Esophageal Catheter Research Articles

Trans-diaphragmatic pressure measurement as a prognostic factor in the Intensive Care Unit in dogs

In the last decade, attempts to improve the quality of the services provided to the critically ill patients in the Intensive Care Unit (ICU) are of great interest in human medicine. The aim of the majority of the clinical studies is the correlation of the survival rate of a critically ill patient with specific prognostic factors at the time of admission. The detailed assessment of a patient at admission in the ICU and during hospitalization seems to affect the management and the outcome. The main aim of this study was to evaluate if the trans-diaphragmatic pressure measurement can be a prognostic factor of the outcome in the ICU in dogs. Thirty-one dogs, 21 male and 10 female was included in this prospective, cohort study. Age, breed, sex, body weight and clinical diagnosis were recorded. The type of admission, the mentation status, physiological and biochemical parameters were measured at the admission of the dog in the ICU. All the variables were assessed over the first 24 hours following ICU admission. The animals were allocated into sixgroups: peritonitis/intra-abdominal surgery, intra-thoracic surgery, respiratory disease, neurologic disease, neoplasia, and systematic disease. The trans-diaphragmatic pressure (Pdi) was measured under the same anesthetic level in all animals with two oesophageal balloon catheters. The most frequent problem for admission in ICU was peritonitis (5/31). Seventeen out of 31 were admitted in acute status while 14/31 had a chronic problem. Mean±standard deviation of Pdi was 10.7±5.6 mmHg and of lactate concentration 2.3±1.2 mmol/L. Both, they can predict outcome (p=0.071 and p=0.076, respectively). Seven out of 31 dogs died, 2 were euthanized and 22 were discharged from the ICU after hospitalization. The technique of Pdi measurement with balloon catheters can be successfully applied in dogs in the ICU. Pdi measurement, as well as lactate concentration may be used as prognostic indicators for the outcome, in dogs in the ICU. However, a bigger sample size is need to support these findings.

A brief airway occlusion is sufficient to measure the patient's inspiratory effort/electrical activity of the diaphragm index (PEI).

Pressure generated by patient’s inspiratory muscles (Pmus) during assisted mechanical ventilation is of significant relevance. However, Pmus is not commonly measured since an esophageal balloon catheter is required. We have previously shown that Pmus can be estimated by measuring the electrical activity of the diaphragm (EAdi) through the Pmus/EAdi index (PEI). We investigated whether PEI could be reliably measured by a brief end-expiratory occlusion maneuver to propose an automated PEI measurement performed by the ventilator. Pmus, EAdi, airway pressure (Paw), and flow waveforms of 12 critically ill patients undergoing assisted mechanical ventilation were recorded. Repeated end-expiratory occlusion maneuvers were performed. PEI was measured at 100 ms (PEI0.1) and 200 ms (PEI0.2) from the start of the occlusion and compared to the PEI measured at the maximum Paw deflection (PEIoccl, reference). PEI0.1 and PEI0.2 tightly correlated with PEIoccl, (p < 0.001, R2 = 0.843 and 0.847). At a patient-level analysis, the highest percentage error was -64% and 50% for PEI0.1 and PEI0.2, respectively, suggesting that PEI0.2 might be a more reliable measurement. After correcting the error bias, the PEI0.2 percentage error was lower than ± 30% in all but one subjects (range − 39 to + 29%). It is possible to calculate PEI over a brief airway occlusion of 200 ms at inspiratory onset without the need for a full patient's inspiratory effort. Automated and repeated brief airway occlusions performed by the ventilator can provide a real time measurement of PEI; combining the automatically measured PEI with the EAdi trace could be used to continuously display the Pmus waveform at the bedside without the need of an esophageal balloon catheter.Electronic supplementary materialThe online version of this article (10.1007/s10877-020-00459-1) contains supplementary material, which is available to authorized users.

