Mechanism of Hyperbaric oxygen therapy in treatment of ear cases

1. Hyperbaric oxygen therapy (HBO)
 HBO involves the administration of oxygen in high concentrations (typically 100%) to
patients while they are exposed to increased atmospheric pressure.
 This hyperoxygenation has several beneficial effects as an adjunctive treatment in a
number of ENT-related diseases.
 To achieve this, patients need to be physically placed inside a pressure container, a
hyperbaric chamber.
o Monoplace chamber
o Multiplace chamber
Physiological effects of hyperbaric oxygen
 The most important effect of hyperbaric oxygenation is an increase in the transportation of
oxygen in the plasma of the arterial blood.
 Whereas the quantity of haemoglobin-bound oxygen being transported is already near-
maximal under “normal” arterial oxygen pressures (of approx. 100 mmHg), breathing
100% oxygen at 2.5 atmospheres (resulting in a PaO2 of approx. 1800 mmHg) will add 5
ml O2 per 100ml blood.
 This is roughly equal to the resting oxygen consumption of an adult human body.
 During hyperbaric oxygen therapy, venous blood will still be fully saturated with oxygen,
indicating that tissue oxygenation is fully achieved with only the plasma-bound molecular
oxygen.
 Therapeutically, this can be used in situations where haemoglobin levels are either too low
(e.g., extreme blood loss anaemia, when no blood transfusions are possible) or non-
functional (severe carbon monoxide poisoning).
 In patients with very low perfusion (arterial insufficiency, venous stasis) HBO may
increase tissue oxygenation even in the absence of sufficient blood flow.
 During hyperbaric oxygen therapy, the capillary oxygen pressure reaching up to 300
mmHg, the diffusion of oxygen from the capillaries to the tissue will increase three- to six
fold.
 High oxygen pressures have a vasoconstrictive effect by antagonism of nitric oxide,
reducing the arteriolar flow by 20-25%. Tissue oxygenation is not compromised, because
of the high oxygen pressures; however, decreased fluid inflow will enhance oedema
resorption.
Normal or even supranormal tissue oxygen levels are important for a number of processes:
 Leucocyte function: neutrophils depend on a high oxygen level to achieve redox potentials
capable of “killing” ingested (by phagocytosis) bacteria; it has been shown that even in
healthy patients, neutrophil killing capacity is only half-maximal under normal tissue
tensions
 Antibiotic efficiency: aminoglycosides, penicillins and a number of other antibiotics have
a markedly reduced inhibitory potential in hypoxic tissues
 Bacteriostasis: the growth of anaerobic bacteria and facultative aerobic bacteria is
suppressed in high oxygen tensions; this constitutes an important adjunctive mechanism of
HBO in the treatment of infections in old or vascular compromised patients
 Reduction of ischaemia-reperfusion phenomena: whereas the re-introduction of oxygen
after ischaemia may trigger deleterious effects such as leucocyte adherence, production of

2. oxygen free radicals and apoptosis, the very rapid restoration of normal mitochondrial
oxygen levels has been shown to (paradoxically decrease these phenomena; hyperbaric
oxygenation is thus a more effective way of reintroducing oxygen than “normobaric” or
even “hypoxic” re-oxygenation
 Collagen synthesis and cross-linking: normal wound healing is characterized by
fibroblast migration (mediated by oxygen gradients), procollagen production and collagen
cross-linking (by oxidation of disulfide bridges); the intermittent elevation of tissue oxygen
tensions stimulates the formation of healthy granulation tissue by providing a solid
collagen matrix for neo-angiogenesis to occur
 Tinnitus, like idiopathic sudden sensorineural hearing loss, has been thought to arise from
a lack of oxygen secondary to vascular insufficiency. For this reason interest has been
shown in the application of hyperbaric oxygen therapy to increase the supply of oxygen to
the ear and brain to reduce the severity of hearing loss and tinnitus.
 A critical assessment of the role of hyperbaric oxygen therapy has been performed by way
of a Coc
Indications for HBO as adjunctive treatment in the following otology-related diseases
1. Idiopathic sudden SNHL
2. Bengein necrotizing otitis externa
3. Malignant otitis externa
4. Osteoradionecrosis of the temporal bone
5. Inner ear decompression sickness
 BNOE Adjunctive hyperbaric oxygen may be considered when there is progression despite
intensive local and systemic treatment and when there is necrosis beyond the tympanic
plate.
 Osteoradionecrosis of the temporal bone. The use of hyperbaric oxygen in radiation-injured
tissue and osteoradionecrosis is controversial.
 Hyperbaric oxygen treatment is indicated in all cases of suspected decompression illness
because failure to treat is associated with permanent functional damage, and death.
 Hyperbaric oxygen has been used on occasion with mixed results and may be considered
as an adjuvant treatment for refractory cases although its efficacy remains unproven.157
HYPERBARIC OXYGEN
The use of hyperbaric oxygen as an adjunct to systemic antimicrobial therapy has been debated
with reports that it confers a beneficial effect.27–29 It increases the partial pressure of oxygen,
relieving hypoxia and enhancing the oxidative killing of microbes. A Cochrane review, however,
found that there was no evidence from randomized controlled trials to support this treatment.
 Impairment of vascular supply and the resulting cochlear ischaemia is one of the proposed
aetiologies for SSNHL.

