Treatment of Decompression Illness

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Treatment of Decompression Illness
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Evidence for Efficacy of Recompression

• considerable collective experience
• repeated personal observations consistent with
  beneficial effect
• case reports / series etc
• consensus opinion of experts
• no double blind RCTs
• acceptance as the definitive treatment of DCI is
  such that patients would be reluctant to be
  controls and doctors would be reluctant to omit
  recompression in the majority of cases

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Initial Objectives of treatment

• pressure
• reduces volume of gas bubbles
• bubble crushing relieves mechanical effects
• enhances gas diffusion out
• increase in bubble surface area to volume ratio
• increased pressure in bubble

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Use of Oxygen

• With changes in diving practice failure rates for
  serious case with USN tables 1-4 reached 46
• 1937 Behnke Shaw experimented with oxygen at
  2.8 ATA after a brief period at 6 ATA on air
• excellent results
• take advantage of wide open oxygen window
• reduces white cell adhesion
• USN unhappy to use oxygen
• However beware the box!

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USN 6A

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Use of Oxygen

• 1964 Goodman Workman used oxygen once in a
  pressure range 2-2.8 ATA
• Identified a Minimally Adequate Recompression
  Table
• 30 mins at 2.8 ATA, ascent over 90 mins, all on
  oxygen
• failure rate 3.6 despite cases of similar
  severity

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Use of Mixtures Including Oxy-Helium

• still doctors liked to use 50 msw
• 1970s Comex introduced a 30 msw table with 50
  nitrox to minimise gas load but allow 4 ATA
• 50 nitrox also used by some at 50 msw
• 1958 20 heliox allowed by USN as an alternative
  to air
• 6ATA without increasing nitrogen load
• nitrogen elimination gradient maximised
• narcosis not a problem
• heliox mixtures used for a variety of tables
• 50 for RNTT67, RNs version of Comex 30

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The Comex 30 table
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Hawaiian Tables
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Objectives of treatment

• high partial pressure of oxygen
• aids elimination of inert gas
• gradient
• oxygen window
• reverses tissue hypoxia
• reduces white cell adhesion to endothelium
• allows re-establishment of circulation

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RECOMPRESSION

• Therapeutic tables utilised vary depending upon
  requirements
• But do we really understand what we are doing?

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Denial

• real problem
• adhered to table
• never had a problem on same profile before
• cant happen to me
• attributed to other things
• motion sickness
• hangover
• bad prawn curry
• fear of consequences on diving / job etc
• particular problem with Technical divers
• self treatment

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Recovery Procedures

• if incapacitated diver should be recovered from
  the water
• protect airway
• do not delay moving diver to a place of safety
  unless it is a long way
• standby diver
• with or without breathing apparatus

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First Aid

• ABC
• Oxygen
• Improves cerebral functioning
• Decreases severity of bends
• Can mask DCI
• ? cure DCI
• Fluids

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Communications

• notify personnel in charge of diving operation
• activities / machinery might need to be stopped
  for safety of casualty / other personnel
• notify emergency services / on site medical team
  if appropriate
• contact hyperbaric facility for advice and to
  ensure ready to receive casualty
• establish how casualty will be transported
• and who is to arrange this

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Transporting the Patient with DCI

• ideally the patient should be transported at no
  less than 1 ATA
• choose fastest and most appropriate transport
• if flown then keep altitude below 300m and
  patient should breathe 100 O2
• helicopter fast in flight but has limitations
• refuel points
• landing points
• prep time
• night flying
• weather / wind
• winching time

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Diagnosis of DCI

• HISTORY
• gas load / reduction in ambient pressure
• Include
• dive profile
• rate of ascent
• symptom onset time
• changes in symptom type or intensity
• More Likely
• missed deco stops
• heavy exertion during dive
• rapid ascent
• previous Hx of DCI

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Role and Timing of the Clinical Examination

• clinical examination guides treatment decisions
• should not delay treatment unnecessarily
• discontinue assessment as soon as established
  that patient requires urgent recompression and is
  safe for compression
• thorough examination pre-treatment
• sometimes required in subtle cases
• appropriate in static, mild cases with long delay
  between onset and presentation
• will give best baseline assessment on which to
  gauge effectiveness of treatment

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Role and Timing of the Clinical Examination

• completion of examination on compression or at
  treatment depth
• ongoing assessment required by attendant or
  doctor inside chamber
• detailed post-treatment examination

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Delay to Recompression

• intuitively earlier -gt better outcome
• naval experience with on-site chambers is
  supportive
• best evidence to date is that severity at time of
  recompression is best indicator of outcome
• very few cases seen early enough to make a
  difference?
• skew in presentation
• serious early
• mild delayed
• clearly this makes a progressive case most urgent

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IV Fluids and Drugs

• Fluids
• crystalloid for rehydration
• colloid for intravascular volume
• no glucose if neurological insult
• Steroids
• ECHM consensus should not be used
• Lidocaine
• some evidence of usefulness in AGE
• ECHM consensus optional for other neuro DCI
• Antiplatelet Drugs
• ECHM consensus aspirin NSAIDs optional
• ECHM strongly recommends anticoagulants for DVT
  prophylaxis

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• Undersea Hyperb Med. 2003 Fall30(3)195-205.
• Adjunctive treatment of decompression illness
  with a non-steroidal anti-inflammatory drug
  (tenoxicam) reduces compression
  requirement.Bennett M, Mitchell S, Dominguez
  A.Department of Diving and Hyperbaric Medicine,
  Prince of Wales Hospital, and University of NSW,
  Sydney, Australia.180 subjects were graded for
  severity on admission and randomized according to
  a stratified random number schedule. Subjects
  were recompressed and treatment continued daily
  until symptom stabilization or complete
  resolution. Tenoxicam 20 mg or a placebo
  preparation was administered at the first air
  break during the initial recompression and
  continued daily for seven days. The subjects were
  assessed using a recovery status score at the
  completion of treatment and at 4-6 weeks. The
  proportion of patients with mild residual
  symptoms at discharge and final follow-up was not
  significantly different (discharge placebo 30
  versus tenoxicam 37, P0.41 six weeks placebo
  20 versus tenoxicam 17, P0.58). There was a
  significant reduction in the number of treatments
  required to achieve discharge (median treatments
  placebo 3, tenoxicam 2, P0.01). 61 of patients
  in the tenoxicam group required less than 3
  compressions, versus 40 in the placebo group
  (P0.01, RRR 33 95CI 9-56, NNT5 95CI
  3-18). There was no evidence of increased
  complications of treatment in the tenoxicam
  group. When given this NSAID, patients with DCI
  require fewer hyperbaric oxygen (HBO2) sessions
  to achieve a standard clinical end-point and
  there is likely to be an associated cost saving.

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Monoplace
UK Category 4
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Duoplace Chamber
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Multiplace
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Gas Supplies and Gas Storage
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Use of Algorithms

• standardises approach
• ensures correct gases and capabilities available
• facilitates collection of statistics of success
• allows expert opinion to guide less experienced

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Treatments for Residua

• residua are treated with repeat hyperbaric
  treatments
• typically 12-14 msw for 90 minutes
• reduced pO2 to reduce side-effects
• seems to be as effective
• bubble crushing not required at this stage

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General Advice

• treat promptly, do not delay
• follow treatment table accurately
• do not ignore minor symptoms, they can quickly
  become serious
• after treatment, keep in the vicinity for 24
  hours re-assess

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Some complex issues
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Amazon Abyss
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Amazon Abyss
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The Hyperlite
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The new Bonner Lab