Reflex swallowing elicited by electrical stimulation in obstructive sleep apnea patients: A preliminary study

This study tested whether electrical stimulation of the pharyngeal mucosa is able to induce reliably the swallowing reflex in awake and asleep obstructive sleep apnea (OSA) patients, and whether the induced reflexes affect the sleep variables. In addition, the latency, occurrence, and morphology of swallows were evaluated. Eight patients received an esophageal catheter that was used on three consecutive nights for electrical stimulation and manometric recordings. The electrical stimulation proved itself safe, but its efficiency in inducing swallows sank from 80.0 % in awake to 37.4 % in sleeping subjects and was lowest in the sleep stage N3. The swallowing reflex was triggered with a mean latency of 3.69 ± 0.70 s, was predominantly induced in the hyperventilation phase, and had no significant effect on the subject's sleep variables. These findings indicate that electrical stimulation can more effectively trigger the swallowing reflex while the subjects are awake than during sleep without showing remarkable clinical benefits in terms of apnea-hypopnea index (AHI) improvement.

Gastric insufflation during cardiopulmonary resuscitation: A study in human cadavers

IntroductionBag-valve-mask ventilation is the first-line ventilation method during cardiopulmonary resuscitation (CPR). Risks include excessive volume delivery and gastric insufflation, the latter increasing the risk of pneumonia. The efficacy of ventilation can also be reduced by airway closure. We hypothesized that continuous chest compression (CC) could limit the risk of gastric insufflation compared to the recommended 30:2 interrupted CC strategy. This experimental study was performed in human “Thiel” cadavers to assess the respective impact of discontinuous vs. continuous chest compressions on gastric insufflation and ventilation during CPR. MethodsThe 30:2 interrupted CC technique was compared to continuous CC in 5 non-intubated cadavers over a 6 min-period. Flow and Airway Pressure were measured at the mask. A percutaneous gastrostomy allowed measuring the cumulative gastric insufflated volume. Two additional cadavers were equipped with esophageal and gastric catheters instead of the gastrostomy. ResultsFor the 7 cadavers studied (4 women) median age of death was 79 [74–84] years.After 6 min of CPR, the cumulative gastric insufflation measured in 5 cadavers was markedly reduced during continuous CC compared to the interrupted CC strategy: (1.0 [0.8–4.1] vs. 5.9 [4.0–5.6] L; p < 0.05) while expired minute ventilation was slightly higher during continuous than interrupted CC (1.9 [1.4–2.8] vs. 1.6 [1.1–2.7] L/min; P < 0.05).In 2 additional cadavers, the progressive rise in baseline gastric pressure was lower during continuous CC than interrupted CC (1 and 2 cmH2O vs. 12 and 5.8 cmH2O). ConclusionContinuous CC significantly reduces the volume of gas insufflated in the stomach compared to the recommended 30:2 interrupted CC strategy. Ventilation actually delivered to the lung is also slightly increased by the strategy.

Esophageal electrode model and simulation of directed transesophageal electrical pacing of the spinal cord

Abstract Spinal cord stimulation (SCS) is the most commonly used technique of neurostimulation. It involves the stimulation of the spinal cord and is therefore used to treat chronic pain. The existing esophageal catheters are used for temperature monitoring during an electrophysiology study with ablation and transesophageal echocardiography. The aim of the study was to model the spine and new esophageal electrodes for the transesophageal electrical pacing of the spinal cord, and to integrate them in the Offenburg heart rhythm model for the static and dynamic simulation of transesophageal neurostimulation. The modeling and simulation were both performed with the electromagnetic and thermal simulation software CST (Computer Simulation Technology, Darmstadt). Two new esophageal catheters were modelled as well as a thoracic spine based on the dimensions of a human skeleton. The simulation of directed transesophageal neurostimulation is performed using the esophageal balloon catheter with an electric pacing potential of 5 V and a trapezoidal signal. A potential of 4.33 V can be measured directly at the electrode, 3.71 V in the myocardium at a depth of 2 mm, 2.68 V in the thoracic vertebra at a depth of 10 mm, 2.1 V in the thoracic vertebra at a depth of 50 mm and 2.09 V in the spinal cord at a depth of 70 mm. The relation between the voltage delivered to the electrodes and the voltage applied to the spinal cord is linear. Virtual heart rhythm and catheter models as well as the simulation of electrical pacing fields and electrical sensing fields allow the static and dynamic simulation of directed transesophageal electrical pacing of the spinal cord. The 3D simulation of the electrical sensing and pacing fields may be used to optimize transesophageal neurostimulation.

