A study of intragastric and intravesicular pressure changes during rest, coughing, weight lifting, retching, and vomiting

Background  In patients undergoing a variety of procedures, surgical success is in part dependent on maintaining normal intra-abdominal pressure in the immediate postoperative period. Our objective was to quantify intragastric and intravesicular pressures during activities, through the use of manometry catheters. Methods  Ten healthy volunteers had a manometry catheter placed transnasally, and a urinary Foley catheter placed. Baseline intragastric and intravesicular pressures were recorded and the catheters were then transduced continuously. Pressures were recorded with activity: coughing, lifting weights, retching (dry heaving), and vomiting. Results  All pressure changes were significant from baseline except for weight lifting. The highest intragastric pressure was 290 mmHg, seen during vomiting. Comparison of intragastric and intravesicular pressures showed no significant difference. There was significantly higher intragastric pressure with vomiting and retching as compared with coughing, whereas coughing applied more pressure than weight lifting. Conclusions  This is the first report of intragastric pressures during vomiting and retching (dry heaving). We conclude that vomiting and retching (dry heaving) can render significant forces on any tissue apposition within the stomach or the peritoneal cavity.     

Vaginal pressure during daily activities before and after vaginal repair

The objective of the study was to measure vaginal pressure during various daily activities in patients before and after vaginal surgery for pelvic organ prolapse, searching data for evidence-based activity guidelines. Vaginal pressure (VP) was studied in 23 patients during activities such as rest, pelvic floor contraction (PFC), coughing, Valsalva, rising from sitting to standing and lifting 2 and 5 kg with four different lifting techniques. VP was measured before, 1–5 days and 4–6 weeks after vaginal repair. Mean VP was four to five times higher during coughing and Valsalva compared to PFC and lifting 2 and 5 kg. Lifting in the walking position created a slightly higher VP compared to other lifting techniques, which did not differ. The VP did not increase when lifting 5 kg compared to 2 kg. Mean VP during coughing and Valsalva were significantly lower 1–5 days after the operation. VP was not related to the type of vaginal repair. The results imply that post-operative counselling should concentrate more on treating chronic cough and constipation than restrictions of moderate physical activities.     

The urethral pressure profile under stress: A comparison of profiles on coughing and straining

In terms of urethral pressure measurements the distinction between stress-incontinent and continent women is perhaps best made by examining the urethral response to stress. Profiles may be performed during the repeated intraabdominal pressure rises due to coughing, or the sustained effect of straining; the relationship between the two has not previously been defined. This comparative study involves 120 patients with a variety of urinary symptoms in whom stress profiles were performed both on coughing and on straining. Parameters of the cough profile were found to be more repeatable than those of the strain profile. and also related more closely to the severity of incontinence. Calculation of pressure transmission ratios from cough profiles also proved more useful. since they allow the acute and sustained components of the urethral response to stress to be readily distinguished.     

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 (< or =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/m(2) (range, 18.4-31.9 kg/m(2)). 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.     

A reliable method for monitoring intraabdominal pressure during natural orifice translumenal endoscopic surgery

Background Natural orifice translumenal endoscopic surgery (NOTES) provides surgical access to the peritoneal cavity without skin incisions. The NOTES procedure requires pneumoperitoneum for visualization and manipulation of abdominal organs, similar to laparoscopy. Accurate measurement of the pneumoperitoneum pressure is essential to avoid potentially deleterious effects of intraabdominal compartment syndrome. A reliable method for monitoring pneumoperitoneum pressures during NOTES has not been identified. This study evaluated several methods of monitoring intraabdominal pressures with a standard gastroscope during NOTES. Methods Four female pigs (25 kg) were sedated, and a single-channel gastroscope was passed transgastrically into the peritoneal cavity. Pneumoperitoneum was achieved via a pressure insufflator through a percutaneous, intraperitoneal 14-gauge catheter. Three other pressures were recorded via separate catheters. First, a 14-gauge percutaneous catheter passed intraperitoneally measured true intraabdominal pressure. Second, a 14-gauge tube attached to the endoscope was used to measure endoscope tip pressure. The third pressure transducer was connected directly to the accessory channel of the endoscope. The abdomen was insufflated to a range of pressures (10–30 mmHg), and simultaneous pressures were recorded from all three pressure sensors. Results Pressure correlation curves were developed for all animals across all intraperitoneal pressures (mean error, –4.25 to –1 mmHg). Endoscope tip pressures correlated with biopsy channel pressures (R ² = 0.99). Biopsy channel and endoscope tip pressures fit a least-squares linear model to predict actual intraabdominal pressure (R = 0.99 for both). Both scope tip and biopsy channel port pressures were strongly correlative with true intraabdominal pressures (R ² = 0.98 and R ² = 0.99, respectively). Conclusion This study demonstrates that monitoring pressure through an endoscope is reliable and predictive of true intraabdominal pressure. Gastroscope pressure monitoring is a useful adjunct to NOTES. Future NOTES procedures should incorporate continuous intraabdominal pressure monitoring to avoid the potentially deleterious effects of pneumoperitoneum during NOTES. This can be achieved by the integration of pressure-monitoring capabilities into gastroscopes. Presented at the 2006 Scientific Session of Society of American Gastrointestional and Endoscopic Surgeons (SAGES), April 2006, Dallas, TX, USA     

