Lecture 3 - Lung mechanisms Flashcards

1
Q

Ventilation

A

Process of inspiration and expiration

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2
Q

Lung volumes

A
Tidal volume
Residual volume
Inspiratory reserve volume
Expiratory reserve volume 
Total lung volume
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3
Q

Tidal volume

A

Volume of air that enters and leaves the lungs at each breath during normal respiration

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4
Q

IRV

A

Max inspired volume of air

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5
Q

ERV

A

Max expired volume of air

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6
Q

Residual volume

A

Volume of air retained after forced expiration

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7
Q

Total lung volume

A

Vital capacity + RV

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8
Q

Lung capacities

A

Inspiratory capacity
Functional residual capacity
Vital capacity

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9
Q

Inspiratory capacity

A

End of quiet expiration to max inspiration

The volume of air that can be inhaled

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10
Q

Functional residual capacity

A

ERV + RV

Volume of air in lungs after quiet expiration

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11
Q

Vital capacity

A

IC + ERV
(IRV+ TV) + ERV

Volume of air breathed in and out of lungs during forced respiration

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12
Q

Anatomical dead space

A

Air that fills the conducting airways not available for gas exchange

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13
Q

Physiological dead space

A

Anatomical dead space + alveolar dead space

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14
Q

Alveolar dead space

A

Air in alveoli that are not perfused or are damaged. Therefore gas exchange does not occur

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15
Q

Tidal volume in terms of anatomical dead space

A

Anatomical dead space + alveolar ventilation

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16
Q

Total pulmonary ventilation (minute volume)

17
Q

Alveolar ventilation

A

(TV- anatomical dead space) x RR

18
Q

Describe quiet inspiration

A
  1. At the end of quiet expiration the atmospheric pressure = intrathoracic pressure
  2. The ribs move laterally and superiorly as the chest expands (30% external intercostal and 70% diaphragm) Muscles contract overcome elastic recoil
  3. The pleural fluid ensures that the lungs expand with the thorax
  4. Intrapulmonary volume increases and pressure decreases
  5. The intrapulmonary pressure is lower than the atmospheric pressure which creates a negative pressure
  6. Air is drawn in
19
Q

Boyle’s law

A

An inverse relationship between pressure and volume of a gas

20
Q

Describe quiet expiration

A

Air is expelled passively

  1. Relaxation of inspiratory muscles so they no longer overcome elastic recoil, reducing the intrathoracic volume and reduces lung volume.
  2. The intrapulmonary pressure is greater than the atmospheric pressure so air is drawn out
21
Q

Resting expiratory level

A

State of equilibrium where all forces are equal and opposite so balance out resulting in no chest wall movement at rest

Creates negative pressure within the intrapleural space

There is a tendency to always want to return to the resting state

22
Q

Forces exerted in the chest wall

A

Lung elasticity and surface tension - lungs pull in and up
Muscles and fascia - Chest wall pulls out
Passive stretch - Diaphragm pulls down

23
Q

Why is intrapleural space negative?

A

The elastic recoil of the lung pulls the visceral pleura inwards and the chest wall pulls the parietal pleura outward

24
Q

Breach in pleural seal

A

Pneumothorax- air is drawn in due to negative pressure

Lung collapse due elastic recoil

25
Accessory muscles of inspiration
SCM Pectoralis major Serratous anterior Scalene muscles
26
Accessory muscles of expiration
Internal intercostal muscles Innermost intercostal muscles Abdominal wall muscles - rectus abdominis + EO + IO
27
Compliance
The extent to which the lungs can stretch | Volume change per unit volume change
28
Elastic recoil
The tendency to return to a resting state
29
What determines compliance?
Elasticity of lung tissue Surface tension of fluid lining the alveoli Surfactant
30
Surface tension
During respiration, the fluid lining the airways and alveoli must stretch due to the increasing SA Surface tension resist this as want to achieve minimal SA. Reduces compliance
31
Surfactant
Secreted by type II pneumocytes Mixture of phospholipids and proteins with detergent properties which floats on fluid Surfactant molecules between the fluid molecules disrupt the interactions between the fluid molecules Reduces surface tension Increases compliance Ensures that pressure is the same in all alveoli regardless of size Prevents collapse of small alveoli into big alveoli
32
How does SA affect surface tension
As SA increases, surface tension increases Surfactant effects decrease therefore surface tension increases as alveoli size increases.
33
When does surfactant have the most effect?
When there is a smaller SA as more molecules are present in a given area
34
Pressure
P= 2T/r T - Surface tension r - radius
35
Respiratory distress syndrome
Premature babies under 30 weeks Do not produce surfactant therefore: - Decrease in compliance - stiff - Hard to expand
36
Resistance to flow
Tubes of smaller diameter have a higher resistance to flow Energy needed to overcome resistance Small decrease in radius - large increase in resistance (r^4)
37
Parallel lower airways
Numerous small airways running in parallel compensate for the increase in individual resistance
38
Upper respiratory system
Highest resistance as have a serial arrangement Wider tubes Cartilaginous rings - reduce compression Lowest resistance in lower airways except when compressed during forced expiration