Question Answer
What are the 2 primary functions of the lungs? supply the body with O2, remove CO2
Ventilation process of moving gas in and out of the lungs
What are the 2 phases of ventilation? inspiration and expiration
Tidal volume volume of air that is inhaled or exhaled from the lungs during effortless breathing
Equation for determining ventilation Pressure=Volume ——-+(Resistance*Flow) compliance
What is a positive pressure? one that is greater than atmospheric pressure
What is a negative pressure? subatomic pressures less than 1 atmosphere
Pressure gradient difference between 2 pressures
What are the 3 important pressure gradients involved in ventilation? transrespiratory, transpulmonary, transthoracic
What does the transrespiratory pressure represent? the difference btw the atmosphere (body surface) and the alveoli
What does the transrespiratory pressure cause to happen? gas to flow in and out of the alveoli during breathing
What does the transpulmonary pressure represent? the pressure difference btw the alveoli and the pleural space
What does the transpulmonary pressure cause to happen? mintains alveolar inflation. Transpulmonary pressure results from the opposing elastic recols of the thorax and lungs themselves.
What does the transthoracic pressure represent? difference in pressure btw 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.
Before inspiration waht is the pleural pressure at in cm of H2O? -5
Before inspiration what is the alveolar pressure in cm of H2O? 0
Describe the what happens as inspiration begins. Muscular effort expands the thorax. This causes a decrease in pleural pressure. Transpulmonary pressure gradient widens, causing alveoli to expand. Causing a negative transrespiratory pressure and air enters
Describe what happens as expiration begins Thorax recoils and transpulmonary pressure starts to rise. Alveolar pressure rises. Transpulmonary pressure narrows and alveoli deflate. Alveolar pressure exceed that at the airway opening.
To generate pressure gradients the lungs must be? distended
What are the two categories of forces opposing lung inflation? elastic forces, frictional forces
Elastic forces? involve tissures of the lungs and thorax and surface tension in alveoli
Frictional forces? resistance caused by gas flow and tissure movement during breathing
Elasticity physical tendency of an object to return to an initial state after defomation
In the lung inflation is equivalent to? stretching
What opposes inflation? lung elastic forces
To increase lung volume what must be applied? pressure
The amount of inflation or stretch is measure as a volume by a? spirometer
What happens to the inflation vurve as the lung is stretched to it’s maximum? becomes flat
What does the flattening indicate? increasign opposition to expansion
hysteresis difference btw the inflation and deflation curves
What does hysteresis indicate? factors other than simple elastic tissure forces are present
Part of the hysteresis exhibited by the lung is a result of? surface tension forces in the alveoli
Less or more pressure is needed to inflate a fluid filled lung to a given volume? Less pressure is needed
The recoil of the lung is a combination of what 2 things? tissue elasticity, and suface tension forces in the alveoli
During inflation additional pressure is needed to overcome what? surface tension forces
Pulmonary surfactant phospholipid that lowers surface tension in the lung
What type of cells produce pulmonary surfactant? Alveolar type II cells
Compliance volume changed per unit in applied pressure.
What does compliance measure? distensibility of the lung
Formula for compliance CL=change in the volume (Liters) ———————– change in the pressure (cm H20)
Compliance of a healthy adult lung averages? 0.2L/cm H2O or 200ml/cm H2O
Compliance is measured under what conditions? static (no airflow)
Measurement of pulmonary compliance in a patients requires the placement of what? balloon tipped catheter in the espohagus
What does the compliance curve of a patient with emphysema look like? steeper and displaced to the right. large changes in volume for small pressure changes (increased compliance due to loss of elastic fibers)
What does the compliance curve of a patient with pulmonary fibrosis look like? flatter than normal curve and shifted down to the right. smaller volume change for any given pressure(decreased compliance, lungs become stiffer with a reduced volume)
