Summary Physiology; spirometry and control of breathing review

28/03/19

Dr Rachel O’Callaghan

Spirometry and Control of Breathing
Ventilation

• Tidal volume (VT) = total volume of air moved in one ventilatory cycle
o Not all air used for gaseous exchange (anatomic, alveolar)
• Minute ventilation = volume of air moved in and out of lungs in one minute
o Minute ventilation = VT x f
• Alveolar minute ventilation = volume of air exchanged between atmosphere and alveoli per
minute
o Alveolar ventilation = (VT – VD) x f

Large tidal volume required for organisms with long trachea etc, humans only have 500ml

Spirometry

• Traditional wet spirometer
o Air filled drum in water filled chamber
o Person breathes through tube to air chamber
o Drum rises and falls during respiratory cycle
▪ Spirogram (volume-time curve)
• Volume-time curve
o Volume (ml) on Y axis, time (s) on X axis




Name Full Name Explanation
TV/VT Tidal volume Volume of air leaving lungs in single breath
IRV Inspiratory reserve volume Extra volume of air for maximum inspiration
IC Inspiratory capacity IRV + VT
ERV Expiratory reserve volume Extra volume of air for maximum expiration
RV Residual volume Minimum volume of air remaining after max expiration
FRC Functional residual capacity ERV + RV
VC Vital capacity VT + IRV + ERV
TLC Total lung capacity Maximum volume the lungs can hold (VC + RV)