Monitoring of patient-ventilator interaction at the bedside

Monitoring of patient-ventilator interactions at the bedside involves evaluation of patient breathing pattern on ventilator settings. One goal of mechanical ventilation is to have ventilator-assisted breathing coincide with patient breathing. The objectives of this goal are to have patient breath initiation result in ventilator triggering without undue patient effort, to match assisted-breath delivery with patient inspiratory effort, and to have assisted breathing cease when the patient terminates inspiration, thus avoiding ventilator-assisted inspiration during patient exhalation. Asynchrony can occur throughout the respiratory cycle, and this paper describes common asynchronies. The types of asynchronies discussed are trigger asynchrony (ie, breath initiation that may manifest as ineffective triggering, double-triggering, or auto-triggering); flow asynchrony (ie, breath-delivery asynchrony, which may manifest as assisted-breath delivery being faster or slower than what patient desires); and cycling asynchronies (ie, termination of assisted inspiration does not coincide with patient breath termination, which may manifest as delayed cycling or premature cycling). Various waveforms are displayed and graphically demonstrate asynchronies; basic principles of waveform interpretation are discussed.