Diving Mask Squeeze

Etiology

Barotrauma related to diving is the result of unconnected compartments of air that produce a pressure difference between them. The mask squeeze injury is the result of a pressure difference inside the mask and the surrounding water pressure. As the diver descends into the water, the surrounding pressure will increase. According to Boyle's Law, this pressure must be balanced by a change in volume if the pressure does not increase within the mask. The problem occurs when the diver does not exhale some of his air through their nostrils, which would allow the volume to remain constant by increasing the pressure within the mask. If the dive does not do this, the pressure inside the mask essentially remains the same, and this air space will attempt to contract; this results in a relative negative pressure inside the mask. The distinction here is that the injury occurs as the result of essentially a “suction” applied to the area of the face covered by the mask. The injury results when this "suction" leads to tissue cell rupture and vessel dilation that can cause small vessels to rupture, leading to tissue injury and ecchymosis. Eye injury can also occur, including conjunctival bleeds, and rarely to orbital subperiosteal hematoma.[3][4]

Epidemiology

Scuba divers and freedivers are at risk for mask squeeze. Most are inexperienced. Swimmers wearing goggles or a mask that only covers

the eyes but not the nose may suffer injury from descending below the surface as well.

Data is limited to the number of annual injuries reported for this sub-type of dive-related barotrauma. Estimates that at least 500 dive-related barotrauma injuries occur each year in the U.S., but many cases go unreported as the injury is often mild. The Diver Alert Network (DAN) provides a reporting system and is the largest database of injuries reported.[5]

History and Physical

The history of the patient is vital to a diagnosis. They will give a history of recent SCUBA diving or freediving. Most have very little experience, so the physician should review their experience level, as well as the depth of the dive. Symptoms of mild mask squeeze include facial pain, redness, bruising, periorbital swelling, and subconjunctival hemorrhages. Rarely more severe injury to the eye can occur. Symptoms of a serious injury include eye pain, proptosis, limited extraocular movements, diplopia, and other visual changes. Review of systems should also include other complaints that may suggest another type of dive injury, including shortness of breath, cough, ear pain, epistaxis, and dizziness. The diver or others with them may report a suspected decompression illness.[6]

While the physical exam will focus on the areas involved, including the eyes, periorbital area, upper face, and forehead. Eye evaluation should include at least visual acuity, ocular range of motion, and diplopia. Suspicion of more serious eye injury will require an ophthalmologic exam. Concern for a decompression illness requires a more extensive evaluation not covered here.[7]

Evaluation

The history of present illness, review of systems, and physical exam are all that are required to make a diagnosis for most cases.

A CT or MRI of the orbits of the eye is required if the examiner notes any visual anomaly, including double vision, proptosis, or restricted ocular movements.[8][9]

Treatment / Management

The vast majority of mask squeeze injuries require no treatment. Mild injuries to the skin, including swelling, bruising, petechia, will resolve within one to two weeks with supportive care. Mild eye injuries, including conjunctivitis and subconjunctival hemorrhages, will also resolve without any intervention in a short time. More severe eye injuries such as a subperiosteal orbital hematoma require emergent evaluation by ophthalmology. If this injury involves compression of the optic nerve or evidence of increased intraocular pressure, needle aspiration or orbitotomy with drainage may be required. Otherwise, conservative management of the eye injury with follow-up visits with ophthalmology may be all that is required.[10][11](B3)

It is important to realize that, unlike decompression-related injuries, mask squeeze is a trauma related to a pressure gradient, not a result of the consequence of microbubbles that occur from decompression. Therefore, treatment does not include oxygen or compression chambers. However, decompression injuries can be coexistent with a mask squeeze, so the examiner should be watchful for signs or symptoms that may suggest this.

Differential Diagnosis

The diagnosis is usually conclusive by history, physical, and imaging studies.

The examiner should be alert to the possibility of other dive-related injuries, such as decompression illness.

Prognosis

Prognosis is usually excellent with complete recovery. Severe eye injuries will usually have excellent outcomes in areas where ophthalmology is available.

Complications

Rare, again, most complications occur if the examiner does not recognize the potential for severe eye injuries. Other complications can arise if concurrent decompression illness is also present. The examiner should remain alert to this possibility.