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1.  Relationship between intra-abdominal pressure and indocyanine green plasma disappearance rate: hepatic perfusion may be impaired in critically ill patients with intra-abdominal hypertension 
Annals of Intensive Care  2012;2(Suppl 1):S19.
Monitoring hepatic blood flow and function might be crucial in treating critically ill patients. Intra-abdominal hypertension is associated with decreased abdominal blood flow, organ dysfunction, and increased mortality. The plasma disappearance rate (PDR) of indocyanine green (ICG) is considered to be a compound marker for hepatosplanchnic perfusion and hepatocellular membrane transport and correlates well with survival in critically ill patients. However, correlation between PDRICG and intra-abdominal pressure (IAP) remains poorly understood. The aim of this retrospective study was to investigate the correlation between PDRICG and classic liver laboratory parameters, IAP and abdominal perfusion pressure (APP). The secondary goal was to evaluate IAP, APP, and PDRICG as prognostic factors for mortality.
A total of 182 paired IAP and PDRICG measurements were performed in 40 critically ill patients. The mean values per patient were used for comparison. The IAP was measured using either a balloon-tipped stomach catheter connected to an IAP monitor (Spiegelberg, Hamburg, Germany, or CiMON, Pulsion Medical Systems, Munich, Germany) or a bladder FoleyManometer (Holtech Medical, Charlottenlund, Denmark). PDRICG was measured at the bedside using the LiMON device (Pulsion Medical Systems, Munich, Germany). Primary endpoint was hospital mortality.
There was no significant correlation between PDRICG and classic liver laboratory parameters, but PDRICG did correlate significantly with APP (R = 0.62) and was inversely correlated with IAP (R = -0.52). Changes in PDRICG were associated with significant concomitant changes in APP (R = 0.73) and opposite changes in IAP (R = 0.61). The IAP was significantly higher (14.6 ± 4.6 vs. 11.1 ± 5.3 mmHg, p = 0.03), and PDRICG (10 ± 8.3 vs. 15.9 ± 5.2%, p = 0.02) and APP (43.6 ± 9 vs. 57.9 ± 12.2 mmHg, p < 0.0001) were significantly lower in non-survivors.
PDRICG is positively correlated to APP and inversely correlated to IAP. Changes in APP are associated with significant concomitant changes in PDRICG, while changes in IAP are associated with opposite changes in PDRICG, suggesting that an increase in IAP may compromise hepatosplanchnic perfusion. Both PDRICG and IAP are correlated with outcome. Measurement of PDRICG may be a useful additional clinical tool to assess the negative effects of increased IAP on liver perfusion and function.
PMCID: PMC3527154  PMID: 23282242
2.  The effect of body position on compartmental intra-abdominal pressure following liver transplantation 
Annals of Intensive Care  2012;2(Suppl 1):S12.
Current assumptions rely on intra-abdominal pressure (IAP) being uniform across the abdominal cavity. The abdominal contents are, however, a heterogeneous mix of solid, liquid and gas, and pressure transmission may not be uniform. The current study examines the upper and lower IAP following liver transplantation.
IAP was measured directly via intra-peritoneal catheters placed at the liver and outside the bladder. Compartmental pressure data were recorded at 10-min intervals for up to 72 h following surgery, and the effect of intermittent posture change on compartmental pressures was also studied. Pelvic intra-peritoneal pressure was compared to intra-bladder pressure measured via a FoleyManometer.
A significant variation in upper and lower IAP of 18% was observed with a range of differences of 0 to 16 mmHg. A sustained difference in inter-compartmental pressure of 4 mmHg or more was present for 23% of the study time. Head-up positioning at 30° provided a protective effect on upper intra-abdominal pressure, resulting in a significant reduction in all patients. There was excellent agreement between intra-bladder and pelvic pressure.
A clinically significant variation in inter-compartmental pressure exists following liver transplantation, which can be manipulated by changes to body position. The existence of regional pressure differences suggests that IAP monitoring at the bladder alone may under-diagnose intra-abdominal hypertension and abdominal compartment syndrome in these patients. The upper and lower abdomen may need to be considered as separate entities in certain conditions.
PMCID: PMC3390292  PMID: 22873413
intra-abdominal pressure; abdominal compartment syndrome; intra-abdominal hypertension; liver transplantation; regional pressure variation
3.  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 r2 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.
PMCID: PMC3953861  PMID: 24701411
Intra-abdominal pressure; Gastric pressure; Bladder pressure; Intra-abdominal hypertension; Hernia; Oxygenation; Respiratory function
4.  Effects of intra-abdominal pressure on liver function assessed with the LiMON in critically ill patients 
Canadian Journal of Surgery  2011;54(3):161-166.
Intra-abdominal pressure (IAP) and intra-abdominal hypertension (IAH) are associated with significant morbidity and mortality in critically ill patients. Our aim was to assess the effects of IAH on liver function using the noninvasive liver function monitoring system LiMON and to assess the prognostic value of IAP in critically ill patients.
We conducted a retrospective analysis of critically ill patients who were treated in the intensive care unit (ICU). The IAP and indocyanine green plasma disappearance rate (ICG-PDR) measurements were made within 24 hours after admission to the ICU and repeated 12 hours later. Intra-abdominal pressure was measured via a Foley bladder catheter, and ICG elimination tests were conducted concurrently using the LiMON.