Noninvasive Prediction of Twitch Transdiaphragmatic Pressure: Insights from Spirometry, Diaphragm Ultrasound, and Phrenic Nerve Stimulation Studies

Background: Twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves is the gold standard for non-volitional assessment of diaphragm strength. Expiratory muscle function can be investigated using MS of the abdominal muscles and measurement of twitch gastric pressure (twPgas). Objectives: To investigate whether twitch pressures following MS of the phrenic and lower thoracic nerve roots can be predicted noninvasively by diaphragm ultrasound parameters and volitional tests of respiratory muscle strength. Methods: Sixty-three healthy subjects underwent standard spirometry, measurement of maximum inspiratory (PI_max) and expiratory pressure (PE_max), and diaphragm ultrasound. TwPdi following cervical MS of the phrenic nerve roots and twPgas after lower thoracic MS (twPgas-Thor) were measured using esophageal and gastric balloon catheters inserted transnasally. Using surface electrodes, compound muscle action potentials (CMAP) were simultaneously recorded from the diaphragm or obliquus abdominis muscles, respectively. Results: Forced expiratory flow (FEF_25–75) was significantly correlated with twPdi (r = 0.37; p = 0.003) and its components (twPgas and twitch esophageal pressure, twPes). Diaphragm excursion velocity during tidal breathing was correlated to twPes (r = 0.44; p = 0.02). No prediction of twitch pressures was possible from CMAP amplitude, forced vital capacity (FVC), or PI_max. TwPgas-Thor was correlated with FEF_25–75 (r = 0.46; p = 0.05) and diaphragm thickness at total lung capacity (r = 0.38; p = 0.04) but could not be predicted from CMAP amplitude, FVC, or PE_max. Conclusions: TwPdi and twPgas-Thor cannot be predicted from volitional measures of respiratory muscle strength, diaphragm and abdominal CMAP, or diaphragm ultrasound. Invasive recording of esophageal and gastric pressures following MS remains indispensable for objective assessment of respiratory muscle strength.

A novel method for transpulmonary pressure estimation using fluctuation of central venous pressure.

The objective of the study is to develop a correction method for estimating the change in pleural pressure (ΔPpl) and plateau transpulmonary pressure (PL) by using the change in central venous pressure (ΔCVP). Seven children (aged < 15years) with acute respiratory failure (PaO2/FIO2 < 300mmHg), who were paralyzed and mechanically ventilated with a PEEP of < 10 cmH2O and had central venous catheters and esophageal balloon catheters placed for clinical purposes, were enrolled prospectively. We compared change in esophageal pressure (ΔPes), ΔCVP, and ΔPpl calculated using a corrected ΔCVP (cΔCVP-derived ΔPpl). cΔCVP-derived ΔPpl was calculated as κ × ΔCVP, where κ was the ratio of the change in airway pressure (ΔPaw) to ΔCVP during the occlusion test. cΔCVP-derived ΔPpl correlated better than ΔCVP with ΔPes (R2 = 0.48, p = 0.08 vs. R2 = 0.14, p = 0.4) with lesser bias and precision in Bland-Altman analysis. The plateau PL calculated using the cΔCVP-derived ΔPpl (17.6 ± 2.6 cmH2O) correlated well with the ΔPes-derived plateau PL (18.1 ± 2.3 cmH2O) (R2 = 0.90, p = 0.001). Our correction method can estimate ΔPpl and plateau PL from ΔCVP with a reasonable accuracy in paralyzed and mechanically ventilated pediatric patients with respiratory failure.

Comparison Between Manual and (Semi-)Automated Analyses of Esophageal Diaphragm Electromyography During Endurance Cycling in Patients With COPD.

