Original sentence: Q can also be affected by the phase of respiration with intra-thoracic pressure changes influencing diastolic filling and therefore Q.This is important especially during mechanical ventilation, and Q should therefore be measured at a defined phase of the respiratory cycle (typically end-expiration)
Edited sentence: Q can also be affected significantly by the phase of respiration; intra-thoracic pressure changes influence diastolic filling and therefore Q.Q should therefore be measured at evenly spaced points over a single cycle or averaged over several cycles.This is especially important during mechanical ventilation where Q can vary by up to 50% across a single respiratory cycle