Ch. 1: Oxygen and Medical Gas Therapy Flashcards
Storage and Control of Medical Gases
Gas cylinders are stored at high pressures; a full O2 cylinder contains ____ psig pressure.
2200
What is the color of this cylinder?
Oxygen
Green
White (internationally)
What is the color of this cylinder?
Helium
Brown
What is the color of this cylinder?
Carbon dioxide
Gray
What is the color of this cylinder?
Nitrous oxide
Light blue
What is the color of this cylinder?
Cyclopropane
Orange
What is the color of this cylinder?
Ethylene
Red
What is the color of this cylinder?
Air
Yellow
What is the color of this cylinder?
CO2/O2
Gray and Green
What is the color of this cylinder?
He/O2
Brown and Green
What safety system do large cylinders use?
ASSS - American Standard Safety System
What safety system do small cylinders use?
Pin Index Safety System
Indications of Oxygen Therapy: (3)
- Hypoxemia
- Labored breathing or dyspnea
- Increased myocardial work
What are some complications of oxygen therapy? (5)
- Respiratory depression
- Atelectasis
- Oxygen toxicity
- Reduced mucociliary activity
- ROP
Indication of NO
In term or near-term neonates of more than 34 wks who have evidence of PPHN
Inhaled NO may be beneficial in improving refractory hypoxemia in ARDS patients after chest trauma.
What type of patients would benifit from mixed gas therapy (He/O2)? (3)
- Obstruction from secretions
- Asthma (during episodes of bronchospasm)
- Airway obstructions (tumors, foreign bodies or tracheomalacia)
What is the lowest effective dose of nitric oxide (NO)?
5 ppm or less
What are some indications of hyperbaric oxygen therapy?
- CO poisoning
- Cyanide poisoning
- Decompression sickness (“the bends”)
- Gas gangrene
- Gas embolism
- Osteonecrosis
Cylinders are constructed of _____
steel.
Chrome molybdenum
What are the most common cylinder sizes for O2 storage?
H and E cylinder
True of False?
An O2 regulator cannot be attached to a helium cylinder.
True
What are the two types of safety relief devices?
- Frangible disk—breaks at 3000 psig
- Fusible plug—melts at 208° to 220° F (caused
by high ambient temperature or high pressure,
which increases the temperature)
What allow the escape of excess gas if the pressure in the cylinder increases?
Safety relief devices on cylinder valves
_____________ developed a color code system for cylinders to distinguish the various gases.
The Compressed Gas Association (CGA)
Explain how cylinders are visually tested.
Cylinders are visually tested by lowering a light bulb inside to look for corrosion.
How often are cylinders tested for corrosion?
Cylinders are hydrostatically tested every 5 or 10 years, depending on the cylinder marking.
What does a star next to latest test date mean?
A star next to the latest test date means the next test must be done 10 years from that date.
What does hydrostatic testing determine?
The amount or number of:
(1) Wall stress
(2) Cylinder expansion
(3) Leaks
What type of O2 is most commonly produced by the process of fractional distillation?
Liquid O2
Liquid O2 is stored in Thermos containers at a pressure not to exceed ______ and what temperature?
250 psig and at a temperature below -297° F (the boiling point of O2).
Regulators are devices attached to the cylinder valve to __________.
regulate flow and reduce cylinder pressure to working pressure (i.e., 50 psig).
Dust or debris entering the regulator from the cylinder valve may rupture the diaphragm.
How do you prevent this?
Always “crack” the cylinder before attaching a regulator. This is accomplished by turning the cylinder on and back off quickly to blow out the debris from the cylinder outlet.
Constant pressure trapped in the pressure chamber after the cylinder is turned off may rupture the diaphragm.
How do you prevent this?
Always vent pressure in the regulator by turning the flowmeter back on after the cylinder is turned off.
What are the cylinder factors for H and E?
H cylinder = 3.14 L psig
E cylinder = 0.28 L psig
Duration of flow EQUATION
Cylinder pressure x cylinder factor / flow rate
What are the three ways to determine whether a flowmeter is compensated for pressure?
