Hyperbaric Physiology The Rouse Story • Oct 12, 1992, off the New Jersey coast • father/son team of experienced divers • explore submarine wreck in 230 ft (70 m) • breathing compressed air • trapped in wreck & escaped with no time for decompression Chris and Chrissy Rouse Arrival at recompression Recompression efforts facility • Both divers directly ascend to dive boat • Recompression starts about 3 hrs after • Helicopter arrives at boat in 1 hr 27 min ascent • Bronx Municipal Hospital recompression facility – put on pure O2 and compressed to 60 ft – Chris (39 yrs) pronounced dead • extreme pain as circulation returned – compressed to 165 ft, then over 5.5 hrs – Chrissy (22 yrs) gradually ascended back to 30 ft., lost • coherent and talking consciousness • paralysis from chest down • no pain – back to 60 ft. Heart failure and death • blood sample contained foam • autopsy revealed that the heart contained only foam Medical Debriefing Gas Laws • Boyle’s Law • Doctors conclusions regarding their – P1V1 = P2V2 treatment • Dalton’s Law – nothing short of recompression to extreme – total pressure is the sum of the partial pressures depths - 300 to 400 ft • Henry’s Law – saturation treatment lasting several days – the amt of gas dissolved in liquid at any temp is – complete blood transfusion proportional to it’s partial pressure and solubility – deep helium recompression 1 Scuba tank ~ 64 cf of air Gas problems during diving Henry, 1 ATM=33 ft gas (10 m) dissovled = gas Pp & tissue • Rapture of the deep (Nitrogen narcosis) solubility • Oxygen toxicity •Hypoxia Dalton, total • Contaminated gases press. = sum of the • Hypercapnia partial pressures Boyle, ↑ press ↓ vol Martini’s Law Narcotic gases • Every fifty feet of depth is • All Noble gases cause narcosis approximately equal to drinking – outer shell filled with electrons one martini on an empty • chemically inert but narcotic properties depend on stomach (increased N2 in tissues) their solubility in body fat • euphoria at > 30m • mechanism for narcosis is unknown (cell membrane) • at pressures > 100m, unconsciousness • determines a physical limit for Nitrogen narcosis breathing air at depth • no apparent adaptation in humans High Pressure Nervous Oxygen Toxicity Syndrome (HPNS) • Occurs from breathing 100% O2 too • Increasing pressure reverses the effects long of narcosis – in 1 ATM, > 12hrs – hyper-excitability effect • Occurs from pressuring a gas mixture – mechanism is also unknown – in 7 ATM, > 5 min • fluidity of membranes, NT release, post- • Symptoms synaptic effects? – coughing, mild irritation under sternum, burning in trachea or bronchi • Forms a barrier to very deep diving – convulsions – HPNS at pressures > 200m 2 Symptoms of HPNS Mixed gases • Rapid tremor, poor coordination, involuntary • Prevents HPNS jerking movements, microsleep • reduces gas density • no evidence of adaptation in humans – work of breathing increases with depth as gas • addition of narcotic gases decreases the density increases effect and increases max depth – helium and hydrogen are much less dense than – Trimix (helium, nitrogen, oxygen) air – heliox (helium and oxygen) – mixed with O2 will support ventilation with light – nitrox (air enriched with oxygen) work at depths as deep as 1500m • HPNS limits the max depth humans can dive • controls oxygen level (↓O2 as ↑depth) Breathe hold diving Hyperbaric injuries • Oldest form of diving • Lung squeeze – 4500 BC artifacts (30m or more) –Ama divers –TLC < RV • time limitations • fluid is drawn – usually about 60 s into alveoli – hyperventilation, 4.5 min • alveoli rupture – world record, 7 min 41s • pneumothorax – hyperven. + O2, 20.1 min • Middle ear • risks squeeze – blackout – affects 40% of – barotrauma divers Hyperbaric injuries, cont. Decompression Sickness • Sinus squeeze (infection and • Caissons used in 1840 to build bridges allergies) – bends, chokes, staggers (vestibular system) • face-mask squeeze (ruptured eye vessels) • Nitrogen forms bubbles during ascent • GI barotrauma (chew gum, carbonated • occurs after dives > 30m fluids, beans) • symptoms usually appear within 3 hrs of • Alternobaric vertigo (unequal middle completing the dive ear pressure) – joint pain • Air embolism(failure to breathe out during – neurological hits, paralysis, confusion ascent) – has occurred in depths as little as 6 – skin mottling ft 3 DCS Tables history Decompression Tables • Paul Bert--first Depth, ft described DCS • JS Haldane-- developed first DCS tables – descend rapidly, spend limited time on the bottom, ascend slowly to the surface in stages – ascend 1/2 way rapidly – ascend set amts and stop Dysbaric Osteonecrosis Open Circuit Scuba Gear • Divers with a history of • Air is fed with a DCS demand regulator at • 20% in divers who ambient pressure work below 200m • air is exhaled to the • bubbles reduce water forming capillary flow to bone bubbles and cause bone cells to die • damage mainly in the end of long bones Closed Circuit Scuba Gear • Air is fed to the diver with a demand regulator at ambient pressure • 100% O2 is recycled through a CO2 scrubber • depth is limited – to < 8m for pure O2 – to < 25m with 60% O2, 40% air Jacques Cousteau and Emile Gagnan developed the demand • must purge nitrogen periodically value in 1943 • No bubbles 4 Carbon Dioxide Toxicity CO2 symptoms • Occurs with closed systems – diving for > 4-6 hrs – headache is usually the critical first warning • Occurs at depth due to pressure – First described by JBS Haldane – Br sub Thetis sunk in 1939, 99 men died only 4 escaped – small escape chamber where men exhaled and CO2 increased to 6% – when escape pressure was pressurized to 10 ATM, CO2 effect became fatal Cardiac arrhythmias Drowning • A Perfect Storm pgs 179-186 • Common during diving even in young • A graphic description of what it feels like divers to drown – 22 x more arrhythmias when submerged – based on report by James Lowson 1892 •Why? – shipwreck survivor – blood pressure increase with breathe hold • stages of drowning – pressure from wet suit on the carotid sinus – struggling to hold breath – fatigue, dehydration, cold – must breathe, water triggers laryngeal spasm – increased central blood volume – pain recedes, euphoric feeling, final thoughts – unconsciousness Susceptible Populations for Other precautions DCS • Females? • Avoid dehydration – Greater body fat (↑ nitrogen dissolved in fat)? • no strenuous exercise 6 hrs after diving – increased symptoms during menstruation • do not fly for at least 12-24 hrs after – don’t dive when pregnant! diving • Age effect • increase decompression time when – > in middle-aged than younger men diving at altitude • Foramen Ovale – inadequate closure of hole between right and left atria in 25% of people – bubbles may occur in the cerebral circulation 5 Limits • 30m, nitrogen narcosis (limit for air) • 30 - 200m, oxygen toxicity and increased work of breathing (breathe mixed gases) • > 200m HPNS, breathe trimix gas • 450m, limit for open sea diving • 600m, limit with pressure chamber Saturation Diving The abyss • Live and work at depths up • Abyssal plains to about 300m to avoid • need pressure-resistant lengthy decompression – breathe heliox vessels – following 100m, 4 d – 1620, first submarine decompression (Cornelius Drebbel) – following 300m, 10 d – 1934, bathysphere, William decompression Beebe and Otis Barton • helium speech unscrambler – 1940, bathyscaphe, Auguste Piccard 1985 Alvin • 30oC living quarters discovers – 1960, Trieste lands in the Titanic Mariana Trench Tektite II 1970 6.