It is the bread and butter of the anesthesia specialist. We have to learn so much about the things that go into the delivery of the oxygen from the sources to the patients, their set up, their construct, things that can go wrong and troubleshooting the, quality check and maintenance. I have summarized it all in this presentation.
2. Discussion points
◦ Oxygen main supply
◦ Nasal Cannula
◦ Facemask
◦ Venturi Mask
◦ High flow nasal cannula
3. Main Supply
◦ Vacuum insulated evaporator
◦ Oxygen is kept between –160 and –180 Celsius at 7
bar
4. Main supply
◦ Cylinder manifolds
◦ Size J or L cylinders are connected to manifold.
Cylinders are arranged in two groups.
5. Main supply
◦ Medical Gas cylinders
◦ Size E cylinders are used as back up to anesthesia
machine main supply and also during
transportation.
6. Oxygen concentrator
◦ Nitrogen and vapors are removed from room air to get 95% oxygen and 5% argon.
◦ USES
◦ Main supply in remote areas
◦ Back up to main supply
7. How they work
• Zeolite columns
• Air is passed through these columns
• Nitrogen and vapors are absorbed leaving
oxygen and argon
8. ◦ Advantages
◦ Cheap and reliable
◦ Reduce the need for commercial devices
◦ Disadvantages
◦ In low flow anesthesia in circle system, argon accumulates to produce a hypoxic mixture.
◦ System will stop producing oxygen if the power fails.
◦ Max flow is 10 L/min
◦ Max Fio2 is 0.95
9. Delivery of supplemental oxygen
◦ Hospital patients have increased oxygen demand.
◦ MV is 6 L/min but it can't be achieved easily due to high flow rates that peak at 60 l/min.
◦ High flows cause air entrainment
◦ Reservoir bags
◦ To increase Fio2, oxygen is collected in the reservoir bags during expiration. Hence during next inspiration,
concentrated oxygen will be drawn from the reservoir bag.
◦ Fixed performance Devices
◦ These deliver high fixed Fio2 by matching the peak inspiratory flow of the patient.
◦ Never deliver more than the specified Fio2
10. Nasal Cannula
◦ Overview
◦ Variable performance device
◦ Uses
◦ In low flow oxygen requirements
◦ How it works
◦ Gas flows of 1-4 l/min
◦ Nasopharynx acts as a oxygen reservoir
◦ Mouth breathing produces same or greater benefit
than nasal breathing
11. ◦ Advantages
◦ Simple and cheap
◦ Patients can speak and eat
◦ Good patient compliance
◦ Disadvantages
◦ Variable Fio2
◦ Drying of nasal mucosa
12. Variable
performance masks
◦ Overview
◦ Most common
◦ Modifications include, reservoir mask and
tracheostomy mask
◦ Uses
◦ Where precise Fio2 not important
◦ Reservoir mask used in emergency situation when high
Fio2 delivery is required.
◦ How it works
◦ Has holes on the side to allow expiration and
entrainment of air during inspiration.
◦ Oxygen flow of upto 15 l/min can be used
13. Reservoir mask
◦ Oxygen is collected in reservoir
◦ Oxygen is delivered via flap to the mask
◦ Mask has holes which are also covered flaps to reduce air entrainment during inspiration
◦ Entrainment still occurs from around the mask since it isn't sealed.
◦ Delivered Fio2 varies from 0.6-o.8
14. ◦ Advantages
◦ Simple, cheap and readily available
◦ Easy to vary delivered Fio2
◦ Reservoir bags are simplest means of delivering high Fio2
◦ Disadvantages
◦ Precise Fio2 is unknown
◦ Not suitable for calculations
◦ Rebreathing of CO2 from mask may occur
15. Venturi
Mask
◦ Overview
◦ Fixed performance devices that utilize venturi effect to deliver a precise
concentration of oxygen
◦ Uses
◦ Where specific Fio2 needs to be delivered
◦ Interpretation of ABGs in Fio2 context
◦ A 24% Venturi can be relied not to deliver more than 24%
16. How it works
◦ Venturi device connects at one end to face mask and at the other
end to oxygen source.
◦ It has a constriction. When oxygen flows through it, its speed
increases and pressure decreases.
◦ When the device is opened to air, decrease in pressure entrains
air and dilutes the oxygen.
◦ Flow delivered to the patient is the sum of flow set and the air
entrained.
◦ Total flow must be more than peak inspiratory flow of patient to
deliver accurate Fio2.
◦ If rate is more than 30/min, oxygen flow should be increased
than the flow printed on the device.
◦ Any flow higher than the specified minimum flow delivers the
fixed Fio2.
17. ◦ Advantages
◦ Simple and light weight
◦ Delivers a specific Fio2
◦ Patients respiratory pattern and rate doesn't effect delivered Fio2
◦ Disadvantages
◦ Risk of hypoxia by under-delivery
◦ High flows can lead to dry airways
◦ Less accurate at higher inspired concentration of oxygen
◦ Humidifiers cause water droplets to occlude the oxygen inlet
18. Nasal High Flow
◦ Overview
◦ Used in critical care
◦ High flows of 60l/min can be delivered.
◦ Warm and humidified oxygen or air mixtures can
be delivered.
◦ Uses
◦ Post-surgical
◦ Critical care
◦ Patients requiring low CPAP
19. ◦ How it works
◦ Oxygen or air mixtures are warmed and humidified
◦ High flows of up to 60 L/min can be delivered
◦ CPAP of up to 5cmH2O can be delivered.
◦ Advantages
◦ Better tolerated than FM in some patients
◦ Fixed FiO2 of up to 100% can be delivered in critical situations
◦ Gas is warmed and humidified
◦ Low CPAP is applied
◦ Disadvantages
◦ Expensive
◦ Not available in all hospitals
◦ Large scale clinical trials are still awaited
20. If this fails:
◦ CPAP
◦ BiPAP
◦ Tracheal intubation and mechanical ventilation
