1. Getting High John P. Hunt LSU New Orleans Department of Surgery

2. Which person could have this blood gas? 7.65/14/35/15/71% 1)Scuba diver on his third 100 ft dive of the day 2)A marathon runner during a race 3)A mountain climber at 22,000 ft 4)A COPD patient in respiratory distress American Board of Surgery, written exam, 1995

3. Oxygen Delivery –From Start to Finish: Changes at Altitude as a Model John P. Hunt LSU New Orleans Department of Surgery

4. Objectives Historical Perspectives Environmental and physiological changes Symptoms Effects on DO 2 Prevention Therapy

5. Where it’s High

6. Historical Perspectives “Men’s bodies become feverish, they lose color and are attacked with headache and vomiting; the asses and cattle being in the same condition” Qian Han Shu, 30 BC

7. Historical Perspectives “I was quite out of breathe from the rarity of the air” DeSaussure 1787 “I feel funny and I don’t know why, excuse me while I kiss the sky” Hendrix 1969

8. Historical Perspectives “After we huddle over our ice axes, mouths agape, struggling for sufficient breath… I feel I no longer belong to myself and my eyesight. I am nothing more then a single narrow gasping lung” Messner 1978

9. Incidence 67% of mountaineers ascending Mount Rainier (14,405 ft) 53 % of trekkers in the Himalayas (13,900 ft) 12% of Colorado skiers (8,000 ft)

10. High Altitude Cerebral Edema (HACE) Less than 1% of all Mountain sickness Always above 12,000 Ft Symptoms: Severe headache, Ataxia, Loss of co-ordination, Diplopia, Confusion, Hallucinations, Death

11. Acute Mountain Sickness (AMS) Usually above 10,000 Ft Onset is 4-6 hours after exposure & Duration 3 Days Symptoms: Headache, Insomnia, Irritability, Fatique, Nausea/vomiting

12. High Altitude Pulmonary Edema (HAPE) Rarely below 8,000 Ft Onset is 1-3 days after exposure Symptoms: Dyspnea at rest, Pink frothy sputum, Rales, Cyanosis, mild temperature

13. Temperature at Altitude Altitude (ft) Temperature (  F)

14. Oxygen Availability at Altitude Partial Pressure of O 2 (mm torr) Altitude (meters)

15. Oxygen Delivery D O 2 = C.O. x 10 x [(Hgb x Sa O 2 x 1.34) + (P O 2 x 0.0031)]

17. Oxygen Delivery may be calculated as a function of? 1)C.O., O 2 saturation, mvO 2 saturation 2)C.O., mvO 2 extraction, mvO 2 saturation 3)C.O., mvO 2 saturation, Hgb 4)C.O., Hgb, O 2 saturation 5)Difference between mvO 2 saturation O 2 saturation and C.O.

18. Acute Hypoxia Produces? 1)Increased pulmonary vascular resistance 2)Increased pulmonary blood flow 3)Increased total blood volume 4)Decreased epinephrine 5)Increased splanchnic perfusion

19. Sea Level Altitude Level Comparative Oxygen Tension Partial Pressure O 2 Ventilation

20. How does Ventilation Improve Oxygenation? Classic Ventilator Management dictates -M.V. – P CO 2 -Fi O 2 – P O 2

21. Alveolar Gas Equation P A O 2 = (P B – P H 2 O )F I O 2 – P aC O 2 /RQ

22. Sea Level Altitude Level Comparative Oxygen Tension Partial Pressure O 2 V/Q Mismatch

23. Dead space Shunt Diffusion

24. Calculation of Shunt Q S /Q T = (C C 0 2 – C a 0 2 )/(C C 0 2 – C v 0 2 ) Understand the concept

25. Lung Volumes RV FRC ERV TV IC IRV Without PEEP RV FRC ERV TV IC IRV With PEEP Pursed-lips technique

26. Diffusion V/Q Mismatch Altitude (M) V/Q Mismatch and Diffusion % Total A-a P O 2 Wagner PD et al J Appl Physiol 1987;63:2348

27. 3 days following operation for a perforated ulcer a 68 y.o man requires intubation. Initial ABG on 100% shows 7.32/72/36. To improve oxygenation the ventilator should be adjusted to? 1)Increase minute ventilation 2)Decrease minute ventilation 3)Increase functional residual capacity 4)Increase compliance 5)Decrease the I:E ratio

28. The primary mechanism by which PEEP improves oxygenation is? 1)Decreased air-flow resistance 2)Increased functional residual capacity 3)Increased forced vital capacity 4)Decreased interstitial lung water 5)Decreased ratio of dead space to total volume

29. Sea Level Altitude Level Comparative Oxygen Tension Partial Pressure O 2 Circulation & Extraction

30. Hemoglobin 33% Increase in Hgb Secondary to significant increases in erythropoetin Chronic exposure typically yields Hct in the 60 range

31. Cardiac Output Preload Contractility Afterload

32. Cardiac Output Increase in SV No changes in afterload Preload sensitive DO 2

33. Starling Mechanism Dehydration and subsequent decrease in preload is the mountaineers worst enemy 80% of carried fuel is used to make water Cardiac Output EDV

34. Starlings Law states that cardiac contractility increases when? 1)SVR Increases 2)SV Increases 3)LVSW Decreases 4)EDV Increases 5)SV Increases and SVR Increases

35. Hemoglobin-Oxygen Dissociation Shifting the curve to the right decreases the affinity of hemoglobin for oxygen inducing off- loading -Increased temp -Decreased pH -Increased CO2 -Increased 2-3 DPG PaO2 O2 Sat

36. A Shift in the Oxygen- Hemoglobin-Dissociation curve to the right is characteristic of? 1)Hyperventilation 2)Increased carboxy-hemoglobin 3)Decreased affinity of hemoglobin for oxygen 4)Decreased A-V O 2 difference 5)May be caused by hypothermia

37. Extraction Ratio VO 2 /DO 2 VO 2 = Q x (C a 0 2 – C v 0 2 ) = Q x 1.34 x Hgb (S a 0 2 – M V 0 2 ) Mountaineers have a maximized extraction ratio

38. At rest MvO 2 Saturation? 1)Normally ranges between.48-.55 2)Increases as O 2 consumption increases 3)Increases as Hgb decreases 4)Increases as Cardiac Output increases 5)Decreases as Arterial oxygen saturation increases

39. Therapy Descend Bedrest Supplemental oxygen Gamow Bag

40. Prevention Slow ascent Climb high, sleep low Acetazolamide Nifedipine

41. Nifedipine For HAPE 21 volunteers with previous history of HAPE Ascended to 4559 M Nifedipine vs Placebo Pulmonary edema in 1 in 10 of treated group vs 7 of 11 in control group Reproduced by Oelz O. et al Bartsch P. et al NEJM 1996;325:1284

42. Acetazolamide For AMS 64 healthy volunteers ascending Mount Rainier 93.6% of treatment group and 75.8% of controls reached the summit 66.7% of controls and 17.2% of the treatment group developed AMS Reproduced by Grissom et al on Denali Larson EB. et al JAMA 1982;248:329

43. Summary Mountain Climbers optimize O 2 delivery by -A four-fold increase in ventilation -Optimizing V/Q matching -Increasing Hgb via erythropoesis -Optimizing the O 2 Extraction Ratio

44. Summary HACE, HAPE, AMS are different forms of Altitude sickness Judicious climbing practices and medical prophylaxis are warranted Descent is the best therapy for altitude sickness