Ventilation vs Oxygenation vs Respiration

Ventilation vs. Oxygenation vs. Respiration (2023)

by | Updated: Sep 23, 2023

The respiratory system is responsible for taking in oxygen and getting rid of carbon dioxide. This involves ventilation, oxygenation, and respiration.

But what exactly is the difference?

  • Respiration is the process of breathing that involves both ventilation and oxygenation.
  • Ventilation is the molecular exchange of gases in the body and involves the movement of air in and out of the lungs.
  • Oxygenation is the molecular absorbance of oxygen that involves the diffusion of oxygen molecules from environmental air into the bloodstream.

The process of respiration, which includes both ventilation and oxygenation, is vital to the overall health of the human body.

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What is Respiration?

Respiration is the physiological process of taking in oxygen from the environment during inhalation, while getting rid of carbon dioxide during exhalation.

This process is known as gas exchange and is a requirement for survival.

The air that enters the lungs during inhalation contains oxygen molecules that diffuse into arterial blood, which is pumped by the heart to the tissues of the body.

While this occurs, carbon dioxide molecules in the venous blood are transported to the lungs for removal during exhalation.

What is Ventilation?

Ventilation is the physiological process that involves the movement of air in and out of the lungs. It is a vital component of respiration and helps ensure that oxygen-rich air is brought into the lungs and carbon dioxide is expelled.

Carbon dioxide (CO2) is the primary parameter that is used to assess the process of ventilation. Carbon dioxide in the body is considered to be acidic, which is why it must be transported to the lungs for removal.

This phenomenon keeps the acidity in the body to a minimum and the blood pH within the normal range.

What is Oxygenation?

Oxygenation is the physiological process that involves the molecular absorbance of oxygen. When air enters the lungs, oxygen diffuses and is picked up in the hemoglobin of red blood cells.

Then is it transported and distributed to the organs and tissues of the body, which rely on oxygen in order to function properly.

While ventilation brings air into the lungs, it is oxygenation that helps ensure that the cells and body tissues receive enough oxygen molecules. When tissues are lacking oxygen, it results in a condition known as hypoxemia, which can be fatal if left untreated.

respiration inhalation exhalation process

Ventilation and Oxygenation Practice Questions:

1. What questions should you ask when assessing oxygenation?
Risk factors (familial, occupational, and environmental), fatigue, pain (chest, jaw, left arm), breathing patterns (dyspnea, orthopnea, wheezing), coughing, respiratory infections, and medication use.

2. Exposure to which substances are linked to respiratory disease?
Smog, cotton, dust, silicon, mold, cockroaches, secondhand smoke, and asbestos.

3. How would you describe pain originating in the heart?
It is most often substernal and typically radiates to the left arm and jaw in men. Some women, as well as some men, have epigastric pain, complaints of indigestion, nausea or vomiting, or a choking feeling and dyspnea.

4. If the patient doesn’t look good and doesn’t feel well, what is the first intervention you should do?
Take their vital signs.

5. How would you describe pericardial pain resulting from an inflammation of the pericardial sac?
It is usually non-radiating and often occurs with inspiration or when lying supine.

6. How would you describe pleuritic chest pain?
Peripheral and usually radiates to the scapular regions. Inspiratory maneuvers such as coughing, yawning, and sighing aggravates pleuritic chest pain. An inflammation or infection in the pleural space usually causes pleuritic chest pain. Patients often describe it as knifelike or sharp, and it increases in intensity with inspiration.

7. How would you describe musculoskeletal pain?
Musculoskeletal pain is often present following exercise, rib trauma, and prolonged coughing episodes. Inspiratory movements aggravate the pain and are easily confused with pleuritic chest pain.

8. What is dyspnea?
A subjective feeling of breathlessness as reported by the patient, or it can be observable labored breathing with shortness of breath.

9. What are symptoms of dyspnea?
Exaggerated respiratory effort, use of the accessory muscles of respiration, nasal flaring, and marked increases in the rate and depth of respirations.

