Diving Medicine: An Overview
MAJ James Lynch, MD, MS
U.S. Army Diving Medical Officer
• Barotrauma
• Decompression
Sickness
• Flying After Diving
• Rebreathers
Agenda
• Eustachian Tube
– Connects middle ear with nasopharynx
– Allows equalization of middle ear with ambient
pressure
– Will ...
• Four major sinus groups
– Maxillary
– Frontal
– Sphenoid (pain in occipital region)
– Ethmoid air cells
• Function
– Lig...
Boyle’s Law:
At constant Temperature, Volume
varies inversely proportional to
Pressure
Barotrauma
• Elements needed to produce barotrauma
– Membrane (vascular) lined space
– Ambient pressure change
– Rigid walls
– Gas fi...
• Predisposing
factors
– Wax impaction
– Tight wet suit
hood
– Ear plugs
– Otitis externa
Barotrauma – External
• Signs and Symptoms
– Ear pain on descent
– Hearing loss until pressure is equalized
– Hemorrhage in external canal
• Tre...
• Most common type of pressure-related
injury
• More common in inexperienced divers
– Ineffective valsalva
• Etiology is a...
• Pathogenesis
– Relative vacuum forms in middle ear resulting in
capillary leakage.
– TM rupture will occur between 100-5...
• Treatment
– Restrict diving until resolved
– Mild (0-1) 8 to 72 hours
– Moderate (2-3) 1 to 8 days
– Severe (4-5) may ta...
• Treatment (continued)
- Decongestants
- Intranasal steroid
- Systemic Steroids – if mod-severe (1mg/kg x 5
days + taper)...
• Prevention
– Avoid diving with Eustachian Tube
Dysfunction
– Topical and systemic decongestants
– Stay ahead of pressure...
• May result in permanent damage to cochlea
or vestibular system
• Occurs most commonly on descent
– Generally starts as m...
• Sites of injury
– Oval window
– Round window
Barotrauma - Inner
} Results in perilymph fistula
• Signs and symptoms
– Vertigo (persistent)
– Tinnitus (often described as “roaring”)
– Nystagmus with positional testing
...
• Treatment
– R/O AGE and DCS (covered later)
– Strict bed rest
– Avoid straining
– Consider sedation
– ENT referral, earl...
• Caloric Vertigo
– Transient; common on descent (thermocline)
– Caused by differing water temperatures in
external canals...
• Predisposing factors
– Infection or Allergy
– Anatomic variations
• Signs and Symptoms
– Pain in sinus area
– Dental pai...
• Treatment
– No diving
– Decongestants
– Observe for infection
– May require surgical correction
• Anatomical defects
• P...
• Barodontalgia
– Occurs on ascent or descent
– Predisposing factors
• Dental disease
• Failed dental restorations
• Recen...
• Signs and Symptoms
– Tooth pain
– Maxillary sinus pain
– Exploding or imploding tooth
• Treatment
– Pain relief
– Dental...
• Predisposing factors
– Failure to clear mask on descent
– Diving with goggles
• Signs and Symptoms
– Periorbital pain
– ...
• Pulmonary Over-inflation Syndrome (POIS)
• Expansion of gas trapped in lung during ascent
(decreasing ambient pressure) ...
Air trapped in lung due to:
• Airway obstruction as in asthma
• Thick secretions
• Lung granulomas (sarcoidosis)
• Cysts a...
Clinical presentation
• Initial rupture of lung tissue with release of gas
• Gas may remain in lung tissue
- migrate to pu...
Pulmonary Barotrauma
Conditions resulting from POIS
• Arterial gas embolism
• Pneumothorax
• Mediastinal emphysema
• Subcu...
Pulmonary Barotrauma
Surface
3 FSW
96 FSW
99 FSW
Arterial Gas Embolism
• Alveolar rupture with concomitant venous or
capillary rupture
• Air traverses pulmonary vein to le...
Arterial Gas Embolism (AGE)
Arterial Gas Embolism
• CNS and Heart most susceptible to injury
• CVA sxs commonly caused by emboli to brain
• Emboli to ...
AGE – Presenting Signs and Symptoms
• Stupor or confusion
• Coma with or without seizures
• Unilateral motor deficits
• Vi...
AGE – Treatment
• A, B, C’s ; check vital signs
• Keep patient warm
• Neutral position, not Trendelenberg
• 100% O2 by fac...
Pneumothorax - Simple
Symptoms
• Chest pain (lateral or apical)
• Cough
• Shortness of breath
Signs
• Decreased breath sou...
Simple Pneumothorax
Pneumothorax – Simple
Treatment
• Needle thoracostomy, Chest tube
• Observe if pneumo is small
Resumption of diving
• Spon...
Pneumothorax - Tension
Symptoms
• Chest pain and cough
• Increasing SOB and tachypnea
Signs
• Asymmetric chest wall moveme...
Tension Pneumothorax
Pneumothorax - Tension
Treatment
• Immediate needle decompression
• Chest tube
Pulmonary Barotrauma
Mediastinal Emphysema
Symptoms
• Substernal chest pain or burning
• May be worsened by inspiration
• Intensity of pain may...
Mediastinal Emphysema
Subcutaneous Emphysema
Symptoms
• Substernal chest pain or burning
• May be worsened by inspiration
• Feeling of “Rice Kri...
