title: The impact of performing spirometry on shunting across a patent foramen ovale.
abstract: Transient changes in intrathoracic pressure can alter left and right intra-atrial pressures, and may provoke shunting of blood across a patent foramen ovale (PFO). Spirometry causes a transient rise and subsequent fall in intrathoracic pressure that, if performed following a dive on compressed air, could raise the risk of decompression illness by arterialisation of venous bubbles across a PFO. To assess whether spirometry can provoke right-to-left shunting across a patent foramen ovale, a subject with a known PFO, previously identified by bubble contrast transthoracic echocardiography, where shunting was only evident on performing a Valsalva manoeuvre, underwent re-examination whilst performing spirometry. Right-to-left shunting was not evident at rest, but was provoked by performing spirometry. If spirometry is to be performed within two hours of surfacing, this should be regarded as a potential risk for decompression illness.
authors: Senior Registrar, Department of Diving and Hyperbaric Medicine, Royal Hobart Hospital, GPO Box 1061L, Hobart, Tasmania 7001, Australia, Phone: +61-(0)3-6222-8193, Fax: +61-(0)3-6222-7268, E-mail: ianmaddox75@hotmail.com.
authors: Ian Ec
authors: IE
authors: Maddox
authors: David R
authors: DR
authors: Smart
authors: Warrick Lj
authors: WLj
authors: Bishop