3.  HBOT has been used in the treatment of SSNHL since the 1960s.
 Hyperbaric oxygen therapy (HBOT) delivers 100% oxygen to a patient at a pressure greater
than 1 atmosphere.
 This results in an increase in tissue oxygenation as well as potentiating the response to
infection and ischaemia.
 For people with early presentation of ISSNHL, the application of HBOT significantly
improved hearing loss, but the clinical significance of the level of improvement is not
debatable.
 The data also suggested that improvement may be related to the severity of the hearing loss
on presentation. However, further evidence is required from future randomized controlled
trials.
 Compared HBOT + oral steroid with oral steroid alone  The results showed no significant
difference between the two groups and therefore did not support the addition of HBOT to
oral steroids.
Malignant otitis externa
 Necrotizing external otitis, also called necrotizing malignant otitis, is an external otitis
resistant to local treatment and involves the temporal and adjacent bones.
 The infection results from an invasion of the external ear canal by a pathogen.
 The typical patient at risk is an elderly diabetic (or immunocompromised) male. Traumatic
factors are often found in such cases (forceful or frequent use of cotton swabs, prosthesis
and exposure to swimming pool water).
 The most frequently involved pathogen is Pseudomonas aeruginosa, found in 75% to 90%
of cases.
 Clinical symptoms are otalgia, which worsens at night and purulent otorrhoea. Hearing
impairment is inconsistently present. An important otoscopic finding is granulation tissue
in the bone-cartilage junction of the external auditory canal. If the infection, while
spreading into the temporal bone, reaches the cranium, it may cause cranial palsies and will
consequently have poorer prognosis.
 The facial nerve is usually the first involved (in 20% to 50% of cases), resulting in facial
paralysis.
 A culture of ear secretions is required to investigate resistance to antibiotics. Pathologic
examination of granulation tissue is essential to exclude malignant processes.50 CT
scanning appears to be the more easily available and effective test.
 It is useful for assessing the location and extent of diseased tissue. Only early stages of
bone erosion may remain invisible on a CT scan.
 Technetium scanning (Tc99) has a sensitivity of 100% and when negative, may exclude
necrotizing external otitis.
 However, its poor specificity makes it inadequate for follow-up application. Gallium citrate
(Ga67) scintigraphy is suggested by a small number of authors for diagnosis; however,
scientific evidence to support this claim is unavailable. It is instead more frequently used
as a baseline for follow-up after treatment. Magnetic resonance imaging can be used to
assess the extension of disease toward the petrous apex, deep soft tissue spaces and
intracranial organs.

4.  The mainstay of treatment is systemic antibiotics, which are effective against Pseudomonas
aeruginosa. A common parenteral combination treatment associates a third-generation
cephalosporin (ceftazidime) with a fluoro-quinolone (ciprofloxacin) for a period of four-
to-six-weeks.
 Local treatment is also important and includes daily meticulous cleaning and debridement
of the auditory canal, with topical application of antimicrobial agents. Surgery currently
has a limited indication, as it may expose healthy bone to the infection. Nevertheless,
surgery remains recommended in the absence of improvement with adequate medical
treatment after two weeks.
 The addition of HBO will help control the infection primarily by:
o Preventing indirect tissue cell necrosis induced by oedema
o Exerting a bacteriostatic effect on anaerobic bacteria, which will limit or slow down
further expansion of the infection
o Optimizing the efficacy of antibiotic treatment
o Optimizing the leucocyte “bacterial killing” Capacity
Inner ear decompression sickness after scuba diving
 Even with early recompression treatment, the prognosis of IEDCS is not good. Up to 90%
of patients treated within six hours from the onset of symptoms retain residual
cochleovestibular symptoms.
 Recommendations for using treatment schedules at higher pressure and using
oxygenhelium mixtures as breathing gas seem to have less impact on the final outcome
than early recompression (ideally within one hour). In case of uncertain diagnosis
(especially in the case of inner ear barotrauma), a bilateral paracentesis is recommended to
obviate the necessity for Valsalva manoeuvres during compression.
 Several follow up HBO treatments may be given; however, early vestibular re-education
is also important.
 It is recommended that early caloric testing be performed to ascertain anatomical and
functional damage and at a later stage, pendulum chair testing, to verify the degree of
central compensation.
Complications of HBOT
 Complications of HBOT are rare and includes the followings:
1. Barotrauma is most common complication or side-effect of HBO therapy
 Middle- and inner-ear, sinus barotrauma
 The most frequent complication is difficultly equalizing pressure in the
middle ear, which occurred in 17% of patients and sometimes cause OME
which in most cases this will resolve without the need for VT insertion
 Pulmonary barotrauma
2. Oxygen toxicity
 Acute neurological oxygen toxicity
 Ophtalmologic changes
3. Claustrophobia and mask intolerance
Disadvantages of HBOT

5.  HBOT is an expensive and time-consuming intervention that is not readily available.
Therapy typically involves multiple sessions of 1–2 hours over days to weeks. Typical
treatments have consisted of between five and ten sessions.
 The evidence supports possible benefit of HBOT as an adjuvant treatment in cases of acute
SSNHL when used within 3 months of the onset of the hearing loss, with potentially more
benefit noted in cases of severe to profound loss.