Ventilation is the process of moving air in and out of the lungs. Alveolar Ventilation has the same meaning except it specifically focuses on the process that takes place in the alveoli of the lungs.
As a Respiratory Therapist, it’s extremely important to develop an understanding of the properties and physiology of the respiratory system. Hopefully, this guide can help make the learning process easier for you. So if you’re ready, let’s get started.
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What is Alveolar Ventilation?
Alveolar Ventilation refers to the ventilatory process that takes place in the alveoli of the lungs. This is where the body is able to take in oxygen and remove carbon dioxide.
It can be calculated by multiplying the breathing frequency by the alveolar tidal volume per breath.
Alveolar Ventilation = Frequency x Alveolar Tidal Volume
The efficiency of alveolar ventilation relies on the amount of gases that reach the alveoli.
For example, if alveolar ventilation increases, the lungs would remove too much CO2 causing the PaCO2 to decrease. This is known as hyperventilation and results in an increased pH (respiratory alkalosis).
Properties of Ventilation Practice Questions:
1. What is internal respiration?
It is the gas exchange between systemic capillaries and cells.
2. What is external respiration?
It is the gas exchange between pulmonary capillaries and the alveoli.
3. What is respiration?
It is the exchanges of gases providing the blood and tissues with oxygen and removing excess carbon dioxide.
4. What does ventilation mean?
It is the process of taking air into the lungs and expelling it into the atmosphere.
5. What does barometric pressure mean?
It is the force exerted by the air that surrounds the body.
6. What is the normal range for barometric pressure?
It is 760mmHg or 1033cmH2O
7. What is the difference between atmospheric pressure and barometric pressure
There is no difference between the two.
8. What is a pressure gradient?
It is the change in pressure between 2 points.
9. What causes airflow?
The change in pressure gradient from outside the body to the alveoli and from lungs requires a pressure gradient change in the opposite direction.
10. What causes the pressure gradient change during respiration?
11. What is Boyle’s Law?
As the volume in an airtight container decreases, the pressure in the container will increase accordingly.
12. What is the pressure gradient at end expiration?
13. What does the normal pleural pressure change during quiet breathing?
14. What is driving pressure?
It is the pressure difference between 2 points in a tube or vessel.
15. What is the transthoracic pressure?
It is the difference between alveolar pressure and body surface pressure. Technically, there is no real difference between the trans respiratory pressure and transthoracic pressure.
16. What measures the elastic forces of the lungs?
17. How is lung compliance determined?
It can be determined by the change in volume divided by change in pressure.
18. What is a tension pneumothorax?
It is too much force for lungs elastic capability can cause rupture.
19. How does the iron lung work?
It is like a piston pump that generates negative pressure simulating reap cycle.
20. What is surface tension?
It is a molecular cohesive force at the liquid-gas interface.
21. What is Laplace’s Law?
It is the distending pressure of bubble which depends on surface tension and
size of the bubble.
22. What is pulmonary surfactant composed of and how does it work?
It is composed of 90% phospholipids and 10% protein. It also decreases surface tension in fluids increasing the exchange of gases in alveoli.
23. What does Dynamic mean?
It is the forces in action causing pressure changes required to move gas in and out of the lungs.
24. What is Poiseuille’s Law?
It is directly proportional to pressure and inversely proportional to viscosity.
25. What is the normal airway resistance in the tracheobronchial tree?
26. What is the difference between dynamic compliance and lung compliance?
27. As airway resistance increases, what happens to the respiratory rate and tidal volume?
Respiratory rate decreases and volume increases.
28. What is a normal tidal volume?
For an ideal body weight, it is 3-4mL/lb. with average 500ml.
29. What is dead space ventilation?
It is the portion of inspired air that does not reach the alveoli for gas exchange.
30. What are the 3 types of dead space ventilation?
a) Anatomic dead space is when airway from nose to but not on bronchioles.
b) Alveolar is not perfumes with pulmonary blood lowering gas exchange.
c) Physiologic which is the combination of anatomic and alveolar dead space.
