Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions

Abstract

By measuring airway pressure at the trachea the effect of endotracheal tube resistance during inspiration is excluded while it is included during expiration, yielding correct end-points of inspiration and expiration. This makes it possible to calculate accurately total compliance of the respiratory system during dynamic conditions. By monitoring of airway pressure in the trachea, respiratory mechanics can be assessed more accurately and ventilatory settings adjusted to attenuate ventilator induced lung injury.

Measurement of Alveolar Recruitment at the Bedside: The Beginning of a New Era in Respiratory Monitoring?

“…Measurement of intratracheal pressure may be associated with errors in pressuremeasurement(end-holevsside-holecatheters,intraluminal diameter, catheter obstruction by tracheal secretions). 16 Presence of an intratracheal catheter increases endotracheal tube resistance, interferes with tracheal suctioning, and may be the source of tracheal injury. The accuracy of nitrogen wash-out/wash-in decreases with FIO 2 Ͼ 70% and is very sensitive to microleaks in ventilatory circuits and heterogeneity of regional gas distribution, frequently observed in ARDS.…”

“…The accuracy of nitrogen wash-out/wash-in decreases with FIO 2 Ͼ 70% and is very sensitive to microleaks in ventilatory circuits and heterogeneity of regional gas distribution, frequently observed in ARDS. 16 Until now, the technique has not been evaluated against the computed tomography reference method or compared to the quasi-static PV curves method.…”

“…2 The PEEP Inview module of the Engström Carestation is an indirect application of the reference method proposed by Ranieri et al 5 Two original modifications have been introduced to allow measurement of alveolar recruitment in dynamic conditions of mechanical ventilation: static PV curves using constant flow are replaced by dynostatic PV curves obtained during tidal inflation. 16 The PEEP releasing maneuver is replaced by the measurement of endexpiratory lung volume using the nitrogen wash-out/ wash-in technique. 17,18 The ventilator is equipped with a sensor specifically designed for measuring intratracheal pressure.…”

A minimal model of lung mechanics and model-based markers for optimizing ventilator treatment in ARDS patients

“…However, it should be possible to predict the effect of different tidal volumes, since the EEV is only correlated to PEEP, as long as the flow rates do not change drastically. This impact of flow rates is distinct due to the use of easily available proximal data [35,36], and the airway resistance changes when flow rates change drastically. This limitation also implies that when the ventilator setting is changed drastically, the model needs to be refit and re-identified using 2 or more PV loops at these new ventilation setting.…”

“…For example, if the model was used to identify the parameters for ventilator data, then the model can predict the ventilator data at different settings. Similarly, if carina measurements like those of Karason et al [35] are used, then the model can be used to predict the PV curve at the carina for different settings. Thus, the model can be very generally applied to any data set or type that may be available.…”