Subcutaneous Emphysema
Mediastinal or Subcutaneous Emphysema
Treatment
• Surface O2
• For cardiac or respiratory compromise
consider recompressio...
POIS other than AGE –Treatment
• Casualty with SOB, substernal chest pain, voice
change, but stable.
• Signs of subcutaneo...
Decompression Sickness
Definition
Pathologic response to the formation of
bubbles from gas dissolved in tissue due to
a reduction in ambient pres...
• Robert Boyle, 1670
– Decompressed a snake and noted visible bubble
formation in its eye vitreous—and that the
snake was ...
Visible Bubbles in Tissue
Decompression Sickness
Further experiences with Caisson’s
Disease
• Construction of Eads Bridge,
St. Louis, 1860s
• Construction of Brooklyn
Brid...
Paul Bert, French physiologist
• 1878, publishes Barometric Pressure
• States bubbles cause decompression sickness
• Bubbl...
J.S. Haldane, British physiologist
• Developed the first
comprehensive decompression
theory and applied it for the
Royal N...
• On the surface, our tissues are in
equilibrium (balance) with the inert (non-
metabolic, e.g. nitrogen) gases in our
bre...
“The amount of gas that will dissolve in a
liquid is proportional to the partial pressure
of that gas above the liquid”
• ...
• Thus at depth, more inert gas than usual is
pushed into our tissues.
• If we come up too quickly, then we may
exceed the...
On ascent, the external (surrounding, ambient)
pressure reduces, so . . .
• The partial pressure of inert gas in our
breat...
• Bubble formation (to the best of current
knowledge) is the root cause of
decompression sickness.
• By following ascent (...
• Everywhere the bubble bounces causes
damage on walls of vasculature
• Eventually it becomes stuck and causes
more damage...
• Bubble size reduced IAW Boyles Law
– If the pressure of the gas in the bubble is > than
the surrounding pressures the bu...
Hydrostatic Reduction
• During the ascent or decompression phase
of a dive, inert gas, which has been
dissolved under depth pressure into tissue...
• Not felt to be a major factor in the
pathogenesis of DCS
• Autochthonous (formed or originating in the
place where found...
• Arterial, venous, capillary, lymphatic
• Most of the evidence for the in vivo
presence of intravascular bubbles is based...
The pulmonary tissue bed usually is efficient
in filtering bubbles, but the following may
compromise it:
• Pulmonary impai...
• Prevalence of patent foramen ovale (PFO) in
the general population is as high as 30%
• 1998 meta-analysis shows OR = 2.5...
• Embolization and blocked blood flow
• Compression or distortion of tissue and
vessels
• A bubble acts as a foreign body ...
• Release of histamine and similar mediators
• Inflammatory vasoactive plasma polypeptides
such as Kinin
• Many effects
--...
DCS – Presenting Signs and Symptoms
• Numbness or Pain
• Dizziness
• Fatigue or weakness
• Headache
• Nausea
• Gait and Se...
• Develops within minutes after deep, brief dives;
but may develop over hours to days after long,
shallow dives
• CNS DCS ...
Time of onset of initial symptoms in 591
DCS cases from 1999 Divers Alert
Network (DAN) data
Time of Onset %
Upon surfacin...
• Musculoskeletal joint pain
• Skin itching and marbling
• Lymphatic edema and tender
lymph nodes
Type I DCS
Musculoskeletal DCS
• If isolated, also known as “pain only” DCS
• Typically joint pain, usually outside the area
covered ...
Cause of musculoskeletal pain is unknown
• Bubble formation in joint space?
– Bubbles artificially introduced don’t seem t...
Minor musculoskeletal pain,“Niggles”
• Refers to “odd fleeting aches and pains”
• May herald typical limb pain DCS
• Some ...
Skin DCS
• Itching and mild urticaria--no Tx needed
• Cutis Marmorata—more serious
– Deep red or purple marbling or mottli...
Lymphatic bends
• Usually presents as local edema with or without pain,
can involve nodes and wider lymphatic obstruction
...
• Pulmonary (“chokes”)
• Neurologic
• Vestibular (Inner Ear)
Type II DCS
Navy diver in MK21 hard hat rig
Pulmonary DCS
• 2% of DCS cases
• Overwhelming load of venous, inert, gas bubbles in the
pulmonary circulation
• Animal st...
Common scenarios for Pulmonary DCS
• Emergency ascents from long, deep dives
with large, omitted decompression
• Altitude ...
Signs and symptoms of Pulmonary DCS
• Substernal discomfort
• Cough
• Pain with inspiration or expiration
• May progress r...
Neurologic DCS
• More common in recreational diving (up to
80% of reported cases to the Divers Alert
Network)
• In contras...
Neurologic DCS
• Spinal cord most affected (40-60% of cases),
then brain, then peripheral nerves
• Distinction of cord v. ...
Manifestations of Spinal cord DCS
• Signs usually are multi-focal, not conforming
to a cord syndrome
• May have extremity ...
Manifestations of Cerebral DCS
• Motor deficits including hemiplegia
• Sensory changes
• Mental status changes
• Loss of c...
Inner Ear DCS, “Staggers”
• Mainly in heliox and saturation dives
• Possible role of isobaric counter-diffusion
--With He ...
Signs and Symptoms of Inner Ear DCS
• Severe vertigo
• Severe nausea and vomiting
• Nystagmus
• Tinnitus
• Hearing loss
Ty...
