Respiratory Mechanics I

1. [1ST ORDER] What is spirometry?

A method of measuring changes in the volume of air moved into and out of the lungs

2. [HIGH-YIELD] What are the four basic lung volumes?

Tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume

3. [1ST ORDER] Define tidal volume (TV).

The volume of air inhaled or exhaled during a normal quiet breath

4. [HIGH-YIELD] What is the approximate normal adult tidal volume?

0.5 L or 500 mL

5. [1ST ORDER] Define inspiratory reserve volume (IRV).

The additional volume of air that can be inspired after a normal tidal inspiration

6. [1ST ORDER] Define expiratory reserve volume (ERV).

The additional volume of air that can be expired after a normal tidal expiration

7. [HIGH-YIELD] Define residual volume (RV).

The air remaining in the lungs after maximal expiration

8. [HIGH-YIELD] Why does residual volume remain after maximal expiration?

Airway closure and air trapping prevent complete emptying of the lungs

9. [HIGH-YIELD] Can residual volume be measured using simple spirometry?

No

residual volume remains after maximal expiration and cannot be exhaled into a spirometer

10. [1ST ORDER] What is a lung capacity?

A combination of two or more lung volumes

11. [HIGH-YIELD] Define inspiratory capacity (IC).

The maximum volume inspired starting at the end of a normal quiet expiration

12. [HIGH-YIELD] Write the inspiratory capacity equation.

IC = TV + IRV

13. [HIGH-YIELD] Define functional residual capacity (FRC).

The volume of air remaining in the lungs after normal quiet expiration

14. [HIGH-YIELD] Write the functional residual capacity equation.

FRC = ERV + RV

15. [HIGH-YIELD] Define vital capacity (VC).

The maximum volume of air that can be exhaled after maximal inspiration

16. [HIGH-YIELD] Write the vital capacity equation.

VC = IRV + TV + ERV

17. [HIGH-YIELD] Define total lung capacity (TLC).

The total volume of air in the lungs after maximal inspiration

18. [HIGH-YIELD] Write the total lung capacity equation.

TLC = IRV + TV + ERV + RV

19. [HIGH-YIELD] Write total lung capacity using vital capacity.

TLC = VC + RV

20. [HIGH-YIELD] Which lung capacities cannot be measured directly using simple spirometry?

FRC and TLC, because both contain residual volume

21. [HIGH-YIELD] Why can vital capacity be measured using spirometry?

All the air comprising VC can be moved through the mouth during maximal respiratory maneuvers

22. [2ND ORDER] Why is FRC physiologically important?

It is the resting equilibrium volume of the combined lung and chest wall

23. [HIGH-YIELD] What two mechanical forces balance at FRC?

Inward elastic recoil of the lungs and outward elastic recoil of the chest wall

24. [2ND ORDER] At what point in normal tidal breathing is FRC reached?

At the end of quiet expiration

25. [2ND ORDER] Which lung volume cannot be voluntarily exhaled?

Residual volume

26. [2ND ORDER] Which capacity represents the air that can be moved between maximal inspiration and maximal expiration?

Vital capacity

27. [2ND ORDER] Which capacity contains every basic lung volume?

Total lung capacity

28. [2ND ORDER] Which capacity includes residual volume but not tidal volume?

Functional residual capacity

29. [2ND ORDER] Which capacity includes tidal volume and IRV but excludes ERV and RV?

Inspiratory capacity

30. [HIGH-YIELD] What is the approximate IRV for the adult male reference in the lecture?

3.0 L

31. [HIGH-YIELD] What is the approximate IRV for the adult female reference in the lecture?

1.9 L

32. [HIGH-YIELD] What is the approximate ERV for the adult male reference?

1.1 L

33. [HIGH-YIELD] What is the approximate ERV for the adult female reference?

0.7 L

34. [HIGH-YIELD] What is the approximate RV for the adult male reference?

1.2 L

35. [HIGH-YIELD] What is the approximate RV for the adult female reference?

1.1 L

36. [2ND ORDER] Why do reference lung volumes often differ between adult males and females?

