ARDS Severity Score

Criteria for ARDS according to the American-European consensus

(1) acute onset of arterial hypoxemia with PaO2/FIO2 < 200 mm Hg regardless of PEEP level

(2) bilateral infiltrates on chest X-ray

(3) pulmonary artery occlusive pressure < 18 mm Hg or no evidence of left atrial hypertension

(4) presence of compatible risk factors

Parameters:

(1) presence of cirrhosis and/or direct lung injury

(2) right atrial and pulmonary artery occlusive pressure, as measure of right ventricular dysfunction

(3) length of mechanical ventilation prior to onset of the ARDS

(4) SAPS II score

(5) underlying, comorbid conditions

(6) oxygenation index, based on mean airway pressure, FIO2 and PaO2

oxygenation index =

= (mean airway pressure in cm H2O) * (FIO2) * 100 / (PaO2 in mm Hg)

where:

• right atrial pressure exceeding pulmonary artery occlusive pressure indicates right ventricular dysfunction

• SAPS II is discussed in the chapter on critical care

ARDS severity score =

= SUM(points for parameters present)

logit =

= (0.09385 * (ARDS severity score)) - 7.6697

probability of hospital mortality =

= (EXP(logit)) / (1 + (EXP(logit)))

where:

• The probability curve is shown in Figure 1 on page 1079.

• The area under the ROC curve was 0.95 for the developmental sample and 0.92 in the validation group.

Major findings seen on the first day of mechanically ventilated ARDS:

(1) SAPS II is best severity score

(2) the McCabe-Jackson score contributes to outcome prediction

(3) the triggering risk factor affects survival

(4) patients with a long period of mechanical ventilation prior to onset of ARDS had a worse prognosis

(5) right ventricular dysfunction is associated with a higher risk of death

(6) the oxygenation index has prognostic value