Hyperbaric Oxygen Therapy

Question 1

Most HBO therapy consists of

Answer 1

pressures between 2.0 and 3.0 ATA
with each session lastin 90 to 120 minutes

Question 2

Gas toxicities where HBOT may be indicated

Answer 2

Carbon monoxide poisoning
Cyanide poisoning

Question 3

Infections where HBOT may be indicated

Answer 3

Clostridial myonecrosis (gas gangrene)
Necrotizing soft tissue infections
Intracranial abscess*
Refractory osteomyelitis*

* usually nonemergent indications

Question 4

Acute ischemic events where HBOT may be indicated

Answer 4

Arterial gas embolism
Blood loss anemia, exceptional
CRAO
Decompression sickness
hEaring loss, acute sensorineural

Question 5

Accounts for the greatest proportion of iatrogenic gas embolism

Answer 5

the introduction of intravascular sheaths,
such as at the start of an interventional radiologic procedure

Question 6

Initial management for arterial gas embolism

Answer 6

Supplemental oxygenation (to support arterial oxygenation and hasten bubble resorption)
Supine position (NOT Trendelenburg or left lateral)

Question 7

Conditions where HBOT is the definitive treatment

Answer 7

Arterial gas embolism (AGE)
recommended when there is neurologic or cardiovascular impairment

Decompression sickness
receommended in all cases of diving decompression sickness

Question 8

Start HBOT in AGE when?

Answer 8

ASAP
but there is evidence of improved outcomes out to 60 hours or longer

Question 9

If HBOT is not available , what is the management for patient with mild symptoms, and stable for longer than 24 hours?

Answer 9

May be treated with supplemental oxygen alone.

Question 10

If a patient must be transported by air to a hyperbaric facility, use

Answer 10

pressurized aircraft to maintain sea-level pressure

or transport at the lowest possible altitude in a nonpressurized craft, such as a helicopter

Question 11

Remarks on the management of decompression sickness

Answer 11

Most patients with decompression sickness who receive rapid HBOT will respond to a single treatment

USNT table 9 may be used in patients with residual symptoms

Question 12

CRAO occlusion is often the result of

Answer 12

cholestero embolus,
and so not treatable with thrombolysis, leading to poor outcomes

Question 13

In CRAO, HBOT produces a clinically significant visual improvement especially when instituted when?

Answer 13

within 24 hours of onset

There are no other CRAO therapies with similar outcomes.

Supplemental oxygen and lower intraocular pressure are recommended until HBO can be initiated

Question 14

Duration of HBOT for CRAO

Answer 14

Done twice daily and contintued until there is no visual improvement for 3 consecutive days

Question 15

Sudden sensorineuroal hearing loss is

Answer 15

hearing loss of at least 30 dB occurring over 3 days involving at least 3 contiguous auditory frequencies

Question 16

The usual presentation of sudden sensorineural hearing loss

Answer 16

awaking from sleep with a sudden unilateral hearing loss, aural fullness, and at times tinnitus and vertigo

cause is unclear

Question 17

Management of profound sensorineural hearing loss

Answer 17

HBOT is indicated for profound sudden sensorineural hearing loss (>40 dB)

In combination with steroids, HBOT produces hearing gains over all frequencies

Question 18

timing of HBOT in sensorineural hearing loss

Answer 18

started within 14 days of symptom onset.

AAOHNS advocates HBOT for up to 3 months after symptom onset

Question 19

HBOT in anemia

Answer 19

useful in acute severe anemia where transfusion cannot be used (e.g., Jehovah’s Witness, Rh incompatibility, patient refusal)

Question 20

HBOT protocol for severe aemia

Answer 20

100% oxygen at 2.5 to 3.0 ATA for 3 to 4 hours (with air breaks) up to 4x daily until RBC improves [via erythropoietin]

Question 21

HBOT in compartment syndrome

Answer 21

Helps both preventing need for fasciotomy

and accelerating recovery from fasciotomy

Question 22

The induction of gas gangrene requires only

Answer 22

the presence of clostridial spores and
a region of lowered oxidation reduction potential caused by local circulatory failure or extensive soft tissue damage and muscle necrosis

under the conditions of low oxygen tension, the clostridial spores can develop into the vegetative form

Question 23

Most prevalent exotoxin in clostridial gas gangrene

Answer 23

Alpha toxin
causes platelet and leukocyte destruction, widespread capillary damageg, hemolysis, tissue necrosis, and often death

Question 24

Prognosis of gas gangrene

Answer 24

Alpha toxin can be detoxified within hours after its elaboration, with natural host defences conferring active immunity with production of a specific antitoxin

However, death often occurs because the infection is so rapidly progressive that the patient dies before immunity can develop

In several series, no mortality has been shown after the third HBO session (end of day1)

Question 25

Treatment of gas gangrene begins when

Answer 25

with an index of suspicion and a positive gram stained smear of the wound fluid revealing gram-positive rods and a paucity of leukocytes

Question 26

Gas gangrene treatment's three-pronged approach

Answer 26

Antibiotics Surgery HBOT *The initial surgery can be restricted to opening of the wound or an initial fasciotomy, followed by immediate HBOT.*

Question 27

Most common adverse effect of HBOT

Answer 27

Middle ear barotrauma

Question 28

Pulmonary barotrauma as complication in HBOT

Answer 28

extremely rare, but should be suspected with development of chest or hemodynamic symptoms

Question 29

if pulmonary barotrauma symptoms develop and the patient is in multiplace chamber...

Answer 29

...stop decompressoin and evaluate for pneumothorax

Question 30

if pulmonary barotrauma symptoms develop and the patient is in monoplace chamber...

Answer 30

Slowly decompress and provide supplemental oxygen upon returning to ambient pressure

Question 31

Acute oxygen toxicity manifests as

Answer 31

Grand mal seizures

Question 32

Management of seizures related to acute oxygen toxicity

Answer 32

Reduce the inspired oxygen tension while leaving the patient at the same pressure *(to avoid pulmonary overexpansion injury when a patient is in tonic-convulsion phase)*

Question 33

Complications of chronic oxygen therapy

Answer 33

Progressive myopia *(typically reverses within 6 weeks after stopping HBOT)* Nuclear cataract *(when treatments exceed >150-200 hours)*

Question 34

HBOT's fetal effects

Answer 34

Current evidence does not indicate that typical HBOT protocols have detrimental effects on neonates or the unborn fetus

Question 35

Miscellaneous complications of HBOT

Answer 35

Confinement anxiety Risk of fire - *scrupulous avoidance of an ignition source is standard in HBOT programs*