Oxygen therapy 2014
What is the most important factor contributing to the oxygen carrying capacity of the blood?
hemoglobin
Accuracy of a pulse ox when saturation is greater than 90%
+/- 4
Accuracy of a pulse ox when saturation is less than 70%
+/- 6
Venturi masks determine the FIO2 that the patient receives by varying two aspects of the entrainment ports construction
1. The diameter of the outflow jets 2. The size of the entrainment port -Venturi windows
G cylinder- 5,269 L/ 2200 psig =_______`
2.41 L/psig
Air-oxygen blenders require a ______source of both oxygen and air, while utilizing an internal pressure balancing system to maintain equal air and oxygen pressures at a proportioning valve.
50 psig
A patient has a nasal cannula and needs to be transported on a stretcher. The E-size 02 cylinder will need to be laid flat under the stretcher. What flow meter would you recommend using?
A Bourdon flow meter is the only unit that will accurately indicate the flow when it is laid horizontally. The others will read accurately only in a vertical position.
If the physican order calls for a specific FIO2 what would the best choice?
A High flow system Venturi mask provides precise concentrations of 24-50% FIO2
What are the factors that determine whether an oxygen delivery device is a high flow or a low-flow devices?
A high flow delivery provides sufficient total flow to meet or exceed the patient's inspiratory flow rate. A low flow device does not provide all of the patient's inspiratory flow needs.
What can you add to help supplement any oxygen that may be leaking from a non rebreather mask that is on 12-15LPM.
A nasal cannula at 5-6 liter worn beneath the NRB
Explain the "Rule of Four" in estimating the FIO2 available with a nasal cannula.
A nasal cannula running at 5 LPM will deliver approximately 40% to the patient. To help you remember this, begin with room air (approx. 20%). For each liter of nasal 02 add 4% to this. 4L X 4% = 16% added to 20% = 36%.
Which oxygen delivery device(s) will provide a stable and predictable oxygen concentration to patients whose ventilatory patterns, respiratory rates and tidal volumes are normal?
A stable & predictable FIO2 may be delivered to patients via high flow devices operated so that the total flow provided by the device meets or exceeds the patient's inspiratory flow needs
Clinical objectives for the administration's first supplemental oxygen include
A) to prevent or correct arterial hypoxemia B) to decrease myocardial work load C) to decrease work of breathing
What 02 delivery device would you recommend for a patient who has a variable respiratory rate, I:E ratio, and Vt?
An air entrainment mask (Venturi mask) should provide enough flow of the prescribed 02 percentage at any patient rate, Vt,
A patient that has a continuing decreased tidal volume would obtain an FIO2 that is higher than normal expected if she were on which of the oxygen delivery devices
Any Low flow device The delivered FIO2 is dependent on the patients tidal volume
What is the oxygen:air entrainment ratio for a 50% Venturi system? What would the total flow of the system be if the oxygen flow rate is 15 lpm? Is the flow sufficient to meet the needs of a patient whose minute ventilation is 8 lpm?
Air entrainment factor for a 50% Venturi device is 1:1.6. With an oxygen flow of 15 lpm, the total flow is 15 X 2.6 or 39 lpm. Using the guess imitation that inspiratory flow is approximately equal to minute ventilation X 4, the described system would just meet the inspiratory flow needs of a patient whose minute ventilation is 8 lpm.
Describe the ideal type of oxygen flow meter for clinical use—include discussion of flow compensation.
Back pressure compensated flow meters provide accurate readings of delivered flow rates in spite of outlet obstructions.
Is the flow meter to use when a small compressed gas cylinder is being transported in a horizontal postion
Bourdon gauge
The simple 02 mask is a reservoir for not only incoming oxygen, but also exhaled ____ ______ It is important to use oxygen flow rates sufficient to "flush" out exhaled ____,
C02 (carbon dioxide). C02
Explain how administration of oxygen to a COPD patient with chronic CO2 retention may cause clinical problems?
CO2 retention in some COPD patients may be exacerbated by administration of oxygen.
Suspect Hugh concentrations in victims of closed space fires and heavy smokers Normal is 0.5-3% 5-10% in smokers
Carboxyhemoglobin
What oxygen percentage should not be exceeded in order to avoid oxygen toxicity?
