Office. Hypoxia. Or this. Or even this. Hypoxia E-1. COL Brian W. Smalley DO, MSPH, CPE

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1 Hypoxia Office COL Brian W. Smalley DO, MSPH, CPE Or this Or even this Hypoxia State of oxygen deficiency in the blood cells and tissues sufficient to cause impairment of function 4 Types Hypoxic Hypemic Stagnant Histotoxic E-1

2 TYPES OF HYPOXIA Hypoxic Hypoxia HYPOXIC (ALTITUDE) HISTOTOXIC (POISONING) Reduced po 2 in the lungs (high altitude) O2 O2 HYPEMIC O2 (BLOOD) O2 STAGNANT (POOLING) Body tissue Red blood cells ALVEOLAR PO2 AIR Po2 = 152 mm Hg Pco2 = 0.3 mm Hg Oxyhemoglobin Dissociation Curve Po2 = 103 mm Hg P H2O = 47 Pco2 = 40 mm Hg ALVEOLI increasedtemp,pco2,or decreasedphshift curve to the right ARTERIES Po2 = 40 mm Hg Pco2 = 46 mm Hg LUNGCAPILLARIES Po2 = 100 mm Hg Pco2 = 40 mm Hg VEINS RIGHT HEART LEFT HEART ALVEOLAR AIR AT SEA LEVEL ALVEOLAR AIR AT 10,000 FT N O CO 2 40 TOTAL 760 N O 2 61 CO 2 35 TOTAL 522 O 2 Hb SAT = 98% O 2 Hb SAT = 87% E-2

3 ALVEOLAR AIR AT 25,000 FT ALVEOLAR AIR AT 34,000 FT N O 2 30 CO 2 27 TOTAL 283 N 2 90 O 2 26 CO 2 24 TOTAL 187 O 2 Hb SAT = 55% O 2 Hb SAT = 42% ALVEOLAR AIR AT 34,000 FT ON 100% OXYGEN N 2 0 O CO 2 40 TOTAL 187 OTHER CAUSES: Hypoventilation Airway obstruction Reduction in gas exchange area Impairment of gas exchange O 2 Hb SAT = 98% Hypemic Hypoxia Inability of the blood to accept oxygen in adequate amounts Reduced RBC count CAUSES blood donation hemorrhage Carbon Monoxide (CO) incomplete combustion forms carboxyhemoglobin Sulfa drugs/ferricyanide forms methemoglobin E-3

Adequate oxygen Blood moving slowly Stagnant Hypoxia Reduced blood flow Red blood cells not replenishing tissue needs fast enough CAUSES SYSTEMIC Sustained high G Sustained PPB Shock Reduced cardiac

4 Adequate oxygen Blood moving slowly Stagnant Hypoxia Reduced blood flow Red blood cells not replenishing tissue needs fast enough CAUSES SYSTEMIC Sustained high G Sustained PPB Shock Reduced cardiac output LOCAL Body posture Hyperventilation Emboli Extreme temperatures Histotoxic Hypoxia Adequate Oxygen Inability of the cell to accept or use oxygen Red blood cells retain oxygen Poisoned tissue HISTOTOXIC HYPOXIA Inability of tissues to accept and/or utilize oxygen Causes: Carbon monoxide Alcohol Cyanide Hydrogen sulfide REMEMBER: Can occur at any altitude Different types are additive Individual and daily variability E-4

Hypoxic Hypoxia Reduced po 2 in the lungs (high altitude) PHYSIOLOGICAL RESPONSES TO HYPOXIC HYPOXIA RESPIRATORY CARDIOVASCULAR Red blood cells Body tissue RESPIRATORY RESPONSE TO HYPOXIA Decreased

5 Hypoxic Hypoxia Reduced po 2 in the lungs (high altitude) PHYSIOLOGICAL RESPONSES TO HYPOXIC HYPOXIA RESPIRATORY CARDIOVASCULAR Red blood cells Body tissue RESPIRATORY RESPONSE TO HYPOXIA Decreased arterial PO2 Stimulate ventilation (8-10K feet) Decrease PACO2 CARDIOVASCULAR RESPONSE TO HYPOXIA Increase in cardiac output (6-8 K Feet) Increase in rate; no change in stroke volume No change in mean arterial pressure Decreased peripheral resistance Redistribution of blood flow Less Reduction in PAO2 CEREBRAL CIRCULATION Below 15,000 ft Decrease PCO2 predominates Reduced blood flow Above 16,000 ft Decreased PO2 predominates Increased blood flow CARDIOVASCULAR RESPONSE Increased heart rate Decreased peripheral resistance Redistribution of cardiac output increase coronary and cerebral decrease renal and skin Normally, no change in skeletal muscle resistance E-5

