Noninvasive assessment of intra-abdominal pressure by measurement of abdominal wall tension

Three-dimensional geometric morphometric shape analysis of chest wall kinematics in different breathing conditions

Breathing motion is based on the differential activity of the thoracic, diaphragmatic and abdominal muscles. Muscle contributions differ between rest and exercise conditions and depend on posture and other factors. Traditionally, these changes are investigated on volumetric data using optoelectronic plethysmography (OEP). OEP offers insight into size variations of different chest wall (CW) compartments but does not provide three-dimensional visualization methods of CW breathing kinematics. Here we explore the use of three-dimensional geometric morphometrics to analyse size and shape changes caused by spontaneous breathing motion during quiet (QB), and recovery breathing (REC, immediately after heavy exercise) in two different postures (SIT, sitting on cycle ergometer; STA, standing position). Our findings show that size and shape differ significantly between inspiration and expiration and that differences are greater in REC than in QB. However, this is achieved by stronger expiration in SIT but by greater expiratory and inspiratory movements in STA. Shape analysis suggests that these differences may be attributed to constrained mobility of the shoulder girdle and a minor thoracic spine extension during inspiration owing to position on the ergometer. Breathing motion in STA seems biomechanically less constrained. Geometric morphometrics analyses can provide additional insights into data obtained by OEP.

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

The development, feasibility and credibility of intra-abdominal pressure measurement techniques: A scoping review

AIM

To provide a comprehensive overview on emerging direct and alternative methods for intra-abdominal pressure (IAP) measurement techniques.

METHODS

This was a scoping review study following Arksey and Malley's framework. The PubMed, EMBASE, Web of Science, EBSCO, Scopus and ProQuest databases were searched, and we only considered studies published from 2000 as we have extended the data from two previous reviews. Original studies that reported on the development, feasibility and credibility of IAP measurement techniques were included.

RESULTS

Forty-two of 9954 screened articles were included. IAP measurement techniques include three major categories: direct, indirect and less invasive measurement techniques. Agreement analyses were performed in most studies, and some explored the safety, time expenditure and reproducibility of IAP measurement techniques.

CONCLUSIONS

Clinical data assessing the validation of new IAP measurement techniques or the reliability of established measurement techniques remain lacking. Considering the cost and invasiveness, direct measurement is not recommended as a routine method for IAP measurement and should be preserved for critically ill patients where standard techniques are contraindicated or could be inaccurate. The measurement accuracy, reliability and sensitivity of the transrectal and transfemoral vein methods remain insufficient and cannot be recommended as surrogate IAP measures. Transvesical measurement is the most widely used method, which is the potentially most easy applicable technique and can be used as a reliable method for continuous and intermittent IAP measurement. Wireless transvaginal method facilitates the quantitative IAP measurement during exercise and activity, which laying the foundations for monitoring IAP outside of the clinic environment, but the accuracy of this technique in measuring absolute IAP cannot be determined at present. Less invasive technology will become a new trend to measure IAP and has substantial potential to replace traditional IAP measurement technologies, but further validation and standardization are still needed. Medical professionals should choose appropriate measurement tools based on the advantages and disadvantages of each IAP technique in combination with assessing specific clinical situations.

Muscle-driven forward dynamic active hybrid model of the lumbosacral spine: combined FEM and multibody simulation

Most spine models belong to either the musculoskeletal multibody (MB) or finite element (FE) method. Recently, coupling of MB and FE models has increasingly been used to combine advantages of both methods. Active hybrid FE-MB models, still rarely used in spine research, avoid the interface and convergence problems associated with model coupling. They provide the inherent ability to account for the full interplay of passive and active mechanisms for spinal stability. In this paper, we developed and validated a novel muscle-driven forward dynamic active hybrid FE-MB model of the lumbosacral spine (LSS) in ArtiSynth to simultaneously calculate muscle activation patterns, vertebral movements, and internal mechanical loads. The model consisted of the rigid vertebrae L1-S1 interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, facet joints, and force actuators representing the muscles. Morphological muscle data were implemented via a semi-automated registration procedure. Four auxiliary bodies were utilized to describe non-linear muscle paths by wrapping and attaching the anterior abdominal muscles. This included an abdominal plate whose kinematics was optimized using motion capture data from upper body movements. Intra-abdominal pressure was calculated from the forces of the abdominal muscles compressing the abdominal cavity. For the muscle-driven approach, forward dynamics assisted data tracking was used to predict muscle activation patterns that generate spinal postures and balance the spine without prescribing accurate spinal kinematics. During calibration, the maximum specific muscle tension and spinal rhythms resulting from the model dynamics were evaluated. To validate the model, load cases were simulated from -10° extension to +30° flexion with weights up to 20 kg in both hands. The biomechanical model responses were compared with in vivo literature data of intradiscal pressures, intra-abdominal pressures, and muscle activities. The results demonstrated high agreement with this data and highlight the advantages of active hybrid modeling for the LSS. Overall, this new self-contained tool provides a robust and efficient estimation of LSS biomechanical responses under in vivo similar loads, for example, to improve pain treatment by spinal stabilization therapies.

