1. Hyperbaric Oxygen Therapy
Yan Wing Wa
Intensive Care Unit
Pamela Youde Nethersole Eastern Hospital
6 June 2005

2. Contents Physics of hyperbaric therapy
Physiological changes in hyperbaric conditions
Indications / Contraindications of hyperbaric therapy
Hyperbaric therapy in Hong Kong
Protocol of hyperbaric therapy
+/- HBO therapy for carbon monoxide poisoning

3. Physics of hyperbaric therapy / diving
One atmosphere (At)
= (10 metres sea water (msw)
= (33) feet sea water (fsw)
= 33.9 (34) feet fresh water
= kg/cm2
= (14.7) lbs/in2 (psi)
= (1) bars
= 1013 millibars
= 760 millimetres mercury (mmHg)
= 760 torr

4. Absolute pressure (Pabs)
Atmospheric pressure + Gauge pressure / Water pressure
e.g. sea surface = 1 ATA
10 msw = 2 ATA
18 msw = 2.8 ATA

5. Pascal’s principle
A pressure applied to a liquid will be transmitted “equally” throughout the liquid.

6. Ideal Gas Law
P1 x V1 =
P2 x V2 T1 T2
P x V = N x R x T

7. Boyle’s Law
P1 x V1 = P2 x V2
At constant temperature the volume of a given mass of gas is inversely proportional to the absolute pressure
Volume changes are greatest near the water surface

10. Charles’ Law P P1 P2 = constant; = T T1 T2 P P2 = T T2
Vs: Adiabatic heating (Second Law of Thermodynamics)

11. Dalton’s Law Pabs = PgasA + PgasB + PgasC PgasA = Pabs x FgasA
The total pressure exerted by a mixture of gases is the sum of the partial pressures that would be exerted by each of the gases if it alone occupied the total volume
Atmospheric air (20% O2 and 80% N2)
1 ATA = 0.2 ATA O2 and 0.8 ATA N2
5 ATA = 1.0 ATA O2 and 4.0 ATA N2

12. Respiratory Gases
Pabs –
VSTPD = VBTPS x ( ) x

13. Henry’s Law
Q = K x P gas
Q (volume of gas dissolved in liquid) = K x Pgas
Q with Temp
At constant temperature, the amount of gas that will dissolve in a liquid is proportional to the partial pressure of that gas over the liquid
1 ATA = x litres of gas in solution
10 ATA = 10x litres of gas in solution
As pressure is reduced solubility falls
Most gas excreted by lung
Rapid ascent may lead to bubble formation

15. Nitrogen Narcosis Pressure Effect of Nitrogen 2-4
Performance impairment, euphoria 4
Impaired reasoning
4-6
Delayed audio / visual response
Calculation errors, loss of self control 6
Sleepiness, delusions
6-8
Dizziness, hysteria 8
Severe intellectual impairment
8-10
Delay in response, confusion 10
Stupor
>10
unconsciousness

17. Inert Gas Narcosis Effects are of rapid onset and recovery
Effects potentiated by
fatigue, narcotics, EtOH, CO2 retention
Adaptation possible, no true tolerance
Avoid making decision inside hyperbaric chamber
Other inert gases
Helium – no narcotic effect, neon less narcotic
Argon, krypton, xenon more narcotic

18. Gas Diffusion
Net movement of gas molecules from an area of higher partial pressure to an area of lower partial pressure.
 with  molecular weight of gas
 viscosity of liquid
temperature of liquid

19. Gas Flux
= gases diffusion x Q
LaPlace’s Law
P  = 2 x  / r

20. The Mechanism of Barotrauma
Barotrauma of Descent
Middle ear
Pulmonary
Sinus
Barotrauma of Ascent

21. Physiological Changes in Hyperbaric Condition – Respiratory system
Changes in compliance
lung and chest wall
Changes in airway resistance
only in turbulent flow
Changes in work of breathing
Changes in V/Q match
 shunt
Changes in DO2
Ca O2=19.5ml%(Hb bound) + 0.3ml%(dissolves) = 19.8ml%
CV O2=15.0ml% ml% = 15.1ml%
Ca O2=19.5ml% ml% = 26.2ml%
(at 100% O2 3ATA)
Changes in CO2 transport
less efficient in HBO environment
  reduced Hb in venous blood 
 carbamino compound with CO2
Changes in control of respiration
? slight depression of respiration drive in HBO

