Upper urinary tract pressures in endourology: a systematic review of range,variables and implications

Objectives

To systematically review the literature to ascertain the upper tract pressures generated during endourology, the relevant influencing variables and clinical implications.

Materials and Methods

A systematic review of the MEDLINE, Scopus and Cochrane databases was performed by two authors independently (S.C., N.D.). Studies reporting ureteric or intrarenal pressures (IRP) during semi-rigid ureteroscopy (URS)/flexible ureterorenoscopy (fURS)/percutaneous nephrolithotomy (PCNL)/miniaturized PCNL (mPCNL) in the period 1950–2021 were identified. Both in vitro and in vivo studies were considered for inclusion. Findings were independently screened for eligibility based on content, with disagreements resolved by author consensus. Data were assessed for bias and compiled based on predefined variables.

Results

Fifty-two studies met the inclusion criteria. Mean IRP appeared to frequently exceed a previously proposed threshold of 40 cmH₂O. Semi-rigid URS with low-pressure irrigation (gravity <1 m) resulted in a wide mean IRP range (lowest reported 6.9 cmH₂O, highest mean 149.5 ± 6.2 cmH₂O; animal models). The lowest mean observed with fURS without a ureteric access sheath (UAS) was 47.6 ± 4.1 cmH₂O, with the maximum peak IRP being 557.4 cmH₂O (in vivo human data). UAS placement significantly reduced IRP during fURS, but did not guarantee pressure control with hand-operated pump/syringe irrigation. Miniaturization of PCNL sheaths was associated with increased IRP; however, a wide mean human IRP range has been recorded with both mPCNL (lowest −6.8 ± 2.2 cmH₂O [suction sheath]; highest 41.2 ± 5.3 cmH₂O) and standard PCNL (lowest 6.5 cmH₂O; highest 41.2 cmH₂O). Use of continuous suction in mPCNL results in greater control of mean IRP, although short pressure peaks >40 cmH₂O are not entirely prevented. Definitive conclusions are limited by heterogeneity in study design and results. Postoperative pain and pyrexia may be correlated with increased IRP, however, few in vivo studies correlate clinical outcome with measured IRP.

Conclusions

Intrarenal pressure generated during upper tract endoscopy often exceeds 40 cmH₂O. IRP is multifactorial in origin, with contributory variables discussed. Larger prospective human in vivo studies are required to further our understanding of IRP thresholds and clinical sequelae.     

Leak-Point Pressure: Clinical Application of Values at Two Different Volumes

A prospective analysis of 306 consecutive patients with genuine stress incontinence was performed to evaluate the clinical usefulness of additional leak-point pressure (LPP) determination at 200 ml. LPP values at both volumes were compared to maximal urethral closure pressure (MUCP) in an attempt to determine a critical cut-off value for the detection of a low MUCP (≤20 cmH₂O). A positive LPP at 150 ml was found in 157 patients. The mean LPP for patients with a low MUCP was 58.5 cmH₂O compared to 71.6 for those with a normal MUCP, which was statistically significant (p = 0.01). The correlation coefficient between LPP and MUCP was 0.317. A negative LPP was found in 30% (24/79) of the total having a low MUCP. The addition of values for LPP at 200 ml resulted in an increase in the number who leaked to 191, a 50% increase in the detection rate of low MUCP and a statistically significant relationship between LPP ≤60 cmH₂O and low MUCP. Various critical cut-off values for LPP demonstrated good specificity but poor sensitivity for the detection of a low MUCP. It was concluded that there was a statistically significant relationship between LPP and MUCP. Performing LPP at 200 ml provides additional clinically useful diagnostic information.     

ProSeal?-Kehlkopfmaske in normalgewichtigen und adip?sen Patienten

Background

Most of the data on combining pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) come from studies with an endotracheal tube (ETT) whereas data on utilization of PEEP with a laryngeal mask airway (LMA) are limited. The LMA-ProSeal? (PLMA) forms a more effective seal of the airway than the LMA-Classic? (CLMA). The application of PEEP when PCV is used with the PLMA could have an impact on oxygenation in adult patients.

