See: [Cameron - Dysbarism](x-devonthink-item://10DC3BB1-027C-40D6-BDB3-4AF0C6B160E6?page=777), [Tintinalli decompression sickness](x-devonthink-item://FEDB96F9-3A4C-48E0-94CF-9ECFCE5D8E93?page=38&start=272&length=23&search=DECOMPRESSION%20SICKNESS%0A), [Rosen Scuba diving and dybarism](x-devonthink-item://CE6E0210-A590-441A-9626-4DCD974FF2E3), [Dunn - Diving medicine](x-devonthink-item://6C92C286-C56A-46C8-B5C5-62CDADBAF8C3) see also: [[Drowning]], [[Marine Envenomation]] > [!key points] > - **Decompression illness** (DCI) is a term that encompasses arterial gas embolism (AGE) and decompression sickness (DCS). > - **Decompression sickness** = *nitrogen bubbles* form in tissues, vessels. neuro, MSK, skin sx within 30-60 min of surfacing > - described by onset, evolution of sx, body system, +/- barotrauma . eg "acute progressive neurological DCI with no evidence of barotrauma" > - **Arterial Gas embolism** = *barotrauma* rapid expansion and tear of pulm tissue → direct entry of bubbles into arterial circulation. > - look for LOC, cog impairment, focal neuro deficits > > #### Treatment considerations > - re-compression therapy ([[Hyperbaric oxygen therapy|hyperbaric]]) indicated for decompression illness or arterial gas embolism > - Keep flat/supine > - High flow o2 15L NRB > - Fixed wing pressurised cabin if retrieval or low altitude in helicopter > check to ensure do not have urinary retention or pneumothorax as can be exacerbated in a hyperbaric chamber > [!important]- "classic" question: collapse on Beach DDx > *Non-marine related* > - cardiac (ACS, arrhythmia) > - CNS -- ICH (spontaneous or traumatic) or high grade SAH, stroke > - PE > - hypoglycaemia > > *Marine-related* (see [[Marine Envenomation]]) > - box jellyfish > - blue ringed octopus > - sea snake > - stone fish > - stingray > > *Diving-related* > - Arterial gas embolism (brain or spinal cord syndrome) > - Pulm barotrauma causing tension PTx and obstructive shock > - hypoxia from empty tanks > - water aspiration > - oxygen toxicity / seizures > - nitrogen narcosis (rare as improves on ascent) > - contamination of inspired gas eg CO -- only if on Hooka system > --- > - [RMH 2023 - Beach collapse](x-devonthink-item://CF52CD70-BFC7-407E-B0FA-079027D23E62) **Dysbarism** == medical complications of exposure to gasses at higher than normal atmospheric pressure - includes barotrauma and decompression illness # Diving overview ## Diving safety **Diving tables** (thanks Randol for explanation) The diving tables explain the *maximum safe depth* for a given type of diving and the *schedule for safe decompression*. They vary based on the type of gas mixture and other aspects of the dive. Eg mountain lakes tables are much different than seawater tables. Diving organisations publish tables, as does the navy and other private commercial enterprises. ## Diving Physics For every 10 m a diver descends in seawater, the pressure increases by 1 atmosphere absolute (ATA). This pressure change impacts on gas spaces within the body according to Boyle's law > [!TLDR] Boyle's Law > PV = k > *at a constant temperature, the volume of a gas varies inversley to the pressure acting on it* The proportionate change in volume is greatest near the surface **Dalton's law** states that the total pressure exerted by a mixture of gases is equal to the sum of the pressures of the constituent gases **Therefore**, as divers breathe air at increasing atmospheric pressure, the partial pressures of nitrogen and oxygen increase. Surface = 1 ATA = 0.8 ATA N2 + 0.2 ATA O2 10m = 2 ATA = 1.6 ATA N2 + 0.4ATA O2 40m = 5 ATA = 4.0 ATA N2 + 1.0 ATA O2 > A diver breathing air at 40 m is inhaling a gas with a partial pressure of oxygen equivalent to breathing 100% o2 at the surface. At partial pressures above 3 ATA,the N2 affects coordination and judgement (**"nitrogen narcosis"** ) . Recrational scuba diving generally has a limit of 40m because of these effects. **Henry's law** states that at a constant temperature, the amount of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas in contact with the liquid. Q = KPgas ## Nitrogen absorbed by tissues Henry's law is relevant in diving illness because it is the basis of **decompression illness** > As ambient pressure increases, the diver is exposed to increasing partial pressures of nitrogen, which dissolve in bodily fluids. the amount of nitrogen absorbed depends