Accuracy of P0.1 measurements performed by ICU ventilators: a bench study

Abstract

Background Occlusion pressure at 100 ms (P0.1), defined as the negative pressure measured 100 ms after the initiation of an inspiratory effort performed against a closed respiratory circuit, has been shown to be well correlated with central respiratory drive and respiratory effort. Automated P0.1 measurement is available on modern ventilators. However, the reliability of this measurement has never been studied. This bench study aimed at assessing the accuracy of P0.1 measurements automatically performed by different ICU ventilators. Methods Five ventilators set in pressure support mode were tested using a two-chamber test lung model simulating spontaneous breathing. P0.1 automatically displayed on the ventilator screen (P0.1vent) was recorded at three levels of simulated inspiratory effort corresponding to P0.1 of 2.5, 5 and 10 cm H2O measured directly at the test lung and considered as the reference values of P0.1 (P0.1ref). The pressure drop after 100 ms was measured offline on the airway pressure–time curves recorded during the automated P0.1 measurements (P0.1aw). P0.1vent was compared to P0.1ref and to P0.1aw. To assess the potential impact of the circuit length, P0.1 were also measured with circuits of different lengths (P0.1circuit). Results Variations of P0.1vent correlated well with variations of P0.1ref. Overall, P0.1vent underestimated P0.1ref except for the Löwenstein® ventilator at P0.1ref 2.5 cm H2O and for the Getinge group® ventilator at P0.1ref 10 cm H2O. The agreement between P0.1vent and P0.1ref assessed with the Bland–Altman method gave a mean bias of − 1.3 cm H2O (limits of agreement: 1 and − 3.7 cm H2O). Analysis of airway pressure–time and flow–time curves showed that all the tested ventilators except the Getinge group® ventilator performed an occlusion of at least 100 ms to measure P0.1. The agreement between P0.1vent and P0.1aw assessed with the Bland–Altman method gave a mean bias of 0.5 cm H2O (limits of agreement: 2.4 and − 1.4 cm H2O). The circuit’s length impacted P0.1 measurements’ values. A longer circuit was associated with lower P0.1circuit values. Conclusion P0.1vent relative changes are well correlated to P0.1ref changes in all the tested ventilators. Accuracy of absolute values of P0.1vent varies according to the ventilator model. Overall, P0.1vent underestimates P0.1ref. The length of the circuit may partially explain P0.1vent underestimation.

High Respiratory Drive and Excessive Respiratory Efforts Predict Relapse of Respiratory Failure in Critically Ill Patients with COVID-19

“…Automated measurements were performed with four commercialized ventilators: Evita XL (Dräger), Evita Infinity V500 (Dräger), Avea (CareFusion), and Carescape R860 (GE Healthcare). The accuracy and precision of values of P 0.1 displayed by these ventilators have been validated ( 8 , 9 ). The same ventilator was used for a given patient.…”

Reliability and limits of transport-ventilators to safely ventilate severe patients in special surge situations

“…The respiratory rate was set at 25 breaths/min. The ventilatory settings were chosen to achieve a moderate effort, with a decrease in airway pressure 100 ms after occlusion (P 0.1 ) of 4 cmH 2 O (consistent with P 0.1 value recently described in COVID patients [ 12 ] measured at the airway opening of the lung model [ 13 , 14 ]. A level of PEEP was applied to the driving lung to obtain a perfect contact of the lung-coupling clip between the two chambers at the end of expiration.…”

Flow Index accurately identifies breaths with low or high inspiratory effort during pressure support ventilation

“…Other proposed measures, such as the airway occlusion pressure ( P 0.1 ) and the swing in airway pressure generated by respiratory muscle effort recorded during a brief airway opening occlusion at end-expiration (Δ P occ ) are both affected by technical or conceptual limitations [ 9 , 10 ]. In particular, P 0.1 measured by mechanical ventilators has a measurement error of ± 2 cmH 2 O [ 10 , 11 ]. Since the threshold for identifying excessive inspiratory effort is 3.5–4 cmH 2 O and 1 cmH 2 O for low inspiratory effort, this approximation is far from negligible.…”