Methods

For this study 148 patients with an mean age of 44 years (range18?C65 years) and mean weight of 86?kg (range 49?C120?kg) were recruited in 2 groups: group?N _(Normal): body-mass index (BMI) <30?kg/m² and group?O _(Obesity) BMI ??30 and <36?kg/m². Cardiovascular and pulmonary disease and a history of smoking were exclusion criteria in addition to the usual LMA contraindications. The bispectral index-guided (BIS) anesthesia technique was used with propofol, fentanyl, and remifentanil without muscle relaxants. Measurement of PLMA seal pressure served as recruitment maneuver and PCV was randomly combined with 0?cmH₂O, 5?cmH₂O or 8?cmH₂O PEEP. An arterial blood gas sample was taken 50?min after induction of anesthesia under an inspiratory oxygen fraction (F_IO₂₎ of 0.3. In the first part partial oxygen pressure (p_aO₂) under 0?cmH₂O was compared with p_aO₂ under 5?cmH₂O and in the second part p_aO₂ under 5?cmH₂O was compared with p_aO₂ under 8?cmH₂O. A significant difference was set as p<0.025.

Results

The PLMA could be placed after 3 attempts in 147 patients. The mean seal pressure was in the range of 24?C30?cm?H₂O. Application of randomized PEEP was possible in all patients and ventilation was comparable between corresponding groups. In group?N no differences were found in part?1 (139±28 vs. 141±28?mmHg, p=0.88) or part?2 (127±24 vs. 134±26?mmHg, p=0.35). In group?O there was a significant difference in p_aO₂ in part?1 (75±12 vs. 94±18?mmHg, p=0.02) but not in part?2 (92±21 vs. 103±18?mmHg, p=0.04).

Conclusions

The application of PEEP when PCV is used with the PLMA results in improved oxygenation in obese patients with a BMI ??30 and <36?kg/m² but not in normal weight patients. Alveolar recruitment produced by seal pressure measurements below 30?cm?H₂O was sufficient to produce a clinically significant improvement in oxygenation in most obese patients and there was a significant improvement of oxygenation with PEEP=5?cmH₂O. Both findings are in contrast to findings of studies using an ETT which suggests that higher pressures (40?cmH₂O) are needed for recruitment of collapsed alveoli and higher PEEP (10?cmH₂O) is needed to produce a clinically significant improvement in oxygenation in obese patients. The results of this study support data showing that the consequences of bronchopulmonary airway reactions known to occur with an ETT are less pronounced or absent when an LMA is used.     

Positive bladder cooling reflex in patients with bladder outlet obstruction due to benign prostatic hyperplasia

The bladder cooling reflex was evaluated in patients with bladder outlet obstruction to study the effect of obstruction on the afferent neural function of the bladder, especially on the C-afferents. The bladder cooling test was performed by infusion of 0 °C saline into the bladder with simultaneous detrusor pressure measurement in 104 patients with bladder outlet obstruction due to benign prostatic hyperplasia. In 49 patients (47%) a positive cooling reflex was observed. This was defined as a rise in the detrusor pressure following cold saline instillation exceeding 15 cmH₂O (range 15–130 cmH₂O, mean 60.6 cmH₂O; positive group). In the remainder of cases the pressure rise ranged from 0 to 12 cmH₂O (mean 6.1 cmH₂O; negative group). Bladder outlet obstruction may cause some alteration in the afferent neural function of the bladder, in particular of the C-afferent fibers.     

Randomized evaluation of the size 2 laryngeal tube and classical laryngeal mask airway in different head and neck positions in children under positive pressure ventilation

Purpose

The aim of this study was to evaluate the applicability of the laryngeal tube (LT) size 2 and the classical laryngeal mask airway (LMA) size 2 in different head–neck positions under positive pressure ventilation in children by measuring leak pressures, peak pressures and the achievable tidal volumes under positive pressure ventilation.

Methods

Forty children were randomized to receive airway management by either the LT or LMA as the primary device. Leak pressures, peak pressures and tidal volumes under positive pressure ventilation were measured in the neutral, anteflection, retroversion, left-rotation and right-rotation head–neck positions.