Differentiating inner ear DCS from barotrauma
• Dive depth and time profile--shallow, no-D
dives are unlikely to result in...
Ocular manifestations
• Nystagmus
• Diplopia
• Visual field defects and scotomata
• Homonymous hemianopsia
• Central retin...
• Proposed term including all cases of reduced-
pressure, bubble-related disorders, including AGE
because distinguishing b...
• DCS/AGE: symptoms of confusion,
drowsiness, fatigue, indifference.
• AGE attacks brain directly & immediately.
• Manifes...
Localized pain 858 91.8 744 76.6
Numbness or paresthesia 199 21.2 41 4.3
Muscular weakness 193 20.6 8 0.8
Skin rash 140 14...
Type Manifestation % Cases
Neurological 47
Pain 25
Constitutional 18
Skin 3
Cardiopulmonary 1.5
Lymphatic 0.4
DAN Survey D...
• If you don’t think of it,
you won’t ask about
recent diving
• The key is the clinical,
“bedside,” diagnosis of
DCS
• His...
• Short, deep dives—a large pressure change that
happens quickly
• Omitted decompression
• Patent foramen ovale
• Cold con...
• The sooner the treatment initiated, the better the
outcome
• Cases of improvement have occurred even after
about a week ...
• 3 Categories Of Urgency
– Emergent: neurologic signs are present and obvious
even without an examination
• “feet should ...
Treatment Table 6 (TT6)
0
30
60
30
Total Elapsed Time: 4 hrs 45 minutes (not including descent time)
O2
O2 O2 O2
O2
20 20 ...
• Indications
– Type II symptoms
– Type I symptoms not relieved in 10 minutes
– Cutis marmorata
– Asymptomatic omitted dec...
• Considerations
– Can be extended twice at 60 ft (20-5 cycle) and twice at
30 ft (60-15 cycle) (don’t extend for mild joi...
• Surface O2 at 15 liters/min for up to 12 hours
• IV normal saline or lactated Ringer’s, goal of clear
urine output (BUT,...
• 100 % O2 breathing should be initiated during
transport to the recompression site
• Potential benefits of O2
(1) Enhance...
• Dehydration decreases tissue oxygenation and off-
gassing.
• Immersion diuresis, insensible water loss
(breathing a dry ...
• Two options:
– Transport to nearest chamber vs. in-water
recompression
• Transport (preferred)
– position prone or left ...
• Climbing to altitude is like ascending to the
surface and can bring on DCS
• If air transport is necessary, the cabin sh...
Flying After Diving
Diver’s Alert Network (DAN)
2002 Consensus Guidelines for
Flying After Recreational Diving
Applies to ...
• For a single no-decompression dive:
– Wait at least 12 hours before flying
• For multiple dives/day or multiple days of ...
• Weight: 25 pounds
• Chest mounted
• Oxygen bottle volume:
1.5 liters
• Oxygen bottle working
pressure: 200 BARS
• Canist...
Rebreathers
• Decompression sickness
• Nitrogen narcosis
• Hypoxia
• Oxygen toxicity
• CO2 toxicity
• Caustic cocktail
• Draeger Ear
M...
• Caused by canister leak
• Highly alkaline solution
– Sofnolime (a typical CO2 scrubber material)
• >75% Calcium hydroxid...
• Also known as “Draeger Ear”
• Refers to the negative pressure that develops in
middle ear after long O2 dives.
• Sxs: ea...
• Analgesics
• NSAIDS
• Decongestants
• Antibiotics
• Topicals
• Antacids
• Vitamins
Considered Safe in
Diving
Questions?
Hang Loose!
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
Diving Med Overview - No Slide Title
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  • Doctor Lynch, this is a very good overview of Diving Medicine. Bravo Zulu. I am a retired US Navy EOD Diving officer. This presentation offers clear and concise information logically explained.
