Research Article: MRI Findings of Otic and Sinus Barotrauma in Patients with Carbon Monoxide Poisoning during Hyperbaric Oxygen Therapy

Date Published: June 12, 2013

Publisher: Public Library of Science

Author(s): Ping Wang, Xiao-Ming Zhang, Zhao-Hua Zhai, Pei-Ling Li, Samuel J. Lin. http://doi.org/10.1371/journal.pone.0065672

Abstract

To study the MRI findings of otic and sinus barotrauma in patients with carbon monoxide(CO) poisoning during hyperbaric oxygen (HBO) therapy and examine the discrepancies of otic and sinus abnormalities on MRI between barotrauma and acute otitis media with effusion.

Eighty patients with CO-poisoning diagnosed with otic and sinus barotrauma after HBO therapy were recruited. Brain MRI was performed to predict delayed encephalopathy. Over the same period, 88 patients with acute otitis media with effusion on MRI served as control. The abnormalities of the middle ear and paranasal sinuses on MRI were noted and were compared between groups. Nine patients with barotrauma were followed up by MRI.

In the barotrauma group, 92.5% of patients had bilateral middle ear abnormalities on MRI, and 60% of patients had both middle ear cavity and mastoid cavity abnormalities on MRI in both ears. Both rates were higher than those in the control group (p = 0.000). In the two groups, most abnormalities on MRI were observed in the mastoid cavity. The rate of sinus abnormalities of barotrauma was 66.3%, which was higher than the 50% in the control group (p = 0.033). In the nine patients with barotrauma followed up by MRI, the otic barotrauma and sinus abnormalities had worsened in 2 patients and 5 patients, respectively.

MRI is able to depict the abnormalities of otic and sinus barotrauma in patients with CO-poisoning during HBO therapy and to differentiate these from acute otitis media with effusion.

Partial Text

HBO therapy has been used widely in clinical practice. It is useful to decrease the incidence of delayed neuropsychologic sequelae in patients with CO-poisoning[1]–[2]. Although patients with CO-poisoning could benefit from the therapy, the side effects, such as barotrauma, should not be overlooked. Barotrauma is defined as tissue damage resulting from the direct effects of pressure[3]–[4]. According to Boyle’s law, a primary change in environmental pressure results in an inverse change in volume. Pressure changes can affect the ears, the sinuses, and the lungs, resulting in injury. Otic barotrauma is one of the most common barotraumas after HBO therapy and is sometimes accompanied by sinus barotraumas [3]–[4]. Under normal conditions, the eustachian tube must open to eliminate the pressure difference between the internal and ambient environments. When the eustachian tube or sinus ostia is blocked or the pressure change exceeds the capacity of its regulation, otic and sinus barotrauma occurs [3]–[8].

Barotrauma is pressure-induced injury. MRI can be useful to evaluate effusions in the middle ear and sinus disease [14], [21]–[25]. Our data reveal that in the group of patients who suffered from barotrauma, most of the abnormalities were found in the bilateral middle ear, and in the bilateral abnormalities, simultaneous abnormalities of the middle ear cavity and mastoid cavity are the most common. The rate of middle ear and sinus abnormalities of barotrauma was significantly higher than in the control group, including simultaneous abnormalities of the bilateral middle ear cavity and mastoid cavity, abnormalities of either middle ear cavity or mastoid cavity of the two ears, and abnormalities of the sphenoid sinus. MR imaging is useful to distinguish otic or sinus barotrauma from acute otitis media with effusion. In both groups of this study, the abnormalities of the middle ear were most commonly and first observed in the mastoid cavity. Our results indicate that bilateral middle ear abnormalities on MRI during HBO, especially both middle ear cavities and mastoid cavities, with no pre-existing history of otologic disease,could be considered barotrauma. When mastoid cavity abnormalities occur on MRI, steps should be taken to prevent the involvement of the middle ear cavity, or else delayed healing and disease progression are likely.

Source:

http://doi.org/10.1371/journal.pone.0065672