Abstract
Rationale. Elevated intra-abdominal pressure (IAP) may compromise respiratory and cardiovascular function by abdomino-thoracic pressure transmission. We aimed (1) to study the effects of elevated IAP on pleural pressure, (2) to understand the implications for lung and chest wall compliances and (3) to determine whether volumetric filling parameters may be more accurate than classical pressure-based filling pressures for preload assessment in the setting of elevated IAP. Methods. In eleven pigs, IAP was increased stepwise from 6 to 30 mmHg. Hemodynamic, esophageal, and pulmonary pressures were recorded. Results. 17% (end-expiratory) to 62% (end-inspiratory) of elevated IAP was transmitted to the thoracic compartment. Respiratory system compliance decreased significantly with elevated IAP and chest wall compliance decreased. Central venous and pulmonary wedge pressure increased with increasing IAP and correlated inversely (r = −0.31) with stroke index (SI). Global end-diastolic volume index was unaffected by IAP and correlated best with SI (r = 0.52). Conclusions. Increased IAP is transferred to the thoracic compartment and results in a decreased respiratory system compliance due to decreased chest wall compliance. Volumetric filling parameters and transmural filling pressures are clearly superior to classical cardiac filling pressures in the assessment of cardiac preload during elevated IAP.
Highlights
Elevated intra-abdominal pressure (IAP) is commonly encountered in critically ill patients as a result of abdominal diseases or conditions associated with bowel distention, ascites, peritonitis, hemoperitoneum, or trauma [1]
Volumetric filling parameters and transmural filling pressures are clearly superior to classical cardiac filling pressures in the assessment of cardiac preload during elevated IAP
Since central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) typically increase with rising IAP in combination with decreasing stroke volume, determination of filling status based on CVP and PAOP is difficult in intra-abdominal hypertension (IAH) [9,10,11]
Summary
Elevated intra-abdominal pressure (IAP) is commonly encountered in critically ill patients as a result of abdominal diseases or conditions associated with bowel distention, ascites, peritonitis, hemoperitoneum, or trauma [1]. In order to differentiate between the contribution of lung and chest wall in decreased respiratory system compliance, pleural pressure must be measured. The first aim of the present study was to analyze the effects of elevated IAP on pleural pressures at different stages of the respiratory cycle and the implications for measurements of lung or chest wall compliance and abdomino-thoracic pressure transmission. Cardiovascular consequences of IAH include a reduction in cardiac output and stroke volume, resulting from both a decreased venous return and an increase in systemic vascular resistance [4, 8]. Since central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) typically increase with rising IAP in combination with decreasing stroke volume, determination of filling status based on CVP and PAOP is difficult in IAH [9,10,11]. This study was conducted in a porcine model of elevated IAP
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