Pulmochart Reference
Mechanical ventilation

Mechanical ventilation


There are different ventilation modes, which influence respiratory analysis. While some ventilation mode lead to characteristic analysis results, other ventilation modes might lead to unexpected results, due to the implementation of the analysis algorithms.
Overall an interpretation of respiratory analysis results should take the measurement circumstances into consideration.

Furthermore, spontaneous breathing can occur during ventilation and might cause problems. Some algorithms, e.g., with respect to volumes do not expect spontaneous breathing and therefore do not handle such breaths separately.


Ventilation modes and their side effects:
There are mainly two types of ventilators, conventional mechanical ventilators and high-frequency ventilators, see [Rimensberger2015] p.150. Conventional ventilators deliver tidal volumes within the normal physiological range (tidal ventilation), while high-frequency ventilators deliver much smaller tidal volumes.

Generally, ventilation modes are distinguished according to their control variables of the tidal breaths, pressure or volume. The respective ventilation modes are pressure-controlled ventilation modes and volume-controlled ventilation modes.

Pressure-controlled ventilation modes:
Pressure-controlled ventilation modes or also called pressure-preset modes are characterized by the application of a predefined target pressure, see [Tobin2013] p. 141.
During ventilation, volume and flow vary with the impedance of the respiratory system and inspiratory efforts of the patient.
Pressure-controlled methods are no safeguard against ventilator-induced lung injury due to the risk of large volume fluctuations.

Pressure-controlled methods are e.g.,
-pressure-support ventilation (PSV)
-pressure-controlled ventilation (PCV)
-airway pressure release ventilation (APRV)
-positive pressure ventilation (PPV)
-negative pressure ventilation
-Positive pressure (mandatory) breaths (PPB)
-continuous positive airway pressure (CPAP) ventilation

Side effects of ventilation modes:
In CPAP ventilation the peak inspiratory pressure (PIP) corresponds e.g., to the applied pressure .

While pressure-controlled ventilation modes control the minimal and the maximal applied pressure, e.g., the PIP and the PEEP detection do not have to be very sensitive. But in volume-controlled ventilation modes, parameters, like PIP and PEEP might have to be calculated more sensitively.

Volume-controlled ventilation modes:
Volume-controlled ventilation modes, also called volume-preset modes are the most widely used ventilation modes, see [Tobin2013] p. 141. These ventilation modes are characterized by machine breathes with the same predefined inspiratory flow-time profile (which defines the volume).
Volume-controlled ventilation modes employ an increased risk of barotrauma.