Spine-Intra-Abdominal Pressure (SIAP) study

The SIAP study investigates the effect of using Ergotrics' Inflatable Prone Support (IPS) on intra-abdominal pressure (IAP) during spine surgery.

The objective of this study is to demonstrate the ability of the inflatable Prone Supports (IPS) to lower the IAP of patients in the prone position.


Study background

The objective of this study is to demonstrate the ability of the inflatable Prone Supports (IPS) to lower the IAP of patients in the prone position. Whenever the patients’ position is changed to prone, the IAP is increased due to abdominal compression.1,2 It has been demonstrated previously that an increased IAP is linked to increased bleeding. The ability to reduce IAP will be assessed by measuring IAP before and after inflation of the IPS. The METC (Medical Ethics Review Committee) has approved the SIAP study submitted by Dr. Van Eijs (anesthesiologist at ETZ, Tilburg, The Netherlands). The study will enroll 40 patients, aged between 18-70 and a body weight < 120 kg.

What is IAP?

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. Under physiological conditions, values of up to 5 mmHg are considered normal in adults.3 The incidence of complications arising from increased IAP in critically ill patients, is high and its impact is significant. IAP impacts the cerebrospinal venous system and the jugular venous system via two pathways (see fig. 1).
Fig 1. The concept of the two pathways. In the first pathway, an increase in IAP can cause backflow through the sacral venous plexus and the vertebral venous into the spinal canal. This can cause congestion of venous blood in the spinal canal and can cause flow of venous blood into the brain. In the second pathway, an increase in IAP can cause an increase in ITP (intrathoracic pressure) which in turn results in a back pressure on the jugular veins and decreases the drainage of the CSF (Cerebrospinal fluid) and the venous blood.4

How is IAP measured?

The enrolled patients undergo spine surgery in prone position and have a transurethral bladder catheter during the procedure. The urinary catheter will be used to measure the IAP. The urinary bladder pressures reflects well the pressures in the abdominal cavity.3,7,8

How do the IPS supports for prone surgery reduce the IAP?

The IPS cushion is designed as a mirror image of the human skeleton. In this way it supports the ribcage and pelvis, while leaving the abdomen free. Patients are positioned in a manner to offload the abdomen as much as possible to avoid an increased IAP.

About Ergotrics

Ergotrics is a Med-Tech company which specializes in the use of compressed air in healthcare. We develop and manufacture products which allow for optimal positioning or moving of patients. Without heavy physical labour and with special attention given to ease of use, patient safety and hygiene.

Need more info?


1. Malhotra et al; Quantifying the Amount of Bleeding and Associated Changes in Intra- Abdominal Pressure and Mean Airway Pressure in Patients Undergoing Lumbar Fixation Surgeries: A Comparison of Three Positioning Systems; Asian Spine J 2016;10(2):199-204.
2. Han et al; The Effect of Body Mass Index on Intra-Abdominal Pressure and Blood Loss in Lumbar Spine Surgery; J Korean Neurosurg Soc 51 : 81-85, 2012.
3. Kirkpatrick et al; Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome; Intensive Care Med (2013) 39:1190–1206.
4. Depauw et al; The significance of intra-abdominal pressure in neurosurgery and neurological diseases: a narrative review and a conceptual proposal; Acta Neurochir (Wien). 2019 May;161(5):855-864.
5. Park; The Effect of Patient Positioning on Intraabdominal Pressure and Blood Loss in Spinal Surgery; Anesth Analg. 2000 Sep;91(3):552-7.
6. Koprulu et al: Ventilation Mode and Epidural Bleeding in Microdiscectomy: Comparison of Two Ventilation Techniques; Turk Neurosurg 26(5): 777-782, 2016.
7. Al-Abassi et al; Is intra-bladder pressure measurement a reliable indicator for raised intra-abdominal pressure? A prospective comparative study. BMC Anesthesiol. 2018 Jun 19;18(1):69.
8. Bodnar. Continuous Intra-Abdominal Pressure Measurement: Re-Discovered. Biomed J Sci&Tech Res 9(3)-2018.

Want to stay informed? Sign up to keep you updated.

Follow us on social media: