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Physiology & Pharmacology of Systems > Introduction to the Respiratory System & Lung Mechanics > Flashcards

Introduction to the Respiratory System & Lung Mechanics Flashcards

1
Q

What is the difference between internal and external respiration?

A

Internal respiration = gas exchange between blood and cells/interstitial fluids

External respiration = exchange of gases between blood and the external environment

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2
Q

What X3 things are involved in external respiration?

I.e. what X3 things need to happen before we can get to the internal respiration stage?

A

1) pulmonary ventilation (breathing)
2) gaseous diffusion
3) transport of O2 and CO2

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3
Q

What formulae (no name needed but provide letters for each component) links air flow, pressure gradient and resistance?

What does this formula imply for the relationship between:

1) flow and pressure?
2) flow and resistance?

A

Flow (Q) = pressure gradient (p1-p2) / resistance (R)

1) flow ∝ pressure
2) flow ∝ 1/resistance

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4
Q

How would you exploit the flow, pressure, resistance formula to increase flow?

A

Either:

a) increase the pressure gradient
b) decrease the resistance

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5
Q

What is the shorthand notation for atmospheric pressure?

A

PB

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6
Q

What is the shorthand notation for pressure of air from the mouth/nose?

A

PM

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7
Q

What is the shorthand notation for alveolar pressure?

What does that make the shorthand notation for arterial pressure?

A

Alveolar = PA

Arterial = Pa

NB: as the alveoli come BEFORE the arterial blood in the chain of gas exchange in breathing.

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8
Q

What relationship needs to exist between PM and PB in order for inspiration to take place?

A

PM > PA

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9
Q

What relationship needs to exist between Pm and Pb in order for expiration to take place?

A

PA > PM

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10
Q

Explain Boyle’s law.

A

For a fixed number of gas molecules.

At a contestant temperature.

The pressure it exerts and the volume of the container it is occupying are inversely proportional.

P1V1 = P2V2.

Therefore P x V is always constant, and if one increases the other decreases.

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11
Q

Why is boyle’s law relevant for breathing?

A

Breathing involves increasing the volume (thoracic cavity) which in turn decreases the alveolar pressure causing air to be entrained.

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12
Q

Explain the types of recoil that exist in the chest at resting end expiration and the types of movement they are ‘wanting to do’.

A

Outward recoil exists = the chest wall wanting to ‘move outwards’

Inward recoil exists = the lungs wanting to ‘move in’

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13
Q

What is the effect of the opposing recoils between the chest wall and lungs at resting end expiration?

Give values.

A

It creates a negative intra-pleural pressure (PPL) between the parietal and visceral pleura which at resting end expiration = -5cmH2O.

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14
Q

What does -5cmH2O actually mean?

A

It means the pressure is -5cmH2O BELOW atmospheric pressure as respiratory pressures are expressed RELATIVE to PB.

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15
Q

Name X4 obligate (always used) inspiratory muscles.

A

1) diaphragm
2) external intercostals
3) scalenes
4) parasternal intercostals

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16
Q

Are there any obligate expiration muscles and why?

A

No, expiration (AT REST) is passive.

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17
Q

How long is a normal respiratory cycle?

What is the breakdown of this in terms of time spent inhaling and exhaling; which is longer?

A

5 seconds.

3 spent inhaling (longer).

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18
Q

What happens to pleural pressure (PPL) during X1 respiratory cycle?

A

It begins at a resting end expiration pressure of -5cmH2O.

It then decreases over the 3 seconds of inhalation to around -8cmH2O.

It then returns on exhalation to the resting end expiratory pressure of -5cmH2O.

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19
Q

What is alveolar pressure at resting end expiration?

A

0cmH2O, the same as PB. That is why there is no air movement!

20
Q

What happens to alveolar pressure during X1 respiratory cycle?

A

It begins at 0cmH2O.

During inspiration it decreases to around -1cmH2O below the atmospheric pressure which allows air to flow in.

It then returns back to 0cmH2O as inspiration comes to an end.

During expiration, as the chest wall relaxes, it increases to around +1cmH2O which causes air to leave. It gradually returns back to 0cmH2O as expiration comes to an end.

21
Q

What is positive and negative flow (graphically) in terms of inhalation and expiration?

A

Positive deflections on flow graphs = flow outwards

Negative deflections on flow graphs = flow inwards

22
Q

What happens to air flow during X1 respiratory cycle?

A

Air flow starts at 0L/sec.

It increases (negative flow = inhalation) to -5L/sec and then back to zero over the course of inspiration.