FRC resting volume of the lungs. point at which alveolar pressure equals atmospheric pressure.
Normal FRC 40% of total lung capacity
What happens if the normal relationship of the chest wall is disrupted? the lung tents to collapse to a volume less than FRC, and the thorax expand to a volume larger than the FRC
The tendency of the chest wall to expand is offset by what? the contractile force of the lungs
Diseases that alter the compliance of either the chest wall or lung often disrupt the balance point usually with a change in what? lung volume
Inhalation occurs when the balance btw the lungs and the chest wall do what? shifts
At the beginning of the breath the tendency of the chest wall to expand facilitates what? lung expansion
What diseases can reduce chest wall compliance and lung volumes? obesity, kyphoscoliosis, ankylosing spondylitis
The total compliance of the respiratory system equals? lung compliance plus the compliance of the thorax
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.
How can the total compliance of the respiratory system be altered? By the position of the patient as well as disorders affedting compliance of the lungs, chest wall or both.
Frictional (nonelastic) opposition to ventilation has the following 2 components? tissue viscous resistance, and airway resistance
What is tissure viscous resistance? impedance of motion caused by displacement of tissues during ventilation
In tissue viscous resistance what tissues are displaced? lungs, rib cage, diaphragm, and abdominal organs
Tissue viscous accounts for how much total resistance to lung inflation? 20%
What diseases can alter tissue viscous resistance, increasing total impedance to ventilation? obesity, fibrosis, ascites
What is airway resistance? impedance to ventilation by movement of gas through airways
Airway resistance accounts for how much of the frictional resistance to ventilation? 80%
what is the formula for airway resistance? Raw=Palv-Pao ——– V
What is the range for airway resistance in healthy adults 0.5-2.5cm H2O
How is airway resistance measured (Flow)? pneumotachometer
Hw are alveolar pressures determined in the body? plethysmograph
How much of the resistance to gas flow occurs in the nose, mouth , and large airways? 80%
How much of the total resistance to flow is attributed to airways smaller than 2 mm in diameter where flow is mainly laminar? 20%
Airway caliber is determined by what factors? anatomic support provided to the airways, and pressure differences across their walls
What do the larger airways mainly depend on for support? cartilage
What do the smaller airways mainly depend on for support? surrounding lung parenchyma
transmural pressure gradient difference between the pleural pressure and the pressure inside the airway
Equal pressure point pressure inside equals the pressure outside in the pleural space
dynamic compression of the airways narrowing of the airways due to an increase in surrounding pressures
When does dynamic airway compression occur in a healthy adult? only at lung volumes well below the resting expiratory level
Destruction of elastic tissure does what to the compliance of the lung? increases compliance of the lung
Assessment of mechanical work of breathing involves measurement of? physical parameters of force and distance as they relate to moving air in and out of the lung
Assessment of metabolic work involves meaurement of? oxygen cost of breathing
How to calculate mechanical work of breathing? WOB=change in pressure*change in volume
When can total mechanical work be measured? during artificial ventilation if respiratory muscles are completely at rest.
How much of the WOB can be attributed to elastic forces opposing ventilation? And the remaing? two thirds. is a result of frictional resistance to gas and tissue movement
In the presence of pulmonary disease th WOB can? increase dramatically
In restrictive lung disease the area of the volume pressure curve is? greater because the slope of the static component is less than normal
The area of the voume pressure curve in obstructive lung disease is? increased because the portion associated with frictional resistance is markedly widened.
The meachanical WOB depends on teh pattern of? ventilation
Large tidal do what to the elastic component of work in mechanical WOB? increase the elastic component of work
High breathing rates do what to the frictional work in mechanical WOB? increase the frictional work