Affecting factors for abdominal incisional tension in surgery of dogs and cats

OBJECTIVE

Proper assessment of intraoperative abdominal incisional tension helps to select the appropriate sutures and suture method. Wound tension is usually thought to be associated with wound size, but few relevant articles have been reported. The aim of this study was to investigate the core factors influencing abdominal incisional tension and construct regression equations to judge incisional tension in clinical surgery.

METHODS

Medical records were collected from clinical surgical cases at the Teaching Animal Hospital of Nanjing Agricultural University from March 2022 to June 2022. The data collected mainly included the body weight, and the incisional length, margin, and tension. The core factors affecting abdominal wall incisional tension were screened by correlation analysis, random forest analysis, and multiple linear regression analysis.

RESULTS

Although correlation analysis showed that multiple same and deep layer abdominal incision parameters and body weight were significantly correlated with abdominal incisional tension. However, the same layer of abdominal incisional margin had the largest correlation coefficient. In random forest models, the abdominal incisional margin had the main contribution to the prediction of the same layer's abdominal incisional tension. In the multiple linear regression model, all incisional tension could be predicted by the same layer of abdominal incisional margin as the only independent variable, except for canine muscle and subcutaneous. The canine muscle and subcutaneous incisional tension were binary regressions with the same layer's abdominal incision margin and body weight.

CONCLUSION

The same layer's abdominal incisional margin is the core factor positively related to the abdominal incisional tension intraoperatively.

Abdominal wall tension increases using Dynamic Neuromuscular Stabilization principles in different postural positions

BACKGROUND

Intra-abdominal pressure (IAP) is an important mechanism stabilizing the spine and trunk. IAP regulation depends on the coordination of abdominal muscles, diaphragm and pelvic floor muscles.

OBJECTIVE

To determine the differences in abdominal wall tension (AWT) of various postural positions, first without any correction, then after verbal and manual instructions according to Dynamic Neuromuscular Stabilization (DNS) principles.

METHODS

In a cross-sectional observational study, thirty healthy individuals (mean age = 22.73 ± 1.91 years) were fitted with two Ohmbelt sensors contralaterally above the inguinal ligament and in the upper lumbar triangle. AWT was measured during five postural positions: sitting, supine with legs raised, squat, bear and hang position. First, spontaneous AWT was measured, then again after manual and verbal instructions following DNS principles.

RESULTS

AWT increased significantly with DNS instructions compared to spontaneous activation. Both sensors recorded significant increases (p < .01; Cohen's d = -1.13 to -2.06) in all observed postural situations. The increase in activity occurred simultaneously on both sensors, with no significant differences noted in pressure increases between the sensors. The greatest activation for both sensors occurred in the bear position. Significant increases in activity were identified for both sensors in the supine leg raise position and in the bear position compared to spontaneous activation in sitting (p < .001). There were no statistically significant differences (for both sensors) between women and men in any position.

CONCLUSION

The amount of AWT significantly increases after verbal and manual instructions according to DNS. The greatest abdominal wall activation was achieved in the bear position.

Indentation of a pressurized silicon stomach model - A non-invasive study of gastric wall stiffness and pressurized gastric content stiffness

BACKGROUND AND AIMS

Evaluation of gastric wall stiffness and intragastric pressure is essential for detailed assessments of gastric accommodation. However, non-invasive assessments are needed for large scale clinical studies and none of the existing methods takes abdominal wall effect into the calculation. This study aimed to assess gastric wall stiffness and gastric content stiffness as a proxy for intragastric pressure using novel mechanical modeling and non-invasive indentation tests on a silicon stomach model.

