Esophageal Pressure Changes Research Articles

American Gastroenterological Association Institute Technical Review on the Management of Gastroesophageal Reflux Disease

American Gastroenterological Association Institute Technical Review on the Management of Gastroesophageal Reflux Disease

New esophageal function testing (impedance, Bravo pH monitoring, and high-resolution manometry): Clinical relevance

Esophageal testing aims to quantify gastroesophageal reflux or characterize esophageal motility. Reflux monitoring traditionally has been based on the detection of acidic reflux by a transnasal catheter that measures esophageal pH. Recently there have been two major developments in this field: the wireless Bravo pH capsule (Medtronic, Inc., Minneapolis, MN), which allows catheter-free monitoring, and impedance-pH measurement, a catheter-based technique that enables detection of acidic and nonacidic reflux. The assessment of esophageal motility has relied on conventional manometry for many years. Two new procedures also recently became available to assess esophageal motility: high-resolution manometry, which uses many closely spaced pressure sensors and provides spatiotemporal plots of esophageal pressure changes, and impedance manometry, a test that directly measures bolus transit and provides conventional manometric data. The advantages, disadvantages, and clinical importance of these new esophageal tests are discussed in this review.

80 Upper Esophageal Sphincter and Gastroesophageal Junction Pressure Changes Act to Prevent Reflux During Obstructive Sleep Apnea in GERD Patients

Introduction: Gastroesophageal reflux (GER) is thought to be induced by deceasing intraesophageal pressure during obstructive sleep apnea (OSA). However, pressure changes in the upper esophageal sphincter (UES) and gastroesophageal junction (GEJ) pressure during OSA events have not been measured. Aims: Determine UES and GEJ pressure change during OSA and characterize the GER and esophago-pharyngeal reflux (EPR) events during sleep. Methods: We studied 12 controls, 5 GERD without OSA and 6 GERD with OSA patients for 6-hours post-prandially during sleep. We concurrently recorded: a) UES, GEJ and esophageal body (ESO) pressures with a high-resolution manometric system. b) pharyngeal and esophageal reflux events by impedance and pH recordings. c) sleep stages and respiratory events using polysomnogram. End inspiration UES, GEJ and ESO pressures over intervals of OSA were averaged in GERD/OSA patients and compared to average values for randomly selected ten-second intervals during sleep in controls and GERD patients. Results: Total sleep time was 309±46, 317±39 and 306±58 minutes in controls, GERD and OSA patients, respectively. Our findings confirm previous reports of decreasing ESO pressures during OSA events, however, end-inspiratory UES and GEJ pressures at the end of OSA events were significantly higher than those at the beginning of OSA (p<0.01, Table 1). End-expiratory pressure in UES, GEJ and ESO at the beginning of OSA was not changed during OSA. Only two GER events during OSA were recorded in OSA patients. The incidence of GER and EPR events during sleep in GERD/OSA patients did not differ from those in controls and GERD patients (Table 2). Conclusion: Despite a decrease in ESO pressure during OSA events, compensatory changes in UES and GEJ pressures prevent GERD patients with OSA from having an increase in reflux events.

A novel partial 5HT3 agonist DDP733 after a standard refluxogenic meal reduces reflux events: a randomized, double‐blind, placebo‐controlled pharmacodynamic study

DDP733, a selective partial 5HT(3) receptor agonist, increases lower oesophageal sphincter pressure in experimental animal models. However, its effect on gastro-oesophageal reflux or lower oesophageal sphincter pressure in humans remains unknown. To evaluate the effect of DDP733 on reflux episodes in healthy volunteers receiving a refluxogenic meal. A randomized, double-blind, placebo-controlled cross-over study evaluated the pharmacodynamic effects of DDP733 (0.5, 0.8 and 1.4 mg). Healthy subjects underwent oesophageal manometry and intra-oesophageal multichannel intraluminal impedance and pH after a refluxogenic meal. DDP733 0.5 mg significantly (P = 0.013) reduced the rate of reflux episodes after a refluxogenic meal from 10 (+/-2.2) on placebo to 6 (+/-1.2) on drug over a 2-h period. DDP733 0.8 and 1.4 mg had no significant effect on reducing the number of reflux episodes. Significant differences in resting lower oesophageal sphincter pressure and the proportion of time pH was <4 (placebo minus drug) after a refluxogenic meal were not observed. No serious adverse events were reported. In healthy subjects, the partial 5HT(3) agonist DDP733 at a dose of 0.5 mg significantly reduces the rate of reflux events, but did not result in a significant change in lower oesophageal sphincter pressure at 1 h postdosing.

