Rhonda Contant, BScH, RRT Oxygen Therapy Rhonda Contant, BScH, RRT

Let’s Start with the Basics! How much O2 is in room air? How much O2 comes out of a flowmeter?

Oxygen Therapy O2 delivery systems: design and performance Three basic designs exist Low-flow systems Reservoir systems High-flow systems There are numerous oxygen modalities available to choose from when treating pts. Design and performance = Proper device selection requires knowledge of the general performance characteristics as well as the individual capabilities. O2 delivery devices are categorized by design – low flow, high flow and reservoir.

We need to answer 2 key questions… How much O2 can the system deliver? What is the FiO2 or FiO2 range of the device? Does the FiO2 vary or remain fixed with changing pt demands? Does everyone know what I mean when I say FiO2?? Fractional concentration of O2 = the concentration of O2 on inspiration Different devices can deliver different O2 concentrations, so we need to know what FiO2 we need or what range before we make our choice. Secondly, is it important to provide a fixed or variable FiO2?

Fixed or Variable FiO2? Depends on how much of the pt’s inspired gas the device delivers Fixed means the FiO2 stays the same Variable mean the FiO2 fluctuates.

Fixed or Variable FiO2? Fixed FiO2 The device is designed to deliver ALL the pt’s inspired gas  FiO2 is constant or fixed Fixed delivers ALL the pts inspired gas even under changing pt demands ie increased RR or Vt

Fixed or Variable FiO2? Variable FiO2 The device provides only SOME of the inspired gas The pt must draw the rest from the surrounding environment (room air) What happens if we mix O2 with room air? Dilutes the delivered O2  lowers FiO2 The result = variable FiO2 from breath to breath depending on pt demands

Low Flow Systems: Uses low flows (< 8 Lpm) They are variable systems therefore the pts demands will affect the FiO2 Keep in mind flow > 6Lpm are very drying (no humidity in O2, the humidity is removed when it is processed) and can lead to nasal dryness and bleeding. Factors that affect (decrease) FiO2 = Examples: increased RR, large Vt and open mouth breating

Low Flow Systems: Nasal cannula Delivers an FIO2 of 0.24 to 0.40 Used with flow rates of ¼ to 8 L/min FIO2 depends on how much room air the patient inhales in addition to the O2. Device is usually well tolerated. Humidifier should be used with flows > 4 Lpm Books say 8 Lpm, but we don’t recommend >6 Lpm unless there are extenuating circumstances

Nasal Prongs / Cannula Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

How to Estimate the FiO2 for Nasal Cannula: FiO2 = 21% + (4 x #Lpm) Example: What is the approximate FiO2 when the flow meter is set at 2 Lpm? FiO2 = 21% + ( 4 x Lpm) FiO2 = 21% + ( 4x 2) FiO2 = 29%

Reservoir Systems Incorporate a mechanism to gather and store O2 between pt breaths Pts draw from this reservoir when their inspiratory flows exceed the oxygen flow delivered by the device Instead of diluting with room air, they dilute with O2  results in a higher FiO2 Incorporates this mechanism into a low flow system. Normally with low flow systems the pt dilutes or draws in r/a to meet their needs. With reservoir systems, they breath in from the reservoir to make up the difference…if they still require more, then they draw in r/a diluting the FiO2.

Reservoir Systems Reservoir cannula Designed to conserve oxygen Nasal reservoir Pendant reservoir Can reduce oxygen use as much as 50% to 75% Humidification usually not needed Typically found in home care. Aesthetically not too pleasing. Need lower flows to achieve the same saturations b/c of less dilution with room air. B/c of low flows, don’t typically need humidification

Moustache Reservoir Cannula

Pendant Reservoir Cannula

Reservoir Systems Reservoir masks Most commonly used reservoir systems Three types Simple mask Partial rebreathing mask Nonrebreathing mask All masks themselves are a type of reservoir to store O2 b/c they gather and store O2 b/w pt breaths. Some systems incorporate another storing device ie. bag Inc.

Simple Mask Simple mask at 5-10 lpm  35-50% FiO2 Requires a minimum flow of 5 Lpm in order to FLUSH out the CO2 from exhalation. Provides a variable FiO2 b/c pt can still breath in though the ports if the volume in the mask does not meet their needs. FiO2 will depend on INPUT FLOW, MASK VOLUME, PT BREATHING PATTERN AND AIR LEAK AROUND THE MASK Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