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  1. 1. Diving Medicine: An Overview MAJ James Lynch, MD, MS U.S. Army Diving Medical Officer
  2. 2. • Barotrauma • Decompression Sickness • Flying After Diving • Rebreathers Agenda
  3. 3. • Eustachian Tube – Connects middle ear with nasopharynx – Allows equalization of middle ear with ambient pressure – Will “lock” closed with excessive pressure in nasopharnyx – Most divers have to actively equalize on descent – Equalization will occur passively on ascent Barotrauma - Anatomy
  4. 4. • Four major sinus groups – Maxillary – Frontal – Sphenoid (pain in occipital region) – Ethmoid air cells • Function – Lighten skull – Provide mucous for nasal cavity Barotrauma - Anatomy
  5. 5. Boyle’s Law: At constant Temperature, Volume varies inversely proportional to Pressure Barotrauma
  6. 6. • Elements needed to produce barotrauma – Membrane (vascular) lined space – Ambient pressure change – Rigid walls – Gas filled space – Enclosed space Barotrauma If rigid gas filled spaces are properly vented, barotrauma will not occur
  7. 7. • Predisposing factors – Wax impaction – Tight wet suit hood – Ear plugs – Otitis externa Barotrauma – External
  8. 8. • Signs and Symptoms – Ear pain on descent – Hearing loss until pressure is equalized – Hemorrhage in external canal • Treatment – Stop descent – Relieve obstruction – Treat OE if present Barotrauma - External
  9. 9. • Most common type of pressure-related injury • More common in inexperienced divers – Ineffective valsalva • Etiology is a blocked Eustachian Tube – Upper respiratory infection – Large adenoid tonsils, nasal septal deviation Barotrauma - Middle
  10. 10. • Pathogenesis – Relative vacuum forms in middle ear resulting in capillary leakage. – TM rupture will occur between 100-500 mmHg of differential pressure • Signs and symptoms – Fullness or pain – Mild transient conductive hearing loss – TM perforation in severe cases – May have blood in face mask – Transient vertigo and/or tinnitus Barotrauma - Middle
  11. 11. • Treatment – Restrict diving until resolved – Mild (0-1) 8 to 72 hours – Moderate (2-3) 1 to 8 days – Severe (4-5) may take up to six weeks (for perforations) Barotrauma - Middle Recurrent perforation is common if diving is resumed too soon after severe ear squeeze
  12. 12. • Treatment (continued) - Decongestants - Intranasal steroid - Systemic Steroids – if mod-severe (1mg/kg x 5 days + taper) – Antibiotics if perforated – Avoid topicals if perforated unless recommended by ENT (use otic suspension not solution) Barotrauma - Middle
  13. 13. • Prevention – Avoid diving with Eustachian Tube Dysfunction – Topical and systemic decongestants – Stay ahead of pressure changes Barotrauma - Middle
  14. 14. • May result in permanent damage to cochlea or vestibular system • Occurs most commonly on descent – Generally starts as middle ear squeeze – Forceful Valsalva causes injury to inner ear • Can be caused by implosion or explosion Barotrauma - Inner
  15. 15. • Sites of injury – Oval window – Round window Barotrauma - Inner } Results in perilymph fistula
  16. 16. • Signs and symptoms – Vertigo (persistent) – Tinnitus (often described as “roaring”) – Nystagmus with positional testing – Bubbling sensation in ear – Neurosensory hearing loss – Otoscopic findings of middle ear barotrauma Barotrauma - Inner
  17. 17. • Treatment – R/O AGE and DCS (covered later) – Strict bed rest – Avoid straining – Consider sedation – ENT referral, early in course if possible – Surgical exploration is often needed Barotrauma - Inner
  18. 18. • Caloric Vertigo – Transient; common on descent (thermocline) – Caused by differing water temperatures in external canals or TM rupture allowing water to enter middle ear • Alternobaric Vertigo – Transient; common on ascent – Caused by rapid pressure change transmitted into inner ear Barotrauma – Inner DDX
  19. 19. • Predisposing factors – Infection or Allergy – Anatomic variations • Signs and Symptoms – Pain in sinus area – Dental pain with maxillary sinus involvement – Blood in face mask – Tenderness on sinus percussion Barotrauma - Sinus
  20. 20. • Treatment – No diving – Decongestants – Observe for infection – May require surgical correction • Anatomical defects • Polyps • Mucus retention cysts Barotrauma - Sinus
  21. 21. • Barodontalgia – Occurs on ascent or descent – Predisposing factors • Dental disease • Failed dental restorations • Recent dental work Barotrauma - Teeth
  22. 22. • Signs and Symptoms – Tooth pain – Maxillary sinus pain – Exploding or imploding tooth • Treatment – Pain relief – Dental referral Barotrauma - Teeth
  23. 23. • Predisposing factors – Failure to clear mask on descent – Diving with goggles • Signs and Symptoms – Periorbital pain – Periorbital petechiae and swelling • Treatment - observe Barotrauma - Face mask
  24. 24. • Pulmonary Over-inflation Syndrome (POIS) • Expansion of gas trapped in lung during ascent (decreasing ambient pressure) with rupture of lung tissue • Causes: – Breath-holding during ascent – Inhaling while pushing purge button – Rapid uncontrolled ascent (blow-up) – Air trapped in lung Pulmonary Barotrauma
  25. 25. Air trapped in lung due to: • Airway obstruction as in asthma • Thick secretions • Lung granulomas (sarcoidosis) • Cysts and blebs • spontaneous pneumothorax Pulmonary Barotrauma
