Diagnostic Criteria for the Hepatopulmonary Síndrome (HPS)
All criteria were determined by means of positive contrast-enhanced echocardiography (i.e., microbubble opacification of the left heart chambers three to six cycles after right atrial passage). The abbreviated formula for the alveolar–arterial gradient is as follows:
PAO2−PaO2 = (FIO2 [Patm–PH2O] – [PaCO2/0.8]) – PaO2,
where PAO2 denotes partial pressure of alveolar oxygen, PaO2 partial pressure of arterial oxygen, FIO2 fraction of inspired oxygen, Patm atmospheric pressure, PH2O partial pressure of water vapor at body temperature, and PaCO2 partial pressure of arterial carbon dioxide (0.8 corresponds to the standard gas-exchange respiratory ratio at rest); the normal range is 4 to 8 mm Hg (0.5 to 1.1 kPa). The normal range for the partial pressure of oxygen is 80 to 100 mm Hg (10.7 to 13.3 kPa) at sea level, while the patient is at rest and breathing ambient air. For patients older than 64 years of age, a value of ≤70 mm Hg (9.3 kPa) for PaO2 or ≥20 mm Hg for the alveolar-arterial gradient is often used. Ambient air is the respired gas unless otherwise indicated. To convert millimeters of mercury to kilopascals, multiply by 0.133.
Created: May 31, 2008