METHODS

A silicon stomach model (scaling 1:1 with the human stomach) was indented using a pressure algometer at intragastric pressures from 0 to 0.8 kPa. Wall thicknesses and luminal cross-sectional areas along the stomach were measured with ultrasound images. The gastric wall stiffness was compared between measurements from tensile tests on strips cut from the silicon stomach and estimations from a shell indentation model. The pressurized gastric content stiffness was predicted from a bonded two-layer axisymmetric half-space indentation model.

RESULTS

The gastric wall stiffness estimated from the shell indentation model showed no difference to measurements from the mechanical tests on the cutting strips (p = 0.14). The predicted gastric content stiffness was strongly associated with the intragastric pressure (r > 0.83, p < 0.001).

CONCLUSIONS

The mechanical model developed in this study can simultaneously predict the gastric wall stiffness and the pressurized gastric content stiffness. In future studies, the method can be applied to reveal intragastric pressure conditions non-invasively via the pressurized gastric content stiffness during gastric accommodation and emptying such as with magnetic resonance imaging.

Intra-abdominal pressure correlates with abdominal wall tension during clinical evaluation tests

BACKGROUND

The abdominal muscles play an important respiratory and stabilization role, and in coordination with other muscles regulate the intra-abdominal pressure stabilizing the spine. The evaluation of postural trunk muscle function is critical in clinical assessments of patients with musculoskeletal pain and dysfunction. This study evaluates the relationship between intra-abdominal pressure measured as anorectal pressure with objective abdominal wall tension recorded by mechanical-pneumatic-electronic sensors.

METHODS

In a cross-sectional observational study, thirty-one asymptomatic participants (mean age = 26.77 ± 3.01 years) underwent testing to measure intra-abdominal pressure via anorectal manometry, along with abdominal wall tension measured by sensors attached to a trunk brace (DNS Brace). They were evaluated in five different standing postural-respiratory situations: resting breathing, Valsalva maneuver, Müller's maneuver, instructed breathing, loaded breathing when holding a dumbbell.

FINDINGS

Strong correlations were demonstrated between anorectal manometry and DNS Brace measurements in all scenarios; and DNS Brace values significantly predicted intra-abdominal pressure values for all scenarios: resting breathing (r = 0.735, r² = 0.541, p < 0.001), Valsalva maneuver (r = 0.836, r² = 0.699, p < 0.001), Müller's maneuver (r = 0.651, r² = 0.423, p < 0.001), instructed breathing (r = 0.708, r² = 0.501, p < 0.001), and loaded breathing (r = 0.921, r² = 0.848, p < 0.001).

INTERPRETATION

Intra-abdominal pressure is strongly correlated with, and predicted by abdominal wall tension monitored above the inguinal ligament and in the area of superior trigonum lumbale. This study demonstrates that intra-abdominal pressure can be evaluated indirectly by monitoring the abdominal wall tension.

A New Device for Measuring Abdominal Wall Tension and Its Value in Screening Abdominal Infection

OBJECTIVE

This study is the largest clinical study of noninvasive Abdominal wall tension (AWT) measurement with a tensiometer to date. It also initially applies a polynomial regression equation to analyze the correlation between AWT measurement and intravesical pressure (IVP) measurement and remarkably finds interesting changes between different IVP intervals and AWT.

METHODS

Critically ill patients who were treated in the intensive care unit (ICU) of Daping Hospital, Army Medical University, from August 30, 2018, to June 30, 2020, and met the inclusion criteria were prospectively included in this study. The patients were divided into an intra-abdominal hypertension group and a non-intra-abdominal hypertension group and an abdominal infection group and no abdominal infection group. AWT and IVP were measured at 9 points on the abdominal wall on the first day after admission to the ICU. The correlations between AWTs and IVP were analyzed, and the role of AWT in the diagnosis of complications of abdominal infection and the prediction of adverse prognosis were analyzed.

RESULTS

A total of 127 patients were included. The average AWT and IVP were 2.77±0.38 N/mm and 12.31±7.01 mmHg, respectively, on the first day of admission. There was a positive correlation between AWT and IVP (correlation coefficient r = 0.706, p < 0.05). The polynomial regression model was AWT= -1.616×10-3 IVP2 +8.323×10-2 IVP+2.094. The cutoff value of the sensitivity and specificity of AWT for the diagnosis of abdominal infection was 2.57 N/mm. Furthermore, AWT = 2.57 N/mm had the best diagnostic efficiency, which was better than that of IAH and lactate.

