Respiratory - Mechanics of breathing

Question 1

In mammals, what s respiration considered?

Answer 1

Tidal

Question 2

After a relaxed breath, what is the air left over in the lungs? How much is this normally?

Answer 2

Functional residual capacity, ~2.5L

Question 3

During inspiration, what is the volume that is changing called? What is this volume?

Answer 3

The tidal volume, ~0.5L

Question 4

What is the volume left over after maximal expiration called (voluntarily)? What is the volume?

Answer 4

Residual volume, ~1L

Question 5

When you do a maximum inspiration, what is this volume called? What is this directly correlated to and what is it approximately?

Answer 5

Total lung capacity is directly related to height and is ~5L

Question 6

What is the ventilation rate approximately? How is this calculated?

Answer 6

0.5L * 12min-1 = 6Lmin-1

Question 7

During exercise how does the ventilation rate change?

Answer 7

3L * 40min-1 = 120Lmin-1 –> greatly increases

Question 8

In order for inspiration to occur, what must be the relative pressure? What is the equation that describes this?

Answer 8

The barometric pressure (P_B) must be higher than alveolar pressure (P_A)

dV/dt (rate of air flowing into lungs) = (P_B - P_A) / R (resistance to air flow)

Question 9

Label the diagram, what do each of the force/pressure symbols mean?

Answer 9

F_CW = force chest wall

F_L = force on the lungs

P_IP = Pressure intrapleural space

Question 10

What is the relationship between F_CW (force on the chest wall) and F_L (force on the lungs)

Answer 10

F_L = -F_CW

Question 11

What is the tendency of the lungs? Why?

Answer 11

They ten to collapse to zero volume because they are highly elastic

Question 12

What is P_IP? What is the location and cause of it?

Answer 12

Intrapleural pressure

It is located between the visceral and parietal membrane of the lungs and it is caused by the negative pressure exerted by the water which keeps the layers of membrane together

Question 13

What causes the F_L?

Answer 13

The elastic recoil from the stretch elastic fibres and surface tension of the wet alveolar cells

Question 14

What causes the F_CW?

Answer 14

The stretched tissue in the sterno-costal joint (connection point between the sternum and the ribs) and costo-vertebral joint (connection point between the ribs and the spinal cord)

Question 15

What is pneumothorax?

Answer 15

When a penetrating injury of the chest wall create a connection between the atmosphere and the intra plural space which means there is air inside the pleural fluid (i.e. intrapleural space)

Question 16

What is the affect of pneumothorax on the pleural membrane? Why?

Answer 16

It causes them to seperate because they are not held together by the water layer

Question 17

What is the affect of pneumothorax on inspiration volume? Why?

Answer 17

There is a lower inspiration volume because the visceral pleura doesn’t follow the parietal membrane which means that lungs don’t expand when the F_CW increases (i.e. chest expands) and the diaphragm contract

Question 18

What is the affect of pneumothorax on lung and chest wall structure? Why?

Answer 18

The lung will collapse because of the elastic properties of the lungs to recoil inwards and the chest wall will recoil outwards (i.e. expand) because of the outwards force exerted by the stretched tissue in the stereo-costo and costo-vertebral joints

Question 19

What is the barometric pressure? What is the value?

Answer 19

The air pressure at sea-level is 760mmHg