List the physiological factors that increase respiratory rate. Include an explanation of the mechanism by which each achieves this increase.
The main points candidates were expected to cover included:
· A description of the central and peripheral chemoreceptors, their predominant stimuli and
effect on ventilation.
· PaCO2 as the main influence on normal ventilation, the near-linear relationship to minute
ventilation around the normal range, and how CO2 produces this effect.
· PaO2 and pH and their sites of action.
· Other stimuli to ventilation – exercise, pregnancy, temperature, baroreceptors.
Candidates frequently confused central and peripheral receptor activities and failed to provide
any relative significance to the major factor(s). The use of a graph relating the main factors
to minute ventilation would have been helpful.
Reference: Nunn 6th edition 60-68
Kam 1st edition 92-98