Medical gas therapy is one of the most common types of respiratory care. It involves the process of delivering pressurized gases to treat a wide variety of pulmonary conditions.
In this guide, we will provide an overview of medical gas therapy and how it can be used by respiratory therapists to treat patients. We provided helpful practice questions for your benefit as well.
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What is Medical Gas Therapy?
Medical gas therapy is a treatment modality in which a gas is administered to a patient. Each medical gas, including oxygen, is considered a drug. This means that it should only be administered with the approval of a qualified physician or respiratory therapist.
When delivering medical gas therapy, it’s important to consider the type of gas, dosage, and delivery method. Each may vary depending on the patient’s condition.
Types of Medical Gases Used in Hospitals
There are several different types of medical gases, including the following:
- Nitric oxide
Each type of gas has different uses, indications, and contraindications. As a respiratory therapist, you must be familiar with the delivery of each type.
Oxygen is the most common medical gas. It is used to treat patients with hypoxemia, dyspnea, and acute or chronic respiratory conditions.
Medical air is considered to be a medical-grade gas because it has been treated to remove impurities. It is primarily used for respiratory support in the hospital setting.
Heliox is a mixture of helium and oxygen. This gas has a low density, which is useful for treating acute obstructive disorders. It is also used to treat croup, severe asthma, and post-extubation stridor.
Nitric oxide (NO) is a colorless, odorless medical gas that promotes vascular smooth muscle relaxation. It helps improve blood flow to ventilated alveoli, which results in improved oxygenation and decreased shunting.
Carbogen is a mixture of oxygen and carbon dioxide and is a medical gas that is rarely used. However, carbogen has been used to treat hiccups, carbon monoxide poisoning, and congenital cardiac anomalies in neonates.
What is Oxygen Therapy?
Oxygen therapy is the process of administering oxygen for therapeutic purposes. The primary goal of delivering oxygen therapy is to maintain tissue oxygenation throughout the body.
This helps prevent hypoxemia while minimizing the cardiopulmonary workload so that the heart and lungs can function properly.
Oxygen Delivery Systems
Each type has different uses, indications, advantages, and disadvantages. Respiratory therapists are required to understand how to deliver oxygen therapy with each delivery system.
Low-flow delivery systems provide oxygen at flows of 8 L/min or less. This includes:
- Nasal cannulas
- Nasal catheters
- Transtracheal catheters
High-flow delivery systems provide oxygen at flows that equal or exceed the patient’s peak inspiratory flow. This includes:
- Air-entrainment masks
- Air-entrainment nebulizers
- Blending systems
- High-flow nasal cannulas.
Reservoir delivery systems are effective because they can gather and store oxygen between the patient’s breaths. Some examples include:
- Simple masks
- Reservoir cannulas
- Partial rebreathing masks
- Nonrebreathing masks
Enclosure delivery systems provide oxygen by completely enclosing the patient from the outside environment. This includes:
- Oxygen hoods
- Oxygen tents
Again, each type of delivery system is characterized by how oxygen is delivered to the patient. Respiratory therapists are required to completely understand each type.
What is Hyperbaric Oxygen Therapy?
Hyperbaric oxygen therapy is a treatment modality in which the patient is exposed to 100% oxygen at pressures greater than one atmosphere absolute. This elevated pressure increases the amount of dissolved oxygen that can enter the body.
Hyperbaric oxygen therapy promotes hyperoxygenation, vasoconstriction, enhanced host immune function, and neovascularization. It is most commonly used in respiratory care to treat patients with carbon monoxide poisoning.
Medical Gas Therapy Practice Questions:
1. What are the three types of oxygen delivery?
(1) Low-flow, (2) High-flow, and (3)Reservoir.
2. What are three ways to determine the need for oxygen therapy?
Documented labs, a specific clinical problem or condition, and hypoxemia (which can cause other problems).
3. What are the AARC indications
Documented hypoxemia, acute care situations in which hypoxemia is suspected, severe trauma, acute myocardial infarction, short-term therapy, and surgical intervention i.e. post-anesthesia recovery.
