Medical Gas Therapy is one of the most common types of Respiratory Care. That means it’s a topic that every Respiratory Therapist (and student) should be thoroughly familiar with.

To help, we created this study guide which covers the basics of Medical Gas Therapy. We’ve also included some helpful practice questions for your benefit as well. So if you’re ready, let’s get started.

What is Medical Gas Therapy?

Medical Gas Therapy refers to the deliverance of gases for therapeutic purposes. Medical gases are technically considered to be drugs, so they should be administered and delivered with the recommendation of the physician or Respiratory Therapist.

What are the Types of Medical Gas Therapy?

Oxygen therapy is the most common type of medical gas therapy, although there are a few other types as well. Here are all the types of medical gas therapy listed out:

  • Oxygen Therapy
  • Helium-Oxygen Therapy
  • Nitric Oxide Therapy
  • Carbon Dioxide–Oxygen Therapy

Now let’s dive deeper into oxygen therapy and how to administer it appropriately.

When is it Appropriate to Recommend Oxygen Therapy?

As a Respiratory Therapist, it’s important to know how to evaluate, recommend, and administer the oxygen therapy for patients in need. Here’s a tidbit of knowledge to remember:

Oxygen is a drug, so we must treat it as such.

Oxygen is a prescribed drug that Respiratory Therapists commonly administered to patients requiring emergency life support, pulmonary disability, and post-operative states that have or may develop cardiopulmonary complications.

The administration of oxygen and other medical gases is one of the main job duties of a Respiratory Therapist.

This is why it’s so important to understand the goals, indications, contraindications, and hazards of oxygen therapy. The Respiratory Therapist must be able to evaluate, recommend, and administer all medical gas modalities appropriately, as well as recognize adverse reactions of the therapy.

Now let’s take a look at the procedure for delivering oxygen therapy.

Procedure for Delivering Oxygen Therapy:

1. Verify the Physician’s Order.

First and foremost, you always want to review and evaluate the orders that were written by the doctor, so that you can fulfill them appropriately in order to give the right care to the right patient.

2. Examine the Patient’s Chart.

You want to do this so that you can review any relevant notes or data. For example, you may review the following in the patient’s chart: their diagnosis, medications, therapies, radiographs, laboratory results, hemodynamic, electrocardiograms, sleep lab reports.

3. Gather and Prepare All Needed Equipment.

In this step, you may need to wash your hands and disinfect any equipment if needed. Assemble any equipment appropriately to verify that it is functioning properly. This includes troubleshooting the equipment if necessary.

4. Explain the Procedure to the Patient.

Use two patient identifiers to confirm the identity of the patient and introduce yourself and be sure to state that you are with the respiratory therapy department. Explain the purpose and objective of the procedure and be sure that the patient understands you.

5. Assess the Patient and Implement the Therapy.

Make sure to position the patient properly. Fully assess the patient which includes obtaining their vital signs, breath sounds, oxygen saturation, and ventilatory status.

Attach the oxygen device to the patient and use the appropriate humidification if needed. Adjust the flow meter to the order or necessary liter flow to deliver the appropriate amount of oxygen to the patient. Make sure to position the interface so that it is comfortably placed on the patient’s face. Verify that it is comfortable for the patient.

6. Assess the Effectiveness of the Therapy and Make Any Needed Adjustments.

This may require you to re-check the patient’s vital signs. Say, for instance, you place the patient on 2 liters binasal cannula, but their oxygen saturation is still hovering around 87%. In this case, you would need to increase the liter flow in order to elevate the patient’s oxygen saturation back into the normal range.

7. Follow-up.

This is where you ensure the patient’s comfort and safety, as well as noting that the oxygen therapy is working effectively. You will need to perform proper hand-washing and dispose of any infectious wastes or materials. Proceed to document all of the important and pertinent information in the patient’s chart.

Also, if the treatment type is not a continuous modality, now is the time for you to remove or disconnect any equipment. However, if it is a continuous modality (like a nasal cannula) then you can leave it as-is and monitor the stability of the oxygenation parameters.

What Skills are Required to Administer Oxygen Therapy?

The following are some of the skills that a Respiratory Therapist must acquire in order to administer oxygen therapy:

  • You must know how to identify the contents of medical gas cylinders and identify the markings on the cylinders as defined by the department of transportation. Know how to store and transport the cylinders safely. 
  • Know the difference between the American Standard Safety System (ASSS), the Diameter Index Safety System (DISS), and the Pin Index Safety System (PISS). 
  • Be able to describe the two main types of valves found on “E” and “H” cylinders and their functions.