The lecture emphasizes differences in average body and lung size rather than sex alone

37. [2ND ORDER] What happens to expected lung volume as body size increases?

Expected lung volume generally increases

38. [3RD ORDER] TV is 0.5 L and IRV is 3.0 L. Calculate IC.

IC = 0.5 + 3.0 = 3.5 L

39. [3RD ORDER] ERV is 1.1 L and RV is 1.2 L. Calculate FRC.

FRC = 1.1 + 1.2 = 2.3 L

40. [3RD ORDER] IRV is 3.0 L, TV is 0.5 L, and ERV is 1.1 L. Calculate VC.

VC = 3.0 + 0.5 + 1.1 = 4.6 L

41. [3RD ORDER] VC is 4.6 L and RV is 1.2 L. Calculate TLC.

TLC = 4.6 + 1.2 = 5.8 L

42. [3RD ORDER] IC is 3.5 L and TV is 0.5 L. Calculate IRV.

IRV = IC − TV = 3.0 L

43. [3RD ORDER] FRC is 2.3 L and RV is 1.2 L. Calculate ERV.

ERV = FRC − RV = 1.1 L

44. [3RD ORDER] TLC is 5.8 L and VC is 4.6 L. Calculate RV.

RV = TLC − VC = 1.2 L

45. [3RD ORDER] A patient performs maximal expiration and still has air trapped in the lungs. What volume remains?

Residual volume

46. [3RD ORDER] A patient finishes a normal quiet expiration. What lung capacity is present?

Functional residual capacity

47. [3RD ORDER] A patient inspires maximally after a quiet expiration. What capacity did they inspire?

Inspiratory capacity

48. [3RD ORDER] A patient exhales maximally after maximal inspiration. What capacity did they exhale?

Vital capacity

49. [4TH ORDER] A clinician wants TLC from simple spirometry alone. Why is this impossible?

TLC includes RV, which cannot be exhaled or measured directly by simple spirometry

50. [4TH ORDER] Why can two healthy adults have different lung volumes without either having disease?

Normal lung volumes vary with body size and other individual characteristics

51. [DRAW/MAP] Map the four volumes from lowest to highest lung volume.

RV → add ERV → FRC → add TV → end tidal inspiration → add IRV → TLC

52. [DRAW/MAP] Map all four lung capacities.

IC = TV + IRV

FRC = ERV + RV

VC = IRV + TV + ERV

TLC = VC + RV

53. [DRAW/MAP] Map the changes during quiet and maximal breathing.

End quiet expiration at FRC → inhale TV → exhale TV to FRC → force expiration of ERV to RV → maximal inspiration to TLC

54. [HIGH-YIELD] What should be memorized about the spirometry slide for the exam?

Definitions of volumes and capacities, their component relationships, and the ability to solve for missing values

55. [4TH ORDER] Why is FRC especially important for understanding the rest of this lecture?

It is the mechanical equilibrium point used to interpret lung and chest wall recoil and compliance curves

56. [HIGH-YIELD] What is the primary muscle of inspiration?

The diaphragm

57. [1ST ORDER] What happens to the diaphragm during inspiration?

It contracts and descends

58. [2ND ORDER] How does diaphragm contraction cause air to enter the lungs?

Thoracic expansion lowers alveolar pressure below atmospheric pressure, creating inward airflow

59. [HIGH-YIELD] What muscles assist normal inspiration by elevating the ribs?

External intercostal muscles

60. [1ST ORDER] What is the orientation of external intercostal muscle fibers?

They slope downward and forward between adjacent ribs

61. [2ND ORDER] What is the bucket-handle movement of the ribs?

Upward and outward movement of the rib cage during inspiration

62. [HIGH-YIELD] Which accessory inspiratory muscles are mentioned in the lecture?

Scalenes, sternocleidomastoid, and pectoralis muscles

63. [HIGH-YIELD] When are accessory inspiratory muscles most likely to be recruited?

During increased respiratory demand or labored breathing

64. [HIGH-YIELD] Is expiration normally active or passive during quiet breathing?

Passive

65. [2ND ORDER] What produces quiet expiration?