Results

In all head–neck positions, the leak pressures were significantly higher for the LT than for the LMA (neutral 25.9 ± 7.0 vs. 19.1 ± 5.7 cmH₂O; anteflection 29.7 ± 7.1 vs. 24.2 ± 8.9 cmH₂O; retroversion 24.1 ± 7.6 vs. 17.2 ± 6.9 cmH₂O). In both devices, the peak ventilation pressures were higher in the anteflection position (LT 27.1 ± 6.3 cmH₂O; LMA 17.8 ± 6.7 cmH₂O) than in the retroversion position (LT 13.7 ± 3.9 cmH₂O; LMA 12.7 ± 3.6 cmH₂O). Compared to the respirator settings, lower tidal volumes were achieved in the anteflection position (LT 65 ± 48 vs. 129 ± 38 ml, LMA 100 ± 21 vs. 125 ± 29 ml) as compared to the other positions.

Conclusion

Based on our results, we suggest that in anaesthetized children, the size 2 LT, compared to the size 2 LMA, may be more suitable for positive pressure ventilation due to favorable leak and peak pressures. Both devices can be safely used in head–neck positions other than neutral. Most disadvantageous with regards to the measured parameters was the anteflection position, especially for the LT.     

Klinische Evaluation eines Überdruckventils für Kindertuben mit Cuff

Objective

The safe use of cuffed tracheal tubes for children necessitates a cuff pressure limitation at 20–25 cmH₂O. The aim of the study was to evaluate the reliability and benefit of a new cuff pressure release valve (opening pressure 20 cmH₂O) for children intubated with a cuffed tracheal tube.

Methods

In a prospective, observational trial cuff pressure was recorded in paediatric and adolescent patients intubated with a cuffed tracheal tube during sevoflurane/nitrous oxide anaesthesia. The cuff pressure release valve was interposed between the cuff manometer and the pilot balloon. In 25 patients measurements were started at the initial opening pressure (group A) and in a further 25 patients measurements were started at the minimal sealing cuff pressure (group B).

Results

A total of 50 patients, aged from 0.4 to 17.8 years (median 7.4 years) were enrolled in the study. The opening pressure measured (group A) was 19.7±0.8 cmH₂O and the cuff sealing pressure (group B) was 11.7±2.9 cmH₂O (range 6–16 cmH₂O). Mean cuff pressure values in group A were 20.4±1.6 cmH₂O and 16.5±3.3 cmH₂O in group B. In one patient (group A) the cuff pressure exceeded 25 cmH₂O and was manually decreased to 20 cmH₂O. In total, 24 filling procedures (group A 14; group B 10) were required during 103.1 h of investigation because of cuff pressure drop and audible air leakage, mainly caused by cuff pressure increases and consequent releases during patient positioning.

Conclusion

Our data demonstrate that the tested cuff pressure release valve was useful and reliable to limit cuff pressure in tracheal intubated children and adolescents within an acceptable pressure range.     

Intra-abdominal Pressure in the Morbidly Obese

Background: Recent data suggests that increased intra-abdominal pressure (IAP) is one factor associated with the morbidity of morbidly obese patients, who have a BMI >35 kg/m². IAP has been proposed to be an abdominal compartment syndrome (ACS). This study investigated the characteristics of IAP in morbidly obese patients. Methods: 45 morbidly obese patients (mean BMI 55±2 kg/m²) had IAP measured using urinary bladder pressure. Results: The mean IAP for the morbidly obese group was 12±0.8 cmH₂O, increased when compared to controls (IAP=0±2 cmH₂O). The IAP correlated to the sagittal abdominal diameter, an index of the degree of central obesity (r=+0.83, P<0.02); however, it did not correlate to basal insulin, body weight, or BMI. The end-expiratory IAP did not change when measured after the laparotomy incision was made, but IAP measured in the last 15 patients increased during the first 2 postoperative days. The IAP for patients with pressure-related morbidity (gastroesophageal reflux disease, hernia, stress incontinence, diabetes, hypertension, and venous insufficiency) was 12±1 cmH₂O, while those without these morbidities had an IAP of 9±0.8 cmH₂O. Conclusion: We conclude that IAP is increased in morbid obesity. This increased IAP is a function of central obesity and is associated with increased morbidity. The degree of IAP elevation correlates with increased co-morbidities. We also conclude that elevation in IAP in morbid obesity is not a true ACS but represents a direct mass effect of the visceral obesity.     