FIO2 should be below 50%.
What should be done to correct the problem of water collecting in the delivery tube of a continuous aerosol delivered to a patient with an endotracheal tube who is receiving oxygen enrichment via a heated nebulizer?
Frequent draining of condensate is essential to ensure consistent delivery of a specific FIO2.
Must provide for the total inspiratory flow demand of the patient
High flow system
How can you estimate a patient's predicted PaO2?
If one considers that the FIO2 of atmospheric air is 0.21 and a healthy person's PaO2 is near 100 torr, a factor of 5 can be derived by dividing the PaO2 by the FIO2. Multiplying the delivered FIO2 by 5 will yield an approximate predicted PaO2.
Suppose a doctor orders a simple 02 mask at 2 lpm, what would be your response?
In this case the physician's orders as given are clearly not compatible with sound respiratory care practice and may be detrimental to the patient's well being.
A patient who has just returned from OR has a 40% Venturi mask in use operated at 2 lpm. The respiratory care practitioner discovers that the patient's inspiratory flow exceeds the output of the apparatus. What should the RCP do to correct the problem?
Increasing the oxygen flow rate will not change the FIO2, but will increase the total output of gas to the patient.
A patient with a tracheostomy is receiving continuous, heated bland aerosol therapy. When the delivered FIO2 is analyzed, it is found that although the air entrainment setting is 40%, the oxygen analyzer reads 60%. Describe some of the causes of this discrepancy.
Lack of frequent and regular calibration of the oxygen analyzers prior to use may result in inaccurate results.
Your patient is wearing a face tent because of recent facial surgery. It is set at 35% 02. The nurse moves the patient from an upright to a supine position in bed. What effect will this have on her respiratory status?
Lying supine may result in the Vt decreasing (due to restriction of the lungs expansion by the abdominal contents).
Iron atom in heme portion of hemoglobin exists in ferric state instead offerrous state; may appear in some patients after administration of some pharmacological agents
Methemoglobin
The nasal cannula is a low flow system and provides a number of advantages over oxygen administration devices that incorporate a mask
More comfortable than masks Affords the opportunity to eat while in use Appropriate to deliver high oxygen concentrations (45%)
Two patients are receiving oxygen via nasal cannula at 3 lpm. Patient A has a tidal volume of 300ml and a respiratory rate of 10 bpm. Patient B has a tidal volume of 500 ml and a respiratory rate of 14 bpm. Which patient will receive the higher FIO2?
Patient A's minute volume is lower than Patient B's. Proportionally more of Patient A's minute volume will be comprised of oxygen from the cannula, therefore his inspired concentration of oxygen will be higher than patient B's.
What specifications should be included by physicians in their orders for administration of oxygen to a hospitalized patient?
Physician's orders for O2 via low flow systems typically specify the device and the flow rate in lpm (cannulas, simple O2 masks)
While setting up a nasal cannula, you insert a flow meter into the oxygen outlet (with the needle valve closed). You notice that the float JUMPS up and then falls. What conclusion can be drawn from this action?
Pressure compensated Thorpe tube flow meters will demonstrate the described phenomenon when they are engaged in a high-pressure system, such as a quick connect outlet.
How is the adequacy of oxygenation assessed "non-invasively" ?
Pulse Oximetry
While setting up oxygen via a Venturi mask, you are unable to attach a flow meter with a quick connect to the wall oxygen outlet. What is the most likely cause of this problem?
Quick connect outlets are designed to connect to specific medical gas outlets. If a quick connect device fails to "seat" or properly connect to an oxygen outlet, it may be indexed for compressed air rather than oxygen.
How would you modify a non-rebreathing mask to make a partial rebreathing mask?
Remove the flaps
In non rebreathing mask and simple o2 mask the masks themselves act as a
Reservoirs
PH- 7.35 PaCO2- 60 torr PaO2- 60 torr HCO3- 32 mEq/l
Stable COPD patient
What effect will a build-up of water in an aerosol hose have on the FIO2 delivery of an aerosol mask?