on both the depth (which determines the partial pressure of nitrogen) and the duration of the dive. Tissues will also take up nitrogen at different rates depending on thier blood supply and permeability. eventually, the tissue becomes saturated. As the diver ascends and ambient pressure decreases, the partial pressure of nitrogen in some tissues will exceed ambient pressure and result in tissue supersaturation. if the diver ascends slowly enough, the nitrogen diffuses out of the tissues and is transported dissolved in the blood to the lungs for elimination. this is **off gassing**. ==if the diver ascends too rapidly, sufficient nitrogen bubbles will form in their body to cause decompression illness== > Oxygen does not cause these problems because it is rapidly metabolised by the tissues # Assessment of injured diver - ==give 100% oxygen== during assessment - ==horizontal position to avoid re-embolization== if history concerning for arterial gas embolism - if sx progressively rapid, rapid acces to recompression - Diver history - number of dives over recent days - depth - bottom time - performance of any decompression or safety stops - dive complications/rapid ascents - surface interval btwn dives - time from completing dive and onset of sx. - recent exposure to altitude ## Vertigo and headache in divers - ==all cases of vertigo in divers== (even if resolved) require specialist assessment - most common cause, alternbaric vertigo, egins just as divers commence thie rascent and is caused by unequal middle ear pressures. usually lasts only a few minutes # Barotrauma > Barotrauma occurs when changes in ambient pressure lead to expansion or contraction of gas within enclosed body cavities > [!quote] > “Barotrauma describes any injury due to pressure. Decompression sickness is barotrauma on a microscopic level and will be discussed in its own section. Barotrauma here will refer here to large tissue damage induced by pressure changes in diving. Barotrauma can occur at any anatomical location where gas is located, namely the lungs, gastrointestinal tract, inner ear and the sinuses. > > Barotrauma is *nearly always a result of inappropriate decompression and ascent*. The largest studies around barotrauma and its effects come from submarine escape trainees who perform rapid, emergent ascents, sometimes from great depths. The effects of pulmonary barotrauma are second only to simple drowning as causes of death in divers.” - Randol ## middle ear barotrauma - most common medical disorder in diving - ear pain, tinnitus, conductive hearing loss - mild vertigo may be experienced - more severe vertigo if water passes through a perforated TM; severe vertigo would be concerning for inner ear barotrauma **Treatment** - analgesia - decongestants - ENT referral if there is tympanic membrane perforation or suspected inner ear barotrauma - antibiotics are indicated due to potential contamination with water - do not dive again until resolved and TM healed and eustacian tube is patent ## Inner-ear barotrauma - sudden pressure changes btwn middle and inner ears can cause rupture of round or oval windows or a tear of reissner's membrane - usually due to rapid descent without equalizing or foreceful valsalva manoeuvres - sudden onset tinnitus, vertigo, nausea, and vomiting, vestibular symptoms, profound sensorineural hearing loss - onset of sx that occur after diving performing an activity that increases intracranial pressure eg heavy lifting suggests IEBT - coexistent middle-ear barotrauma is absent in 1/3 of cases - DDx is decompression injury involving the inner ear or vestibular apparatus - because of overlap of sx, **early specialist advise suggested** **Treatment** - avoid activities - ENT referral (same day) - audiometry - antiemetics - supine with head on pillow; if DCI excluded, then 45 deg head OK - consider re-compression if DCI not excluded ## Sinus Barotrauma - tx analgesia, decongestants, and avoid diving until better - +/- abx if secondary infection ## mask squeeze - ensure normal visual acuity ## Gastrointestinal barotrauma - expansion of gas within GI tract on ascent can cause colicky abdo pain - rupture of stomach is rare - shoulder pain may be due to diphragmatic irritation or DCI - DDx pulmonary barotrauma ## Pulmonary barotrauma - diver ascends without exhailing adequately and the expanded gas in the lungs exceeds the lungs