A novel technique of intra-abdominal pressure measurement:validation of two prototypes

Intra-abdominal pressure (IAP) is an important parameter and prognostic indicator of the patient's underlying physiologic status [1]. Correct IAP measurement therefore is crucial. The gold standard measurement method via a bladder catheter first described by Kron poses the risk for infection and needle-stick injury and interferes with urinary output estimations [1]. Cheatham and Safcsak reported a revision of Kron's technique limiting these risks but still interfering with urinary output estimation [2]. All these measurements also interfere with nursing time and cannot be done without manipulation of the Foley catheter. A technique for measuring IAP using the patient's own urine as transmitting medium has been described previously [1]. The aim of this study is to validate IAP measurement via two prototypes (Holtech Medical, Kopenhagen, Denmark) using this technique. A 50 ml container fitted with a bio-filter for venting is inserted between the Foley catheter and the drainage bag. The container fills with urine during drainage; when the container is elevated, the 50 ml urine flows back into the patient's bladder, and IAP can be read from the position of the meniscus in the clear manometer tube between the container and the Foley catheter. The first prototype consisted of a 50 ml plastic bag with a bio-filter, inserted between the Foley catheter and the urine collection bag; a major drawback was occasional blocking of the bio-filter, leading to overestimation of IAP in some cases. Another drawback was the occasional presence of air-bubbles in the manometer tube, producing multiple menisci leading to misinterpretation of IAP. In addition, the volume of urine flowing back into the bladder was not well defined. Prototype 2 was adapted to correct for the drawbacks of prototype 1, using a rigid 50 ml reservoir with a large bio-filter surface.