We included 30 critically ill patients (17 women and 13 men aged 28–89 yr) in our analysis. Statistical analysis showed that the baseline IAP values were significantly higher among nonsurvivors than survivors (19.38 [standard deviation; SD 2.08] v. 13.07 [SD 0.99]). The twelfth-hour IAP values were higher than baseline measurements among nonsurvivors (21.50 [SD 1.96]) and lower than baseline measurements among survivors (11.71 [SD 1.54]); the difference between groups was significant (p < 0.001). The baseline ICG-PDR values were significantly lower among nonsurvivors than survivors (10.86 [SD 3.35] v. 24.51 [SD 6.78]), and the twelfth-hour ICG-PDR values were decreased in all groups; the difference between groups was significant (p < 0.001).
Our results suggest that measurement of ICG-PDR with the LiMON is a good predictor of the effects of IAP on liver function and, thus, can be recommended for the evaluation of critically ill patients.
PMCID: PMC3104306  PMID: 21443832
5.  Are Standard Intra-Abdominal Pressure Values Different during Pregnancy? 
PLoS ONE  2013;8(10):e77324.
Measurement of intra-abdominal pressure (IAP) is an important parameter in the surveillance of intensive care unit patients. Standard values of IAP during pregnancy have not been well defined. The aim of this study was to assess IAP values in pregnant women before and after cesarean delivery.
This prospective study, carried out from January to December 2011 in a French tertiary care centre, included women with an uneventful pregnancy undergoing elective cesarean delivery at term. IAP was measured through a Foley catheter inserted in the bladder under spinal anaesthesia before cesarean delivery, and every 30 minutes during the first two hours in the immediate postoperative period.
The study included 70 women. Mean IAP before cesarean delivery was 14.2 mmHg (95%CI: 6.3–23). This value was significantly higher than in the postoperative period: 11.5 mmHg (95%CI: 5–19.7) for the first measurement (p = 0.002). IAP did not significantly change during the following two postoperative hours (p = 0.2). Obese patients (n = 25) had a preoperative IAP value significantly higher than non-obese patients: 15.7 vs. 12.4; p = 0.02.
In term pregnancies, IAP values are significantly higher before delivery than in the post-partum period, where IAP values remain elevated for at least two hours at the level of postoperative classical abdominal surgery. The knowledge of these physiological changes in IAP values may help prevent organ dysfunction/failure when abdominal compartment syndrome occurs after cesarean delivery.
PMCID: PMC3808400  PMID: 24204808
6.  The Relation between Postvoid Residual and Occurrence of Urinary Tract Infection after Stroke in Rehabilitation Unit 
Annals of Rehabilitation Medicine  2012;36(2):248-253.
To determine the relation between postvoid residual (PVR) and the occurrence of urinary tract infection (UTI) in stroke patients.
One hundred and eighty-eight stroke patients who were admitted to an inpatient rehabilitation unit and who did not have UTI on admission (105 males, 83 females, mean age 67.1 years) were included in this study. The PVR was measured 3 times within 72 hours after admission. Mean PVR, demographic variables, K-MMSE (Korean Mini-Mental State Examination), initial K-MBI (Korean Modified Barthel Index), Foley catheter indwelling time and stroke type were defined and the relation to the occurrence of UTI was analyzed.
UTI occurred in 74 patients (39.4%) during admission to the rehabilitation unit. There were significant differences between the UTI and non-UTI groups in K-MMSE, K-MBI, Foley catheter indwelling time (p<0.01). However, age, gender, stroke location and type were not associated. The occurrence of UTI was 4.87 times higher in the patients with a mean PVR over 100 ml than in those with a mean PVR <100 ml. The mean PVR was 106.5 ml in the UTI group, while it was 62.7 ml in the non-UTI group (p<0.01). PVR was not associated with age.
The UTI rate is higher when the mean PVR is over 100 ml irrespective of gender and age. Close monitoring of PVR and appropriate intervention is needed to reduce the occurrence of UTI in stroke patients.
PMCID: PMC3358682  PMID: 22639750
Urinary tract infection; Postvoid residual; Stroke
7.  Long catheter sign: a reliable bedside sign of incorrect positioning of foley catheter in male spinal cord injury patients 
Cases Journal  2008;1:43.
Indwelling urethral catheter is often used in male spinal cord injury patients to provide drainage to neuropathic bladder. If the balloon of a Foley catheter is inflated in urethra or, when a properly inserted Foley catheter is later pulled and thereby, the Foley balloon comes to lie in urethra, an excessive length of catheter will remain outside the penis. This sign is termed "long catheter sign". Long catheter sign will also be positive when Foley catheter slips out of urinary bladder in situations where Foley balloon is ruptured by a spiky vesical calculus or deflated due to a defective valve.