The effect of epinephrine by nebulization on measures of airway obstruction in patients with acute severe croup

To demonstrate that tests of pulmonary function applicable to sick infants and small children with acute severe viral croup would provide clear, objective evidence of responsiveness to therapy with nebulized epinephrine. Oesophageal pressure changes and airflows at the mouth were measured in 17 patients with acute severe croup, before and after nebulization with epinephrine. In 12 of the 17 patients there was a significant improvement in respiratory mechanics following epinephrine nebulization. Six of the 12 patients who responded to adrenaline also received 0.9% saline by nebulization, without improvement. No measures derived from combined flow and volume data showed any statistically significant change following epinephrine nebulization. Measures combining flow and pressure data, specifically inspiratory airway resistance, expiratory airway resistance, work of breathing, rate of work of breathing and volume for effort, showed changes of 26%, 33%, 16%, 16% and 46% respectively. The most statistically significant measures were pressure-rate product, pressure-time integral, oesophageal pressure alone and expiratory resistance. These changes persisted for at least 10 min after inhalation although there was some evidence of decline in pharmacologic effect at that time. Nebulized epinephrine results in a short-lived improvement in some but not all patients with croup. This reduction in respiratory effort occurs secondary to a decline in inspiratory and expiratory airway resistance. Oesophageal pressures measured via a feeding tube are satisfactory for quantification of the acute response and may be a useful continuous monitoring device. Flow measurements are unhelpful, and continuous administration of nebulized epinephrine should be investigated.

Sternomastoid, rib cage, and expiratory muscle activity during weaning failure

We hypothesized that patients who fail weaning from mechanical ventilation recruit their inspiratory rib cage muscles sooner than they recruit their expiratory muscles, and that rib cage muscle recruitment is accompanied by recruitment of sternomastoid muscles. Accordingly, we measured sternomastoid electrical activity and changes in esophageal (DeltaPes) and gastric pressure (DeltaPga) in 11 weaning-failure and 8 weaning-success patients. At the start of trial, failure patients exhibited a higher DeltaPga-to-DeltaPes ratio than did success patients (P = 0.05), whereas expiratory rise in Pga was equivalent in the two groups. Between the start and end of the trial, failure patients developed additional increases in DeltaPga-to-DeltaPes ratio (P < 0.0014) and the expiratory rise in Pga also increased (P < 0.004). At the start of trial, sternomastoid activity was present in 8 of 11 failure patients contrasted with 1 of 8 success patients. Over the course of the trial, sternomastoid activity increased by 53.0 +/- 9.3% in the failure patients (P = 0.0005), whereas it did not change in the success patients. Failure patients recruited their respiratory muscles in a sequential manner. The sequence began with activity of diaphragm and greater-than-normal activity of inspiratory rib cage muscles; recruitment of sternomastoids and rib cage muscles approached near maximum within 4 min of trial commencement; expiratory muscles were recruited slowest of all. In conclusion, not only is activity of the inspiratory rib cage muscles increased during a failed weaning trial, but respiratory centers also recruit sternomastoid and expiratory muscles. Extradiaphragmatic muscle recruitment may be a mechanism for offsetting the effects of increased load on a weak diaphragm.