31. What is the formula for minute alveolar ventilation?
Va = (Vt – Vd) x breaths/minute
32. What is Biot’s respirations?
It is the short episodes of rapid uniformly deep inspiration followed by 10-30 sec apnea.
33. What is tachypnea?
It is the rapid shallow ventilatory pattern.
34. What is hyperpnea?
It is the increase in depth with or without
35. What is hyperventilation?
It is the Increase in rate and/or increase in depth that leads to
36. What is hypoventilation?
It is the decrease in rate or in depth.
37. What is orthopnea?
It is the ability to breathe only in an upright position.
38. What is dyspnea?
It is the difficulty in breathing of which individual is aware of.
39. What is Cheyne-Stokes?
It is the gradual increase and decrease in the volume and rate of breathing followed by 10-30 seconds of apnea.
40. What is Kussmaul breathing?
It is the increase in rate and depth.
41. What are the 4 things that a Respiratory Therapist must know to fully understand the process of ventilation?
a.) The mechanisms of pulmonary ventilation
b.) The elastic properties of the lungs and chest wall
c.) The dynamic characteristics of the lungs and how they affect ventilation
d.) The characteristics of normal and abnormal ventilator patterns
42. What is the mechanism of pulmonary ventilation that create a pressure gradient?
Primary principals of ventilation
43. What is ventilation?
It is the process that moves gases between the external environment and alveoli.
44. What is compliance?
It is the ability to stretch.
45. What is elasticity?
It is the ability to snap back to place.
46. What is Dalton’s law?
It is the sum of partial pressures exerted by all gases in the atmosphere equals the barometric pressure.
47. If the PO2 is 100 mmHg at one barometric pressure (760 mmHg), what is the approximate PO2 if the pressure is increased to 1,520 mm Hg in a hyperbaric chamber?
48. What is Charles’s law?
It is when gas volume varies with the temperature at constant pressure.
49. What is Kelvins?
It is when using gas law equations, the temperature must first be converted.
50. What are pressure gradients?
It is the pressure difference from one point to another.
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51. What are the primary principles of ventilation?
Mechanisms of pulmonary ventilation that create a pressure gradient.
52. What makes a bronchoconstriction cause a very large increase in the work of breathing?
The changes in the radius of the airway.
53. In the Poiseuille equation, it shows that when the radius of the airway decreases by half the driving pressure must increase. How many times is needed to maintain the same flow rate?
54. What is atmospheric pressure?
It is also known as barometric pressure.
55. What is barometric pressure?
It is the force exerted by the air that surrounds the earth and the body.
56. What is the sea level under standard conditions (the Barometric pressure)?
57. What is a barometer?
It is an instrument used to measure P(am).
58. What is a pressure gradient?
It is the general term for a pressure difference between two points in a system.
59. What is expiration?
It is when the intra-alveolar pressure is higher than the atmospheric pressure at the point in the ventilatory cycle.
60. What gas law states that constant temperature and a volume of gas varies inversely proportional to its pressure?
61. At what point in the respiratory cycle can equilibrium point be reached?
End- inspiration and end-expiration
62. What are intercostal retractions?
It is a general term for the inward movement of tissue between the ribs during inspiration due to increase negative intrapleural pressure generated during respiratory distress. It is also the force required to move gas or fluid through a tube or vessel driving pressure.
63. What is transmural pressure?
It is the difference between the alveolar pressure and the pleural pressure.
64. What is transthoracic pressure?
It is the difference between the alveolar pressure and the body surface pressure.
65. What is lung compliance?
It is a clinical measurement used to evaluate the elastic forces of the lungs.
66. How does air trapping and hyperinflation of the lungs affect lung compliance?
Lung compliance is reduced.
67. How do obstructive lung diseases (that cause air trapping) affect lung compliance?
Lung compliance is reduced with obstructive lung diseases.
68. What effect do restrictive lung diseases have on lung compliance?
Lung compliance decreases.
69. Which would shift the volume-pressure curve to the right?
Its pneumothorax, pleural effusion, and pulmonary edema.
