Medical Gas Therapy: Overview and Practice Questions (2025)

Medical gas therapy is a vital component of modern healthcare, used to support or enhance a patient’s respiratory function. Whether delivering oxygen to treat hypoxemia, administering helium-oxygen mixtures to ease airway resistance, or using carbon dioxide for diagnostic procedures, medical gases play an essential role in patient care.

This therapy is most commonly used in emergency settings, intensive care units, and for individuals with chronic respiratory conditions such as COPD or asthma. Understanding the indications, delivery methods, and safety considerations of medical gas therapy is crucial for healthcare professionals.

In this article, we’ll explore the different types of medical gases, how they are delivered, and why proper administration is critical for effective respiratory support and overall patient safety.

What is Medical Gas Therapy?

Medical gas therapy refers to the clinical use of therapeutic gases to treat patients with respiratory and cardiovascular conditions. The most common gas used is oxygen, but others—such as nitric oxide, helium-oxygen mixtures (heliox), and carbon dioxide-oxygen mixtures (carbogen)—may be used for specialized treatments.

The main goal of medical gas therapy is to improve oxygen delivery to the body’s tissues and support adequate gas exchange in patients who are unable to maintain normal oxygen levels on their own. This can include patients with:

• Chronic lung diseases like COPD and asthma
• Acute conditions like pneumonia or pulmonary edema
• Newborns with respiratory distress
• Carbon monoxide poisoning
• Wound healing issues (in hyperbaric oxygen therapy)

These therapies are delivered through various devices, including nasal cannulas, face masks, high-flow systems, and hyperbaric chambers—each tailored to the patient’s specific condition and oxygen needs.

Note: Medical gas therapy is a fundamental part of respiratory care that helps restore and maintain proper breathing and oxygenation in a wide range of clinical situations. 

Watch the video and keep reading to discover how medical gas therapy supports patients and plays a vital role in respiratory care.

Types of Medical Gases Used in Hospitals

Medical gases play a critical role in patient care across various hospital departments—from emergency rooms and ICUs to operating rooms and respiratory care units. Each gas serves a specific purpose and must be administered with precision and care.

Here are the most commonly used types of medical gases in healthcare settings:

Oxygen (O₂)

Oxygen is the most widely used medical gas and is considered life-saving in many situations. It is essential for treating hypoxemia and is frequently administered during surgeries, in emergency care, and for chronic respiratory diseases like COPD, asthma, and pneumonia.

Oxygen improves tissue oxygenation, supports cellular metabolism, and is often delivered through devices such as nasal cannulas, masks, or mechanical ventilators. While indispensable, its use must be monitored to prevent complications such as oxygen toxicity or absorption atelectasis.

Medical Air

Medical air is a purified, compressed gas composed primarily of nitrogen (approximately 78%) and oxygen (about 21%), mimicking the natural composition of atmospheric air.

Unlike oxygen, it does not increase the risk of oxygen-induced lung injury, making it ideal for use in long-term respiratory support. It is used in ventilators, nebulizers, and for powering anesthesia machines. Medical air must be free of contaminants like oil or particulates to be safe for patient use.

Helium

Although helium by itself is not therapeutically useful due to its inability to support respiration, its physical property of being significantly lighter than air makes it valuable in respiratory medicine.

When blended with oxygen, helium reduces the density of inspired gas, which in turn lowers airway resistance. This effect is particularly beneficial in patients with upper airway obstructions or severe asthma attacks. On its own, however, helium cannot sustain life.

Heliox (Helium-Oxygen Mixture)

Heliox is a specialized mixture of helium and oxygen, often in ratios such as 80:20 or 70:30. It is primarily used to manage conditions with airflow limitation—such as status asthmaticus, croup, or tracheal stenosis—by enabling smoother airflow through narrowed or obstructed airways.

Heliox improves ventilation, reduces the work of breathing, and can temporarily stabilize patients until definitive treatments take effect. Its delivery typically requires special equipment to maintain the correct gas ratio.

Nitric Oxide (NO)

Nitric oxide is used as an inhaled gas primarily for its selective pulmonary vasodilation properties. It plays a critical role in managing pulmonary hypertension, especially in neonates with persistent pulmonary hypertension of the newborn (PPHN) or in patients with ARDS.