An intra- and interrater reliability and agreement study of vaginal resting pressure,pelvic floor muscle strength,and muscular endurance using a manometer

Introduction and hypothesis

Manometry is commonly used to assess pelvic floor muscle (PFM) function. Aims of the study were to assess intra- and interrater reliability and agreement of vaginal resting pressure, PFM strength, and muscular endurance using a high-precision pressure transducer.

Methods

A convenient sample of 23 women was included. The participants were tested twice by two examiners on day 1 and retested after 1 week by one examiner. Vaginal resting pressure, PFM strength, and muscular endurance were measured by manometer (Camtech AS). Intraclass correlation coefficient (ICC) and Bland–Altman plots were used to analyze reliability and agreement respectively. Results are presented with mean differences (bias) and minimal detectable change.

Results

Twenty participants completed the tests (mean age 55.8 years [27–71], mean parity 1.7 [range 0–3], and mean body mass index 23.7 [range 18.4–27.2, SD 2.4]). ICC values were very good (ICC >0.90) for all measurements. Considerable intervariation of scores, and outliers were seen for measurements representing the highest values. Agreement with mean differences (bias) and minimal detectable change for the intrarater assessment was for vaginal resting pressure: ?2.44?±?8.7 cmH₂O, for PFM strength ?0.22?±?7.6 cmH₂O, and for muscular endurance 0.75?±?59.5 cmH₂O/s. The interrater agreement for vaginal resting pressure was: 1.36?±?9.0 cmH₂O, for PFM strength 2.24?±?9.0 cmH₂O, and for muscular endurance 15.89?±?69.7 cmH₂O/s.

Conclusions

Manometry (Camtech AS) seems less accurate for the strongest women. In clinical practice, significant improvement in PFM variables needs to exceed the minimal detectable change to be above the error of measurement.

     

The influence of ureteral stent on renal pelvic pressure in vivo

The objective of this study was to explore the influence of ureteral stent on renal pelvic pressure by urodynamic study. 41 patients (with unilateral renal and/or ureteral calculi) after minimally invasive percutaneous nephrolithotomy (MPCNL) were placed a 4.7-Fr ureteral stent and 16-Fr nephrostomy tube. Renal pelvic pressure of these patients was measured by urodynamic study at the 5–7 days after MPCNL. Renal pelvic pressure (RPP), intraabdominal pressure (IAP), and vesical pressure (VP) during the filling and voiding phases were detected by urodynamic study with intravesical perfusion. At the baseline, intraabdominal pressure (IAP₀) was 27.52 ± 7.03 cmH₂O, renal pelvic pressure (RPP₀) was 33.07 ± 7.04 cmH₂O; at the maximum cystometric bladder capacity (MCBC) during the filling phase, vesical pressure (VP_vol) was 41.61 ± 10.34 cmH₂O, renal pelvic pressure (RPP_vol) was 39.44 ± 7.33 cmH₂O; at the maximum vesical pressure during the voiding phase, vesical pressure (VP_max) was 74.95 ± 12.79 cmH₂O, renal pelvic pressure (RPP_max) was 65.68 ± 17.03 cmH₂O. (1) There was a strong relationship between RPP₀ and IAP₀ (P = 0.0001); (2) There was statistical significance among RPP₀, RPP_vol and RPP_max (P = 0.0001); (3) RPP was higher than 40 cmH₂O during the voiding phase, and it was obviously relevant to the VP (P = 0.0001) but not to the MCBC (P = 0.2696). RPP increased mildly during the filling phase and dramatically during the voiding phase after stenting. RPP increased higher than the level required for a backflow (40 cmH₂O) during the voiding phase. So it was encouraged to remove the stent at earlier stage or decrease using the ureteral stent if possible.     

Exposure to anaesthetic trace gases during general anaesthesia: CobraPLA vs. LMA classic

Background: To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Methods: Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N₂O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. Results: N₂O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7±7.2 p.p.m. in CobraPLA vs. 4.1±4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16±3 vs. 14±2 cmH₂O, P=0.01). The average leak pressure of the CobraPLA was 24±4 cmH₂O, compared with 20±4 cmH₂O of the LMA classic (P<0.001; all values means±SD). Conclusion: Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N₂O trace concentrations in the anaesthetists' breathing zone.     

