Swallowing Activity Assessed by Ambulatory Impedance-pH Monitoring Predicts Awake and Asleep Periods at Night

INTRODUCTION: Voluntary muscle activity, including swallowing, decreases during the night. The association between nocturnal awakenings and swallowing activity is under-researched with limited information on the frequency of swallows during awake and asleep periods. AIM: The aim of this study was to assess nocturnal swallowing activity and identify a cut-off predicting awake and asleep periods. METHODS: Patients undergoing impedance-pH monitoring as part of GERD work-up were asked to wear a wrist activity detecting device (Actigraph(®)) at night. Swallowing activity was quantified by analysing impedance changes in the proximal esophagus. Awake and asleep periods were determined using a validated scoring system (Sadeh algorithm). Receiver operating characteristics (ROC) analyses were performed to determine sensitivity, specificity and accuracy of swallowing frequency to identify awake and asleep periods. RESULTS: Data from 76 patients (28 male, 48 female; mean age 56 ± 15 years) were included in the analysis. The ROC analysis found that 0.33 sw/min (i.e. one swallow every 3 min) had the optimal sensitivity (78 %) and specificity (76 %) to differentiate awake from asleep periods. A swallowing frequency of 0.25 sw/min (i.e. one swallow every 4 min) was 93 % sensitive and 57 % specific to identify awake periods. A swallowing frequency of 1 sw/min was 20 % sensitive but 96 % specific in identifying awake periods. Impedance-pH monitoring detects differences in swallowing activity during awake and asleep periods. Swallowing frequency noticed during ambulatory impedance-pH monitoring can predict the state of consciousness during nocturnal periods

Rainfall input, throughfall and stemflow of nutrients in a central African rain forest dominated by ectomycorrhizal trees

Incident rainfall is a major source of nutrient input to a forest ecosystem and the consequent throughfall and stemflow contribute to nutrient cycling. These rain-based fluxes were measured over 12 mo in two forest types in Korup National Park, Cameroon, one with low (LEM) and one with high (HEM) ectomycorrhizal abundances of trees. Throughfall was 96.6 and 92.4% of the incident annual rainfall (5370 mm) in LEM and HEM forests respectively; stemflow was correspondingly 1.5 and 2.2%. Architectural analysis showed that ln(funneling ratio) declined linearly with increasing ln(basal area) of trees. Mean annual inputs of N, P, K, Mg and Ca in incident rainfall were 1.50, 1.07, 7.77, 5.25 and 9.27 kg ha(-1), and total rain-based inputs to the forest floor were 5.0, 3.2, 123.4, 14.4 and 37.7 kg ha-1 respectively. The value for K is high for tropical forests and that for N is low. Nitrogen showed a significantly lower loading of throughfall and stemflow in HEM than in LEM forest, this being associated in the HEM forest with a greater abundance of epiphytic bryophytes which may absorb more N. Incident rainfall provided c. 35% of the gross input of P to the forest floor (i. e., rain-based plus small litter inputs), a surprisingly high contribution given the sandy P-poor soils. At the start of the wet season leaching of K from the canopy was particularly high. Calcium in the rain was also highest at this time, most likely due to washing off of dry-deposited Harmattan dusts. It is proposed that throughfall has an important `priming' function in the rapid decomposition of litter and mineralization of P at the start of the wet season. The contribution of P inputted from the atmosphere appears to be significant when compared to the rates of P mineralization from leaf litter.

Local environmental knowledge: a key input for the sustainable development of Andean mountain communities

Local knowledge is crucial to both human development and environmental conservation. This is especially the case in mountain regions, where a combination of remoteness, harsh climatic conditions, rich cultural heritage, and high biological diversity has led to the development of complex local environmental knowledge systems. In the Andes for instance, rural populations mainly rely on their own environmental knowledge to ensure their food security and health. Recent studies conducted within Quechua communities in Peru and Bolivia showed that this knowledge was both persistent and dynamic, and that it responded to socio-economic and environmental changes through cultural resistance and adaptation. As this paper argues, combining local knowledge and so-called scientific knowledge – especially in development projects – can lead to innovative solutions to the socio-environmental challenges facing mountain communities in our globalized world. Based on experiences from the Andes, this paper will provide concrete recommendations to policymakers and practitioners for integrating local knowledge into development and natural resource management initiatives.