Patients with pulmonary fibrosis often assume what breathing pattern? rapid shallow, this pattern minimizes the mechanical of distending the lungs but at the expense of more energy to increase breathing rate.
Patients with obstructive disease often assume what breathing pattern? breathing slowly using pursed lip breathing during exhalation to minimize airway resistance
When increased work of breathing occurs with respiratory muscle weakness what happens to the inspiratory muscles? Tidal volume & RR they fatigue. Tidal volume decrease, RR increases.
How is the oxygen cost of breathing assessed? by measuring the rate of oxygen consumption at rest and at increased levels of ventilation.
What is the average of ocygen cost of breathing in an individual? 0.5-1.0 mL of oxygen per liter of increased ventilation
The rate of oxygen consumtion by the respiratory muscles is closely related to? the inspiratory pressures generated by the diaphragm
How is diaphragmatic pressure measured? (similar to intrapleural)thin catheter is placed into the esophagus. One balloon remains in the esophagus and the other at the tip of the stomach. This measures the difference in pressures.
In the presence of pulmonary diseas teh oxygen cost of breathing does what? Ventilation? increase. increase
Abnormally high oxygen cost of breathing is one factor that limits exercise in what type of patients? patients with obstructive disease such as emphysema
Increased oxygen consumption by the respiratory muscles may also contribute to what when dealing with mechanical ventilation? failure to wean patients off the ventilator
Is ventilation distributed evenly in the lungs? no
What 2 factors account for the unevenness in the distribution of ventilation? regional and local factors
What are the regional factors in the distribution of ventilation? relative differences in thoracic expansion, and regional transpulmonary pressure gradients
(Thorax expansion) The thorax and respiratory muscles cause greater expansion at the lung bases or apices? bases
(Transpulmonary pressure gradients)The transpulmonary pressure is directly relates to what at a given level of alveolar inflation? pleural pressure
Changes in transpulmonary pressure gradient are greatest in what type of alveoli? Do these alveoli expand more or less? peripheral alveoli. More
Pleural pressure increases how much for ech centimeter form the lung apex to its base for th average adult? it increases 0.25cm H2O
What does the increase in pressure in the pleural space from the lung apex to its base result from? weight of the lung an the effect of gravity
How much is pleural pressure at the apex? -10 cm H2O
How much is the pleural pressure at the bases of the lungs? -2.5 cm H20
The bases of the upright lung receive how my ventilation compaired to the apices? 4 times as much at the bases
(Local factors in Distribution of ventilation) Alveolar filling and ventilation are affected by? What determines the filling and emptying? Local factors. compliance and resistance
Each respiratory unit has an elastic element which is? and a resistive element which is? alveolus. Airway
Change in alveolar volume and the time required fro the change to occur depend on? compliance and resistance of each respiratory unit
The more distensible the lung unit the greater will be the? volume change at a given transpulmonary pressure
Lung units with high compliance(distendablilty) have less what? How does this affect the filling and emptying? elastic recoil than normal. They fill and empty more slowly
Lung units with low compliance(high elastic recoil)do what? How does this affect the filling and emptying? increase their volume less. They fill and empty faster than normal
What does the alveolar surfactand help to do in filling and emptying? helps stabilize alveoli of different sizes and evens out filling and emptying
What also affects the emptying and filling? airway resistance
The relationship btw the compliance and resistance of a lung unit is measured and this property of each lung unit is called? time constant
Time constant equals? compliance times resistance
What causes a lung unit to have a long time constant? how long do they take to fill and empty? If resistance or compliance is high. Take longer to fill and empty
What causes a lung unit to have a short time constant? How long do they take to fill and empty? when resistance or compliance is low. Takes faster than normal to fill and empty.
Time constants affect local or regional distribution of ventilation in the lungs? local