By relaxing pulmonary vessels, NO improves blood flow in ventilated lung regions, enhancing oxygenation without causing systemic hypotension. Since it can convert into toxic byproducts like nitrogen dioxide, its administration must be carefully monitored using specialized delivery systems and real-time gas analyzers.

Nitrous Oxide (N₂O)

Commonly referred to as “laughing gas,” nitrous oxide is widely used for its analgesic and anxiolytic properties, especially in dental procedures, labor, and minor surgeries.

It offers rapid onset and offset, making it a convenient option for short-term sedation. However, it must always be combined with oxygen to prevent hypoxia. Chronic exposure can have neurological side effects, so proper scavenging systems are required in clinical environments.

Carbogen (Carbon Dioxide-Oxygen Mixture)

Carbogen is a therapeutic blend of carbon dioxide and oxygen, typically in concentrations like 5% CO₂ and 95% O₂. It is used to stimulate the respiratory drive in patients with diminished ventilatory response, such as those with central hypoventilation or during specific diagnostic procedures like cerebral blood flow studies.

By increasing the level of CO₂ in the bloodstream, carbogen encourages deeper and more frequent breathing, although its use is less common in general clinical practice.

 

Note: Understanding the different types of medical gases and their clinical applications is essential for healthcare professionals, especially those in respiratory care. Each gas has a unique role, from oxygenating tissues to easing airway resistance or enhancing blood flow.

What is a Gas Cylinder?

A gas cylinder is a specially designed container used to store and transport compressed medical gases under high pressure. These cylinders are commonly made from steel or aluminum and come in various sizes, each labeled with a letter (such as E, H, or D) depending on its capacity.

In hospitals and clinical settings, gas cylinders supply essential gases like oxygen, medical air, and nitrous oxide to patients who need respiratory support or anesthesia. Each cylinder is color-coded and labeled for easy identification to ensure safety and prevent mix-ups.

Key Features of Medical Gas Cylinders:

• Pressure gauge to indicate how much gas remains
• Valve and regulator to control the flow and delivery pressure
• Color coding for safety (e.g., green for oxygen in the U.S.)
• Portable or stationary use depending on patient needs

Note: Gas cylinders are critical in emergency care, transport situations, and areas without built-in piped gas systems. Proper handling, storage, and maintenance are essential to ensure safety and prevent leaks or accidents.

What is Oxygen Therapy?

Oxygen therapy is a medical treatment that involves delivering supplemental oxygen to patients who are unable to maintain adequate oxygen levels on their own. It is commonly used to treat conditions that affect breathing and oxygenation, such as chronic obstructive pulmonary disease (COPD), pneumonia, heart failure, asthma, and COVID-19.

When the body’s oxygen levels drop too low—a condition known as hypoxemia—oxygen therapy helps restore adequate oxygen delivery to the tissues and organs. This improves cellular function, reduces the work of breathing, and prevents complications like organ damage.

Goals of Oxygen Therapy:

• Relieve hypoxemia
• Improve oxygen delivery to tissues
• Reduce shortness of breath
• Prevent or reverse organ dysfunction

Note: Oxygen therapy must be carefully monitored and adjusted based on the patient’s needs to avoid complications like oxygen toxicity or carbon dioxide retention.

Oxygen Delivery Systems

Delivering oxygen effectively requires specialized equipment designed to match a patient’s respiratory needs. These devices regulate the flow, concentration, and delivery method of oxygen therapy. Understanding the different types of delivery systems is essential for ensuring safe and appropriate treatment.

Oxygen delivery systems are commonly grouped into four main categories:

1. Low-Flow Systems
2. High-Flow Systems
3. Reservoir Systems
4. Enclosure Systems

Note: Each system has specific indications, advantages, and limitations. Respiratory therapists must be able to assess the clinical situation and select the appropriate system for optimal outcomes.

Low-Flow Systems

Low-flow systems deliver oxygen at flow rates typically up to 8 liters per minute (L/min). They do not meet the patient’s total inspiratory demand, which means the delivered FiO₂ can vary depending on the patient’s breathing pattern. These are most often used in stable or less critical cases.

Examples:

• Nasal cannula
• Nasal catheter
• Transtracheal catheter

High-Flow Systems

High-flow systems are capable of meeting or exceeding the patient’s peak inspiratory flow, delivering a consistent and precise oxygen concentration. These systems are ideal for patients with moderate to severe respiratory distress or when a fixed FiO₂ is required.