Determination of respiratory gas flow by electrical impedance tomography in an animal model of mechanical ventilation

Background A recent method determines regional gas flow of the lung by electrical impedance tomography (EIT). The aim of this study is to show the applicability of this method in a porcine model of mechanical ventilation in healthy and diseased lungs. Our primary hypothesis is that global gas flow measured by EIT can be correlated with spirometry. Our secondary hypothesis is that regional analysis of respiratory gas flow delivers physiologically meaningful results. Methods In two sets of experiments n = 7 healthy pigs and n = 6 pigs before and after induction of lavage lung injury were investigated. EIT of the lung and spirometry were registered synchronously during ongoing mechanical ventilation. In-vivo aeration of the lung was analysed in four regions-of-interest (ROI) by EIT: 1) global, 2) ventral (non-dependent), 3) middle and 4) dorsal (dependent) ROI. Respiratory gas flow was calculated by the first derivative of the regional aeration curve. Four phases of the respiratory cycle were discriminated. They delivered peak and late inspiratory and expiratory gas flow (PIF, LIF, PEF, LEF) characterizing early or late inspiration or expiration. Results Linear regression analysis of EIT and spirometry in healthy pigs revealed a very good correlation measuring peak flow and a good correlation detecting late flow. PIFEIT = 0.702 · PIFspiro + 117.4, r2 = 0.809; PEFEIT = 0.690 · PEFspiro-124.2, r2 = 0.760; LIFEIT = 0.909 · LIFspiro + 27.32, r2 = 0.572 and LEFEIT = 0.858 · LEFspiro-10.94, r2 = 0.647. EIT derived absolute gas flow was generally smaller than data from spirometry. Regional gas flow was distributed heterogeneously during different phases of the respiratory cycle. But, the regional distribution of gas flow stayed stable during different ventilator settings. Moderate lung injury changed the regional pattern of gas flow. Conclusions We conclude that the presented method is able to determine global respiratory gas flow of the lung in different phases of the respiratory cycle. Additionally, it delivers meaningful insight into regional pulmonary characteristics, i.e. the regional ability of the lung to take up and to release air.

Association Between Baseline Impedance Values and Response Proton Pump Inhibitorsin Patients With Heartburn

BACKGROUND & AIMS: Esophageal impedance measurements have been proposed to indicate the status of the esophageal mucosa, and might be used to study the roles of the impaired mucosal integrity and increased acid sensitivity in patients with heartburn. We compared baseline impedance levels among patients with heartburn who did and did not respond to proton pump inhibitor (PPI) therapy, along with the pathophysiological characteristics of functional heartburn (FH). METHODS: In a case-control study, we collected data from January to December 203 on patients with heartburn and normal findings from endoscopy who were not receiving PPI therapy and underwent impedance pH testing at hospitals in Italy. Patients with negative test results were placed on an 8-week course of PPI therapy (84 patients received esomeprazole and 36 patients received pantoprazole). Patients with more than 50% symptom improvement were classified as FH/PPI responders and patients with less than 50% symptom improvement were classified as FH/PPI nonresponders. Patients with hypersensitive esophagus and healthy volunteers served as controls. In all patients and controls, we measured acid exposure time, number of refluxes, baseline impedance, and swallow-induced peristaltic wave indices. RESULTS: FH/PPI responders had higher acid exposure times, numbers of reflux events, and acid refluxes compared with FH/PPI nonresponders (P < .05). Patients with hypersensitive esophagus had mean acid exposure times and numbers of reflux events similar to those of FH/PPI responders. Baseline impedance levels were lower in FH/PPI responders and patients with hypersensitive esophagus, compared with FH/PPI nonresponders and healthy volunteers (P < .001). Swallow-induced peristaltic wave indices were similar between FH/PPI responders and patients with hypersensitive esophagus. CONCLUSIONS: Patients with FH who respond to PPI therapy have impedance pH features similar to those of patients with hypersensitive esophagus. Baseline impedance measurements might allow for identification of patients who respond to PPIs but would be classified as having FH based on conventional impedance-pH measurements.

Evaluating Esophageal Bolus Transit by Impedance Monitoring

The function of the esophagus is transporting nutrients from the oropharyngeal cavity to the stomach. This is achieved by coordinated contractions and relaxation of the tubular esophagus and the upper and lower esophageal sphincter. Multichannel intraluminal impedance monitoring offers quantification of esophageal bolus transit and/or retention without the use of ionizing radiation. Combined with conventional or high-resolution manometry, impedance measurements complement the quantification of esophageal body contraction and sphincter relaxation, offering a more comprehensive evaluation of esophageal function. Further studies evaluating the utility of quantifying bolus transit will help clarify the role and position of impedance measurements.

