Evaluation of a new module in the continuous monitoring of respiratory mechanics

Objective: Bedside monitoring of respiratory mechanics facilitates the use of lung protective ventilation in acute lung injury (ALI). We evaluated a new clinical monitor of respiratory mechanics. Design: Prospective, in vitro and in vivo study. Setting: University hospital. Patients: Measurements were done using a lung model and in patients after cardiac surgery (n = 10) and in patients with ALI (n = 10). Interventions and measurements: The monitor provides continuous monitoring of pressure, flow and volume waveform and loop data, and automatically collected variables of respiratory mechanics. Breath-by-breath respiratory mechanics data and the automated variables obtained with the new monitor were compared with Row and pressure reference data. Results: Waveform data comparison showed errors of less than 5 % for most variables. Automatically recorded respiratory pressures and volumes showed good agreement within clinical standards when compared to reference (errors from 2.5 % to 6.2 %). Automatically recorded derived variables present poor agreement (errors from 8.1 % to 158.3 %). Conclusions: The waveform data of the new monitor is accurate. The value of the automatically derived variables is limited by the fact that inspiratory plateau pressure and plateau compliance have no direct physiological meaning. Nevertheless, in clinical monitoring much information can be derived from the waveform signals alone and from pressure-volume and flow-volume loops. These facilitate monitoring changes in respiratory mechanics in the ALI patient.