Relaxation of inspiratory muscles and elastic recoil of the respiratory system

66. [1ST ORDER] What happens to the diaphragm during quiet expiration?

It relaxes and moves upward

67. [HIGH-YIELD] Which intercostal muscle group assists forced expiration?

Internal intercostals

68. [HIGH-YIELD] Which major muscle group also assists forced expiration?

Abdominal muscles

69. [2ND ORDER] Why are abdominal muscles useful during forced expiration?

Their contraction increases abdominal pressure and pushes the diaphragm upward

70. [2ND ORDER] Why is forced expiration different from quiet expiration?

Forced expiration recruits active muscles instead of relying only on passive recoil

71. [HIGH-YIELD] What mnemonic does Dr. Michels provide for the intercostals?

External = Inspiration

Internal = Expiration

72. [3RD ORDER] A patient is breathing quietly without distress. Which muscle is responsible for most inspiratory effort?

Diaphragm

73. [3RD ORDER] A patient is using sternocleidomastoid and scalene muscles to breathe. What does this suggest?

Increased work of breathing or increased inspiratory demand

74. [3RD ORDER] A patient forcefully exhales during a respiratory maneuver. Which muscle groups are recruited?

Internal intercostals and abdominal muscles

75. [DRAW/MAP] Map the mechanical sequence of inspiration.

Diaphragm contracts and descends → rib cage expands → thoracic volume increases → alveolar pressure decreases → air enters

76. [DRAW/MAP] Map quiet expiration.

Inspiratory muscles relax → lung elastic recoil reduces lung volume → alveolar pressure rises above atmospheric pressure → air exits

77. [DRAW/MAP] Map forced expiration.

Abdominal and internal intercostal contraction → thoracic volume decreases → alveolar pressure rises → air is expelled forcefully

78. [HIGH-YIELD] What is the intrapleural space?

The space between the lung's visceral pleura and the chest wall's parietal pleura

79. [HIGH-YIELD] What is the normal pressure characteristic of the intrapleural space?

It is negative relative to atmospheric pressure during normal quiet breathing

80. [HIGH-YIELD] What mechanical tendency does the isolated lung have?

It tends to recoil inward

81. [HIGH-YIELD] What mechanical tendency does the chest wall have near FRC?

It tends to spring outward

82. [2ND ORDER] Why is intrapleural pressure normally negative?

Opposing recoil forces of the lung and chest wall create subatmospheric pressure in the pleural space

83. [2ND ORDER] Why is negative intrapleural pressure important?

It maintains mechanical coupling between lung expansion and chest wall movement

84. [HIGH-YIELD] What is transmural pressure?

The pressure inside a structure minus the pressure outside it

85. [HIGH-YIELD] What is transpulmonary pressure?

The difference between alveolar pressure and intrapleural pressure

86. [HIGH-YIELD] Write the transpulmonary pressure equation.

Ptp = Palv − Ppl

87. [2ND ORDER] Why is transpulmonary pressure usually positive?

Intrapleural pressure is negative relative to alveolar pressure

88. [2ND ORDER] What can happen when transmural pressure becomes negative?

An airway may narrow or collapse

89. [3RD ORDER] Palv is 0 and Ppl is −5 cm H2O. Calculate transpulmonary pressure.

Ptp = 0 − (−5) = +5 cm H2O

90. [3RD ORDER] Palv is 0 and Ppl is −8 cm H2O. Calculate transpulmonary pressure.

Ptp = +8 cm H2O

91. [HIGH-YIELD] What is a pneumothorax?

Air entering the pleural space, disrupting the normal lung–chest wall mechanical relationship

92. [HIGH-YIELD] What happens to the lung when a pneumothorax disrupts pleural coupling?

The lung tends to recoil inward and collapse

93. [HIGH-YIELD] What happens to the chest wall after pleural coupling is disrupted?

It tends to spring outward

94. [2ND ORDER] Why does a pneumothorax impair breathing?

The normal negative-pressure coupling needed for lung expansion is disrupted

95. [HIGH-YIELD] What is PEEP?

Positive end-expiratory pressure maintained in the airway during mechanical ventilation