Case Presentation
A fifty-year-old Caucasian male with paraplegia at T-5 level had been managing neuropathic bladder by long-term indwelling urethral catheter. During his stay in spinal unit, the patient felt that there had been a tug on the drainage tube when he was being turned during night as part of the routine care for relief of pressure. Next morning, a health professional noticed that a long segment of catheter was lying outside penis. There was no bleeding from urethral meatus. Catheter continued to drain urine, which was yellowish in colour. Urine output was satisfactory. This patient did not develop any clinical feature of autonomic dysreflexia nor was he feeling unwell. In view of positive long catheter sign, radiological studies were performed to check the position of Foley catheter, which confirmed the clinical impression of incorrectly positioned Foley catheter. The catheter was removed; flexible cystoscopy was performed. A 16 Fr, 20 ml balloon Foley catheter was inserted over a 0.032" guide wire. Following this procedure, a considerably shorter length of Foley catheter remained outside the penis.
Positive long catheter sign indicates that the Foley catheter is placed incorrectly and needs repositioning urgently. Prompt recognition of long catheter sign and immediate repositioning of Foley catheter will help to prevent complications such as chronic distension of urinary bladder, urine infection, and pressure necrosis of urethra especially if Foley balloon remains inflated within urethra for a long period. In this patient, use of a Foley catheter with 20 ml balloon, and securing the drainage tube to thigh with two straps, helped to prevent inadvertent pull of Foley balloon into the urethra.
PMCID: PMC2488320  PMID: 18637181
8.  Abdominal compartment syndrome in patients with severe acute pancreatitis in early stage 
AIM: To study retrospectively the influence of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) in patients with early acute pancreatitis (AP) (during the first week after admission) on physiological functions, and the association of the presence of IAH/ACS and outcome.
METHODS: Patients (n = 74) with AP recruited in this study were divided into two groups according to intra-abdominal pressure (IAP) determined by indirect measurement using the transvesical route via Foley bladder catheter during the first week after admission. Patients (n = 44) with IAP ≥ 12 mmHg were assigned in IAH group, and the remaining patients (n = 30) with IAP < 12 mmHg in normal IAP group. For analysis of the influence of IAH/ACS on organ function and outcome, the physiological parameters and the occurrence of organ dysfunction during intensive care unit (ICU) stay were recorded, as were the incidences of pancreatic infection and in-hospital mortality.
RESULTS: IAH within the first week after admission was found in 44 patients (59.46%). Although the APACHE II scores on admission and the Ranson scores within 48 h after hospitalization were elevated in IAH patients in early stage, they did not show the statistically significant differences from patients with normal IAP within a week after admission (16.18 ± 3.90 vs 15.70 ± 4.25, P = 0.616; 3.70 ± 0.93 vs 3.47 ± 0.94, P = 0.285, respectively). ACS in early AP was recorded in 20 patients (27.03%). During any 24-h period of the first week after admission, the recorded mean IAP correlated significantly with the Marshall score calculated at the same time interval in IAH group (r = 0.635, P < 0.001). Although ACS patients had obvious amelioration in physiological variables within 24 h after decompression, the incidences of pancreatitic infection, septic shock, multiple organ dysfunction syndrome (MODS) and death in the patients with ACS were significantly higher than that in other patients without ACS (pancreatitic infection: 60.0% vs 7.4%, P < 0.001; septic shock: 70.0% vs 11.1%, P < 0.001; MODS: 90.0% vs 31.5%, P < 0.001; mortality: 75.0% vs 3.7%, P < 0.001).
CONCLUSION: IAH/ACS is a frequent finding in patients admitted to the ICU because of AP. Patients with IAP at approximately 10-12 mmHg and early signs of changes in physiologic variables should be seriously considered for urgent decompression to improve survival.
PMCID: PMC2716618  PMID: 18567084
Acute pancreatitis; Abdominal compartment syndrome; Intra-abdominal pressure; Intra-abdominal hypertension; Organ dysfunction
9.  Evaluation of the Colin STBP-680 at rest and during exercise: an automated blood pressure monitor using R-wave gating. 
The application of automated blood pressure measurement during exercise has been limited by inaccuracies introduced by the effects of accompanying motion and noise. We evaluated a newly developed automated blood pressure monitor for measuring exercise blood pressure (Colin STBP-680; Colin, San Antonio, Texas, USA). The STBP-680 uses acoustic transduction with the assistance of the electrocardiogram R-wave to trigger the sampling period for blood pressure measurement. The automated monitor readings were compared with simultaneous technician mercury sphygmomanometric readings in the same arm. Blood pressure was measured in 18 men at rest and during exercise at 40% VO2 peak, (low intensity), 70% VO2 peak (moderate intensity) and VO2 peak (high intensity) on the cycle ergometer. Mean(s.d.) systolic blood pressure difference between the automated monitor and mercury manometer readings at rest and during exercise at low, moderate and high work intensities were 3(0) mmHg, 3(2) mmHg, 1(1) mmHg, and 0(11) mmHg respectively (analysis of variance; P > 0.05). Resting diastolic blood pressure obtained with the STBP-680 was similar to the mercury manometer readings (78(10) versus 81(7) mmHg (P > 0.05). Exercise diastolic pressure at the low level of work intensity was almost identical between the automated monitor and mercury manometer readings (64(8) versus 65(10) mmHg (not significant)). Diastolic blood pressure readings between the STBP-680 and mercury manometer showed a greater difference at the moderate and high workloads (11 mmHg and 9 mmHg, respectively), but this difference was not significant (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
PMCID: PMC1332130  PMID: 8358579
10.  Sensitivity of Transcranial Doppler Versus Intracardiac Echocardiography in the Detection of Right-to-Left Shunt 
JACC. Cardiovascular imaging  2010;3(4):343-348.