70. When a positive pressure breath is delivered from a mechanical ventilator, how would intra-alveolar and intrapleural pressures be affected during inspiration?
Both will increase.
71. When a tension pneumothorax occurs during positive pressure ventilation, how will the cardiac output and blood pressure be affected?
Both will decrease.
72. What law best explains the basic operation of the negative pressure ventilator?
73. What is surface tension?
It is a term for the molecular cohesive force at a liquid-gas interface.
74. What is pulmonary surfactant?
It is the substance in the alveoli responsible for lowering the surface tension.
75. Which can cause pulmonary surfactant deficiency?
Pulmonary embolism, pulmonary edema, atelectasis, and ARDS.
76. What is derived when the pressure difference between the mouth and the alveoli is divided by the flow rate?
77. What is laminar flow?
It is when the flow pattern that occurs in the airways at low flow rates and pressure gradients.
78. What is turbulent flow?
It is when the flow pattern occurs in the airways at high flow rates and high-pressure gradients.
79. What is a time constant?
It is defined as the “time required to inflate a lung region to 60% of its filling capacity”.
80. When lung compliance is reduced, how will time constants be affected?
The time constants will be reduced by half.
81. What is dynamic compliance?
It is defined as “the change in volume in the lungs divided by the change in transpulmonary pressure during the time required for one breath”.
82. How do patients typically offset the decrease time constants when they adopt an increased respiratory rate in the presence of restrictive lung disorders?
They decrease their respiratory rate and increase their tidal volume.
83. What changes in breathing patterns do patients with obstructive pulmonary disorders, increased airway resistance, and increased time constants typically adopt?
84. What is the term for the condition in which positive pressure remains in the alveoli during exhalation due to the insufficient expiratory time when rapid ventilatory rates occur?
Tidal volume is the term for the volume of gas that is typically measured during exhalation on one quiet breath.
85. What is the average respiratory rate for adults at rest?
86. When the end-expiratory pause is factored in, what is the normal I
87. What is the average respiratory rate for a healthy toddler at rest?
88. What are the boundaries of anatomic dead space?
Nose and mouth through the terminal bronchioles.
89. What is the approximate volume of anatomic dead space?
1mL/lb. of ideal body weight
90. What is alveolar dead space?
It is a term for alveolar ventilation without pulmonary capillary perfusion.
91. What is physiologic dead space?
It is the sum of anatomic dead space and alveolar dead space.
92. How would the addition of the length of tubing between a ventilator and the endotracheal tube effect the dead space?
It prolongs inactivity during pregnancy, childbirth, obesity, and hypercoagulation disorders which can cause pulmonary emboli.
93. Which portion of the lungs has the most negative pleural pressure in the upright position?
94. In the upright lung, how does compliance vary across the lung?
5%. The compliance in the apices is lower than the bases.
95. What is ventilatory efficiency?
It is the alteration of the ventilatory pattern to minimize dead space ventilation. The respiratory rate increases and tidal volume decreases.
96. How does the normal adult respiratory pattern change when the lung compliance decreases?
Respiratory rate increases.
97. What does apnea mean?
It is a ventilatory pattern defined as the complete absence of spontaneous breathing.
98. What is Biot’s breathing?
Breathing condition in which short episodes of rapid, uniform deep breaths are followed by 10-30 seconds of apnea.
99. What is tachypnea?
It is a rapid respiratory rate.
100. What is hyperpnea?
It is the breathing pattern in which the depth of breathing increases.
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101. In which breathing pattern is an individual only able to breathe comfortably in the upright position?
102. Which abnormal breathing pattern is most commonly associated with ketoacidosis?
It is Kussmaul breathing.
103. What is the only absolute way of confirming hyperventilation?
Rapid breathing which exhaling is more than inhaling.
104. What is ventilation?
It is a mechanism by which oxygen is carried from the atmosphere to the alveoli and by which carbon dioxide is carried from the alveoli to the atmosphere.