Background: Electrocardiogram (ECG) contamination is present in diaphragm electromyography (EMGdi) recordings. Obtaining EMGdi without ECG contamination is crucial for EMG amplitude analysis. Manually selecting EMGdi in between QRS complexes has been most commonly applied in recent years (manual method). We developed a semi-automated analysis method based on Least Mean Square Adaptive Filtering combined with a synchronously recorded separate ECG channel to remove ECG artifacts from the EMGdi signals. We hypothesized that this approach would shorten analysis duration and might minimize the potential for inter-rater disagreement.Aims: We aimed to evaluate agreement between the semi-automated method and the manual method and inter-rater reliability of the manual method.Methods: Electromyography signals of seven patients with COPD were recorded using an esophageal catheter during an exercise test on a cycle ergometer. Four patients subsequently participated in an inspiratory muscle training (IMT) program for 8 weeks. After IMT, the tests were repeated. EMGdi/EMGdiMax as obtained either manually by the two assessors or retrieved from the semi-automated method were compared.Results: Semi-automated EMGdi/EMGdiMax agreed well with values obtained by one of the two manual assessors (assessor 1) both at pre-intervention measurements (mean difference −0.5%, 95% CI: −19.6 to 18.6%) and for the pre/post IMT differences (mean difference 1.2%, 95% CI: −16.8 to 19.2%). Intra-class correlation coefficients between methods were 0.96 (95% CI: 0.94–0.97) at pre-intervention measurements and 0.78 (95% CI: 0.58–0.89) for pre/post IMT differences (both p < 0.001). EMGdi/EMGdiMax from assessor 2 was systematically lower than from assessor 1 and agreed less well with the semi-automated method both at pre-intervention measurements (mean difference: 9.3%, 95% CI: −11.4 to 29.9%) and for pre/post IMT differences (mean difference 7.0%, 95% CI: −20.4 to 34.4%). Analysis duration of the semi-automated method was significantly shorter (29 ± 9 min) than the manual method (82 ± 20 min, p < 0.001).Conclusion: The developed semi-automated method is more time efficient and will be less prone to inter-rater variability that was observed when applying the manual analysis method. It is, therefore, proposed as a new standard for objective EMGdi amplitude analyses in future studies.

Recurrent Aspiration Pneumonia in a Missed Case of Broncho-Esophageal Fistula with Repaired Esophageal Atresia: Usefulness of Fiberoptic Bronchoscopy: A Case Report

: Broncho-esophageal fistula (BEF) is a rare congenital anomaly affecting the respiratory and upper gastrointestinal tract. The rarity makes its timely diagnosis very challenging. This study presents a rare case of missed congenital BEF in a six-year-old girl with repaired esophageal atresia in the neonatal period suffering from recurrent respiratory symptoms, choking, and respiratory distress following eating, resulting in vomiting or regurgitation for three years before admission. While the contrast esophagography and endoscopy had failed to diagnose her problem, the methylene blue test via an esophageal catheter observed by fiberoptic bronchoscopy could detect the presence of BEF reliably in the present case. Presenting this case can raise physicians’ knowledge of the diagnostic role of methylene blue test via fiberoptic bronchoscopy.

A Measurement System to Estimate the Pleural Pressure From the CVP for Respiratory System Monitoring

We present a technique to estimate the pleural pressure combining the information provided by the central venous pressure (CVP) and electrocardiographic signals (ECG) for respiratory system monitoring. We discuss the characterization of the proposed measurement method with theoretical modeling, numerical analysis, and experiments based on signals acquired from intensive care unit patients. The results confirm the validity of the proposal suitable to define a novel method for the continuous monitoring of the respiratory mechanics. Since mechanically ventilated patients are supposed to have a central venous catheter in position, the CVP filtering technique can results in an useful clinical approach to estimate the pleural pressure, avoiding additional invasive devices (i.e., balloon-tipped esophageal catheters).

Pulmonary mechanics measurements by respiratory inductive plethysmography and esophageal manometry: Methodology for infants on non-invasive respiratory support.

