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Oxygen. Dr Mark B Smith. Oxygen. History Discovered by Carl Wilhelm Scheele, 1772 (German-Swedish) Joseph Priestley, 1774 (British) Named by Lavoisier, 1777 (French) Lost his head selling cheap tobacco. Oxygen. Atomic Number: 8 Atomic Weight: 15.9994

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oxygen

Oxygen

Dr Mark B Smith

oxygen1
Oxygen
  • History
    • Discovered by
      • Carl Wilhelm Scheele, 1772 (German-Swedish)
      • Joseph Priestley, 1774 (British)
    • Named by
      • Lavoisier, 1777 (French)
        • Lost his head selling cheap tobacco
oxygen2
Oxygen

Atomic Number: 8

Atomic Weight: 15.9994

Melting Point: 54.36 K (-218.79°C or -361.82°F)

Boiling Point: 90.20 K (-182.95°C or -297.31°F)

Density: 0.001429 grams per cubic centimeter

Phase at Room Temperature: Gas

Element Classification: Non-metal

Period Number: 2 

Group Number: 16

Group Name: Chalcogen

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Oxygen

The 10 Most Abundant Elements in the Universe

Source: Exploring Chemical Elements and their Compounds; David L. Heiserman, 1992

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Composition of the Earth's AtmosphereSource: Definition of the U.S. Standard Atmosphere (1976)CRC Handbook of Chemistry and Physics, 77th Edition

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Oxygen
  • Production
    • Photosynthesis
      • Where it has all come from
    • Heating mercuric oxide and nitrates
      • How it was discovered
    • Fractional distillation of air
      • Supply for medicine and industry
    • Colourless gas, pale blue liquid
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Oxygen
  • Daltons Law (John)
    • total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture
  • Significance
    • At fixed total pressure “adding” another gas reduces partial pressure of other gases
      • Water vapour
      • Carbon dioxide
oxygen under pressure
Oxygen: Under pressure

760mmHg = 101.325 kPa = 1 atmosphere

1 Pa = 1 Newton per square meter

1 torr = 1 mmHg = 1/760 atmosphere

Specific fluid density = 13.591 g/cm3

(Density of mercury at 0oC)

Specific gravity = 9.80665 m/s2

(Standard gravity)

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Oxygen

The purpose of the cardio-respiratory system is to extract oxygen from the atmosphere and deliver it to the mitochondria of cells.

Oxygen

exerts a partial pressure

determined by the prevailing environmental pressure

sea level atmospheric pressure is 760mmHg

oxygen makes up 21% (20.094% to be exact) air

oxygen exerts a partial pressure of 760 x 0.21 = 159mmHg

The oxygen cascade

as one moves down through the body to the cell, oxygen is diluted down, extracted or otherwise lost, so that at cellular level the PO2 may only be 3 or 4 mmHg.

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Oxygen

Oxygen Cascade

Oxygen moves down a stepwise series of partial pressure gradients from the inspired air to the body's cells and their mitochondria.

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Oxygen

Water vapour

humidifies inspired air

dilutes the amount of oxygen

reduces the partial pressure by the saturated vapour pressure (47mmHg)

effect on the PIO2 (the partial pressure of inspired oxygen)

recalculated as: (760 - 47) x 0.2094 = 149mmHg.

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Oxygen

Carbon dioxide

alveolar carbon dioxide, the PACO2

is usually the same as the PaCO2

measured by a blood gas analyzer

alveolar partial pressure of oxygen PAO2 calculated from the following equation: PAO2 = PIO2 – PaCO2/R

R is the respiratory quotient

represents the amount of carbon dioxide excreted for the amount of oxygen utilized

depends on the carbon content of food (carbohydrates high, fat low)

let us assume that the respiratory quotient is 0.8

PAO2 will then be 149 – (40/0.8) = 100mmHg

More Carbon dioxide means less Oxygen

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Oxygen

The next step

alveolus to artery

significant gradient, usually 5 –10 mmHg

small ventilation perfusion abnormalities

the diffusion gradient

physiologic shunt (from the bronchial arteries).

PaO2 = 90mmHg

Oxygen only moves through tissues dissolved in water

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Oxygen

Oxygen transport

arterial tree

minimal extraction

progressively extracted through the capillary network

interstitial space

return via venous system

partial pressure of oxygen in mixed venous blood, PVO2, is approximately 47mmHg.