It then does the same in reverse to +5L/sec and then back to zero over the course of expiration.

23
Q

What is the name of the volume of air in the lungs after passive expiration?

A

Functional residual capacity.

24
Q

What is the name of the group of pressure used to predict the movement of the lungs and is measured across different compartments of the chest?

A

Transmural pressures.

25
Q

What is the key rule in remembering how to calculate the transmural pressures?

A

It is ALWAYS the inside compartment minus the outside compartment.

26
Q

Which X3 pressures make up the transmural pressures?

What are their shorthand notations?

What are their formulas?

A

Trans chest wall (PW)
= across the chest wall (between the pleural cavity and the atmosphere)
= PPL (pleural) - PB

Transpumonary (PL)
= across the lungs (between alveoli and pleural cavity)
= PA - PPL

Trans total system (PRS)
= across the whole system (between alveoli and atmosphere)
= PA - PB

27
Q

Is the transpulmonary pressure (PL) always positive or negative?

A

Positive.

28
Q

What is transpulmonary pressure (PL) also known as?

What happens when PL increases?

A

It is known as the ‘distending pressure’.

As it increases it inflates the lungs.

29
Q

What is the relationship between PL and elastic lung recoil?

A

They are equal and opposite in value.

30
Q

What is a normal FRC volume?

A

3500ml

31
Q

What is a normal TLC volume?

A

7300ml

32
Q

What does IRV stand for, what does it mean and what is a normal volume?

A

Inspiratory reserve volume = the volume that can be inspired beyond a normal inhalation (tidal volume).

Normal = 3300ml

33
Q

What does IC stand for, what does it mean and what is a normal volume?

A

Inspiratory capacity = the maximal amount that can be inspired including today volume.

Therefore it is tidal volume (500) + IRV (3300) = 3800ml.

34
Q

What does ERV stand for, what does it mean and what is a normal volume?

A

Expiratory reserve volume = the volume that can be expired beyond a normal expiration.

Normal = 1700ml.

35
Q

What does RV stand for, what does it mean and what is a normal volume?

A

Residual volume = the volume of air remaining in the lungs after maximal expiration.

Normal = 1800ml.

36
Q

What is dead space?

What is its shorthand notation?

A

The volume of conducting airway not involved in gas exchange.

Dead space = Vd

37
Q

What are the X2 types of dead space and what do they include?

What is a normal value for the first kind of dead space?

A

Anatomic
= all of the airway except alveoli and respiratory bronchioles.
= usually around 150ml.

Physiologic
= anatomical dead space + areas where gas exchange should take place but is dysfunctional.

38
Q

What is the normal ratio of anatomic Vd to physiological Vd?

A

Normally equal in health.

39
Q

What is minute ventilation and how is it calculated?

A

Minute ventilation = volume of air moved into OR out of the lungs in a minute.

Tidal volume = 500ml
RR = 15/min

500 x 15 = 7500ml/min

40
Q

How can we calculate alveolar ventilation?

A

Alveolar ventilation = minute ventilation - dead space ventilation.

Minute ventilation = 7500
Anatomic dead space = 150ml
RR = 15/min

150 x 15 = 2250ml/min

7500 - 2250 = 5250ml/min = alveolar ventilation.

41
Q

What can we note about normal alveolar ventilation and pulmonary perfusion?

A

Alveolar ventilation (V) = 5250ml/min

Pulmonary blood flow (perfusion) (Q) = SV x HR
SV = 70ml
HR = 70bpm

70 x 70 = 4900ml/min

Therefore V and Q are matched in health!
The V/Q ratio = 1!

42
Q

Which X2 resistances must we overcome in order to inhale?

NB: these are both areas which will change in disease states so think about it in that respect.

A

1) the elastic resistance of the lung

2) the airway resistance to airflow (usually in expiration)

43
Q

What is the technical term for lung elastic resistance/stiffness?

A

Compliance.

44
Q

What formula denotes lung compliance?

A

Compliance = change in lung volume (V) / change in transpulmonary pressure (PL)

Therefore high compliance means large changes in lung volume for small changes in transpulmonary pressure.

45
Q

Which pressure increases and turns positive in forced expiration?

A

Pleural pressure (PPL)

46
Q

What class of drugs cause bronchoconstriction and what receptors do they act on?

A

Cholinergic agonists acting on M3 receptors.

47
Q

Explain how dynamic compression of the airways works?

A

During forced expiration, the intrapleural (PPL) pressure is made positive and rises above the pressure in the airways. This forces them shut and blocks air exiting.

Physiology & Pharmacology of Systems (21 decks)

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