Ch.5 Pulmonary Function Measurements

what are the 4 lung volumes?

1. inspiratory reserve volume

2. tidal volume

3. expiratory reserve volume

4. residual volume

what is inspiratory reserve volume (IRV)?

amount of air that can be forcibly inhaled beyond Vt

what is expiratory reserve volume? (ERV)

the amount of air that can be forcibly exhaled after a normal Vt

what is tidal volume? (Vt)

the amount of air inhaled and exhaled with each breathe during quiet breathing

(inspiration & expiration)

what is residual volume? (RV)

the amount of air still in the lungs after a forced ERV

what are the 4 lung capacities?

1. inspiratory residual capacity

2. functional residual capacity

3. vital capacities

4. total lung capacities

what is inspiratory residual capacity? (IRC)

the vol of air that can be inhaled during normal exhalation

IRV + Vt

what is functional residual capacity? (FRC)

volume of air remaining in the lungs after a normal exhalation 

ERV + RV

what is vital capacities? (VC)

the max vol of air that can be exhaled after max inspiration

IRV + Vt + ERV

what is total lung capacities?

max amt of air the lungs can accommodate

ERV + Vt + IRV + RV

what effects does obstructive diseases have on PFTs (pulmonary function testing)

•affects VC, airflow limitation, ↓ expiratory flow, high airway resistance

• ↓ in FEV1

• normal or slight ↓ in FVC

• ↓ 70% of FEV1/FVC

•difficulty exhaling

what effects does restrictive diseases have on PFTs (pulmonary function testing)

• ↓ both FEV1 and FVC

• normal FEV1/FEVC

• low lung compliance

• ↓ lung volume & capacities

• difficulty inhaling, pneumonia, atelectasis

normal FEV1

83 or 80 %

normal FEV0.5

60%

normal FEV2 vs FEV3

94 % vs 97%

how do you calculate FEV1 and FVC ratio?

•divide (Height, age, gender,ethnicity) by predicted number

• <70 FEV1/FVC is obstructive

FEV1/ FEV2 × 100

what is peak flow rate (PF)? what is it used for?

• highest instantaneous flow achieved during FVC maneuver

• max attainable expiratory flow rate

• measures velocity & flow rate

• determined by large airway diameter

• occurs during early forced expiration

what is a normal flow-volume loop?

• graphic presentation of FVC maneuver followed by forced inspiratory vol (FIV) maneuver

• smooth, bell-shaped loop, with a symmetrical inspiratory limb and a linear, convex expiratory limb

• absence of significant airflow obstruction or restriction

what is an obstructive flow-volume loop?

•delayed and prolonged expiratory flow, often described as "t" or "dipping," with a low peak expiratory flow and a prolonged expiratory phase that doesn't reach zero

condition that narrows the airways, such as:

• Asthma 

• COPD (chronic bronchitis, emphysema) 

• Large airway tumors 

what is a restrictive flow-volume loop?

•reduced overall lung volume but maintains a relatively normal shape and flow, with an inspiratory limb that rapidly decreases in flow and a shortened, but usually linear, expiratory limb

condition that limits lung expansion, such as:

• Interstitial lung disease 

• Kyphoscoliosis 

• Weakness of respiratory muscles 

• Obesity 

what factors affect predicted normal values of obstructive and restrictive flow-volume loop?

age, sex, height, race/ethnicity, weight/body comp, effort/technique

what are the 3 methods for measuring RV

• open circuit helium dilution method →amt of helium in the lung-spirometer system is the same at the end of the test as at the beginning

• closed circuit nitrogen washout → usually ends when expired nitrogen is < 2%

• body plethysmographic method → measures pt’s lungs (most accurate)

what is minute ventilation?

• total vol moving in or out of lungs per min

VE= fB (frequency of breathing) x VT