Figures
- FIGURE 1
Schematic diagram depicting the function principles of a device for applying automatic continuous positive airway pressure (CPAP) (see text for explanation). V′ and Pao are flow and pressure measured at the patient's airway opening.
- FIGURE 2
a) Schematic diagram of the function principles of a noninvasive mechanical ventilator. b) Diagram of conventional noninvasive mechanical ventilators. Pressure-controlled ventilators are described by the black and red components. Flow/volume-controlled ventilators are described by the black and blue components. V′ and Pao are flow and pressure measured at the patient's airway opening. c) Diagram of advanced ventilators. Pressure regulated volume control ventilators are described by the black, red and magenta components. Proportional assist ventilation devices are described by the black, blue and magenta components. Neural adjusted ventilation assist devices are described by the black and green components. See text for explanations.
- FIGURE 3
Bench test setting for automatic continuous positive airway pressure (APAP) devices. a) System to simulate the breathing pattern and airway obstructions in patients with sleep disordered breathing. V′: flow; P: pressure; EP: exhalation port; PNT: pneumotachograph. Reproduced from [15] with permission from the publisher. b) Diagram of the different sleep sections in an example of whole-night simulated patient (see text for explanation).
- FIGURE 4
Pressure applied by different automatic continuous positive airway pressure devices in a bench test over a full simulated night (grey line). Blue lines are the pressure required to fully normalise breathing (avoiding, apnoeas, hypopneas and flow limitation) and red lines are the pressure required to avoid apnoeas. A device that delivered pressures above the blue line achieves full breathing normalisation, while if it delivered pressures just above the red line only obstructive apnoeas were overcome.
- FIGURE 5
a) Experimental system to carry out a bench test of noninvasive ventilators. V′: flow into the lung chamber; V′c: flow delivered by the ventilator; Paw: airway pressure. Reproduced from [36] with permission from the publisher. b) Commercially available lung simulators to test mechanical ventilators (www.ersbuyersguide.org/features/category/lung-simulation). Some patient simulators for ventilation are passive (resistance–compliance systems) and some of them are computerised patient models allowing to easily simulate lung resistance and compliance and to activate inspiratory pressures simulating the patient's muscles activity.
- FIGURE 6
Results from a recent bench test of 13 noninvasive ventilators using a computer-controlled active patient simulator. a) Proportion of the preset tidal volumes (VT) actually delivered, without leakage and with mild continuous leakage. *: p<0.05 between conditions without leakage and with mild continuous leakage. b) Trigger performance in noninvasive pressure support ventilation. Inspiratory delays, triggering delay (ΔT) and pressurisation delay (PD), in response to moderate and strong inspiratory efforts, without leakage and with calibrated, mild and severe continuous leakage. Reproduced from reference [36] with permission.