(a) It is labeled as such on the flowmeter.
(b) The needle valve is located after the float.
(c) The float jumps when the flowmeter, while it is turned off, is plugged into a wall outlet.
Flowmeter outlets use which safety system?
the Diameter Index Safety System, as do all gas-administering equipment that operates at less than 200 psig, so that attachment to the wrong gas source is avoided.
Uncompensated or compensated flowmeter?
The needle valve is located proximal to (before) the float; therefore atmospheric pressure is in the Thorpe tube. Any back pressure in the tube affects the rise of the float.
Uncompensated flowmeter
Uncompensated flowmeters should not be used clinically
Uncompensated or compensated flowmeter?
The needle valve is located distal to (after) the float; therefore 50 psig is in the tube. Only back pressure that exceeds 50 psig will affect the rise of the float.
Compensated or compensated flowmeter
The flowmeter reads accurately with an attachment, such as a humidifier or nebulizer on the outlet, or with any obstruction downstream. If the O2 tubing is completely obstructed with no gas flowing to the patient, the flowmeter will reflect that with a flow reading of near 0.
Technical problems associated with reducing valves and regulators
A weak spring can result in diaphragm vibration and inadequate flows that are caused by ____________________.
premature closing of the inlet valve.
Does this describe a compensated or uncompensated flowmeter?
When a restriction, such as a humidifier or a nebulizer, is attached to the outlet, back pressure into the tube forces the float down and compresses the gas molecules closer together so that more molecules go around the float than are indicated by the float. Therefore the flowmeter reading is lower than the amount the patient is actually receiving.
Uncompensated flowmeter
What should be done in this instance?
If the flowmeter is turned off completely but gas is still bubbling through the humidifier or is heard coming from the flowmeter.
The valve seat is faulty and the flowmeter should be replaced.
The Bourdon gauge flowmeter is a pressure gauge that has been calibrated in liters per minute. It is compensated or uncompensated for back pressure?
Uncompensated for back pressure
When a humidifier or nebulizer is attached to the outlet of the Bourdon gauge, back pressure is generated into the gauge (which measures pressure), and the gauge reading is higher or lower than the amount the patient is actually receiving?
HIGHER
What is the advantage of the Bourdon gauge over the Thorpe tube?
The advantage of the Bourdon gauge is that it is not position dependent. It reads just as accurately in a horizontal position as it does in a vertical position. This makes it the flowmeter of choice when transporting a patient with an oxygen tank.
Signs and Symptoms of Hypoxemia
- Tachycardia
- Dyspnea
- Cyanosis (unless anemia is present)
- Impairment of special senses
- Headache
- Mental disturbance
- Slight hyperventilation
COMPLICATIONS OF OXYGEN THERAPY
How would you prevent respiratory depression?
Patients with COPD who is chronically hypoxic is most affected. Maintain PaO2 between 50 and 65 mm Hg for these patients.
COMPLICATIONS OF OXYGEN THERAPY
How do we prevent atelectasis?
High O2 concentrations in the lung can wash out nitrogen in the lung and reduce the production of surfactant, which may lead to atelectasis. Maintain FiO2 below 0.60.
COMPLICATIONS OF OXYGEN THERAPY
How do we prevent oxygen toxicity?
High O2 concentrations result in increased O2 free radicals and therefore lung tissue toxicity. This may lead to acute respiratory distress syndrome (ARDS). Maintain FiO2 below 0.60.
COMPLICATIONS OF OXYGEN THERAPY
How do we prevent reduced mucililary activity?
Maintain FiO2 below 0.60. The beating of the cilia in the mucociliary blanket is not as active when high FiO2 levels are used.
COMPLICATIONS OF OXYGEN THERAPY
How do we prevent retinopathy of prematurity (ROP)?
This is caused by high PaO2 levels in infants and results in blindness. It is more common in premature infants. Maintain PaO2 below 80 mm Hg. The normal level of PaO2 in infants is 50 to 70 mm Hg.