Examples:

• Air-entrainment masks (Venturi masks)
• Air-entrainment nebulizers
• Blending systems
• High-flow nasal cannula (HFNC)

Reservoir Systems

Reservoir systems function by collecting and storing oxygen during exhalation, allowing higher FiO₂ delivery with lower oxygen flow rates. This makes them efficient for moderate oxygen requirements and helps conserve oxygen usage.

Examples:

• Simple face mask
• Reservoir cannula
• Partial rebreather mask
• Non-rebreather mask

Enclosure Systems

Enclosure systems surround or isolate the patient in a controlled oxygen-rich environment. These are commonly used in pediatric or neonatal care, especially for infants who require precise FiO₂ control without using a direct interface.

Examples:

• Oxygen hood
• Isolette (incubator)
• Oxygen tent

Note: A thorough understanding of oxygen delivery systems is critical for respiratory therapists and other healthcare providers. The right system not only improves oxygenation but also minimizes risks and enhances patient comfort.

What is Hypoxemia?

Hypoxemia is a medical condition that refers to low levels of oxygen in the blood, specifically in the arteries. Since oxygen is vital for every cell in the body, a deficiency can lead to serious complications if not corrected promptly.

Normally, oxygen travels from the lungs into the bloodstream, where it binds to hemoglobin and is delivered to tissues and organs. When this process is impaired—due to lung disease, high altitude, or circulatory issues—hypoxemia can occur.

Common Causes of Hypoxemia:

• Chronic lung diseases (e.g., COPD, emphysema)
• Pneumonia
• Pulmonary embolism
• Heart failure
• Sleep apnea
• High altitude

Signs and Symptoms:

• Shortness of breath
• Rapid breathing (tachypnea)
• Cyanosis (bluish lips, fingers, or skin)
• Confusion or disorientation
• Increased heart rate (tachycardia)
• Fatigue or weakness

How It’s Diagnosed:

• Pulse oximetry: A noninvasive test that estimates oxygen saturation (SpO₂)
• Arterial blood gas (ABG) analysis: Measures the actual oxygen level (PaO₂) in arterial blood

Note: Treatment for hypoxemia depends on the cause but often includes oxygen therapy to raise blood oxygen levels and improve tissue oxygenation. In more severe cases, mechanical ventilation or medications may be required.

What is Hyperbaric Oxygen Therapy?

Hyperbaric oxygen therapy (HBOT) is a specialized medical treatment in which a patient breathes 100% oxygen while inside a pressurized chamber. The pressure inside the chamber is typically 1.5 to 3 times higher than normal atmospheric pressure (measured in ATA—atmospheres absolute).

This high-pressure environment allows more oxygen to dissolve in the blood plasma, significantly increasing oxygen delivery to tissues throughout the body. The enhanced oxygenation promotes healing, reduces inflammation, and helps fight infection.

Under normal conditions, oxygen is carried mainly by hemoglobin in red blood cells. In HBOT, the pressurized oxygen allows the plasma—the liquid portion of blood—to carry a much higher amount of dissolved oxygen.

This benefits tissues that are inflamed, infected, or starved of oxygen due to poor circulation or injury.

Common Indications for HBOT:

• Carbon monoxide poisoning
• Decompression sickness (the “bends”)
• Non-healing diabetic foot ulcers
• Crush injuries
• Gas gangrene
• Radiation tissue damage
• Burns
• Sudden sensorineural hearing loss
• Severe infections such as necrotizing fasciitis

Benefits of HBOT:

• Stimulates new blood vessel formation (angiogenesis)
• Enhances white blood cell activity to fight infection
• Reduces swelling and inflammation
• Improves wound healing
• Helps remove carbon monoxide and other toxins from the blood faster

Risks and Precautions:

• Barotrauma (ear or sinus pressure injuries)
• Oxygen toxicity (especially in the central nervous system)
• Temporary vision changes
• Claustrophobia (in some patients)
• Seizures (rare, due to high oxygen levels)

Summary: Hyperbaric oxygen therapy is a powerful tool in modern medicine, especially in treating conditions where oxygen delivery is compromised. By increasing oxygen availability in the bloodstream, HBOT accelerates healing, combats infection, and supports recovery in a range of serious medical conditions.