10. What is dyspnea that occurs when a patient is sleeping?
Paroxysmal nocturnal dyspnea (PND).

11. What is wheezing?
A high-pitched musical sound caused by high-velocity movement of air through a narrowed airway. It is present in asthma, acute bronchitis, or pneumonia.

12. What is a productive cough?
One that produces sputum that is swallowed or expectorated.

13. What is hemoptysis?
Bloody sputum.

14. What do you call the ventilation where not all inspired air reaches the alveoli and 150 mL is stopped in the airway leading to the alveoli?
Deadspace ventilation.

15. What is the FiO2?
The concentration of oxygen in our inhaled air, which is referred to as the fraction of inspired oxygen.

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16. What may cause a pulse oximeter to not work?
Nail polish or poor circulation.

17. The main area to place a pulse oximeter is the finger, but where else can you place it if you are unable to obtain a good reading?
The earlobe or nose.

18. What happens to the chest wall with inspiration?
It moves out.

19. Inspiration is what kind of process?
An active process.

20. Expiration is what kind of process?
A passive process.

21. Inspiration is an active process that causes the brain to do what?
Send impulses down the phrenic nerve to initiate diaphragm contraction.

22. When assessing a patient’s respirations, what should you keep in mind?
The patient’s baseline, influence of any disease or illness, relationship with respiration in cardiac function, influences of any therapies on their respiration status.

23. What is bradypnea?
Decrease in respiratory rate.

24. What is tachypnea?
Increase in respiratory rate.

25. What is apnea?
Absence of breathing.

26. What is hyperventilation?
It is a state in which there is an increased amount of air entering the lungs.

27. What is hypoventilation?
It is breathing at an abnormally slow rate, resulting in an increased amount of carbon dioxide in the blood.

28. What is Cheyne-Stokes respirations?
A regular pattern of irregular breathing rate (often before patients die).

29. What is Kussmaul respirations?
Slow rapid respirations.

30. A 12-year-old female patient is having an asthma attack after participating in some strenuous activity during recess at school. She’s taken several doses of her own bronchodilator with little relief. Your partner immediately administers oxygen. Providing supplemental oxygen will increase the amount of oxygen molecules carried by what?
Carried by the hemoglobin in her blood, helping oxygenate critical organs like the brain.

31. What is the cause of hyperventilation?
Anxiety, infection, and drugs.

32. What are the treatments for hyperventilation?
Removal of the underlying problem, if anxiety related have them breathe into a paper bag.

33. What are the signs and symptoms of hyperventilation?
Excessive stimulation of respiratory center attempts to blow off carbon dioxide, increased anxiety, lightheadedness, and restlessness.

34. What are the causes of hypoventilation?
Drugs, inappropriate and ministration of O2 to COPD patients.

35. What are the signs and symptoms of hypoventilation?
Mental status changes, dysrhythmias, and potential cardiac arrest.

36. What are the treatments for hypoventilation?
Improved oxygenation, restored ventilation, treat underlining cause, and receive the acid-base balance.

37. What are the causes of hypoxia?
Impaired ventilation, poor tissue perfusion, decrease diffusion of O2 and alveoli to blood, and the inability of tissues to extract oxygen from the blood.

38. What is hypoxemia?
Low level of arterial oxygen in the blood.

39. What are the signs and symptoms of hypoxemia?
Restlessness, inability to concentrate, dizziness, and increased pulse rate.

40. What is the treatment for hypoxemia?
Administer oxygen entry underlining cause.

41. What is chest wall movement asymmetry?
Unequal expansion of lungs caused by a chest wall injury; i.e. a collapsed lung.

42. What are retractions?
Visible sinking in soft tissues of the chest that lies between and around firmer tissue (e.g., cartilage and bony ribs).

43. What is paradoxical breathing?
Asynchronous breathing and chest contraction during inspiration and expansion during expiration.

44. What normally triggers the respiratory drive by changing levels?
Carbon dioxide.

45. What do you call the volume of air that is moved in and out of the chest in a normal breath cycle?
Tidal volume.

46. What causes peripheral cyanosis?
Vasoconstriction and diminished blood flow and hypoxemia.

47. What causes central cyanosis?
Hypoxemia and/or hypoxia which is the late sign.

48. What causes decreased skin turgor?
Dehydration which is the normal finding in older adults as a result of decreased skin elasticity.