105. What is the pressure difference in pulmonary physiology?
106. Describe Boyle’s Law?
It states that a volume of
107. What is the driving pressure?
It is the pressure difference between two points in a tube or vessel and it is also the force moving gas or fluid through the tube or vessel.
108. What is the transrepiratory pressure?
It is the difference between the barometric pressure and the alveolar pressure.
109. What is the transmural pressure?
It is the pressure difference that occurs across the airway wall subtracting the intra-airway pressure from the pressure on the outside of the airway.
110. What is positive transmural pressure?
It exists when the pressure within the airway is greater than the pressure outside of the airway.
111. What is negative transmural pressure?
It exists when the pressure outside the airway is greater than inside the airway.
112. What is transpulmonary pressure?
The difference between the alveolar pressure and the pleural pressure.
113. What is transthoracic pressure?
The difference between the alveolar pressure and the body surface pressure.
114. How does the chest wall move on a natural tendency?
Outward or to expand.
115. How do the lungs move on their natural tendency?
Inward or collapse.
116. What is the technical definition of lung compliance?
It is the change in lung volume per unit pressure.
117. What is the definition of elastance?
The natural ability of matter to respond directly to force and to return to its original resting position or shape after the external force no longer exists.
118. What is Hooke’s Law?
It states that when a truly elastic body like a spring acted on by one unit of force, the elastic body will stretch 1 unit of length. And when it acted on by 2 units of force, it will stretch 2 units of length.
119. What is surface tension?
Distending pressure of a liquid bubble is influenced by the surface tension of the bubble and the size of the bubble itself.
120. What is Laplace’s Law?
It is a molecular, cohesive force at the liquid-gas interface. It shows the distending pressure of a liquid sphere directly proportional to the surface tension of the liquid and inversely proportional to the radius of the sphere.
121. What is the critical opening pressure?
The principles of Laplace’s law do not come into effect until the distending pressure of the liquid sphere goes beyond.
122. What is the composition of pulmonary surfactant?
It is composed of 90% phospholipids and 10% protein.
123. What is airway resistance?
It is the pressure difference between the mouth and the alveoli divided by flow rate.
124. What is laminar gas flow?
It is the gas molecules that move through a tube in a random manner.
125. What is dynamic compliance?
It is the product of the time constant. It is also the change in volume of the lungs divided by the change in the transpulmonary pressure during the time required for one breath.
126. What does frequency dependent mean?
It refers to compliance of alveoli, – the alveoli distal to the obstruction do not have enough time to fill to their potential filling capacity as the breathing frequency increases.
127. What is the definition of tidal volume?
It is the volume of air that normally moves into and out of the lungs in one quiet breath.
128. What is the tidal volume of a normal adult patient?
5-7 ml/kg of the ideal body weight (IBW).
129. What is alveolar ventilation?
It is the only inspired air that reaches the alveoli and is effective in terms of gas exchange.
130. What is anatomic dead space?
It is the volume of gas in the conducting airways: nose, mouth, pharynx, larynx and lower airways but not the respiratory bronchioles.
131. What is eupnea?
It is the normal and spontaneous breathing.
132. What is Cheyenne-Stokes breathing?
It is the 10-30 seconds of apnea, followed by a gradual increase in the volume and frequency of breathing. Followed by a gradual decrease in the volume of breathing until another period of apnea occurs.
133. What is Kussmaul’s breathing?
It is both an increased depth and rate of breathing.
134. What are the 2 primary functions of the lungs?
To supply the body with oxygen and to remove CO2.
135. What are the 2 phases of ventilation?
Inspiration and expiration.
136. What is tidal volume?
The volume of air that is inhaled or exhaled from the lungs during effortless breathing.
137. What is a positive pressure?
Pressure that is greater than atmospheric pressure.
138. What is a negative pressure?
Subatomic pressures less than 1 atmosphere.
139. What are the 3 important pressure gradients involved in ventilation?
Transrespiratory, transpulmonary, and transthoracic.
140. What does the transrespiratory pressure represent?
It represents the difference between the atmosphere (body surface) and the alveoli.