Gastro-oesophageal reflux is common in oligosymptomatic patients with dental erosion: A pH-impedance and endoscopic study.

Background: Dental erosion is a complication of gastro-oesophageal reflux disease (GORD) according to the Montreal consensus statement. However, GORD has not been comprehensively characterized in patients with dental erosions and pH-impedance measures have not been reported. Objectives: Characterize GORD in patients with dental erosions using 24-h multichannel intraluminal pH-impedance measurements (pH-MII) and endoscopy. Methods: This single-centre study investigated reflux in successive patients presenting to dentists with dental erosion using pH-MII and endoscopy. Results: Of the 374 patients, 298 (80%) reported GORD symptoms <2 per week, 72 (19%) had oesophagitis and 59 (16%) had a hiatal hernia. In the 349 with pH-MII the mean percentage time with a pH <4 (95% CI) was 11.0 (9.3–12.7), and 34.4% (31.9–36.9) for a pH <5.5, a critical threshold for dental tissue. The mean numbers of total, acidic and weakly acidic reflux episodes were 71 (63–79), 43 (38–49) and 31 (26–35), respectively. Of the reflux episodes, 19% (17–21) reached the proximal oesophagus. In 241 (69%) patients reflux was abnormal using published normal values for acid exposure time and reflux episodes. No significant associations between the severity of dental erosions and any reflux variables were found. The presence of GORD symptoms and of oesophagitis or a hiatal hernia was associated with greater reflux, but not with increased dental erosion scores. Conclusions: Significant oligosymptomatic gastro-oesophageal reflux occurs in the majority of patients with dental erosion. The degree of dental erosion did not correlate with any of the accepted quantitative reflux indicators. Definition of clinically relevant reflux parameters by pH-MII for dental erosion and of treatment guidelines are outstanding. Gastroenterologists and dentists need to be aware of the widely prevalent association between dental erosion and atypical GORD.

Manually calculated oesophageal bolus clearance time increases in parallel with reflux severity at impedance-pH monitoring.

BACKGROUND Oesophageal clearance has been scarcely studied. AIMS Oesophageal clearance in endoscopy-negative heartburn was assessed to detect differences in bolus clearance time among patients sub-grouped according to impedance-pH findings. METHODS In 118 consecutive endoscopy-negative heartburn patients impedance-pH monitoring was performed off-therapy. Acid exposure time, number of refluxes, baseline impedance, post-reflux swallow-induced peristaltic wave index and both automated and manual bolus clearance time were calculated. Patients were sub-grouped into pH/impedance positive (abnormal acid exposure and/or number of refluxes) and pH/impedance negative (normal acid exposure and number of refluxes), the former further subdivided on the basis of abnormal/normal acid exposure time (pH+/-) and abnormal/normal number of refluxes (impedance+/-). RESULTS Poor correlation (r=0.35) between automated and manual bolus clearance time was found. Manual bolus clearance time progressively decreased from pH+/impedance+ (42.6s), pH+/impedance- (27.1s), pH-/impedance+ (17.8s) to pH-/impedance- (10.8s). There was an inverse correlation between manual bolus clearance time and both baseline impedance and post-reflux swallow-induced peristaltic wave index, and a direct correlation between manual bolus clearance and acid exposure time. A manual bolus clearance time value of 14.8s had an accuracy of 93% to differentiate pH/impedance positive from pH/impedance negative patients. CONCLUSIONS When manually measured, bolus clearance time reflects reflux severity, confirming the pathophysiological relevance of oesophageal clearance in reflux disease.

Natural Hedging of Exchange Rate Risk: The Role of Imported Input Prices

In this paper, we estimate ERPT into imported input prices and export prices using disaggregated quarterly trade data for Switzerland over 2004–2011. We find evidence for high pass-through rates into imported input prices. This demonstrates the effectiveness of natural hedging. On the export side, ERPT exhibits substantial sectoral heterogeneity and changes in imported input costs are not transmitted to foreign consumers in most cases. This suggests the use of cheaper imported inputs to offset adverse effects of currency appreciation on export profit margins.