Oxygen Delivery Devices
- Pressure-regulating devices
- • How air/oxygen blenders work
- • How Oxygen concentrators work
- -Delivery of other medical gases (heliox, carbon dioxide, nitric oxide)
- • Oxygen Conserving Devices
- a. Essentially regulators and reducing valve refers to the same thing, however a regulator combines a reducing valve with some type of flowmeter (bourdon guage)
- b. Reducing valves can either be preset by the manufacturer (50 psi) or adjustable
- i. An adjustable regulator can reduce the pressure down to levels selected by the operator
- ii. Adjustable regulators are not common
- c. Reducing valves can be single-stage or multi-stage
- i. Single stage reducing valves drop the pressure to its working level in one stage
- 1. Contains:
- a. Inlet port
- b. Pressure gauge
- c. High pressure chamber
- d. Pressure relief valve
- e. Outlet port
- f. Flexible diaphragm
- g. Ambient pressure chamber
- h. Spring
- i. Valve stem
- ii. Multistage reducing valves drop the pressure in two or more stages
- 1. Multistage are relatively uncommon in clinical practice because they are larger and more expensive, and provide a level of precision that is generally unnecessary
- 2. First stage reduces pressure to preset intermediate (500-700 psi) after which each of the following stages further reduces the pressure until 50 psi
How air/oxygen blenders work
- a) Air/oxygen blenders are connected to a high pressure (50 psi) air source and a high pressure oxygen source. The two pressures must be equal in order for the device to be accurate.
- b) When activated, both air and oxygen flow into the blender and then through dual pressure regulators that cause the pressure of the two gases to equalize.
- c) The gases then move toa precision proportioning valve. At this point, because the pressure of the two gases is equal, the concentration of oxygen (FiO2) is controlled by varying the size of the air and oxygen inlets. The blended gas then flows out of the outlet port to the delivery device, with a small amount of gas being shunted to an alarm.
How Oxygen concentrators work
- a) Modern stationary oxygen concentrators are electromechanical devices that generally operate from an AC power source, weight 30-50 pounds and have sound pressure levels of 39 to 55 decibels
- b) Oxygen concentrators separate the oxygen in the air from other gases using a chemical sieve gas-separating technology. The most common method of separating the gases employed in oxygen concentrations is known as pressure-swing absorption (PSA). Oxygen PSA systems pump air under specific pressure through a molecular sieve bed, normally composed of a ceramic ziolite that preferentially absorbs nitrogen molecules in the air, while allowing oxygen molecules to pass through the bed.
- c) The maximum output purity of modern oxygen concentrators is about 95%. Once separated, the output oxygen is typically collected in a small storage tank, pressurized, and delivered at the prescribed setting to the user.
- d) The most common are capable of delivering a range of continuous flow up to 5 L/min, with an oxygen purity of greater than or equal to 87%, although many modern devices exceed 93%
- • -Delivery of other medical gases (heliox, carbon dioxide, nitric oxide)\
- a. Heliox:
- i. Nonintubated patients may receive heliox therapy using a nonrebreathing oxygen mask.
- ii. Heliox can also be administered through a mechanical ventilator with caution.
- b. Carbon dioxide:
- i. Carbon dioxide/ oxygen mixtures (carbogen) have been used to terminate seizures, improve regional blood flow by dilating vessels in the brain of stroke victims, and encourage ophthalmic artery blood flow
- ii. Introducing small amounts of carbon dioxide into inspired gas before or after cardiac surgery on infants with hypoplastic left heart syndrome can help limit pulmonary blood flow by increasing pulmonary vascular resistance.
- c. Nitric Oxide:
- i. Inhaled nitric oxide has been used as a selective pulmonary vasodilator. It has been FDA approved for use in conjunction with ventilatory support where it is indicated for the treatment of term or nearterm neonates with hypoxic respiratory failure associated with clinical or echocardiographic evidence of pulmonary hypertension where it improves oxygenation and reduces the need for extracorporeal membrane oxygenation.
- ii. Delivery of nitric oxide is with the INOmax DSIR system from IKARIA. This device can be used with or without mechanical ventilation (i.e. noninvasive devices such as cannulas and nasal CPAP systems)
Oxygen Conserving Devices
- a) Pulse-dose oxygen-conserving devices were designed to conserve oxygen by delivering pulses of gas only during inspiration, thus avoiding the waste typically seen with a nasal cannula.
- b) Modern PDOCs are either electronically or pneumatically operated devices and typically deliver oxygen on demand.
- c) The patients demand is senses as the pressure drop caused by inspiratory flow past the sensor (typically nasal cannula). Once triggered, the device delivers a pre-determined flow of gas over a preset time interval, which produces a certain dose or bolus of oxygen.
Know ALL variable (Low Flow) devices and the Fi02 and Flow ranges for each
AARC CPG guidelines for 02 therapies
- Nasal Cannula [.24 -.44] 1-6 LPM (Liters per minute)
- Trans Tracheal Catheter
- Simple Mask [.35-.50] 5-10 LPM (Liters per minute)
- OxyMask [.24-.90] 1 to flush LPM (Liters per minute)
- Partial Rebreather Mask (PRBM) [.40-.70] 6-10 LPM
- Non Rebreather Mask (NRBM) [.60-.80] 10 LPM minimum
Know ALL fixed (High Flow) devices = High Flow Devices
- Air-Entrainment devices
- High flow nasal cannula
- Air entrainment nebulizer
- o The air-entrainment mask is a high flow oxygen delivery device that can provide a variety of precise FiO2s at flows that can greatly exceed that patients inspiratory demand.
- o Air-entrainment masks provide six to seven FiO2 settings:
- o Mask manufacturers typically publish recommended flowmeter settings for each FiO2.
- 4 L/min (0.24)
- 12-15 L/min (0.50)
High flow nasal cannula
- o Can provide rates up to 40 L/min through a nasal cannula wit heated humidification
- o The Vapotherm 2000i was capable of producing flows from 1 to 40 L/min at temperatures between 91.4*f and 109.4*F and a relative humidity of at least 95%
- o FiO2 was controlled by an air/oxygen blender located proximal to the device and adjustable between 0.21 to 1.0
Air entrainment nebulizer
- o Offer 6 to 8 FiO2 settings generally ranging from 0.28 to 1.0
- o The flow rates are adjusted so as to ensure a total flow that always exceeds inspiratory demand, often in actual practice the clinician will use a flowmeter setting of 15 L/min
YOU MUST KNOW HOW TO CALCULATE AIR: 02 RATIO FORMULAS:
• Either direct or scenario-based questions asking you to either calculate:
Air: 02 Ratio’s - Use which ever method works best for you –we will cover all
- Memorization of ratios
- Air:02 Ratio Formula: Example:
- o 100-40 60 3 = 3:1 Ratio
- 40 – 21 19 1
- “Magic Box”
- You will be asked to calculate either of the following
- Once you know the ratio, you can then:
- Determine the amount of air entrainment
- Total flow calculations (entrained + gas flow) = Total Flow
- o TOTAL FLOW = ratio combined