Medical Gas Therapy Practice Questions

1. What are the four types of oxygen delivery?  
1) Low-flow, 2) High-flow, 3) Reservoir systems, and 4) Enclosure systems.

2. What are three ways to determine the need for oxygen therapy?  
Laboratory evidence, clinical signs or conditions, and the presence of hypoxemia, which can lead to other complications.

3. What are the AARC indications for oxygen therapy?  
Documented hypoxemia, suspected hypoxemia in acute care settings, severe trauma, acute myocardial infarction, and perioperative management including post-anesthesia recovery.

4. What are the AARC precautions and potential complications of oxygen therapy?  
Oxygen toxicity when PaO2 > 60 mmHg, ventilatory depression in patients with chronic CO2 retention, absorption atelectasis from FiO2 > 0.50, and fire risk, especially in neonatal care.

5. What is an air entrainment system?  
A device that mixes oxygen with room air based on jet velocity and port size, delivering a fixed FiO2 regardless of patient breathing pattern.

6. How can a respiratory therapist help minimize oxygen toxicity?  
Limit 100% oxygen use to less than 24 hours; reduce FiO2 to ≤ 70% within 2 days and ≤ 50% within 5 days when possible.

7. What are bag-mask devices?  
Manual resuscitation tools used in emergency and critical care that can deliver nearly 100% oxygen when connected to a reservoir and adequate flow source.

8. What is carbon dioxide-oxygen therapy?  
A rarely used therapy for hiccups, CO poisoning, and to prevent total CO2 washout in specific neurological cases.

9. What are the clinical goals of oxygen therapy?  
To correct hypoxemia, alleviate hypoxemia-related symptoms, and reduce the cardiopulmonary workload.

10. Why might COPD patients hyperventilate when given oxygen?  
Because high oxygen levels can blunt their hypoxic respiratory drive, leading to hypoventilation and CO2 retention.

11. How is documented hypoxemia defined?  
A PaO2 < 60 mmHg or SaO2 < 90% while breathing room air.

12. What are oxygen enclosures?  
Oldest delivery systems, including oxygen tents, hoods, and incubators, mostly used for infants and small children.

13. How do you estimate FiO2 with a nasal cannula?  
Start at 24% for 1 L/min and add 4% for each additional liter per minute.

14. What are examples of reservoir oxygen systems?  
Reservoir cannulas, simple masks, partial rebreathers, and non-rebreathers.

15. What happens if a reservoir mask runs at less than 5 L/min?  
It can cause CO2 rebreathing due to insufficient flow clearing exhaled gas.

16. What is heliox therapy?  
A mixture of helium and oxygen used to reduce airway resistance and improve gas flow in cases of upper airway obstruction or severe asthma.

17. What is a high-flow nasal cannula (HFNC)?  
A system that delivers heated, humidified oxygen at flows up to 60 L/min, potentially offering low levels of positive pressure.

18. What is a high-flow system?  
A device capable of meeting or exceeding a patient’s inspiratory demand with a consistent, fixed FiO2.

19. How does oxygen therapy correct hypoxemia?  
By increasing alveolar oxygen tension, thereby raising the oxygen content in arterial blood.

20. What is hyperbaric oxygen therapy?  
The medical use of oxygen at pressures greater than atmospheric pressure to enhance oxygen delivery and treat conditions such as CO poisoning, air embolism, and non-healing wounds.

21. What are common causes of hypoxemia?  
Ventilation-perfusion mismatch, diffusion defects, shunting, hypoventilation, and reduced inspired oxygen.

22. What are common signs and symptoms of hypoxemia?  
Tachypnea, tachycardia, cyanosis, accessory muscle use, and overall respiratory distress.

23. What is a low-flow oxygen system?  
A device that provides oxygen at flow rates that do not meet the patient’s total inspiratory needs, resulting in variable FiO2—examples include nasal cannula and simple mask.

24. What is the “Magic Box” used for in oxygen therapy?  
A visual tool to quickly determine the air-to-oxygen ratio for a given FiO2 using subtraction and placement of standard oxygen and air percentages.

25. What are common air entrainment devices?  
Venturi masks and air-entrainment nebulizers, which deliver fixed oxygen concentrations.

26. What is the most frequently used type of respiratory therapy?  
Oxygen therapy (gas therapy).

27. What is nitric oxide used for?  
An inhaled gas used for selective pulmonary vasodilation in neonates, ARDS patients, and adults with pulmonary hypertension.

