HUMB1000 4.4 Respiratory Volumes & Capacities

Tidal Volume

Amount of air inspired or expired with each breath

Inspiratory reserve volume

Amount of air forcefully inspired after inspiration of tidal volume

Expiratory reserve volume

Amount of air forcefully expired after expiration of tidal volume

Residual volume

Volume of air remaining in lungs after forceful expiration

Inspiratory Capacity.

Amount of air inspired maximally after normal expiration

(Tidal volume + inspiratory reserve volume)

Functional residual capacity

Amount of air remaining in lungs after normal expiration

(Expiratory reserve volume + residual volume)

Vital capacity

Maximum volume of air expelled from lungs after maximum inspiration (Inspiratory reserve volume + tidal volume + expiratory reserve volume)

Total lung capacity

Inspiratory reserve volume + expiratory reserve volume + tidal volume + residual volume

Respiratory rates

Number of breaths taken per minute

Minute ventilation

Total amount of air inspired & expired per minute
(Tidal volume x respiratory rate)

Anatomic dead space

Space formed by nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles & terminal bronchioles

Alveolar Ventilation

Volume of air available for gas exchange per minute

Forced vital capacity

Maximal volume of air forcefully expired as fast as possible after deep inspiration

Forced expiratory volume in 1 second (FEV _{1 SEC})

Volume of air expired in first second

Forced expiratory volume 1% (FEV _1%)

FEV _1% = (FEV _{1 sec} / FVC) x 100  

Dynamic lung function

Lung volume measured in relation to time during repetitive breathing

Static lung function

Determined during one maximal inspiration or expiration

Fives static lung volumes

Tidal volume

Inspiratory & vital capacity

Inspiratory & expiratory reserve volume

Obstructive lung diseases

Normal lung volume & narrow airways (Asthma)

Restrictive lung diseases

Overall decrease in lung volume (pneumonia)

Obstructive lung disease (FEV)

Normal FVC

Severly reduced FEV _{1 SEC} & Fev _1%

Restrictive lung diseases (FEV)

Severely reduced FVC

Slightly reduced FEV _{1 SEC}

Normal Fev _1%