CONCLUSION

There was a correlation between AWT and IVP. AWT measurement was helpful in the diagnosis of IAH and abdominal infection complications and can therefore serve as a new method for the clinical diagnosis of IVP and abdominal infection.

Postural and respiratory function of the abdominal muscles: A pilot study to measure abdominal wall activity using belt sensors

BACKGROUND: The abdominal muscles play an important respiratory and stabilization role, and in coordination with other muscles regulate intra-abdominal pressure (IAP) to stabilize the spine. OBJECTIVE: To examine a new, non-invasive method to measure activation of the abdominal wall and compare changes in muscle activation during respiration while breathing under a load, and during instructed breathing. METHODS: Thirty-five healthy individuals completed this observational crossover study. Two capacitive force sensors registered the abdominal wall force during resting breathing stereotype, instructed breathing stereotype and under a load. RESULTS: Mean abdominal wall force increased significantly on both sensors when holding the load compared to resting breathing (Upper Sensor: P< 0.0005, d=-0.46, Lower Sensor: P< 0.0005, d=-0.56). The pressure on both sensors also significantly increased during instructed breathing compared to resting breathing (US: P< 0.0005, d=-0.76, LS: P< 0.0005, d=-0.78). CONCLUSIONS: The use of capacitive force-sensors represent a new, non-invasive method to measure abdominal wall activity. Clinically, belts with capacitive force sensors can be used as a feedback tool to train abdominal wall activation.

A concise overview of non-invasive intra-abdominal pressure measurement techniques: from bench to bedside

This review presents an overview of previously reported non-invasive intra-abdominal pressure (IAP) measurement techniques. Each section covers the basic physical principles and methodology of the various measurement techniques, the experimental results, and the advantages and disadvantages of each method. The most promising non-invasive methods for IAP measurement are microwave reflectometry and ultrasound assessment, in combination with an applied external force.

Ultrasonography in the diagnosis and monitoring of intra-abdominal hypertension and abdominal compartment syndrome: Ultrasonografia a nadciśnienie wewnątrzbrzuszne i zespół przedziału brzusznego

Despite their considerable clinical significance, intra-abdominal hypertension and abdominal compartment syndrome are rarely discussed in the context of ultrasonography. They occur in critically ill patients, usually hospitalized in intensive care units. Early diagnosis of these conditions is of key importance for prognosis as it allows for proper treatment and prevents high mortality. Although there are various methods for the assessment of intra-abdominal pressure, a measurement using a sensor-equipped catheter placed in the bladder is the gold standard. However, this technique does not allow to identify the etiology of the problem, which is usually resolved by analyzing patient's clinical data supported by imaging findings. Computed tomography is most often used for this purpose. Recent years have proved that point-of-care ultrasonography is also useful in this respect. This issue has become the basis for developing this review paper, which describes the opinion of the experts of the World Society of the Abdominal Compartment Syndrome on the nomenclature, classification and diagnosis of intra-abdominal hypertension. We also presented preliminary data on the role of ultrasound in the diagnosis and monitoring of intra-abdominal hypertension and the contribution of this modality to the choice of appropriate treatment for patients presenting with this clinical condition. A multi-center study used point-of-care ultrasonography to assess the position of a g-tube in the stomach and its contents, intraluminal content status and bowel motor function, the monitoring of gastric drainage and forced intestinal evacuation, the presence of ascites and ascitic status without and after paracentesis. Even when simplified, the method was found to be very useful.

Effects of intra-abdominal pressure on laparoscopic working space in domestic rabbits (Oryctolagus cuniculus)

OBJECTIVE

To assess the effects of 3 intra-abdominal pressures (IAPs) on pneumoperitoneal (laparoscopic working space) volume in domestic rabbits (Oryctolagus cuniculus).

ANIMALS

6 female New Zealand White rabbits.

PROCEDURES

A Latin-square design was used to randomly allocate sequences of 3 IAPs (4, 8, and 12 mm Hg) to each rabbit in a crossover study. Rabbits were anesthetized, subumbilical cannulae were placed, and CT scans were performed to obtain baseline measurements. Each IAP was achieved with CO₂ insufflation and maintained for ≥ 15 minutes; CT scans were performed with rabbits in dorsal, left lateral oblique, and right lateral oblique recumbency. The abdomen was desufflated for 5 minutes between treatments (the 3 IAPs). Pneumoperitoneal volumes were calculated from CT measurements with 3-D medical imaging software. Mixed linear regression models evaluated effects of IAP, rabbit position, and treatment order on working space volume.