49. What causes dependent edema?
Heart failure.

50. What causes cyanosis of the nail beds?
Decreased cardiac output or hypoxia; sometimes the result of decreased circulation to affected limb or vasoconstriction secondary to cold.

51. What is the definition of the disruption of lung tissue by mechanical forces or medical problems can upset diffusion?
The process of gas exchange between the alveoli and the capillaries.

52. What causes clubbing of fingertips?
Chronic hypoxemia.

53. What causes pursed-lip breathing?
Chronic lung disease; increased respiratory effort.

54. How can oxygen be transferred?
Ventilation and perfusion.

55. What will happen if a person has low red blood cells?
Shortness of breath.

56. What causes pallor of the mouth and lips?

57. What causes distension of neck veins?
Heart failure (typically right-sided) and fluid overload.

58. What causes barrel chest?
COPD and may be a normal finding in older adults.

59. What is eupnea?
Breathing 12-20 breaths/min and normal in adults.

60. What is tachypnea?
It is breathing greater than 20 breaths/min. It resulted from anxiety, pain, fever, respiratory infection, or other causes that lead to respiratory distress. It can lead to respiratory alkalosis, paresthesia, tetany, and confusion.

61. What is apnea?
Periods of no respiration lasting greater than 20 seconds. Sometimes intermittent such as in sleep apnea or prolonged as in a respiratory arrest.

62. What are Kussmaul respirations?
Respiration usually greater than 35 breaths/min. Breaths deep in nature which is associated with metabolic acidosis state such as diabetic ketoacidosis.

63. What is Cheyne-Stokes respiration?
Periods of increasing depths of breathing followed by a period of apnea. It is seen in seriously ill patients, typically with brain injury or drug-associated respiratory distress. It may be seen in children and older adults during sleep.

64. What is ataxic or Biot’s respiration?
Irregular respirations of varying depths with irregular periods of apnea. It has poor prognosis and usually associated with severe brain injury.

65. What is neutral oxygenation?
The rhythm in depth between inspiration and expiration, the central nervous system controls rate and depth and rhythm.

66. What is chemical regulation for oxygenation?
The rate and depth based on the changes in carbon dioxide hydrogen and oxygen.

67. When a patient blows up too much CO2 do, they become basic or acidic?

68. What is dyspnea?
Difficulty breathing.

69. Where do crackles commonly found in the lungs?
Dependent lobes.

70. What is the treatment to crackles in the lungs?

71. Where is rhonchi heard?
Prime really heard over the trachea and bronchi.

72. What is rhonchi?
A sound caused by mucus in the large airways.

73 What are crackles?
Sounds caused by minor fluid accumulation.

74. What are wheezes?
High-pitched squeaking in the lungs that continues during inspiration and expiration.

75. What is an arterial blood gas?
An invasive procedure that sticks a needle an artery to tell the medical profession of the pH of the blood (this does not require consent).

76. What are the four different types of hypoxia?
Hypoxemic Hypoxia, Hystotoxic Hypoxia, Circulatory hypoperfusion stagnant hypoxia, and
Anemic hypoxia.

77. What is hypoxemic hypoxia?
The patient is hypoxic because they are hypoxemic.

78. What is hystotoxic hypoxia?
Oxygen can’t attach to the hemoglobin.

79. What are examples of hystotoxic hypoxia?
Carbon monoxide poisoning and cyanide poisoning.

80. How many times greater is affinity in carbon monoxide (CO) than in oxygen (O2) for hemoglobin?
200 times.

81. How do you treat CO poisoning?
100% NRB initially and then a hyperbaric chamber.

82. At what point do severe toxic effects start for CO poisoning?
When the levels get over 30%.

83. What are symptoms of severe toxic effects of CO poisoning?
A headache, lethargic, and arrhythmias.

84. At what level is CO poisoning fatal?
When it reaches over 50%.

85. What is the half-life of CO at room air?
3-4 hours.

86. What is the half-life of CO on 100% NRB?
40-60 minutes.

87. What is half-life?
The amount of time it takes for a substance to cut its amount in half.

88. What is the half-life of CO in a hyperbaric chamber?
15-20 minutes.

89. Does the pulse oximeter number have any value when the patient is suspected of having CO poisoning?

90. How do you measure CO on an ABG?
Co-ox or hemoximetry.

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91. What will the ABG look like in CO poisoning?
High PaO2 and low SaO2.

