This document discusses acute suppurative otitis media (ASOM), an infection of the middle ear. It begins by defining ASOM and explaining that obstructed Eustachian tubes, respiratory infections, and allergies can lead to bacterial contamination of the middle ear. Common bacteria include Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. ASOM frequently affects children due to anatomical differences in their Eustachian tubes that make contamination more likely. The document then describes the pathophysiology of ASOM using an analogy of a flask and explains the stages of the infection and its potential complications if not treated promptly with antibiotics.
2. Definition
It is defined as suppurative infection
involving the mucosal lining of middle
ear cleft. The term acute is used to
indicate infections of less than 3
weeks duration
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4. Microbiology
Commonly viral (Viral infections help
bacteria to adhere to the middle ear
mucosa)
Bacteria implicated include:
S. Pneumoniae
H. Influenza
M. Catarrhalis
These infections commonly affects children because their
Eustachean tubes are shorter, wider and straighter
facilitating easy efflux of contaminants in to the middle ear
cavity from Nasopharynx
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5. Role of Eustachean tube
Patulous
Eustachean tube
Hypotonic
Eustachean tube
Congenital
abnormalities of 1st
and 2nd arch
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6. Flask model
ET, Middle ear, and mastoid air cell
system can be likened to be that of a
flask with a narrow neck
The mouth of the flask is the
nasopharyngeal end of ET
Narrow neck is the isthmus of the ET
Bulbous portion is the middle ear
chamber and mastoid system
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7. Flask model
Fluid flow through the neck of the
flask is dependent on:
1. Pressure at either end
2. Radius & length of the neck
3. Viscosity of the liquid
When a small amount of liquid is instilled into the mouth of the flask, liquid
flow stops somewhere in the narrow neck owing to capillarity within the
neck and the relative positive air pressure that develops in the chamber of
the flask.
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9. Protective function of ET
ET protects middle ear from
nasopharyngeal contamination
The basic geometry of the ET is
considered to be critical for this
function
Reflux of liquid into the body of the
flask occurs if the neck of the flask is
wide / length of the neck of flask is
short as is the case in children
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13. ASOM (Stages)
Stage of Hyperemia
Stage of exudation
Stage of suppuration
Stage of resolution
The progression of these stages are dependent on:
1. Virulence of infecting organism
2. Host immunity
3. Adequacy of antibiotic therapy
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14. Hyperemia
Hyperemia of
mucous membrane
Otalgia / fever /
fullness common
Antibiotics during
this stage will help
in the resolution of
disease
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15. Exudation
Out pouring of fluid
from the blood vessels
of mucoperiosteum of
middle ear
Fluid is initially serous
in nature
The whole middle ear
cavity is tense
Suppuration eventually
follows
Ear drum starts to
bulge
These patients have
mastoid tenderness
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16. Suppuration
Exudate present in
the middle ear
suppurates due to
superadded
infection
This stage needs to
be treated with
antibiotics
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17. Resolution
This stage is preceded by rupture of
ear drum
Discharge from the middle ear starts
to flow out (Light House sign)
These patients have reduced Otalgia
Fever if present subsides
Patients show excellent clinical
improvement
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18. Complications
Presence of middle ear infections for more
than 2 weeks cause complications
This is due to obstruction of normal
drainage of middle ear due to thickening of
mucoperiosteum
Complications commonly include coalescent
mastoiditis, subperiosteal abscess
These patients have low grade fever and
Otalgia
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