RESULTS

Mean working space volume at an IAP of 8 mm Hg was significantly greater (a 19% increase) than that at 4 mm Hg, and was significantly greater (a 6.9% increase) at 12 mm Hg than that at 8 mm Hg. Treatment order, but not rabbit position, also had a significant effect on working space. Minor adverse effects reported in other species were observed in some rabbits.

CONCLUSIONS AND CLINICAL RELEVANCE

A nonlinear increase in abdominal working space was observed with increasing IAP. Depending on the type of procedure and visual access requirements, IAPs > 8 mm Hg may not provide a clinically important benefit for laparoscopy in rabbits.

3D surface imaging of abdominal wall muscular contraction

BACKGROUND AND OBJECTIVE

The biomechanical analysis of the abdominal wall should take into account muscle activation and related phenomena, such as intra-abdominal pressure variation and abdomen surface deformation. The geometry of abdominal surface and its deformation during contraction have not been extensively characterized, while represent a key issue to be investigated.

METHODS

In this work, the antero-lateral abdominal wall surface of ten healthy volunteers in supine position is acquired via laser scanning in relaxed conditions and during abdominal muscles contraction, repeating each acquisition six times. The average relaxed and contracted abdominal surfaces are compared for each subject and displacements measured.

RESULTS

Muscular activation induces raising in the region adjacent to linea alba along the posterior-anterior direction and a simultaneous lowering along lateral-medial direction of the abdominal wall sides. Displacements reach a maximum value of 12.5 mm for the involved subjects. The coefficient of variation associated to the abdomen surface measurements in the same configuration (relaxed or contracted) is below 0.75%. Non-parametric Mann-Whitney U test highlights that the differences between relaxed and contracted abdominal wall surfaces are significant (p < 0.01).

CONCLUSIONS

Laser scanning is an accurate and reliable method to evaluate surface changes on the abdominal wall during muscular contraction. The results of this experimental activity can be useful to validate numerical models aimed at describing abdominal wall biomechanics.

Abdominal Compliance and Laparoscopy: A Review

Background and Objectives

Creating and maintaining a pneumoperitoneum to perform laparoscopy is governed by gas laws and the limiting physical constraints of the abdomen.

Methods

A review of how gas, biomechanical and physical properties affect the abdomen and a systematic structured Medline and PubMed search was conducted to identify relevant studies related to the topic.

Results

Abdominal compliance is a measure of ease of abdominal expansion and is determined by the elasticity of the abdominal wall and diaphragm. It is the change in intra-abdominal volume per change in intra-abdominal pressure. Caution should be exercised with pressures exceeding 12 millimeters mercury since this is defined as intra-abdominal hypertension.

Conclusions

Abdominal compliance has its limits, is unique for each patient and pressure-volume curves cannot be easily predicted. Using the lowest possible pressure to accomplish the surgical task without compromising surgical outcome is the desired goal. The clinical importance is caution and knowing there is a point where more pressure does not increase working space and only increases pressure.

Effect of retension sutures on abdominal pressure after abdominal surgery

PURPOSE

To evaluate the effect of retention sutures on abdominal pressure and postoperative prognosis in abdominal surgery patients.

METHODS

This prospective cohort study included patients who were admitted to Daping Hospital from May 15, 2014 to October 11, 2014. A total of 57 patients were enrolled, including 18 patients in the "U" type retention suture group, 17 patients in the intermittent retention suture group, and 22 patients in non-retention suture group. The demographic data, clinical data and risk factors for abdominal wound dehiscence were recorded. The bladder pressure (IVP) was monitored preoperatively, intraoperatively, and four days postoperatively. Additionally, the incidence of abdominal wound dehiscence and infection 14 days after the operation was recorded.

RESULTS

During the operation, the IVP decreased and then increased; it was at its lowest 1 h after the start of the operation (5.3 mmHg ± 3.2 mmHg) and peaked after tension-reducing (8.8 mmHg ± 4.0 mmHg). The IVP values in the "U" type retention suture group and intermittent retention suture group were higher than in the non-retention suture group 4 days after operation (p < 0.005). The Visual Analogue Scale (VAS) pain scores were 3.9 ± 2.2, 3.8 ± 2.0, and 3.0 ± 1.0 in the retention suture group, intermittent retention suture group and non-retention suture group, respectively. The VAS pain scores in the "U" type tension-reducing group and intermittent tension-reducing group were higher than in the non-tension-reducing group (p < 0.005).

