13-Feb-161High Atitude High Altitude Acclimatization

13-Feb-16High Atitude2 Hypoxia of High Altitude As one ascends to high altitudes One encounters problems associated Hypoxia, increased radiation & exposure to cold temp Basic cause of hypoxia As altitude increases Barometric pressure falls % Composition of air does not change appreciably Partial pressures of respiratory gases fall

13-Feb-16High Atitude3 Hypoxia of High Altitude At an altitude of 18,000 ft (5,500 m) Barometric pressure is ½ normal (380 mm Hg) P O2 of moist inspired gas (380-47)* = 70 mm Hg Note kilimanjaro is at 19,360 ft

13-Feb-16High Atitude4 Hypoxia of High Altitude At summit of Everest 29,028 ft Barometric pressure = 250 mm Hg P O2 of moist inspired gas = 43 mm Hg At altitude of 63,000 ft Barometric pressure =47 mm Hg P O2 of moist inspired gas = 0

13-Feb-16High Atitude5 Effect of High Altitude on Bar Pres and P O2 Altitude (ft) Pressure mm Hg P O2 air mm Hg Remarks 63, , , Severe O 2 lack despite use of 100% O 2 33, ¼ atmos, Mt Everest 29,028(250 mm Hg) 20, Danger to life unless O 2 added to inspired air, 18, ½ atmos, Kili 19,360 10, >12,000 definite O 2 lack Up to 8,000 safe zone

13-Feb-16High Atitude6 High Altitude Vs P AO2, P ACO2, O 2 Sat% Altitude (ft) Bar.Pre s (mm Hg) P O2 in air (mm Hg) P AO2 (mm Hg) P ACO2 (mm Hg) Art. O 2 sat% 63, , , ,

13-Feb-16High Atitude7 Hypoxia of High Altitude Effect of CO 2 & water vapor Even at high altitude CO 2 production is still there Water vaporizes in alveolar Leading to dilution of alv O 2 conc P AO2 = (P B – P CO2 – 47)

13-Feb-16High Atitude8 Effect of Breathing Pure O 2 Space that was occupied by nitrogen Is now occupied by oxygen This improves the % saturation of Hb with oxygen

13-Feb-16High Atitude9 Effect of Breathing Pure O 2 Breathing air Breathing 100% O 2 Altitude Barr.Press P AO2 mm Hg % satP AO2 mm Hg % sat 30, ,

13-Feb-16High Atitude10 Effect of Breathing Pure O 2 An aviator breathing oxygen in an un-pressurized aircraft –Can ascend to far higher altitudes than one not breathing pure oxygen e.g 4700ft as compared to 23000ft which is a Limit for an un-acclimatized individual who is also breathing normal air

13-Feb-16High Atitude11 Effects of Breathing Pure O 2 When individual is breathing pure oxygen P ao2 remains 90% Up to altitude of 39,000 ft Falls to 50% at 47,000 ft for unacclamatized falls to 50% at 23000ft

13-Feb-16High Atitude12 Effect of Acute Hypoxia Begin at about 12,000 ft –Drowness, lastitude –Mental & muscle fatigue –Headaches, nausea –Euphoria Above 18,000 ft –Muscular twitches & convulsions Above 23,000 –Coma, death

13-Feb-16High Atitude13 Acclimatization Respiratory Increase in pulmonary ventilation Hyperventilation Exposure to low P O2 stimulate chemoreceptors Stimulate respiration Leads to 65% increase in alveolar ventilation

13-Feb-16High Atitude14 Acclimatization An immediate compensation for high altitude Makes it possible for a person to ascend several thousand feet The  in alv ventilation decrease CO 2 – P CO2 &  pH both Inhibit respiration Tend to oppose stimulatory effect of hypoxia

13-Feb-16High Atitude15 Acclimatization After 2 to 5 days this inhibition fades away –Ventilation  3 to 7 times the normal level Active pumping of HCO 3 - from CSF Cause  pH in the CSF –Chemoreceptors are once more stimulated

13-Feb-16High Atitude16 Acclimatization Haemoglobin –Hypoxia causes –Release of erythropoietin –Increase production of RBC (polycythemia) Haematocrit increase –From 40 –45% to 60-65% –Hb increase from 15 gm% to 22 gm%

13-Feb-16High Atitude17 Acclimatization Total result is –Increase in circulating Hb of 50 to 90% more than normal Polycythemia –Increase viscosity However, these adaptive changes –Slow to develop –Takes about 2 – 3 weeks –Become fully developed after many months

13-Feb-16High Atitude18 Acclimatization O 2 transport  affinity of Hb for O 2 –Effect of increased 2,3 DPG (from 85 g/ml to 140 g/ml of blood) within 1 st 2 days Shifts O 2 - Hb dissociation curve to the right Diffusion capacity of lung for O 2 (21 ml/mm Hg/min) –Increases 3 times more

13-Feb-16High Atitude19 Acclimatization Increased capillary density – The number of capillaries – The distance between capillary & cells

13-Feb-16High Atitude20 Acclimatization Cardiac output –Increase by 20 – 30% immediately –But after few days Return back to normal May fall slightly below normal after few months There is increase in blood flow to –Muscles, heart, brain

13-Feb-16High Atitude21 Acclimatization Cellular level Enzyme adaptation to hypoxia –Increase in number of mitochondria –Increase in cellular oxidative enzymes

