Letter to the Editor Effect of conservative dive profiles on the occurrence of venous and arterial bubbles in divers with a patent foramen ovale: A pilot study ☆ Jakub Honěk a,b , Martin Šrámek b,c , Luděk Šefc b , Jaroslav Januška d , Jiří Fiedler a , Martin Horváth a , Aleš Tomek c , Štěpán Novotný e , Tomáš Honěk a , Josef Veselka a, ⁎ a Department of Cardiology, Charles University in Prague, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic b Institute of Pathological Physiology, Charles University in Prague, First Faculty of Medicine, Prague, Czech Republic c Department of Neurology, Charles University in Prague, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic d Cardiocenter, Hospital Podlesi, Trinec, Czech Republic e Hyperbaric Chamber, Kladno Regional Hospital, Kladno, Czech Republic article info Article history: Received 14 April 2014 Accepted 17 April 2014 Available online 26 April 2014 Keywords: Patent foramen ovale Decompression sickness Paradoxical embolism Conservative dive profile Patent foramen ovale (PFO) is a risk factor for decompression sick- ness (DCS) in divers due to paradoxical embolization of nitrogen bubbles formed in peripheral blood during decrease of ambient pressure [1]. In our previous study we have demonstrated that catheter-based PFO clo- sure prevented right-to-left shunting of bubbles and might prevent DCS recurrence [2]. However, the question of PFO closure is still debat- able [3]. Also, randomized clinical data are lacking in this field. Therefore, the majority of divers are currently not referred for PFO closure, and various conservative dive profiles (CDP) are recommended to prevent unprovoked DCS (i.e., without violation of decompression regimen) [4]. Unfortunately, to date, the safety of these CDP has not been tested in di- vers with PFO. The aim of this study was to test the effect of dive time and ascent rate restrictions on the occurrence of venous and arterial bubbles in divers with PFO after simulated dives. We compared a standardly rec- ommended no-decompression dive [5] and a stricter regimen with slower ascent to the same control dive, which was previously used to test the efficacy of catheter-based PFO closure [2]. We screened a total of 532 consecutive divers for PFO using transcra- nial color coded sonography (TCCS). The diagnosis of PFO was confirmed by transesophageal echocardiography. Forty-six divers (36.4 ± 10 years; 72% men) with a significant PFO (grade 3 according to the international consensus criteria [6]) who had previously not undergone PFO closure were enrolled in this pilot study. All divers performed a simulated dive to 18 m in a hyperbaric chamber. Divers were randomized into three groups: group A (n = 13; 36.5 ± 9 years; 77% men) performed a stan- dard Bühlmann regimen no-decompression dive (dive time 51 min, ascent rate 10 m/min), group B (n = 14, 40.9 ± 12 years; 64% men) performed the same regimen with a slower ascent (51 min, 5 m/min), and a control group (n = 19; 33.0 ± 8 years; 74% men) performed a staged-decompression dive according to the US Navy decompression regimen (80 min, 9 m/min, decompression stop 7 min at 3 m). Within 60 min of surfacing, the presence of venous and arterial bubbles was assessed. Venous bubbles were assessed by pulse wave Doppler in the right ventricular outflow tract (RVOT), and arterial bubbles by TCCS dur- ing native breathing and after Valsalva maneuvers, as described previ- ously [2]. The study was approved by the local ethics committee and all patients signed an informed consent. In all divers, visualization of RVOT and the middle cerebral artery was possible. The occurrence of arterial and venous bubbles is summarized in Fig. 1. There was significantly lower occurrence of venous bubbles in groups A and B compared to controls (for group A, 31% vs. 74%, p = 0.03; for group B, 14% vs. 74%, p b 0.01). The reduction in arterial bubble occurrence was not significant in group A compared to controls, but there was elimination of arterial bubbles in group B (for group A, 8% vs. 32%, p = 0.42; for group B, 0% vs. 32%, p = 0.03). There was no significant dif- ference in venous or arterial bubble occurrence between groups A and B (venous, 31% vs. 14%, p = 0.38; arterial, 8% vs. 0%, p = 0.48). All divers were observed for any DCS symptoms 24 h after the simulated dive. In the control group transient neurological symptoms (headache, unusual fatigue, and transitory visual disturbances) were present in 21% of divers, no DCS symptoms were observed in group A (p = 0.13) or B (p = 0.12). Generally, the aim of our research is to stratify the risk of DCS in divers with PFO and to find the optimal management strategy for symp- tomatic divers, including potential catheter-based PFO closure. In our International Journal of Cardiology 176 (2014) 1001–1002 ☆ The authors disclaim any commercial, proprietary, or financial interest in any products or companies described in this article. Research was supported by MH CZ–DRO, University Hospital Motol, Prague, Czech Republic 00064203; SVV 2014-260 033 from the Charles University in Prague; and PRVOUK-P24/LF1/3 of the Charles University in Prague — First Faculty of Medicine. ⁎ Corresponding author at: Department of Cardiology, University Hospital Motol, V Úvalu 84, 150 06 Praha 5, Czech Republic. Tel.: +420 224434901; fax: +420 224434920. E-mail address: veselka.josef@seznam.cz (J. Veselka). http://dx.doi.org/10.1016/j.ijcard.2014.04.218 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved. Contents lists available at ScienceDirect International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard