What happens in the chamber?

Mattijn Buwalda

Anesthetist-intensivist

& Diving Medicine Physician

Runtime: 40 min

Slides: 32

The chamber - content

• indications HBOT

• beneficial effects of HBOT

• side effects

• different tables

• organization, team

• Safety

• tank for one or more patients

• variable pressure (> 1.4 bar)

• variable time

• variable schedule

• patients breath O2

What is HBOT?

Goal: increase tissue PO2

3

HBO blue print

4

1. decompression sickness 2. air or gas embolus 3. severe CO poisoning 4. clostridial myonecrosis 5. necrotizing fasciitis 6. crush injury & compartment syndrome 7. non-healing hypoxic wounds 8. radiation bone and soft tissue necrosis 9. refractory osteomyelitis 10. severe haemorrhagic anaemia 11. compromised skin flaps and grafts 12. severe thermal injury (burns)

ECHM accepted indications

College voor zorgverzekeringen. www.cvz.nl 23-2-2009

Not in NL

5

Oxygen Ambient

pressure

Pio2

mmHg

Arterial Hb

bound O2

PaO2

mmHg

Dissolved

plasma/tissue

ml/dl

21% 1 bar 160 20 ml 100 0.31 ml

100% 1 bar 760 20 ml 700 2 ml

100% 2 bar (10 MSW) 1520 20 ml 1400 4 ml

100% 3 bar (20 MSW) 2280 20 ml 2100 6 ml

Oxygen content

Oxygen content in ml O2/ dl blood = (2 x Hb x SPO2) + (0.0031 x PaO2) Hb = 10 mmol/L

1 bar = 1000 mbar = 760 mmHg

Pao2 (predicted) = Fio2 x (760x PATA – PH2O) – [PaCO2/R] x [a/Aair]

6

Dissolved O2

• extraction 25% = 5 ml O2/ 100 ml blood

• dissolved O2 @ 3 bar ATA = 6 ml/100 ml blood

• anemic oxygenation!

Boerema I, Meyne NG, Brummelkamp WK, et al: Life without blood. A study of the influence of high atmospheric pressure and hypothermia on dilution of the blood. J Cardiovasc Surg 1960;1:133-146 7

Krogh cylinder

Capillary 30-60µm from tissue cell 8

Bigger cylinders

HBO arterializes the venous blood!

9

• HBO only works if there still is some tissue perfusion!

Tissue perfusion

10

Mechanical effects of HBO

From 1 > 2.8 bar volume reduction 73% diameter reduction 35%

11

pN2 = 0

pO2 = 2.8 bar

Increased N2 gradient

100% O2 @ 2.8 ATA

O2

12

alveolus

tissue dissolved N2

N2 bubble

Why do bubbles eventually disappear without O2 or recompression therapy?

Oxygen window I

https://www.globalunderwaterexplorers.org/effect-hyperbaric-oxygen-oxygen-window

PN2 = 637 Ptot = 760

P N2 = 573 Ptot = 696

Oxygen window II

PN2 = 637 Ptot = 760

Oxygen window III

The higher the O2 window, the faster N2 is eliminated from the tissues

• 125% increase of oxygen content

• 10 x increase tissue & plasma PO2

• 3 x diffusion distance (Krogh cylinders)

HBOT: primary effects

16

HBOT: secondary effects

arteriolar & venous vasoconstriction

↑ neutrofil oxidative killing

↑ fibroblast & osteoblast function

↓ endothelial neutrofil adhesion

↓ proinflammatory cytokines

↑red cell deformabillity

don’t function if tissue < PO2 30

mmHG

↓art. inflow ↓edema formation

all promote tissue perfusion and oxygenation

cerebral edema in CO intox and AGE, DCI spinal cord, crush, grafts

tissue infections

ischeamic wounds

post radiation

crush

compartment

burns

grafts

DCS & AGE

17

• HBO antagonizes the effect of .NO on vascular tone

– NO scavenging by superoxide producing peroxinitrite: .NO + .O2

- > ONOO-

– Decreased .NO release by the RBC

• does not cause tissue hypoxia!

