Hyperbaric Medicine II

Result FromMechanical Effects Increased Partial Pressure of Oxygen

remember that atm is 2.5-3atm.IN a deciL of blood (100mL?)=20cc of Oxygen. = 5L of blood - has 1L of OXygen bound to Hb in the body. Note that none is dissolved into blood.We extract 6cc of 02 per decil from arterial (33%)At 3atm, 100% o2, 6CC will dissolve into plasma - that allows us to support ourselves without any oxygen from Hb, within the HB chamber.n the lung between the alveolar wall and capillary wall is the interstitial space. (got to go through alveolar, capilarry and RBC cell wall).People xposed to 50% oxygen have....interstitial space is permanently expanded - now need to be on 100% oxygen.Oxygen of atm was 21%; we're making 100%.21%02 we put 100% at 10lL/min1l/breath 1 breath per sec0L/min=10000cc/sec166cc = max benefit+210 in rm air = 38%Without intubation, nobody gets more than 50% oxygen. Must be intubated and in a hyperbaric chamber.Without intubation, nothing is dissolved in plasma.Cant force it to dissolve in plasma without pressure.add 6cc, the other of 20cc can go to hypoxic tissues

following diving accidents or the iatrogenic introduction of intravascular air injecting with a syringe - can do up to 500mL of...and they still wont die. Not a problem until having pressure which pushes into venous blood....6cc/deciL of 02 that goes into the venous blood

Clostridium perfringens type a

magnitude of an embolism goes down by 2/3 in a chamber

add 6CC - the other 20CC can go to the ischemic areas

(at granulation tissue’ collagen secreted by fibroblasts; important for epithelial growth)

Shows the appearance of the right iposterior heel area and the resulting wound following dehiscence of the suture line after Achilles tendon rupture repair. This particular procedure had been performed four month previously with breakdown of the suture line within the first two weeks post-op. Additionally, transcutaneous oxygen measurements near the site of the wound clearly documented hypoxic regions of the soft tissue immediately adjacent to the edges of the open ulcer. Unsuccessful attempts at secondary closure led to consideration for the application of hyperbaric oxygen (HBO) therapy.

Shows the completely healed area of the Achilles tendon repair now five weeks following the completion of HBO therapy. The patient received 20 HBO treatments at 2.0 atmospheres absolute for 90 minutes each with routine wound care and supplemental oral antibiotic therapy. The patient has excellent range of motion and is ambulating without difficulty.

Gram-positive anaerobic rod-shaped bacteriaAssociated with penetrating wound contamination & anaerobic conditionsThrives in tissues with low oxygen tensionGas GangreneNecrotizing FascitisExotoxins (secreted by gram + bacteria) : Alpha & Theta toxins These destroy host tissues and inflammatory cellsCause hemolysis They suppress myocardial contractility-don’t die of infection; die of toxemia – with amputation, they will be better by tomorrow because toxin production has stopped.The Infection is characterized by: severe myonecrosis, gas bubbles & red or purple skin bullae. Microscopy/cytologynecrosis, gas bubbles, large Gram positive rodsHigh mortalityshock, renal failure, ARDS, multi-organ failure

Note red-purple bullae in skin; doesn’t involve the muscle. Vs. pyomyocytis starts in muscle – you have to amputate.Note necrosis (arrow heads) and gas bubbles (arrows) within tissue. Gas bubbles would produce crepitus on palpation.

Osteomyelitis

An injury caused by direct trauma or pressure. Damage related to crush injury can include laceration, open wounds, fractures, bleeding, bruising, compartment syndrome and others. The primary insult is tissue trauma, ischemia, and cellular hypoxia. Vasodilation in the tissue surrounding the injury leads to increased edema and further vascular compromise leading to ischemiacompromises the tissues ability to prevent infections

HBOT must be started within 24 hour of the burnpreferably ASAP

Lipid peroxidation Free radical damage to lipid (cell) membranesOne of the main causes of tissue injury following reperfusion of hypoxic tissueAbsolutely oxygen dependent

There are some experimental results that suggest that HBO has a suppressive effect on both humoral and cell-mediated immunity

Oxygen inhibits enzymes involved in the synthesis of surfactant may also inhibit the transport of surfactant to the alveoli Gilder and McCherry (1974).