22. Cardiovascular System
Changes in blood volume distribution
Dive reflex:  heart rate
Blood pressure : same

23. Decompression Illness (DCI)
Uptake of inert gases (descent)
Elimination (ascent)
Bubbles formation
Biochemical damage (Inflammatory cascade)
DCI (within 24 hours)
Non-specific symptoms and signs
Brain (sensory > motor)
Spinal cord (retention of urine with overflow)
Vestibular disease
Musculoskeletal disease
Respiratory disease
(~ O2 toxicity, pulmonary barotrauma, asthma, salt water aspiration)

24. Oxygen Toxicity
Syperoxide anion [O2] generated as normal product of oxygen metbolism
O2 is highly reactive free radical
Sulphydryl group dependent enzymes
Unstaurated lipids
Membrance bound transport systems
O2 Controlled by antioxidant mechanisms
Superoxide dismutase, catalase, vitamins
O2 / antioxidant balance disturbed by increase pO2

25. CNS Oxygen Toxicity Paul Bert effect Major symptoms is convulsion
fibrillation of lip/cheek, pallor, palpitations, bradycardia, sweating, apprehension, nausea, vertigo, disturbed respiration, twitching, hallucinations
Contributory factors
Exercise, CO2 retention, previous hypoxia
Management
Off oxygen until symptoms resolved
Convulsions with diazepam IV

26. Pulmonary Oxygen Toxicity
Lorrain-Smith effect
Threshold pO2 0.5 – 0.75 ata
Symptoms
Irritation on deep inspiration, cough, burning on inspiration, paroxysms of cough, breathlessness
Signs
Reduced vital capacity, desaturation on exercise
Management
Reduce pO2 – recovery from all but most severe episodes
Control
Intermittent exposure (air or chamber gas breaks)

27. RN Table 60 - Hyperbaric Oxygen Therapy
Gauge Depth (msw)
Stops/Ascent (minutes)
Elapsed time (hours and mins)
Rate of Ascent (msw/minute) 18
25 (O2)
00: :25 -
5 (Air)
00: :30
00: :55
00: :00
18 - 0
30 (O2)
01: :30
3 m in 5 min
Surface
01:30

28. Oxygen Toxicity Dose may be calculated by UPTD
Unit Pulmonary Toxic Dose
Assumes pO2 0.5 no effect
UPTD little use because of variability in susceptibility
Main control is by use of intermittent exposure

29. Oxygen Toxicity Toxicity dependent on pO2 and duration of exposure
pO2 > 3 ata – CNS symptoms dominant
pO2 > 2 ata – Pulmonary symptoms dominant
Considerable variability in susceptibility
Between individuals
From day to day
Symptoms may occur soon after reduction in pO2

30. Oxygen Toxicity  fever  work  CO2 retention steroid anxious
adrenaline /noradrenaline
high dose penicillin
insulin infusion
thyrotoxicosis

31. Carbon Dioxide Retention
Direct result of alveolar hypoventilation, dense gas, breathing apparatus, poor scrubbing
Symptoms
Headache, sweating, palpitations, breathlessness, peripheral vasodilatation
Ultimately brain stem depression and cessation of breathing
Not specific
Interactions with O2 toxicity and decompression sickness

32. Indications for HBO –Undersea and Hyperbaric Medical Society (UHMS)
Related to diving and compressed air work
decompression illness
Air or gas embolism
Acute conditions
Carbon monoxide poisoning
Clostridial myonecrosis
soft tissue necrotising infections
Crush injury, compartment syndrome and other traumatic ischaemias
Exceptional blood loss anaemia

33. Mechanisms of action and effects of HBO
Increase of oxygenation of tissue fluids
Reduction in tissue oedema
Increased capillary proliferation
Increase in fibroblast growth
Increase in collagen formation
Decrease lipid peroxidation by PMN leucocytes

34. Side Effects of HBO Treatment
Cough, dyspnoea
Barotrauma
ear drums, sinuses
pulmonary
Oxygen toxicity
retrosternal discomfort, pulmonary oxygen toxicity, convulsion
Decompression Illness (Chamber attendants)
Fire Hazard!

