We should not forget one of the first lessons we were taught as new divers: Don’t force it — if it’s hard to equalize, end the dive.
The DiverThe diver was a 26-year-old woman with approximately 200 lifetime dives.
The DiveShe did a single, morning dive to a maximum depth of 88 feet. She reported no troubles equalizing or other complications during her descent. Approaching her safety stop near the end of the ascent, however, she was struck by a sudden massive headache, nausea and vomiting. She skipped the safety stop and ascended directly to the surface. The headache and vomiting continued on the boat, and she also experienced an onset of what she called dizziness. The crew helped her remove her gear and administered oxygen. After a few minutes with no improvement, the crew recalled the rest of the divers and called emergency medical services (EMS) and the DAN® Emergency Hotline.
AnalysisFurther discussion revealed that the dizziness the diver reported was likely true vertigo. Vertigo is characterized by a spinning sensation and is usually accompanied by nausea and vomiting, while dizziness is a sensation of loss of balance.
In a diving context, a sudden onset of vertigo during ascent or descent is suggestive of ear barotrauma, with inner-ear barotrauma (IEBT) being most concerning. Ear pain may or may not be present. Vertigo is also common in cases of inner-ear decompression sickness (IEDCS). Symptom onset for IEDCS is usually not so sudden and dramatic, and the dive profile did not seem to be aggressive enough to immediately suggest IEDCS.Nevertheless, such a diagnosis could not be completely ruled out.
Distinguishing between IEDCS and IEBT can pose a significant diagnostic challenge, but doing so is critical because the two conditions require very different therapeutic approaches, and misdiagnosis and mistreatment could be harmful.
Headaches are a common postdive complaint, often the result of a sinus barotrauma.
Although much rarer, another possible diagnosis was a very bad sinus barotrauma with gas leaking into the cranial cavity (pneumocephalus). The sudden onset of a massive headache associated with a significant drop in barometric pressure accompanied by nausea, vomiting and vertigo was suggestive of such a rare diagnosis. The diver did report some difficulties equalizing and what seemed to have been some sinus pain during descent as well as a sensation of pressure later during ascent. The diver's recent history of a cold increased the likelihood of a very bad sinus barotrauma. Pneumocephalus is usually diagnosed using imaging, but small amounts of gas can be reabsorbed in a short time. Because of the relatively small window for a positive diagnostic image and the harmful — even fatal — nature of pneumocephalus, ruling it out should be a priority.
The mechanism of injury is assumed to be a reverse block of the sinuses. The presence of mucus and inflammation of mucous membranes are the most common causes of transient sinus blockage. These generally pose no greater risk than inflammation in the mucous membranes of the sinuses, but with the ambient pressure changes involved in diving, a partial or intermittent blockage may act as a valve that impairs normal gas flow in the sinuses.
Gas expansion from a reverse block can be significant enough to disrupt the thin bone walls separating the sinuses from each other and from the cranial cavity. When a sinus cavity suddenly relieves its pressure into another one, this usually manifests as pain, a headache and possibly a nose bleed. Gas leaking into the cranial cavity (pneumocephalus), on the other hand, can result in anything from headaches to life-threatening neurological deficits.
Potential consequences will depend on the amount of gas and the degree of displacement of normal anatomical structures. This sort of injury can initially manifest as a moderate or severe headache or, in severe cases, result in seizures or even death. Most cases of pneumocephalus resolve spontaneously without surgical intervention. Management involves breathing oxygen, keeping the head of the bed elevated, taking antibiotics (especially when traumatic injury is involved), managing pain and performing frequent neurologic checks and repeated CT scans.
Evaluation and TreatmentThe diver's X-rays revealed subtle signs that could indicate pneumocephalus, which warranted admission to the hospital. These findings, however, could not be reproduced during a CT scan several hours later. These diagnostic discrepancies prompted some discussions, but based on the case history, symptom presentation and initial imaging, the diagnosis was still thought to be pneumocephalus following sinus barotrauma. The patient had been breathing pure oxygen since surfacing, including during transportation, evaluation and hospital admission, which could have sped up the reabsorption of the gas.
In the absence of concrete evidence of pneumocephalus, the treatment plan was for the patient to continue to breathe oxygen, begin a course of antibiotics, undergo repeat CT scans and be observed for no less than 48 hours.
A six-month follow-up appointment revealed the diver had a very good outcome and had no complications during or after her hospital stay. She has not resumed diving.
DiscussionOne of the first rules we learn as student divers is to discontinue diving when we experience difficulty equalizing. This is probably the first rule we all break. Questions about the use of decongestants are among the most common asked on the DAN Medical Information Line. (Learn more about decongestants and diving at DAN.org/medical/FAQ.)
With regard to barotrauma risk, the most critical phases of a dive are the descent and ascent, during which massive barometric changes take place. When divers have difficulty equalizing during descent, dive leaders often go to excessive lengths to avoid aborting a dive, encouraging divers to try different equalization techniques and instructing them to alternate between ascending a few feet and trying again to descend. It is also not uncommon to see divers pinching their nose and blowing during ascent, presumably because they are experiencing equalization difficulties while ascending. Both of these practices are counterproductive and significantly increase the risk of middle-ear, sinus and inner-ear barotrauma.
Problems with sinus inflammation and congestion may be amplified by the sinuses' natural responses to cold temperature. Exposure to cold triggers a reflex to limit heat that manifests as increased mucus production and swelling of mucous membranes. This is known as "cold-induced rhinitis." Sea water can also have an irritating effect on mucous membranes, further stimulating mucus production.
Normally this has no negative consequences other than copious amounts of clear mucous when we surface, but be careful when diving: If you are recovering from a cold or have other predisposing factors such as active allergies, gas movement between sinuses may be significantly more difficult. If you experience mild difficulty equalizing at the beginning of a dive, chances are the increased mucus production and swelling of mucous membrane may make equalizing even more difficult near the end of the dive. Remember you can always abort a descent; aborting an ascent is a lot more problematic.
© Alert Diver — Q2 Spring 2016