EDUCATIONAL OBJECTIVES A FISH FOR YOU! HYPERBARIC MEDICINE REVIEW FOR THE CAQ EXAM MARY E. HANLEY, DO, UHM REVIEW MATERIAL THAT COMMONLY APPEARS ON CAQ EXAM REVIEW GAS LAWS AND THE BASIC MATH OF HYPERBARIC AND DIVE MEDICINE REVIEW INDICATIONS AND CONTRAINDICATIONS OF HYPERBARIC OXYGEN THERAPY HOPEFULLY NOT PUT EVERYONE TO SLEEP GAS LAWS 1.Boyle s Law 2.Charles Law Boyle s Law at constant temperature, the volume of the gas increases as the pressure decreases. The volume of the gas decreases and the pressure increases. V P 3.Gay-Lussac s Law V o l u m e L P1V1 = P2V2 If you squeeze a gas sample, you make its volume smaller. Pressure (kpa) BOYLE S LAW Boyles if the only gas law we use that is INVERSELY proportional! As pressure increases, volume decreases AT A CONSTANT TEMPERATURE. Moveabl piston Now... a container where the volume can change (syringe) Same temperature Volume is 100 ml at 25 C Volume is 50 ml at 25 C M-1
CHARLES LAW Charles Law at a constant pressure, the volume of a gas increases as the temperature of the gas increases and the volume decreases when the temperature decreases. CHARLES LAW increase AKE increase the speed of V ol the particles u the walls of a flexible m container expand e think of hot air balloons! L Temperature (K) V1 T1 = V2 T2 Steel cylinder (2L) contains 500 molecules of O2 at 400 K Steel cylinder (2L) contains 500 molecules of O2 at 800 K 1. In which system do the O2 molecules have the highest average kinetic energy? B 2. In which system will the particles collide with the container walls with the greatest force? B 3. In which system is the pressure higher? B GAY LUSSAC S LAW Gay-Lussac s Law the pressure of a gas is directly proportional to its absolute temperature at a constant volume GAY LUSSAC S LAW WE SEE THIS LAW IN ACTION EVERYDAY WHENVER WE TREAT A PATIENT WITH HYPERBARIC OXYGEN. P1 T1 = P2 T2 Pressure (atm) AS WE INCREASE PRESSURE, TEMPERATURE GOES UP AND PATIENTS COMPLAIN OF BEING WARM. AS WE DECREASE PRESSURE AT THE END OF THE TREATMENT, PATIENTS OFTEN COMPLAIN OF FEELING COLD. Temperature (K) PTV TO REMEMBER HOW THESE WORK, THINK: PUBLIC TELE VISION WE ARE CONCERNED WITH PRESSURE, TEMPERATURE AND VOLUME WHICH CONSTANTS GO WITH WHICH LAW? CHARLES LAW: CHEESE PIZZA (PRESSURE) BOYLES LAW: BLT (TEMPERATURE) GAY LUSSAC S LAW: GREEN LEAFY VEGGIES (VOLUME) M-2
COMBINED GAS LAW.. IDEAL GAS LAW PV = nrt P1V1 T1 = P2V2 T2 COMBINATION OF BOYLE S, CHARLES AND GAY LUSSAC LAWS Note that all temperatures must be in Kelvin! OK, HERE COME THE MATH (run!!!) IF YOU LIVE IN RHODE ISLAND. The earth s atmosphere weighs down on us with a specific amount of pressure. THE MATH (CONT D) THE MATH (C0NT D) At sea level, where I live, we experience 1 atmosphere of pressure. For every 33 feet you descend in sea water, you experience an additional atmosphere. By convention, when we talk about pressurized environments, we count the fact that everyone starts at sea level, so we speak of ATMOSPHERES ABSOLUTE OR A.T.A. M-3
THE MATH (CONT D) We know that Hyperbaric Oxygen therapy was born out of the diving industry to treat the Bends. In the USA, many gauges read in FEET OF SEA WATER (FSW) IF YOU DIVE TO 33 FSW, YOU ARE NOW AT 2 ATA ( 1 Atmosphere of the earth + 1 Atmosphere of water) Stay with me, it gets better! THE MATH (CONT D) We can also measure pressure and that is in mm Hg. ***REMEMBER: AT SEA LEVEL: 1 ATA (ATMOSPHERE ABSOLUTE) = 760 mmhg We know that at sea level, there is 21% oxygen in the air we breathe. The rest is nitrogen 0.21 x 760mmHg= 160mmHg of Oxygen CONVERSIONS REMEMBER: all answers must be in ATA and degrees Kelvin Degrees Kelvin = Centigrade + 273 Hyperbaric Medicine Physics Atmospheric pressure: = 33 ft (sea water) 34 ft (fresh water) 10 mt (sea water) 14,965 psi 760 mmhg (Torr) 101,3 KPa Medicine Conversion: Depth vs Pressure P ATA = (Depth/33) + 1 D = (P ATA 1) X 33. Wound Recovery & Hyperbaric Medicine Center Kent Hospital 2010 Hyperbaric Medicine Main Menu Hyperbaric Medicine Main Menu Decompression Sickness Decompression sickness - Caisson disease or the bends - Attributed to formation of nitrogen bubbles in the body on decompression Under pressure, Nitrogen is forced in solution in the blood Carbon monoxide poisoning is the leading cause of injury and death by poisoning in the world Affinity of CO for hemoglobin (forming carboxyhemoglobin) is 220 times higher than for oxygen Also occurs in miners and astronauts HBO causes carboxyhemoglobin dissociation to occur faster than pure oxygen at sea level pressure. Wound Recovery & Hyperbaric Medicine Center Kent Hospital 2010 Wound Recovery & Hyperbaric Medicine Center Kent Hospital 2010 M-4
