Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo

Abstract

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.

Força muscular e mortalidade na lista de espera de transplante de fígado

“…About 50 to 60% of patients suffering from hepatic cirrhosis develop ascites due to renal difficulties in manipulating sodium and water, and this generates a prognosis reserved for patients which leads to a survival of 50% in two years 1 . The protein-caloric malnutrition has been described as an existing condition among all patients with hepatic cirrhosis since the liver plays an essential role in metabolism.…”

“…The protein-caloric malnutrition has been described as an existing condition among all patients with hepatic cirrhosis since the liver plays an essential role in metabolism. Another important disturbance is the loss of muscle and bone mass and all of these factors can negatively influence both morbidity and mortality [1][2][3][4] . Patients with hepatic cirrhosis from different etiologies demonstrate malnourishment and vulnerability to infections, which consequently weakens their musclular and respiratory functions.…”

“…They may also show ascites and pleural effusions, due to low levels of albumin and poor protein intake. Because of alimentary restrictions and hepatic metabolism inefficiencies, muscle mass may also be impaired 1 . Respiratory muscular strength can be decreased; nevertheless, it doesn't interfere with removal of mechanical ventilation, despite chirurgic interferences, pain and surgical incisions 5 .…”

“…The high levels of intra-abdominal pressure affect adjacent organ and tissue function, which leads to increases in the intra-thoracic pressure that compresses the lungs, and impair the ventilation/perfusion 6 relationship. Some authors observed that the bulky and tense ascites alter the respiratory mechanics and decrease chest complacency 1 . The major disturbance occurs in the pulmonary volumes and for the functional residual capacity, which improves after paracentesis, however, without significant improvements in oxygenation 7 .…”

Evaluation of the Effects of Elevated Intra-abdominal Pressure on the Respiratory Mechanics in Mechanically Ventilated Patients

“…There are many studies examining the interaction between abdominal and thoracic compartment in humans and animals, in healthy and diseased lung [9,16,[19][20][21].…”