The Effect of Patient Position on Leak-Point Pressure Measurements in Women with Genuine Stress Incontinence

The aim of this study was to determine the quantitative and qualitative effects of patient position on coughing and Valsalva leak-point pressure in women with genunie stress incontinence. Thirty-seven patients with genuine stress incontinence and 4 with mixed incontinence underwent multichannel urodynamics using a standardized protocol. Leak-point pressures were performed using 8 Fr microtip catheters placed in the bladder and vagina at a bladder volume of 250 ml in the supine, semirecumbent and standing positions. Urethral pressure profilometry was performed in the semirecumbent position at a bladder volume of 250 ml. The mean (range) age, and median (range) gravidity, parity, body mass index (BMI), and mean (range) Q-tip deflection angle were 61 years (36–80), 3 (1–8), 3 (1–6), 26 (22–30) and 55.8° (25°–80°), respectively. The mean (± standard deviation) Valsalva leak-point pressures in the supine, semirecumbent and standing positions were 82 ± 23, 73 ± 24 and 63 ± 22 cmH₂O, respectively (P<0.001). The mean (± standard deviation) cough leak-point pressures also decreased as the patients were moved from the supine (98 ± 29 cmH₂O) to the semirecumbent (88 ± 24 cmH₂O) and standing positions (77 ± 24 cmH₂O) (P<0.001). The correlation between leak-point pressure and maximum urethral closure pressure was statistically significant and was dependent upon patient position and the provocative maneuver used.     

Titration of Mechanical Insufflation–Exsufflation Optimal Pressure Combinations in Neuromuscular Diseases by Flow/Pressure Waveform Analysis

IntroductionThe aim of this study was to assess several air-pressure settings for MI–E to determine their effect on peak cough flow (PCF), and to compare the best pressures with those are more common used in the literature (±40 cmH₂O) in patients with neuromuscular disorders (NMD).MethodsAdults with NMD in whom MI–E was indicated were recruited. Assisted PCF was measured by an external pneumotachograph. The protocol included 9 PCF measures per patient: 1 baseline (non-assisted), 4 with increasing inspiratory pressures without negative pressure (10, 20, 30 and 40 cmH₂O or maximum tolerated), and then 4 adding expiratory pressures (?10, ?20, ?30 and ?40 cmH₂O or maximum tolerated) with maximum inspiratory pressure previously achieved.ResultsTwenty one patients were included, 61% with amyotrophic lateral sclerosis (ALS). Mean PCFs with recommended pressures (±40 cmH₂O) were lower than the scored in the individualized steps of the titration protocol (197.7 ± 67 l/min vs 214.2 ± 60 l/min, p < 0.05). Regarding subgroups, mean PCF_max values in ALS patients with bulbar symptoms were significantly higher than those achieved with recommended pressures (163.6 ± 80 vs 189 ± 66 l/min, p < 0.05).ConclusionThe PCF_max obtained with the protocol did not always match the recommended settings. It may be advisable to perform MI–E titration assessed by non-invasive PCF monitoring in patients with NMD, especially in ALS with bulbar involvement to improve the therapy detecting airway collapse induced by high pressures.     

The 'ventral urethral elevation plus' sling: a novel approach to treating stress urinary incontinence in men

OBJECTIVE

To evaluate the urodynamic changes after placing a novel ‘ventral urethral elevation plus’ (VUE+) sling (Levera^TM, Caldera Medical, Agoura Hills, CA, USA) in a cadaveric study, and in our initial experience in two patients.

PATIENTS, MATERIALS AND METHODS

In two male cadavers (A and B) the maximum urethral closure pressure (MUCP) and retrograde leak‐point pressure (RLPP) were measured before and after transperineal placement of the Levera sling. A 5.5 × 7 cm sling, with two 1.5 × 22.5 cm inferior extensions and two 1.5 × 25 cm superior extensions, was placed over the bulbar urethra. The inferior extensions were passed using the transobturator approach, and the superior extensions by a prepubic approach. This procedure was offered to two men (C and D) with severe neurogenic intrinsic sphincter deficiency.