Effect of straining on the lower esophageal sphincter: identification of the "straining-esophageal reflex" and its role in gastroesophageal competence mechanism.

The lower esophagus is intra-abdominal and exposed to intra-abdominal pressure (IAP) variations that may lead to gastroesophageal reflux (GER). We investigated the hypothesis that the lower esophageal sphincter (LES) undergoes phasic contraction on IAP increase, with a resulting inhibition of the stress GER. The study comprised 17 subjects (age 42.3 +/- 8.7 SD yr, 10 men, 7 women) who were scheduled for surgical repair of abdominal hernia. The patients had no swallowing problems. The electromyographic (EMG) activity of the LES and pressure within the LES were recorded at rest and during increased IAP (coughing, straining). The recording was repeated after LES anesthetization or saline infiltration. The LES EMG at rest showed regular slow waves (SWs), superimposed on or followed by random action potentials (APs). Coughing or straining induced increase of the SWs parameters and also of the APs; although the increase with straining was less than with coughing, the difference was insignificant. Coughing or straining increased the LES pressure significantly (p < .05, p < .05, respectively). Ten minutes after LES anesthetization, coughing or straining did not produce significant LES EMG or pressure changes, while saline infiltration of LES caused LES response similar to preinjection. Thus, coughing and straining effected an increase of the LES EMG activity and pressure, an action presumably mediated through a reflex that we call the "straining-esophageal reflex." This reflex seems to be evoked during increased intra-abdominal pressure and to effect LES contraction, thus, sharing with other factors in prevention of gastroesophageal reflux.     

Effect of Straining on the Lower Esophageal Sphincter: Identification of the “Straining-Esophageal Reflex” and Its Role in Gastroesophageal Competence Mechanism

The lower esophagus is intra-abdominal and exposed to intra-abdominal pressure (IAP) variations that may lead to gastroesophageal reflux (GER). We investigated the hypothesis that the lower esophageal sphincter (LES) undergoes phasic contraction on IAP increase, with a resulting inhibition of the stress GER. The study comprised 17 subjects (age 42.3 ± 8.7 SD yr, 10 men, 7 women) who were scheduled for surgical repair of abdominal hernia. The patients had no swallowing problems. The electromyographic (EMG) activity of the LES and pressure within the LES were recorded at rest and during increased IAP (coughing, straining). The recording was repeated after LES anesthetization or saline infiltration. The LES EMG at rest showed regular slow waves (SWs), superimposed on or followed by random action potentials (APs). Coughing or straining induced increase of the SWs parameters and also of the APs; although the increase with straining was less than with coughing, the difference was insignificant. Coughing or straining increased the LES pressure significantly (p<.05, p<.05, respectively). Ten minutes after LES anesthetization, coughing or straining did not produce significant LES EMG or pressure changes, while saline infiltration of LES caused LES response similar to preinjection. Thus, coughing and straining effected an increase of the LES EMG activity and pressure, an action presumably mediated through a reflex that we call the “straining-esophageal reflex.” This reflex seems to be evoked during increased intra-abdominal pressure and to effect LES contraction, thus, sharing with other factors in prevention of gastroesophageal reflux.     

End Thoracic Duct Pressures in Man1

Thoracic duct end pressures have been measured in a conscious patient undergoing cannula-tion in an attempt to remove serum blocking activity. Pressures were measured during rest, coughing, straining and laughing, and during the last-mentioned activity pressures of the order of 85 mm Hg were recorded. It is suggested that formal ligation of the thoracic duct would be necessary to withstand these pressures following removal of the cannula at the termination of treatment.     