  • Know the components of a bulk liquid system and a reserve system. Understand the characteristics of a small and large liquid oxygen reservoir and the advantages and disadvantages of each.
  • Know how to operate and troubleshoot an air compressor. 
  • Know and understand the components of regulators, bourdon gages, and Thorpe tubes. This includes knowing the difference between a pressure-compensated and non-pressure compensated flowmeter.
  • Know how to set up and operate an oxygen blender.
  • Know how to locate and identify zone valves in your healthcare facility in case of an emergency. Also just know and understand the purpose of zone valves.
  • Know how to use the wall outlet quick-connect system.  

With these skills, a Respiratory Therapist can confidently administer oxygen to their patient if and when it’s indicated. 

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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 for oxygen therapy?
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.

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 bag-mask devices?
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 for oxygen therapy?
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 an SaO2 less than 90% while breathing room air.

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 an FiO2 of 24%.

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.

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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 transtracheal catheter.

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 bottom left, and the desired oxygen in the center; subtract diagonally. The number in the upper right is the amount of air; the number in the lower right is the oxygen.

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?
Gas 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 include: simple mask, partial re-breathing mask, and nonrebreathing mask.

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 transtracheal catheter placed?
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 multiplace or monoplace chamber.

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?
Poor paradoxical response, rebound hypoxemia, and pulmonary hypertension.

46. What are examples of high flow oxygen delivery systems?
They provide 100% of the patient’s oxygen needs. Examples are: High flow nasal cannula, Cascade high-flow, Passover high-flow, and Venturi Mask.

47. What are examples of low flow oxygen delivery systems?
They provide part of the patient’s oxygen needs. Examples are: Nasal cannula, regular mask, partial rebreather mask, oxymizer, and a non-rebreather mask.

48. What are three designs for oxygen delivery systems?
(1) Low-flow systems, (2) Reservoir systems, and (3) High-flow systems.

49. What are three goals of oxygen therapy?
(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 three types of oxygen delivery masks?
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 an FiO2 of 35-50%. A simple mask should be chosen when a moderate FiO2 is needed for a short time.

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?
Fractional distillation

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?
Physical separation

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?
Nitric Oxide

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?
Nitrous Oxide.

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?
O2–He mixture

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 use to avoid excessively high buildup of cylinder pressure?
Pressure-relief mechanism on the valve stem.

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 psig. About how long would the contents of this cylinder last, until completely empty, at a flow of 6 L/min?
It would last about 17 hours and 30 minutes.

107. The gauge on an E cylinder of O2 reads 800 psig. About how long would the contents of this cylinder last, until completely empty, at a flow of 3 L/min?
It would last about 1 hour and 15 minutes.

108. Which type of safety system will prevent you from connecting an air flowmeter to an oxygen station outlet?

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?
900 psi

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?
153 minutes.

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 wall away from heat sources. No smoking signs posted and with cylinder caps in place if they are not in use. Store liquid oxygen containers in a cool, well-ventilated area.

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 and CO2. Purified air is liquefied by compression and cooled by rapid expansion (Joule-Thompson Effect). The resulting mixture is heated slowly to allow nitrogen to boil off, leaving just oxygen. Basically, it’s this: Air is filtered, liquefied, cooled, and then heated slowly resulting in pure oxygen.

Final Thoughts

So there you have it. As previously mentioned, medical gas therapy is a topic that every Respiratory Therapist must be familiar with — especially oxygen therapy.

Hopefully, this study guide can serve as a resource to make the learning process easier for you. We also have a guide on Lung Expansion Therapy that I think you will enjoy. Thanks for reading and as always, breathe easy my friend.


The following are the sources that were used while doing research for this article:

  • Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020. [Link]
  • Faarc, Heuer Al PhD Mba Rrt Rpft. Wilkins’ Clinical Assessment in Respiratory Care. 8th ed., Mosby, 2017. [Link]
  • “Acute Use of Oxygen Therapy.” National Center for Biotechnology Information, 1 June 2015,
  • “Acute Oxygen Therapy: A Review of Prescribing and Delivery Practices.” PubMed Central (PMC), 20 Oct. 2020,
  • “Acute Oxygen Therapy.” National Center for Biotechnology Information, 19 Sept. 1998,

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