A Model for Gastric Banding in the Treatment of Morbid Obesity

This work establishes an animal model for nonadjustable gastric banding and characterizes the effect of gastric banding on esophageal physiology. Obstruction at the esophagogastric junction (EGJ) results in esophageal dilation and aperistalsis. Although laparoscopic gastric banding as a primary treatment of morbid obesity has been widely accepted, the effects of this therapy on esophageal function remain unknown. Twenty-five opossums were randomly divided into sham (n = 5), EGJ band (n = 5), and gastric band (n = 15) groups. Gastric and EGJ bands were surgically placed, and esophageal manometry was performed prebanding, at 2-week intervals during the banding period (up to 14 weeks), and 2 and 4 weeks after band removal. Manometric measures were equivalent prior to banding in all groups. There were no changes in LES or esophageal pressures during the study period in the sham group. During banding, there was a 36% decrease in baseline mean resting lower esophageal sphincter pressure in the gastric band group (P = 0.003). Mean distal esophageal peristaltic pressure decreased from baseline by 36% in gastric band animals (P < 0.001). The incidence of esophageal motility disorder during the study period for sham, EGJ band, and gastric band groups, was 2.9%, 42.1%, and 31.3%, respectively (P = 0.001, P = 0.381, pairwise comparisons of gastric band vs. sham and gastric band versus EGJ groups, respectively). Immediately prior to band removal, the probability of an abnormal peristaltic sequence with each swallow was 1%, 38%, and 16% for sham, EGJ, and gastric band groups, respectively (P < 0.005, pairwise comparisons of band groups with sham). Nonadjustable gastric banding results in impaired esophageal body motility, a reduction in esophageal peristaltic pressure, and a reduction in resting lower esophageal sphincter pressure. These findings suggest that gastric banding causes esophageal outlet obstruction and subsequent decompensation of peristaltic function as well as a compromise of the native antireflux mechanism.

The effect of inspired gas density on pulmonary artery transmural pressure and exercise induced pulmonary haemorrhage

Pulmonary capillary stress failure, largely as a result of high pulmonary vascular pressures, has been implicated in the aetiology of EIPH. However, the role of the respiratory system in determining the magnitude of EIPH has received little attention. Horses breathing a gas of greater density than air will exhibit greater transmural pulmonary arterial pressures (TPAP) and more severe EIPH, and horses breathing a gas of lower density than air will exhibit lower TPAP and less severe EIPH, both compared with horses breathing air. Following a warm-up, 8 Thoroughbred horses were exercised for 1 min at 10, 11 and 12 m/sec (5 degrees incline) breathing air or 21% oxygen/79% helium or 21% oxygen/79% argon in a randomised order. Heart rate, respiratory rate, pulmonary arterial pressure and oesophageal pressure were measured during exercise. Bronchoalveolar lavage fluid (BALF) was collected from the dorsocaudal regions of the left and right lungs 40 min post exercise and red blood cell (RBC) counts were performed. The exercise tests induced mild EIPH. Maximum changes in oesophageal pressure were lower on helium-oxygen compared to argon-oxygen (P<0.001). TPAP and median RBC counts did not differ between gas mixtures. BALF RBC counts from the left lung correlated with counts from the right lung (P<0.0001). However BALF RBC counts from the left lung were higher than those from the right lung (P = 0.004). As alterations in pulmonary arterial and oesophageal pressure caused by changes in inspired gas density were of similar magnitude, TPAP remained unchanged and there was no significant effect on EIPH severity. Manipulations that decrease swings in intrapleural pressure may only decrease the degree of EIPH in horses severely affected by the condition.

Acute effects of thixotropy conditioning of inspiratory muscles on end-expiratory chest wall and lung volumes in normal humans

Thixotropy conditioning of inspiratory muscles consisting of maximal inspiratory effort performed at an inflated lung volume is followed by an increase in end-expiratory position of the rib cage in normal human subjects. When performed at a deflated lung volume, conditioning is followed by a reduction in end-expiratory position. The present study was performed to determine whether changes in end-expiratory chest wall and lung volumes occur after thixotropy conditioning. We first examined the acute effects of conditioning on chest wall volume during subsequent five-breath cycles using respiratory inductive plethysmography (n = 8). End-expiratory chest wall volume increased after conditioning at an inflated lung volume (P < 0.05), which was attained mainly by rib cage movements. Conditioning at a deflated lung volume was followed by reductions in end-expiratory chest wall volume, which was explained by rib cage and abdominal volume changes (P < 0.05). End-expiratory esophageal pressure decreased and increased after conditioning at inflated and deflated lung volumes, respectively (n = 3). These changes in end-expiratory volumes and esophageal pressure were greatest for the first breath after conditioning. We also found that an increase in spirometrically determined inspiratory capacity (n = 13) was maintained for 3 min after conditioning at a deflated lung volume, and a decrease for 1 min after conditioning at an inflated lung volume. Helium-dilution end-expiratory lung volume increased and decreased after conditioning at inflated and deflated lung volumes, respectively (both P < 0.05; n = 11). These results suggest that thixotropy conditioning changes end-expiratory volume of the chest wall and lung in normal human subjects.