  26. 26. Clinical presentation • Initial rupture of lung tissue with release of gas • Gas may remain in lung tissue - migrate to pulmonary circulation - move to the pleural space - dissect along the bronchial tree into the mediastinum and subcutaneous tissues Pulmonary Barotrauma
  27. 27. Pulmonary Barotrauma Conditions resulting from POIS • Arterial gas embolism • Pneumothorax • Mediastinal emphysema • Subcutaneous emphysema • Pneumopericardium
  28. 28. Pulmonary Barotrauma Surface 3 FSW 96 FSW 99 FSW
  29. 29. Arterial Gas Embolism • Alveolar rupture with concomitant venous or capillary rupture • Air traverses pulmonary vein to left heart • Emboli are pumped out to the systemic circulation and distributed to all organs Pulmonary Barotrauma
  30. 30. Arterial Gas Embolism (AGE)
  31. 31. Arterial Gas Embolism • CNS and Heart most susceptible to injury • CVA sxs commonly caused by emboli to brain • Emboli to coronary arteries may cause myocardial ischemia or infarction • Usually present within the first ten minutes of a surface interval Pulmonary Barotrauma
  32. 32. AGE – Presenting Signs and Symptoms • Stupor or confusion • Coma with or without seizures • Unilateral motor deficits • Visual disturbances • Vertigo • Sensory abnormalities Pulmonary Barotrauma
  33. 33. AGE – Treatment • A, B, C’s ; check vital signs • Keep patient warm • Neutral position, not Trendelenberg • 100% O2 by facemask or ET tube • IV Fluids • Serial Neurological exams • Immediate recompression upon diagnosis • Cabin pressure below 1000 feet Pulmonary Barotrauma
  34. 34. Pneumothorax - Simple Symptoms • Chest pain (lateral or apical) • Cough • Shortness of breath Signs • Decreased breath sounds • Typical CXR findings Pulmonary Barotrauma
  35. 35. Simple Pneumothorax
  36. 36. Pneumothorax – Simple Treatment • Needle thoracostomy, Chest tube • Observe if pneumo is small Resumption of diving • Spontaneous - unsafe for diving • Traumatic - may return to diving after resolution with proper evaluation Pulmonary Barotrauma
  37. 37. Pneumothorax - Tension Symptoms • Chest pain and cough • Increasing SOB and tachypnea Signs • Asymmetric chest wall movement • Tracheal deviation • JVD • Rapid pulse with decreasing pulse pressure • Mediastinal shift on CXR Pulmonary Barotrauma
  38. 38. Tension Pneumothorax
  39. 39. Pneumothorax - Tension Treatment • Immediate needle decompression • Chest tube Pulmonary Barotrauma
  40. 40. Mediastinal Emphysema Symptoms • Substernal chest pain or burning • May be worsened by inspiration • Intensity of pain may vary greatly Signs • Mediastinal air on CXR • May hear crepitus - Hamman’s sign Pulmonary Barotrauma
  41. 41. Mediastinal Emphysema
  42. 42. Subcutaneous Emphysema Symptoms • Substernal chest pain or burning • May be worsened by inspiration • Feeling of “Rice Krispies” under skin • Subjective voice changes Signs • Crepitus in neck and supraclavicular area • Audible voice changes Pulmonary Barotrauma
  43. 43. Subcutaneous Emphysema
  44. 44. Mediastinal or Subcutaneous Emphysema Treatment • Surface O2 • For cardiac or respiratory compromise consider recompression • 5 - 10 FSW may be sufficient Pulmonary Barotrauma
  45. 45. POIS other than AGE –Treatment • Casualty with SOB, substernal chest pain, voice change, but stable. • Signs of subcutaneous emphysema (“rice krispies”) • Tx with 100% O2 on surface at least for 1 hour. • May obtain CXR / CT chest for confirmation / documentation Pulmonary Barotrauma
  46. 46. Decompression Sickness
  47. 47. Definition Pathologic response to the formation of bubbles from gas dissolved in tissue due to a reduction in ambient pressure. Synonyms: DCS, Decompression Illness (DCI), dysbarism, bends, Caisson’s disease Decompression Sickness
  48. 48. • Robert Boyle, 1670 – Decompressed a snake and noted visible bubble formation in its eye vitreous—and that the snake was “tortured furiously.” • Triger, 1841 – French mining engineer first described pressure-related limb pain and paralysis in 2 caisson workers—after a 7-hour dive in the Loire river. History
  49. 49. Visible Bubbles in Tissue Decompression Sickness
  50. 50. Further experiences with Caisson’s Disease • Construction of Eads Bridge, St. Louis, 1860s • Construction of Brooklyn Bridge, NY, 1869-1883, 20 deaths • Popularization of name, “bends”, because of the bent posture of some patients. History
  51. 51. Paul Bert, French physiologist • 1878, publishes Barometric Pressure • States bubbles cause decompression sickness • Bubbles are composed primarily of N2 • Was the first to suggest recompression for DCS • Was first to suggest a slow decrease in pressure to avoid DCS • Was first to suggest decompression with O2 History
  52. 52. J.S. Haldane, British physiologist • Developed the first comprehensive decompression theory and applied it for the Royal Navy, 1905-7. • His ideas still are utilized today (such as the initial formulation of the US Navy standard air decompression tables). Haldanian Decompression Theory
  53. 53. • On the surface, our tissues are in equilibrium (balance) with the inert (non- metabolic, e.g. nitrogen) gases in our breathing mixture – Air is 78% N2, 21% O2 , and 1% Argon • When we dive with this same breathing mix, what happens to the concentration of the inert gas in the mix???? Why Decompression?
