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Respiratory System > Lecture 3.1: Lung Ventilation > Flashcards

Lecture 3.1: Lung Ventilation Flashcards

1
Q

How much oxygen should blood pick up in the lungs at rest?

A

5 liters of blood must pick up 12 mmol of oxygen per minute

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2
Q

How many alveoli do we have?

A

300 million alveoli (each surrounded by a capillary)

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3
Q

What is the order of sub-divisions in the lung airways?

A

• Trachea branches
• Main bronchi (right and left)
• Lobar bronchi (3 on right 2 on left)
• Segmental bronchi
• Sub-segmental bronchi
• Bronchioles
• Terminal bronchioles
• Respiratory bronchioles
• Alveolar ducts
• Alveoli

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4
Q

What is the difference between the walls of bronchi and bronchioles?

A

• Bronchi have cartilage in walls
• Bronchioles do not but do have more
smooth muscle

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5
Q

What is the importance of the hydrostatic pressure gradient?

A

Drives fluid from the pulmonary microcirculation into the interstitium

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6
Q

What is the importance of the oncotic pressure (colloidal osmotic pressure)?

A

Gradient favours movement of fluid in the opposite direction

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7
Q

How does ‘alveolar air’ have a different composition to the atmosphere?

A

• Less Oxygen
• More Carbon Dioxide
• As gas exchange removes oxygen from and
adds carbon dioxide to alveolar air

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8
Q

Mixed Venous Blood: pO2? pCO2?

A

• Returns to the lungs from the body
• pO2 typically 6.0 kPa
• pCO2 typically 6.5 kPa
• This varies with metabolism

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9
Q

Alveolar Air: pO2? pCO2?

A

• pO2 normally 13.3 kPa
• pCO2 normally 5.3 kPa

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10
Q

What are the 3 factors that affect Diffusion?

A

1) Area: Large (exchange area in normal lung
70m2)
2) Gradients: Large
3) Diffusion Resistance

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11
Q

Diffusion Barrier

A

• Diffusion through gas to alveolar wall
• Epithelial cell of alveolus
• Tissue Fluid
• Endothelial Cell of Capillary
• Plasma
• Red Cell Membrane

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12
Q

What machine is used to measure ventilation?

A

Spirometer

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13
Q

How to use a Spirometer?

A

• Subject breathes from a closed chamber
over water
• Whose volume changes with ventilation

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14
Q

What is Tidal Volume?

A

• Volume in and out with each breath
• In males: 0.5L
• In females: 0.5L

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15
Q

What is Inspiratory Reserve Volume?

A

• Extra volume that can be breathed in over
that at rest
• In males: 3.3L
• In females: 1.9L

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16
Q

What is Expiratory Reserve Volume?

A

• Extra volume that can be breathed out
over that at rest
• In males: 1.1L
• In females: 0.7L

17
Q

What is Residual Volume? How to measure it?

A

• Volume left in lungs at maximal expiration
(0.8L)
• Volume does not change
• Cannot be measured by spirometer
• Use helium dilution

18
Q

Lung Capacities vs Lung Volumes

A

• Lung volumes change with breathing pattern
• Capacities do not change
• Because measured from fixed points in breathing cycle

19
Q

What are the 4 measured Lung Capacities?

A
  1. Vital capacity (VC) (can be measured by spirometers)
  2. Total lung capacity (TLC)
  3. Inspiratory capacity (IC) (can be measured by spirometers)
  4. Functional residual capacity (FRC)
20
Q

What is Vital Capacity?

A

• Measured from max inspiration to max expiration
• Often changes in disease
• Typically 5L
• Total Lung Capacity = Vital Capacity + Reserve Volume

21
Q

What is Inspiratory Capacity?

A

• Biggest breath that can be taken from resting expiratory level
• Typically 3.8L

22
Q

What is Functional Residual Capacity?

A

• Volume of air in lungs at resting expiratory level
• Typically 2L
• Functional Residual Capacity = Expiratory Reserve Volume + Residual Volume

23
Q

What is Ventilation Rate?

A

The amount of air moved into and out of a space per minute product of:
1) Volume moved per breath
2) Respiratory Rate

24
Q

What is Pulmonary Ventilation Rate?

A

• Tidal volume x respiratory rate
• Typically 8l.min-1 at rest
• Can exceed 80 l.min-1 in exercise

25
Q

What is Dead Space?

A

• The volume of air that is inhaled that does not take part in the gas exchange
• Because it either remains in the conducting airways
• Or reaches alveoli that are not perfused or poorly perfused

26
Q

What is Serial Dead Space?

A

Anatomical Deadspace

27
Q

What is Distributive Dead Space?

A

Alveolar Deadspace

28
Q

What is Alveolar Ventilation Rate?

A

• The amount of air that actually reaches the alveoli

29
Q

What is the calculation for Physiological Dead Space?

A

• Serial Dead Space + Distributive Dead Space = Physiological Dead Space
• Typically 0.17l

30
Q

What is the calculation for Alveolar Ventilation Rate?

A

Alveolar Ventilation Rate = Pulmonary Ventilation Rate - Dead Space Ventilation Rate

31
Q

How to calculate DSVR?

A

DSVR = DS vol x Respiratory Rate

32
Q

How to calculate Pulmonary Ventilation Rate?

A

PVR = Tital Volume x Respiratory Rate

33
Q

How to calculate Alveolar Ventilation Rate?

A

AVR = PVR - DSVR

34
Q

How much Inspired Air is ‘wasted’ in normal breathing?

A

1/3

35
Q

How much Inspired Air is ‘wasted’ in shallow, rapid breathing?

A

2/3

36
Q

But why do we not take slow, deep breaths if less inspired air is ‘wasted’?

A

It is hard work so at rest we adopt an intermediate rate and depth

37
Q

What is Ventilation Perfusion Matching (Ratio)?

A

A ratio used to assess the efficiency and adequacy of the matching of two variables:
• V – ventilation – the air that reaches the alveoli
• Q – perfusion – the blood that reaches the alveoli via the capillaries
• V/Q

38
Q

Why can Ventilation Perfusion Mismatch occur? (3)

A

Reduced ventilation to a well perfused area of the lung:
• Airway obstruction
• Alveolar disease, damage

Reduced perfusion to well ventilated areas of the lung:
• Pulmonary embolism

Respiratory System (19 decks)

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