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Oxygen

Oxygen cascade interference

At 19,000 feet (just above base camp at Mount Everest, the barometric pressure is half that at sea level, and thus, even though the FiO2 is 21%, the PIO2 is only 70mmHg, half that at sea level

Increased barometric pressure such as in hyperbaric chambers, the PIO2 will actually be higher

More oxygen…but dissolved not on haemoglobin

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Oxygen

Four factors influence transmission of oxygen from the alveoli to the capillaries

Ventilation perfusion mismatch

Pneumonia, pulmonary embolism

Right to left shunt

ASD, VSD

Diffusion defects

Pulmonary fibrosis, pulmonary oedema, COPD

Cardiac output

Pump failure, Exercise

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Oxygen

The amount of oxygen in the bloodstream is determined by;

serum haemoglobin level

percentage of this haemoglobin saturated with oxygen

cardiac output

the amount of oxygen dissolved (see below).

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Oxygen

How much oxygen is in the blood?

The amount of oxygen in the blood is calculated using the formula: [1.34 x Hb x (SaO2/100)] + 0.003 x PO2 = 20.8ml per 100ml blood

emergency mobile medical unit training weekend
EMERGENCY MOBILE MEDICAL UNIT Training Weekend

HYPOVENTILATION

  • A RISE IN PaCO2 CAUSES A FALL IN PaO2

THIS IS THE BASIS OF THE ALVEOLAR GAS EQUATION

PaO2 = FiO2(Pb-PaH2O)-PaCO2/0.8

emergency mobile medical unit training weekend1
EMERGENCY MOBILE MEDICAL UNIT Training Weekend
  • TREATMENT
    • OXYGEN TO OBTAIN SaO2>90%
  • IF THE PATIENT BECOMES TIRED THE PaCO2 MAY RISE
  • IF RISING PaCO2 OR DROWSY PROVIDE ASSISTED VENTILATION
emergency mobile medical unit training weekend2
EMERGENCY MOBILE MEDICAL UNIT Training Weekend

HIGH CONCENTRATIONS OF INSPIRED OXYGEN DO NOT DEPRESS VENTILATION IN PATIENTS WITH ACUTE RESPIRATORY FAILURE

emergency mobile medical unit training weekend3
EMERGENCY MOBILE MEDICAL UNIT Training Weekend
  • OXYGEN THERAPY ON GENERAL WARDS MUST BE PRESCRIBED
      • TYPE OF OXYGEN DELIVERY SYSTEM
      • FLOW RATE OF OXYGEN (OR %)
      • DURATION OF THERAPY
      • MONITORING TO BE UNDERTAKEN

Oxygen is a drug

emergency mobile medical unit training weekend4
EMERGENCY MOBILE MEDICAL UNIT Training Weekend

OXYGEN DELIVERY SYSTEMS

  • VARIABLE PERFORMANCE
  • FIXED PERFORMANCE
variable performance systems
VARIABLE PERFORMANCE SYSTEMS

NASAL CANNULA

  • 24-40% DEPENDING ON FLOW RATE
  • INSPIRED CONCENTRATION VARY BETWEEN BREATHS
  • DEPENDS UPON RATE AND DEPTH
  • MAXIMUM FLOW RATE APPROX 4 l/min
variable performance systems1
VARIABLE PERFORMANCE SYSTEMS

SIMPLE FACE MASK

  • MASK INCREASES RESERVOIR
  • MINIMAL FLOW RATE APPROX 4 l/min
  • NO INCREASED INSPIRED OXYGEN ABOVE 15 l/min
  • INSPIRED OXYGEN OF UP TO 60%
variable performance systems2
VARIABLE PERFORMANCE SYSTEMS

PARTIAL REBREATHING MASKS

  • FACEMASK AND RESERVOIR BAG
  • INSPIRED OXYGEN >60%
  • FLOW RATES OF APPROX 15 l/min REQUIRED
fixed performance systems
FIXED PERFORMANCE SYSTEMS

VENTURI MASK

  • ENTRAINS AIR
  • HIGH FLOW MAINTAINS HIGH INSPIRED OXYGEN CONCENTRAION THROUGHOUT RESPIRATORY CYCLE
  • COLOUR CODED VENTURI HEADS
fixed performance systems1
FIXED PERFORMANCE SYSTEMS

ANAESTHETIC MACHINE

  • Open system
    • Magill Circuit
    • Bains system
    • Maplesons C
  • Closed system
    • Circle
inspired oxygen v tissue oxygen
Inspired Oxygen v Tissue Oxygen
  • Inspired oxygen greater than alveolar oxygen
    • Oxygen cascade
        • Water vapour
        • Carbon dioxide
  • Normal and pathological physiological effects
    • Oxygen cascade, continued
        • Intrapulmonary ventilation/perfusion mis-match
        • Cardiac shunts
        • Arterial oxygen loss
        • Oxygen diffusion in water solution
emergency mobile medical unit training weekend5
EMERGENCY MOBILE MEDICAL UNIT Training Weekend

SUMMARY

ALL CRITICALLY ILL PATIENTS REQUIRE OXYGEN

Oxygen cascade occurs regardless

Maximise inspired Oxygen

MONITOR