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PHYSIOLOGY FRCA > Respiratory > Flashcards

Respiratory Flashcards

1
Q

How does compliance vary with lung volume?

A

Lower at high and low lung volumes.
If you draw out pressure volume curve - it is a sigmoidal shape. the gradient is compliance hence since it is not a linear curve it shows it varies with lung volume

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2
Q

what factors decrease and increase lung compliance?

A

decreased - fibrosis, oedema
increased - elderly, emphysema

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3
Q

what are the units for compliance of a lung. what is roughly the normal value for compliance of the lung?

A

0.1 L/ cm H20

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4
Q

How is dynamic compliance related to the frequency of ventilation

A

inversely related.

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5
Q

how is physiological and anatomical deadspace related?

A

physiological DS = anatomical DS + alveolar DS

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6
Q

how does dead space change with changes in tidal volume?

A

Changes in lung volume affect conducting airway diameter and pulmonary vascular resistance, altering regional pulmonary blood flow and V/Q ratios throughout the lung.

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7
Q

how can physiological dead space be calculated?

A

Bohr equation -
VD/VT = (PaCO2 - PECO2)/PaCO2 (PACO2 is assumed to equal PaCO2)

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8
Q

how does the resistance change in bronchioles as lung volumes increase?

A

increase in lung volume, diameter of bronchioles increases, resistance decreases.

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9
Q

can terminal bronchioles collapse in expiration?

A

yes with forced expiration or in disease states

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10
Q

what is the closing volume?

A

Closing volume is the volume above residual volume at which measurable small airways closure occurs.

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11
Q

do terminal bronchioles have abundant smooth muscle?

A

yes

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12
Q

how do PO2 and PCO2 affect minute volume ?

A

PO2 increases resp expontentially when below 7Kpa

PCO2 - proportional increase in MV with increase in PCO2. however above 10kpa this is diminished = carbon dioxide narcosis

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13
Q

what is closing capacity equal to?

A

closing volume + residual capacity

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14
Q

how does closing capacity change with lying down?

A

increaases

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15
Q

how does closing capacity change with age?

A

increases with age

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16
Q

how does intrapleural and alveolar pressure change with inspiration ?

A

intrapleural pressure - decreases -5 to -8

intralveolar pressure - decreases

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17
Q

what is equation for total compliance of lung?

A

1/CTOTAL = 1/CLUNG + 1/CCHEST WALL

Compliance of the lungs is approximately 200 ml.cm H2O-1 and that of the chest wall is also 200 ml.cm H2O-1. Total compliance, 1/CTOTAL = 1/CLUNG + 1/CCHEST WALL (c.f. resistance of two electrical resistors in parallel) = 100 ml.cm H2O-1.

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18
Q

how does dynamic compliance compare to static compliance?

A

Dynamic compliance is always less than static compliance.

Dynamic - when breathing , includes lung / chest wall elastic compliance and resistance to breathing.
Static - when no air flow , only affected by lung and chest wall.

19
Q

how does lung compliance change with age?

A

increases

20
Q

how is CO2 carried in blood?

A

As HCO3 - bicarbonate (main way ) (NOT Carbonate)

as carbamino compounds - with Hb mainly but also plasma protiens

dissolved in blood

21
Q

what type of shunt will reduce PaO2 of blood?

A

right to left
(be careful with direction in MCQ)

22
Q

how does PaO2 alter with exercise or hyperventilation?

A

exercise - relatively constant

hyperventilation - drop in CO2 hence increase in PaO2 as per alveolar gas equation

23
Q

is deadspace negligble in healthy adults?

A

no there is still some anatomical and alveolar dead space

24
Q

how is deadspace calculated?

A

alveolar = bohr equation
anatomical = fowlers method- one breath N2

25
Q

what can increase bronchi diameter?

A

inspiration
sympathetic NS - hence exercise

reduced by coughing

26
Q

how does glucagon affect the heart

A

increases contractility
GPCR –> increase cAMP

27
Q

how does increasing extracellular calcium affect myocardial contractility ?

A

increases heart contractility

28
Q

how does acidosis affect myocardial contractility?

A

inhibits it

29
Q

how does pH and CO2 affect pulmonary vasculature?

A

A low blood pH and/or high CO2 cause pulmonary vasoconstriction, a direct effect of CO2 itself.

30
Q

how does vagus nerve/ parasympathetic effect anatomical deadspace?

A

bronchoconstriction –> less anatomical dead space

31
Q

how can pCO2 and pH be presented graphically

A

a plot of log PCO2 on x axis
against pH on y
straight line in the physiological range - negative gradient i.e high ph = low co2

32
Q

what is the equation for surface tension?

A

Surface tension may be defined as energy per unit area or force per unit length.
P = 2T/r, so T = Pr/2,
expressed in S.I. units = N.m-1

33
Q

is surface tension bigger in small or larger alveoli?

A

T=Pr/2 - the larger the radius, the bigger the tension

34
Q

what is the intrapleural pressure during normal breathing?

A

Intrapleural pressure is approximately -5 cm H2O at end-expiration. During inspiration, intrapleural pressure falls further to approximately -8 cm H2O

35
Q

how is intrapleural pressure measurements estimated?

A

oesophageal pressures

36
Q

how does the intrapleural pressure between base and apex of the lung compare?

A

Thus the pressure at the base is higher (less subatmospheric) than that at the apex.

37
Q

how does intrapleural pressure change in valsalva?

A

increases above atmospheric

38
Q

what does the helium dilution test measure and is this an over estimate or underestimate?

A

FRC
underestimate - excludes unventilated areas of the lung behind closed airways.

39
Q

what is a normal value for FRC in an adult male?

A

2.5-3 L

40
Q

how does CO2 alter CBF?

A

vasodilation hence increase in blood flow in a linear fashion.

41
Q

which area of the brain does CO2 affect arousal?

A

reticular activating system

42
Q

what is normal CO2 for arterial and mixed venous blood?

A

mixed venous - 6.1
arterial 5.3 kpa

43
Q

what is the CO2 and O2 content of arterial blood?

A

The arterial oxygen content of blood is approximately 200 ml.L-1. Arterial carbon dioxide content is approximately 480 ml.L-1.

44
Q
A

PHYSIOLOGY FRCA (10 decks)

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