NORMAL PaO2 VALUES BY AGE
Less than or equal to 60 years old
80 mm Hg
NORMAL PaO2 VALUES BY AGE
70
70 mm Hg
NORMAL PaO2 VALUES BY AGE
80
60 mm Hg
What type of hypoxia is this?
Hypoxia caused by lack of O2 in the blood as a result of:
1. Inadequate O2 in the inspired air
2. Alveolar hypoventilation (Adminstering O2 alone is not beneficial).
3. Diffusion defects (Adminstering O2 alone is not beneficial).
4. V/Q mismatch
5. Anatomic right-to-left shunt (Adminstering O2 is not beneficial).
Hypoxemic hypoxia
If a normal PaO2 level cannot be maintained with a 60% O2 mask, a large shunt is probable and should not be treated with higher O2 concentrations. How should it be treated?
CPAP should be administered provided that the PaCO2 is at normal or below normal levels. If the PaCO2 level is elevated in a patient with hypoxemia, mechanical ventilation should be initiated.
When given a patient using 60% O2 or higher who is ventilating adequately (normal or low PaCO2) but has hypoxemia, place the patient on CPAP.
What is the exception to this rule?
If the question states that the patient has hypotension, a low cardiac output, or an elevated intracranial pressure. PEEP may worsen conditions.
What type of hypoxia is this?
The blood capacity to carry O2 is reduced as a result of:
1. Decreased Hb level
2. CO poisoning
3. Excessive blood loss
4. Iron deficiency
5. Methemoglobin
Anemic hypoxia
If the question states that the patient has been exposed to CO, always select the device that provides 100% O2, whether it is a nonrebreather, CPAP, or endotracheal (ET) tube flow-by.
EXAM NOTE!
To determine what a normal PaO2 is while any oxygen percentage is being breathed, multiply the percentage by 5. For example, a normal PaO2 for a patient breathing 40% oxygen would be approximately 200 torr (40 x 5). This is an approximation but can be helpful on the exam.
EXAM NOTE!
Patients who have been involved in fires or who have been breathing car fumes must be treated immediately for ______.
CO poisoning
The level of CO bound to Hb (carboxyhemoglobin) may be determined with ______.
CO oximetry
Even if a PaO2 is really high on a CO exposed patients, if the SaO2 is not around 95%, DO NO TITRATE THE OXYGEN DOWN.
The reason the SaO2 is so low and the PaO2 is so high is that O2 is not able to combine with Hb because it is already carrying CO. Therefore the O2 dissolves in the plasma, thereby increasing the PaO2.
What are the two ways that blood carries oxygen?
- Bound to hgb
- Dissolved in plasma
What type of hypoxia is this?
The O2 content and carrying capacity are normal, but capillary perfusion is diminished as a result of:
(1) Decreased heart rate
(2) Decreased cardiac output
(3) Shock
(4) Embolism
Stagnant (circulatory) hypoxia
What type of hypoxia is this?
The oxidative enzyme mechanism of the cell is impaired as a result of:
(1) Cyanide poisoning
(2) Alcohol poisoning
Histotoxic hypoxia
The FiO2 deliveryed by low-flow O2 delivery systems is dependent on what?
Patient’s ventilatory pattern
Histotoxic hypoxia is accompanied by increased _______ levels.
PvO2
Low-flow O2 systems does not meet the patient’s inspiratory flow demands; therefore what must make up the remainder of the patient’s tidal volume (VT)?
Room air
In most cases, humidifiers are not necessary if less than ____ is being delivered.
5 L/min
List the possible complications of transtracheal O2 catheter
- Accidental removal of the catheter
- Irritation or infection at insertion site or in the trachea
Transtracheal O2 catheter
How often should the transtracheal catheter be replaced?
Every 3 months before it becomes kinked, cracked, or obstructed by dry mucus.
Transtracheal O2 Catheter FiO2 and flow rate ranges
22-35%
1/4 to 4 L/min
NASAL CANNULA
FiO2 and flow rate range
24-40%
1/4 to 6 L/min
Although a flow of 6 L/min is acceptable, according
to the AARC clinical practice guidelines, the maximum O2
percentage obtainable with a nasal cannula is ______.