The purpose of this study was to understand the reason for variation in the sensitivity of different methods of detecting right-to-left shunts (RLS).
Patent foramen ovale (PFO) is implicated in the pathogenesis of cryptogenic stroke, decompression illness, and migraine headaches. Intravenous agitated saline injections with tomographic imaging (transthoracic, transesophageal, and intracardiac echocardiography) has been used for detecting intracardiac shunts. Some patients with a high clinical suspicion of PFO have inconclusive echocardiographic study results. Transcranial Doppler (TCD) is an alternative method for detecting RLS that is not dependent on tomographic imaging.
Thirty-eight consecutive patients who were undergoing PFO closure had simultaneous transcranial Doppler and intracardiac echocardiography performed. Agitated saline injections were performed at rest, with Valsalva maneuver, and with forced expiration into a manometer to 40 mm Hg before and after closure, as well as 3 or more months after closure. Right atrial pressures were measured in the periprocedural period, and RLS were graded according to standard methods during these maneuvers.
Right atrial pressures were significantly higher with Valsalva maneuver compared with rest (before closure 21.6 ± 11.9 mm Hg vs. 6.6 ± 2.6 mm Hg, p < 0.001; after closure 28.4 ± 13.9 mm Hg vs. 6.8 ± 2.6 mm Hg, p < 0.001) and with manometer compared with Valsalva maneuver (before closure 38.7 ± 6.6 mm Hg vs. 21.6 ± 11.9 mm Hg, p < 0.001; after closure 44.0 ± 9.5 mm Hg vs. 28.4 ± 13.9 mm Hg, p < 0.001). Intracardiac echocardiography underestimated shunting in 34% of patients with Valsalva maneuver or manometer after closure compared with TCD.
Transcranial Doppler with immediate feedback provided by forced expiration against a manometer to 40 mm Hg is more sensitive than echocardiographic imaging for the detection of RLS. These observations have significant implications for determining the incidence of RLS in patients with stroke or migraine.
PMCID: PMC3951441  PMID: 20394894
patent foramen ovale; transcranial Doppler; stroke
11.  Effect of bladder volume on measured intravesical pressure: a prospective cohort study 
Critical Care  2006;10(4):R98.
Correct bedside measurement of intra-abdominal pressure (IAP) is important. The bladder method is considered as the gold standard for indirect IAP measurement, but the instillation volumes reported in the literature vary substantially. The aim of this study was to evaluate the effect of instillation volume on intra-bladder pressure (IBP) as an estimation for IAP in critically ill patients.
In this prospective cohort study in 13 sedated and mechanically ventilated patients, we used a revised closed system repeated measurement technique for measurement of IBP. After the system was flushed, IBP was measured with 25 ml increments up to 300 ml. The absolute bias for each volume was calculated as IBP at a given volume minus IBP at zero volume.
In total, 30 measurement sets were performed (mean 2.3 per patient). The median IBP at 25 ml was already significantly higher than IBP at zero volume (7.5 versus 6 mmHg). There was no correlation between IBP at zero volume and absolute IBP bias at any bladder volume. Median absolute IBP bias was 1.5 mmHg at 50 ml; 2.5 mmHg at 100 ml; 5.5 mmHg at 150 ml; and up to 11 mmHg at 300 ml.
Larger instillation volumes than the usually recommended 50 ml to estimate IAP by bladder pressure may cause clinically relevant overestimation of IAP. Small volumes to a maximum of 25 ml, enough to create a fluid column and to remove air, may be sufficient.
PMCID: PMC1750998  PMID: 16934130
12.  Early recognition of abdominal compartment syndrome in patients with acute pancreatitis 
AIM: To assess the value of widely used clinical scores in the early identification of acute pancreatitis (AP) patients who are likely to suffer from intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS).
METHODS: Patients (n = 44) with AP recruited in this study were divided into two groups (ACS and non-ACS) according to intra-abdominal pressure (IAP) determined by indirect measurement using the transvesical route via Foley bladder catheter. On admission and at regular intervals, the severity of the AP and presence of organ dysfunction were assessed utilizing different multifactorial prognostic systems: Glasgow-Imrie score, Acute Physiology and Chronic Health Evaluation II (APACHE-II) score, and Multiorgan Dysfunction Score (MODS). The diagnostic performance of scores predicting ACS development, cut-off values and specificity and sensitivity were established using receiver operating characteristic (ROC) curve analysis.
RESULTS: The incidence of ACS in our study population was 19.35%. IAP at admission in the ACS group was 22.0 (18.5-25.0) mmHg and 9.25 (3.0-12.4) mmHg in the non-ACS group (P < 0.01). Univariate statistical analysis revealed that patients in the ACS group had significantly higher multifactorial clinical scores (APACHE II, Glasgow-Imrie and MODS) on admission and higher maximal scores during hospitalization (P < 0.01). ROC curve analysis revealed that APACHE II, Glasgow-Imrie, and MODS are valuable tools for early prediction of ACS with high sensitivity and specificity, and that cut-off values are similar to those used for stratification of patients with severe acute pancreatitis (SAP).