  54. 54. “The amount of gas that will dissolve in a liquid is proportional to the partial pressure of that gas above the liquid” • What happens to the partial pressure of the inert gas in our breathing mix when we dive? • What does this do to the amount of inert gas dissolved in our tissues? By the second Law of Thermodynamics, tissues will equilibrate with the respired gas. Henry’s Law
  55. 55. • Thus at depth, more inert gas than usual is pushed into our tissues. • If we come up too quickly, then we may exceed the capacity for dissolved inert gas in our tissues, and the excess gas has no where else to go except to form… BUBBLES! Decompression
  56. 56. On ascent, the external (surrounding, ambient) pressure reduces, so . . . • The partial pressure of inert gas in our breathing mix decreases • Correspondingly, per Henry’s Law, the amount of inert gas that can be dissolved in our tissues will be reduced • What happens to this excess dissolved gas when ascend? Decompression
  57. 57. • Bubble formation (to the best of current knowledge) is the root cause of decompression sickness. • By following ascent (or decompression) rules, such as slowing the rate of ascent, we can prevent significant bubble formation and reduce the risk of decompression sickness. Decompression
  58. 58. • Everywhere the bubble bounces causes damage on walls of vasculature • Eventually it becomes stuck and causes more damage and pain • It damages capillaries and causes tissue hypoxia and injury Bubble Damage
  59. 59. • Bubble size reduced IAW Boyles Law – If the pressure of the gas in the bubble is > than the surrounding pressures the bubble grows. – If it is < than the surrounding pressures the bubble will shrink. Recompression
  60. 60. Hydrostatic Reduction
  61. 61. • During the ascent or decompression phase of a dive, inert gas, which has been dissolved under depth pressure into tissues, comes out of solution under lower pressure. • This process can lead to inert gas in tissue becoming supersaturated, resulting in bubble formation. Pathophysiology of DCS
  62. 62. • Not felt to be a major factor in the pathogenesis of DCS • Autochthonous (formed or originating in the place where found, not carried there from somewhere else) bubble formation in CNS white matter: is this an example of extravascular bubbles? --we’re not sure. Extravascular Bubbles
  63. 63. • Arterial, venous, capillary, lymphatic • Most of the evidence for the in vivo presence of intravascular bubbles is based upon doppler ultrasound studies • Usually observed on the venous side • Arterial bubbles rarely observed – However, if present, is associated with serious DCS Intravascular Bubbles
  64. 64. The pulmonary tissue bed usually is efficient in filtering bubbles, but the following may compromise it: • Pulmonary impairment (disease, barotrauma) • Arterio-venous shunts • Intracardiac shunts Arteriolization of venous bubbles
  65. 65. • Prevalence of patent foramen ovale (PFO) in the general population is as high as 30% • 1998 meta-analysis shows OR = 2.5 for DCS with PFO (3.4 cases in 10,000 dives) • 2003 Review of 145 articles shows no clear agreement to role of PFO in DCS • Extremely low absolute risk of DCS: <0.08% Intracardiac Shunts
  66. 66. • Embolization and blocked blood flow • Compression or distortion of tissue and vessels • A bubble acts as a foreign body provoking an inflammatory response – Aggregation of platelets and leukocytes – Activation of coagulation enzymes – Activation of the complement system Bubble Effects
  67. 67. • Release of histamine and similar mediators • Inflammatory vasoactive plasma polypeptides such as Kinin • Many effects --Vasodilation --Increased vascular permeability --Decreased perfusion --Increased pain via stimulation of nerve endings Bubble Effects (Secondary)
  68. 68. DCS – Presenting Signs and Symptoms • Numbness or Pain • Dizziness • Fatigue or weakness • Headache • Nausea • Gait and Sensory abnormalities • Visual disturbance • Itching Decompression Sickness
  69. 69. • Develops within minutes after deep, brief dives; but may develop over hours to days after long, shallow dives • CNS DCS may have shorter latency > 90% become symptomatic < 3 hours • Pain-only DCS may have a longer latency 90% become symptomatic < 6 hours • A few cases of DCS have been reported  36 hours after dive Latency of DCS
  70. 70. Time of onset of initial symptoms in 591 DCS cases from 1999 Divers Alert Network (DAN) data Time of Onset % Upon surfacing 30 < 1 hour 50 < 6 hours 67 < 24 hours 84 > 48 hours < 7%
  71. 71. • Musculoskeletal joint pain • Skin itching and marbling • Lymphatic edema and tender lymph nodes Type I DCS
  72. 72. Musculoskeletal DCS • If isolated, also known as “pain only” DCS • Typically joint pain, usually outside the area covered by shorts and a T-shirt • Peri-articular knees, shoulders, and elbows • No signs of inflammation • Usually dull, vague, deep, aching • Unaffected by movement Type I DCS
  73. 73. Cause of musculoskeletal pain is unknown • Bubble formation in joint space? – Bubbles artificially introduced don’t seem to cause pain • Bubbles in the bone marrow? – Bubble formation in marrow of sheep caused ↑ intra- medullary pressure and evidence of limb discomfort • Bubble formation under periosteum? • Autochthonous bubble formation in perarticular soft tissue (tendons, ligaments, joint capsule)? • Referred pain from central neurological injury? Type I DCS
