Ineffective triggering

Flow and pressure waveforms, respectively, illustrating two simulated types of ineffective triggering. The first two waveforms (panel A) represent a patient without problems in respiratory mechanics, with a weak spontaneous effort (Pmus) because of respiratory muscle weakness or decreased neural drive. The bottom two waveforms (panel B) represent a patient with airflow obstruction and difficulty in triggering some breaths because of the presence of auto-positive end-expiratory pressure, even with a muscle effort that is "physiological" but unable to trigger ventilator breaths. In both cases, pressure-controlled ventilation (pressure sensitivity of –2 cm H₂O) was used. The dots on the waveforms indicate ineffective efforts.