28. What are oxygen blenders?  
Devices that precisely mix oxygen and air to deliver a specific FiO2, commonly used in neonatal and high-acuity settings.

29. What can oxygen therapy reduce?  
The work of breathing and ventilatory demand, especially in patients with respiratory distress or failure.

30. How can oxygen therapy benefit patients with chronic hypoxemia?  
It can enhance cognitive function, increase exercise tolerance, and improve overall quality of life.

31. What are oxygen hoods?  
Oxygen hoods are the preferred method for delivering controlled oxygen to infants. They allow easy access for care and typically use a heated air entrainment nebulizer or a blender with a humidifier.

32. What are oxygen tents?  
Oxygen tents are used primarily for pediatric patients, delivering cooled oxygen and aerosol therapy—often for croup. However, maintaining a consistent FiO2 is challenging due to frequent openings.

33. Patients with chronic hypoxemia have an increased cardiopulmonary workload, which can eventually lead to what?  
Right ventricular failure, also known as cor pulmonale.

34. What is a reservoir mask?  
A type of oxygen delivery system that stores oxygen in a reservoir during exhalation, allowing the patient to draw from it during inhalation. Examples include simple masks, partial rebreathers, and nonrebreathers.

35. What is a reservoir system?  
An oxygen delivery system that stores supplemental oxygen, which the patient can use when their inspiratory demand exceeds the device flow.

36. What is retinopathy of prematurity (ROP)?  
A potentially blinding eye condition that occurs in premature or low birth weight infants exposed to high levels of supplemental oxygen.

37. What SpO2 threshold indicates the need for supplemental oxygen in adults?  
An SpO2 of less than 92%.

38. What are the two types of reservoir cannulas?  
The nasal reservoir cannula and the pendant reservoir cannula.

39. How is a transtracheal catheter placed?  
A physician surgically inserts it directly into the trachea through a small incision in the neck.

40. How is hyperbaric oxygen therapy administered?  
It is delivered in a monoplace or multiplace pressurized chamber.

41. What are two acute conditions treated with hyperbaric oxygen therapy?  
Air embolism and carbon monoxide poisoning.

42. What bedside signs may indicate the need for oxygen therapy?  
Tachypnea, tachycardia, confusion, and signs of respiratory distress.

43. What are the key factors that determine oxygen toxicity risk?  
The partial pressure of oxygen (PO2) and the duration of exposure.

44. What are the potential risks of hyperbaric oxygen therapy?  
Ear or sinus barotrauma, worsening of pneumothorax, oxygen toxicity, and increased fire risk.

45. What are some potential complications of nitric oxide therapy?  
Poor or paradoxical response, rebound hypoxemia, and worsening pulmonary hypertension.

46. What are examples of high-flow oxygen delivery systems?  
High-flow nasal cannula, Venturi mask, cascade high-flow systems, and passover high-flow humidifiers.

47. What are examples of low-flow oxygen delivery systems?  
Nasal cannula, simple face mask, partial rebreather, nonrebreather, and oxymizer.

48. What are the three basic designs for oxygen delivery systems?  
Low-flow systems, reservoir systems, and high-flow systems.

49. What are the three primary goals of oxygen therapy?  
1) Correct hypoxemia, 2) Relieve hypoxemia-related symptoms, and 3) Reduce cardiopulmonary workload.

50. What are three common oxygen delivery masks?  
Simple face mask, partial rebreather mask, and nonrebreather mask.

51. What causes infiltrates to appear in the lung parenchyma?  
Prolonged exposure to high concentrations of oxygen (high FiO2), which can lead to oxygen toxicity and inflammation.

52. What do demand and pulse-dose oxygen systems do?  
They conserve oxygen by delivering it only during inhalation.

53. What does a high-flow nasal cannula (HFNC) provide?  
It offers high FiO2, heated and humidified gas, and a degree of positive airway pressure.

54. What body systems are primarily affected by oxygen toxicity?  
The central nervous system (CNS) and lungs.

55. What happens in retinopathy of prematurity?  
Excessive oxygen causes vasoconstriction and damage to the retinal vessels, potentially leading to blindness.

56. What is a disadvantage of oxygen tents?  
They are difficult to regulate for both temperature and FiO2.

57. What is an oxygen hood (oxyhood)?  
An enclosure that provides precise oxygen concentrations to infants and allows easy access for care.

