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Hyperbaric Oxygen Therapy
Yan Wing Wa Intensive Care Unit Pamela Youde Nethersole Eastern Hospital 6 June 2005
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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
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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
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Absolute pressure (Pabs)
Atmospheric pressure + Gauge pressure / Water pressure e.g. sea surface = 1 ATA 10 msw = 2 ATA 18 msw = 2.8 ATA
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Pascal’s principle A pressure applied to a liquid will be transmitted “equally” throughout the liquid.
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Ideal Gas Law P1 x V1 = P2 x V2 T1 T2 P x V = N x R x T
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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
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Charles’ Law P P1 P2 = constant; = T T1 T2 P P2 = T T2
Vs: Adiabatic heating (Second Law of Thermodynamics)
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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
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Respiratory Gases Pabs – VSTPD = VBTPS x ( ) x
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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
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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
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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
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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
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Gas Flux = gases diffusion x Q LaPlace’s Law P = 2 x / r
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The Mechanism of Barotrauma
Barotrauma of Descent Middle ear Pulmonary Sinus Barotrauma of Ascent
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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
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Cardiovascular System
Changes in blood volume distribution Dive reflex: heart rate Blood pressure : same
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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)
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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
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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
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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)
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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
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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
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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
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Oxygen Toxicity fever work CO2 retention steroid anxious
adrenaline /noradrenaline high dose penicillin insulin infusion thyrotoxicosis
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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
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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
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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
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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!
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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
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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
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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
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Control Panel with Fireman
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Control Panel
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Control Panel
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Control Panel
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Entrance to Chamber
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Emergency Trolley
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Medical equipments and consumables
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Communication Lock
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Drinking Water and Washing Basin
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Communication with outside
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Communication with outside
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Communication with Entry Lock
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Entry Lock with Sanitary Facilities
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Entry Lock
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Exit From Entry Lock
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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
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Royal Adelaide Hospital
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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
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Monoplace chambers
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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.
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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
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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.
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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
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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.
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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.
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Ventilator
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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
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Oxygen Mask
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Oxygen Mask
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Hood for HBO
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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.
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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.
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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.
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Hyperbaric Chamber
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Chamber and Monitoring Equipment
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For Monitoring Equipment
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Medical Examination Equipment
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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.
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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.
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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)
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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
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Occupational Safety and Health for Staff
Training and instructions/guidelines provided Safety measures especially fire hazards (refer to guidelines provided by FSD)
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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
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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
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