We are all too familiar with tachypnic and the occasional bradypnic patient (i.e. narcan deficient) rolling through resus, but rarely do we come across platypnic and orthodeoxic (except for yesterday). In order to come across them, you need to know what they are, so here we go.
Platypnea is defined as dyspnea in the upright position that improves with laying flat.
Orthodeoxia is similarly defined as a drop in O2 Sat by more than 5% when sitting up that also returns to baseline when laying flat.
When should you suspect this and what causes it? Great questions. Platypnea is commonly seen in patients with hepatopulmonary syndrome, with an estimated prevalence of 5-47% in those with liver disease (really precise estimate…). Although the etiology is unknown, it thought to be due dilatation of pulmonary capillary vessels and preferential perfusion of these vessels that are mostly found at the lung bases, i.e the least well oxygenated. It may also be due to AV shunting of these same vessels (see image).
Why does it matter to you, the front line EM provider? Well, it doesn’t truly change management, but keep it in the back of your mind that in a patient with severe liver disease, the respiratory position of comfort may actually be laying flat, not siting upright.
Ferreira PP, Camara EJ, Paula RL, et al. Prevalence of hepatopulmonary syndrome in patients with decompensated chronic liver disease and its impact on short-term survival. Arq Gastroenterol 2008; 45:34.
Lange PA, Stoller JK. Hepatopulmonary syndrome: prevalence, causes, clinical manifestations, and diagnosis. Mandel J and Finlay G (Eds) in Uptodate.com http://www.uptodate.com/contents/hepatopulmonary-syndrome-prevalence-causes-clinical-manifestations-and-diagnosis?source=see_link
Lee, D. Cirrhosis (liver). Marks JW (Ed) on MedicineNet.com http://www.medicinenet.com/cirrhosis/page8.htm (for image)
Rodríguez-Roisin R, Krowka MJ. Hepatopulmonary syndrome–a liver-induced lung vascular disorder. N Engl J Med 2008; 358:2378.