Partial and Non - Rebreathers Left = Partial Rebreather Right = non Rebreather. Incorporates a 1 L reservoir bag attached to the O2 inlet that acts as a reservoir Non rebreather uses one way valves to further increase the FiO2. Partial rebreather has no valves. Partial rebreather – no valves, therefore on exhalation, some of the exhaled gas goes into the reservoir bag = approx the first third of the pts exhalation. This gas is coming from the pts anatomic deadspace (which has not undergone gas exchange), therefore is high in O2 and has essentially no CO2 and it mixes with gas coming from the flowmeter. The other 2/3 of exhalation get flushed out the ports on mask. (therefore rebreathing of CO2 is minimal) On inspiration, the pt breaths in the O2 from the mask and then draws from the bag. The result = moderate but variable FiO2 – 40 – 70% at flows of approx 10 - 15 Lpm (enough to keep the bag inflated) Non rebreather: - one one-way valve on mask and one on bag. Explain how they work. Inspiratory valve on bag, expiratory valve on mask Again, requires flows high enough to prevent the bag from collapsing during inspiration In theory can deliver 100%, but in reality can only deliver approx. 60-80% Why? B/c only one valve on mask portion to prevent suffocation in event that O2 becomes disconnected. This other port also allows for air dilution. As well may get leaks around the seal of the face. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

High Flow Systems Supply a given (or fixed) O2 concentration at a flow equaling or exceeding the patient’s peak inspiratory flow Use air-entrainment or blending system to mix air and oxygen at very specific ratios to determine a specific oxygen concentration Can ensure a fixed FIO2 These devices are designed to mix in specific ratios. Example a 1:1 ratio of Air to O2 will produce an FiO2 of 0.60 (60%) The higher the FiO2 the lower the total flow The lower the FiO2 the greater the total flow Why? B/c to get a lower FiO2 we have to mix more room air with it. Ex. 30% = 8 parts air and 1 part O2 = 9 total parts. Therefore, lower FiO2 are gaurenteed to have flows high enough to meet or exceed the pts demands. Higher FiO2 may not have flows great enough to meet the pts demands What happens if the total flow is not enough to meet the pts demands? They will dilute with room air.

Air Entrainment or Venti Mask You may hear this called a Venturi mask – this is incorrect! They do not apply the venturi principle. Provide a fixed FiO2 at lower ranges ie 24-50% at set flows of 3Lpm (0.24 – 0.31) and 6 Lpm (0.35-0.50) depending on setting. If a patients saturations do not improve on this system, increasing the flow is not the solution. They are specially designed to work at the designated flow rates, therefore we need to change modalities. Large volume nebulizers (Jet nebulizers) use this same principle but they provide humidity. Can’t exceed FiO2 of 0.50 (even though they say they go up to 100%) Why not? Again, because the output or total flow is not enough to meet the pts demands, therefore they will dilute with room air and actually decease the actual FiO2. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc.

High Flow Jet Nebs Misty Ox is a brand name. It can deliver fixed FiO2 at 0.60 – 0.96 when the flowmeter is set at minimun 40Lpm How is this possible? Crank it all the way open = approx. 45 Lpm will come out of the flowmeter.

Equipment for Aerosol Therapy Airway appliances Aerosol mask Face tent T-tube Tracheostomy mask All used with large-bore tubing These devices are connected to the large volume nebulizer or High flow nebulizers.

Equipment for Bland Aerosol Therapy Masks – traditional Facetent – facial burns, claustrophobic pts can sometimes benefit from there, pts with nasal packing for epistaxis. Trach mask – trachs

Equipment for Bland Aerosol Therapy T-piece is used with ETT.

How do we know what to use? Nasal Cannula Uses: Stable pts requiring low FiO2 Home care pts requiring long term O2 Advantages Adults, peds and infants Easy to apply Disposable, inexpensive Well tolerated Can eat with them in place

How do we know what to use? Nasal Cannula Disadvantages Easily dislodged High flows uncomfortable Can cause dryness and bleeding Variable FiO2s

How do we know what to use? Reservoir (NRBR) Uses Emergencies Unstable pts (MI) Acute hypoxemia Smoke inhalation / CO poisoning CHF

How do we know what to use? Reservoir (NRBR) Advantages High FiO2 Adults and peds Quick and easy to apply Disposable and inexpensive Disadvantages Uncomfortable Can’t eat with mask on Risk of aspiration if pt vomits Potential suffocation hazard

How do we know what to use? Venti mask Uses: Unstable pts requiring precise low FiO2 Pts with variable RR and Tidal Volume Advantages: Easy to apply Disposable and inexpensive Stable, precise FiO2 Disadvantages: Uncomfortable Can’t eat with mask on Noisy Risk of aspiration if pt vomits

How do we know what to use? Large Volume (Jet) Nebulizers Uses: Pts with artificial airways Pts with supraglottic swelling To help mobilize secretions Advantages: Provides humidification Provides fixed FiO2 Disadvantages: FiO2 varies with back pressure (ie condensation in tubing) Increased risk for infection

FYIs O2 is a prescribed drug For every connection there is a possibility for a leak Vasoline and O2 don’t mix  use a water based lubricant to treat nasal and lip dryness When in doubt, call RT, we are there to help!!

Questions?