Normal Intraabdominal Pressure in Healthy Adults

Background

Intraabdominal pressure (IAP) has been considered responsible for adverse effects in trauma and other abdominal catastrophes as well as in formation and recurrence of hernias. To date, little information is available concerning IAP in normal persons. Our purpose in this study was to measure the normal range of IAP in healthy, nonobese adults and correlate these measurements with sex and body mass index (BMI).

Methods

After Institutional Review Board approval, 20 healthy young adults (≤30 years old) with no prior history of abdominal surgery were enrolled. Pressure readings were obtained through a transurethral bladder (Foley) catheter. Each subject performed 13 different tasks including standing, sitting, bending at the waist, bending at the knees, performing abdominal crunches, jumping, climbing stairs, bench-pressing 25 pounds, arm curling 10 pounds, and performing a Valsalva and coughing while sitting and also while standing. Data were analyzed by Student’s t-test and Pearson’s correlation coefficients

Results

Intraabdominal pressure was measured in 10 male and 10 female subjects. The mean age of the study group was 22.7 years (range, 18–30 years), and BMI averaged 24.6 kg/m² (range, 18.4–31.9 kg/m²). Mean IAP for sitting and standing were 16.7 and 20 mm Hg. Coughing and jumping generated the highest IAP (107.6 and 171 mm Hg, respectively). Lifting 10-pound weights and bending at the knees did not generate excessive levels of pressure with the maximum average of 25.5 mm Hg. The mean pressures were not different when comparing males and females during each maneuver. There was a significant correlation between higher BMI and increased IAP in 5 of 13 exercises.

Conclusion

Normal IAP correlates with BMI but does not vary based on sex. The highest intraabdominal pressures in healthy patients are generated during coughing and jumping. Based on our observations, patients with higher BMI and chronic cough appear to generate significant elevation in IAP. Thus, this group of patients may potentially be at increased risk for abdominal wall hernia formation following surgery.

Introduction

The importance of elevated intraabdominal pressure (IAP) has been recognized in the trauma and critical care literature for its potential detrimental effects [1, 2]. Elevations in IAP can have several adverse effects such as decreased cardiac output due to reduced venous return, reduced splanchnic and hepatic perfusion, and decreased renal blood flow and glomerular filtration rate [3]. With improvements in the management of the multiorgan dysfunction patient and a better understanding of volume resuscitation and the effects of ischemia-reperfusion injury, the calculation of IAP has become an important adjunct in the care of the critically injured patient.

Recently, the role of IAP as it pertains to hernia repair has been investigated. Junge and colleagues have attempted to study the elasticity and tensile strength of the abdominal wall [4]. Calculations based on Pascal’s principle of hydrostatics have predicted the maximum tensile strength of the abdominal wall to be 16 N/cm [5]. Polypropylene mesh has been shown to have a bursting strength that is more than 10 times this calculated force. Based on their mathematical models and stereotaxy of human abdominal walls, it is hypothesized that the currently available prosthetics may in fact be overengineered, or more dense and less compliant than needed for an optimal hernia repair [5]. However, the abdominal wall pressures are calculated and not a direct measure.

Due to the invasiveness of direct IAP measurement, the measurement of urinary bladder pressure via a bladder catheter has been used as an indirect method of determining IAP [6, 7]. The majority of intensive care patients have a bladder catheter in place, making bladder pressure measurement a readily accessible option for patients at risk for abdominal compartment syndrome. To date, little information is available regarding IAP measurements in noncritically ill patients. Fusco and colleagues evaluated bladder pressure during laparoscopy and showed a close approximation between IAP and bladder pressure [8]. In an attempt to determine a normal range for IAP, Sanchez and coworkers measured IAP in hospitalized patients with bladder catheters in place. They found a mean value of 6.2 mm Hg and a significant relationship between body mass index (BMI), recent abdominal surgery, and IAP [9]. Investigators are currently using indirect pressure measurements for clinical applications. Shafik et al. recorded IAP with an anal manometric catheter during straining and evaluated the effects of increased abdominal pressure on the function of the perineal musculature [10].

The IAP generated during typical daily activities cannot be adequately evaluated in critically ill patients on mechanical ventilation or in patients hospitalized after recent surgery; therefore, a study in healthy subjects was undertaken. The goal of this study was to evaluate multiple healthy subjects to determine a normal range of IAP during typical activities of daily living. This would provide information to establish a baseline force that abdominal closure and hernia repair techniques, including prosthetic biomaterials, must withstand to be considered adequate. We anticipated that there would be a wide range of forces depending on the type of activity performed. The information generated may allow for subsequent comparison studies using variables such as gender or body mass index (BMI).