The investigators will prospectively estimate incidences of decompression sickness in SCUBA divers with or without patent foramen ovale (PFO). All participants will receive transesophageal echocardiogram and transcranial doppler to ascertain whether they get a PFO. Clinical follow up will be undertaken 3 month after transesophageal echocardiographic evaluation, and every 6 month up to 3 years by E-mailing or telephone interview with self-questionnaire report. All decompression sickness (DC) events or DC-like symptoms will be reviewed by a professional diver, who is a medical doctor and member of DAN-AP, and a neurologist.

PFO was defined as transesophageal echocardiographic (TEE) evidence of infused microbubbles in the left atrium within three cardiac cycles after their appearance in the right atrium, at rest or during Valsalva release. If TEE finding will not be conclusive, we will decide the presence or absence of PFO with supplementary transcranial doppler. It will be blinded to participants, physicians and research persons to perform clinical follow-up. It will be not officially recorded, and will be preserved by another research person, who will not contact study participants.

Inclusion Criteria:

• Divers who experienced fifty dives per year

Exclusion Criteria:

• Decompression sickness within recent 20 dives
• Previous procedure or surgery for closure of PFO or ASD
• Previous cerebral infarction or hemorrhage
• Previous epilepsy
• Previous angina or myocardial infarction

Recreational or occupational SCUBA (self-contained underwater breathing apparatus) divers