141. What does the transrespiratory pressure cause to happen?
It causes gas to flow in and out of the alveoli during breathing.
142. What does the transpulmonary pressure represent?
It represents the pressure difference between the alveoli and the pleural space.
143. What does the transpulmonary pressure cause to happen?
It helps to maintain alveolar inflation. Transpulmonary pressure results from the opposing elastic recoils of the thorax and lungs themselves.
144. What does the transthoracic pressure represent?
It represents the difference in pressure between the pleural space and the body surface. It is the pressure across the chest wall. It represents the total pressure needed to expand or contract the lungs and chest wall together.
145. What happens as inspiration begins?
Muscular effort expands the thorax. This causes a decrease in pleural pressure. Transpulmonary pressure gradient widens, causing the alveoli to expand, which causes a negative transrespiratory pressure and air enters the lungs.
146. What happens as expiration begins?
The thorax recoils and transpulmonary pressure starts to rise. Alveolar pressure rises. The transpulmonary pressure narrows and the alveoli begin to deflate. Alveolar pressure exceeds that at the airway opening.
147. What is another name for barometric pressure?
148. In order to generate pressure gradients the lungs must be what?
They must be distended.
149. In order to increase lung volume, what must be applied?
150. The amount of inflation or stretch is measured as a volume by what?
It is measured with a spirometer.
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151. The recoil of the lung is a combination of what 2 things?
Tissue elasticity and surface tension.
152. During inflation, additional pressure is needed to overcome what?
153. What type of cells produce pulmonary surfactant?
Alveolar type II cells.
154. What is compliance?
Volume changed per unit in applied pressure.
155. What does compliance measure?
It measures the distensibility of the lung.
156. Compliance is measured under what conditions?
Static conditions (no airflow).
157. The measurement of pulmonary compliance in a patients requires the placement of what?
A balloon-tipped catheter in the esophagus.
158. What does the compliance curve of a patient with emphysema look like?
It is steeper and displaced to the right. Large changes in volume for small pressure changes (increased compliance due to loss of elastic fibers).
159. What does the compliance curve of a patient with pulmonary fibrosis look like?
It is flatter than a normal curve and is shifted down and to the right. Smaller volume change for any given pressure (decreased compliance, lungs become stiffer with a reduced volume).
160. What is FRC?
The resting volume of the lungs. It is the point at which the alveolar pressure equals atmospheric pressure.
161. What happens if the normal relationship of the chest wall is disrupted?
The lung tends to collapse to a volume less than the FRC, and the thorax expands to a volume larger than the FRC.
162. The tendency of the chest wall to expand is offset by what?
The contractile force of the lungs.
163. Diseases that alter the compliance of either the chest wall or lung often disrupt the balance point usually with a change in what?
164. Inhalation occurs when the balance btw the lungs and the chest wall does what?
165. At the beginning of the breath, the tendency of the chest wall to expand facilitates what?
It facilitates lung expansion.
166. What diseases can reduce chest wall compliance and lung volumes?
Obesity, kyphoscoliosis, and other restrictive diseases.
167. The total compliance of the respiratory system equals?
Lung compliance plus the compliance of the thorax.
168. What are 2 ways to measure lung thorax compliance?
Placing a relaxed or anesthetized subject in a body respirator. OR, in an intubated patient with a cuffed endotracheal tube by using positive pressures.
169. How can the total compliance of the respiratory system be altered?
By the position of the patient as well as disorders affecting the compliance of the lungs, chest wall, or both.
170. What is airway resistance?
The impedance to ventilation by the movement of gas through the airways.
171. Airway resistance accounts for how much of the frictional resistance to ventilation?
172. What is the range for airway resistance in healthy adults?
0.5–2.5 cm H2O.
173. How is airway resistance measured (Flow)?
With a pneumotachometer.
174. How are alveolar pressures determined in the body?
With a plethysmograph.
175. How much of the resistance to gas flow occurs in the nose, mouth, and large airways?
176. How much of the total resistance to flow is attributed to airways smaller than 2 mm in diameter where flow is mainly laminar?