1. Alveolar ventilation equation
2. Average compliance of a healthy adult lung  

 

0.2 L/cmH₂O

3. Causes of alveolar dead space • Pulmonary embolism

 

• V/Q mismatch (without perfusion there is no gas exchange)

4. Characteristics of compliance in patients with emphysema  

 

Increased compliance

• ↑ ∆V with small ∆P

• Results from loss of elastic fibers

• Lungs become more distensible, usually resulting in hyperinflation (abnormally increased lung volume)

5. Characteristics of compliance in patients with pulmonary fibrosis  

 

Decreased compliance

• ↓ ∆V for any given ∆P

• Results from increase in connective tissue (fibrotic lung)

• Stiffer lungs with reduced volumes

6. Compare the differences in thoracic expansion from the upper chest to the lower chest Expansion of the lower chest is approximately 50% greater than that of the upper chest
7. Compare the expansion of the alveoli in different regions of the upright lung • Alveoli at the apices have a higher resting volume and expand less during inspiration

 

• Alveoli at the bases have a lower resting volume and receive approximately 4 TIMES as much ventilation as the apices

8. Conditions that can increase tissue viscous resistance • Obesity

 

• Fibrosis

• Ascites

9. Dead Space Equation Vd= 1 mL per lb or 2.2 mL per kg
10. Define airway resistance Impedance to ventilation caused by the movement of gas through the airways
11. Define alveolar dead space The volume of gas ventilating unperfused alveoli
12. Define alveolar ventilation The volume of fresh gas reaching the alveoli per minute
13. Define anatomic dead space The volume of the conducting airways, including the oro-and nasopharynx
14. Define compliance Volume change per unit of pressure change

 

• Compliance is usually measured under static conditions (no airflow)

15. Define dead space Volume of inspired gas that is wasted
16. Define effective ventilation Ventilation is effective when it PaCO₂ is maintained at a level that maintains a normal pH
17. Define elasticity The physical tendency of an object to return to an initial state after deformation

 

• When stretched, the structure tends to return to its original shape

18. Define hyperventilation Ventilation exceeding metabolic needs
19. Define hypoventilation Ventilation that does not meet metabolic needs resulting in respiratory acidosis
20. Define minute ventilation Tidal volume per minute
21. Define Normal VT • Removes CO₂ and supplies O₂ to meet metabolic needs (≈ 0.5 L or 500 mL)
22. Define physiological dead space The sum of anatomical and alveolar dead space
23. Define the Equal Pressure Point (EPP)  

 

The point where intrapleural pressure and alveolar pressure are equal.

• This happens sooner in diseased lungs and can lead to collapsed airways at lower levels

24. Define Tidal Volume (VT) The volume of air inspired or expired in a single breath during regular breathing
25. Define tissue viscous resistance The impedance of motion caused by displacement of tissues during ventilation (lungs, ribcage, diaphragm, abdominal organs)
26. Define work in traditional physical terms W = F ⋅ d

 

(Work = Force × distance)

27. Describe breathing patterns that reduce WOB in individuals with lung diseases • Restrictive: Rapid, shallow breathing

 

• Obstructive: Slow, pursed-lip breathing

28. Describe effective ventilation A balance between CO₂ production and alveolar ventilation
29. Describe exhalation below the resting level Requires muscular effort to overcome the tendency of the chest wall to expand
30. Describe O₂ cost of breathing with increasing ventilation in the presence of pulmonary disease O₂ consumption in the presence of pulmonary disease will dramatically increase as ventilation increases due to an increased work of breathing
31. Describe pulmonary surfactant’s effect on surface tension Pulmonary surfactant changes surface tension according to its area

 

• This ability is reduced as surface area increases

• This ability is increased as surface area decreases

32. Describe the affects of alveolar ventilation in comparison to CO₂ production and removal • Approximately 200 mL of CO₂/min is produced in the body during resting metabolic conditions

 

• Alveolar ventilation must match CO₂ production per minute to ensure the acid-base balance (homeostasis – 40 mmHg)

33. Describe the differences in alveolar pressure (intrapulmonary pressure) during the breathing cycle  

 

• Alveolar pressure varies during the breathing cycle

• Between +0.5 and -0.5 cmH₂O

34. Describe the differences in intraplural pressure during the breathing cycle  

 

• Intraplural pressure is usually negative during quiet breathing and varies during the breathing cycle

• Between -5 and -10 cmH₂O

35. Describe the differences in work of breathing (WOB) during inhalation and exhalation • Inhalation is ACTIVE

 

• Exhalation is PASSIVE

– Forced exhalation requires additional work by expiratory muscles

36. Describe the effect of changes in compliance and resistance on driving pressure and alveolar inflation In an obstructed lung there is the possibility of increased airway resistance in local areas

 

• More driving pressure is needed to flow through airways

• Less driving pressure is available for alveolar inflation

• There is less alveolar volume change for a given pressure

37. Describe the effect that patient/lung position has on ventilation The regions and/or lung closest to the resting surface becomes dependent (better ventilation).
38. Describe the opposing forces that determine the lung volume equivalent to the functional residual capacity (FRC) The lungs and chest wall recoil (in opposite directions) to a resting volume, or Functional Residual Capacity (FRC)

 

• FRC is the total amount of gas left in the lungs after a resting expiration

• Opposing forces are balanced (Palv = Pao)

