Sumesh Arora on Dysbarism

DYSBARISM

Dr Sumesh AroraStaff Specialist

Department of Intensive Care MedicinePrince of Wales Hospital, Sydney

Kilo Pascal1000 N/m2

Psi Standard Atmosphere

mm Hg Cm H2O

1 atm 101.325 14.69 1 760 1033.1

1 psi 6.895 1 0.068 51 70

Conversion between the units of pressure

Atmospheric Absolute

ATA: 1Gauge reading: 0

30 psi = 2 atm3 ATA

Depth Pressure (ATA)

Surface 1

10 m (3 storey building)

2

Marina Trench: 10.9 Km

> 1000

Henry’s Law

16 °C2.7 ATA

16 °C1 ATA

Department of HBOT at POW

Basic mechanism of action

Increase in the solubility of all gases in blood at high pressure. Henry’s law

Attainment of very high oxygen level Displacement of toxins like CO from

haemoglobin Kills anaerobic organisms

Anti-inflammatory action of hyperbaric oxygen

Monoplace Chamber

•One patient at one time•Compressed with 100% oxygen•Greater fire hazard•Maximum pressure of approximately 2 ATA

Multiplace chamber

The ICU HBOT room

Very high P room

Commonest indications for HBOT requiring ICU Arterial gas embolism Necrotizing fasciitis and gas

gangrene Carbon monoxide poisoning Decompression illness

Arterial Gas EmbolismReferral and transfer for HBOT: Things to remember Diagnosis of AGE is clinical

supine position. Lateral decubitus with head down increases ICP

High concentration O2 is extremely important. If patient is intubated, use 100%

If air transfer: Possibility of exacerbation of injury due to

decompression and increase is size of bubbles

Necrotizing fasciitis and gas gangrene

Pain out of proportion to physical signs

In later stages, development of anaesthesia over the affected area indicate destruction of nerves

Easy separation of tissue planes at the time of debridement

Foul smelling exudate may suggest anaerobic infection

Hypocalcemia may be indicative of extensive fat necrosis

Imaging to diagnose Necrotizing fasciitis?

Really early in the course of disease, CT may identify gas

MR may overestimate the extent of deep tissue involvement

Treatment before transfer for HBOT

Early surgery and debriment. Commonest mistake is to refer for HBOT

before debridement Obtain tissue samples

Broad spectrum antibiotics

HbCO level

Normal < 1% <1%

Smokers: 10-12%

Mild CO Poisoning: 10-20%

Moderate CO poisoning 20-40%

Severe poisoning >40%

HbCO level does not correlate with severity of toxicity, response to therapy or prognosis

CO poisoning

Indications for HBO

Loss of consciousness

Focal neurological signs

HbCO levels > 25%

Pregnancy

If neurological symptoms are present, the HbCO level is irrelevant

Typical treatment schedule: 2.5 ATA, 90 min, 3 times

Carbon Monoxide poisoning: Things to rememberImmediate treatment with high concentration

oxygen is more important than referral to a unit with HBOT

Beneficial effect of HBOT may be unrelated to HbCOlevel, which is undetectable in most patients at start of treatment

Even minor toxicity in pregnant patient should be discussed with the hyperbaric unit due to slower fetal elimination

Practical issues when sending intubated patient for HBOT

Grommets for the tympanic membrane

Chest drain if pneumothorax

NG on free drainage

Replace the air from the ETT cuff with saline. Change to air at the end of the treatment

Contraindications for HBOT Difficult oxygenation/ARDS Pneumothorax Agitation Seizures Congenital spherocytosis Drugs

Bleomycin: Absolute contraindication Adriamycin with in previous one week. Cisplatin

Side effects of HBOT

Barotrauma: OticPulmonary

Oxygen toxicity

Refractory changes

Cataract

Abdominal doscomfort

When in doubt, speak with your referral HBOT

unit

Thank you