Adult respiratory distress syndrome (ARDS), also known as acute lung injury, is a unique pathologic condition. It causes severe hypoxemic respiratory failure and has characteristic X-ray findings following an inciting event. There are about 200,000 cases of ARDS each year in the United States, with a mortality rate between 30% and 50%.
Acute respiratory failure itself may be either hypoxemic or hypercapnic. Hypoxemic respiratory failure is identified by either a partial pressure of oxygen (PaO2) less than 60 mm Hg or oxygen saturation by pulse oximetry (SpO2) less than 91% without any supplemental oxygen or a ratio of PaO2 to fraction of inspired oxygen (FiO2) ratio less than 300 on supplemental oxygen.
To qualify as ARDS, acute respiratory failure must be so severe that respiratory support with positive airway pressure is necessary—this is an integral diagnostic component of ARDS.
ARDS results from acute diffuse inflammation and injury to alveolar membranes and capillaries causing fluid exudation and interstitial pulmonary edema. Management is primarily supportive care. Patients with the condition require positive end-expiratory pressure (PEEP) while mechanically ventilated or noninvasive continuous positive airway pressure (CPAP).
The chest X-ray of a patient with ARDS shows bilateral diffuse alveolar opacities and dependent atelectasis. A chest CT typically demonstrates widespread patchy and/or coalescent opacities, usually more apparent in the dependent lung zones.
In a patient with these characteristic imaging findings, the diagnosis of ARDS and its severity depends on the PaO2/FiO2 ratio, with either noninvasive CPAP or invasive PEEP of at least 5 cm H2O. According to the 2018 updated Berlin definition, severity is classified in three stages. Stage 1 (mild) ARDS is defined as a PaO2/FiO2 ratio of 200 to 300 with noninvasive CPAP or invasive PEEP. Stage 2 (moderate) is a PaO2/FiO2 ratio of 100 to 200 with invasive PEEP, and stage 3 (severe) is a PaO2/FiO2 ratio below 100 with invasive PEEP.
Common causes of ARDS are shown in the Table. Transfusion-related acute lung injury is a particularly interesting phenomenon that may occur with the transfusion of one or more units of any blood product. It occurs in about one of every 5,000 transfusions.
ARDS must be distinguished from other conditions that may mimic it, such as cardiogenic pulmonary edema, diffuse alveolar hemorrhage, pulmonary vasculitis, disseminated malignancy, and acute interstitial pneumonitis. Cardiogenic pulmonary edema is frequently encountered in critically ill patients and is a common confounding condition. Evidence of acute left ventricular failure should make the distinction.
The ICD-10-CM code for ARDS is J80. The term “ARDS” must be specifically documented. If instead the diagnosis is documented as acute lung injury, the patient will be incorrectly assigned a code for trauma to the lung, not ARDS. The stages of ARDS are not recognized by ICD-10-CM, so code J80 should be used for all ARDS cases.
Since severe respiratory failure is a defining component of ARDS, a separate code for respiratory failure is not assigned for an ARDS diagnosis. An exception would be when respiratory failure was already present due to another cause before ARDS occurred.
The CMS 2019 DRG definitions upgraded code J80 from a comorbidity and complication (CC) to a major CC (MCC). MCCs reflect greater severity and cost of care than CCs.
In summary, ARDS is identified by a precipitating event, a characteristic chest X-ray or CT scan and severe acute respiratory failure defined by a PaO2/FiO2 ratio of 300 or less with either noninvasive CPAP or invasive PEEP greater than 5 cm H2O. Severity is classified as mild, moderate, or severe based on the PaO2/FiO2 ratio. ARDS must be distinguished from other conditions that may mimic it, particularly cardiogenic pulmonary edema.
The ARDS code is J80, and the term “ARDS” must be specifically documented. Acute lung injury is inadequate to describe patients with ARDS because it is assigned a lung trauma code. Respiratory failure is not separately coded since it is a defining criterion for ARDS. Code J80 should be used for all cases of ARDS, since the stages of ARDS are not recognized by ICD-10-CM.