4. What are the AARC precautions and possible complications of oxygen therapy?
A PaO2 greater than 60 mmHg, ventilator depression may occur in patients with an elevated PaCO2 creating hypoxic drive, FiO2 greater than .50, babies, and there is a fire hazard with oxygen delivery.
5. What is an air entrainment system?
It delivers direct high-pressure oxygen through a small nozzle or jet surrounded by ports. It depends on the air-to-oxygen ratio and amount of flow resistance downstream for the mixing site.
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6. How can the Respiratory Therapist help in avoiding oxygen toxicity?
Limit patient exposure to 100% oxygen to less than 24 hours whenever possible. A high FiO2 is okay when the concentration can be decreased to 70% within 2 days and 50% or less in 5 days.
7. What are
They are used in emergency life support, critical care, and can provide up to 100% FiO2.
8. What is Carbon Dioxide-Oxygen therapy?
It is rarely used but it is a treatment for hiccups, carbon monoxide poisoning, and to prevent a complete CO2 washout.
9. What are the clinical objectives
To correct documented or suspected acute arterial hypoxemia, decrease symptoms associated with chronic hypoxemia, and to decrease the workload hypoxemia imposes on the cardiopulmonary system.
10. Why do COPD patients tend to hyperventilate when given oxygen?
This is likely due to the suppression of their hypoxic drive.
11. What is documented hypoxemia evidenced by?
By a PaO2 less than 60 mmHg, and
12. What are enclosures?
They are the oldest form of oxygen therapy, such as oxygen tents, hoods, and incubators.
13. How do you estimate the FiO2 with a low flow system?
1 L/min of nasal oxygen increases the FiO2 by 4%. 1L/min starts at
14 What are some examples of a reservoir system?
Reservoir cannula, reservoir mask, and non-rebreathing reservoir circuit.
15. Describe a flow of less than 5 L/min in a reservoir mask?
It acts as dead space and causes CO2 rebreathing.
16. What is heliox therapy?
It is used to reduce the work of breathing, in patients with severe acute asthma or upper airway obstructions until the primary problem can be resolved.
17. What is a high-flow nasal cannula?
It provides heated and humidified oxygen up to 60 L/min. It can sometimes be hard to determine the amount of positive pressure delivered.
18. What is the high-flow system?
Oxygen therapy equipment that supplies inspired gases at a consistent preset oxygen concentration.
19. How does oxygen therapy correct hypoxemia?
By increasing the alveolar and blood levels of oxygen.
20. What is hyperbaric oxygen therapy?
The therapeutic application of oxygen at pressures greater than one atm.
21 What are some causes of hypoxemia?
Pulmonary vasoconstriction and pulmonary hypertension.
22. Hypoxemia can cause other manifestation such as?
Tachypnea, tachycardia, cyanosis, and a distressed appearance.
23. What is a low-flow system?
It is a variable performance oxygen therapy device that delivers oxygen at a flow that provides only a portion of the patient’s inspired gas needs. They provide supplemental oxygen directly to the airway. Some examples include a nasal cannula, nasal catheter, and
24. What is the ‘Magic Box’?
It is a shortcut for the Air-to-oxygen ratio, used to estimate high flow FiO2. It goes as follows: 20 top left, 100
25. What are the most common air entrainment devices?
Air entrainment mask (i.e. Venturi mask) and air entrainment nebulizer.
26. What is the most common mode of respiratory therapy?
27. What is Nitric oxide?
It is given for pulmonary vasodilation and used in airway obstruction. It is colorless, odorless, diffusible, lipid soluble, and relaxes capillary smooth muscle and improves blood flow to ventilated alveoli. It is used in neonates, ARDS patients, and adults with pulmonary hypertension. The main thing to remember is that it’s an inhaled gas used to reduce pulmonary artery pressure and improve arterial oxygenation
28. What are oxygen blenders?
They help provide a precise FiO2 by mixing air and oxygen. Air and oxygen enter this device and pass through dual pressure regulators to match pressures.
29. What can oxygen reduce?
It can help to reduce high ventilatory demand and the work of breathing.
30. Oxygen therapy can do what to mental function in patients with chronic hypoxemia?
It can improve mental function.