CONCLUSION

Although retention sutures may reduce the incidence of postoperative wound dehiscence in abdominal surgery patients, they can increase the IVP and postoperative pain.

Strategies for Intravenous Fluid Resuscitation in Trauma Patients

Intravenous fluid management of trauma patients is fraught with complex decisions that are often complicated by coagulopathy and blood loss. This review discusses the fluid management in trauma patients from the perspective of the developing world. In addition, the article describes an approach to specific circumstances in trauma fluid decision-making and provides recommendations for the resource-limited environment.

The neglected role of abdominal compliance in organ-organ interactions

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Noninvasive monitoring of intra-abdominal pressure by measuring abdominal wall tension

BACKGROUND

Noninvasive monitoring of intra-abdominal pressure (IAP) by measuring abdominal wall tension (AWT) was effective and feasible in previous postmortem and animal studies. This study aimed to investigate the feasibility of the AWT method for noninvasively monitoring IAP in the intensive care unit (ICU).

METHODS

In this prospective study, we observed patients with detained urethral catheters in the ICU of Shanghai Tenth People's Hospital between April 2011 and March 2013. The correlation between AWT and urinary bladder pressure (UBP) was analyzed by linear regression analysis. The effects of respiratory and body position on AWT were evaluated using the paired samples t test, whereas the effects of gender and body mass index (BMI) on baseline AWT (IAP<12 mmHg) were assessed using one-way analysis of variance.

RESULTS

A total of 51 patients were studied. A significant linear correlation was observed between AWT and UBP (R=0.986, P<0.01); the regression equation was Y=-1.369+9.57X (P<0.01). There were significant differences among the different respiratory phases and body positions (P<0.01). However, gender and BMI had no significant effects on baseline AWT (P=0.457 and 0.313, respectively).

CONCLUSIONS

There was a significant linear correlation between AWT and UBP and respiratory phase, whereas body position had significant effects on AWT but gender and BMI did not. Therefore, AWT could serve as a simple, rapid, accurate, and important method to monitor IAP in critically ill patients.

The effect of standing and sitting postures on breathing in brass players

Purpose

The object of this study was to examine the effect of posture on breathing in brass players. Breathing when standing was compared with sitting erect on a flat, downward or upward sloping seat, or on a reclining seat.

Methods

Spirometry was used to measure aspects of lung function. Muscle activity and respiratory movements during different playing tasks were recorded using electromyography and inductive plethysmography.

Results

Only sitting in a reclining position produced statistically significantly lower values for VC, FVC, FEV1, PEF than standing. When players were asked to produce a note of maximum duration, only a downward sloping seat caused a significant change (an 11% reduction) compared to standing. When seated, the abdominal component of respiratory movement was significantly higher during these long notes than when standing, though maximum activity in abdominal wall muscles was significantly reduced (by 32–44%). On a downward sloping seat, muscle activity was significantly higher (9%) than on a flat seat. Tongued and untongued sforzando notes recruited significantly less abdominal muscle activity (33–67%) when sitting than when standing. When playing a trumpet study, abdominal muscle activity was significantly reduced on a downward sloping seat (by 32%) and on a flat seat (by 40%) in comparison to standing. Muscle activity in the two sitting positions were not significantly different.

Conclusion

Though brass players are often told to “sit as if standing”, abdominal muscle activity is always significantly reduced when sitting on a flat or downward sloping seat, however when greater respiratory effort is required, activity on downward sloping seats may rise closer to that of standing.