92. When should the patient stay on the NRB in CO poisoning?
When the CO is elevated.

93. What is a normal CO percentage in smokers?

94. What is circulatory hypoperfusion stagnant hypoxia?
The patient can’t get blood to the tissue because the blood pressure is too low to get it there.

95. What causes anemic hypoxia?
Low red blood cell (RBC).

96. What is A-a gradient also known as?
Alveolar-air equation.

97. What does the A stand for in A-a gradient?

98. What does the “a” stands for in A-a gradient?
Arterial PaO2 in the blood.

99. What is the formula for the A-a gradient?
PAO2= [FiO2 (PB-47)] – (PaCO2 X 1.25).

100. What is a normal A-a gradient?
Less than 25.

101. What is the indication of a huge difference between the oxygen in the alveoli and oxygen in the blood?
It indicates a huge problem at the AC membrane. The patient should be put on CPAP.

102. What do you do if the patient has a high level of oxygen in the alveoli and high level in the blood and is on a 100% NRB?
Lower FiO2 to 60% then continue to lower to keep stats at or greater than 90%.

103. Can the PaO2 be greater than the PAO2?
No, no it can’t.

104. What is a critical value for the A-a gradient and what do you do about it?
Greater than 450mm Hg with an Fi02 of greater than 60%. If the patient isn’t on a vent, then they should be.

105. How do you want your A-a gradient, high or low?

106. What indicates a bad A-a gradient?
A high gradient with a high Fi02.

107. What value should the P/F ration be?
Greater than 300.

108. What is a critical P/F value?
Less than 200 with an Fi02 greater than 60%.

109. Do you want a P/F ratio that is high or low?

110. What is the normal SpO2?

111. What is mild hypoxemia?

112. What is moderate hypoxemia?

113. What is severe hypoxemia?
85% or lower.

114. What is Kussmaul respirations?
Deep, slow or rapid, gasping breathing, and commonly found in diabetic ketoacidosis.

115. What is Cheyne-Stokes respirations?
Progressively deeper, faster breathing alternating gradually with shallow, slower breathing, and indicating brain stem injury.

116. What is Biot’s respirations?
An irregular pattern of rate and depth with sudden, periodic episodes of apnea, and indicating increased intracranial pressure.

117. What is Central neurogenic hyperventilation?
Deep, rapid respirations, and indicating increased intracranial pressure.

118. What are agonal respirations?
Shallow, slow, or infrequent breathing, and usually indicating brain anoxia.

119. What is snoring?
Results from partial obstruction of the upper airway by the tongue.

120. What is gurgling?
Results from the accumulation of blood, vomitus, or other secretions in the upper airway.

121. What is stridor?
A harsh, high-pitched sound heard on inhalation, associated with laryngeal edema or constriction.

122. What is wheezing
A musical, squeaking, or whistling sound heard in inspiration and/or expiration, associated with bronchiolar constriction.

123. What are crackles (rales)?
A fine, bubbling sound heard on inspiration, associated with fluid in the smaller bronchioles.

124. What is rhonchi?
A course, rattling noise heard on inspiration, associated with inflammation, mucus, or fluid in the bronchioles.

125. What hemoglobin (Hb) does SpO2 not distinguish but it reflects the amount of oxygen bound to hemoglobin?
Oxyhemoglobin, Carboxyhemoglobin, and Methemoglobin.

126. What percentage of oxygen is the patient receiving if they are breathing in room air?

127. In normal exhalation, the diaphragm and intercostal muscles relax to contract the chest, which creates a positive pressure. This is what type of process?

