ResMed C28173 Manual page 14

248476r4.book Seite 8 Freitag, 28. Oktober 2011 3:10 15
Unintentional leak
Mask vent leak
Unintentional leak may arise due to factors such as poor mask fit, mask movement during sleep,
and fast therapy pressure transitions. When an unintentional leak is introduced (see below
graph), synchrony between the device and the patient is disrupted. The increased flow from a
leak can be interpreted as patient inhalation and cause the ventilator to trigger from EPAP to
IPAP out of time with the patient's actual effort (A). Vsync responds rapidly to correct the
disruption and restore synchrony within 2-6 breaths (B) depending on the patient's respiratory
rate and the size of the leak.
Therapy Pressure
Patient Effort
Unintentional leak
True Respiratory Flow
Unintentional leak flow varies with changes to therapy pressure or the size of the leak opening.
Vsync calculates changing leak by:
monitoring average pressure and flow
•
assuming that on average volume delivered to the patient is equal to volume exhaled by the
•
patient
using this information to continuously estimate the size of the leak opening as it changes
•
calculating the air flowing through the opening, knowing its size and the therapy pressure.
•
8
Total flow
Unintentional leak introduced
Total Flow
Patient respiratory flow
Period of asynchrony
A B