Infants are commonly supported with non-invasive ventilation (NIV) such as nasal CPAP and high flow nasal cannula (HFNC). These modes utilize a nasal/oral interface precluding use of a traditional airway flow sensor, such as a pneumotachometer (PNT), needed for pulmonary mechanics (PM) measurements. Respiratory Inductive Plethysmography (RIP), when properly calibrated, records tidal volume non-invasively from chest wall movements. Our aim was to integrate RIP into an existing neonatal pulmonary function testing system to measure PM in infants on NIV and to compare measurements of dynamic lung compliance (CL) and resistance (RL) using RIP with those obtained using a PNT. RIP ribcage (RC) and abdominal (ABD) signals were recorded simultaneously with the flow signal from a PNT; transpulmonary pressure was estimated using an esophageal catheter. Two calibration algorithms were applied to obtain RC and ABD scaling factors. Forty PM measurements were performed on 25 infants (GA 31.5±2.9 weeks; birth weight 1598±510 g; median age 7 days). Correlation coefficients for RIP- vs. PNT-based PM were r2 = 0.987 for CL and r2 = 0.997 for RL. From Bland-Altman analysis, the mean bias (±95% CI) between RIP and PNT methods was -0.004±0.021 ml/cmH2O/kg for CL and 0.7±2.9 cmH2O/(L/sec) for RL. The upper, lower limits of agreement (±95% CI) were 0.128±0.037, -0.135±0.037 ml/cmH2O/kg for CL and 18.6±5.1, -17.2±5.1 cmH2O/(L/sec) for RL. Properly calibrated RIP may be a useful tool with sufficient diagnostic accuracy for PM measurements without need for a nasal/oral airflow sensor in infants receiving NIV.

DOZ047.47: Flourish device for treatment of esophageal atresia

Abstract Esophageal atresia (EA) is usually repaired soon after birth. However, there are conditions in which early repair is not possible including prematurity, a large distance between the ends, failed attempt at primary anastomosis, and postoperative complications. Cases in which the ends of the esophagus are not able to be brought together without significant tension, or long-gap esophageal atresia (LGEA), remain a challenge to manage. A variety of techniques have been used to establish esophageal continuity consisting of extensive mobilization, myotomies, esophageal flaps, and traction of the segments. The use of magnets is a nonsurgical alternative for esophageal anastomosis. There have been a few series demonstrating initial success and accomplishment of magnamosis in EA patients. A prospective, single-arm, observational study is currently enrolling patients to evaluate the safety and benefit of the Flourish Device (Cook Medical), a catheter-based, magnetic device used to lengthen the atretic esophageal ends and create an anastomosis. The primary outcomes include stricture requiring dilation or surgery, anastomotic leaks or other adverse events with follow-up for two years. The distance of the esophageal gap is measured with metal probes. All patients require a mature gastrostomy and atretic segments &lt; 4 cm apart. The proximal catheter has a suction port and the distal portion has a channel for feeds. Placement is done under fluoroscopy with anesthesia or sedation. Daily chest radiographs are obtained until union of the magnets occur. Successful anastomosis is identified by saliva in the gastrostomy catheter, feeds in the esophageal catheter, or with a contrast study. One day after confirmation, the magnets may be removed. When the catheters are aligned, the magnets attract. Once the magnets have connected, the tissue between them sloughs off while the outer rim heals establishing the anastomosis. The Flourish device may be particularly useful in patients in whom additional operations are not ideal such as those with congenital anomalies or who have undergone previous operations or complications.