58. How does oxygen use differ between a transtracheal catheter and nasal cannula?  
A transtracheal catheter requires 40–60% less oxygen to achieve the same PaO2 as a nasal cannula.

59. What is the FiO2 range for a nasal catheter?  
Approximately 0.22 to 0.45; however, it has largely been replaced by nasal cannulas.

60. How does breathing route affect FiO2 in low-flow systems?  
Nose breathing increases FiO2, while mouth breathing reduces it.

61. What is the main benefit of nitric oxide therapy?  
It improves oxygenation by selectively dilating pulmonary vessels in ventilated lung regions, reducing shunting and improving V/Q matching.

62. What is the relationship between oxygen flow and FiO2?  
Higher oxygen flow increases FiO2, while lower flow decreases FiO2.

63. What FiO2 range is typically delivered by a nasal cannula (low-flow)?  
FiO2 ranges from 0.24 to 0.40, depending on the flow rate and the patient’s inspiratory pattern.

64. What’s the difference between a Venturi mask and a Venti mask?  
There is no difference—“Venti mask” is simply a nickname for the Venturi mask.

65. Where are oxygen-related fire hazards most likely to occur?  
In oxygen-enriched environments such as operating rooms, intensive care units, and hyperbaric oxygen therapy chambers.

66. Which patients would benefit most from nitric oxide therapy?  
Patients with pulmonary hypertension, acute respiratory distress syndrome (ARDS), and severe COPD exacerbations.

67. Who is at risk of developing absorption atelectasis?  
Patients receiving high FiO2 (≥ 0.50) who have low tidal volumes, such as those on mechanical ventilation.

68. What is the overall goal of oxygen therapy?  
To ensure adequate tissue oxygenation while minimizing cardiopulmonary stress.

69. What are the three primary clinical goals of oxygen therapy?  
(1) Correct acute or suspected hypoxemia, (2) Alleviate symptoms from chronic hypoxemia, and (3) Reduce cardiopulmonary workload caused by low oxygen levels.

70. What is cor pulmonale?  
A condition where the right ventricle enlarges due to pulmonary hypertension caused by chronic lung disease.

71. What are four major adverse effects of oxygen therapy?  
Oxygen toxicity, respiratory depression, retinopathy of prematurity, and absorption atelectasis.

72. When should humidification be used with a nasal cannula?  
Whenever the flow exceeds 4 L/min.

73. What is the typical liter flow and FiO2 range for nasal cannula use?  
1–5 L/min flow, with FiO2 increasing by approximately 4% per liter; for example, 2 L/min delivers around 0.29 FiO2.

74. What are the characteristics of a transtracheal oxygen catheter?  
It delivers oxygen directly into the trachea, reducing oxygen usage by 40–60% compared to a nasal cannula and eliminates the need for humidification.

75. What causes the humidifier pop-off valve to activate?  
An obstruction distal to the humidifier, excessive flow, or nasal blockage. Correct by clearing the obstruction or switching to another device.

76. What should a respiratory therapist do if a patient is mouth-breathing?  
Switch to a simple face mask or a Venturi mask for more effective oxygen delivery.

77. What are the key features of a simple face mask?  
Covers the nose and mouth, requires at least 5 L/min to prevent CO2 rebreathing, delivers 35–50% FiO2, and is suited for short-term moderate oxygen needs.

78. Why might a patient repeatedly remove their mask?  
Due to discomfort from claustrophobia or confusion. Solutions include using an alternative device or applying restraints if necessary.

79. What does it indicate if the reservoir bag collapses during inhalation?  
The oxygen flow is insufficient and should be increased.

80. What does it mean if the reservoir bag remains inflated during inhalation?  
There may be a mask leak or a malfunctioning inspiratory valve. Check for leaks and replace the mask if needed.

81. How do air entrainment systems work?  
They use a high-velocity oxygen jet to entrain room air through adjustable ports, delivering a fixed FiO2.

82. What two factors influence the air entrainment rate?  
The size of the jet orifice and the diameter of the air entrainment ports.

83. How does jet size affect an air entrainment system?  
A smaller jet increases velocity, which entrains more air, resulting in a lower FiO2 and higher total flow.

84. How does port size affect air entrainment?  
Larger air entrainment ports allow more room air to mix in, reducing the FiO2 and increasing total flow.

