An Increase of Abdominal Pressure Increases Pulmonary Edema in Oleic Acid–induced Lung Injury

Abstract

Increased abdominal pressure is common in intensive care unit patients. To investigate its impact on respiration and hemodynamics we applied intraabdominal pressure (aIAP) of 0 and 20 cm H 2 O (pneumoperitoneum) in seven pigs. The whole-lung computed tomography scan and a complete set of respiratory and hemodynamics variables were recorded both in healthy lung and after oleic acid (OA) injury. In healthy lung, aIAP 20 cm H 2 O significantly lowered the gas content, leaving the tissue content unchanged. In OAinjured lung at aIAP 0 cm H 2 O, the gas content significantly decreased compared with healthy lung. The excess tissue mass (edema) amounted to 30 Ϯ 24% of the original tissue weight (455 Ϯ 80 g). The edema was primarily distributed in the base regions and was not gravity dependent. Heart volume, central venous, pulmonary artery, wedge, and systemic arterial pressures significantly increased. At aIAP 20 cm H 2 O in OA-injured lung, the central venous and pulmonary artery pressures further increased. The gas content further decreased, and the excess tissue mass rose up to 103 Ϯ 37% (tissue weight 905 Ϯ 134 g), with homogeneous distribution along the cephalocaudal and sternovertebral axis. We conclude that in OAinjured lung, the increase of IAP increases the amount of edema.Keywords: intraabdominal pressure; acute respiratory distress syndrome; pulmonary edema; lung mechanics; computed tomography scanThe importance of intraabdominal pressure (IAP) in acute lung injury and acute respiratory distress syndrome has been recently suggested (1). For a long time any change in respiratory mechanics in patients with acute lung injury/acute respiratory distress syndrome was attributed to lung mechanics, whereas chest wall mechanics was assumed to be normal. However, few studies in which chest wall elastance was actually measured have showed that it was abnormal in a substantial proportion of patients with acute lung injury/acute respiratory distress syndrome (2-4). We (5) and others (6) have described different chest wall mechanics in patients with pulmonary and extrapulmonary acute respiratory distress syndrome, mainly due to different IAP values.However, apart from respiratory mechanics, the increased intrathoracic pressure caused by chest wall impairment may have important consequences on hemodynamics (7). We investigated the effect of changing IAP during controlled mechanical ventilation in healthy and diseased lungs. Surprisingly, the increase of IAP had an unexpected impact on lung edema, likely related to its formation and clearance. We wish to report our findings and METHODS(Additional details about Methods are provided in an online supplement.)The study group consisted of seven anesthetized and paralyzed domestic pigs (41 Ϯ 4 kg) ventilated throughout the experiment in supine position, with a Vt of 12 ml/kg, respiratory rate of 12-14 breaths/minute, positive end-expiratory pressure of 5 cm H 2 O, and Fi O 2 of 1.0. The animals were fully instrumented for hemodynamic monitoring (carotid artery, right atrium, mea...

Myelofibrosis‐associated massive splenomegaly: A cause of increased intra‐abdominal pressure, pulmonary hypertension, and positional dyspnea

“…In a similar pattern, pulmonary hemodynamics were affected in otherwise healthy lungs when IAP was high [21]. This effect was reversible, and normal pulmonary function was restored in patients with increased IAP when abdominal decompression was performed [22].…”

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

“…revealed in healthy animals [9]. Increased IAP markedly affects the mechanical properties of the respiratory system, lung and chest wall, and the respiratory function in different experimental settings.…”

“…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].…”

“…Elevated IAP is one of the reasons for respiratory failure [8,9]. IAP is transmitted to the thoracic cavity directly or indirectly thought deviation of the diaphragm.…”

The Abdominal Compartment Syndrome

“…Recently, IAH has been related to ventriculoperitoneal shunt dysfunction [19]. For the lungs [24][25][26]: As a rule of thumb, the best PEEP may be set to counteract IAP whilst at the same time avoiding overinflation of already well-aerated lung regions. The best PEEP (cm H 2 O) = IAP (mm Hg) to a maximum value of 20.…”