DOZ047.53: Esophageal balloon dilatation for strictures developing after esophageal atresia surgery

Abstract Aim The aim of this study is to evaluate the results of esophageal balloon dilatation (BD) for strictures after esophageal atresia (EA) surgery. Methods Flexible endoscopic BD was done under fluoroscopic and manometric control. The balloon placed in the stricture was inflated by contrast. The target pressure and the diameter were decided in compliance with the manufacturer's directions as well as fluoroscopic guidance. The balloon was kept inflated for 3 minutes. Prospectively collected data over 10 years were retrospectively evaluated. Cure was defined as no need for dilatation during the last 12 months. Results A total of 79 patients with variable diagnoses underwent 481 BD. Forty (51%) had strictures which developed after EA surgery. They underwent 175 (36%) BD (P &lt; 0.05). There were 21 males and 19 females. The atresia was distal fistula type in 31 (77.5%) patients and isolated EA in nine (22.5%). The BD was done for primary esophago-esophageal anastomosis site in 37 patients. The remaining three patients with long gap EA had undergone previous replacement surgery and the BD was done for the proximal esophago-colonic anastomosis. The median age at the time of the first BD was 14 months with 17 (43%) patients below the age of 1 year. The maximal inflation diameter varied between 5–20 mm. Esophageal BD catheters were used in all except two occasions where 5 mm ureteral balloons were used. The median number of BD was four (n = 1–15). Thirty-four (85%) patients underwent more than one BD. A transmural perforation was encountered in one occasion (0.6%) and the patient eventually underwent esophageal replacement surgery with an uneventful outcome. There was no mortality. Fundoplication was done in nine patients. Thirty-three patients (82.5%) were regarded as ‘cure’. Conclusion Esophageal BD is employed for strictures caused by a variety of reasons. Patients with EA comprise a substantial number of cases needing BD and have strictures less resistant to dilatation. The technique employed in this study is advantageous because it enables direct endoscopic visualization of the stricture and both gradual and controlled increase of the dilatation pressure. BD is safe and efficient yet there is a risk of esophageal perforation as in the other dilatation techniques.

Toward a novel semi-invasive activation mapping tool for the diagnosis of supraventricular arrhythmias from the esophagus.

Supraventricular arrhythmia diagnosis using the surface electrocardiogram (sECG) is often cumbersome due to limited atrial signal quality. In some instances, use of esophageal electrocardiography (eECG) may facilitate the diagnosis. Here, we present a novel approach to reconstruct cardiac activation maps from eECG recordings. eECGs and sECGs were recorded from 19 individuals using standard acquisition tools. From the recordings, algorithms were developed to estimate the esophageal ECG catheter's position and to reconstruct high-resolution mappings of the cardiac electric activity projected in the esophagus over time. Esophageal two-dimensional activation maps were created for five healthy individuals and 14 patients suffering from different arrhythmias. The maps are displayed as time-dependent contour plots, which not only show voltage over time as conventional ECGs, but also the location, direction, and projected propagation speed of the cardiac depolarization wavefront in the esophagus. Representative examples of sinus rhythm, atrial flutter, and ventricular pre-excitation are shown. The methodology presented in this report provides a high-resolution view of the cardiac electric field in the esophagus. It is the first step toward a three-dimensional mapping system, which shall be able to reconstruct a three-dimensional view of the cardiac activation from recordings within the esophagus.

The Impact of Cycling Cadence on Respiratory and Hemodynamic Responses to Exercise.

The physiological consequences of freely chosen cadence during cycling remains poorly understood. We sought to determine the effect of cadence on the respiratory and hemodynamic response to cycling exercise. Eleven cyclists (10 males, 1 female; age, 27 ± 6 yr; V˙O2max = 60.8 ± 3.7 mL·kg·min) completed four, 6-min constant-load cycling trials at 10% below their previously determined gas exchange threshold (i.e., 63% ± 5% peak power) while pedaling at 60, 90, and 120 rpm, and a freely chosen cadence (94.3 ± 6.9 rpm) in randomized order. Standard cardiorespiratory parameters were measured and an esophageal electrode balloon catheter was used to assess electromyography of the diaphragm (EMGdi) and the work of breathing (Wb). Leg blood flow index (BFI) was determined on four muscles using near-infrared spectroscopy with indocyanine green dye injections. Oxygen uptake (V˙O2) increased as a function of increasing cadence (all pairwise comparisons, P < 0.05). The EMGdi and Wb were significantly greater at 120 rpm compared with all other conditions (all P < 0.01). Vastus medialis and semitendinosus BFI were significantly greater at 120 rpm compared with 60 and 90 rpm (all P < 0.05). Gastrocnemius BFI was higher at 120 rpm compared with all other cadences (all P < 0.01). No difference in BFI was found in the vastus lateralis (P = 0.06). Blood flow index was significantly correlated with the increase in V˙O2 with increasing cadence in the medial gastrocnemius (P < 0.001) and approached significance in the vastus lateralis (P = 0.09), vastus medialis (P = 0.06), and semitendinosus (P = 0.09). There was no effect of cadence on Borg 0-10 breathing or leg discomfort ratings (P > 0.05). High cadence cycling at submaximal exercise intensities is metabolically inefficient and increases EMGdi, Wb, and leg muscle blood flow relative to slower cadences.