Relationship between changes in plasma gastrin and lower oesophageal sphincter pressure after meals.

Changes in plasma gastrin and lower oesophageal sphincter pressure were measured in 20 subjects after a standard protein meal. Significant increases in both gastrin and sphincter pressure were seen. Peak gastrin response occurred an average of 19-5 minutes and peak lower oesophageal sphincter response 40-0 minutes after the meal. Both gastrin and sphincter pressure showed a wide spectrum of response. In 5 subjects there was no appreciable rise (less than 5 pg/ml) in plasma gastrin after the meal, and 3 of these had symptoms of oesophageal reflux. In this group there was only a small but nervertheless significant rise in lower oesophageal sphincter pressure (mean pressure rise 18-0 per cent of fasting value, p less than 0.05). Greater increases in sphincter pressure (mean rise 54-2 per cent, p less than 0.005) were seen in subjects with a moderate (up to 50 pg/ml) rise in plasma gastrin, and those with the most marked gastrin response (less than 50 pg/ml) showed the greatest rise in pressure (mean rise 80-3 per cent, p less than 0.0025). These results suggest that endogenous plasma gastrin is the main stimulus to the rise in lower oesophageal sphincter pressure after food. Subjects with a poor gastrin response to the meal have only a small increase in sphincter pressure and as a result may be more liable to develop gastro-oesophageal reflux.

Lower oesophageal sphincter pressure and timed barium oesophagogram: two objective parameters in the non-invasive assessment of primary achalasia

The non-invasive assessment of primary achalasia is not precise. To compare investigations before and 1 month after balloon dilation in achalasia. Fifty-two patients with primary achalasia were enrolled. Subjective and objective variables of oesophageal functions were analysed before and 1 month after balloon dilation. The mean predilation symptom score, lower oesophageal sphincter pressure, height and volume of barium at 5 min were 7.7 +/- 2.6, 62.0 +/- 25.1 mmHg, 9.2 +/- 6.1 cm and 53.2 +/- 49.8 mL respectively; the mean postdilation values were 3.0 +/- 3.0, 34.1 +/- 12.5 mmHg, 7.9 +/- 5.1 cm and 28.0 +/- 30.1 mL respectively. The before dilation volume of barium at 5 min correlates significantly with lower oesophageal sphincter pressure (P < 0.01). The mean symptom scores, lower oesophageal sphincter pressure and volume of barium at 5 min dropped significantly after intervention (P < 0.01), but the reduction in barium height at 5 min was not significant. The percentage changes in volume at 5 min significantly predicted the percentage changes in lower oesophageal sphincter pressure (P < 0.01). The volume of barium retention at 5 min can predict the lower oesophageal sphincter pressure before and after balloon dilation in primary achalasia. This could be used as a non-invasive objective tool for initial and post-dilation assessment.

Evaluation of Esophageal Function/pH in Endoscopic Therapy for Gastroesophageal Reflux Disease

Gastroesophageal reflux disease (GERD) typically requires lifelong medical therapy or surgery for the management of patients with frequent symptoms. The current standard of care is to prescribe medical therapy using proton pump inhibitors. Patients with moderate-to-severe GERD require extended/maintenance therapy. Until recently, the only alternative to this approach was surgical intervention. Endoscopic therapy for GERD has emerged as a second alternative strategy. Primary endpoints for all interventions have aimed at symptomatic control and reduction/discontinuance of medication use. For surgical and endoscopic therapies, however, there are other physiologic endpoints that have attempted to define changes in lower esophageal sphincter pressure and esophageal acid exposure. For patients being evaluated for endoscopic GERD therapy, the author recommends comprehensive esophageal testing and pH testing.