85. What is the air-to-oxygen ratio for delivering 40% oxygen?  
3:1

86. What is the air-to-oxygen ratio for delivering 60% oxygen?  
1:1

87. What effect does downstream resistance have on air entrainment systems?  
It reduces the amount of air entrained, increasing delivered FiO2 but lowering total flow, which may not meet the patient’s inspiratory demand.

88. What is the preferred oxygen delivery device for patients with a tracheostomy?  
A T-piece (Briggs adapter) or tracheostomy collar with a flow of 12–15 L/min.

89. What makes helium a valuable therapeutic gas?  
Its low density reduces airway resistance and work of breathing in patients with upper airway obstructions.

90. How should heliox be administered?  
Via a nonrebreather mask or simple mask to maximize its effectiveness.

91. By what method is oxygen most commonly produced for medical use in hospitals?  
Fractional distillation of air.

92. What is the most common and cost-effective method of producing commercial oxygen?  
Fractional distillation.

93. What is the FDA purity standard for medical-grade oxygen?  
99%

94. What oxygen production method is typically used in home care settings?  
Physical separation using molecular sieves or membrane devices.

95. Which of the following statements about carbon dioxide (CO2) is FALSE?  
It is a flammable gas. (CO2 is actually non-flammable.)

96. Which of the following statements about helium is FALSE?  
It is heavier than air. (Helium is lighter than air.)

97. What property of helium makes it clinically valuable as a therapeutic gas?  
Its low density, which helps reduce airway resistance.

98. Which gas is used to treat hypoxic respiratory failure by improving V/Q mismatch?  
Nitric oxide

99. If you see a plus sign (+) next to the test date on a gas cylinder, what does it indicate?  
The cylinder may be filled up to 10% above its service pressure.

100. What gas is contained in a cylinder that is color-coded blue?  
Nitrous oxide

101. What is contained in a gas cylinder that is color-coded brown and green?  
An oxygen-helium mixture (Heliox).

102. How is the contents of a medical gas cylinder positively identified in clinical settings?  
By reading the cylinder label.

103. What safety mechanism is used on all compressed gas cylinders to prevent overpressurization?  
A pressure-relief device located on the valve stem.

104. In a liquid-filled gas cylinder, what does the pressure reading represent?  
The pressure of the surface vapor at the cylinder’s current temperature.

105. In a gas-filled cylinder, what does the pressure reading represent?  
The force exerted by the gas compressing its volume inside the cylinder.

106. If an H cylinder reads 2,000 psig and is set at 6 L/min, how long will it last?  
Approximately 17 hours and 30 minutes.

107. If an E cylinder reads 800 psig and is set at 3 L/min, how long will it last?  
Approximately 1 hour and 15 minutes.

108. What safety system prevents attaching an air flowmeter to an oxygen station outlet?  
DISS (Diameter-Index Safety System).

109. A patient needs 10 L/min of O2 for a 30-minute MRI. Which E cylinder has the minimum required pressure?  
At least 900 psig.

110. What is the color code for helium cylinders?  
Brown

111. What happens to a Bourdon gauge reading if there’s an occlusion distal to the gauge?  
It will display a falsely high reading.

112. A regulator is a combination of which two devices?  
A reducing valve and a flowmeter.

113. If the needle valve is located before the Thorpe tube, what type of system is it?  
An uncompensated Thorpe tube.

114. If the ball in a Thorpe tube jumps when connected to a gas outlet, what does that indicate?  
The flowmeter is compensated.

115. What flowmeter is best suited for patient transport when the cylinder is laid flat?  
Bourdon gauge

116. How long will an H cylinder with 1,500 psi and a flow rate of 5 L/min last?  
Approximately 15 hours and 30 minutes.

117. What safety system is used with E-size gas cylinders?  
Pin-Index Safety System (PISS)

118. How long will an E cylinder with 2,200 psi last at a flow rate of 4 L/min?  
Approximately 153 minutes.

119. What are the three main clinical objectives of oxygen therapy?  
1) Correct acute hypoxemia, 2) Decrease chronic hypoxemia symptoms, and 3) Reduce cardiopulmonary workload.

120. How does oxygen therapy help correct hypoxemia?  
By increasing the amount of oxygen in the alveoli and arterial blood.