HOW DOES HBO2 WORK? PAO2= FiO2 (PB-47= 713 at sea level) PaCO2 / R Reverses hypoxia Alters ischemia reperfusion effect Influences vascular permeability Reduces edema Modulates Nitric Oxide production Modifies growth factor expression, Cytokine levels Adjusts cellular ion exchange HOW DOES HBO2 WORK? (CONT D) Promotes cellular proliferation Accelerates collagen production Stimulates capillary budding, angiogenesis, neovascularization Promotes WBC microbial oxidative killing Increases select antibiotic membrane crossing Deactivates clostridial toxins Directly anaerobicidal Modulates immune system response CYANIDE POISONING LETS ANSWER SOME QUESTIONS!!! COMMONLY SEEN IN VICTIMS REMOVED FROM STRUCTURE FIRES INCOMPLETE COMBUSTION OF NYLON, VINYL, PLASTICS PRODUCE CYANIDE. MAY HAVE CO AND CYANIDE POISONING IN SAME VICTIM TREATMENT : ADMINISTER CYANOCOBALAMIN WHICH WILL TURN URINE A DEEP RED WINE COLOR. HYPERBARIC OXYGEN TREATMENT IMPROVES OUTCOMES FOR BOTH CO AND CYANIDE POISONING, AND DECREASES THE DEVELOPMENT OF DELAYED NEUROLOGIC SEQUELAE What modified TEED score would be used to describe a perforated TM? 1. Grade 0 2. Grade 1 3. Grade 5 4. Grade 6 Answer: #3 Middle ear barotrauma was classified by Teeds in 1944 Ranges from 0 which is normal otoscopic exam to a 5 which is a perforated Tympanic Membrane. Grade 0= normal Grade 1 = tympanic membrane injection or retraction Grade 2= slightly hemorrhagic tympanic membrane Grade 3 = grossly hemorrhagic tympanic membrane Grade 4 = hemotympanum Grade 5 = perforation of TM Note that previous scarring of TM will increase the risk of perforation! M-5
What is the mechanism of action in carbon monoxide poisoning? 1. Direct brain cell toxicity 2. acute lung injury 3. acute hemolysis 4. displacement of oxygen from hemoglobin Answer: #4 displacement of O2 from hemoglobin Oxygen has a much lower affinity for hemoglobin than CO This causes hypoxic injury to the brain Acute lung injury can occur from smoke inhalation G6PD deficiency can cause acute hemolysis with exposure to various substances such as sulfa drugs and fava beans. What is normal oxygen partial pressure at sea level? 1. 760 mm Hg 2. 105 mm Hg ANSWER: #4 160 MM HG The percentage of oxygen in room air is 21%.21 x 760 = 160 mm Hg 3. 21 mm Hg 4. 160 mm Hg Which of the following is an indication of acute oxygen toxicity? 1. Alertness 2. Paresthesias 3. Cyanosis Answer: # 2 Paresthesias Signs of acute oxygen toxicity include dyspnea, chest pain or burning, paresthesias and seizure. We use air breaks during hyperbaric treatments to decrease the amount of time the patient is breathing 100% oxygen and to decrease the risk of oxygen toxicity. 4. Tachycardia M-6
Cherry-red skin in a comatose patient suggests the diagnosis of : 1. Carbon monoxide poisoning 2. Methemoglobinemia 3. Polycythemia Answer: #1 Carbon monoxide poisoning Cherry red skin in a comatose patient suggests carbon dioxide poisoning. This may be seen post mortem. Cherry red mucous membranes may be seen in a patient with cyanide poisoning. 4. Bacteremia Post scuba diving, a patient complains of red eyes and periorbital bruising. Visual acuity, EOM, ocular pressures are all normal. What is your next step? 1.Reassure the patient, telling him his symptoms should resolve in two or more weeks. 2. Order a CT scan of the orbits to look for fracture. 3. Transfer patient to nearest facility for hyperbaric oxygen treatment. 4. consult ophthalmology stat Answer: #1 reassure patient & tell him symptoms will resolve in 1-2 weeks This is mask squeeze. No treatment is needed A CT or MRI of the orbits is indicated if there is evidence of significant injury to the eye such as decreased vision or pain. Hyperbaric oxygen treatment is indicated for decompression illness and air embolism. Hyperbaric oxygen is not needed to treat mask squeeze Ophthalmology should be consulted if there is evidence of significant injury to the eye such a decreased visual acuity or oculomotor paralysis. Relax, take deep breaths, and Good Luck on the Exam!!!! Thank you for your attention! M-7