40%
NASAL RESEVOIR CANNULA
FiO2 and flow rate range
22-35%
1/4 to 4 L/min
SIMPLE O2 MASK
FiO2 and flow rate range
O2: 35-50%
Flow rate: 5-10 L/min
PENDANT RESEVOIR CANNULA
For this device to function properly, the patient must ____________ so that the exhaled air passes through the cannula tubing to inflate the reservoir.
exhale through the nose
SIMPLE O2 MASK
Minimum flow rate of ____ L/min is required to prevent buildup of exhaled CO2 in the mask.
5
PARTIAL REBREATHING MASK
FiO2 and Flow ranges
40-70%
10-15 L/min
NONREBREATHING MASK
FiO2 and ranges
60-80%
10-15 L/min
When is a nonrebreather mask considered a low-flow oxygen delivery system?
If only one exhalation port is covered with a one-way valve, FiO2 decreases because more room air can enter the mask. In this case the mask is considered a low-flow mask.
Low-flow O2 devices are adequate O2 delivery systems only when the patient meets the following criteria:
(1) Regular and consistent ventilatory pattern.
(2) Respiratory rate of less than 25 breaths/min.
(3) Consistent VT of 300 to 700 mL
Increasing the flow rate on high-flow
devices will not increase FiO2.
Read it and weep.
AIR ENTRAINMENT MASK
FiO2 ranges
24-50%
What determines the FiO2 of a air entrainment mask?
The jet size and entrainment port determine the FiO2.
When asked to determine what O2 delivery device to set
up for a patient, pay close attention to the patient’s
breathing pattern. If the question states that the patient’s
VT is fluctuating and not consistent, or if the respiratory
rate is above 25 breaths/min, what should you pick?
HIGH-FLOW DEVICE
AIR ENTRAINMENT MASK
The larger the entrainment port, the more air entrained and the ________ the FiO2.
Lower
and VICE VERSA
The larger the jet size, the less air entrained and the ____ the FiO2.
Higher
and VICE VERSA
AEROSOL MASK
FiO2 and flow ranges
21-100%
8-15 L/min
FACE TENT
FiO2 and flow ranges
21-40%
8-15 L/min
What is another name of the T piece?
Briggs adaptor
What type of patients is the face tent primarily used for?
Patients with facial trauma or burns or for those who cannot tolerate a mask
T-pieces are used for what type of patients?
Intubated or tracheostomy patient
TRACHEOSTOMY MASK (COLLAR)
FiO2 and flow ranges
35-60%
10-15 L/min
OXYMASK
FiO2 and flow rates
24-90%
1-15 (flush) L/min
To ensure adequate flow rates on a device set on
60% or higher, what should you do?
Use two flowmeters connected in line together.
To ensure adequate flow rates, set the flowmeter to a rate that delivers a total flow of at least 40 L/min.
A restriction, such as kinked aerosol tubing or water in the tubing, causes back pressure into the nebulizer, decreasing the amount of air entrainment and therefore ____________ the percentage of O2.
increasing
Doesn’t make sense, but okay.
When using a blender/nebulizer to provide O2, make sure the nebulizer is set on 100%.
As the gas from the blender enters the nebulizer, room air will be entrained, which dilutes the blender mixture to a lower percentage if the nebulizer is set to anything but 100%.
ALVEOLAR AIR EQUATION
[(PB-PH20)(FiO2)] - (PaCO2 x 1.25)
OXYGEN BLENDER
These devices use 50-psig gas sources to mix or blend O2 and compressed air proportionately to deliver ____________ O2 at flow rates of 2 to 100 L/min.
21% to 100%
What is the normal A-a gradient on room air?
4-12 mm Hg
TRACH MASK OR COLLAR
FiO2 and flow rate range
35-60%
10-15 L/min
What is this mask called?
It is an “open mask” system utilizing several holes that allow exhaled CO2 to escape more easily, decreasing the feeling of claustrophobia.
OxyMask
HIGH FLOW NASAL CANNULA
Flows of up to _____ are used in adults.