Reconstruction of abdominal wall defects using corium. Surgical procedure, clinical results and manometric examination of postoperative abdominal wall function]

Extensive resection of the abdominal wall was performed on six patients to reconstruct defects caused by tumors or necroses. Autologous dermis covered by a flap plasty produced good clinical and functional results, documented by the measurement of intraabdominal pressures in response to coughing, pressing, and lifting of the legs. The autologous dermis graft represents a valuable tool for the closure of large defects of the abdominal wall.     

Hemodynamic effects of pneumoperitoneum in lithotomy position

AIM OF STUDY: The study investigates the haemodynamic effects of the varying intraabdominal pressures and patient positions during gynecological procedures employing pneumoperitoneum in lithotomy positions. METHODES: TEE was used to determine end-diastolic and end-systolic left ventricular surface areas and ejection fractions were calculated from these data. To evaluate intraabdominal volume shifts the diameter of the internal iliac vein was measured by mean of vaginal ultrasound. RESULTS: In the horizontal lithotomy position both LVEDA and LVESA increased when intraabdominal pressure increased by 10 and 15 mmHg, respectively. LVAEF significantly decreased when intraabdominal pressure increased by 15 mmHg. Also DVII decreased. In Trendelenburg position there was no change in LVEDA, LVESA, LVAEF and DVII. In Anti-Trendelenburg position LVEDA and LVESA decreased. However, LVAEF remained constant and DVII increased. CONCLUSION: The increase of the intraabdominal pressure in the lithotomy position results in an increase in intrathoracic volume and an decrease in LVAEF via elevation of the the lower extremities and compression of the splanchnic vessels. There are no changes in Trendelenburg position. However, in Anti-Trendelenburg position, gravity results in a decrease in intrathoracic blood volume. In the decreased, dilatated heart the increase in intrathoracic volume may increase myocardial wall tension and hence oxygen demand, ultimately leading to an acute heart failure. As a result laparoscopic procedures in horizontal lithotomy position should be avoided in patients with dilatative cardiomyopathy.     

Urethral pressure increase on effort originates from within the urethra,and continence from musculovaginal closure

The aim of the study was to determine the contribution of intra-abdominal pressure transmission to urinary continence in the female. Five patients with genuine stress incontinence (GSI) were studied. Pressure transmission was measured in equivalent positions inside and outside the urethra and bladder during the Intravaginal Slingplasty procedure, a surgical operation used for treatment of urinary incontinence, and performed under local anaesthesia. A 6 mm diameter channel was created alongside the urethra. Two separate microtransducer catheters appropriately marked for length were inserted, one inside the urethra, and the other inside the described channel. With the vaginal hammock intact, an average of 10 simultaneous pressure measurements were made intraoperatively in response to coughing and straining in equivalent positions inside the urethra, and directly outside. Significantly higher pressure readings were found inside the urethra (P = 0.0025), indicating that an active component within the urethra may have created this pressure rise. After opening out two suburethral vaginal flaps, large quantities of urine were lost on coughing in all patients Continence was achieved on tightening the suburethral vagina, indicating that an adequately tight vaginal hammock is a critical element in the continence process. The findings of this study question intraabdominal pressure as a mechanism contributing to continence, but support an alternative mechanism, musculovaginal closure of the urethra. © 1995 Wiley-Liss, Inc.     

On the pathogenesis of rectocele: the concept of the rectovaginal pressure gradient

