A 56-year-old male with 30-pack year smoking history, CAD, and advanced liver disease due to alcoholic cirrhosis is being evaluated for a liver transplantation. He complains of worsening shortness of breath. His heart rate is 110/min, blood pressure is 97/64 mm Hg, respiratory rate is 32/min, and saturation 90% on 5 L/min nasal cannula. When asked to sit up in bed, the patient states that he “usually breathes better” when lying supine.
Which of the following is the MOST likely pathophysiology behind the diagnosis?
A. Decreased FRC resulting in increasing closing capacity leading to atelectasis
Correct Answer: C
The development of intrapulmonary vascular dilatations (IVPD) in the presence of advanced liver disease and portal hypertension results in hepatopulmonary syndrome (HPS). Several mediators included nitric oxide, endothelin 1, TNF alfa, and vascular endothelial growth factor have been implicated in the development of these IVPDs. The dilation of these blood vessels results in shunting of blood, leading to V/Q mismatch, hypoxemia, and an increased alveolar arterial oxygen gradient. These IVPDs tend to occur predominantly in the base of the lungs, resulting in worsening of the shunt while upright. This manifests as platypneaorthodeoxia. Contrast-enhanced echocardiography can aid with the diagnosis of HPS and microaggregated albumin (MAA) can help distinguish and quantify hypoxemia resulting from IVPD in patients with other lung parenchymal disorders. Liver transplantation is the definitive treatment. Although several experimental medical therapies have been tried, none of them have consistently shown to be of benefit in the treatment of HPS.