Eardrum

Brick buildings severely damaged, 75% external wall collapse. Fired heaters badly damaged. Storage tanks leak from base. Threshold for eardrum damage to people. Domino or knock-on radius. Pipe bridges may move. 

The ear is a very sensitive and complex organ that responds to very small variations in pressure. It was argued in Hirsch (1968) that ear drum rupture is decisive as to ear damage from blast waves. Figure C-3 shows the percentage of eardrum ruptures as a function of side-on overpressure F,. 

Ohr-speicheldriise, /. parotid gland, -stein, m. otolith, -trommel,/, eardrum, -trompete,/. (Anat.) Eustachian tube, -wachs, n. ear wax, cerumen, -wasser, n. endolymph. 

Another well-established area of mechanical finite-element analysis is in the motion of the structures of the human middle ear (Figure 9.3). Of particular interest are comparisons between the vibration pattern of the eardrum, and the mode of vibration of the middle-ear bones under normal and diseased conditions. Serious middle-ear infections and blows to the head can cause partial or complete detachment of the bones, and can restrict their motion. Draining of the middle ear, to remove these products, is usually achieved by cutting a hole in the eardrum. This invariably results in the formation of scar tissue. Finite-element models of the dynamic motion of the eardrum can help in the determination of the best ways of achieving drainage without affecting significantly the motion of the eardrum. Finite-element models can also be used to optimise prostheses when replacement of the middle-ear bones is necessary. 

Figure 9.3. The human ear is divided into three main parts. The outer ear collects sound and directs it down the ear canal towards the eardrum. The size of the eardrum, comhined with the lever action of the three hones of the middle ear, ensures the efficient conduction of sound from the ear canal, which is filled with air, to the inner ear, which is filled with a liquid. Very small muscles, not shown here, are cormected to these bones to protect the ear from very lond sounds. The inner ear consists of two parts. Only the cochlea is shown, which is the part of the human ear that is responsible for converting sound into electrical signals in the auditory nerve. The other part of the inner ear, the vestibular organ, is involved in balance.

Tympanostomy tube A small plastic or metal tube inserted in the eardrum to keep the middle ear aerated and improve hearing in patients with chronic middle ear effusion. 

Fever is present in less than 25% of patients and, when present, is mote often in younger children. Examination shows a discolored, thickened, bulging eardrum. 

Pneumatic otoscopy or tympanometiy demonstrates an immobile eardrum 50% of cases are bilateral. Draining middle ear fluid occurs (<3% of patients) that usually reveals a bacterial etiology. 

Eisenberg3 reported the following data on the effect of explosion peak overpressures on eardrum rupture in humans ... 

A blast produces a peak overpressure of 47,000 N/m2. What fraction of structures will be damaged by exposure to this overpressure What fraction of people exposed will die as a result of lung hemorrhage What fraction will have eardrums ruptured What conclusions about the effects of this blast can be drawn ... 

Table 2-4 converts the probit to percentages. The result shows that there are no deaths and that less than 10% of the exposed people suffer eardrum ruptures. This assumes complete conversion of explosion energy. 

Hexavalent chromium compounds have been implicated as responsible for such effects as ulcerated nasal mucosa, perforated nasal septa, rhinitis, nosebleed, perforated eardrums, pulmonary edema, asthma, kidney damage, erosion and discoloration of the teeth, primary... 

Fill ear insert a moist cotton plug repeat 1-2 h PRN Caution [C, ] Contra w/ perforated eardrum Disp Soln 5.4% antipyrine, 1.4% benzocaine SE Local irritation Interactions May X effects OF sulfonamides EMS None OD Unlikely, may be harmful if swallowed... 

Contraindications Perforated eardrum, history of hypersensitivity to desonide or other corticosteroids... 

The pressure of the air on the outside of your eardrums is decreasing faster than is the pressure of the air on the inside of your eardrums. FYI, commercial airplanes maintain a cabin pressure that is equal to the pressure one experiences at about 2400 meters (8000 feet) up a mountainside. 

Model rooms (Refs 57 80) and houses (Ref 170), communication tunnels (Refs 58,81 118), magazines (Refs 128 163) and a storage bay (Ref 82), and concrete arches (Ref 59) and bunkers (Ref 103) have been exposed to up to 500-ton explns. Trees and automobiles have been similarly tested (Ref 129). Simulated human bodies have been tested in a coniferous forest (Ref 48). Foxholes showed little damage (Refs 41 95) sheep in open 2-man foxholes showed severe eardrum damage, but were otherwise unharmed except for slight pulmonary... 

Hearing works by the ear detecting sound waves, converting them into neural signals and then sending the signals to the brain. The ear has three divisions the external ear, the middle ear, and the inner ear (Figure 10). The external ear collects sound waves and funnels them down the ear canal, where they vibrate the eardrum. Within the middle ear, the eardrum is connected to... 

We have discussed only the visual aspects of the fourth vision. Auditory phenomena are of equal importance. Here the solid, labelled nature of auditory patterns is lost, and the mechanical impact of sound hitting the eardrum is registered. In some cases, sound becomes converted into pure sensation, and synesthesia (mixture of sense modalities) occurs. Sounds are experienced as colors. External sensations hitting the cortex are recorded as molecular events, ineffable. 

Blank cartridges can produce fatal wounds when fired at, or near, contact, and they work very well in power heads. As with firearm ammunition, blanks can also damage the eardrums when discharged. 

Range for 1-90% eardrum rupture among exposed population... 

Cotton wool buds should not be poked into the ear, as wax is pushed further in and eardrum perforation is possible. 

Leibovici, D., Gofrit, O. N., Shapira, S. C. (1999). Eardrum perforation in explosion survivors Is it a maker of pulmonary blast injury Annals of Emergency Medicine, 34, 168-172. 

In a detonation, a pressure front (shock wave) forms and propagates at supersonic speed, rapidly compressing and igniting the flammable mixture and giving the appearance of an instantaneous combustion. In the Vicinity of the detonation, the force of the shock wave can demolish a building or propel a bullet. The noise is the vibration of the eardrums caused by the shock wave. 

Mild cases, characterised by pinkness or infection of the eardrum, often resolve spontaneously and need only analgesia emd observation. They are normally viral. A bulging, inflamed eardrum indicates bacterial otitis media usually due to Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Bran-hamella) catarrhalis. Streptococcus pyogenes (Group A) or Staphylococcus aureus. Amoxicillin or co-amoxiclav is satisfactory, but the clinical benefit of antibiotic therapy is very small when tested in controlled trials. Chemotherapy has not removed the need for myringotomy when pain is very severe, and also for later cases, as sterilised pus may not be completely absorbed and may leave adhesions that impair hearing. Chronic infection presents a similar problem to that of chronic sinus infection, above. 

EMLA is a new anesthetic ointment that anesthetizes the external ear canal and eardrum. After keeping the ointment in the external ear canal for 15-20 min it is removed. The surgical procedure may then be completed. This product has been used for myringotomy under local anesthesia. 

The human hearing apparatus is commonly considered in three sections the outer ear, middle, and inner ear. The outer ear consists of the pinna (generally called the ear) and the external auditory canal, which terminates in the tympanic membrane or eardrum. The outer ear collects sound, amplifying some frequencies and attenuating others. The eardrum... 

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