Lung physiology 2

Question 1

FEV1

Answer 1

forced expiratory volume in one second

Question 2

FVC

Answer 2

forced vital capacity

Question 3

PEF

Answer 3

peak expiratory flow (rate)
• Single measure of highest flow during expiration
• Peak Flow Meter, spirometer
• Gives reading in L/min
• Very effort dependent
• May be measured over time, by giving a patient a PEF meter and chart

Question 4

RV

Answer 4

residual volume

Question 5

IC

Answer 5

inspiratory capacity

Question 6

TLC

Answer 6

total lung capacity

Question 7

forced expiration

Answer 7

breath in to total lung capacity (TLC), exhale as fast as possible to residual volume (RV), volume produced is the vital capacity (FVC)

Question 8

Gas dilution

Answer 8

• Measurement of all air in the lungs that communicates with the airways
• Does not measure air in non-communicating bullae
• Gas dilution techniques use either closed-circuit helium dilution or open-circuit nitrogen washout.
• Usually, the patient is connected at the end-tidal position of the spirometer, measuring FRC

Question 9

total body plethysmography (body box)

Answer 9

• Alterative method of measuring lung volume, (Boyle’s law), including gas trapped in bullae.
• From the FRC, patient “pants” with an open glottis against a closed shutter to produce changes in the box pressure proportionate to the volume of air in the chest.
• The volume measured (TGV) represents the lung volume at which the shutter was closed

Question 10

TLC =

Answer 10

VC + RV

Question 11

transfer estimates

Answer 11

Carbon monoxide used to estimate DLCO, as it has high affinity for binding to haemoglobin
DLCO is an overall measure of the interaction of;
• alveolar surface area
• alveolar capillary perfusion
• physical properties of the alveolar capillary interface
• capillary volume
• haemoglobin concentration, and the reaction rate of carbon monoxide and hemoglobin.
Single 10 second breath-holding technique
• 10% helium, 0.3% carbon monoxide, 21% oxygen, remainder nitrogen.
Alveolar sample obtained;
• DLCO is calculated from the total volume of the lung, breath-hold time, and the initial and final alveolar concentrations of carbon monoxide.

Question 12

Compliance

Answer 12

• Compliance of the lung
• Change in volume per unit change in pressure gradient between the pleura and the alveoli; (transpulmonary pressure)
• Can be measured during breath-hold;
STATIC COMPLIANCE
• Can be measured during regular breathing;
DYNAMIC COMPLIANCE

Question 13

measured values

Answer 13

• Normal ranges
• Each measured value has its own normal range
• Derived normally from regression equations based on normal populations
• Wide range of values hence normal
• Lowest 5% arbitrarily defined as abnormal (and upper 5%)