CONCLUSION: IAH and ACS are rare findings in patients with mild AP. Based on the results of our study we recommend measuring the IAP in cases when patients present with SAP (APACHE II > 7; MODS > 2 or Glasgow-Imrie score > 3).
PMCID: PMC2653440  PMID: 19222096
Acute pancreatitis; Abdominal compartment syndrome; Intra-abdominal pressure; Intra-abdominal hypertension; Organ dysfunction
13.  Effects of Treatment on the Mortality Rate in Septicaemia 
British Medical Journal  1969;2(5653):338-341.
The results of treatment have been analysed in 173 patients with septicaemia during 1962–8. Between 1962 and 1965 various antibiotics were used, and shock was treated with vasopressor agents. Between 1966 and 1968 kanamycin was given initially, and shock was treated with corticosteroids and with intravenous fluid therapy monitored with a central venous pressure manometer.
The mortality rate in 1966–8 fell to half that of the earlier period in patients with Gram-negative infections, and in those with shock. The reduced mortality in the latter was clearly associated with the use of a central venous manometer to control intravenous fluid therapy, though whether the reduction resulted from specific improvement in intravenous therapy or from the necessary closer observation of the patient is not clear. Staphylococcal septicaemia was common during both periods, and its mortality rate did not fall; hence methicillin together with kanamycin is now given initially in all cases.
PMCID: PMC1983278  PMID: 5768457
14.  Endotracheal tube cuff pressure in three hospitals, and the volume required to produce an appropriate cuff pressure 
BMC Anesthesiology  2004;4:8.
Cuff pressure in endotracheal (ET) tubes should be in the range of 20–30 cm H2O. We tested the hypothesis that the tube cuff is inadequately inflated when manometers are not used.
With IRB approval, we studied 93 patients under general anesthesia with an ET tube in place in one teaching and two private hospitals. Anesthetists were blinded to study purpose. Cuff pressure in tube sizes 7.0 to 8.5 mm was evaluated 60 min after induction of general anesthesia using a manometer connected to the cuff pilot balloon. Nitrous oxide was disallowed. After deflating the cuff, we reinflated it in 0.5-ml increments until pressure was 20 cmH2O.
Neither patient morphometrics, institution, experience of anesthesia provider, nor tube size influenced measured cuff pressure (35.3 ± 21.6 cmH2O). Only 27% of pressures were within 20–30 cmH2O; 27% exceeded 40 cmH2O. Although it varied considerably, the amount of air required to achieve a cuff pressure of 20 cmH2O was similar with each tube size.
We recommend that ET cuff pressure be set and monitored with a manometer.
PMCID: PMC535565  PMID: 15569386
15.  Endotracheal tube cuff pressure assessment maneuver induces drop of expired tidal volume in the postoperative of coronary artery bypass grafting 
Previous investigations reported that the cuff pressure (CP) can decrease secondary to the CP evaluation itself. However is not established in literature if this loss of CP is able to generate alterations on expired tidal volume (ETV). Therefore, the aim of this study was to evaluate the potential consequences of the endotracheal CP assessment maneuver on CP levels and ETV in the early postoperative of coronary artery bypass grafting (CABG).
A total of 488 patients were analyzed. After the operation, the lungs were ventilated in pressure-assist-control mode and the same ventilatory settings were adjusted for all patients. After intensive care unit arrival, the cuff was fully deflated and then progressively inflated by air injection, to promote a minimal volume to occlude the trachea. To assist the cuff inflation and the air leakage identification, the graphical monitoring of the volume-time curve was adopted. After 20 minutes a first cuff pressure evaluation was performed (P1) and a second measurement (P2) was taken after 20 minutes with an analog manometer. ETV was obtained always pre and post P1 measurement.
The CP assessment maneuver promoted a significant drop of P2 in relation to P1 when the manometer was attached to the pilot balloon (p < 0.0001). When compared the moments, pre-P1 versus post-P1, a significant drop of the ETV was also observed (p < 0.0001).
The CP assessment maneuver promoted a significant decrease in CP values and occurrence of air leakage with reduction of ETV in the early postoperative of CABG.
PMCID: PMC3403938  PMID: 22681781
Coronary artery bypass grafting; Endotracheal tube cuff pressure; Air leakage; Expired tidal volume; Mechanical ventilation
16.  Study on a Concentric Tube Bulb Manometer and its Performance Compared to U-shaped Manometer 
Sensors (Basel, Switzerland)  2007;7(11):2835-2845.
This paper presents comparative study of a new type of manometer called concentric tube bulb (C.T.B) manometer. Its performance of measuring differential height is studied against conventional U-shaped manometer. Pressure drops and mass flow rates are calculated by taking various systems comprising of different flow measuring devices such as orifice and venturimeters using both U- shaped and C.T.B manometers. Comparison between the physically measured values of differential pressure drops and mass flow rates with the calculated values based on theoretical equations is also made. Experiments are carried out using mercury and CCl4 in these manometers as sensing fluids. Water is used as flowing fluid for mass flow rate and pressure drop measurements, whereas in gauge pressure measurements air is used.