Skeletal muscle pumpversusrespiratory muscle pump: modulation of venous return from the locomotor limb in humans

The vast majority of quantitative data examining the effects of breathing on venous return have been derived from anaesthetized or reduced animal preparations, making an extrapolation to an upright exercising human problematic due to the lack of a hydrostatic column and an absence of muscular contraction. Thus, this study is the first to quantitatively examine the effects of different breathing mechanics on venous return from the locomotor limbs both at rest and during calf contraction exercise in the semirecumbent human. When subjects inspired using predominantly their ribcage/accessory inspiratory muscles at rest (change in gastric pressure (DeltaP(GA)) = <2 cmH(2)O, change in oesophageal pressure (DeltaP(ES)) = approximately -6 cmH(2)O; inspiratory time/total breath time (T(I)/T(TOT)) = 0.5), a slight facilitation of femoral venous return was observed during inspiration (65% of all flow occurred during inspiration), with a slight reduction in femoral venous return during the ensuing expiratory phase of the breath. However, when subjects inspired using a predominantly diaphragmatic breath at rest (DeltaP(GA) = > 5 cmH(2)O, DeltaP(ES) = approximately -6 cmH(2)O; T(I)/T(TOT) = 0.5), femoral venous return was markedly impeded (net retrograde flow of 11%) and significantly lower than that observed during ribcage breathing conditions (P < 0.01). During the ensuing expiratory phase of a diaphragmatic breath, there was a large resurgence of femoral venous blood flow. The pattern of modulation during ribcage and diaphragmatic breathing persisted during both mild (peak calf force = 7 kg) and moderate (peak calf force = 11 kg) levels of calf contraction. Despite the significant within-breath modulation of femoral venous return by breathing, net blood flow in the steady state was not altered by the breathing pattern followed by the subjects. Though popliteal blood flow appeared to be modulated by respiration at rest, this pattern was absent during mild calf contraction where popliteal outflow was phasic with the concentric phase of calf contraction. We conclude that respiratory muscle pressure production is the predominant factor modulating venous return from the locomotor limb both at rest and during calf contraction even when the veins of the lower limb are distended due to the presence of a physiologic hydrostatic column.

ALTERATION OF LOWER ESOPHAGEAL SPHINCTER PRESSURE FOLLOWING ENDOSCOPIC VARICEAL LIGATION (PRELIMINARY REPORT)

Purpose: Endoscopic variceal ligation (EVL) and Endoscopic sclerother-apy (EVS) are the two first line therapy for bleeding esophageal varices. In addition EVL may also be used as primary prophylaxis for variceal bleeding. Both sclerotherapy and EVL are reported to be associated with altered esophageal motility. Lower esophageal pressure changes following endoscopic sclerotherapy in the available data are heterogeneous. Altered esophageal motility may be due to esophageal inflamation at the early stage or due to subsequent fibrosis. Data regarding pressure changes of LES following EVL are relativly inadequate in literature. Previous studies shows, there is no early changes (<24 hrs) of LES pressure following EVL as well as Endoscopic sclerotherapy. Aim of the Study: To see the late effect of EVL on the change of pressure of LES. Methods: Sixteen patients of portal hypertension underwent esophageal mannometry one hour prior to EVL and 4 weeks after. Mannometry was performed using a continuous water perfusion system with external transducer and analysed using software Albyn Medical System. EVL was done using Omniview 6 shooter variceal ligator. Results: The study was completed in 8 pts. of which EVL done for secondary prophylaxis in 5 and for primary prophylaxis in 3 pts. Basal mid expiratory LES pressure ranged from 7 mm of Hg to 27 mm of Hg. Four weeks post EVL, LES pressure ranged from 5 mm to 45 mm of Hg. The mean LES pressure increased in 5 pts. (62.5%), decreased in 2(25%) and remained normal in 1pt. (12.5%). The mean amplitude of contraction as well as duration of contraction remained almost same before and after EVL. Conclusions: EVL causes rise of LES pressure in majority of the cases, however their effect in long term follow up needs to be defined and the rise of LES pressure does not produce symptoms by interfering passage of food in those sub group of patients.