SYMPTOMS (subjective ) SYMPTOMS (objective) apprehension euphoria tingling dizziness blurred vision tunnel vision headache hot/cold flashes nausea numbness belligerence fatigue hyperventilation

6 SYMPTOMS (subjective ) SYMPTOMS (objective) apprehension euphoria tingling dizziness blurred vision tunnel vision headache hot/cold flashes nausea numbness belligerence fatigue hyperventilation cyanosis poor judgment mental confusion loss of muscle coordination unconsciousness STAGES OF HYPOXIA STAGES OF HYPOXIA INDIFFERENT COMPENSATORY DISTURBANCE CRITICAL Indifferent Stage Altitudes: Sea Level - 10,000 feet Symptoms: decrease in night 4000 feet acuity color perception Compensatory Stage Altitudes: 10,000-15,000 feet Symptoms: impaired efficiency, drowsiness, poor judgment and decreased coordination E-6

Disturbance Stage Altitudes: 15,000-20,000 feet Symptoms: Decreased memory, impaired judgment, decreased reliability, poor understanding Personality: happy drunk versus the mean drunk Blurred vision,

consciousness, convulsions and death WARNING! When hemoglobin saturation fallsbelow 65% serious cellulardysfunctionoccurs; andif prolonged, cancausedeath!

7 Disturbance Stage Altitudes: 15,000-20,000 feet Symptoms: Decreased memory, impaired judgment, decreased reliability, poor understanding Personality: happy drunk versus the mean drunk Blurred vision, increased sense of touch & pain, impaired hearing Poor coordination, erratic flight control, slurred speech, illegible handwriting Critical Stage Altitudes: 20,000 feet and above Signs: loss of consciousness, convulsions and death WARNING! When hemoglobin saturation fallsbelow 65% serious cellulardysfunctionoccurs; andif prolonged, cancausedeath! TUC (time of useful consciousness) Altitude TUC TUC The time from an interruption of an adequate oxygen supply to the time useful function is lost. FL 430 & up FL 400 FL 350 FL 300 FL 280 FL 250 FL sec sec sec 1-2 min 2-3 min 3-5 min min Signs of Hypoxia (what you might see) Mental Disturbance Hyperventilation Cyanosis Mental confusion Poor judgment Lack of muscle coordination E-7

Performance Disturbance Handwriting at 25K Time offoxygen 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 6

Failureto recognizeyoursignsand symptomsby the disturbancestagemay result in an aircraft mishap Altitude

Altitude Temperature Self-imposed stress Prevention Limit time at altitude Know your symptoms Pressurized cabin

8 Performance Disturbance Handwriting at 25K Time offoxygen 1 minute 2 minutes 3 minutes 4 minutes 5 minutes 6 minutes Backon oxygen CAUTION! Failureto recognizeyoursignsand symptomsby the disturbancestagemay result in an aircraft mishap Altitude (cabin) Rate of Ascent Factors Influencing Hypoxia and TUC Duration of Exposure Fitness Level Activity at Altitude Temperature Self-imposed stress Prevention Limit time at altitude Know your symptoms Pressurized cabin Minimize self imposed stressors 100% O 2 Hypoxia Treatment Descend to a safe altitude 100% O 2 RECOVERY FROM HYPOXIA RAPID AND COMPLETE O2 PARADOX DECREASE IN PCO2 INTRODUCTION OF HIGH FIO2 QUESTIONS? E-8

American College of Occupational and Preventive Medicine 2011 Annual Meeting, Orlando, Florida, November 2, 2011

American College of Occupational and Preventive Medicine 2011 Annual Meeting, Orlando, Florida, November 2, 2011 Administrative Information Risk Assessment: Low AEROSPACE/ OCCUPATIONAL MEDICINE BAROMETRIC CONCERNS Dr. John Campbell, MFS Environmental Considerations: None Safety Considerations: None Evaluation: 50