Abdominal contributions to cardiorenal dysfunction in congestive heart failure

Current pathophysiological models of congestive heart failure unsatisfactorily explain the detrimental link between congestion and cardiorenal function. Abdominal congestion (i.e., splanchnic venous and interstitial congestion) manifests in a substantial number of patients with advanced congestive heart failure, yet is poorly defined. Compromised capacitance function of the splanchnic vasculature and deficient abdominal lymph flow resulting in interstitial edema might both be implied in the occurrence of increased cardiac filling pressures and renal dysfunction. Indeed, increased intra-abdominal pressure, as an extreme marker of abdominal congestion, is correlated with renal dysfunction in advanced congestive heart failure. Intriguing findings provide preliminary evidence that alterations in the liver and spleen contribute to systemic congestion in heart failure. Finally, gut-derived hormones might influence sodium homeostasis, whereas entrance of bowel toxins into the circulatory system, as a result of impaired intestinal barrier function secondary to congestion, might further depress cardiac as well as renal function. Those toxins are mainly produced by micro-organisms in the gut lumen, with presumably important alterations in advanced heart failure, especially when renal function is depressed. Therefore, in this state-of-the-art review, we explore the crosstalk between the abdomen, heart, and kidneys in congestive heart failure. This might offer new diagnostic opportunities as well as treatment strategies to achieve decongestion in heart failure, especially when abdominal congestion is present. Among those currently under investigation are paracentesis, ultrafiltration, peritoneal dialysis, oral sodium binders, vasodilator therapy, renal sympathetic denervation and agents targeting the gut microbiota.

Effect of intra-abdominal pressure on respiratory function in patients undergoing ventral hernia repair

AIM

To determine the influence of intra-abdominal pressure (IAP) on respiratory function after surgical repair of ventral hernia and to compare two different methods of IAP measurement during the perioperative period.

METHODS

Thirty adult patients after elective repair of ventral hernia were enrolled into this prospective study. IAP monitoring was performed via both a balloon-tipped nasogastric probe [intragastric pressure (IGP), CiMON, Pulsion Medical Systems, Munich, Germany] and a urinary catheter [intrabladder pressure (IBP), UnoMeterAbdo-Pressure Kit, UnoMedical, Denmark] on five consecutive stages: (1) after tracheal intubation (AI); (2) after ventral hernia repair; (3) at the end of surgery; (4) during spontaneous breathing trial through the endotracheal tube; and (5) at 1 h after tracheal extubation. The patients were in the complete supine position during all study stages.

RESULTS

The IAP (measured via both techniques) increased on average by 12% during surgery compared to AI (P < 0.02) and by 43% during spontaneous breathing through the endotracheal tube (P < 0.01). In parallel, the gradient between РаСО2 and EtCO2 [Р(а-et)CO2] rose significantly, reaching a maximum during the spontaneous breathing trial. The PаO2/FiO2 decreased by 30% one hour after tracheal extubation (P = 0.02). The dynamic compliance of respiratory system reduced intraoperatively by 15%-20% (P < 0.025). At all stages, we observed a significant correlation between IGP and IBP (r = 0.65-0.81, P < 0.01) with a mean bias varying from -0.19 mmHg (2SD 7.25 mmHg) to -1.06 mm Hg (2SD 8.04 mmHg) depending on the study stage. Taking all paired measurements together (n = 133), the median IGP was 8.0 (5.5-11.0) mmHg and the median IBP was 8.8 (5.8-13.1) mmHg. The overall r (2) value (n = 30) was 0.76 (P < 0.0001). Bland and Altman analysis showed an overall bias for the mean values per patient of 0.6 mmHg (2SD 4.2 mmHg) with percentage error of 45.6%. Looking at changes in IAP between the different study stages, we found an excellent concordance coefficient of 94.9% comparing ΔIBP and ΔIGP (n = 117).

CONCLUSION

During ventral hernia repair, the IAP rise is accompanied by changes in Р(а-et)CO2 and PаO2/FiO2-ratio. Estimation of IAP via IGP or IBP demonstrated excellent concordance.

Intra-abdominal pressure, intra-abdominal hypertension, and pregnancy: a review

The last several decades have seen many advances in the recognition and prevention of the abdominal compartment syndrome (ACS) and its precursor, intra-abdominal hypertension (IAH). There has also been a relative explosion of knowledge in the critical care, trauma, and surgical populations, and the inception of a society dedicated to its understanding, the World Society of the Abdominal Compartment Syndrome (WSACS). However, there has been almost no recognition or appreciation of the potential presence, influence, and management of intra-abdominal pressure (IAP), IAH, and ACS in pregnancy. This review highlights the importance and relevance of IAP in the critically ill parturient, the current lack of normative IAP values in pregnancy today, along with a review of the potential relationship between IAH and maternal diseases such as preeclampsia-eclampsia and its potential impact on fetal development. Finally, current IAP measurement guidelines are questioned, as they do not take into account the gravid uterus and its mechanical impact on intra-vesicular pressure.