Endoscopic GERD therapy: is enteryx the answer?: Johnson DA, Ganz R, Aisenberg J, et al., Endoscopic, deep mural implantation of enteryx for the treatment of GERD: 6-month follow-up of a multicenter trial, Am J Gastroenterol 2003;98:250–8

In the February issue of The American Journal of Gastroenterology, Johnson et al. describe a single-armed, unblinded, prospective, controlled trial evaluating the efficacy and safety of Enteryx (Enteryx, Boston Scientific Corp., Natick, MA) implantation at or just distal to the squamocolumnar junction for the treatment of proton pump inhibitor (PPI)-responsive gastroesophageal reflux disease (GERD). To be included in the study, patients had to have heartburn and/or regurgitation with GERD confirmed by pH-metry. Additionally, symptoms had to be relieved with PPIs (defined by a GERD health-related quality-of-life [HRQL] score < 11), and the symptoms had to recur when PPIs were discontinued (defined by a GERD-HRQL > 20). Exclusion criteria included Barrett's epithelium, hiatal hernia > 3 cm, persistent esophagitis > grade III with administration of PPIs, and esophageal motility disorders. Patients were evaluated at eight sites, and the study reported results over a 6-month period. After an extensive baseline evaluation, enrolled patients underwent the Enteryx injection procedure while taking PPIs, and then discontinued taking PPIs on day 11 after the procedure. At that point, patients were asked to take only antacids as needed. If antacids failed to control symptoms, histamine receptor antagonists (H2RAs) were given. If H2RAs failed to control symptoms, PPIs were resumed. The primary outcome was the use of PPIs 6 months after the procedure. Additional outcomes included questionnaire results measuring GERD-related symptoms and generic health status, esophageal manometric parameters, and esophageal pH measurements. Adverse events were also recorded. A total of 85 patients were enrolled, but five were unavailable for evaluation at the 6-month visit. The remaining 80 patients were included in the analysis. After 6 months, 74% of study patients were able to eliminate PPIs, and 10% were able to reduce PPIs by more than 50%, resulting in a combined 84% “medication improved.” Most of these patients were able to discontinue all medications, with only approximately 15% requiring antacids or H2RAs. The GERD-HRQOL scores and broader quality of life scores were significantly improved at 6 months after Enteryx treatment compared with baseline scores when PPIs were not being taken. Esophageal acid exposure measured in 71 patients after Enteryx treatment was statistically improved compared with baseline scores when PPIs were not being taken in the median time at pH < 4 (supine, upright, and total) and in the total number of episodes of pH < 4. The authors also noted that 26/71 (37%) of patients normalized their pH measurement (total time). Manometry measured in 74 patients revealed that the median lower esophageal sphincter length significantly increased during the follow-up period as well, although there were no significant changes in lower esophageal sphincter pressure. There were no clinically serious adverse events that were life-threatening or required surgical intervention. Retrosternal chest pain that was mild or moderate was experienced by 91.8% of patients, and it resolved within 2 weeks in most cases. Of patients with chest pain, 69.2% used prescribed oral analgesics, and 10.3% used over-the-counter analgesics. Seventeen patients (20%) reported dysphagia, all of which resolved by 12 wk. One patient underwent two dilation procedures. Ten patients (11.8%) had low grade fevers, all of which resolved within 3 days. In accordance with the protocol, 19 patients (22%) were retreated with Enteryx injection because of inadequate relief with the initial treatment. At 6 months, 12/19 had reduced or eliminated PPIs. The authors concluded that endoscopic implantation of Enteryx is a relatively safe and efficacious treatment option for the management of GERD, and that it might offer a viable alternative to lifelong PPI drug use without the risks associated with antireflux surgery.

Influence of maturation on infant diaphragm function assessed by magnetic stimulation of phrenic nerves.

