Decompression Illness Flashcards
Define Dysbarism
Any disease induced by change in pressure, includes both trapped and evolved gases
Decompression sickness, arterial gas embolus and barotrauma
Define Decompression Sickness
Evolved gas disease
Define arterial gas embolus
Pulmonary barotrauma with embolisation usually to cerebral
Decompression illness
Modern preferred term - similar to old term dysbarism
Clinical more descriptive term introduced due to difficulty in distinguishing DCS and CAGE
Explain the pathophysiology of DCI
Inert gas No is diffused into tissues down concentration gradient (supersaturation)
On ascent, the elimination of inert gas mirrors the process of uptake. Bubbles are formed in different areas of the body. As per Henry’s law.
If <2:1 or 1/2 atm the bubble form instead of dissolve out. Form on surface
If a state of supersaturation develops, bubbles can form out of solution (Haldane’s hypothesis)
Formation of bubbles - Henry’s law, Haldane’s critical supersaturation theory Pre-existing conditions: - Bubble micronuclei - Hydrophobic interfaces - Vascular turbulence - Tribonucleation/Cavitation Persistence of bubble - effects of surface tension/surfactants - LaPlace’s law Boyle’s law: Once formed
What are the primary and secondary effects of bubble formation
primary
- Bubbles - evolved or embolus
- fragments
- compress
- Obstruct
Secondary
- Stimulation of inflammatory processes by activation of Complement, kin in, coagulation, leukocyte response
- Endothelial dysfunction - leaking vessels
- Microparticle formation
- often delayed symptoms
Venous Gas emboli creation and effects
Genesis
- Arise de novo in low pressure areas
- Flow in venous plexi may favour formation
- promoted by presence of micronuclei
Effects
- Haematological - pro inflam, pro coag
- Venous infarction - venous stasis, how bends happen to the spine
- Embolic via right heart to the lungs increases MPAP - causes right heart failure
Arterial bubble creation and effects
Genesis
- Unlikely to form de novo in high pressure
- rarely supersaturated
- usual cause is via Venous gas emboli via paradoxical R to L shunts (PFO) or penetrate bubble filter. Or pulmonary barotrauma.
Effects
- Damage endothelium - strips surfactant, increase permeability
- Haemoconcentration
- activate inflammatory cascades
What is the role of PFO in DCI
Seems assoicated with more severe DCI
- CAGE
- Neurological/spine
- inner ear
- Cutaneous
Theoretical risks of PFO
- R to L shunting
- Increase R atrial pressure
- CAGE
- Anti-G straining
- Positive pressure breathing
Clinical features for DCI
MSK- joints: localised pain, worse on movement. Most common
Cutaneous - skin: itching, formication, mottled rash can migrate
Neurological - Brain, spinal cord and peripheral nerves. Altered sensation, Confusion, memory loss and disorientation. Visual abnormalities, mood, seizure, ascending weakness or paralysis in legs.
Pulmonary - dry persistent cough, retrosternal pain, SOB
Audiovestibular - vertigo, tinnitus nausea and vomiting, hearing impairment
Constitutional: Headaches, unexplained fatigue/ lethargy, poorly localised aches and pain
Describe the musculoskeletal DCI symptoms, findings and pathology
Symptoms
- Migratory periarticular mono/polyarthralgia
- severity varies - minor niggle to severe
- May be delayed onset 24-48hrs
- may be migratory
Findings
- Exam usually unremarkable
- Better with pressure
- worse with use
Pathology
- uncertain
- Pain from periosteum/ligaments/tendons
- mass effects
- inflammation
Cutaneous DCI symptoms, findings, pathology
Symptoms
- pruritus
- formication
- rash
- hyperaesthesia
Findings
- Erythematous macular rash
- Marbling
- Cutis marmorata - marker of severe
Pathology
- Subcutaneous bubble formation
- Inflammatory reaction
Respiratory DCI symptoms, findings and pathology
Symptoms
- Chest pain
- chest tightness
- cough
- shortness of breath
Findings
- Bronchoconstriction
- Increased pulmonary artery pressure
Pathology
- Lung bubble filter overwhelmed
- pulmonary inflammation
- oedema in alveoli and bronchi
Neurological DCI symptoms, findings and pathology
Symptoms
- Variable, depending on site of bubble
- focal deficits
- Peripheral nerve issues most common
- spinal cord
Findings
- variable
- can get motor and sensory signs
- balance/proprioception
- Cognitive deficits
Pathology
- usually embolic as autochthonous is very rare
- leaky blood brain barrier
Inflammatory reaction
Spinal cord DCI symptoms, findings and pathology
Symptoms
- girdling pain
- Sensorimotor deficits
- paralysis
Findings
- motor/sensory signs
- Balance/proprioception
- poor prognosis
Pathology
- atrial emboli
- venous infarction in plexus
- compression by tissue bubbles
