Nitrogen bubble detection after simulated dives in divers with patent foramen ovale. Is catheter closure indicated?
Abstract
Purpose: The aim of the study was to test the risk of paradoxical embolism of nitrogen bubbles after simulated dives in divers with patent foramen ovale (PFO), and to compare the safety of commonly used decompression regimens. Methods: This study adds on our previous studies, where we performed screening for PFO in 353 Czech scuba divers using transcranial doppler sonography (TCD).
In 31 divers previously diagnosed with PFO we detected venous bubbles using transthoracic echocardiography (TTE) and arterial bubbles using TTE and TCD after surfacing from simulated dives in recompression chambers. The amount of bubbles was rated as small (<20) or large (20).
Three different decompression procedures were compared - Bühlmann 18 m, US Navy 18 m and US Navy 50 m. Results: In the Bühlmann 18m regimen venous bubbles were detected in 3/14 (21 %) divers, no arterial bubbles (0 %) detected.
In US Navy 18 m regimen venous bubbles detected in 6/9 (67 %), arterial in 2 (22 %). In US Navy 50 m regimen venous bubbles detected in 7/8 (88 %), arterial in 6 (75 %).
Significantly lower number of venous bubbles was detected after Bühlmann regimen dives compared with US Navy (21 % vs. 76 %, P < 0.01). Conclusion: The well documented fact of bubble formation and paradoxical embolization in divers with PFO after simulated dives was tested on a small study group.
Significantly lower number of venous bubbles was detected when using Bühlmann regimen (recommended for recreational diving in the Czech Republic). The results indicate higher risk of paradoxical embolization of bubbles in deeper dives with relatively shorter decompression procedure.
PFO screening should be recommended to all divers, further approach and indication to catheter closure is individual, simulated dives can test individual risk.