Hi Bolts,
As you have read, a free diver can sustain a syndrome that includes a number of features suggestive of neurological DCS (e.g., vertigo, nausea, lethargy, paralysis, alterations in vision and hearing).
As such, concluding that one could not have DCS
solely on the basis that the diver hadn't been on scuba at the time would be difficult to support. Moreover, numbness and tingling sensations of the skin, joint pain and nausea are not complaints typical of barotrauma of any sort; they are much more characteristic of a gas bubble disorder.
Of course bubbles that make their way into arterial circulation as a result of pulmonary barotrauma can cause AGE (arterial gas embolism), but AGE doesn't typically present with the constellation of symptoms you describe. Moreover, the signs and symptoms that may arise due to pulmonary barotrauma usually occur during ascent or very shortly after surfacing. Symptoms such as numbness of the right ear appearing a few hours after the last dive aren't likely to be related to pulmonary barotrauma. That examination of the chest, including x-ray, reportedly proved negative further lowers the index of suspicion of pulmonary barotrauma. Hopefully your visit with the chest physician next week will prove informative.
Getting back to the DCS from free diving hypothesis, the published descriptions indicate diving schedules involving frequencies and depths that far exceed the "5-10 or so" dives to "increasing depths, starting at about 10m and ending up at around 25m" which you report. This makes sense when one considers times/depths as they relate to inert gas loads and bubble formation. Given the millions of recreational free dives that take place every year, it seems very likely that if a pattern of diving such as the one you describe caused a DCS-like syndrome with any frequency, then diving medicine would be aware of it.
However, if a diver has an abnormality that predisposes him to DCS, such as a patent foramen ovale (PFO) that can facilitate the arterialization of venous gas bubbles, then perhaps a pattern of free diving such as you report could result in a clinical picture strongly suggestive of a gas bubble disorder. You may wish to read the following brief coverage of PFO and its implications for scuba. It's a modified piece based on an item appearing in my "Ask RSD" column in "Rodale's Scuba Diving":
"Patent foramen ovale (PFO) is an abnormal opening between the right and left upper chambers of the heart.
It is normal for blood to flow through a small opening between these two chambers during fetal development when the lungs are inoperative and blood is oxygenated by the mother. At the moment of birth, however, changes in chamber pressures cause this membranous opening to close, shunting blood to the now functioning lungs. While usually permanently sealed by the 3rd month of life, this does not always occur; about one in every four persons has an incomplete closure of varying size. Without complete closure, blood can flow from the right to the left side of the heart without passing through the lungs.
Because the left side of the heart is the "high pressure side," the majority of otherwise healthy persons with PFO, many with only small openings, are unaware they have the condition. However, given a shift in the normal pressure gradient between these two chambers of the heart, blood can flow in the wrong direction.
Of significance to divers with PFO is the increase in right chamber pressure which occurs with equalization techniques like the Valsalva maneuver. Under this condition, nitrogen bubbles that may form in the venous bloodstream during decompression can pass directly into the arteries without the filtering action of the lungs. Divers with PFO can develop decompression illness (DCI) manifestations ranging from relatively harmless skin rashes to serious neurological problems such as vertigo or paralysis. Studies of high frequency divers have found that a large percentage of them with otherwise unexplained incidents of DCI turned out to have PFO. In addition, the risk of severe decompression sickness (DCS) appears to be about three to five times greater in those with PFO as compared to the general diving population, although the relationship is much weaker for only mild cases.
Despite research findings of increased risk of DCI in divers with PFO, the risk is still very low. Most dive medicine experts do not recommend echocardiogram as a routine procedure in healthy divers.
However, evaluation for PFO should be considered given otherwise unexplained incidents of DCI, especially neurological DCI.
At present, the gold standard for detecting the presence and nature of a PFO arguably is transesophageal echocardiogram (TEE) with bubble contrast. This allows bubbles passing from the right to the left to side of the heart to be observed. Even a small number of bubbles are a matter of concern. The basic procedure is described here----> Echocardiography
http://en.wikipedia.org/wiki/Echocardiography. The following recent article suggests several alternative screening techniques that may be considered: "Should All Divers be Screened for PFO?"
http://tenfootstop.blogspot.com/2006/07/should-all-divers-be-screened-for-pfo.html
If repair is indicated, the procedure selected depends upon a number of factors including the size of the opening. There are several approaches, including suturing of the defect or placing a tissue patch over it, although preferred where possible is the non-surgical placement of a blocking device such as the Amplatzer Septal Occluder described here----> Amplatzer
http://www.fda.gov/cdrh/mda/docs/p000039.html
At some point following the repair TEE with bubble contrast likely will be repeated. With these findings and other information regarding fitness to dive, including general health and exercise tolerance, the diver and his physician can decide on the best course of action. Given an uncomplicated and successful closure in an otherwise fit individual, return to diving typically can be expected within 6-12 weeks. ©Doc Vikingo 2005"
Please do keep us informed of your situation--it's how we learn.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice with you or any other individual and should not be construed as such.
Regards,
DocVikingo
