Ear, Nose and Throat and Non-Acoustic Barotrauma
Total Page：16
File Type：pdf, Size：1020Kb
B-ENT, 2016, 12, Suppl. 26/1, 203-218 Ear, nose and throat and non-acoustic barotrauma J. Claes1,2, P. Germonpre3, V. Van Rompaey1,2 and E. Bourmanne4 1Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, Edegem, Belgium; 2Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium; 3Centre for Hyperbaric Oxygen Therapy, Military Hospital, Brussels, Belgium; 4Department of Hyperbaric and Emergency Medicine, Centre Hospitalier Epicura, Ath, Belgium Key-words. Blast trauma; barotrauma; third window syndrome; ENT; scuba diving; injuries; pressure Abstract. The organs of the ear, nose and throat (ENT) contain air- or gas-filled cavities, which make them sensitive to pressure changes. There is a specific pathophysiology involved when these structures are exposed to non-acoustic press ure changes, which are usually not traumatic in normals. The concepts of pathophysiology, diagnosis and treatment of these traumas in an emergency setting are reviewed. Introduction which appears after disintegration by a supersonic explosive composition known as a “bang” (e.g., A blast trauma is the physical damage to the human 1-methyl 2,4,6 trinitrobenzene [TNT], Semtex) body caused by a shock wave after an explosion. This bang generates a quick chemical reaction Typically, blast traumas are subdivided into four involving the decomposition of an explosive possible types of lesions, where only the primary substance due to a sequential wave shock. This lesions are directly caused by a shock wave. creates a mass of gas, the warmer and more In general terms, barotrauma is defined as any compressed central areas of which are propagated lesion caused or provoked by a change in pressure faster than the peripheral areas, thereby creating a differential between various anatomical parts of frontal pressure or shock wave. The latter transfers the organ involved. As membranes and tissue walls the energy to the nearby molecular components. possess a certain resistance to pressure, a change in This is known as an “explosive’s brisant power”. pressure does not always and automatically cause The profile of a wave shock in an open field is a lesion. Pressure differentials can be caused by ideally of the Friedlander type. external factors (change in environmental pressure, It starts with an abrupt elevation of the static sudden increase in locally applied external pressure) pressure or shock front. Then, the pressure or by internal pressure changes. Barotrauma results decreases exponentially towards the atmospheric in physical disruption of membranes and/or tissue, pressure. The time between the bang and the return with anatomical and functional damage as a to the atmospheric pressure is the compression consequence. phase (t0). On the contrary, if we achieve distance As third window syndromes make the ear from the explosion, the wave shock has a negative particularly sensitive to pressure changes, a phase (depressurization), after which there is a separate section of this chapter is dedicated to progressive return to the atmospheric pressure due these syndromes and their typical consequences in to oscillation. Each explosive or weapon has its scenarios involving even minor pressure changes. own pressure wave. The signature of each explosive The aim of this chapter is to summarize and review requires knowledge of the ascent time, the pressure expert opinions and literature data on these subjects. ridge, the time of the positive phase and the pulse.1 A sub-aquatic blast is much more dangerous 1. Blast trauma at the same distance than an air blast because the 1.1. Physics density of water causes a wider high-speed spread. The profile of the shock wave depends on the The blast is the body’s damage caused by a shock environment in which the detonation appears. In wave after an explosion. It is thus the energy release, the case of an open space, the wave shock will 15-claes-.indd 203 6/11/16 17:02 204 J. Claes be omnidirectional, spherical or hemispherical, which can present a tympanic tear and the possible whether it appears near to the ground or not. On disarticulation of the tympano-ossicular chain, or a the opposite, in a closed space, the wave will be haemorrhage resulting in conductive deafness (for confined or directed if channelled by a rigid wall. more details, see chapter 12). The inner ear can also The destructive power of each explosive is be affected, with injury to the cochlear membranes, given by means of an equivalence compared to an thereby causing perceptive hearing loss.5 explosive reference: TNT. The symptomatology is characterized by hearing A cannon effect can be observed if the explosive loss, tinnitus, earache, vertigo and secondary is maintained in a confined space (e.g., a mine otorrhoea. One must, however, keep in mind that buried in a clayey soil), while we can observe extreme noise