IngentaConnect Validation of a new respiratory inductive plethysmograph

Abstract:

Background:

The respiratory inductive plethysmograph (RIP) can be used to monitor changes in end-expiratory lung volume (ΔEELV), and thus, used in intensive care when evaluating positive end-expiratory pressure (PEEP)-induced changes in lung volumes in order to optimise the ventilator settings. We validated the newest model of RIP (Respitrace Plus^TM), both under laboratory and clinical conditions, and made a comparison with a previously validated RIP (Respigraph^TM) in the measurement of tidal volume (V_T), long-term EELV and PEEP-induced acute ΔEELV. Methods:

The in vitro validation was performed using a lung model and the in vivo evaluation in five spontaneously breathing normal subjects, four patients with acute lung injury (ALI) and eight anaesthetised patients. Results:

The difference in V_T values during PEEP manipulations between pneumotachometer (PNT) and RIP in spontaneously breathing volunteers and mechanically ventilated ALI patients was 0.1±0.9% (mean±SEM) and −5.2±0.6, respectively (effect of device NS). In anaesthetised patients, the difference between the new RIP and spirometer in the measurement of PEEP-induced acute ΔEELV was −2.6±1.5% (PEEP-device interaction, P<0.05). In ALI patients, the difference between PNT and RIP in the measurement of PEEP-induced acute ΔEELV was 1.0±9.7% (NS). The new RIP had a baseline drift over 50-fold when cold and over 10-fold when warm compared to the old RIP in vitro. Conclusion:

The new RIP is accurate enough for clinical and research purposes in the measurement of V_T. Semiquantitative measurements of acute ΔEELV can be done with accuracy sufficient for clinical use, but long-term ΔEELV monitoring is not possible. The new RIP should be kept on for several hours before measurements to minimise the drift.

Keywords: Breathing pattern; end-expiratory lung volume (EELV); respiratory inductive plethysmography (RIP); tidal volume (VT)

Document Type: Research article

Affiliations: 1: Department of Anaesthesia, Turku University Central Hospital, Turku, Finland 2: Critical Care Research Program, Division of Intensive Care, Department of Anesthesiology and Intensive Care, Kuopio University Hospital, Kuopio, Finland 3: Department of Intensive Care, University Hospital Bern, Bern, Switzerland