Correspondence

A Case of Platydeoxia?

N Engl J Med 2006; 354:1759-1760April 20, 2006

Article

To the Editor:

The Clinical Problem-Solving article by Hegland et al. (Dec. 1 issue)1 concerned a case of platypnea–orthodeoxia, in which a positionally dependent intracardiac right-to-left shunt led to arterial desaturation when the patient was in the upright position but not the supine. We report a case in which the converse occurred.

An 81-year-old woman was brought to the emergency room by her neighbors, who found her lying on the floor of her apartment, markedly confused. On examination, the patient was cooperative but delirious. She was hemodynamically stable, her respiratory rate was 13 breaths per minute, and her initial oxygen saturation was 95 percent while breathing room air. Repeated oximetry several hours later revealed an oxygen saturation of 80 percent and blood gas measurement yielded a partial pressure of arterial oxygen (PaO₂) of 34 mm Hg that did not improve despite the delivery of high-flow oxygen by aerosol mask. The patient was intubated and transferred to the intensive care unit. A spiral computed tomographic scan was negative for pulmonary embolism but revealed a very large aneurysm in the ascending aorta (8.2 cm by 8.0 cm) that was compressing the right main pulmonary artery.

In the intensive care unit, the patient was placed in a sitting position and the PaO₂ increased to 486 mm Hg. Her PaO₂ remained elevated despite the reduction of the fraction of inspired oxygen (FiO₂) to 35 percent, and she was extubated and transferred back to the ward. On the ward, her oxygen saturation dropped to 60 percent and rose only marginally while she was breathing supplemental oxygen. It was then noted that the oxygen saturation rapidly corrected to 100 percent when the patient was placed lying on her side or sitting upright. A transthoracic echocardiogram with bubble study was performed; it revealed a patent foramen ovale with a notable increase in right-to-left shunting when the patient was lying supine, as opposed to in the left lateral decubitus position (Figure 1Figure 1Transthoracic Echocardiography with Microbubble Contrast.). Measures of blood gases obtained with the patient supine and breathing with an FiO₂ of 100 percent indicated a shunt fraction of 28 percent, whereas the shunt fraction when the patient was sitting was 10.5 percent. After considering cardiovascular surgery, the patient opted for a pillow to maintain the lateral decubitus position during sleep. This measure prevented nighttime oxygen desaturation.

We hypothesize that the supine position increased the compression of the patient's pulmonary artery by her ascending thoracic aneurysm, leading to an increment in pulmonary-artery pressure, which in turn increased intracardiac right-to-left shunting. To our knowledge, all reported cases of positionally dependent intracardiac right-to-left shunting document increased shunting in the upright position2 — hence the term “orthodeoxia.” We suggest “platydeoxia” to describe the converse phenomenon.

Ian D. Bookman, M.D.
University Health Network, Toronto, ON M5G 2C4, Canada

Eric T. Dryver, M.D.
University Hospital of Lund, 22185 Lund, Sweden
eric.dryver@skane.se

2 References

1. 1

   Hegland DD, Kunz GA, Harrison JK, Wang A. A hole in the argument. N Engl J Med 2005;353:2385-2390
   Full Text | Web of Science | Medline

2. 2

   Chen GP, Goldberg SL, Gill EA Jr. Patent foramen ovale and the platypnea-orthodeoxia syndrome. Cardiol Clin 2005;23:85-89
   CrossRef | Web of Science | Medline

Citing Articles (1)

Citing Articles

1. 1

   Tsung O. Cheng. (2008) Patent foramen ovale in high-altitude pulmonary edema: A vicious cycle. International Journal of Cardiology 126:3, 433-434
   CrossRef