177. Airway caliber is determined by what factors?
Anatomic support provided to the airways, and pressure differences across their walls.
178. What do the larger airways mainly depend on for support?
179. What do the smaller airways mainly depend on for support?
The surrounding lung parenchyma.
180. When does dynamic airway compression occur in a healthy adult?
Only at lung volumes well below the resting expiratory level.
181. Destruction of elastic tissue does what to the compliance of the lung?
It increases the compliance of the lung.
182. Assessment of mechanical work of breathing involves the measurement of what?
Physical parameters of force and distance as they relate to moving air in and out of the lungs.
183. Assessment of metabolic work involves the measurement of what?
Oxygen cost of breathing.
184. How to calculate mechanical work of breathing?
WOB = change in pressure*change in volume
185. When can total mechanical work be measured?
During artificial ventilation if the respiratory muscles are completely at rest.
186. In the presence of a pulmonary disease, the work of breathing will do what?
It will increase dramatically.
187. Large tidal volumes do what to the elastic component of work in mechanical work of breathing?
Increases the elastic component of work.
188. High breathing rates do what to the frictional work in mechanical work of breathing?
Increases the frictional work.
189. Patients with pulmonary fibrosis often assume what breathing pattern?
A rapid, shallow breathing pattern. This pattern minimizes the mechanical of distending the lungs but at the expense of more energy to increase breathing rate.
190. Patients with obstructive disease often assume what breathing pattern?
Breathing slowly using pursed lip breathing during exhalation to minimize airway resistance.
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191. When increased work of breathing occurs with respiratory muscle weakness, what happens to the inspiratory muscles?
They become fatigued. The tidal volume decrease and the respiratory rate increases.
192. How is the oxygen cost of breathing assessed?
By measuring the rate of oxygen consumption at rest and at increased levels of ventilation.
193. What is the average oxygen cost of breathing in an individual?
0.5–1.0 mL of oxygen per liter of increased ventilation.
194. The rate of oxygen consumption by the respiratory muscles is closely related to what?
The inspiratory pressures generated by the diaphragm.
195. Abnormally high oxygen cost of breathing is one factor that limits exercise in what type of patients?
Patients with obstructive disease such as emphysema.
196. Increased oxygen consumption by the respiratory muscles may also contribute to what when dealing with mechanical ventilation?
Failure to wean patients off the ventilator.
197. Is ventilation distributed evenly in the lungs?
No, no it is not.
198. What 2 factors account for the unevenness in the distribution of ventilation?
Regional and local factors.
199. What are the regional factors in the distribution of ventilation?
Relative differences in thoracic expansion, and regional transpulmonary pressure gradients.
200. The thorax and respiratory muscles cause greater expansion where?
At the lung bases.
So there you have it. As you can see, the topic of alveolar ventilation and pulmonary physiology is very complex. With that said, is it a subject that each and every Respiratory Therapist must learn and understand.
Hopefully, this guide can help make that process easier for you. We have a similar study guide on Gas Exchange that I think you will enjoy. Thank you so much for reading and as always, breathe easy my friend.
- Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020. [Link]
- Jardins, Des Terry. Cardiopulmonary Anatomy & Physiology: Essentials of Respiratory Care. 7th ed., Cengage Learning, 2019. [Link]
- Intagliata, Sal. “Physiology, Lung Dead Space – StatPearls – NCBI Bookshelf.” National Center for Biotechnology Information, U.S. National Library of Medicine, 2 Sept. 2020, www.ncbi.nlm.nih.gov/books/NBK482501.
- Hoffman, A. “Comparison of Alveolar Ventilation, Oxygenation, Pressure Support, and Respiratory System Resistance in Response to Noninvasive versus Conventional Mechanical Ventilation in Foals.” PubMed, Dec. 1997, pubmed.ncbi.nlm.nih.gov/9401700.
- “Physiology, Pulmonary Ventilation and Perfusion.” National Center for Biotechnology Information, U.S. National Library of Medicine, 29 Sept. 2020, www.ncbi.nlm.nih.gov/books/NBK539907.
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