• Normal FRC is 40% (1200 mL) of total lung capacity (TLC)

39. Describe the pressure changes during inspiration and expiration • Pbs and Pao remain at 0 throughout cycle

 

• Palv and Ppl are changing throughout cycle

40. Describe the transpulmonary pressure gradient • The difference in pressure between the alveoli and the pleural space

 

• Pl = Palv – Ptp

41. Describe the transresipiratory pressure gradient (Prs) • The difference in pressure between the atmosphere and the alveoli

 

• Prs = Palv – Pao

• In a spontaneously breathing patient, Pao = Pbs = 1 atm (760 mmHg)

42. Describe the transthoracic pressure gradient • The difference in pressure between the plural space and the body surface

 

• Pw = Ppl – Pbs

• In a spontaneously breathing patient, Pbs = Pao = 1 atm (760 mmHg)

43. Factors that affect the efficiency of ventilation • Regional differences in ventilation

 

• Dead space (anatomic and alveolar)

• Alveolar ventilation

• Efficiency = consume little oxygen and produce minimum CO₂

44. Factors that increase the elastic component of the work of breathing  

 

Restrictive lung diseases, like pulmonary fibrosis; tidal volume

45. Factors that increase the frictional component of work of breathing  

 

Obstructive lung diseases, like COPD (emphysema, chronic bronchitis); shallow breathing

46. Formula for airway resistance  

 

The ratio of driving pressure responsible for gas movement to the flow of the gas

• cmH₂O/L/sec (cmH₂O per liter per second)

• Think Pressure/Flow

47. Formula or measurement of lung compliance  

 

• ∆V (liters) is the inspired volume

• ∆P (cmH₂O) is the transpulmonary pressure gradient

• Units are L/cmH₂O

48. Formula to compute mechanical work of breathing WOB = ∆P × ∆V
49. Formula to compute the time constant of a lung unit Time Constant = R × C

 

• R = Resistance (cmH₂O/L/sec)

• C = Compliance (L/cmH₂O)

• All units cancel except seconds

50. Identify all forces that must be overcome to move into the respiratory system • Elastic forces

 

• Frictional forces

51. Identify the causes of long time constants • Resistance or compliance is high

 

• Lung unit will fill and empty more slowly

52. Identify the causes of short time constants • Resistance or compliance is low

 

• Lung unit will fill and empty more rapidly

53. Identify the distribution of airway resistance by location • 80% in nose, mouth, and large airways

 

• 20% in airways > 2mm in diameter where flow is mainly laminar

54. Identify the elastic forces opposing lung inflation • Tissues of the lungs and thorax

 

• Surface tension in the alveoli

55. Identify the factors that affect the dead space/tidal volume ratio during normal breathing and during exercise • Physiological dead space is approximately 1/3 of tidal volume (30%)

 

• During exercise, both increase, but tidal volume increases more, reducing the dead space/tidal volume ratio.

56. Identify the frictional forces opposing lung inflation • Resistance caused by gas flow (80%)

 

• Tissue movement during breathing (20%)

57. Identify the normal total lung-thorax compliance of a healthy subject 0.1 L/cmH₂O
58. Identify the proportions attributed to the total work of breathing  

 

• Approximately 2/3 of WOB is attributed to elastic forces

• Remaining 1/3 is attributed to frictional forcesTotal mechanical WOB is the sum of areas 1 + 2 above

59. Minute ventilation equation
60. Normal range of airway resistance in healthy adults 0.5 – 2.5 cmH₂O/L/sec
61. Primary Function of the Lungs • Supply O₂

 

• Remove CO₂

62. Rule of thumb for changes in caliber of airway A change in the caliber of an airway by a factor of 2 causes a 16-fold change in resistance (r⁴ = 16, if r = 2)
63. The best indicator of effective ventilation Normal PaCO₂ and pH
64. The point during inspiration that the chest wall reaches natural resting level  

 

70% of vital capacity (VC)

 

 

Egan’s Chapter 10 Study Guide:

 