The air entrainment devices work on Bernoulli's principle, which basically states that as the flow rate increases, the lateral pressure drops (becomes more negative) in the area of the air entrainment port (Venturi window).
When a patient who is receiving oxygen via non rebreathing mask inhales the reservoir bag on the mask does not deflate. What is the problem?
We know that the flow is NOT the problem because the reservoir bag is inflated. or excess humidity
What errors in operation of a Venturi mask are most likely to cause it to deliver an FIO2 higher than intended?
The most common error in the operation of a Venturi device that will result in a delivered FIO2 (FIO2) higher than intended is allowing the device to operate with an obstruction in its outflow tract
When a patient who is receiving oxygen via a non-rebreathing mask inhales, the reservoir bag on the mask does not deflate. Describe the most probable cause of this situation.
The most likely cause of this problem in a poor fit.
A patient is admitted to the emergency room with a chief complaint of shortness of breath. Arterial blood gases recorded at this time reveal the following: pH 7.35 PaCO2 60 torr PaO2 48 torr HCO3 38 mEq/L Which oxygen delivery device would you select to administer supplemental oxygen to this patient?
The safe approach would be to apply a 24% entrainment device and monitor the patient's oxyhemoglobin saturation via blood gas analysis or pulse oximetry.
Explain the relationship of excessive oxygen levels and depression of respiratory drive in certain COPD (CO retaining) patients.
These patients do not breathe because of a high PCO2 level as in a normal person. They breathe due to a lower PO2. If this "hypoxic drive" is taken away by supplying excessive levels of oxygen, they will have no physiologic reason to continue breathing.
Some COPD patients experience a reduction in respiratory drive as a result of excessive oxygenation. This patient's values suggest acute and chronic respiratory acidosis, evidenced by an elevated bicarbonate value; the acidic pH is a reflection of decompensation, as the patient's PaCO2 has risen. It is likely that this patient's blood gas values prior to the onset of illness, were as follows: pH=7.35, PaCO2=60 torr, PaO2 = 60 torr (on room air,) HCO3=32 mEq/L
These values are typical of stable COPD patients. When illness develops, the patient may experience more CO2 retention that will lower the pH. Bicarbonate value will rise over time to compensate for the pH disturbance, but the patient will be acutely acidic until full compensation occurs.
A spontaneously breathing patient in the intensive care unit has viral pneumonia and is receiving 60% oxygen. An arterial blood gas analysis reveals the results below. pH 7.58 PaCO2 24 torr HCO3 22 mEq/L PaO2 44 torr Describe the most appropriate therapy for the patient described above?
These values may be interpreted as acute respiratory alkalosis with moderate to severe hypoxemia. The most appropriate therapy suggested by these values is oxygen via non-rebreathing mask, assure a good fit and monitor outcome with repeat blood gas or pulse oximetry in 20 minutes.
An asthmatic patient has an increased inspiratory flow rate of 50 LPM, and requires 28% oxygen by aerosol mask. What flow rate would you set on the oxygen flow meter?
Using the "magic box," the Venturi ratio is first calculated. Dividing the needed total flow required by the "total parts" gives 5 LPM as the required 02 flow setting.
How would you go about calculating the total flow delivered from a 40% T-piece (Brigg's adapter) running at 10 LPM?
Using the '"magic box" calculate the Venturi ratio, then calculate the total flow by multiplying the 02 liter flow X the "total parts.'"
Low flow devices provide oxygen at a _____ FIO2
Variable
High flow device Can give a precise concentration of oxygen
Venturi mask
Which oxygen delivery devices(s) provide an accurate FIO2 regardless of the patient's ventilatory pattern?
Venturi masks are classified as high flow oxygen delivery devices because they can deliver a total flow rate of gas that meets or exceeds patient's inspiratory flow needs. Multiplying the patient's minute volume by 4 needs can derive estimation of inspiratory flow.
A patient is admitted to the emergency room with a chief complaint of shortness of breath. Arterial Blood Gases recorded at this time reveal the following: pH = 7.33, PaCO2 = 60 torr, PaO2 = 50 torr What delivery device would you select to administer supplemental oxygen to this patient?
With no additional patient history, the most appropriate oxygen delivery device would be a nasal cannula.
