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Getting High. John P. Hunt LSU New Orleans Department of Surgery. Which person could have this blood gas? 7.65/14/35/15/71%. Scuba diver on his third 100 ft dive of the day A marathon runner during a race A mountain climber at 22,000 ft A COPD patient in respiratory distress.

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getting high

Getting High

John P. Hunt

LSU New Orleans

Department of Surgery

which person could have this blood gas 7 65 14 35 15 71
Which person could have this blood gas?7.65/14/35/15/71%
  • Scuba diver on his third 100 ft dive of the day
  • A marathon runner during a race
  • A mountain climber at 22,000 ft
  • A COPD patient in respiratory distress

American Board of Surgery, written exam, 1995

oxygen delivery from start to finish changes at altitude as a model

Oxygen Delivery –From Start to Finish: Changes at Altitude as a Model

John P. Hunt

LSU New Orleans

Department of Surgery

objectives
Objectives
  • Historical Perspectives
  • Environmental and physiological changes
  • Symptoms
  • Effects on DO2
  • Prevention
  • Therapy
historical perspectives
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

historical perspectives1
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

historical perspectives2
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

incidence
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)

high altitude cerebral edema hace
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
acute mountain sickness ams
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
high altitude pulmonary edema hape
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
temperature at altitude
Temperature at Altitude

Temperature (F)

Altitude (ft)

oxygen availability at altitude
Oxygen Availability at Altitude

Partial Pressure of O2 (mm torr)

Altitude (meters)

oxygen delivery
Oxygen Delivery

DO2= C.O. x 10 x

[(Hgb x SaO2 x 1.34) + (PO2 x 0.0031)]

oxygen delivery may be calculated as a function of
Oxygen Delivery may be calculated as a function of?
  • C.O., O2 saturation, mvO2 saturation
  • C.O., mvO2 extraction, mvO2 saturation
  • C.O., mvO2 saturation, Hgb
  • C.O., Hgb, O2 saturation
  • Difference between mvO2 saturation O2 saturation and C.O.
acute hypoxia produces
Acute Hypoxia Produces?
  • Increased pulmonary vascular resistance
  • Increased pulmonary blood flow
  • Increased total blood volume
  • Decreased epinephrine
  • Increased splanchnic perfusion
comparative oxygen tension
Comparative Oxygen Tension

Ventilation

Sea Level

Partial Pressure O2

Altitude

Level

how does ventilation improve oxygenation
How does Ventilation Improve Oxygenation?
  • Classic Ventilator Management dictates

-M.V. – PCO2

-FiO2 – PO2

alveolar gas equation
Alveolar Gas Equation

PAO2= (PB – PH2O)FIO2– PaCO2/RQ

comparative oxygen tension1
Comparative Oxygen Tension

V/Q Mismatch

Sea Level

Partial Pressure O2

Altitude

Level

v q mismatch
V/Q Mismatch
  • Dead space
  • Shunt
  • Diffusion
calculation of shunt
Calculation of Shunt

QS/QT= (CC02 – Ca02)/(CC02 – Cv02)

  • Understand the concept
lung volumes
Lung Volumes
  • Pursed-lips technique
v q mismatch and diffusion
V/Q Mismatch and Diffusion

Diffusion

% Total A-a P O2

V/Q Mismatch

Altitude (M)

Wagner PD et al J Appl Physiol 1987;63:2348

slide27

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?

  • Increase minute ventilation
  • Decrease minute ventilation
  • Increase functional residual capacity
  • Increase compliance
  • Decrease the I:E ratio
the primary mechanism by which peep improves oxygenation is
The primary mechanism by which PEEP improves oxygenation is?
  • Decreased air-flow resistance
  • Increased functional residual capacity
  • Increased forced vital capacity
  • Decreased interstitial lung water
  • Decreased ratio of dead space to total volume
comparative oxygen tension2
Comparative Oxygen Tension

Circulation & Extraction

Sea Level

Partial Pressure O2

Altitude

Level

hemoglobin
Hemoglobin
  • 33% Increase in Hgb
  • Secondary to significant increases in erythropoetin
  • Chronic exposure typically yields Hct in the 60 range
cardiac output
Cardiac Output
  • Preload
  • Contractility
  • Afterload
cardiac output1
Cardiac Output
  • Increase in SV
  • No changes in afterload
  • Preload sensitive DO2
starling mechanism
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

starlings law states that cardiac contractility increases when
Starlings Law states that cardiac contractility increases when?
  • SVR Increases
  • SV Increases
  • LVSW Decreases
  • EDV Increases
  • SV Increases and SVR Increases
hemoglobin oxygen dissociation
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

O2 Sat

PaO2

a shift in the oxygen hemoglobin dissociation curve to the right is characteristic of
A Shift in the Oxygen-Hemoglobin-Dissociation curve to the right is characteristic of?
  • Hyperventilation
  • Increased carboxy-hemoglobin
  • Decreased affinity of hemoglobin for oxygen
  • Decreased A-V O2 difference
  • May be caused by hypothermia
extraction ratio
Extraction Ratio
  • VO2/DO2
  • VO2 = Q x (Ca02 – Cv02)

= Q x 1.34 x Hgb (Sa02 – MV02)

  • Mountaineers have a maximized extraction ratio
at rest mvo 2 saturation
At rest MvO2 Saturation?
  • Normally ranges between .48-.55
  • Increases as O2 consumption increases
  • Increases as Hgb decreases
  • Increases as Cardiac Output increases
  • Decreases as Arterial oxygen saturation increases
therapy
Therapy
  • Descend
  • Bedrest
  • Supplemental oxygen
  • Gamow Bag
prevention
Prevention
  • Slow ascent
  • Climb high, sleep low
  • Acetazolamide
  • Nifedipine
nifedipine for hape
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

acetazolamide for ams
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

summary
Summary
  • Mountain Climbers optimize O2 delivery by

-A four-fold increase in ventilation

-Optimizing V/Q matching

-Increasing Hgb via erythropoesis

-Optimizing the O2 Extraction Ratio

summary1
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
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