Background

ARDS was first described by Rene Laennec in 1821 as "idiopathic anasarca of the lungs." Injured soldiers succumbing to respiratory failure were described as having a posttraumatic massive pulmonary collapse around World War I, while "shock lung" and "white lung" and "DaNang lung" all came during later military conflicts. It was not until the seminal description of ARDS by Ashbaugh and colleagues in 1967 that physicians recognized their differing descriptions of the same syndrome.1

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a single pathologic process of acute respiratory failure. Acute lung injury is characterized by:

Table 7.1. Disorders associated with ARDS

Disease Incidence of ARDS

Sepsis 41%

Aspiration pneumonia 22%

Pulmonary contusion 22%

Massive transfusions 36%

Pepe PE, Potkin RT, Reus DH et al. Clinical predictors of the adult respiratory distress syndrome. Am J Surg 1982; 144:124-30.

• bilateral infiltrates on chest radiographs

• pulmonary capillary wedge pressure of 18 mm Hg or less

• absence of clinically evident left atrial hypertension

• ratio of partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2:FiO2) of 300 or less

The definition of ARDS is the same with a PaO2:FiO2 ratio of 200 or less with mortality rates of 34-60%. Most deaths are attributable to pneumonia, sepsis, or multiorgan dysfunction.

The combined incidence ofALI and ARDS is estimated to be 75 cases/100,000/ year. Of patients admitted to the ICU, 2-3% will develop ALI or ARDS.

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