RESULTS

The mean baseline MUCP in specimen A was 55 cmH₂O and the RLPP 35 cmH₂O; after placing the sling the respective values increased to 75 and 70 cmH₂O. In specimen B the respective mean values were 56 and 50 cmH₂O, and after placing the sling were 82 and 75 cmH₂O. In patient C, the RLPP increased from 17 cmH₂O before surgery to 65 cmH₂O afterward, and in patient D, from 20 to 70 cmH₂O. At the 12‐month follow‐up, there was complete resolution of urinary incontinence in both patients.

CONCLUSIONS

The VUE+ Levera sling provides urethral compression against the perineal membrane using a straightforward pre‐pubic approach, and ventral elevation and compression of the bulbous urethra using the transobturator approach, avoiding the risks associated with of bone screws and retropubic needle passage. In our initial two patients stress incontinence was cured at 1 year of follow‐up. A long‐ term follow‐up and a larger prospective study of the VUE+ sling is needed to objectively assess the efficacy of this novel procedure.     

两种去神经支配压力性尿失禁模型的比较

目的 比较两种去神经支配压力性尿失禁(SUI)模型的效果.方法 30只雌性Wistar大鼠随机分为3组.测漏尿点压力(LPP),3组分别切断坐骨神经、阴部神经和只游离不切断,术后2周测LPP,行喷嚏试验.术后1月行尿道组织学检查.解剖坐骨、阴部神经.结果 3组术前LPP差异无统计学意义(P>0.05).对照组手术前后LPP分别为(27.567 70±5.434 89)、(30.132 20±5.790 94)cm H_2O,差异无统计学意义(P>0.05);坐骨神经组为(30.911 00±5.467 62)、(30.400 80±5.515 54)cm H_2O,差异无统计学意义(P>0.05);阴部神经组为(27.84930±5.23036)、(9.588 30±2.342 55)cm H_2O,差异有统计学意义(P<0.01).阴部神经组术后喷嚏时漏尿,镜检尿道括约肌萎缩.解剖证明坐骨、阴部神经各自独立,支配尿道括约肌的是阴部神经.结论 切断阴部神经可以建立大鼠去神经支配SUI模型,切断坐骨神经则不能.     

Neuromodulation of bladder activity by stimulation of feline pudendal nerve using a transdermal amplitude modulated signal (TAMS)

Aim: To develop a non‐invasive neuromodulation method to regulate bladder activity. Methods: Neuromodulation of bladder activity was investigated in felines with an intact spinal cord under α‐chloralose anesthesia using a transcutaneous stimulation method with surface electrodes attached to the skin area between the base of the tail and the sciatic notch. Results: The bladder could be either inhibited or excited depending on stimulation frequency and bladder volume. With the bladder distended to induce large amplitude rhythmic isovolumetric bladder contractions, stimulation at a frequency between 5 and 7 Hz significantly suppressed the contractions. Stimulation applied during a cystometrogram (CMG) also increased bladder capacity by 44.3 ± 10.8%. At a frequency between 20 and 40 Hz the inhibitory effect on rhythmic bladder contractions was weak and did not increase bladder capacity during CMG. At low bladder volumes ranging between 60% and 100% of the bladder capacity 20 Hz stimulation‐induced small amplitude (21.2 ± 14.6 cmH₂O) bladder contractions. However, stimulation at 20 Hz induced large amplitude (111.7 ± 22.2 cmH₂O) bladder contractions at a bladder volume about 100–110% of the bladder capacity after the rhythmic bladder contractions were completely inhibited by the inhibitory 5 Hz stimulation. Conclusions: Both inhibitory and excitatory effects on bladder activity can be obtained in cats using the non‐invasive neural stimulation approach. This pre‐clinical study warrants a further clinical trial to investigate the possibility of using this non‐invasive stimulation method to treat incontinence or urinary retention. Neurourol. Urodynam. 30: 1686–1694, 2011. © 2011 Wiley Periodicals, Inc.     