exposure also has an impact on the fragmentation if the explosive is placed in a hull, central nervous system, causing neural damage.6 fragments of which will be expelled at a speed This damage can also influence the intensity and greater than that of the initial wave shock. persistence of “aural symptoms”, such as tinnitus, The presence of a wall is enough to form multiple vertigo and poor speech discrimination. shock waves due to reflection. Each wave shock In a recent study of 63 patients, who were then generates bodily injuries.2 examined at the Antwerp University Hospital within one month after the terrorist attack at 1.2. Physiopathology Brussels International Airport on 22nd March 2016, Two mechanisms of injury should be considered.3 we found the predominant presenting symptoms to First, the implosion, which means that, in soft be tinnitus and aural fullness (Table 1). This was body areas, there is initially compression followed the case in both those who presented with drum by sudden relaxation, causing parietal fractures perforations and one particular individual with (e.g., auricular and digestive injuries). haemotympanum, as well as those with normal Second, the shock wave in tissues of different otoscopy. density causes the sudden compression of less 1.4. Associated lesions dense tissues by the denser tissues. The quick return to the initial situation generates injuries in the tissue A clinical finding of tympanic perforation must interface (e.g., pulmonary and laryngeal injuries). lead to a lung X-ray or preferably a CT scan of the An explosion generates four types of injuries. thorax. A primary injury is the result of the direct effect of the shock wave on the organs. A secondary injury is the consequence of the impact from Table 1 ammunition fragments or environmental rubble. Overview of physical findings during otological and Third, the victim’s body can be injured because audiological examinations vs. presenting symptoms in a of its displacement, or its projection, which would population of 63 individuals who presented within one month mean a tertiary injury in this case. Finally, a after being exposed to explosions at the Brussels International Airport departure hall on 22nd March 2016. Complaints quaternary injury can be observed and covers all of tinnitus and aural fullness predominate, even in those others consequences (collapse, thermal effect, dust individuals where no objective abnormalities were found. 4 inhalation etc.). Hearing loss The ear is the first organ reached in case of an Symptoms No Yes Total air blast, followed by damages to the respiratory Normal Tinnitus 16 24 40 apparel (lung and larynx) and finally the bowels. otoscopy Ear pressure 12 19 31 The bone or nerve injuries occur in cases of a borne blast (e.g., a projectile striking armour plating). Hyperacusis 4 3 7 Abnormal Tinnitus 3 3 1.3. Ear lesions otoscopy Ear pressure 1 1 An eardrum tear occurs at 20 kPa for a wave Hyperacusis 0 0 shock of 3 m/s in a positive phase. The tympanic Total tinnitus 16 27 43 examination is therefore a priority in cases of blast Total ear pressure 12 20 32 suspicion. The first affected organ is the middle ear, Total hyperacusis 4 3 7 15-claes-.indd 204 6/11/16 17:02 ENT and non-acoustic barotrauma 205 At the pulmonary level, the injuries are explained Furthermore, the upper airway is classically by the weight difference between the affected lung affected by the passage of the shock wave. Laryngeal and a normal lung. The alveolar haemorrhage petechiae are commonly found during fibroscopy, increases the weight of the lung, thereby causing with the presence of these injuries being a sign asphyxia or systemic air embolism. It is generally of pulmonary injury because the laryngeal lesion accepted that it is the impact between the lung and threshold is just below the pulmonary threshold. the rib cage that generates injuries. We consider Finally, the digestive system is also affected in the movement speed of the rib cage to be a good cases of primary blast because its lesion threshold indicator of the injury.7 is just below the upper airway. The bowel We first observe laryngeal damages at a speed may be torn, leading to pneumoperitoneum or of 4 m/s, while the pulmonary lesion threshold haemoperitoneum.9,10 appears at a speed of 10 m/s. Among the 63 patients described in Table 1, 1.7 Take-home messages three individuals presented with a drum perforation The damage after a blast trauma depends on the and one with a haemotympanum. All patients were power of the explosive, the distance between the examined by fiberoptic indirect laryngoscopy. No victims and the deflagration, and the space where one showed evidence of laryngeal damage. Results it appears. from the physical examination of the lungs in all The ear and the upper and lower respiratory tract patients and the medical imaging of the thorax in 19 are the most frequently affected.