Theuse of an esophageal catheter to check the results of left atrial posterior wall isolation in the treatment of atrial fibrillation.

Left atrial posterior wall isolation (LAPWI) via catheter, surgical, and hybrid techniques is a promising treatment for persistent atrial fibrillation (PersAF). We investigated whether confirmation of LAPWI can be achieved using an esophageal pacing and recording electrode. Patients undergoing PersAF ablation with the intention to achieve LAPWI were enrolled. Two approaches to LAPWI were tested: (1) ablation using endocardial catheter ablation only, and (2) "Staged Hybrid" ablation with thoracoscopic epicardial ablation, followed by endocardial left atrial electrophysiological study and catheter ablation where necessary. Patients enrolled in the study all required further catheter ablation to achieve LAPWI in this group. In both the groups, esophageal recording and esophageal pacing was performed at the start of mapping and electrophysiological study and compared with endocardial electrophysiological findings. This was repeated at the end of the procedure. Twenty patients (16M, four F) were studied. Endocardial electrophysiological study showed that in none of the cases was the posterior left atrial wall electrically isolated at the start of the study. One patient with Barrett's esophagus failed to sense or pace from the esophagus at any point in the study. In the remaining 19/19, esophageal pacing captured the atrial rhythm at the start of the procedure. LAPWI was then achieved in 17/19 using endocardial catheter ablation; retesting at this point showed sensing and capture of the atrium from the esophagus was abolished. In the remainder sensing and capture persisted. Esophageal pacing can be used to confirm or refute electrical isolation of the left atrial posterior wall.

Effects of Age and Sex on Inspiratory Muscle Activation Patterns during Exercise.

To characterize the effects of age, sex, and their interaction on inspiratory muscle activation patterns during exercise. Twenty younger (20-30 yr, n = 10 women) and 20 older (60-80 yr, n = 10 women) subjects performed an incremental cycle exercise test. Electromyography (EMG) of the scalene (EMGsca) and EMG of the sternocleidomastoid (EMGscm) muscles were measured using skin surface electrodes, whereas diaphragm EMG (EMGdi) and esophageal and transdiaphragmatic pressures were measured using an esophageal catheter. Electromyography data were transformed into root mean square with a 100-ms time constant. Esophageal and diaphragmatic pressure-time products were used as indices of total inspiratory muscle pressure production and diaphragmatic pressure production, respectively. At absolute minute ventilations (V˙E), women and older subjects had greater EMGdi than men and younger subjects, respectively (all P < 0.05), but no differences were noted when V˙E was expressed in relative terms (all P > 0.05). Women had greater EMGsca activity than men at absolute and relative levels of V˙E (all P < 0.05). Older subjects had greater EMGsca than younger subjects when V˙E was expressed in relative (all P < 0.05) but not absolute terms (all P > 0.05). At absolute and relative levels of V˙E, women and older subjects had greater EMGscm than men and younger subjects, respectively (all P < 0.05). Women and older subjects had a greater esophageal and diaphragmatic pressure-time products at a V˙E of 70 L·min than men and younger subjects, respectively (both P < 0.05), but no differences were noted when V˙E was expressed in relative terms (all P > 0.05). No significant interactions between age and sex were noted (all P > 0.05). Age and sex significantly affect inspiratory muscle activation patterns during exercise; however, the extent of the effects depends on whether comparisons are made at absolute or relative V˙E.