PMCID: PMC3965241
Comparative study; Differential height; Concentric tube bulb manometer; Mass flow rates; Sensing fluids
17.  Intra-abdominal pressure in severe acute pancreatitis 
Hospital mortality in patients with severe acute pancreatitis (SAP) remains high. Some of these patients develop increased intra-abdominal pressure (IAP) which may contribute to organ dysfunction. The aims of this study were to evaluate the frequency of increased IAP in patients with SAP and to assess the development of organ dysfunction and factors associated with high IAP.
During 2001–2003 a total of 59 patients with severe acute pancreatitis were treated in the intensive care unit (ICU) of Helsinki University Hospital. IAP was measured by the intravesical route in 37 patients with SAP. Data from these patients were retrospectively reviewed.
Maximal IAP, APACHE II score, maximal SOFA score, maximal creatinine, age and maximal lactate were significantly higher in nonsurvivors. There was a significant correlation of the maximal IAP with the maximal SOFA, APACHE II, maximal creatinine, maximal lactate, base deficit and ICU length of stay. Patients were divided into quartiles according to the maximal IAP. Maximal IAP was 7–14, 15–18, 19–24 and 25–33 mmHg and the hospital mortality rate 10%, 12.5%, 22.2% and 50% in groups 1–4, respectively. A statistically significant difference was seen in the maximal SOFA, ICU length of stay, maximal creatinine and lactate values. The mean ICU-free days in groups 1–4 were 45.7, 38.8, 32.0 and 27.5 days, respectively. The difference between groups 1 and 4 was statistically significant.
In patients with SAP, increased IAP is associated with development of early organ failure reflected in increased mortality and fewer ICU-free days. Frequent measurement of IAP during intensive care is important in optimizing abdominal perfusion pressure and recognizing patients potentially benefitting from decompressive laparotomy.
PMCID: PMC1800837  PMID: 17227591
18.  Neonatal resuscitation 3: manometer use in a model of face mask ventilation 
Background: Adequate ventilation is the key to successful neonatal resuscitation. Positive pressure ventilation (PPV) is initiated with manual ventilation devices via face masks. These devices may be used with a manometer to measure airway pressures delivered. The expiratory tidal volume measured at the mask (VTE(mask)) is a good estimate of the tidal volume delivered during simulated neonatal resuscitation.
Aim: To assess the effect of viewing a manometer on the peak inspiratory pressures used, the volume delivered, and leakage from the face mask during PPV with two manual ventilation devices in a model of neonatal resuscitation.
Methods: Participants gave PPV to a modified resuscitation mannequin using a Laerdal infant resuscitator and a Neopuff infant resuscitator at specified pressures ensuring adequate chest wall excursion. Each participant gave PPV to the mannequin with each device twice, viewing the manometer on one occasion and unable to see the manometer on the other. Data from participants were averaged for each device used with the manometer and without the manometer separately.
Results: A total of 7767 inflations delivered by the 18 participants were recorded and analysed. Peak inspiratory pressures delivered were lower with the Laerdal device. There were no differences in leakage from the face mask or volumes delivered. Whether or not the manometer was visible made no difference to any measured variable.
Conclusions: Viewing a manometer during PPV in this model of neonatal resuscitation does not affect the airway pressure or tidal volumes delivered or the degree of leakage from the face mask.
PMCID: PMC1721943  PMID: 15871988
19.  The Effect of Intra-Abdominal Hypertension Incorporating Severe Acute Pancreatitis in a Porcine Model 
PLoS ONE  2012;7(3):e33125.
Abdominal compartment syndrome (ACS) and intra abdominal hypertension(IAH) are common clinical findings in patients with severe acute pancreatitis(SAP). It is thought that an increased intra abdominal pressure(IAP) is associated with poor prognosis in SAP patients. But the detailed effect of IAH/ACS on different organ system is not clear. The aim of this study was to assess the effect of SAP combined with IAH on hemodynamics, systemic oxygenation, and organ damage in a 12 h lasting porcine model.
Measurements and Methods
Following baseline registrations, a total of 30 animals were divided into 5 groups (6 animals in each group): SAP+IAP30 group, SAP+IAP20 group, SAP group, IAP30 group(sham-operated but without SAP) and sham-operated group. We used a N2 pneumoperitoneum to induce different levels of IAH and retrograde intra-ductal infusion of sodium taurocholate to induce SAP. The investigation period was 12 h. Hemodynamic parameters (CO, HR, MAP, CVP), urine output, oxygenation parameters(e.g., SvO2, PO2, PaCO2), peak inspiratory pressure, as well as serum parameters (e.g., ALT, amylase, lactate, creatinine) were recorded. Histological examination of liver, intestine, pancreas, and lung was performed.
Main Results
Cardiac output significantly decreased in the SAP+IAH animals compared with other groups. Furthermore, AST, creatinine, SUN and lactate showed similar increasing tendency paralleled with profoundly decrease in SvO2. The histopathological analyses also revealed higher grade injury of liver, intestine, pancreas and lung in the SAP+IAH groups. However, few differences were found between the two SAP+IAH groups with different levels of IAP.
Our newly developed porcine SAP+IAH model demonstrated that there were remarkable effects on global hemodynamics, oxygenation and organ function in response to sustained IAH of 12 h combined with SAP. Moreover, our model should be helpful to study the mechanisms of IAH/ACS-induced exacerbation and to optimize the treatment strategies for counteracting the development of organ dysfunction.