35. Contraindications Abnormal Eustachian Tube function
e.g. Upper respiratory tract infections or sinusitis
ENT assessment to ensure normal Eustachian tube function
prophylactic myringotomy if necessary
Drug therapy with
doxorubicin, disulfiram, bleomycin, cisplatin or mafenide acetate
Untreated pneumothorax

36. The Recompression Treatment Centre (RTC)
Up to 1994, recompression therapy was provided by UK Royal Navy
RTC opened in 1994
Operated by HK Fire Services Department
Maintenance by EMSD
Medical supervision offered by Occupational Medicine Division, Labour Department
Intensive Care supported by ICU, PMH, ?now

39. Referral to Occupational Medicine Division, LD
Emergency
Notified Fire Service Department
Contact first call Occupational Health Officer and discuss the management plan
Transfer patients to RTC with referrals and medical records
Accompanied by medical staff of the relevant units

43. Control Panel with Fireman

44. Control Panel

45. Control Panel

46. Control Panel

47. Entrance to Chamber

49. Emergency Trolley

50. Medical equipments and consumables

51. Communication Lock

52. Drinking Water and Washing Basin

53. Communication with outside

54. Communication with outside

55. Communication with Entry Lock

57. Entry Lock with Sanitary Facilities

58. Entry Lock

59. Exit From Entry Lock

60. Multiplace chamber Advantages Ill patients Less claustrophobia
Sputum suction
Physical exam
Higher pressure
Less claustrophobia
Allow tenders in and out
Disadvantages
Expensive
More operators
Mounted on heavy foundation

61. Royal Adelaide Hospital

62. Monoplace chambers Advantages Cheap One operator to many chambers
Can be installed in existing patient room
Disadvantages
Claustrophobia
No suction / examination/ intervention like CPR during treatment
Most chambers maximum pressure are 3 ATA

63. Monoplace chambers

64. Protocol for ICU Patients Undergoing Hyperbaric Oxygen (HBO) Treatment
Introduction
1. Hazards exist if HBO therapy is not done with proper preparation and monitoring.
2. Balance between benefit obtained from HBO therapy and risk associated it’s use should be considered by ICU doctors.

65. Introduction
3. Medical conditions requiring special consideration before HBO therapy:
Respiratory
Chronic obstructive lung disease (emphysema)
Asthma
Upper respiratory infection
History of thoracic surgery
History of spontaneous pneumothorax
Pneumothorax (all pneumothorax should be drained prior to HBO therapy)
Chest x-ray film with asymptomatic pulmonary lesions
Otolaryngologic
Chronic sinusitis
History of ear surgery

66. Introduction 3. Ophthalmologic History of optic neuritis Neurologic
Seizure disorder
Hematologic
Congenital spherocytosis
Systemic
Viral infections
Hyperthermia (uncontrolled high fever)
Untreated/metastatic malignancy (controversial)
Miscellaneous
Pregnancy
4. Try to simplify patient’s treatment and monitoring before HBO therapy.

67. Procedures (cont.)
5. Probable risk of HBO therapy should be explained to patient and patient’s relatives, if any. Consent by patient or minor should be obtained before initiation of HBO therapy.
6. Experienced ICU doctor should accompany the patient throughout the whole procedure although he/she may not need to enter into the pressure chamber.
7. Doctors on-call of the Hyperbaric chamber should be contacted directly

70. Procedures (cont.) 8. ETT/Tracheostomy tube
Use water to inflate the cuff.
9. Mechanical ventilator systems
Oxylog 1000 is to be used for ventilating patient in the hyperbaric chamber. When the chamber pressure is changed, the tidal volume delivered to the patient will change accordingly. Calibration table should be referred to during treatment (Appendix 1).
Wright’s spirometer should be connected into the ventilator circuit for tidal volume monitor.
Anaesthetic PEEP valve can be attached if PEEP is required.

71. Oxylog 1000 (serial number : ARNG-0054) had been calibrated with the use of Wright’s spirometer (Ohmeda) inside the hyperbaric chamber at Stonecutter Island. It should be noted that additional marking is made on the frequency and minute volume knobs. However, the minute volume delivered is not very exact. Wright’s spirometer should be used for monitoring tidal volume, if necessary.