Recruitment and PEEP level influences long‐time aeration in saline‐lavaged piglets: an experimental model

Objectives: To evaluate aeration/ventilation in saline‐lavaged piglets during a 3‐h follow‐up after a recruitment maneuver (RM)/PEEP titration compared with PEEP 10 cmH₂O without a RM. Background: Lung recruitment and PEEP titration are used to find a PEEP preventing repetitive opening/collapsing of lung. Methods: Twenty‐one lung‐lavaged piglets, mean age 7 weeks and mean weight 10 kg; a RM‐group and a PEEP10‐group, were ventilated at PEEP 5 cmH₂O (baseline) followed by zero PEEP ventilation. In the RM‐group, tidal elimination of CO₂ and dynamic compliance (Cdyn) guided recruitment and PEEP titration, respectively. A final 3‐h ventilation followed using PEEP 2 cmH₂O above the first decline of Cdyn and end‐inspiratory pressure (EIP) for a target tidal volume (V_T) of 10 ml·kg^?1. In the PEEP10‐group, PEEP 10 cmH₂O without a RM was used during the final 3‐h ventilation. CT scans and blood gases were repeated every 30 min. Airway pressures, Cdyn and hemodynamics were continuously recorded. Results: Aeration improved without differences between groups. The RM‐group PEEP level of 10 ± 0.6 cmH₂O did not differ from the PEEP10‐group. Compared to baseline EIP was lower in the RM‐group after 3‐h ventilation. In both groups, driving pressure (DP) was lower and Cdyn higher than baseline. In the RM‐group, final EIP and DP were lower and Cdyn higher than in the PEEP10‐group. Conclusions: Both RM/PEEP titration and PEEP elevation resulted in improved aeration without differences between groups at the end point. Lung aeration was achieved at lower EIP and DP and higher Cdyn in the RM‐group than in the PEEP10‐group.     

Changes in fatigability of the striated anal canal after childbirth

Aim Anal manometry is an established assessment tool for patients with faecal incontinence. Fatigue rate index (FRI) has been shown to discriminate between symptomatic patients and controls. The aim of this study was to compare manometry and fatigability of the anal canal in nulliparous women before and after childbirth. Method An air‐filled manometry device was used to record maximum resting and squeeze pressures, fatigue rate (recorded over 20 s) and FRI. Recordings were made before and after vaginal delivery. Results Nineteen women were studied. Resting anal canal pressure was not significantly different before and after delivery (57.1 ± 13.6 vs 51.1 ± 11.9 cmH₂O, P = 0.1). Squeeze pressure was significantly lower postpartum (106.5 ± 43.6 vs 75.5 ± 45.6 cmH₂O, P < 0.001). Fatigue rate was significantly reduced postpartum (?129.5 ± 74.7 vs?76.1 ± 54.8 cmH₂O/min, P = 0.001), but FRI was not significantly altered (1.23 ± 1.49 vs 1.41 ± 1.27 min, P = 0.09). Conclusion Maximal squeeze pressure and fatigue rate of the anal canal are significantly reduced after childbirth. Resting anal canal pressure and FRI are not significantly different.     

In vitro performance and principles of anti-siphoning devices

Background

Anti-siphon devices (ASDs) of various working principles were developed to overcome overdrainage-related complications associated with ventriculoperitoneal shunting.

Objective

We aimed to provide comparative data on the pressure and flow characteristics of six different types of ASDs (gravity-assisted, membrane-controlled, and flow-regulated) in order to achieve a better understanding of these devices and their potential clinical application.

Methods

We analyzed three gravity-dependent ASDs (ShuntAssistant [SA], Miethke; Gravity Compensating Accessory [GCA], Integra; SiphonX [SX], Sophysa), two membrane-controlled ASDs (Anti-Siphon Device [IASD], Integra; Delta Chamber [DC], Medtronic), and one flow-regulated ASD (SiphonGuard [SG], Codman). Defined pressure conditions within a simulated shunt system were generated (differential pressure 10–80 cmH₂O), and the specific flow and pressure characteristics were measured. In addition, the gravity-dependent ASDs were measured in defined spatial positions (0–90°).

Results

The flow characteristics of the three gravity-assisted ASDs were largely dependent upon differential pressure and on their spatial position. All three devices were able to reduce the siphoning effect, but each to a different extent (flow at inflow pressure: 10 cmH₂O, siphoning -20 cmH₂O at 0°/90°: SA, 7.1?±?1.2*/2.3?±? 0.5* ml/min; GCA, 10.5?±?0.8/3.4?±?0.4* ml/min; SX, 9.5?±?1.2*/4.7?±?1.9* ml/min, compared to control, 11.1?±?0.4 ml/min [*p?2O/ siphoning -20cmH₂O: DC, 2.6?±?0.1/ 4?±?0.3* ml/min; IASD, 2.5?±?0.2/ 0.8?±?0.4* ml/min; SG, 0.8?±?0.2*/ 0.2?±?0.1* ml/min [*p?Conclusion The tested ASDs were able to control the siphoning effect within a simulated shunt system to differing degrees. Future comparative trials are needed to determine the type of device that is superior for clinical application.     