Infant diaphragm function may be adversely affected in a variety of disorders and conditions. Key to establishing an accurate diagnosis are appropriate control data. The aim of this study was to determine the effect of maturation on diaphragm function, using a nonvolitional test. Diaphragm function was assessed by measuring the transdiaphragmatic pressure (Pdi) generated by magnetic stimulation of the phrenic nerves. Ballon catheters were positioned in the lower third of the esophagus and stomach. Esophageal (Pes) and gastric (Pgas) pressure changes were measured using differential pressure transducers. The pressure signals were amplified and displayed in real time on a computer (running Labview trade mark software) and Pdi derived by online subtraction of Pes from Pgas. Twenty-nine infants (14 born preterm), at a median gestational age of 37 (range, 25-42) weeks, were studied at a median postconceptional age (PCA) of 39 (range, 32-44) weeks. At time of measurement, none had respiratory problems or were hyperinflated (functional residual capacity ranged from 23-35 mL/kg). The preterm infants had significantly lower transdiaphragmatic pressures responses following median left (4.0, range 2.5-6.8 cmH(2)O vs. 4.8, range 2.8-7.2 cmH(2)O) and median right phrenic nerve stimulation (3.6, range 2.6-4.8 cmH(2)O vs. 4.3, range 2.7-6.8 cmH(2)O) (P < 0.05) than term infants. Following left and right phrenic nerve stimulation, Pdi correlated significantly with gestational age (r = 0.4, P < 0.05, and r = 0.4, P < 0.05, respectively) and PCA (r = 0.37, P = 0.05, and r = 0.56, P < 0.01, respectively). We conclude that gestational age at birth and postconceptional age at time of measurements must be taken into account when interpreting the results of infant diaphragm function tests.

Preoperative prediction of long‐term outcome following laparoscopic fundoplication

Although long-term outcomes following laparoscopic fundoplication for gastro-oesophageal disease have now been reported as very satisfactory, a small, but important, minority of patients are unhappy with the outcome, often due to recurrent reflux symptoms or new-onset dysphagia. In this study, we sought to establish whether various parameters that can be determined before surgery, can predict the long-term outcome of surgery. Data collected prospectively were evaluated to determine factors that were associated with outcome at 5 years following laparoscopic fundoplication. Inclusion criteria were complete preoperative assessment data and 5-year follow-up data. Data examined included information on preoperative age, sex, weight, home address, health insurance status, duration of reflux symptoms, previous surgery, operating surgeon, endoscopy and 24-h pH monitoring. In addition, lower oesophageal sphincter resting and residual relaxation pressures were evaluated before and after surgery. The postoperative symptoms of heartburn and dysphagia, as well as overall satisfaction 5 years following surgery was determined using a 0-10 visual analogue scale. The association of the pre- and perioperative factors and outcome at 5 years was determined by univariate and linear regression analysis. Two hundred and sixty-two patients from an overall experience of over 1000 laparoscopic anti-reflux procedures met the entry criteria. There was no association between patient address, age, weight, duration of symptoms, the presence of endoscopically proven oesophagitis, operating surgeon, the necessity for conversion to an open procedure, change in lower oesophageal sphincter residual relaxation pressure and the outcome parameters. Using univariate analysis, a higher heartburn score was associated with previous abdominal surgery, female sex, no private health insurance, and a normal preoperative 24-h pH study. A higher dysphagia score was associated with a normal preoperative pH study, a postoperative increase in lower oesophageal sphincter resting pressure of more than 6 mmHg, and previous abdominal surgery. Overall satisfaction with the outcome at 5 years was higher among male patients, private patients, patients who had a hiatus hernia, and patients who had an abnormal preoperative pH study. Linear regression analysis confirmed that private insurance, male sex, and the absence of previous abdominal surgery, were the strongest predictors of an improved heartburn score, whereas male sex and private health insurance were the strongest predictors of greater satisfaction with the overall outcome. There are parameters that can be assessed before or during laparoscopic Nissen fundoplication that correlate with late outcome parameters. In particular, male patients and those from higher socioeconomic groups appear to have a better long-term outcome.

