Static versus dynamic respiratory mechanics for setting the ventilator

Abstract

The lower inflection point (LIP) of the inspiratory limb of a static pressure-volume (PV) loop is assumed to indicate the pressure at which most lung units are recruited. The LIP is determined by a static manoeuvre with a PV-history that is different from the PV-history of the actual ventilation. In nine surfactant-deficient piglets, information to allow setting PEEP and VT was obtained, both from the PV-curve and also during ongoing ventilation from the dynamic compliance relationship. According to LIP, PEEP was set at 20 (95% confidence interval 17-22) cm H2O. Volume-dependent dynamic compliance suggested a PEEP reduction (to 15 (13-18) cm H2O). Pulmonary gas exchange remained satisfactory and this change resulted in reduced mechanical stress on the respiratory system, indirectly indicated by volume-dependent compliance being consistently great during the entire inspiration.

Endoscopic Imaging to Assess Alveolar Mechanics During Quasi-static and Dynamic Ventilatory Conditions in Rats With Noninjured and Injured Lungs*

“…Differences in global lung mechanics during static or quasi-static and dynamic ventilatory conditions have long been known (27). It has recently been shown that lung mechanics assessed during continuous ventilationarehelpfulinadjustingindividual ventilatory settings (2,4,(42)(43)(44)(45). As assessment of dynamic lung mechanics does not require invasive interventions and allows continuous assessment of ventilatory settings, they may be of clinical interest.…”

“…T he pressure/volume relationship of the respiratory system is commonly used to adjust ventilatory variables (e.g., positive end-expiratory pressure [PEEP]) during mechanical ventilation (1)(2)(3). Specifically, the static pressure/ volume loop has been used to select ventilatory settings that counteract collapse and overdistension of alveoli.…”

“…Consequently, analysis of the "dynamic" pressure/volume loops during uninterrupted ventilation has been the focus of recent investigations. It was shown that measurements of the same variable (e.g., respiratory system compliance) may significantly differ when determined during static or quasi-static and dynamic conditions (2,4). Whereas variables such as the respiratory system compliance are global measures of combined lung and thoracic mechanics, examination of alveolar mechanics provides information on regional respiratory system mechanics.…”

An individualized recruitment maneuver for mechanically ventilated patients after cardiac surgery

“…Traditionally, static pulmonary mechanics has been used to assess lung mechanics [5]. However, recent studies have indicated that the application of dynamic respiratory mechanics in ventilated patients is more appropriate than the use of static lung mechanics [9][10][11]. Therefore, we have proposed the concept of an individualized RM that was defi ned on the basis of dynamic compliance (Cdyn), which is easily obtained from the ventilator as a bedside diagnostic tool [9][10][11].…”

“…However, recent studies have indicated that the application of dynamic respiratory mechanics in ventilated patients is more appropriate than the use of static lung mechanics [9][10][11]. Therefore, we have proposed the concept of an individualized RM that was defi ned on the basis of dynamic compliance (Cdyn), which is easily obtained from the ventilator as a bedside diagnostic tool [9][10][11].The purpose of the present study was to assess the safety and effi cacy of our individualized RM in patients after cardiac surgery. The primary endpoint of our study was to verify the hemodynamic effects induced by the individualized RM and to evaluate the improvement in oxygenation and Cdyn.…”