Lung Volumes

Question 1

Total Lung Capacity

Answer 1

> Total volume of gas in lungs after max inspiration (average is between 3-8L depending on size + sex)
I.e max we can hold

Question 2

Vital Capacity

Answer 2

> Amount that can be exhaled after max inspiration (between 3-6L)
Max breath out

Question 3

Residual Volume

Answer 3

> Amount remaining after full expiration
keeps lungs open + makes inspiration easier
first and last breaths

Question 4

Expiratory Reserve Volume

Answer 4

> Extra gas can be exhaled after tidal volume breath out

> I.e extra breath out after relaxed/normal breath out

Question 5

Inspiratory Reserve Volume

Answer 5

> Extra gas can be inhaled after tidal volume breath in

> I.E extra breath in after relaxed/normal breath in

Question 6

Functional Residual Volume

Answer 6

> Volume remaining after tidal volume breath out
Expiratory reserve + residual volumes
*Increased in hyperinflated but decreased in restrictive conditions (closer to closing volume)

Question 7

Tidal Volume

Answer 7

> Volume of air breather in and out in a single respiratory cycle (resting volume)
~300-800ml

Question 8

Closing Volume

Answer 8

> Volume (above residual volume) at which Alveoli start to collapse
Will increase with age/smoking/disease/position
Yawn or sigh is normal way to prevent airway collapse

Question 9

Lung volumes depend on

Answer 9

> Body Size
> Age 
> Sex 
> Muscular training 
> lung pathology

Question 10

Dead space

Answer 10

> Air not used in gas exchange

• anatomical (gas in upper airways)
• alveolar (lack of blood means no gas exchange)
• physiological is above combined
• We should avoid increasing dead space wherever possible to maximise V/Q ratio (e.g ventilation tube will increase anatomical dead space)