The pressure at the lower inflexion point has no relation to airway collapse in surfactant‐treated premature lambs

Abstract

In surfactant-treated premature lambs the pressures at LIP and UIPexp are not related, showing that LIP does not indicate the pressure at which airways collapse.

Pressure‐volume relationships in acute lung injury: methodological and clinical implications

“…2, see methods). The estimated LIP do not represent therefore the same physiological phenomenon (15)(16)(17)(18). Our aim was to assess the numerical differences between these measurements and consider their eventual impact in the clinical practice.…”

“…A wide variety of inflation and deflation PV curves constructed both with PEEP and volume manipulations have been proposed, but no standard methods have been established so far. Many of the available methods translate different physiological phenomena and, as such, convey different information (15)(16)(17)(18). The possible impact of these methodological differences on a protective approach to mechanical ventilation has never been systematically analyzed.…”

Lung recruitment during mechanical positive pressure ventilation in the PICU: what can be learned from the literature?

“…The upper inflection point on the pressurevolume loop is related to alveolar over-distention, usually at pressures well over 30-50 cm H 2 O [22,23]. The lower inflection point (LIP) is not related to alveolar opening or optimal recruitment or 'optimal PEEP' as it is merely a result of external factors such as chest wall compliance and intra-abdominal pressure, and the recruitment state as a result of volume history [22,[24][25][26][27][28]. Besides direct microscopy, studies analysing PV-loops show that alveolar recruitment occurs above LIP until the UIP [17,29].…”

Does a solitary lobar collapse give pressure–lung volume relationship similar to that found in acute respiratory distress syndrome? A porcine experimental study

“…Static PV curves measuring airway pressure and oesophageal pressure (as an estimate of pleural pressure) and lung volume change of the whole lung and of the non-affected lung (see below) were obtained by a slow inflation-deflation, interrupted technique, as reported previously (Ingimarsson et al, 2001;Hansen et al, 2006;Koefoed-Nielsen et al, 2008). In short, the lungs were slowly (40 ml )1 s) inflated via an interrupter from 0 to 40 cmH 2 O airway pressure.…”

“…Maximal hysteresis was defined as the maximal vertical distance between the limbs of the curve (Fig. 2) (Ingimarsson et al, 2001;Bitzen et al, 2006;Koefoed-Nielsen et al, 2008).…”