elasticity, tearing alveoli - most commonly when a diver runs out of air, panics, and ascends too rapidly - even a change in pressure over 1m near the surface is sufficient to cause lung barotrauma **clinical features** - rapid onset of symptoms - if [[Pneumomediastinum]] or pneumothorax is detected after diving, it is essential to look for features c/w associated **arterial gas embolism** - loss of conscousness - cog impairment/loss of memory - neurologic abnormalities **Treatment** - if arterial gas embolism suspected, then keep supline and urgent recompression treatment is requirement - [[Trauma/pneumothorax]] from pulmonary barotrauma should be managed identically to non-diving related causes - pneumomediastinum and subcutaneous emphysema in abscens of arterial gas embolism usually managed conservatively - if sx severe, give 100% oxygen to resolve trapped gas # Decompression illness ## Diving history to ask - number of dives over recent days - dive profile from tables (depth, times, ascent rates, surface intervals, safety/decompression stops) - bottom time - performance of any decompression or safety stops - dive complications/rapid ascents - problems equalising. equipment issues - surface interval between dives - time from completing dive and onset of symptoms - altitude / flight between dives ## Diagnostic criteria - onset (acute/chronic) - evolution of symptoms (spontaneous resolving/static/progressive/relapsing) - body system affected (MSK/cutaneous/lymphatic/neuro/vestibular/cardiorespiritory) - presence/absence of barotrauma ## Treatment # Hyperbaric oxygen benifical effects: - reduce bubble size in accordance with boyle's law --> reducing obstruction caused by intravascular bubbles and tissue distorsion of extravascular bubbles - increase outward diffuse gradient for nitrogen - relief of tissue ischameia and hypoxia adverse effects of hyperbaric oxygen - oxygen toxicity # Nitrogen narcosis # diving-related pulmonary oedemia # decompression illness vs arterial gas embolism **Decompression illness**  - nitrogen bubbles form in tissues, vessels, and activate inflammatory cascade - gradual onset of neuro, MSK, and/or skin sx within 30-60 min of surfacing  **arterial gas embolism**  - barotrauma--rapid expansion. tear of pulm tissue → direct entry of bubbles into arterial circulation - usually occur on ascent or immediatly upon surfacing   - if pneumomediastinum or pneumothorax is detected after diving, it is essential to look for features c/w associated **arterial gas embolism** - loss of conscousness - cog impairment/loss of memory - neurologic abnormalities **Treatment** - if arterial gas embolism suspected, then keep supline and urgent recompression treatment is requirement ![[Pasted image 20241023135043.png]] # Related questions ## diving - [x] 3Q: [Decompression sickness](x-devonthink-item://4134DDB3-6E12-474A-9F6F-64135C0C6048?page=38) -- [Answer](x-devonthink-item://AC92B5F1-8EE6-461A-B03E-F70AE7DC1275?page=39) - [ ] 4Q: [Complications of diving](x-devonthink-item://CA0CC973-6102-4C33-AB59-A43A87724DF0?page=12) -- [Answer](x-devonthink-item://9F437E5A-02D4-43FC-B795-5386EDE954F3?page=10) - [x] 5Q: [Decompression sickness](x-devonthink-item://8AAAF35C-CCF4-4157-9551-5B05727AA0CD?page=5) -- [Answer](x-devonthink-item://FDFBA3A1-6207-4204-AB6D-7483D80C5B5C?page=5) - [x] DUPLICATE Q: [Decompression sickness](x-devonthink-item://8AAAF35C-CCF4-4157-9551-5B05727AA0CD?page=5) -- [Answer](x-devonthink-item://FDFBA3A1-6207-4204-AB6D-7483D80C5B5C?page=5) - [ ] 6Q: [Decompression sickness](x-devonthink-item://2F267333-5FEC-47E5-83D1-CC05B23EB91A?page=11) -- [Answer](x-devonthink-item://C6CAC39D-CAE8-4F76-9C45-689A0464D936?page=8) - [ ] 7Q: [Decompression illness](x-devonthink-item://F0498813-9350-484C-AD5B-6FF7C3AE9015?page=32) -- [Answer](x-devonthink-item://A491A3F6-FD6D-492F-BCBE-7F7BAE101EDF?page=32) - [ ] 8Q: [Decompression sickness](x-devonthink-item://5FC539E5-7F1D-48E5-B062-83009DA98093?page=5) -- [Answer](x-devonthink-item://D25C2F83-6C30-4F45-8B5B-6E7E57BD24A3?page=3) - [ ] 9Q: [Cutis Marmorata](x-devonthink-item://662C8511-01CD-4659-B57D-5A01CF74D69B?page=16) -- [Answer](x-devonthink-item://79A95C0A-634E-4B38-9131-78949F63D56F?page=14) - [ ] 10Q: [Decompression Illness](x-devonthink-item://7061D1B4-0AB9-4963-B3B0-23BDD975B2CD?page=55) -- [Answer](x-devonthink-item://3F30C77E-E23E-4200-89FE-48A41618E0C2?page=37)