Value of measuring esophageal pressure to evaluate heart-lung interactions-applications for invasive hemodynamic monitoring.

Evaluation of intrathoracic pressure is the cornerstone of the understanding of heart-lung interactions, but is not easily feasible at the bedside. Esophageal pressure (Pes) has been shown to be a good surrogate for intrathoracic pressure and can be more easily measured using a small esophageal catheter, but is not routinely employed. It can provide crucial information for the study of heart-lung interactions in both controlled and spontaneous ventilation. This review presents the physiological basis, the technical aspects and the value in clinical practice of the measurement of Pes.

Intracranial pressure responsiveness to positive end-expiratory pressure is influenced by chest wall elastance: a physiological study in patients with aneurysmal subarachnoid hemorrhage

BackgroundRespiratory system elastance (ERS) is an important determinant of the responsiveness of intracranial pressure (ICP) to positive end-expiratory pressure (PEEP). However, lung elastance (EL) and chest wall elastance (ECW) were not differentiated in previous studies. We tested the hypothesis that patients with high ECW or a high ECW/ERS ratio have greater ICP responsiveness to PEEP.MethodsAn esophageal balloon catheter was placed to measure esophageal pressure. PEEP was increased from 5 to 15 cmH2O. Airway pressure and esophageal pressure were measured and EL, ECW and ERS were calculated at the two PEEP levels. Patients were classified into either an ICP responder group or a non-responder group based on whether the change of ICP after PEEP adjustment was greater than or less than the median of the overall study population.ResultsThe magnitude of the increase in esophageal pressure (median [interquartile range]) at end-expiratory occlusion was significantly increased in the responder group compared with that in the non-responder group (4.1 [2.7–4.1] versus 2.7 [0.0–2.7] cmH2O, p = 0.033) after PEEP adjustment. ECW and the ECW/ERS ratio were significantly higher in ICP responders than in non-responders at both low PEEP (p = 0.021 and 0.017) and high PEEP (p = 0.011 and 0.025) levels. No significant differences in ERS and EL were noted between the two groups at both PEEP levels.ConclusionsPatients with greater ICP responsiveness to increased PEEP exhibit higher ECW and a higher ECW/ERS ratio, suggesting the importance of ECW monitoring.

Correlation of surface respiratory electromyography with esophageal diaphragm electromyography

ObjectivesTo assess the correlation between surface respiratory electromyography(sEMG) and esophageal diaphragm electromyography(EMGdi) at different levels of neural respiratory drive (NRD). DesignRandomised parallel design controlled trial. SettingThe First Affiliated Hospital of Guangzhou Medical University. Participants15 healthy subjects and 1 severe to very severe stable COPD patients were studied. Interventions15 healthy subjects performed incremental inspiratory threshold loading (ILT) and 15 stable COPD patients underwent noninvasive positive pressure ventilation (NPPV).The correlation between EMGdi and sEMG at different NRD levels was analyzed. EMGdi was performed with a multi-pair esophageal electrode catheter; sEMG were was performed by surface diaphragm EMG(located in right anterior axillary line and left anterior axillary line respectively expressed as sEMGdi(r) andsEMGdi(l))、surface parasternal EMG(sEMGpara),and surface sternocleidomastoid EMG(sEMGsc).Signals were normalized using the peak EMG expressed as EMG%max. Primary and secondary outcome measuresThe mean ± standard deviation resting EMGdi%max was higher in patients with COPD than in healthy subjects (57.26%±15.45% vs13.64% ±4.96%, respectively; p < 0.001).During ILT and NPPV, EMGdi was correlated with sEMGdi (r), sEMGdi (1), sEMGpara and sEMGsc (r = 0.90, 0.87, 0.90, 0.90 and r = 0.92, 0.83, 0.92 and 0.71, respectively; all P < 0.001). ConclusionA strong relationship is present between NRD measured by EMGdi%max and NRD measured by sEMG%max. sEMG%max serves as a non-invasive marker of NRD.