Coughing or straining evokes reflex bulbocavernosus (BCM) and puborectalis (PRM) muscle contraction, which apparently transforms the vagina into a closed high-pressure cavity [13]. This elevated vaginal pressure counteracts the increased intra-abdominal pressure and the tendency of the uterus to prolapse, and also supports the rectovaginal septum against the high straining-induced intrarectal pressure and possible consequent rectocele (posterior vaginal prolapse) formation. We investigated the hypothesis that a weak BCM and PRM share in the genesis of rectocele by changing the rectovaginal pressure gradient. Twenty-three women with rectocele (mean age 43.2±6.6 years) and 12 healthy women volunteers (mean age 41.6±6.2 years) were studied. The response of the intrarectal (intra-abdominal) and intravaginal pressure, as well as the EMG activity of the BCM and PRM to straining or coughing, was recorded. In the healthy volunteers the rectal and vaginal pressures showed a significant increase on coughing or straining, with no significant difference between the rectal or vaginal pressures. Also, the BCM and PRM EMG activity exhibited a significant increase. Rectocele patients showed a significantly low resting vaginal pressure. The increase in rectal and vaginal pressure, as well as of the EMG activity of the BCM and PRM on straining or coughing, was significantly lower and the latency of the EMG response was significantly longer than those of the healthy volunteers. A difference in the rectovaginal pressure gradient showing a significant increase in the rectal against the vaginal pressure, particularly on coughing or straining, is suggested to be the basic factor in the genesis of rectocele. This pressure difference appears to be caused by diminished BCM and PRM contractile activity. A disrupted rectovaginal septum is not a prerequisite for rectocele formation, as the septum appears normal in obstructed defecation despite the common occurrence of rectocele. A histopathologic study of the septum in rectocele seems necessary.Abbreviations BCM Bulbocavernosus muscle - PRM Puborectalis muscle - EMG Electromyogram Editorial Comment: The investigation demonstrated decreased EMG activity and vaginal pressure in the women with rectoceles, especially during increased intra-abdominal pressure, compared to normal controls. Based on these data, the authors theorize that the decreased vaginal pressure results from poor tone and blunted reflex contraction of the BCM and PRMS during increases in intra-abdominal pressure, which in normal women closes the vaginal hiatus causing an equilibration of increased intra-abdominal pressure on the rectal and vaginal sides of the rectovaginal septum. This is a novel theory for the pathogenesis of rectocele and is supported by these preliminary data. The fact that the subjects had a stool frequency of less than twice weekly is more consistent with defecatory dysfunction secondary to a motility disorder rather than outlet obstruction. This raises the question of whether the rectocele is a result of the defecatory dysfunction rather than causative, and affects the external validity of the study population. Additionally, the theory fails to explain the association of paradox with rectocele. Nevertheless, this theory merits further investigation as one of several potential etiologies of rectocele.     

Intra-abdominal Pressure Monitoring in Open Abdomen Management with Dynamic Abdominal Closure

The importance of elevated intra-abdominal pressure (IAP) and abdominal compartment syndrome (ACS) have been recognized in critical care for its potential damaging effects. But, quantification of IAP values may be useful as a clinical tool for determining efficacy of coughing and straining for functional recovery of OA patients. We would like to evaluate IAP generated in an OA patient and the effect of negative pressure therapy (NPT) and dynamic abdominal closure systems (ABRA) on the IAP values at rest and during coughing and straining and compare those with IAP measurements of closed abdomen after standard open elective colorectal surgery (non-OA). Eight OA and eight non-OA patients were included in this study. OA patient with NPT and ABRA (OA + NA), OA patient without NPT and ABRA completely unbraced (OA-NA) (NA stands for NPT and ABRA), and non-OA patients underwent IAP measurements at rest, during coughing, and during straining via transurethral catheter. There was no difference in the mean of IAP measurement at rest in OA-NA (6.1 mmHg), OA + NA (6.5 mmHg), and non-OA (6.0 mmHg) patients. During coughing, IAP of OA-NA, OA + NA, and non-OA patients were 11.5, 19.1, and 22.0 mmHg and during straining, IAP of OA-NA, OA + NA, and non-OA patients were 11.5, 17.5, and 23.5 mmHg, respectively. Application of NPT in conjunction with ABRA did not increase IAP at rest but provided significant IAP increase in OA + NA patients, when compared to OA-NA patients during coughing and straining. NPT in conjunction with ABRA offers the advantage of increase of IAP during coughing and straining.     

Comparison of direct and intravesical measurement of intraabdominal pressure in children

Purpose

The aim of this study was to compare directly measured intraabdominal pressure with the pressure measured indirectly via urinary catheter using different bladder-filling volumes in children.

Methods

Prospective observational study in pediatric intensive care unit at a university children's hospital. Three simultaneous measurements of intraabdominal pressure were performed in 14 children, mean age 1.6 months (range, 0.2-56), after cardiac surgery requiring cardiopulmonary bypass directly via an intraperitoneal dialysis catheter and indirectly via indwelling urinary catheter with bladder volumes of 1, 1.5, 2, 2.5, and 3 mL/kg of physiological saline. Of the 14 patients, 9 were mechanically ventilated at the time of the intraabdominal pressure measurements.