13-Feb-16High Atitude22 Failure to Acclimatize Chronic mountain sickness After remaining at high altitudes for a long time –One develops mountain sickness Red cell mass & haematocrit –Become exceptionally high Pulmonary arterial pressure –Become elevated more than during acclimatization

13-Feb-16High Atitude23 Failure of Acclimatization Right heart becomes greatly enlarged Peripheral arterial pressure falls Congestive heart failure develop

13-Feb-16High Atitude24 (II) Deep Sea Diving Relationship of sea depth to pressure A column of fresh water 34 ft (33 ft sea water) high –Exert the same pressure as the atmosphere above earth –Person 33 ft beneath ocean Exposed to pressure of 2 atmospheres

13-Feb-16High Atitude25 Effect of Depth on Pressure Sea depth (ft)Pressure (atmos) O

13-Feb-16High Atitude26 Effect of Depth on Volume of Gases Can be derived from gas laws P 1 V 1 = P 2 V 2 Example if –At sea level P 1 = 1 atmosphere, V 1 = 1 liter –At 33 ft below sea P 2 = 2 atmosphere, V 2 = (P 1 V 1 )/P 2 = ½ liter The air chambers of the divers will be compressed

13-Feb-16High Atitude27 Nitrogen Narcosis About 4/5 th of air is nitrogen At sea level pressure –Nitrogen has no bad effect to the body tissues However, at high pressures –Nitrogen can cause varying degree of narcosis

13-Feb-16High Atitude28 Nitrogen Narcosis When a diver remains beneath the sea –For about an hr breathing compressed air At 120 ft –Begins to have symptoms of mild narcosis Exhibit joviality Becomes careless

13-Feb-16High Atitude29 Nitrogen Narcosis At ft –Becomes drowsy At 200 – 250 ft –Loss of strength –Clumsy Beyond 250 ft –Diver usually becomes useless

13-Feb-16High Atitude30 Nitrogen Narcosis The narcosis is due to effects of dissolved N 2 –N 2 diffuses freely through fat –Into nervous tissue –Alters conduction of nerve impulse –Decreases excitability Brain function becomes impaired

13-Feb-16High Atitude31 Oxygen Toxicity Effect of extremely high P O2 When the P O2 increase above 100 mm Hg –Amount of dissolved O 2 in water increases The normal safe range of tissue P O2 –Is between 20 – 60 mm Hg At higher tissue P O2 –Oxygen poisoning occurs

13-Feb-16High Atitude32 Acute Oxygen Poisoning Due to extremely high tissue P O2 –Exposure to 4 atmospheres pressure of O 2 Partial pressure of about 3040 mm Hg will cause –Seizures (convulsion) within 30 to 60 min They occur without warning Likely to be lethal to the diver Other symptoms include –Nausea, muscle twitches, dizziness, disturbances of vision, irritability

13-Feb-16High Atitude33 Oxygen Poisoning Excessive intra cellular oxidation –Oxidizing free radicals Molecular O 2 –Active form of O 2 –Oxygen free radicals Super- oxide free radical (O 2 - ) Peroxide radicals (hydrogen peroxide)

13-Feb-16High Atitude34 Oxygen Poisoning At normal tissue P O2 –Small amount of free radicals are formed –Body contain enzymes that remove them Peroxidases, catalases, superoxide dismutase

13-Feb-16High Atitude35 Oxygen Poisoning Above a critical level of alveolar P O2 (>2 atmospheres) –Hb – O 2 buffering mechanism fail –Tissue P O2 rise tremendously –The amount of oxidizing free radicals 

13-Feb-16High Atitude36 Oxygen Poisoning Effects of oxidizing free radicals –Oxidize polyunsaturated fatty acids Essential components of cell membranes –Oxidize cellular enzymes Damage cellular metabolism Nervous tissue –Very susceptible –Lethal effect caused due to brain damage

13-Feb-16High Atitude37 Decompression of Diver When a diver breathes compressed air for a long time –Amount of nitrogen dissolve in body fluid increase The nitrogen dissolved in tissue –Not metabolized –Remains dissolve in tissue fluids

13-Feb-16High Atitude38 Nitrogen Dissolved in Body Fluid Depth in ft Amount in Liters

13-Feb-16High Atitude39 Decompression Sickness Also known as –Bends –Compressed air sickness –Caisson’s disease –Diver’s paralysis –Dysbarism

13-Feb-16High Atitude40 Decompression Sickness When a diver has been beneath the sea for a long time –Large amount of nitrogen Become dissolved in body fluids –If the diver suddenly comes to the surface Significant amount of nitrogen bubbles –Can develop in the body fluid These can cause some damages This is known as decompression sickness

13-Feb-16High Atitude41 Decompression Sickness Symptoms Most of the symptoms are caused by –Bubbles blocking blood vessels Air embolism The symptoms include –Pain in joints and limb muscles –Nervous symptoms Dizziness, paralysis, collapse

13-Feb-16High Atitude42 Decompression Sickness The chokes caused by –Massive numbers of bubbles plugging pulmonary capillaries Shortness of breath Severe pulmonary edema

13-Feb-16High Atitude43 Decompression Procedures However, –If the diver is brought to surface slowly –Dissolved N 2 is eliminated through the lung Rapidly enough to prevent decompression sickness –About 2/3 rd of the total nitrogen is liberated in 1 hr –And about 90% of the total in 6 hrs

13-Feb-16High Atitude44 Decompression Procedures There are special time schedules –For decompression –Depending on the depth and duration of the dive