31. What are oxygen hoods?
The best method for controlled oxygen therapy for infants and also allows access for infant care. It has a heated air entrainment nebulizer or blending system with a humidifier.
32. What are oxygen tents?
A method for delivering cooled oxygen to pediatric patients. The opening often makes it hard to keep the oxygen concentration at the needed level. It’s used mostly for pediatric aerosols for croup.
33. Patients with chronic hypoxemia have an increased workload and over long-term, this can lead to what?
It can lead to right ventricular failure, which is known as cor pulmonale.
34. What is a reservoir mask?
It is the most common reservoir system. The types
35. What is a reservoir system?
An oxygen delivery system that provides a reservoir oxygen volume that the patient taps into when the patient’s inspiratory flow exceeds the device flow.
36. What is retinopathy of prematurity (ROP)?
An abnormal ocular condition that occurs in some premature or low birth-weight infants who receive oxygen.
37. What SpO2 threshold value indicates the need for oxygen therapy?
Less than 92% for a normal, healthy adult.
38. What are the two types of reservoir cannulas?
Nasal reservoir and pendant reservoir.
39. How is a
It is surgically placed in the trachea through the neck by a physician.
40. Hyperbaric Oxygen Therapy is administered via what?
It is administered via a
41. What are two acute conditions for which Hyperbaric Oxygen would be administered by the Respiratory Therapist?
Air embolism and Carbon Monoxide Poisoning.
42. What bedside findings would lead to the necessity of oxygen therapy?
Tachypnea, tachycardia, and confusion.
43. What are determining factors for oxygen toxicity?
The PO2 and exposure time.
44. What are drawbacks of Hyperbaric Oxygen therapy?
Ear or sinus trauma (i.e. busted eardrum), worsened pneumothorax (don’t use if diagnosed), oxygen toxicity, fire (not spontaneous combustion).
45. What are the drawbacks to Nitric Oxide Therapy?
46. What are examples of high flow oxygen delivery systems?
They provide 100% of the patient’s oxygen needs. Examples
47. What are examples of low flow oxygen delivery systems?
They provide part of the patient’s oxygen needs. Examples
48. What are three designs for oxygen delivery systems?
(1) Low-flow systems, (2) Reservoir systems, and (3) High-flow systems.
49. What are
(1) Correct documented or suspected acute Hypoxemia, (2) Decrease symptoms associated with chronic hypoxemia, and (3) Decrease the workload hypoxemia imposes on the cardiopulmonary system.
50. What are
Simple Mask, Partial Rebreathing mask, and Non-Rebreathing mask.
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51. What causes infiltrates in the lung parenchyma?
Prolonged exposure to a high FiO2.
52. What do Demand and Pulse-dose systems do?
They help to conserve oxygen by providing flow during inspiration only.
53. What does a high-flow nasal cannula provide?
It provides a high FiO2, high relative humidity, and positive pressure.
54. What does oxygen toxicity primarily affect?
The lungs and CNS.
55. What happens in retinopathy of prematurity?
Excessive blood oxygen levels cause retinal vasoconstriction and necrosis.
56. What is a negative aspect of an Oxygen Tent?
Regulating cooling and the FiO2 can be difficult.
57. What is an Oxygen hood (Oxyhood)?
It is generally the best method for delivering controlled oxygen to infants and allows access for care.
58. What is the difference in oxygen use between a transtracheal catheter and nasal cannula?
A Transtracheal Catheter uses 40-60 % less oxygen to achieve the same PaO2 as a nasal cannula.
59. What is the FiO2 level delivered by a nasal catheter?
0.22 – 0.45 (replaced by nasal cannula).
60. What is the FiO2 relationship between nose and mouth breathers?
Nose Breathers = Increased FiO2; Mouth Breathers = Decreased FiO2.
61. What is the main benefit of Nitric Oxide Therapy?
It improves oxygenation without shunting.
62. What is the relationship between oxygen and FiO2?
Higher oxygen = Increased FiO2; Lower oxygen = Decreased FiO2.
63. What should the FiO2 level be at when using the nasal cannula (low flow)?
It should typically be 0.24 – 0.40 dependent on how much room air the patient inhales in addition to oxygen.
