Scireq flexivent, User Manual, Page: 19 / 86

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1.4 THEORY OF OPERATION
As is mentioned in section 1.1, the flexiVent is a computer controlled piston ventilator. The
computer control afforded by
flexiWare
software makes the
flexiVent
versatile because you
control the parameters of the ventilation and measurement manoeuvres that it executes. Its
design adds to its versatility in part because it may be used with a range of subject sizes, but
also because it allows for the integration of a variety of accessories and hardware extensions,
which includes both SCIREQ products and third-party products.
1.4.1 RESPIRATORY MECHANICS
Generally speaking, mechanics is the relationship of objects and the forces that act upon them.
Respiratory mechanics is a way to quantify the airway constriction and stiffness of the lungs
through relationships between pressure, volume and flow using mathematical models.
1.4.2 FORCED OSCILLATION TECHNIQUE
Measurement manoeuvres executed by the flexiVent are referred to as perturbations. During a
perturbation, an iso-volume ventilator compartment is established when the valves within the
module close to the outside environment. The ventilator compartment consists of the subjects
respiratory system, the cylinder, pathways outside the module (e.g. Y-tubing) and pathways
within the module (e.g. from the cylinder to the Y-tubing). Once the valves are closed, the
perturbation, or Forced Oscillation, is applied to the ventilator compartment through movement
of the piston (see Figure
1-3). The signals generated during the perturbation are used to
calculate parameters of respiratory mechanics that help to quantify acute and/or chronic
disease-related changes to the lungs.