(Radiation Tissue Damage – vasculitis – blood vessels reduce in number over time after radiation)

Complication during ascent phase of treatmentAir volume increases in the pleural cavity, doubling or tripling, as atmospheric pressure is approached

If pneumothorax occurs in the multiplace chamber under pressure, it must be relieved surgically before decompression If pneumothorax occurs in the monoplace chamber, a McSwain dart or other chest tube is made ready, the chamber is decompressed not taking longer than 1 min, and the chest tube inserted as the patient emerges

HBO and doxorubicin given together has caused death in rats probably from cardiac toxicity HBO may increase the cytotoxic effect of cis-platinum in the tissue of chronic wounds, inhibiting healing.Any patient who has a non-healing wound and is receiving cis-platin will not be helped, and may be worsened by HBOT

Occasionally used to treat alcoholismInhibits metabolism of alcohol which leads to an accumulation of acetylaldehyde causing headache, nausea, dyspneaAntabuse blocks the production of superoxide dismutase which protects the body from oxygen toxicity. Contraindicated in conjunction with multiple HBO treatments.

Bleomycin chemotherapeutic agent used to treat a variety of tumors including head and neck, lymphomas, and germ cell testicular tumors

Pulmonary toxicityBleomycin can cause pulmonary toxicity leading to interstitial pneumonitis and fibrosis.Increased oxygen tension seems to accelerate this side effect.HBOT may cause rapid pulmonary deterioration and result in fibrosis

O2 in premature infants can cause retrolental fibroplasia (fibrosis on the surface of the retina)  blindness HBO is contraindicated in premature infants Full-term babies may be safely treated with HBO

surgical scarring may have produced air-trapping lesions

removal of the hypoxic drive may cause respiratory arrest

may make it difficult for the patient to equalize pressure in the ears and sinuses decongestants are indicated

for treatment of otosclerosis a wire or plastic strut might be displaced if the patient cannot equalize pressure in the earstympanostomy tubes may be needed

may increase susceptibility to O2 seizurespremedication (with diazepam) may be advisable

may predispose to O2 seizures should be reduced before placing the patient in the chamber

may worsen with HBO reason to temporarily interrupt daily treatment of some chronic illnesses some authors feel that acute viral infections are a contraindication to HBO therapy because they may be severely exacerbated

Most common complication of HBOT It is inherently more difficult to inflate the middle ear because the inner ends of the Eustachian tube (fossae of Rosemueller in the naso-pharynx) have slit-like openings. These openings tend to close tighter if they are not open actively. If the patient has descended more than about one meter without clearing the ears, it will be impossible to voluntary open the tubes through swallowing, yawning, or doing the Valsalva maneuver The chamber pressure will have to be slightly decreased to facilitate ear clearing

Extremely rare complication caused by the vigorous performance of the Valsalva maneuverUsually reported in divers Very rare in a clinical hyperbaric patientsNormally, in an unconscious patient, the tympanic membrane ruptures before the round window gives wayRound or oval window blowouts usually produce immediate deafness, tinnitus and vestibular symptoms such as nystagmus and vertigo 2 Possible Mechanismsimplosiveexplosive

During descent pressure is transmitted from an inward bulging eardrum, causing the ossicles to move toward the inner ear at the oval window This pressure wave is transmitted through the inner ear and causes an outward bulging the round window membrane If a diver performs a forceful Valsalva maneuver and the eustachian tube suddenly opens, a rapid increase in middle ear pressure occurs. This causes the ossicles to suddenly return to their normal positions, causing the round window to implode

When a diver attempts to clear a blocked middle ear space by performing a Valsalva maneuver and the eustachian tube is blocked a dramatic increase in the intracranial pressure occurs Since the fluids surrounding the brain communicate freely with the inner ear fluids, this pressure may be transmitted to the inner ear A sudden rise in the inner ear pressure could then cause the round or oval window membrane to explode

Occurs if any of the openings to the various sinuses to the head are blocked by an overgrowth of tissue, edema, or mucusVery painful and the patient should undergo slow compression.Decongestants

May occur particularly when HBOT is given at more than 2.4 atm Some patients are idiosyncratically susceptible to high O2 partial pressuresTreatment: discontinue of the O2Incidence of seizure is low 1.3/10,000 treatments

Substernal chest pain, cough, and patchy atelectasisMay occur but is usually not seen if treatment protocols are adhered to

After 20 or 30 HBO treatments some patients complain of numbness in the fingersUsually ulnar distributionDisappears 4 to 6 weeks after therapy Mechanism unknown

May result from daily HBO Usually minor problem Treatment: decongestants

Myopia worsens, presbyopia improves Due to alteration in the shape of the lensnot cornea Cause of shape change not knownUsually resolves completely following HBOTsome individuals refractive error may not completely revert to its pretreatment level rare It has been suggested, but not proved, that preexisting cataracts mature more rapidly with HBOT

Rarely, patients will suffer tooth pain during compression or decompression Typically caused by an air space under a filling or restorationCompression forces the pulp into the air space which causes exquisite pain

Approximately one out of 50 patients exhibit some degree of confinement anxiety in multiple chambersrarely severe enough to require sedationMono-place chamber can be very anxiety provokingApproximately one patient in 10, using the 25- inch mono-place chamber will have claustrophobia severe enough to make treatment difficult or impossible