Results

Directly measured intraabdominal pressure ranged between 0 and 10 mm Hg and showed the highest correlation (r = 0.971, P < .0001) with the pressure measured via urinary catheter using bladder-filling volume of 1 mL/kg. The higher the bladder-filling volume, the higher was the overestimation of the intraabdominal pressure and the weaker was the correlation with the direct measurement. Overestimation of intraabdominal pressure was 1.3, 2.0, and 2.9 mm Hg, with bladder volume of 1, 2, and 3 mL/kg, respectively.

Conclusion

These data suggest that intravesical pressure closely correlates with intraabdominal pressure in children. A bladder-filling volume of 1 mL/kg is recommended for the measurement of intraabdominal pressure in children with a risk of abdominal compartment syndrome.     

Study of the Effect of Straining on the Bulbocavernosus Muscle with Evidence of a Straining–Bulbocavernosus Reflex and its Clinical Significance

The bulbocavernosus muscle (BCM) surrounds the vaginal introitus and covers the vestibular bulb. Its role in erection is known. However, as it surrounds the vaginal introitus, it may also have a role in intravaginal pressure regulation and in the pathogenesis of uterovaginal prolapse. We investigated the effect of increased intra-abdominal pressure (IAP) on the BCM, aiming to assess its possible function in supporting the uterus, vagina and anorectum. The intrarectal (representative of the IAP) and intravaginal pressures were measured by manometric catheters in 19 healthy women volunteers (mean age 46.2 ± 10.4 years). The EMG activity of the BCM and its response to straining at different pressures were recorded by a concentric needle electrode. Two types of straining were tested: sudden momentary and slow sustained. The procedure was repeated in 11 of the women after individual anesthetization of the BCM, rectum and vagina. Sudden straining (coughing) produced a significant increase in intrarectal (P<0.0001) and intravaginal (P<0.0001) pressure as well as BCM EMG activity. Slow straining effected a similar but lower response: the BCM responded gradually with pressure elevation, whereas the latency exhibited a gradual decrease. The BCM did not react to straining after individual anesthetization of the BCM, vagina and rectum, but did respond to saline administration. The results were reproducible. BCM contraction on straining postulates a reflex relationship, which we call the ‘straining–bulbocavernosus reflex’. We hypothesized that this reflex is evoked by straining and results in BCM contraction and closure of the vaginal introitus. The vagina is believed to become a closed cavity, counteracting the increased intra-abdominal pressure and the uterine tendency to prolapse. The high pressure in the closed vaginal cavity presumably supports the rectovaginal septum against the high intrarectal pressure, and is suggested to share in the prevention of rectocele. The role of BCM in the pathogenesis of uterovaginal prolapse and rectocele needs further study.     

Renal pelvic pressure responds with augmented increases to increments in intraabdominal pressure

BACKGROUND/PURPOSE: Flow of a fluid through a collapsible tube is under the influence of various factors including the external compressing pressure. Because the intraabdominal pressure may compress the ureter, an experimental study has been planned to determine and compare the normal intraabdominal and renal pelvic pressures and the alterations in renal pelvic pressure in response to the increments in intraabdominal pressure in the rabbits. METHODS: Eight adult rabbits were used for the experiment. Under general anesthesia, an urethral catheter, a nasogastric tube, and an intraperitoneal catheter were placed to measure intravesical (IVP), intragastric (IGP), and intraabdominal pressures (IAP), respectively. Intracranial pressure monitorization catheter was placed into the renal pelvis to monitor intrapelvic pressure (IPP). Basal pressure measurements have been recorded. The pressures have been recorded in every 5 minutes, and IAP has been increased gradually about 3 to 4 cm of water pressure in every step for 30-minute periods. RESULTS: Increases in the intrapelvic pressure values have been significantly higher than the increases in the IAP (P < .001). A significant correlation has been found between IPP and IAP (P = .000, r = 0.866). By using linear regression analysis the relationship has been found to be IPP = 7.303 + 1.985 (IAP). Intragastric pressure values have been higher compared with IAP values (P < .001), whereas intravesical pressures have not differed from IAP (P > .05). CONCLUSIONS: Elevations in IAP results in augmented increases in the IPP. Poiseuille and Laplace Laws suggest this augmented increase to resemble proximal ureteric obstruction. Increases in IAP may simulate proximal ureteric obstruction and may take part in the pathogenesis of hydronephrosis. J Pediatr Surg 36:901-904.     