  74. 74. Minor musculoskeletal pain,“Niggles” • Refers to “odd fleeting aches and pains” • May herald typical limb pain DCS • Some experts recommend treating as a form of Type I DCS Type I DCS
  75. 75. Skin DCS • Itching and mild urticaria--no Tx needed • Cutis Marmorata—more serious – Deep red or purple marbling or mottling – Blanches with pressure suggests vascular etiology – May be associated with itching – Tends to be associated with subsequent serious DCS, so some will treat as Type II DCS Type I DCS
  76. 76. Lymphatic bends • Usually presents as local edema with or without pain, can involve nodes and wider lymphatic obstruction • Can get swelling of breast, abdominal areas, extremities • Can be accompanied by skin changes --‘orange peel’ appearance • Treat with recompression --associated pain should respond quickly, but swelling may persist for several days Type I DCS
  77. 77. • Pulmonary (“chokes”) • Neurologic • Vestibular (Inner Ear) Type II DCS Navy diver in MK21 hard hat rig
  78. 78. Pulmonary DCS • 2% of DCS cases • Overwhelming load of venous, inert, gas bubbles in the pulmonary circulation • Animal studies have shown: •  Pulmonary arterial and right ventricular pressure rise •  Cardiac output and O2 sat •  blood vessel permeability • Pulmonary edema Type II DCS
  79. 79. Common scenarios for Pulmonary DCS • Emergency ascents from long, deep dives with large, omitted decompression • Altitude DCS • Caisson workers Type II DCS
  80. 80. Signs and symptoms of Pulmonary DCS • Substernal discomfort • Cough • Pain with inspiration or expiration • May progress rapidly to cardiovascular collapse Type II DCS
  81. 81. Neurologic DCS • More common in recreational diving (up to 80% of reported cases to the Divers Alert Network) • In contrast, Type I, pain-only DCS is the main type in military or commercial diving (approximately 86% of reported cases). • Neurologic DCS tends to present rapidly as noted earlier Type II DCS
  82. 82. Neurologic DCS • Spinal cord most affected (40-60% of cases), then brain, then peripheral nerves • Distinction of cord v. brain doesn’t matter as far as treatment is concerned • Paresthesias and numbness are the most common symptoms Type II DCS
  83. 83. Manifestations of Spinal cord DCS • Signs usually are multi-focal, not conforming to a cord syndrome • May have extremity deficits corresponding to a cord level and a dermatomal pattern • Bowel and/or bladder problems in severe cases Type II DCS
  84. 84. Manifestations of Cerebral DCS • Motor deficits including hemiplegia • Sensory changes • Mental status changes • Loss of coordination, ataxia • Upper motor neuron signs –Hyperactive deep tendon reflexes –Spasticity Type II DCS
  85. 85. Inner Ear DCS, “Staggers” • Mainly in heliox and saturation dives • Possible role of isobaric counter-diffusion --With He and N2 at depth, He more readily diffuses into tissue than N2 diffuses out at the interface of the inner and middle ear, and bubbles form in the inner ear fluid • Structural pathophysiology --Rupture of membranes of semicircular canals and cochlea --Hemorrhage Type II DCS
  86. 86. Signs and Symptoms of Inner Ear DCS • Severe vertigo • Severe nausea and vomiting • Nystagmus • Tinnitus • Hearing loss Type II DCS
  87. 87. Differentiating inner ear DCS from barotrauma • Dive depth and time profile--shallow, no-D dives are unlikely to result in DCS • Point of onset--during descent, unlikely inner ear DCS • Sx with difficult Valsalva suggest baro- trauma • Other signs / Sx of DCS can go along with inner ear DCS Type II DCS
  88. 88. Ocular manifestations • Nystagmus • Diplopia • Visual field defects and scotomata • Homonymous hemianopsia • Central retinal artery occlusion • Optic neuropathy • Ocular muscle impairment • Eyelid muscle pain Type II DCS
  89. 89. • Proposed term including all cases of reduced- pressure, bubble-related disorders, including AGE because distinguishing between neuro DCS and AGE can be very difficult. • In practice, recompression treatment of most cases of neurologic DCS and AGE is the same “Decompression Illness” (DCI)
  90. 90. • DCS/AGE: symptoms of confusion, drowsiness, fatigue, indifference. • AGE attacks brain directly & immediately. • Manifests as acute stroke with focal hemispheric or brain stem injury. Seizure, aphasia, hemiparesis & CV arrest common. • Divers on SCUBA may be susceptible for combination of DCS & AGE. DCI: Brain Involvement
  91. 91. Localized pain 858 91.8 744 76.6 Numbness or paresthesia 199 21.2 41 4.3 Muscular weakness 193 20.6 8 0.8 Skin rash 140 14.9 42 4.4 Dizziness of vertigo 80 8.5 24 2.5 Nausea or vomiting 74 7.9 8 0.8 Visual disturbances 64 6.8 14 1.4 Paralysis 57 6.1 2 0.2 Headache 37 3.9 5 0.5 Unconsciousness 26 2.7 6 0.6 Urinary disturbances 24 2.5 0 - Dyspnea (“chokes”) 19 2.0 4 0.4 Personality change 15 1.6 0 - Agitation or restlessness 13 1.3 0 - Fatigue 12 1.2 2 0.2 Muscular twitching 12 1.2 0 - Convulsions 11 1.1 0 - Incoordination 9 0.9 0 - Equilibrium disturbances 7 0.7 0 - Localized edema 5 0.5 0 - Intestinal disturbances 4 0.4 0 - Auditory disturbance 3 0.3 0 - Cranial nerve involvement 2 0.2 0 - Aphasia 2 0.2 0 - Hemoptysis 2 0.2 0 - Emphysema-subcutaneous 1 0.1 0 - Sign or Symptom Number of Percentage of Number of Percentage of Instances Within Instances Within Instances Manifested Initial 935 Cases 935 Cases Initially Manifestations Frequency of Signs and Symptoms: 935 Cases of Decompression Sickness (Rivera, 1964)
  92. 92. Type Manifestation % Cases Neurological 47 Pain 25 Constitutional 18 Skin 3 Cardiopulmonary 1.5 Lymphatic 0.4 DAN Survey Data 1110 cases of DCI from SCUBA divers (1987-99)
