Hyperbarics

HBO2 = Hyperbarics

60 or so centers in US that are able to do critical care hyperbaric medicine. (800-900 centers can do hyperbaric wound care)

Definition: anything greater than 1 atm (sea level) of pressure. For billing purposes, greater than 1.4 atm of 100% oxygen (98+%)

Monoplace chamber = 1 person (3h runs); Multiplace chamber = multiple people, delivered by mask. (Typically, 2 atm for 90-120 minutes)

Physiologic effects:

Bubble volume reduction
Increased blood/tissue PO2
Gas washout
Vasoconstriction (in some vascular beds)
Neovascularization (use cases: OM, chronic wounds, post-radiation)
Increased WBC oxidative killing -> particularly useful for nectoxins from clostridium / anaerobes + toxins
modulation of ischemia/reperfusion
Increased growth factor receptors (contributes to neovascularization)

Hyperbaric Oxygen Therapy Indications 14th edition is reference

Gas embolism
CO poisoning
Clostridial myonecrosis and nec fasc (particularly, if there is concern for progressive necrosis despite debridement - even if nec fasc is not due to clostridial species - which classically causes more of a myonecrosis and less of a fasciitis, though there is often some degree of each)
Crush injury
Decompression sickness (60 ft water = 3 atm; 1 psi/min is fastest rate)
Problem ischemic wounds
Acute sensorineural hearing loss
Exceptional blood loss
Osteomyelitis
Radiation tissue damage
Skin grafts and flaps
Thermal burns
Intracranial abscess
Acute retinal occlusion

Need for deep sedation (+/- neuromuscular blockade) due to limited ventilator (no assist modes - just control modes; Sechrist 500A ventilator. Only control flow, I time, E time. No alarms). Hypercapnia -> can worsen O2 toxicity because CNS blood flow increases. This often becomes an issue when the ventilator is limited in ability to deliver breaths quickly.

Hospital wall oxygen 55 PSI - often insufficient to create adequate driving pressure. Thus, IHC uses manifold (85 PSI) or direct in corner room STICU (direct 120 PSI)