Rupture of the knee capsule from articular hyperpressure. Experiments in cadaver knees

We used 10 cadaver knees to estimate the safe pressure during arthroscopy by measuring the volumes and pressures of irrigation fluid at different flexion angles. Maximum volumes could be contained at 35 degrees of flexion. Pressures of 200 to 450 mmHg were measured, and all the knees ruptured by extension or flexion after they were filled to 100 mmHg at 35 degrees of flexion. Fifty milliliters of irrigation fluid had to be removed if the pressure remained constant when extending from 35 degrees and 70 ml when flexing to 90 degrees. Totally, 100 ml irrigation fluid had to be removed when flexing from 35 degrees to 120 degrees. Our investigation indicates that a pressure of 150 mmHg can be tolerated by all knees. Both flexion and extension from the 35 degrees position must be done gently and slowly using a large bore, wide-open inflow and outflow tubes allowing egress of irrigation fluid to prevent capsular rupture, extravasation of irrigation fluid, vascular compromise, or compartment syndrome.     

Correlation between the prostatic vein and vertebral venous system under various conditions.

In dogs, the venous blood from the prostate gland was observed under X-ray fluoroscopy to drain into the vertebral venous system under conditions of abdominal compression, the addition of various intraabdominal pressures, and occlusion of the inferior vena cava by a balloon catheter. Pressure in the inferior vena cava and abdominal cavity were measured simultaneously. The venous blood draining from the prostate gland started to flow from the inferior vena cava into the vertebral veins at more than 25 mmHg of intraabdominal pressure with the animal in the supine position. The average pressure of the inferior vena cava draining into the vertebral veins was 12.8 +/- 1.3 mmHg in the supine position and 21.1 +/- 2.7 mmHg in the standing position. The average intraabdominal pressures were 35.5 +/- 3.9 mmHg and 30.1 +/- 2.8 mmHg, respectively. Under conditions of abdominal compression and balloon occlusion of the inferior vena cava, the materials flowed into the vertebral venous system from various routes, such as the internal iliac vein, common iliac vein, and inferior vena cava. It was suggested that the inferior vena caval blood easily enters the vertebral venous system in the standing position by adding high intraabdominal pressure, and that the vertebral venous system may be useful for experimental study of drug administration in bone metastasis of prostate cancer.     

Intraabdominal pressure rise during weight lifting as an objective measure of low-back pain

Twenty-three male patients who had chronic nonspecific low-back pain were asked to record the amount of pain they felt on an arbitrary scale while lifting light weights in different directions. During the lifts their intraabdominal pressures were recorded with an intragastric transducer. The patients who experienced extra pain during the lift had higher rises of pressure than both normal controls and those patients who did not experience extra pain. The available evidence suggests that this pressure rise may be a response to low-back pain and may be used as a method of objectively measuring that pain.     

Effect of straining on perineal muscles and their role in perineal support: identification of the straining-perineal reflex

OBJECTIVE: The functional activity of the superficial (STPM) and deep (DTPM) transverse perineal muscles is poorly addressed in the literature. We investigated the hypothesis that these muscles act to support the perineum during increased intraabdominal pressure (IAP). METHODS: 46 healthy volunteers (mean age 30.4 +/- 1.2 y, 20 nulliparous women) were studied. The IAP was recorded by a manometric catheter introduced into the rectum. The response of the perineal muscles to straining (sudden by coughing and slow by Valsalva's maneuver) was registered by a needle electrode inserted into the STPM and DTPM separately. The response was recorded again after individual anesthetization of the perineal muscles and rectum using Xylocaine. The test was repeated using saline instead of Xylocaine and was performed on both sides. RESULTS: Straining (sudden or slow sustained) effected increase of the rectal pressure and the motor unit action potentials of both perineal muscles. The higher rectal pressure was increased by straining, the higher the motor unit action potentials increased MUAPs. The latency showed a gradual decrease upon incremental rectal pressure elevation. The perineal muscles did not respond to straining after individual anesthetization of the rectum and perineal muscles, but did respond to saline administration. The response was similar from muscles on both sides. CONCLUSIONS: Perineal muscle contraction on straining postulates a reflex relationship that we call the "straining-perineal reflex." We suggest that this reflex, which results in perineal muscle contraction, supports the perineum against the increased IAP induced by straining and the tendency of the perineum to descend. The results warrant further study of the role of the straining-perineal reflex in the genesis of perineal functional disorders.