lecture 2: ventilation

Question 1

what are the two main components to the chest wall?

Answer 1

• bone and muscle and fibrous tissue
• the lungs

Question 2

ribcage and lungs

what are the natural tendencies of both the rib cage and the lungs?

Answer 2

• the ribcage recoils outwards
• the lungs recoil inwards

Question 3

what is the volume and pressure of the pleural cavity?

Answer 3

• fixed volume
• and contains protein-rich negative fluid
• there is negative pressure

Question 4

what is the functional residual capacity?

Answer 4

• when we are at the end of tidal expiration
• at the end we are at FRC when both the lungs and the ribcage are in equilibrium

Question 5

what is the importance of the pleural cavity?

Answer 5

• it is the link between the lungs and the chest wall
• if we do a full inspiration we are expanding the chest wall as well as pulling the diaphragm down
• so the chest wall needs to pull the lung with it
• the negative pressure of the pleural cavity allows the chest wall to pull the lungs with it

Question 6

what happens to the pleural cavity with a punctured lung?

Answer 6

• if you have a puncture in the chest wall
• the fixed volume pleural cavity is compromised
• air will fill the pleural cavity the elastic recoil will take over and the lung will collapse

Question 7

what is the difference with a haemothorax?

Answer 7

• this occurs much slower

Question 8

what is hyperventilation?

Answer 8

excessive ventilation of the lungs atop of metabolic demand

Question 9

what is hypoventilation?

Answer 9

Deficient ventilation of the lungs; unable to meet metabolic demand

Question 10

*show a diagram of a labelled lung volume and capacity graph :

Answer 10

*

Question 11

what is the tidal volume?

Answer 11

normal breathing volume - it can increase during exercise

Question 12

what is inspiratory reserve volume?

Answer 12

how much extra air you can draw in after a breath in

Question 13

what is expiratory Reserve volume?

Answer 13

how much extra air you can breathe out after a normal breath in

Question 14

residual volume?

Answer 14

the volume left in the lungs after normal expiration

Question 15

what factors affect the lung volume and capacity?

Answer 15

• body size - sex (men are bigger) - fitness - disease - age

Question 16

what is dead space?

Answer 16

these are areas on the airway that do not participate in gas exhange

Question 17

what are the two types of dead space?

Answer 17

anatomical dead space -

alveolar dead space -

non perfused parenchyma (alveoli without a blood supply)

the conducting zone is dead space

Question 18

what are the two distinct parts of the lungs?

Answer 18

• conducting zone - anatomical dead space - respiratory zone - split into 7 generations

Question 19

*show a diagram of dead space:

Answer 19

*

Question 20

how to increase dead space ?

Answer 20

• use a ventilator

Question 21

how to decrease the dead space?

Answer 21

• tracheostomy

Question 22

what is

transmural pressure

transpulmonary pressure

transrespiratory pressure

Answer 22

transmural = across several tissues

transpulmonary = difference between alveolar and intrapleural pressure

transrespiratory pressure = tells us if there is airflow into or out of the lung

Question 23

what is the snorkel analogy saying?

Answer 23

a longer snorkel means more dead space which means the lungs may not be able to shift - poiseuilles law: a decrease in diameter by a half increases resistance by x16

Question 24

how does the alveolar volume and pressure in alveolar change ?

Answer 24

• at the start there is no transpulmonary pressure - there is no pressure change - the chest wall expands and creates the negative pressure - the pressure gradient is established - the pressure gradient equalises

Question 25

how to work out the orientation of the gradient?

Answer 25

inside - outisde

Question 26

how do we normally inspire? in terms of pressure

Answer 26

- we inspire when there is a lower pressure inside the lungs - it is possible to ventilate using positive pressure breathing this is when we increase the pressure outside by using a ventilatory or CPR

Question 27

what is the chest wall relationship?

Answer 27

- the elastic recoil of the lungs inwards and the outward recoil of the rib cage are in equilibrium - the lungs are surrounded by a visceral pleural membrane whilst the inner surface in covered in a parietal membrane

Question 28

what does breaching in the pleural cavity result in?

Answer 28

- haemothorax - bleeding in chest cavity - pneumothorax - perforated chest wall

Question 29

how is air flow generated?

Answer 29

- goes from high pressure - to low pressure \*\*\*\*\*

Question 30

what is negative pressure breathing?

Answer 30

this is inspiration with a lower pressure in the lungs (NORMAL)

Question 31

what is positive pressure breathing?

Answer 31

- this is pressure increased abnormally in situations like CPR and ventilation

Question 32

what is transmural pressure?

Answer 32

pressure inside - pressure outside this is the pressure across the tissues a positive transmural pressure leads to expiration

Question 33

what is transpulmonary pressure?

Answer 33

- this is a difference between the alveolar and interpleual pressure this pressure dictates the airflow

Question 34

what is the chest wall relationship graph?

Answer 34

\*\*\* will go over in later lecture

Question 35

how are lung function tests carried out?

Answer 35

- patient wears nose clip and inhales to total lung capacity - the patient exhales as hard and fast as they can until 6 seconds have passed - inspect the graph and look for -slow starts - early stops or - intramanouver variability

Question 36

how to calculate the FEV1/ FVC ratio? (forced vital capacity)

Answer 36

volume of air forced out in 1 second / volume of air at max inhalation

Question 37

what does obstructive lung disease do to the lung function tests?

Answer 37

FEV1 and FVC is much lower while FET is much higher (takes longer to expel). - forced expiratory time

Question 38

what do restrictive lung diseases do to the lung function tests?

Answer 38

FVC is lower while FEV1 is relatively high as the airway conduction pathway is clear (not like in COPD).

Question 39

what does the volume time graph look like?

Answer 39

\*\*

Question 40

what peak flow test?

Answer 40

this measures the force of exhalation instead of the volume or time taken

Question 41

how to measure the peak flow?

Answer 41

look at the graph which is peak expiratory flow rate / age and look at the max point

Question 42

how to calculate alveolar ventilation

Answer 42

\*\*

Question 43

how to calculate alveolar ventilation

Answer 43

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