A: Machine-triggered intermittent mandatory ventilation (IMV) with inadequate patient triggering of mandatory breaths. The patient is receiving pressure-controlled, time-cycled, continuous-flow IMV. Points A-C are unassisted spontaneous breaths. At point D the patient begins to exhale, but before exhalation begins, a positive pressure breath is delivered, resulting in breath-stacking and patient-ventilator asynchrony. B: Synchronized intermittent mandatory ventilation. All of the mandatory breaths are patient-triggered and delivered appropriately by the ventilator. (Adapted from Reference 6, with permission.)
Neurally adjusted ventilatory assist (NAVA) ventilation is triggered by the electrical activity of the diaphragm. Traditional ventilation modes are triggered by airway pressure or flow. (Adapted from Reference 31 and 32.)
Ventilator screen during testing of adaptive pressure control (volume-targeted) ventilation with the VN500 ventilator and a neonatal test lung. The set tidal volume (VT) was 5 mL, and the simulated ETT leak was calculated at 88%. The arrows point to the inhaled and exhaled VT, measured at the proximal flow sensor. The VT value displayed in the box is the estimated volume delivered to the lung model after subtracting the leak volume. This is the volume measurement used by the adaptive pressure control algorithm. The VT measured in the lung model was identical to the estimated delivered VT and the pre-set volume (data not shown).
Pressure and flow waveforms show that excessive inspiratory time causes active exhalation. The spikes at the end of each inspiration indicate that the patient is forcibly exhaling due to a prolonged inspiratory time. (Adapted from Reference 61, with permission.)