64. What’s the difference between a Venturi mask and a Venti mask?
There is no difference, you silly goose you.
65. Where are oxygen-related fire hazards at high risk?
In oxygen-enriched environments and surgical suites in the presence of hyperbaric oxygen therapy.
66. Which patients would benefit from Nitric Oxide Therapy?
Patients with pulmonary hypertension, as well as, ARDS and COPD patients.
67. Who is at risk of Absorption atelectasis?
Patients breathing small tidal volumes with an FiO2 above 0.50 are at great risk.
68. What is the overall goal of oxygen therapy?
To maintain adequate tissue oxygenation while minimizing cardiopulmonary work.
69. What are the three specific clinical objectives for oxygen therapy?
(1) To correct documented or suspected acute hypoxemia, (2) to decrease the symptoms associated with chronic hypoxemia, and (3) to decrease the workload hypoxemia imposes on the cardiopulmonary system.
70. What is cor pulmonale?
Enlargement of the right ventricle of the heart due to a disease of the lungs or pulmonary blood vessels.
71. What are the 4 major harmful effects of oxygen therapy?
Oxygen toxicity, depression of ventilation, retinopathy of prematurity, and absorption atelectasis.
72. At what point is humidification needed for a nasal cannula?
Over 4 L/min.
73. What is the most common liter flow and FiO2 for a nasal cannula?
The most common flow is 1-5 L/min. There is a 4% increase in FiO2 for every 1 L/min, so the patient’s FiO2 on room air is .21 and at 2 L/min, it will be .21 + .08 = .29.
74. What are the basic characteristics of a transtracheal catheter?
The deliver oxygen directly into the trachea through a small bore catheter that is surgically inserted into the trachea; uses 40-60% less oxygen flow than a cannula so no humidification is necessary; oxygen builds up in trachea during expiration and is taken in during inhalation.
75. What is the cause and fix for when the humidifier pop-off is sounding?
There is an obstruction distal to the humidifier. You should find and correct the obstruction; or, the flow is set too high. In this case, you should use an alternative device; or, there is an obstructed naris. In this case, you should also use an alternative device.
76. What should the Respiratory Therapist do if the patient is mouth-breathing?
Switch them to a simple or Venturi mask.
77. What are the characteristics of a simple mask?
They cover the mouth and nose with the body of the mask and they work by gathering and storing oxygen between the patient’s breaths; exhaled air escapes through holes in its body. If oxygen input is interrupted, air is drawn through these holes and around the mask edge. They work with flows of 5-12 L/min. A minimum of 5 L/min is needed to prevent the rebreathing of CO2. They provide
78. What are the causes of a patient constantly removing the mask?
The causes can be claustrophobia (use alternative device) or confusion (use restraints).
79. What causes the reservoir bag to collapse when the patient inhales?
The flow is inadequate and needs to be increased.
80. What does it mean if the reservoir bag remains inflated throughout inhalation?
It means that there is either a large mask leak (correct the leak) or the inspiratory valve is jammed or reversed (repair or replace the mask).
81. How do air entrainment systems operate?
They direct a high-pressure oxygen source through a small nozzle or jet surrounded by air entrainment ports.
82. What 2 factors affect the amount of air entrained?
The jet size or orifice and the air entrainment port size.
83. What effect does the jet size have on the way the air entrainment system operates?
The smaller the jet the higher the velocity, the higher the velocity the more air entrained so the lower the FiO2 and the greater the total output flow.
84. What effect does the air entrainment port size have on the system?
The larger the air entrainment port the more air is entrained so the lower the FiO2 and the greater the total output flow.
85. What is the air to oxygen ratio for 40% oxygen?
86. What is the air to oxygen ratio of 60% oxygen?
87. What is the effect of downstream flow resistance on air entrainment devices?
Any resistance to flow distal to the jet will result in less air entrained, therefore the delivered oxygen concentration will be increased. However, the total flow will also be decreased, therefore if the total flow does not meet the patient’s needs, the patient will inhale room air and the delivered oxygen concentration may actually be lower than what is being delivered.