60 L/min
What is the second lightest gas and therefore, when combined with O2, decreases the total density of the gas? This allows the gas to pass through obstructions more easily.
Helium
What are the two most common heliox mixtures?
- 80:20
- 70:30
For an 80:20 mixture of helium and O2, multiply the flowmeter reading by 1.8 to determine the correct flow rate. To deliver a specific flow, divide the flow rate by 1.8.
Read it and weep.
For a 70:30 mixture of heliox, multiply the flowmeter reading by 1.6 to get correct flow rate. Divide by 1.6 to obtain a specific flow rate.
Know it!
Heliox mixtures must be delivered in a tightly closed system, such as a nonrebreathing mask, ET tube, or tracheostomy tube, to prevent what?
The lighter gas from leaking out.
What is the only side effect of heliox therapy?
Distortion of the voice
Extreme caution must be used when mixing heliox from a helium cylinder and an O2 cylinder. Inaccurate flow readings may result in the patient receiving less than 21% O2.
A premixed helium/ O2 cylinder is recommended.
If a patient receiving an 80:20 heliox mixture is hypoxemic, why will it help to change to a 70:30 mixture?
Provide supplemental O2 while at the same time using a lower-density gas for better gas movement through the obstruction.
________ is a selective pulmonary vasodilator that improves blood flow to ventilated alveoli, which results in decreased intrapulmonary shunting and improved arterial oxygenation.
Inhaled nitric oxide (NO)
What is the normal starting dose of inhaled nitric oxide (NO)?
20 ppm
The dose is then weaned to the lowest effective dose and continued until the neonate’s condition has improved.
Before discontinuning iNO, the patient should receive a dose of ____ for 30 min to 1 hr.
1 ppm
Before discontinuing INO, what should you do to provide hemodynamic support?
Increase FiO2
Hyperbaric Oxygen Therapy
What is the difference between a multiplace chamber and monoplace unit?
- The multiplace chamber is a walk-in unit that accomodates multiple people
- Monoplace unit accomodates only one person at a time
Physiologic Effects of Hyperbaric Oxygen Therapy (5)
- Elevated PaO2 levels
- Vasoconstriction
- New capillary bed formation
- Metabolic alteration of aerobic and anaerobic organisms
- Reduction of nitrogen bubbles in the blood
HBO treatments or “dives” usually require how much time to complete?
90 min at 2-3 atm, two to four times a day.
Galvanic Cell O2 Analyzers
_ is used to chemically reduce O2 to electron flow.
Electrolyte gel
What is a clark electrode used to measure?
O2 concentration
Galvanic Cell O2 Analyzers and Polarographic O2 Analyzers
What are some things to analyzer reading is affected by? (5)
- Water
- Positive pressure
- High altitude
- A torn membrane
- Lack of electrolyte gel
Polarographic O2 Analyzers
________ poloarizes the electrodes to allow O2 reduction to occur, which gives off electron flow.
A battery
Electrodes last longer on which analyzer?
Galvanic cell analyzer, but the polarographic analyzer has a quicker response time.
Pulse oximeters are devices that measure SaO2 by the principle of what?
Spectrophotometry, also referred to as SpO2.
Light from the probe is directed through a capillary bed to absobed in different amounts. It is displayed as a percentage.
List some causes of inaccurate pulse oximeter readings (9)
- Low blood perfusion
- CO poisoning
- Severe anemia
- Hypotension
- Hypothermia
- Cardiac arrest
- Dark skin pigmentation
- Ambient light sources
- Nail polish, especially blue, brown, green and black
Why should an oximeter never be use on patients with suspected CO exposure?
The reading may reflect an inaccurately high value.
A pulse ox is not capable of determining what substance is being carried by Hgb.
HbCO as high as ________ may be seen in heavy smokers, but higher levels are measured in patients who have inhaled large amounts of car fumes or smoke.
10-12%
HbCO levels of more than 20% result in nausea and vomiting. Fatal levels are _______.
60-80%
What is the best option to use for assessing oxygenatinon in patients who have been exposed CO?
CO-OXIMETRY (HEMOXIMETRY)