72. Ventilator

76. Procedures (cont.) 10. Chest tube drainage systems
Must have thoracostomy apparatus ready within vicinity of chamber for emergency procedures.
- Chest drain box
Maintain suction, monitor air-fluid levels during ascent/descent.
May substitute with one-way valve (e.g., Heimlich valve).
11. Oxygen breathing device (built-in breathing device)
Use of oxygen within chamber must be controlled carefully (use only tight-fitting aviator masks or hoods or endotracheal/tracheostomy tubes).
Only aqueous solutions should be used because of fire hazards

77. Oxygen Mask

78. Oxygen Mask

79. Hood for HBO

80. Procedures (cont.) 12. Intravenous (i.v.) infusion equipment
- AVOID Glass i.v. bottles
- i.v. infusion pump/syringe pump
Consider potential fire hazard, preferably purging continuously with nitrogen.
Frequent alarming; must disarm “anti-infiltration” switch. Readjust at depth.
Use JMS SP100S syringe pump which perform satisfactorily within chamber
- Tubing
Ensure absolutely no air entrainment. Avoid puncturing rubber injection sites (use 3-way stopcocks) Safeguard against disconnection.

81. Procedures (cont.) 13.Nasogastric tubes
Leave unclamped or on intermittent suction.
14.Central line placement
Avoid subclavian puncture. Use femoral or internal jugular veins.
- Pulmonary artery catheters
Ensure that balloon at catheter tip is deflated and balloon port must be left open.
Obtaining wedge pressure during the dive is not recommended.

82. Procedures (cont.) 15. Monitoring equipment
SpaceLab Monitor is available for use in the chamber. Can substitute individual patient’s modules for monitoring.
Minimise use of instrument within the chamber.
Do not use portable monitors with cathode ray tubes at depths greater than 3ATA. Considering purging interiors continuously with nitrogen to avoid ignition. LCD monitor is safe to be used inside the chamber
Intravascular pressure monitoring systems (e.g., Intraarterial pressure)
Pressure bladder
Further inflate pressure bag during compression, appropriately deflate during decompression.
Tubing
Avoid air entrainment (because it may be injected into patient or interfere with signal transmission).
Zeroing
Zero pressure transducer with reference to chamber pressure in the standard way.

83. Hyperbaric Chamber

84. Chamber and Monitoring Equipment

85. For Monitoring Equipment

86. Medical Examination Equipment

87. Procedures (cont.)
Cardiac output computers must be specially adjusted.
Function of pulse oximeters/capnographs may be unreliable. For blood gas analysis, must either use specially adjusted equipment within chamber, or expect spurious results if sample is analyzed at surface (due to “off-gassing”). pCO2 and pH values are usually reasonably accurate.
Do not put monitor with a hot wire stylus inside the pressure chamber.
Make sure all devices attached to patient’s body are hyperbaric chamber compatible. If it is not sure, not to bring them into chamber.

88. 16. Injections
Avoid Intramuscular/subcutaneous because of delayed/erratic absorption (due to vasoconstriction secondary to HBO).
Be careful with multiple use vial during ascent.
17. Defibrillation
Defibrillation should only be done when the patient was surfaced because of fire hazard.
18. Suction devices
Suction device is available inside and outside the chamber.
19. Indwelling urinary catheter
Ensure that balloon is inflated with water.

89. 20.Sphygmomanometer
Do not use mercury-filled type.
21.Staff accompanying patient should not carry combustible materials include
Cigarettes, matches or lighters
Oil based cosmetic, face creams, body oils, hair spray, nail polish.
Nylon clothing
Ink filling pen
Electronic instrument
Pagers, mobile phone, watches (except diving-watch)

90. Most commonly involve ear on descent
22. Complication anticipated during treatment
- Barotrauma:
Most commonly involve ear on descent
May involve sinuses, lungs, carious teeth
- O2 toxicity
Acute toxicity usually manifests as seizure.
- Claustrophobia
- Reversible worsening of visual acuity.
- Transient GI pain
- Fire / explosion hazards
1st issued June, 1998
Revised in Jul 1998
Revised in Aug 1998
Revised in Feb 2001
Revised in Aug 2001

91. Occupational Safety and Health for Staff
Training and instructions/guidelines provided
Safety measures especially fire hazards (refer to guidelines provided by FSD)

92. Occupational Safety and Health for Staff
Normal Eustachian Tube function
No history of pneumothorax
No history of obstructive or restrictive airway diseases, no history of chest surgery
Not pregnant
No recent diving

93. Occupational Safety and Health for Staff
No flying after dive – at least 24 hours
Diving with decompression stops – at least 48 hours
Recognise symptoms of complications of compressed air work and seek treatment
Barotrauma especially ears
Decompression illness e.g. joint pain, numbness, weakness etc.
Informed OMD through emergency call number if DCI suspected
Notify occupational diseases to OMD

94. Comments and Questions