PMCID: PMC3293917  PMID: 22403734
20.  Intraocular pressure measurement at the choroid surface: a feasibility study with implications for implantable microsystems 
AIMS—To demonstrate that a sensor, which is inserted through the sclera and placed in intimate contact with the choroid, can reliably detect changes in the intraocular pressure (IOP).
METHODS—A manometer was used to control the IOP of three cadaver eyes in steps of 7 mm Hg. A piezoresistive pressure sensor was used to measure the pressure at the choroid through a 2.5 mm diameter hole that was surgically removed from the sclera. Data were collected for two configurations; with the sensor: (i) rigidly attached to a miniature positioning stage, and (ii) sutured to the sclera.
RESULTS—Both configurations accurately tracked the manometer pressure from 10 mm Hg to 47 mm Hg. For the fixed sensor cases, the average difference between the pressure measured at the choroid and in the anterior chamber was 0.8 mm Hg for the three eyes. For the sutured sensor case, the average difference was 2.1 mm Hg—although a significant portion of this was attributed to an initial offset. The standard deviations at each pressure level for all of the choroid measurements were under 1.0 mm Hg.
CONCLUSIONS—Small changes in IOP can be accurately measured by a sensor in contact with the surface of the choroid, for both a fixed sensor configuration and for a sensor sutured to the sclera. These results are the first step in the realisation of a surgically implantable microsensor to monitor IOP for patients suffering from low tension and other difficult to manage forms of glaucoma.

PMCID: PMC1724025  PMID: 11423464
21.  Effects of zero reference position on bladder pressure measurements: an observational study 
Annals of Intensive Care  2012;2(Suppl 1):S13.
Although the World Society for Abdominal Compartment Syndrome in its guidelines recommends midaxillary line (MAL) as zero reference level in intra-abdominal pressure (IAP) measurements in aiming at standardizing the technique, evidence supporting this suggestion is scarce. The aim of this study is to study if the zero reference position influences bladder pressure measurements as estimate for IAP.
The IAP of 100 surgical patients was measured during the first 24 h of admission to the surgical intensive care unit of General Calixto Garcia Hospital in Havana (Cuba) following laparotomy. The period was January 2009 to January 2010. The IAP was measured twice with a six-hour interval using the transurethral technique with a priming volume of 25 ml. IAP was first measured with the zero reference level placed at MAL (IAPMAL), followed by a second measurement at the level of the symphysis pubis (SP) after 3 minutes (IAPSP). Correlations were made between IAP and body mass index (BMI), type of surgery, gender, and age.
Mean IAPMAL was 8.5 ± 2.8 mmHg vs. IAPSP 6.5 ± 2.8 mmHg (p < 0.0001). The bias between measurements was 2.0 ± 1.5, 95% confidence interval of 1.4 to 3.0, upper limit of 4.9, lower limit of -0.9, and a percentage error of 35.1%. IAPMAL was consistently higher than IAPSP regardless of the type of surgery. The BMI correlated with IAP values regardless of the zero reference level (R2 = 0.4 and 0.3 with IAPMAL and IAPSP respectively, p < 0.0001).
The zero reference level has an important impact on IAP measurement in surgical patients after laparotomy and can potentially lead to over or underestimation. Further anthropometric studies are needed with regard to the relative MAL and SP zero reference position in relation to the theoretical ideal reference level at midpoint of the abdomen. Until better evidence is available, MAL remains the recommended zero reference position due to its best anatomical localization at iliac crest.
PMCID: PMC3390299  PMID: 22873414
intra-abdominal pressure; measurement; bladder pressure; zero reference; midaxillary line; symphysis pubis; laparotomy.
22.  Arterial blood pressure monitoring in overweight critically ill patients: invasive or noninvasive? 
Critical Care  2006;10(2):R64.
Blood pressure measurements frequently guide management in critical care. Direct readings, commonly from a major artery, are considered to be the gold standard. Because arterial cannulation is associated with risks, alternative noninvasive blood pressure (NIBP) measurements are routinely used. However, the accuracy of NIBP determinations in overweight patients in the outpatient setting is variable, and little is known about critically ill patients. This prospective, observational study was performed to compare direct intra-arterial blood pressure (IABP) with NIBP measurements obtained using auscultatory and oscillometric methods in overweight patients admitted to our medical intensive care unit.
Adult critically ill patients with a body mass index (BMI) of 25 kg/m2 or greater and a functional arterial line (assessed using the rapid flush test) were enrolled in the study. IABP measurements were compared with those obtained noninvasively. A calibrated aneroid manometer (auscultatory technique) with arm cuffs compatible with arm sizes and a NIBP monitor (oscillometric technique) were used for NIBP measurements. Agreement between methods was assessed using Bland-Altman analysis.
Fifty-four patients (23 males) with a mean (± standard error) age of 57 ± 3 years were studied. The mean BMI was 34.0 ± 1.4 kg/m2. Mean arm circumference was 32 ± 0.6 cm. IABP readings were obtained from the radial artery in all patients. Only eight patients were receiving vasoactive medications. Mean overall biases for the auscultatory and oscillometric techniques were 4.1 ± 1.9 and -8.0 ± 1.7 mmHg, respectively (P < 0.0001), with wide limits of agreement. The overestimation of blood pressure using the auscultatory technique was more important in patients with a BMI of 30 kg/m2 or greater. In hypertensive patients both NIBP methods underestimated blood pressure as determined using direct IABP measurement.