Oxygen Transport and Venous Admixture in the Extremely Obese. Influence of Anaesthesia and Artificial Ventilation with and without Positive End-Expiratory Pressure

Eight extremely obese patients (mean weight 136 kg) were studied when awake and breathing air, and during anaesthesia with controlled ventilation (oxygen fraction in inspirate (Fi o₂): 0.5). During anaesthesia, the patients were first studied with zero end-expiratory pressure (ZEEP) ventilation. Then two different positive end-expiratory pressures (PEEP) were applied, 10 cmH₂O and 15 cmH₂O₂ in order to study the effect of an increase in functional residual capacity (FRC). Arterial oxygenation and oxygen availability, as well as cardiac output (Q_t) and venous admixture (Q_s/Q_t) were studied. With the institution of anaesthesia and ZEEP, the alveolar arterial oxygen tension difference (P(A-a)o₂) rose from 3.5 ± 1.1 to 28.4 ± 2.6 kPa, and the oxygen availability fell from 1346 ± 222 to 1039 ± 239 ml/min, due to the additive effect of an increase in Q_s/Q_t from 10 ± 4 to 21 ± 5% and a fall in Q_T, from 7.7 ± 1.2 to 5.5 ± 1.1 l/min. With increasing levels of PEEP, despite a fall in P(A-a)o₂, there was a reduction in oxygen availability. This was due to simultaneous reduction in Q_s/Q_t and Q_T. At a PEEP of 15cmH₂O, the P(A-a)o₂ was 21.2 ± 7.1 kPa, oxygen availability 862 ± 170 ml/min, Q_s/Q_t 13 ± 4 and Q_T 4.4 ± 0.6 I. It is concluded that PEEP ventilation significantly reduces Q_s/Q_t in extremely obese patients during anaesthesia and should be used in these patients if there is arterial hypoxemia despite a high Fi o₂     

Physiological effects of a lung-recruiting strategy applied during one-lung ventilation

Background: One‐lung ventilation (OLV) affects respiratory mechanics and ventilation/perfusion matching, reducing functional residual capacity of the ventilated lung. While the application of a lung‐recruiting manoeuvre (RM) on the ventilated lung has been shown to improve oxygenation, data regarding the impact of RM on respiratory mechanics are not available. Methods: Thirteen patients undergoing lung resection in lateral decubitus were studied. During OLV, a lung‐recruiting strategy consisting in a RM lasting 1 min followed by the application of positive end‐expiratory pressure 5 cmH₂O was applied to the ventilated lung. Haemodynamics, gas exchange and respiratory mechanics parameters were recorded on two‐lung ventilation (TLV_baseline), OLV before and 20 min after the RM (OLV_pre‐RM, OLV_post‐RM, respectively) and TLV_end. Haemodynamics parameters were also recorded during the RM. Results: The PaO₂/FiO₂ ratio was 358±126 on TLV_baseline; it decreased to 235±113 on OLV_pre‐RM (P<0.01) increased to 351±120 on OLV_post‐RM (P<0.01 vs. OLV_pre‐RM), and remain stable thereafter. During the RM, CI decreased from 3.04±0.7 l/m² OLV_pre‐RM to 2.4±0.6 l/m² (P<0.05), and returned to baseline on OLV_post‐RM (3.1±0.7 l/m², NS vs. OLV_pre‐RM). The RM resulted in alveolar recruitment and caused a significant decrease in static elastance of the dependent lung (16.6±8.9 cmH₂O/ml OLV_post‐RM vs. 22.3±8.1 cmH₂O/ml OLV_pre‐RM) (P<0.01). Conclusions: During OLV in lateral decubitus for thoracic surgery, application to the dependent lung a recruiting strategy significantly recruits the dependent lung, improving arterial oxygenation and respiratory mechanics until the end of surgery. However, the transient haemodynamic derangement occurring during the RM should be taken into account.