88. What is the device of choice for the delivery of oxygen to patients with an artificial tracheal airway?
Oxygen can be delivered by either a T-piece (Briggs Adaptor) or Trach Collar. Due to an increased resistance to flow, the maximum oxygen input flow is between 12-15 L/min.
89. What is helium’s value as a therapeutic gas?
Based on the low density, it is used to decrease the work of breathing in patients with large airway obstructions by decreasing the turbulence of flow in the airways, which in turn, requires a reduction in the driving pressure needed to move air flow past the obstruction.
90. How should Heliox be delivered?
By a non-rebreather or simple mask.
91. By what means is oxygen for medical use in a hospital most commonly produced?
92. What is the most common and least expensive method for commercial production of oxygen?
Fractional distillation of air.
93. What is the U.S. Food and Drug Administration (FDA) purity standard for oxygen?
94. Which of the following methods of producing oxygen is commonly used in the home care setting?
95. Which of the following statements about CO2 is FALSE?
It is a flammable gas.
96. Which of the following statements about Helium is false?
It is heavier than air.
97. What key property of Helium makes it useful as a therapeutic gas?
It’s low density.
98. Which of the following gases is used to treat conditions causing hypoxic respiratory failure?
99. During inspection of the shoulder of a compressed gas cylinder, you note a plus sign (+) next to the test date. This indicates what about the cylinder?
That it can be filled to 10% above its service pressure.
100. According to the U.S. Department of Commerce, a gas cylinder that is color-coded blue should contain which of the following?
Storage and Delivery of Medical Gases Practice Questions:
101. According to the National Institute of Standards and Technology of the U.S. Department of Commerce, a gas cylinder that is color-coded brown and green should contain which of the following?
102. In clinical practice, how is a positive identification made of the contents of a medical gas cylinder?
Reading the cylinder label
103. Which of the following mechanisms do all compressed gas cylinders
104. The measured pressure in a liquid-filled cylinder is equivalent to which of the following?
The pressure of the surface vapor at any given temperature.
105. The measured pressure in a gas-filled cylinder is equivalent to which of the following?
The force required to compress its volume within the cylinder.
106. The gauge on an H cylinder of oxygen reads 2000
It would last about 17 hours and 30 minutes.
107. The gauge on an E cylinder of O2 reads 800
It would last about 1 hour and 15 minutes.
108. Which type of safety system will prevent you from connecting an air
109. A patient is to be taken to have an MRI and it will take approximately 30 minutes. The patient needs at least 10 L/min of oxygen. Which of the following E cylinders has the lowest amount of oxygen that you can safely use?
110. What is the cylinder color code for Helium?
111. When using a Bourdon gauge and an occlusion occurs distal to the gauge, the bourdon gage will:
Read higher than the actual L/min.
112. A regulator is what two things combined?
Reducing valve and flowmeter.
113. If you look at a Thorpe tube and the needle valve is positioned upstream or proximal to the actual tube, this would indicate what?
That it is uncompensated.
114. If you put a flowmeter into a gas outlet and the ball in the Thorpe tube jumps this would indicate what?
That the Thorpe tube is compensated.
115. If you had to transport a patient and knew the only way to continue the patient’s oxygen therapy was to lay the cylinder down flat, what kind of flowmeter would be most appropriate?
A Bourdon gauge.
116. An H cylinder reading 1500 psi with the flow set at 5 L/min will need to be changed out when?
It will need to be changed in about 15 hours and 30 minutes.
117. What type of safety system is used for E tanks or smaller?
Pin-Index safety system( PISS)
118. How long will an E cylinder of oxygen with 2200 psi of pressure and a flow rate of 4 L/min last?
119. What are the three clinical objectives of oxygen therapy?
(1) To correct acute hypoxemia, (2) To decrease chronic hypoxemia symptoms, and (3) To decrease the cardiopulmonary workload.
120. How does oxygen therapy go about correcting hypoxemia?
By raising the alveolar and blood levels of oxygen.
121. What are the four patient manifestations of hypoxemia?
Tachypnea, tachycardia, cyanosis, and an overall distressed appearance.