128. What does the pulse oximeter probe measure?
Pulsatile (arterial) blood flow at 2 different wavelengths.

129. Which 2 wavelengths does the SpO2 probe measure and what do they measure?
Oxyhemoglobin = 660 nm and Reduced hemoglobin = 940 nm.

130. Which 3 patients should get pulse oximetry?
Any hypoxemic patient, patients who need life monitors (critically ill or w/ circulatory deficits), and any patient under anesthesia.

131. What are the limiting factors for interpreting SpO2?
Poor perfusion (hypotension, hypothermia, peripheral vasoconstriction), dark pigmentation, motion, accuracy (probe must be in place for at least 30 sec, with good waveform/pulse form/HR), and dyshemoglobinemias will falsely elevate SpO2.

132. What are the normal values for ETCO2?
30-43 mmHg.

133. How does ETCO2 work?
Infrared light is passed through end-tidal air to a photo-detector. The detected light intensity is inversely proportional to the concentration of CO2 in the sample.

134. What are the two designs for ETCO2 detectors and how do they differ?
Mainstream = optical chamber located in the circuit. The other design is Side-stream = Sampling port is attached to a breathing circuit, and CO2 is desiccated and transported to the measurement chamber.

135. Which 4 groups of patients are at risk of ventilatory failure?
Cardiac, respiratory, NMJ, and neurologic patients.

136. Which 4 categories of patient selection exist for ETCO2 monitoring?
Patients at risk of ventilatory failure, Patients undergoing intermittent PPV, Anesthesia, and
Cardiopulmonary resuscitation patients.

137. Which 3 disturbances may cause an increase in ETCO2?
Hypoventilation increased metabolic rate (fever!), and IPPV (Increased cardiac output).

139. Which 3 disturbances may cause a decrease in ETCO2?
Hyperventilation, hypothermia, and IPPV (reduced CO).

140. What is the indication of the rise in both baseline and ETCO2?
Rebreathing of CO2.

141. What is the indication of a sudden fall in ETCO2?
Airway leakage or ventilator malfunction and IPPV for cardiac arrest.

142. Which sites can be used to get a sample for blood gas analysis?
Dorsal pedal artery, Femoral artery, and Lingual artery.

143. How many hours should an arterial blood sample for blood/gas analysis be analyzed or placed on ice?
1-2 hours.

144. What are 2 common sampling errors during arterial blood gas collection and how do they affect results?
Exposure to room air or bubbles, PaO2 will approach 150 mmHg and PaCO2 will decrease (increases pH values). Excess heparin will decrease pH, PaO2, and PaCO2.

145. Which blood gas variables are measured versus calculated?
Measured: pH, PaCO2, PaO2 and calculated: SaO2, Bicarb, CaO2.

146. What is the partial pressure of oxygen dependent upon?
The barometric pressure.

147. What do you call the potential space between the lung and chest wall?
The pleural space.

148. What are the 4 measurements of oxygenation?
PaO2 (Partial pressure of O2 in arterial blood), alveolar-arterial O2 difference (A-a), 5 x FiO2, and partial pressure of O2:FiO2 (PaO2/FiO2).

149. What is PaO2 and what is the cutoff value for hypoxemia?
Partial pressure of oxygen in arterial blood. PaO2 < 85-90 mmHG = hypoxemia.

150. What is the A-a and what is the Alveolar Gas Equation it follows?
A-a = Difference in oxygen tension between the alveolus (A) and the artery (a). Mean alveolar PO2 (PAO2) = FiO2 (Barometric pressure – Water vapor) – (PaCO2/0.8).

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151. What values do we follow for A-a?
Less than 10 = normal for patient breathing room air and greater than 30 = abnormal for patient breathing room air.

152. What is FiO2x5 and why do we make this calculation?
Anticipated value for PaO2 based on the fraction of inspired air that the patient is breathing
Expected PaO2 = FiO2 X 5

153. What are the normal ratios for PaO2/FiO2?
If ratio is > 500, = NORMAL. If ratio is < 300, = significant defect in gas exchange.