  93. 93. • If you don’t think of it, you won’t ask about recent diving • The key is the clinical, “bedside,” diagnosis of DCS • History: dive profile, latency, symptoms • Exam: neuro findings Diagnosis of DCS
  94. 94. • Short, deep dives—a large pressure change that happens quickly • Omitted decompression • Patent foramen ovale • Cold conditions • Older age • Obesity • Dehydration • Previous episode of DCS DCS Risk Factors
  95. 95. • The sooner the treatment initiated, the better the outcome • Cases of improvement have occurred even after about a week following the pressure exposure Timing of Treatment
  96. 96. • 3 Categories Of Urgency – Emergent: neurologic signs are present and obvious even without an examination • “feet should not be elevated, nor head lowered” • Type II DCS or AGE – Urgent: “only severe symptom is pain” • Can delay briefly for DMO or equipment • Start all normal chamber preps – Timely: symptoms are not obvious without a detailed exam • “only a DMO may make the decision not to treat” Casualty Assessment
  97. 97. Treatment Table 6 (TT6) 0 30 60 30 Total Elapsed Time: 4 hrs 45 minutes (not including descent time) O2 O2 O2 O2 O2 20 20 20 30 60 605 5 5 15 152.4 O2 O2 Descent Rate = 20 fpm Ascent  1 fpm Time at depth, min Air
  98. 98. • Indications – Type II symptoms – Type I symptoms not relieved in 10 minutes – Cutis marmorata – Asymptomatic omitted decompression with > 30 min missed – Symptomatic, uncontrolled (> 20 fsw) ascent – Treatment of unresolved sxs following in-water recompression – Severe CO poisoning, CN poisoning, or smoke inhalation TT6
  99. 99. • Considerations – Can be extended twice at 60 ft (20-5 cycle) and twice at 30 ft (60-15 cycle) (don’t extend for mild joint soreness) – Tender breathes 100% O2 for last 30 minutes of last 30 ft O2 period and to the surface • If > 1 extensions then tender breathes all 60 minutes of last O2 period • If tender has been under pressure in last 12 hours, add 60 minutes 100% O2 at 30 ft to requirement TT6
  100. 100. • Surface O2 at 15 liters/min for up to 12 hours • IV normal saline or lactated Ringer’s, goal of clear urine output (BUT, limit fluids in cases of pulmonary DCS) • Enoxaparin (Lovenox), 30 mg SQ every 12 hours for cases of low-extremity paralysis • Aspirin / NSAIDs, lidocaine, and steroids are NOT recommended Adjunctive Treatment
  101. 101. • 100 % O2 breathing should be initiated during transport to the recompression site • Potential benefits of O2 (1) Enhanced off-gassing of inert gasses (2) Improved tissue oxygenation (3) Decreased cerebral edema Oxygen
  102. 102. • Dehydration decreases tissue oxygenation and off- gassing. • Immersion diuresis, insensible water loss (breathing a dry air source), as well as minimal intake before / during the dive are all factors in dehydration. • AGE/ /Type II DCS (brain) IV 80 - 100 ml/h • Type II DCS (non-brain) IV 200-250 ml/hr Fluid Therapy
  103. 103. • Two options: – Transport to nearest chamber vs. in-water recompression • Transport (preferred) – position prone or left lateral if unconscious – 100% O2 – monitor hydration and body temperature – unpressurized aircraft < 1000 ft if possible • In-water recompression: “only when the delay in transporting to a chamber would cause greater harm” No Chamber
  104. 104. • Climbing to altitude is like ascending to the surface and can bring on DCS • If air transport is necessary, the cabin should be pressurized to 1 ATA: C-9, C-40 (and other commercial airliners), Citation jet, Learjet • If only unpressurized aircraft such as helo’s are available, then the aircraft should be kept below 1000 ft. • Transport on O2 Flying with DCS
  105. 105. Flying After Diving Diver’s Alert Network (DAN) 2002 Consensus Guidelines for Flying After Recreational Diving Applies to air dives followed by flights at cabin altitudes of 2000 to 8000 feet for divers without DCS symptoms
  106. 106. • For a single no-decompression dive: – Wait at least 12 hours before flying • For multiple dives/day or multiple days of diving: – Wait at least 18 hours before flying • For any decompression dives: – “substantially longer than 18 hours appears prudent.” Flying After Diving
  107. 107. • Weight: 25 pounds • Chest mounted • Oxygen bottle volume: 1.5 liters • Oxygen bottle working pressure: 200 BARS • Canister duration: 115- 200 minutes Rebreathers: Draeger LAR V
  108. 108. Rebreathers
  109. 109. • Decompression sickness • Nitrogen narcosis • Hypoxia • Oxygen toxicity • CO2 toxicity • Caustic cocktail • Draeger Ear Medical Considerations in Rebreather Diving
  110. 110. • Caused by canister leak • Highly alkaline solution – Sofnolime (a typical CO2 scrubber material) • >75% Calcium hydroxide • 3% Sodium hydroxide – Lithium hydroxide is 10 times more toxic than Sofnolime/Sodasorb. • Usually preceded by symptoms of hypercarbia Caustic Cocktail
  111. 111. • Also known as “Draeger Ear” • Refers to the negative pressure that develops in middle ear after long O2 dives. • Sxs: ear pain, pressure, hearing loss, crackling sensation secondary to middle ear effusion. • Dx: may look like mild squeeze, +/- middle ear effusion. • Tx: decongestants • Avoid by periodic valsalva post O2 dive. Middle Ear Oxygen Absorption Syndrome
  112. 112. • Analgesics • NSAIDS • Decongestants • Antibiotics • Topicals • Antacids • Vitamins Considered Safe in Diving
  113. 113. Questions? Hang Loose!
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