Platypnea

Specialty: Respiratory.

• orthostatic dyspnea
• dyspnea when standing
• dyspnea induced by the erect position

Why it occurs

• Hepatopulmonary syndrome (characterized by microscopic vasodilation of pulmonary capillaries in patients with advanced liver cirrhosis, causing an imbalance in the ventilation/perfusion relationship when standing due to gravity)
• Position-dependent right-to-left intracardiac shunt (as occurs in patent foramen ovale or atrial septal defect associated with right atrial myxoma, atrial septal aneurysm, or severe scoliosis that modifies the alignment of the vena cava with the septum when standing)
• Idiopathic platypnea-orthodeoxia syndrome (functional disorder that causes arterial hypoxemia and respiratory difficulty when standing, which is almost completely relieved in the recumbent position)
• Pulmonary arteriovenous malformations located at the lung bases (where standing increases basal blood flow due to gravity, exceeding the lung oxygenation capacity and increasing intrapulmonary shunt)
• Chronic obstructive pulmonary disease (COPD) of a very advanced emphysematous nature (with severe dynamic collapse of the airways when standing and alteration of expiratory reserve volumes)

Initial workup

Systematic differential pulse oximetry (measurement in the supine position and after a minimum of 10 minutes of active standing); Transthoracic and transesophageal echocardiogram with agitated microbubble contrast (to delineate the presence and time of appearance of intracardiac or intrapulmonary shunt); Computed tomography angiography (CT-Angio) of the chest with vascular reconstruction; Quantitative ventilation-perfusion (V/Q) scintigraphy with macroaggregated albumin; Right heart catheterization in supine and standing positions.

Standard management

• Portable supplemental oxygen therapy — adjusted by intermittent flow titration during standing to maintain oxygen saturations greater than 90-92%
• Sildenafil — phosphodiesterase 5 inhibitor, prescribed under close monitoring at a dose of 20 mg every 8 hours to modulate pulmonary vascular resistance in specific cases of hepatopulmonary syndrome
• Propranolol (used at doses of 20-40 mg every 12 hours in the context of cirrhosis for the concomitant management of portal hypertension, monitoring hemodynamic tolerance).