The minimum inspiratory need (inspiratory flow rate) may be determined by multiplying the patient's minute ventilation______.
X 4
If a massive gas leak occurs from the wall oxygen outlet when a flow meter is removed from the outlet, what should the RCP do immediately?
allay patient fears resulting from the sudden loud noise and re-insert the flow meter to stop the leak.
What is an important consideration in using an aerosol mask as the method of O2 delivery?
appropriate total flow rate of gas to the patient in order to maintain a predictable and consistent FIO2.
In what way(s) is a nasal cannula advantageous as compared with air entrainment (Venturi) devices?
are generally more comfortable than a mask. They should not be used for patients who have irregular breathing patterns
What is the function of the air-entrainment port ("venturi window") on the large volume nebulizer?
decrease the FIO2, and to increase total flow to the patient.
small compressed gas cylinder is generally the most practical oxygen-supply system to use for patient transport.
e cylinder
A patient has a peak inspiratory flow of 48 LPM. What is the MINIMUM flow meter setting needed to meet the patient's requirements if a 40% nebulizer is being used?
flow meter is run at 12 liters per minute, the device will deliver a total flow of 48 liters per minute. Calculate total flow as follows: 1 is to 3 as 12 is to X. Solve for X.
You are making general rounds in the hospital when you find a patient whose reservoir tubing has fallen off his Brigg's adapter. What effect would the absence of this reservoir tubing having on the delivered FIO2?
in room air being inhaled and the overall 02 percentage decreasing.
How could you remedy the situation if a patient receiving oxygen via a simple mask at 6 LPM remains hypoxic after 2 hours?
increase the oxygen concentration delivered to the patient by applying a non-rebreathing reservoir oxygen mask
The respiratory therapist is informed of a fire in the west wing of the hospital. What is the most appropriate initial response/ recommendation to this situation?
is to ensure patient safety. Thus the respiratory therapist would shut off the oxygen zone valve to the west wing, and provide emergency oxygen for all the patients who become relocated from the west wing.
patient receiving oxygen at 6 LPM via nasal cannula complains that he does not feel any oxygen coming out. What would you do?
is to verify that there are no leaks.
A patient requires an oxygen concentration of approximately 35% to prevent hypoxemia. The patient vomits frequently as a result of medication taken to treat his condition. Which oxygen delivery device would be safest to satisfy this patient's oxygen requirements?
nasal cannula operated at a flowrate of 4 lpm.
The compressor delivers pressurized air not _____
oxygen
What should be done immediately for an 88 year old COPD patient who becomes lethargic and has the following ABGs while receiving O2 via a nasal cannula at 4 lpm? pH 7.32 PaCO2 70 torr PaO2 95 torr HCO3 35 mEq/L
partially compensated respiratory acidosis with normoxia. this is normal for a copd patient with acute problems
The physician asks you which 02 delivery device would be best for a patient who needs about 75% 02. What would you recommend
properly fitting non-rebreathing mask with enough flow to keep the reservoir bag inflated will deliver the highest 02 percentage of the devices available.
A patient is receiving 40% O2 via aerosol T-piece. Condensation of the aerosol in the tubing almost completely occludes the tubing at its lowest point. How will the PAO2 be affected?
reduces the forward pressure of gas at the outlet of the entrainment device. LESS air is drawn into the gas stream through the entrainment ports of the device, thereby RAISING the delivered FIO2
A patient is receiving O2 via a non-rebreathing mask at 8 LPM. The respiratory care practitioner notices that the reservoir bag on the mask empties completely during inspiration. What should the practitioner do immediately to assure successful clinical outcome?
the flow rate of O2 into the bag must be increased to assure safe O2 therapy with this appliance.
In what situations would a T-piece be indicated?
to provide aerosol (humidity) with a precise FIO2, whereas others have one or more limitations that preclude their use
You are called to draw an arterial blood sample from a patient who is wearing a 35% air-entrainment (Venturi) mask. When you enter the room, you notice that his covers are drawn up over the air entrainment ports of the mask. How would this affect the function of the mask?
will result in the patient receiving a higher 02 percentage than desired (this is because there would be less room air dilution). also less flow
