Local Differences in Intrathoracic Pressure and Their Relation to Cardiac Filling Pressure in the Dog

Age‐related differences in the distortion of the sheep lung in response to localised pleural stress

“…As discussed below, this finding is consistent with previous observations that the lungs provide a greater limitation to the filling of the heart in the fetus and neonate than they do in the adult (Kingma et al 1987;Grant et al 1994;Grant, 1999). Our study also revealed that in the adult the surface of the lung that comprises the cardiac fossa is significantly less distortable than the lateral surface of the same lung, a result that is in keeping with the observation that the pleural pressure within the cardiac fossa exceeds that at the lateral surface of the lung (Brookhart & Boyd, 1947). Finally, our study confirms a previous report that increases in P aw substantially decrease the distortability of the adult lung (Robertson et al 1973).…”

“…Although both a decrease in chest-wall compliance (Agostoni, 1959) and an alteration in the properties of the pericardium (Naimark, 1995;Naimark et al 1998) are likely to contribute to the changes in ventricular constraint that accompany development, our current findings suggest for the first time that developmental alterations in the properties of the lungs themselves are also important. Brookhart & Boyd (1947) recognised that, while filling, the heart displaces the lung and, as a result, the intrathoracic pressure within the cardiac fossa exceeds that of the lateral regions. Moreover, the difference between lateral pleural pressure and the pressure recorded from within the cardiac fossa increases as P aw is increased.…”

“…Just as the heart influences lung gas volume, the presence of the lung surrounding the heart also significantly limits ventricular filling and thus limits cardiac output via the Frank-Starling mechanism. Brookhart & Boyd (1947) observed that the interaction between the heart and the lung results in intra-thoracic pressure within the cardiac fossa exceeding that in the lateral pleural space, and that an increase in lung volume is accompanied by an increase in extra-cardiac pressure. It was subsequently recognised that this increase in extra-cardiac pressure is the mechanism whereby the application of positive endexpiratory pressure and increasing lung volume act to constrain ventricular filling and limit cardiac output (Fewell et al 1980a,b;Kingma et al 1987).…”

“…we aimed to determine whether the neonatal lung resists neighbouring structures encroaching into its space to a greater extent than the adult lung. Moreover, as the pressure recorded in the cardiac fossa exceeds that measured on the lateral pleural surface (Brookhart & Boyd, 1947), we sought to determine whether the distortability of the lung surface within the cardiac fossa differs from that of the lateral surface of the lung. Finally, we sought to determine how the distortability of the lung is affected by elevations in airway pressure (P aw ) throughout development as increments in P aw have a negative impact upon cardiac function, especially in early life.…”

Intrinsic PEEP and cardiopulmonary interaction in patients with COPD and acute ventilatory failure

“…On the one hand, an increase in lung volume may impede venous return, both directly through compression of the vena cava [29] and right heart [36], and indirectly through an increase in Pra, which can reduce the pressure gradient for venous return [37]. On the other hand, Pra will decrease consequent to the transmission of the large negative inspiratory swings transmitted to the intrathoracic vascular structures.…”