Experimental intra-abdominal pressure symmetrically influences bladder pressure and airway plateau pressure
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Introduction: Bladder pressure is routinely measured in the clinical setting to estimate intra-abdominal pressure (IAP). Elevated IAP also affects standard airway pressure measurements. In a porcine model of controlled intra-abdominal hypertension (IAH), we evaluated the fidelity of the standardized bladder pressure measurement and airway plateau pressure changes over a range of IAPs. Methods: Eight (n=8) deeply anesthetized swine were mechanically ventilated at VT=10 ml/kg, f=15, I:E=1:2 and PEEP=1 and 10 cmH2O. After surgical placement of airway tubing in the peritoneal cavity, different levels of IAP (5, 10, 15, 20 and 25 mmHg) were applied via a CPAP system. Bladder pressure and airway pressure were each measured after 10 minutes of stabilization at each level of IAP and during PEEP= 1 and 10 cmH2O. Results: Bladder pressure changed in parallel with IAP. When IAP is >10 mmHg, a mean underestimation of 3.25±0.83 mmHg was observed. Airway plateau pressure also increased with IAP. Bladder pressure was not affected by PEEP (1 and 10 mmHg) or the ventilatory cycle in this air-based model. Conclusion: Our model confirms the reported role of bladder pressure measurement in identifying IAH. Minimal underestimation is noted (3-4 mmHg after IAP>10 mmHg); probably due to incomplete pressure transmission. During mechanical ventilation, airway plateau pressure is directly influenced by IAP as estimated by bladder pressure.