121. What are the four common signs of hypoxemia in a patient?  
Tachypnea, tachycardia, cyanosis, and a generally distressed appearance.

122. Which two major body systems are most affected by oxygen toxicity?  
The lungs and the central nervous system (CNS).

123. What are the two key factors that determine the harmful effects of oxygen?  
Duration of exposure and the partial pressure of oxygen (PaO2).

124. To reduce the risk of oxygen toxicity, how long should 100% oxygen exposure be limited?  
Ideally, exposure should be limited to less than 24 hours.

125. What are the five primary hazards of supplemental oxygen therapy?  
Oxygen toxicity, hypoventilation, retinopathy of prematurity, absorption atelectasis, and fire risk.

126. Why do some COPD patients hypoventilate when given supplemental oxygen?  
Due to suppression of their hypoxic respiratory drive.

127. What eye condition can develop in premature infants receiving high oxygen concentrations?
Retinopathy of prematurity (ROP).

128. How can the contents of a gas cylinder be identified?  
By checking the color-coding and the label on the cylinder.

129. In what types of containers can medical gases be stored?  
High-pressure cylinders or large bulk liquid oxygen reservoirs.

130. Which oxygen tank size is most commonly used for patient transport?  
The E cylinder.

131. What gas is commonly used with oxygen to treat severe upper airway obstruction?  
Helium

132. What is nitric oxide used for, and in which patients is it indicated?  
It is used to treat hypoxemic respiratory failure in term or near-term infants.

133. What is the most effective heliox mixture for therapeutic use?  
80% helium and 20% oxygen.

134. Which safety system uses a yoke connection to prevent misconnections?  
Pin Index Safety System (PISS)

135. Why are zone valves important in a hospital’s gas delivery system?  
To shut off medical gas supply to a specific area during an emergency.

136. How are gas cylinders identified and marked?  
By color-coding and permanent metal stamping on the shoulder of the cylinder.

137. How are compressed gas cylinders filled?  
They are filled to their service pressure at 70°F and can be filled to 10% above service pressure if marked with a “+” symbol.

138. How does heliox therapy help reduce the work of breathing?  
By decreasing gas density, which reduces turbulent airflow and promotes laminar flow.

139. How is the content of a gas-filled cylinder measured?  
By the pressure gauge; pressure is proportional to the volume of gas remaining.

140. How is the content of a liquid-filled gas cylinder measured?  
By weighing the cylinder; pressure does not indicate volume in liquid systems.

141. How is medical-grade air produced?  
By compressing and filtering atmospheric air to remove contaminants.

142. How often are safety tests required for compressed gas cylinders?  
Every 5 to 10 years, depending on the type of cylinder and regulatory requirements.

143. What are the safe storage practices for gas cylinders?  
Store upright, secured with chains or racks, away from heat, with caps in place; post “No Smoking” signs, and keep liquid oxygen in cool, ventilated areas.

144. What are the physical properties of nitric oxide?  
It is colorless, nonflammable, toxic, and supports combustion.

145. What are the physical properties of nitrous oxide?  
It is a colorless gas with a slightly sweet smell and taste.

146. What is the purpose of a central piping system in hospitals?  
To deliver medical gases at a standard working pressure (50 psi) throughout the facility.

147. What does a pressure-compensated Thorpe tube do?  
It ensures accurate flow readings despite changes in downstream resistance or back pressure.

148. What is the function of a flowmeter?  
To regulate and display the flow rate of gas being delivered to the patient.

149. What is the role of a reducing valve in gas delivery?  
It reduces high cylinder pressure to a safe, usable working pressure.

150. What is fractional distillation?  
A process of separating gases based on their boiling points, used to produce pure oxygen by cooling and compressing air, then collecting the oxygen as it condenses.

Final Thoughts

Medical gas therapy remains a cornerstone of respiratory care and emergency medicine, providing life-saving support to patients with compromised breathing or specific clinical needs.

From oxygen and helium mixtures to specialized gases used in anesthesia and diagnostics, each type plays a unique role in treatment. However, these therapies must be administered with care, following strict safety protocols to avoid complications such as oxygen toxicity or fire hazards.

By understanding the principles behind medical gas therapy and mastering proper delivery techniques, healthcare providers can ensure patients receive the maximum therapeutic benefit while minimizing risk. Ultimately, this knowledge contributes to more effective care and improved patient outcomes across various clinical settings.