154. What are the normal values for PaCO2?
PaCO2 < 36 mmHg: Hypocapnia (respiratory alkalosis) and hyperventilation. While PaCO2 > 45 mmHg: Hypercapnia (respiratory acidosis) and hypoventilation.

155. What are the typical normal values for pH, PCO2, and PaO2 on blood gas?
pH = 7.35-7.45, PCO2 = 35-45, and PaO2 = 90-100.

156. What causes the sympathetic nervous response to occur?
Breathe faster and deeper, blood vessels to constrict, heart to beat stronger and faster, skin to sweat, pupils to dilate, and skin to become pale.

157. What would be the minute volume if a patient is having difficulty breathing and her current tidal volume is 350 mL, and she is breathing at 28 times per minute?
9,800 mL.

158. Our blood transports oxygen from the lungs to the cells and returns with what byproduct of metabolism?
Carbon dioxide.

159. What is the best description of the chest’s mechanical functions?
The chest is a closed space with only one opening; the trachea, to inspire air; the diaphragm contracts down and the intercostal muscles expand the ribs, causing a negative pressure that fills the lungs with air.

160. What is the correct order of air flow from the nose to the alveoli in the lungs?
Nose, nasopharynx, pharynx, hypopharynx, larynx, trachea, bronchi, and alveoli.


What is the Difference Between Ventilation and Oxygenation?

Ventilation and oxygenation are fundamentally different physiological processes. Ventilation refers to the patient’s ability to take in oxygen and remove carbon dioxide.

Oxygenation refers to the patient’s ability to take in oxygen from the lungs and distribute it to the tissues and organs of the body.

Capnography can be used to monitor the patient’s ventilation status, whereas, pulse oximetry can be used to monitor their oxygenation status.

pulse oximetry for oxygenation

Does Ventilation Affect Oxygenation?

Yes, ventilation can affect oxygenation. When a patient is having difficulty breathing, it can lead to a decrease in oxygen saturation levels. This is because the lungs are not able to take in as much oxygen and carbon dioxide builds up in the blood.

If left untreated, this can lead to serious health complications that stem from respiratory or ventilatory failure.

What is the Difference Between Ventilation and Breathing?

Breathing is the process of taking in air and exchanging gases in the lungs. Ventilation is a vital component of respiration that refers to the movement of air in and out of the lungs.

While breathing is necessary for survival, ventilation helps ensure that oxygen-rich air is brought into the lungs and carbon dioxide is expelled.

What is Perfusion?

Perfusion is the process of blood circulating through the body. It is responsible for delivering oxygen and nutrients to the cells, tissues, and vital organs.

When blood flows to the alveolar capillaries, it picks up oxygen molecules for transport. Therefore, for the body to obtain oxygen, there also must be sufficient amounts of blood being perfused through the lungs.

What is the Difference Between Ventilation and Perfusion?

Ventilation and perfusion are two important physiological processes that work together to ensure proper respiration. Ventilation is responsible for bringing air into the lungs and expelling carbon dioxide.

Perfusion is responsible for delivering oxygenated blood to the tissues and organs of the body. Therefore, if either ventilation or perfusion is lacking, the tissues of the body will not receive an adequate amount of oxygen molecules.

Final Thoughts

Ventilation, oxygenation, and respiration are all vital processes that work together to ensure the overall health of the human body. Each process plays an important role in gas exchange and keeping the blood pH within a normal range.

While ventilation brings air into the lungs, it is oxygenation that helps ensure that the cells and body tissues receive enough oxygen molecules.

If you enjoyed this article, we have a similar guide on gas exchange that I think you’ll find helpful. Thanks for reading!

Written by:

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.


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  • Cardiopulmonary Anatomy & Physiology: Essentials of Respiratory Care. Cengage Learning, 2019.
  • “Essentials of Airway Management, Oxygenation, and Ventilation: Part 1: Basic Equipment and Devices.” National Center for Biotechnology Information, 2014,
  • Rozanski, Elizabeth. “Oxygenation and Ventilation.” PubMed, Apr. 2014,
  • “Anatomy and Physiology of Respiratory System Relevant to Anaesthesia.” PubMed Central (PMC), 1 Sept. 2015,

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