• causes reduction of tissue edema

HBOT induced vasoconstriction

Demchenko IT, Boso AE, O’Neill TJ, et al. Nitric oxide and cerebral blood flow response to hyperbaric oxygen. J Appl Physiol 2000;88:1381-1389 Allen BW, Piantadosi CA. How do red cells cause hypoxic vasodilation? The SNO-hemoglobin paradigm. Am J Physiol Heart Circ 2006;291:1507-1512

18

• HBO reduces adhesion of PMN to injured endothelium (down regulation of CD11/18, integrin protein on surface of PMN and monocyte)

• reduces ICAM-1 expression (endothelial PMN-receptor)

• promotes microvascular perfusion

Endothelial effects

Thom SR: Functional inhibition of leukocyte B2 integrins by hyperbaric oxygen in carbon monoxide mediated brain injury in rats. Toxicol Appl pharmacol. 1993;123:248-256 Hong JP, Kwon H, Chung YK, et al. The effect of hyperbaric oxygen on ischemia-reperfusion injury: an experimental study in a rat musculocutaneous flap. Ann Plast Surg 2003;51:478-487

19

• vasoconstriction varies from organ to organ

• most profound in:

– brain

– retina

– heart

– skeletal muscle

• increased SVR and

• prominent bradycardia (not only vagal)

Hemodynamic effects

Fagreus L, Linnarsson D. Heart rate in the hyperbaric environment after autonomic blockade. Acta Physiol Scand 1973;9:260-264

20

• 10% of the CO2 in venous blood is removed during lung passage

• CO2 transport in blood: – HCO3

- (87%)

– Carbamate Hb (8%)

– Dissolved (5%)

• Haldane effect: – ¼ of the AV CO2 content difference

– absent in HBO !

– compensated by mild hyperventilation

Ventilatory effects

Lumb AB: Carbon dioxide. Nunn’s Applied Respiratory Physiology, 6 th ed. Philadelphia, Elsevier Butterworth Heineman, 2005, pp148-165

21

Hemiplegia after CVC insertion

only air in • ophthalmic vein • central venous sinus • brachiocephalic vein

22

Pathofysiology

• VGA

• gravity

• local endothelial activation

• leucocyte adhesion

• stasis > venous infarction!

• takes some time for neurological symptoms to develop!

Venous air entry

• diving

• central venous catheter • insertion

• removal

• manipulation

• peripheral line

• neurosurgery (sitting)

• CABG

• Prostatectomy

• hip/spine surgery

• caesarean section

Venous gas emboli

neurological signs after CVC manipulation? think of HBOT!

Bothma P, Brodbeck AE. Cerebral venous air embolism treated with hyperbaric oxygen: a case report. Diving and Hyperbaric Medicine Volume 42 No. 2 June 2012

23

• claustrofobia

• hypertension

• dense air

• barotrauma

• myopia

• cerebral oxygen toxicity

• pulmonary oxygen toxicity

HBOT side effects

ICU related:

• cuff volume

• pressure bags

• pressure transducers

• drains

• drip chambers

• certified equipment

24

U.S. Navy table 5

U.S. Navy table 6

27

Wound table 14 msw

• supervisor chamber operator

• assistent chamber operator

• inside medical attendent

• hyperbaric physician

HBOT team

28

• fire hazard

– cotton clothing

– no electronical equipment

– sprinklers

– air athmosphere

• medical attendent

• certified staff and equipment

Safety and HBO

29

• Diving bell accident On 5 November 1983 at 4:00 a.m., while drilling in the Frigg gas field in the Norwegian sector of the North Sea, four divers were in a decompression chamber system attached by a trunk (a short passage) to a diving bell on the rig, being assisted by two dive tenders. The four divers were

• Edwin Coward (British, 35 years old) Roy Lucas (British, 38 years old) Bjørn Giæver Bergersen (Norwegian, 29 years old) Truls Hellevik (Norwegian, 34 years old)[10] Hellevik was about to close the door between the chamber system and the trunk when the chamber explosively decompressed from a pressure of nine atmospheres to one atmosphere in a fraction of a second. One of the tenders, 32-year-old William Crammond of Great Britain, and all four of the divers were killed instantly; the other tender, Saunders, was severely injured.[10]

Explosive decompression.....

Explosive decompression.....

Thank you for listening! 32