122. Which two primary areas of the body are affected by oxygen toxicity?
The lungs and the central nervous system.
123. What two factors determine the harmful effects of oxygen?
Exposure time and the partial pressure of oxygen.
124. As a general rule to avoid oxygen toxicity, patient exposure to 100% oxygen should be limited to how many hours?
Whenever possible, limit the exposure to less than twenty-four hours.
125. What are five hazards of supplemental oxygen therapy?
Oxygen toxicity, depression of ventilation, retinopathy of prematurity, absorption atelectasis, and fire hazard.
126. What is the primary reason that some COPD patients hypoventilate when given oxygen?
The most likely cause is suppression of their hypoxic drive.
127. Supplemental oxygen can cause what eye condition in some premature and low birth weight infants?
Retinopathy of prematurity.
128. How can you identify what gas is in a cylinder?
All cylinders are color-coded and labeled for the ID of contents.
129. What devices can medical gases be stored in?
They are either stored in high-pressure cylinders or large bulk reservoirs.
130. What is the most common oxygen tank used in transport?
The E cylinder.
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131. What gas is used with oxygen to manage severe airway obstruction?
132. What is the purpose of Nitric Oxide, when is it indicated, and in what kind of patient is it indicated?
It is used in hypoxemic respiratory failure for term or near-term infants.
133. What is the most effective therapeutic heliox mixture?
20% oxygen with 80% Helium.
134. What safety system has a yoke connection?
PISS–Pin Index Safety System
135. Why are zone valves used in hospitals?
To stop the flow of medical gases to a particular zone in the case of an emergency.
136. How are cylinders marked and identified?
They are color coded and marked with metal stamping on the shoulder.
137. How are gas cylinders filled with compressed gases?
They are normally filled to its service pressure at 70 degrees Fahrenheit. They can be filled to 10% in excess of service pressure.
138. How does heliox decrease the work of breathing?
It has a lower density and makes the gas flow more laminar.
139. How do you measure gas-filled cylinder contents?
The volume of gas in the cylinder is directly proportional to it’s pressure.
140. How do you measure liquid gas cylinder contents?
The pressure does not relate to the amount of liquid remaining, only the weight of the cylinder indicates the amount of gas inside.
141. How is medical-grade air produced?
It is produced by filtering and compressing atmospheric air.
142. How often are safety tests conducted on gas cylinders?
They are conducted every 5 or 10 years.
143. How should gas cylinders be stored?
They should be stored in racks or chained to
144. What are the physical characteristics of nitric oxide?
It is colorless, nonflammable, toxic (Supports combustion)
145. What are the physical characteristics of Nitrous Oxide?
It is colorless gas with slightly sweet odor and taste
146. What does a central piping system do?
It is used to deliver compressed gas to all areas throughout the hospital at standard working pressure (50-psi).
147. What does a pressure compensated Thorpe Tube do?
It prevents changes in downstream resistance, or back pressure, from affecting meter accuracy.
148. What is a flowmeter used for?
It is used to control the flow that is delivered to a patient.
149. What is a reducing valve used for?
To reduce gas pressure to a usable level.
150. What is Fractional distillation?
Atmospheric air is filtered to remove pollutants, water
Medical gas therapy is performed daily by respiratory therapists. That is why it’s essential to learn about the different types, indications, benefits, and hazards.
Hopefully, this guide can make the learning process easier for you. If so, we have a similar guide on lung expansion therapy that I think you’ll find helpful. Thanks for reading and, as always, breathe easy, my friend.
John Landry, BS, RRT
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
- Faarc, Heuer Al PhD Mba Rrt Rpft. Wilkins’ Clinical Assessment in Respiratory Care. 8th ed., Mosby, 2017.
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- “Acute Oxygen Therapy: A Review of Prescribing and Delivery Practices.” PubMed Central (PMC), 20 Oct. 2020, www.ncbi.nlm.nih.gov/pmc/articles/PMC4888716.
- “Acute Oxygen Therapy.” National Center for Biotechnology Information, 19 Sept. 1998, www.ncbi.nlm.nih.gov/pmc/articles/PMC1113909.