1. Ventilation: the process of moving air between the environment and the alveoli

2. Respiration: the process of gas exchange between the alveoli and pulmonary capillary blood

3. Transpulmonary pressure gradient: pressure difference btwn the alveoli and the plural pressure

4. Transairway pressure: the pressure difference between the alveoli and the entrance of the airway

5. Transthoracic pressure: the pressure difference btwn the alveoli and the body surface

6. What are the 3 pressure gradients responsible for gas movement and lung inflation?

trans: pulmonary, airway, thoracic

7. What 2 pressure gradients are the same?: Transairway and Transthoracic

8. Why must pressure gradients exist?: for spontaneous ventilation to occur


9. What is pleural pressure at rest?: subatmospheric

10. What is the process of inspiration during NORMAL breathing?: diaphragm and external intercostal muscles contract > Ribcage lifts > volume of pleural space increases > (the increase in volume causes a decrease in pleural pressure per Boyle’s Law) > Transpulmonary pressure gradient increases > alveoli expand and their volume increases > alveolar pressure becomes subatmospheric > transairway pressure gradient increases > air flows from the airway entrances to the alveoli until muscular effort ceases and the transairway pressure equalizes

11. What is the process of expiration during NORMAL breathing?: Diaphragm relaxes and rib cage recoils > plueral space and volume decrease > pleural pressure increases > transpulmonary pressure gradiant narrows (lessens) > alveoli recoil > alveolar space decreases > alveolar pressure becomes supraatmospheric > transairway pressure gradient widens (increases) > air flows out of the lungs until back into the resting state (transairway pressure gradient equalizes)

12. What are the forces opposing ventilaion of the lung?: elastic forces ( tissue retraction, ST in alveoli, static forces nor affected by airflow) and non-elastic frictional forces (RAW and tissue movement during breathing)

13. Surface tension: tension created at the liquid air interface

14. Compliance: the measure of distendability of the lung

15. Elasticity: the ability of the lung to return to a normal shape after being stretched

16. How is ST produced?: by the cohesive forces of a liquid that attracts the polar liquid molecules away from the interface

17. What effect does ST have on the lungs?: draws them inward, causing them to recoil

18. How does the body combat ST?: with surfactant

19. Surfactant: a phospholipid that places itself between the liquid molecules, causing a decrease in cohesive bonding

20. Is the surfactant layer thicker or thinner in a smaller SA than a greater SA? Why?: thicker to offset increase ST

21. What is lung complaince?: the measure of distendability of the lung

22. What is the formula for lung Compliance?:

CL = dV/dP mL/cmH2O

V = tidal volume

P = transpulmonary pressure gradient

23. What is the compliance of the lungs and chest wall?: 200 mL/cmH2O and 200 mL/cmH2O

24. What is the total compliance?: compliange of lung + compliance of thorax

25. What is the normal total compliance?: 100 mL/cmH2O

26. What effect does the pressure of surfactant in the alveoli have on compliance? Why?: increased (less ST so more stretching can be done)

27. What would happen to compliance in a lung that loses its elastic fibers?: increase

28. What effect does increased compliance have on elasticity? why?: since the lungs would expand more easily by recoil with more difficulty the elasticity would decrease

29. What effect would decreased compliance have on elasticity? Why?: causes the lungs to distend with difficculty so an increased elasticity

 

Egan’s Chapter 10 (Ventilation) Test Bank:

 

1. Transairway and transthoracic presure gradients are equal. TRUE

2. alveolar dead space: alveoli that are ventilated but are not perfused. The condition may exist when pulmonary circulationmuscle activity is obstructed as by thromboembolus

3. A change in the caliber of an airway by a factor of 2 causes what change in resistance?: 16 fold

4. compliance: volume change per unit is applied pressure. change in volume / by the change in pressure

5. dynamic compression: compliance of airways caused by a pressure gradient that occurs with breathing or forced breathing and normally occurs in diseased airways

6. dynamic hyperinflation (air trapping): increased in functional residual capacity above the elastic equilibrium volume of the respiratory system; causes include increased flow resistance, short inspiratory time and increased post-respiratory muscle acitvity

7. elastance: tendency of matter to resist a stretching force and recoil or return to its original size or form after deformation or expansion; the reciprocal of compliance

8. elasticity: the ability tissue to regain its original shape and size after being stretched, squeezed or other wise deformed. Muscle tissue is generally regarded as elastic because it is able to change size and shape and return to its original condition

9. equal pressure point (EPP): during forced exhalation, the point along an airway where the pressure inside its wall equals the intrapleural pressure, upstream beyond this point, the pleural pressure exceeds the pressure inside the airway, tending to promote bronchiolar collapse

10. hyperventilation: ventilation greater than necessary to meet metabolic needs, signified by PCO2 less than 35mmHg in the arterial blood.

