Don’t Connect the Dots

DAN medics and researchers answer your questions about dive medicine.



Q: I was diving last week from a liveaboard in the Bahamas. Each day I did around four dives and never experienced any problems. I waited 24 hours before flying home, and I felt completely fine during the flights. Now after being home for three days, I woke up this morning feeling terrible. My joints ache, I'm dizzy, I have a headache, and I feel weak. Some of my experienced dive buddies are confident this is decompression sickness (DCS). What does DAN think?


A: It is a natural human tendency to try to establish cause and effect or to "connect the dots." It is helpful to consider possibilities, but it can be counterproductive to self-diagnose or assign blame too quickly. A health-care professional must provide an actual diagnosis, and the pertinent facts must be viewed objectively and within the proper context.

Certainly joint aches, headache, dizziness and weakness are among the signs and symptoms associated with DCS, but we must evaluate those signs and symptoms in the context of the facts. This diver reported no symptoms after diving. The surface interval prior to flying was within the recommended guidelines (a minimum of 18 hours after multiple dives). Think about why it is considered safe to fly after waiting the recommended time: Studies show that after that period nitrogen levels in the body are no longer sufficiently elevated to cause symptoms during a routine commercial flight. If by some odd chance a diver had enough residual nitrogen to cause a problem, the symptoms would likely occur during the altitude exposure. This diver did not report any signs or symptoms during her flights. The chances of nitrogen having anything to do with this diver's symptoms are essentially nonexistent.

Most divers understand, at least intellectually, that a diver can do everything right and still sustain a decompression injury. However, most seem to have difficulty accepting this concept when it actually occurs. The overwhelming number of cases diagnosed as DCS have no discernable cause (other than breathing compressed gas at depth and subsequently returning to the surface). But divers often try to find some factor to blame. This is speculation, however, and can be counterproductive.

If you experience symptoms after diving please do not decide on your own what the diagnosis should be. Get a medical evaluation. DAN is available for consultation with medical professionals as well as directly with divers. Always consider your symptoms within a proper context — don't connect the dots.

— Marty McCafferty, EMT-P, DMT


Q: I understand that feeling tired after a dive may be a symptom of decompression sickness, but I almost always feel tired after diving. Should I be concerned?




A:The expectation of normal (i.e., nonpathological) tiredness following diving varies from person to person. Factors such as individual fitness, thermal stress, gear constriction, diving skill, work completed during the dive, psychological stress (positive or negative) and distraction can all affect how tired one feels. While these variables make it difficult to quantify tiredness as a symptom of decompression sickness (DCS), unusual fatigue has long been documented in association with other symptoms of DCS.

The mechanism behind fatigue as a symptom of DCS remains elusive, although it is possibly a response to a cascade of physiological events taking place in various tissues. It could be through direct stimulation of nervous tissues or indirectly through the stimulation of other tissues. It is possible that the attention currently being directed toward identifying biochemical markers of DCS will help resolve the questions. In the meantime, it is reasonable to say that DCS represents a complex, multifocal response to a decompression injury. Unusual or "undue fatigue" (that in excess of normal fatigue for a given individual and diving exposure) is a recognized symptom.

— Neal W. Pollock, Ph.D.


Q: My doctor recently put me on Coumadin. Could diving while taking this medication cause me any problems?



A: There is a well-recognized risk for uncontrolled bleeding in people who are being treated with anticoagulant medications such as Coumadin. However, many people who take anticoagulants — including divers — have carefully adjusted their prothrombin times and with appropriate behaviors may not be at undue risk. Some physicians believe diving is an unnecessary risk for their patients who are taking anticoagulants and will advise against diving, but DAN is unaware of any data indicating that sport divers face an increased risk of complications.

Some physicians trained in dive medicine may be willing to endorse recreational diving for these patients provided:
  • the underlying disorder or need for anticoagulants does not put the patient at increased risk of an accident, illness or injury while diving.
  • the patient understands the risks and modifies his or her dive practices to reduce the risk of ear, sinus and lung barotrauma as well as physical injury. This includes avoiding forceful equalization — equalization must come easily for these people.
  • the patient dives conservatively, planning short, shallow profiles to reduce the risk of decompression illness, which can involve bleeding in the inner ear or spinal cord.
  • the patient avoids diving in circumstances in which access to appropriate medical care is limited.

DAN medics are available for consultation with you or your doctor; don't hesitate to give us a call.

— Dan Nord, EMT-P, DMT


Q: When trying to provide rescue breaths in the water to an injured diver, why can't I use my spare regulator's purge button? That seems easier to me than trying to manage a pocket mask.

A: Using the purge button of a second-stage regulator has been proposed many times, but any advantage it may seem to offer does not outweigh the potential risks and complications.

If the regulator mouthpiece is not already in the unconscious diver's mouth, trying to replace it can be difficult and time consuming. Without a good seal and a means to occlude the diver's nostrils, any attempts to ventilate will be unsuccessful. Even if the mouthpiece can be successfully placed in the diver's mouth there is a risk of it pushing the relaxed tongue to the back of the throat and blocking the airway.




If the regulator mouthpiece remained or was placed in the diver's mouth without blocking the airway, the next challenge would be administering air. Purge buttons do not have any true regulatory capability. They effectively override the second stage's function of stepping down gas from intermediate pressure to ambient pressure and thereby deliver intermediate-pressure gas directly from the first stage. Delivering breathing gas to the lungs at too high a pressure may overinflate them, potentially leading to serious injury. If the diver's airway is not maintained in an open position, the breathing gas delivered by the purge button could be forced into the stomach, causing gastric distention. This places the diver at risk for regurgitation, which can further compromise the airway and lead to aspiration.

Delivering rescue breaths using a pocket mask or similar method provides tactile feedback via changes in pressure required to ventilate the lungs; supplying rescue breaths with the purge valve eliminates this important feedback. Using a regulator's purge valve also precludes the option of supplementing the gas with 100 percent oxygen.

Rescue methods that are currently taught by dive-training agencies are the result of years of practical experience. Purge valves were never designed to function as rescue equipment. When ventilating an injured diver, rely on established methods.

— Marty McCafferty, EMT-P, DMT

Ask Us
The DAN Medical Information Line is here to answer all your dive-related medical questions. You can reach the medical staff during regular business hours (Monday through Friday, 9 a.m. to 5 p.m. ET) by calling +1-919-684-2948, ext. 222. You can also submit an email at DAN.org/Contact.


© Alert Diver — Spring 2014