called infant respiratory distress syndrome, common in preemies.  The condition was first named in 1967 by Ashbaugh and associates. In 1994, the condition was redefined by the American-European Consensus Conference Committee. The changes in definition recognized how severe the disease and defined several variables of the disease. 
The definition of ARDS is a situation where the PaO2 (the partial pressure of oxygen) is below 200 mmHg along with alveolar infiltrates on both sides of the lungs as seen on XRAY.  The infiltrates look a great deal like heart failure but the heart shape and size actually appears normal.  The disease has an acute onset and is preceded by an insult to the lung.  The precursor state to ARDS is called acute lung injury or ALI that has a PaO2 of less than 300 mmHg.  When the PaO2 becomes less than 200 mmHg, the disease becomes ARDS or acute respiratory distress syndrome.
Facing a Patient with ARDS
ARDS often occurs between 24 to 48 hours of the initial injury or lung attack.  The person develops rapid breathing, shortness of breath and shock-like symptoms.  The amount of oxygen in the bloodstream is low, red spots show up in the underarm area and there is mental confusion or other neurological findings. 
Occasionally long term sicknesses can trigger ARDS.  One of these is malaria.  The symptoms of ARDS occur at sometime after the acute phase of the illness.  Specialists recommend ruling out any possible cause of heart-related disease as they look very similar to ARDS.  A pulmonary artery catheter is used to determine whether or not the condition is heart-related.  Other testing can include a CT scan of the lung which shows the lung tissue and infiltrates a great deal better than an XRAY. 
Pathophysiology
In ARDS, there is inflammation throughout the lung tissue.  The triggering insult to the lung tissue results in a sudden release of the inflammatory molecules called cytokines.  Cells called neutrophils and T-lymphocytes go to the inflamed lung tissue and make the inflammation worse.  There is damage to the alveoli of the lungs with hyaline membrane creation in the walls of the alveoli.   The exact mechanism by which all this happens is unclear. 

The inflammation of lung tissue causes the endothelial cells to malfunction and leak fluid from the lung capillaries, increasing free fluid within the lungs. The surfactant within the lungs decreases and the patient needs to breathe in more oxygen.  Following this, there is inflammatory exudate (fluid) leaking into the lung space making it more difficult to get oxygen.  Eventually fibrous tissue forms in the alveolar tissue.  Entire alveoli collapse upon themselves or get flooded with fluid.  They process gas and oxygen less and the need for oxygen increases.  When alveoli collapse, air exchange doesn’t happen and the individual needs to be on mechanical ventilation, such as a ventilator.  In fact, mechanical ventilation is a vital part of the treatment of acute respiratory distress syndrome.  The patient eventually must work to breathe to a capacity that is incompatible with life, requiring mechanical ventilation.  While mechanical ventilation is essential, it has its side effects which must be watched out for when dealing with a patient with ARDS.

Treatment

Treatment almost always requires artificial ventilation. One method of treatment is to use the antioxidant glutathione, which is diminished in many forms of lung disease. The dose is given by means of bronchioalveolar lavage.