11. hypoventilation: ventilation less than necessary to meet metabolic needs; signified by PCO2 greater than 45mmHg in the arterial blood

12. hysteresis: failure of two associated phenomena to coincide, as in the observed difference between the inflation and deflation volume pressure curves of the lungs

13. physiologic dead space: area in the respiratory system that includes the anatomic dead space together with the space in the alveoli occupied by air that does not contribute to the O2-CO2 exchange

14. plethysmograph: device for measuring pressure; in pulmonary physiology, a chamber in which the subject sits to measure lung pressure and volumes

15. pneumotachometer: any device for measuring gas flow

16. pressure gradient: the pressure difference between 2 points in a system

17. subatmospheric: below atmosphere; used to describe pressure below ambient

18. surface tension: the tendency of a liquid to minimize the area of its surface bu contracting. This property causes liquids to rise in a capillary tube, effects the exchange of gases in the pulmonary alveoli, and alters the ability of various liquids to wet another surface.

19. tidal volume: volume of air that is inhaled of exhaled form the lungs during effortless breathing

20. time constant: mathematical expression describing the relative efficacy of lung unit filling and emptying and computed as the product of compliance times resistance (measured in seconds)

21. transairway pressure: difference between airway pressure and alveolar pressure and pleural pressure

22. transairway pressure difference: pressure measured at airway opening minus pressure measured at alveoli of lungs

23. transalveolar pressure: difference between alveolar pressure and pleural pressure

24. transalveolar pressure difference: pressure measured at alveoli of lungs minus pressure measured at the pleural space

25. trans-chest wall pressure: difference between the pleural space and the body surface, also called transthoracic pressure

26. trans-chest wall pressure difference: pressure measured at the pleural space minus pressure measured at body surface

27. transpulmonary: of or pertaining to the difference in a parameter between the alveoli and pleural space

28. transpulmonary pressure difference: pressure measured at airway opening minus pressure measured at the pleural space

29. transrespiratory pressure difference: pressure measured at airway opening minus pressure measured at body surface

30. transrespiratory pressure gradient: pressure differential between the mouth and the alveoli that causes gas to flow in and out of the lungs

31. transthoracic: across the thorax of or pertaining to the difference in a parameter between the pleural space and body surface

32. transthoracic pressure difference: pressure measured at alveoli of lungs minus pressure measured at body surface

33. ventilation: molecular exchange of O2 and CO2 within the body’s tissues

34. what are two forces that oppose lung inflation?: elastic forces and frictional forces

35. What does the respiratory muscles use to preform work?: O2

36. What is normal physiologic dead space: 150ml

37. what is normal tidal volume: 500ml

38.What is the compliance of the lung and chest wall in a healthy adult?: ~ 0.2 L/cm H2O

 

Egan’s Chapter 10 Practice Questions:

 

1. There are 3 Pressure Gradients involved in ventilation.

2. 3 Pressure Gradients involved in ventilation: 1. Transrespiratroy Pressure, 2. Transpulmonary Presure, 3. Transthoracic Pressure

3. airway resistance: measure of the impedance to ventilation caused by the movement of gas through the airways; abbreviated as Raw, airway resistance is computed as the change in pressure along a tube divided by the flow.

4. alveolar dead space: alveoli that are ventilated but are not perfused. The condition may exist when pulmonary circulation is obstructed, as by a thromboembolus.

5. At end of resting exhalation: transpulmonary pressure, PL, normally 5 cm H2O; Palv is zero, period of no gas flow

6. Compliance: volume change per unit in applied pressure.

7. dynamic compression: collapse of airways caused by a pressure gradient that occurs with breathing or forced breathing and normally occurs in diseased airways.