Oscillometric blood pressure measurements underestimated IABP readings regardless of patient BMI. Auscultatory measurements were also inaccurate, tending to underestimate systolic blood pressure and overestimate mean arterial and diastolic blood pressure. NIBP can be inaccurate among overweight critically ill patients and lead to erroneous interpretations of blood pressure.
PMCID: PMC1550873  PMID: 16630359
23.  We should care more about intracuff pressure: The actual situation in government sector teaching hospital 
Indian Journal of Anaesthesia  2010;54(4):314-317.
Endotracheal tube (ETT) should have intracuff pressure (ICP) in the range of 20 to 30 cm water (H2O). In this observational study, we studied the trend amongst anaesthesiologist in choosing the type of ETT and their ability to assess optimum ICP clinically. After institutional ethics committee approval, we observed 75 patients under general endotracheal anaesthesia in Government Medical College. Anaesthesiologists were blinded to study purpose. The type of ETT used and magnitude of ICP was recorded. ICP was measured using simple aneroid manometer. Once the pressure was measured, it was readjusted to normal range and nitrous oxide was allowed to start. Red rubber tube was used in 18.7% and polyvinyl chloride (PVC) in 81.3% cases. The anaesthesiologists were not able to assess ICP in the recommended range clinically in 100% cases when red rubber ETT was used and in 40% cases when portex ETT was used. Red rubber ETT (reusable) with low-volume high-pressure cuff is still in use, though the trend is shifting towards more of using PVC ETT. Anaesthesiologists were not able to inflate the ETT cuff to the recommended range in spite of their clinical expertise (more than 5 years of teaching experience) in significant number of cases. We recommend the use of simple aneroid manometer for objective monitoring of ICP over subjective assessment, not only in red rubber, but also in PVC ETT.
PMCID: PMC2943700  PMID: 20882173
Aneroid manometer; intra cuff pressure; polyvinyl chloride endotracheal tube; red rubber endotracheal tube
24.  Effect of mechanical ventilation on intra-abdominal pressure in critically ill patients without other risk factors for abdominal hypertension: an observational multicenter epidemiological study 
Annals of Intensive Care  2012;2(Suppl 1):S22.
Mechanical ventilation (MV) is considered a predisposing factor for increased intra-abdominal pressure (IAP), especially when positive end-expiratory pressure (PEEP) is applied or in the presence of auto-PEEP. So far, no prospective data exists on the effect of MV on IAP. The study aims to look on the effects of MV on IAP in a group of critically ill patients with no other risk factors for intra-abdominal hypertension (IAH).
An observational multicenter study was conducted on a total of 100 patients divided into two groups: 50 patients without MV and 50 patients with MV. All patients were admitted to the intensive care units of the Medical and Surgical Research Centre, the Carlos J. Finlay Hospital, the Julio Trigo University Hospital, and the Calixto García Hospital, in Havana, Cuba between July 2000 and December 2004. The IAP was measured twice daily on admission using a standard transurethral technique. IAH was considered if IAP was greater than 12 mmHg. Correlations were made between IAP and body mass index (BMI), diagnostic category, gender, age, and ventilatory parameters.
The mean IAP in patients on MV was 6.7 ± 4.1 mmHg and significantly higher than in patients without MV (3.6 ± 2.4 mmHg, p < 0.0001). This difference was maintained regardless of gender, age, BMI, and diagnosis. The use of MV and BMI were independent predictors for IAH for the whole population, while male gender, assisted ventilation mode, and the use of PEEP were independent factors associated with IAH in patients on MV.
In this study, MV was identified as an independent predisposing factor for the development of IAH. Critically ill patients, which are on MV, present with higher IAP values on admission and should be monitored very closely, especially if PEEP is applied, even when they have no other apparent risk factors for IAH.
PMCID: PMC3527157  PMID: 23281625
A rapid method for measuring tissue pressures has been designed. A pressure of 250 mm. Hg is imposed on a manometer. Then the system is allowed to discharge into a needle cannula inserted in the tissue. The manometer forces out fluid (about 10 until the pressure within it is the same as that within the tissue. Records of the pressure changes are made. Each observation takes about a minute. The method gives results that are closely comparable with other reports of tissue pressures. With this method, the pressure in the following organs of dogs was found to be: kidney, 26 mm. Hg, cerebral cortex, 0 to 5 mm., muscle, 1 to 10 mm., spleen, S to 16 mm., subcutaneous tissue, 0 to 3 mm., and liver –2 to 14 mm. The reliability of the method was tested on the kidneys of decerebrate dogs. Measurements were found to be the same within narrow limits over a period of an hour; they were the same when taken simultaneously in different regions of the same kidney or in opposite kidneys. They were independent of the volume of fluid forced into the tissue. Similar pressures were observed with 1 or 5 or 10 holes bored in the shaft of the cannulating needle. The intrarenal pressure was also measured by inserting a needle cannula into the tissue and then allowing the pressure to reach equilibrium passively with a manometer. This method gave similar results. The intrarenal pressure has now found to be the same when measured by three different technics.
PMCID: PMC2135999  PMID: 14784541

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