American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
Office Hypoxia
• COL Brian W. Smalley DO, MSPH, CPE
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Hypoxia • Stateof oxygen deficiency in the blood cells and tissues sufficient to cause impairment of function • 4 Types – Hypoxic – Hypemic – Stagnant – Histotoxic
E-1 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
Hypoxic Hypoxia TYPES OF HYPOXIA
Reduced pO2 in the lungs HYPOXIC (high altitude) (ALTITUDE) HISTOTOXIC (POISONING)
O2 O2
HYPEMIC O2 (BLOOD) O2 Red blood cells STAGNANT (POOLING) Body tissue
ALVEOLAR PO2 Oxyhemoglobin
AIR Dissociation Curve Po2 = 152 mm Hg Pco2 = 0.3 mm Hg
PH2O = 47 mmHg
Po2 = Pco2 = 103 mm 40 mm Hg ALVEOLI Hg increased temp, Pco2, or decreased pHshift curve to the right
Po2 = 40 mm Hg Po2 = 100 mm Hg
Pco2 = 46 mm Hg Pco2 = 40 mm Hg
ARTERIES VEINS LUNG CAPILLARIES
RIGHT LEFT HEART HEART
ALVEOLARAIR AT SEA LEVEL ALVEOLARAIR AT 10,000 FT
GAS mmHg GAS mmHg
N2 563 N2 376 O2 103 O2 61
CO2 40 CO2 35 H2O 47 H2O 47 TOTAL 760 TOTAL 522
O2Hb SAT = 87% O2Hb SAT = 98%
E-2 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
ALVEOLAR AIR AT 34,000 FT ALVEOLARAIR AT 25,000 FT
GAS mmHg GAS mmHg
N2 179 N2 90 O2 30 O2 26
CO2 27 CO2 24 H2O 47 H2O 47 TOTAL 283 TOTAL 187
O2Hb SAT = 55% O2Hb SAT = 42%
ALVEOLAR AIR AT 34,000 FT ON 100% OXYGEN OTHER CAUSES: • Hypoventilation GAS mmHg • Airway obstruction N2 0 • Reduction in gas exchangearea O2 100 • CO2 40 Impairment of gas exchange H2O 47 TOTAL 187
O2Hb SAT = 98%
Hypemic Hypoxia CAUSES
Inability of the • Reduced RBC count + blood to accept – blood donation + + – hemorrhage + oxygen in • Carbon Monoxide(CO) + adequate amounts + + + – + + incomplete combustion – + + forms carboxyhemoglobin + • Sulfa drugs/Ferricyanide – forms methemoglobin + + +
E-3 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
Stagnant Hypoxia CAUSES
Adequate • SYSTEMIC oxygen – Sustained high G Reduced – Sustained PPB blood – Shock Blood – Reduced cardiac output moving flow slowly • LOCAL – Body posture Red bloodcells – Hyperventilation not replenishing – Emboli tissueneeds – Extreme temperatures fastenough
Histotoxic Hypoxia
Adequate Oxygen Inability of the cell to accept or use oxygen
Red blood cells retain oxygen
Poisoned tissue
HISTOTOXIC HYPOXIA REMEMBER:
• Inability of tissues to accept and/orutilize • Can occur at any altitude oxygen • Different types are additive • Causes: • Individual and daily variability – Carbon monoxide – Alcohol – Cyanide – Hydrogen sulfide
E-4 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day PHYSIOLOGICAL RESPONSES TO HYPOXIC Hypoxic Hypoxia HYPOXIA
Reduced pO2 in the lungs (high altitude) • RESPIRATORY
• CARDIOVASCULAR
Red blood cells
Body tissue
RESPIRATORY RESPONSETO HYPOXIARESPIRATORY HYPOXIA CARDIOVASCULAR RESPONSE TO HYPOXIA Decreased arterial PO2 • Increase in cardiac output (6-8 K Feet) – Increase in rate; no change in stroke volume Stimulateventilation (8-10K feet) • No change in mean arterial pressure – Decreased peripheral resistance Decrease PACO2 – Redistributionof blood flow
Less Reduction in PAO2
CARDIOVASCULARRESPONSE CEREBRAL CIRCULATIONCIRCULATIONCEREBRAL • Increased heart rate • Decreased peripheral resistance • Below 15,000 ft – Decrease PCO2 predominates • Redistribution of cardiac output – Reduced blood flow – increase coronary and cerebral • Above 16,000 ft – decrease renal and skin – Decreased PO2 predominates • Normally,no change in skeletal muscle – Increased blood flow resistance
E-5 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day SYMPTOMS SYMPTOMS (subjective ) (objective)
apprehension headache hyperventilation euphoria hot/cold flashes cyanosis tingling nausea poor judgment dizziness numbness mental confusion blurred vision belligerence loss of musclecoordination tunnel vision fatigue unconsciousness
STAGES OF HYPOXIA STAGES OF HYPOXIA
• INDIFFERENT • COMPENSATORY • DISTURBANCE • CRITICAL
Indifferent Stage Compensatory Stage
• Altitudes: Sea Level - 10,000 feet • Altitudes: 10,000 - 15,000 feet
• Symptoms: decreasein night vision @ 4000 • Symptoms: impaired efficiency,drowsiness, feet poor judgment and decreased coordination – acuity – color perception
E-6 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
Disturbance Stage Critical Stage
• Altitudes: 15,000 - 20,000 feet • Altitudes:20,000 feet • Symptoms: and above – Decreased memory, impaired judgment, decreased reliability, poor understanding • Signs: loss of consciousness, – Personality: happy drunk versus the mean drunk convulsions and – Blurred vision, increased sense of touch & pain, death impaired hearing – Poor coordination, erratic flight control, slurred speech, illegible handwriting WARNING! When hemoglobin saturation fallsbelow65% serious cellular dysfunctionoccurs; and if prolonged, can causedeath!
TUC TUC (timeof useful consciousness) Altitude TUC
• The timefrom an interruption of an FL430&up 9-12sec FL400 15-20sec adequateoxygen supply to the time useful FL350 30-60sec function is lost. FL300 1-2min FL280 2-3min FL250 3-5min FL180 20-30min
Signs of Hypoxia (what you might see) Mental Disturbance
• Hyperventilation • Cyanosis • Mental confusion • Poorjudgment • Lack of musclecoordination
E-7 American Osteopathic College of Occupational and Preventive Medicine OMED 2013, Mandalay Bay Convention Center, Las Vegas Tuesday, October 1, 2013, Aerospace Medicine Day
Performance Disturbance Handwriting at 25K
Time off Oxygen
1 minute
2 minutes
3 minutes
4 minutes
5 minutes
6 minutes
Backonoxygen
CAUTION! Failureto recognizeyoursignsand symptomsbythe disturbance stage may result in an aircraft mishap
Factors Influencing Hypoxia and TUC Hypoxia • Prevention – • Altitude (cabin) Limit time at altitude • Rate of Ascent – Know your • Duration of Exposure symptoms – Pressurized • Fitness Level cabin – • Activity at Altitude Minimize self • imposed Treatment • Temperature stressors – Descend to a safe altitude – 100% O • Self-imposed stress – 100% O2 2
RECOVERY FROM HYPOXIAHYPOXIARECOVERY
• RAPID AND COMPLETE • O2 PARADOX QUESTIONS? – DECREASE IN PCO2 – INTRODUCTION OFHIGHFIO2
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