8. elastance: tendency of matter to resist a stretching force and recoil or return to its original size or form after deformation or expansion; the reciprocal of compliance. Also called elasticity

9. elasticity: ability of tissue to regain its original shape and size after being stretched, squeezed, or otherwise deformed. Muscle tissue is generally regarded as elastic because it is able to change size and shape and return to its original condition

10. equal pressure point (EPP): during forced exhalation, the point along an airway where the pressure inside its wall equals the intrapleural pressure; upstream beyond this point, the pleural pressure exceeds the pressure inside the airway, tending to promote bronchiolar collapse.

11. Expiration begins:

-Thoracic recoil causes Ppl to begin to rise.

-PL declines, so alveoli begin to deflate.

-Shrinking alveoli increase Palv so “positive” pressure gradient compared to Pao (↑Prs)

-Gas moves from alveoli to atmosphere.

-When Palv falls to Pao, expiratory flow stops.

12. hyperventilation: ventilation greater than necessary to meet metabolic needs; signified by PCO2 less than 35 mm Hg in the arterial blood.

13. hypoventilation: ventilation less than necessary to meet metabolic needs; signified by PCO2 greater than 45 mm Hg in the arterial blood

14. hysteresis: failure of two associated phenomena to coincide, as in the observed difference between the inflation and deflation volume-pressure curves of the lung.

15. Inspiration begins.:

-Inspiratory muscles expand thorax; ↓Ppl widens PL, causing alveoli to expand.

-Alveolar expansion decreases Palv below zero, resulting in “negative” Prs, so gas enters.

-Alveolar filling slows as Palv approaches Pao.

-End-inspiration Prs is again zero as Palv = Pao.

16. Lung and thorax compliance & Resistance:

-The load the respiratory muscles overcome to produce ventilaiton.

-Healthy Lngs at rest, inspiratory Load is minimal, while expiration is passive

17. Normal Tidal Volumes: Women- 450-650, Men 650-700

18. physiologic dead space: area in the respiratory system that includes the anatomic dead space together with the space in the alveoli occupied by air that does not contribute to the O2-CO2 exchange

19. plethysmograph: device for measuring pressure; in pulmonary physiology, a chamber in which the subject sits to measure lung pressures and volumes

20. pneumotachometer: any device for measuring gas flow

21. pressure gradient: the pressure difference between 2 points in a system.

22. Pressure is always measured in: cm of H20 (water)

23. subatmospheric: below atmospheric; used to describe pressures below ambient.

24. surface tension: tendency of a liquid to minimize the area of its surface by contracting. This property causes liquids to rise in a capillary tube, effects the exchange of gases in the pulmonary alveoli, and alters the ability of various liquids to wet another surface

25. tidal volume (VT): volume of air that is inhaled or exhaled from the lungs during effortless breath

26. time constant: mathematical expression describing the relative efficacy of lung unit filling and emptying and computed as the product of compliance times resistance (measured in seconds)

27. transpulmonary: of or pertaining to the difference in a parameter (e.g., pressure) between the alveoli and pleural space.

28. Transpulmonary pressure:

-PL = Palv – Ppl

-PL keeps alveoli open.

-Etablished by opposing lung and thorax recoil

-The pressures that exist in the pulmonary system.

29. transrespiratory: across the respiratory system; of or pertaining to the difference in a parameter (e.g., pressure) between the alveoli and the body surface

30. Transrespiratory pressure: Prs = Palv – P(bs or ao) (bs=body surface) .This gradient causes gas flow in and out of lungs. It is the pressure between 2 points.

31. transthoracic: across the thorax; of or pertaining to the difference in a parameter (e.g., pressure) between the pleural space and body surface.

32. Transthoracic pressure:

-Pw = Ppl – Pbs

-Pw pressure across chest wall

-Represents total pressure required to expand or contract the lungs and chest wall together

33. transthoracic pressure difference (PTT): difference between the pleural space and the body surface. Also called trans-chest wall pressure

34. ventilation: molecular exchange of O2 and CO2 within the body’s tissues.

35. Ventilation is cyclic: Inspiration and Expiration

-Tidal volume (Vt): has per cycle

-Facilitates removal of CO2, replinishes 02

36. WOB: Work of breathing