New Methods for the Non-Invasive Assessment of Sympathetic Activity During Sleep. Neue Methoden zur nicht-invasiven Erfassung des Sympathikotonus im Schlaf

Autonomous nervous functions do change with normal sleep and do show characteristic changes with sleep disorders. This is why the investigation of autonomous nervous function during sleep plays an important role. Two different and new methods will be introduced here. The pulse transit time (PTT) determines the time delay between ECG and the resulting peripheral pulse wave. PTT is reverse proportional to arterial blood pressure and changes in amplitude of the PTT signal do correlate well with intra-thoracic pressure changes. The peripheral arterial tonometry (PAT) determines the peripheral arterial vascular tone using a plethysmographic method. The peripheral arterial tone is modulated by sympathetic and parasympathetic activity, by peripheral blood pressure, and by the peripheral resistance of the vessels. Both signals are non-invasive methods to assess changes of autonomous nervous function. With the help of both signals in addition to cortical arousal it is possible to detect sub-cortical arousal. This effect and the high correlation with oesophageal pressure and blood pressure changes result in characteristic changes in PTT and PAT for obstructive sleep apnoea. The changes are so characteristic that they can be used diagnostically. In summary, PTT and PAT do show different aspects of the autonomous nervous function and cannot be substituted by each other. Both give important additional information to characterise arousal during sleep and sleep disorders. The clinical and cardiovascular consequences of sub-cortical arousal need prospective long-term follow-up studies.

Central Venous and Bladder Pressure Reflect Transdiaphragmatic Pressure During Pressure Support Ventilation

To determine whether the change in bladder pressure (Pblad) and central venous pressure (Pcvp) may reflect the changes in esophageal pressure (Pes) and gastric pressure (Pgas) when inspiratory pressure support (IPS) is altered. Prospective clinical study. The ICUs of a teaching hospital. Ten patients currently receiving IPS ventilation via a tracheostomy or an endotracheal tube who already had bladder and central venous catheters in situ. Airway pressure, Pes, Pgas, Pcvp, Pblad, and flow were measured at the original IPS setting. IPS then was reduced by 5-cm H(2)O increments until IPS was zero or was at the minimum pressure that could be tolerated by each patient. At each level of IPS, pressures and flow were measured at steady-state breathing. The maximum pressure difference for each pressure during inspiration was calculated. We found that the Delta Pblad correlated closely with the Delta Pgas (r = 0.904) and that the Delta Pes correlated with the Delta Pcvp (r = 0.951). When the Delta Pcvp - Delta Pblad was compared with the transdiaphragmatic pressure for each patient as the IPS was altered, the correlation coefficients varied from 0.952 to 0.999. Although absolute values for the Delta Pcvp during mechanical ventilation do not always reflect the Delta Pes, useful information can be obtained from this route. In individual patients, the two sites of measurement followed each other when IPS was changed, enabling a bedside assessment of the response to reducing respiratory support.

Changes in esophageal variceal pressure after transcatheter arterial embolization for hepatocellular carcinoma.

The aim of this study was to investigate the influence of transcatheter arterial embolization on esophageal variceal pressure and portal hemodynamics. Out of 18 cirrhotic patients with hepatocellular carcinoma, 12 underwent transcatheter arterial embolization and the remaining six patients underwent angiography alone as a control. We examined esophageal variceal pressure with an endoscopic pneumatic pressure sensor and portal blood flow with Doppler ultrasonography immediately before and 3 days after transcatheter arterial embolization or angiography. Angiography alone did not influence esophageal variceal pressure or portal blood flow. Transcatheter arterial embolization resulted in an increase in variceal pressure in five (42%) of the 12 patients and in a marked increase in portal blood flow in eight (88.9%) of nine patients, although no change in the endoscopic variceal findings was observed after transcatheter arterial embolization. The change in esophageal variceal pressure did not correlate with the change in portal blood flow. We could not find predictive factors for the elevation of variceal pressure after transcatheter arterial embolization. Our study demonstrated that transcatheter arterial embolization resulted in an increase in esophageal variceal pressure in about half of the patients, bearing little relation to portal hemodynamic parameters.