Inflation volume-balloon diameter and inflation pressure-balloon diameter characteristics of commonly used bronchial blocker balloons for single-lung ventilation in children.

BACKGROUND: Balloon-tipped bronchial blocker catheters are widely used in pediatric thoracic anesthesia to establish single-lung ventilation. In clinical practice, their balloons demonstrate sudden expansion when inflated with air. In addition, there are concerns related to the high inflation pressures required to expand the balloons. METHODS: This in vitro study assessed inflation volume- and inflation pressure-balloon diameter characteristics of the Fogarty arterial embolectomy catheters and Arndt endobronchial blockers. Balloon diameters were photographically assessed during unrestricted volume- and pressure-guided inflation, using air up to the maximum allowed inflation volume as indicated by the manufacturers. Inflation pressures required to open the blocker balloons and inflation pressures needed to expand them to maximum indicated diameter were measured. RESULTS: Volume-guided inflation demonstrated a late acute rise in diameter in Fogarty blocker balloons, whereas in the Arndt endobronchial blocker balloons almost linear inflation volume-to-diameter characteristics were observed. Pressure-guided inflation on the other hand demonstrated low-volume, high-pressure characteristics in the Fogarty blocker balloons, with inflation pressures required to expand the balloons to maximum diameters ranging from (mean (SD)) 636 (75) to 947 (152) cmH2 O. The inflation pressures required to open the Fogarty blocker balloons were even >1000 cmH2 O. Inflation pressures required to expand the 5 F, 7 F, and 9 F Arndt endobronchial blocker balloons to maximum indicated diameter were much lower, namely at 218 (15), 252 (28), and 163 (8) cmH2 O. CONCLUSION: Based on these study findings, the balloons of Fogarty arterial embolectomy catheters represent high-pressure devices and do not permit stepwise controlled bronchial blockage. The Arndt endobronchial blockers have some advantages over the Fogarty blocker devices, but also represent high-pressure equipment and must be used with caution and limited duration. Manufacturers are asked to design pediatric endobronchial blocker catheters with truly high-volume, low-pressure balloons in accordance to age-related pediatric airway dimensions.

Insertion of cuff inflation line into pediatric tracheal tubes related to oral and nasal tracheal intubation depth.

BACKGROUND: In clinical practice, the cuff inflation line of cuffed pediatric tracheal tubes often interferes with securing tracheal tubes. METHODS: The insertion site of the cuff inflation lines and the lengths of four different brands and nine sizes of commonly used cuffed pediatric tracheal tubes were measured and compared in vitro with oral and nasotracheal intubation depths as calculated by different formulas for pediatric patients aged from birth to 16 years. Motoyama's recommendation was used for age-related size selection of cuffed pediatric tracheal tubes. RESULTS: The proportion of the distance from the tracheal tube tip to the insertion site of the cuff inflation line varied considerably between the tracheal tubes (Microcuff: 48.5-60.7%; Parker: 48.7-73.2%; Ruesch: 59.1-77.8%; and Shiley: 46.0-60.3%). Using different formulas for oral or nasotracheal intubation depth, the insertion site of the cuff inflation line was placed within the oral or nasal cavity or within an area 1 cm beyond the teeth or the nostrils in almost all tracheal tubes tested. Positioning the insertion site 2 cm from the proximal end of the tracheal tubes resulted in a cuff line-free tube area of ≥1 cm in all orally and almost in all nasally inserted tracheal tubes, considering maximum recommended tracheal intubation depths. CONCLUSION: The cuff inflation line in almost all commonly used cuffed pediatric tracheal tubes interferes with securing the tracheal tube due to its insertion site into the tracheal tube. This potentially carries the risk of kinking, obstruction, or damage to the cuff inflation line with ensuing failure to deflate or inflate the cuff. The proposed position of the insertion of the cuff inflation line 2 cm from the proximal end of the tracheal tube would ensure a 1-cm-wide cuff line-free circular area beyond the oral or nasal cavity in nearly all assessed tracheal tube sizes.

Dimensional compatibility of rigid ventilating bronchoscopes with pediatric airway anatomy using different recommendations for age-related sizing-A bench study.

BACKGROUND: Appropriate size selection of pediatric rigid bronchoscopes is fundamental to avoidance of airway trauma and to a high success rate with the first intubation attempt. The aim of the present study was to compare the outer diameters of pediatric rigid bronchoscopes with the anatomical data on the pediatric airway. METHODS: Outer diameters (OD) of pediatric rigid ventilating bronchoscopes as given by the manufacturer were compared with published computed tomography internal diameters (ID) of the cricoid outlet, the trachea as well as the left and right proximal mainstem bronchus, using six published recommendations for age-related size selection. The ratios between a specific OD and ID were calculated and given as percentage values (%) for lower and upper age ranges. RESULTS: Nominal sized 2.5, 3, 3.5, 3.7, 4, 4.5, 5, and 6 rigid bronchoscopes were included. In five recommendations, the rigid bronchoscopes' OD was larger than the internal cricoid diameter in the upper age range, whereas in one recommendation the ratio (OD rigid bronchoscope to ID of cricoid) ranged between 77% and 90% for the upper age and between 95% and 109% for the lower age range. In only one of the six recommendations was the rigid bronchoscope OD larger than the tracheal ID. Ratios for the left and right proximal mainstem bronchus ranged from 70% to 146% for the upper and from 78% to 156% for the lower age range, with the highest ratios for the left proximal mainstem bronchus. CONCLUSION: Based on this in vitro study, most of the recommendations analyzed result in a balanced fit of rigid bronchoscopes within the cricoid. Since the left mainstem bronchus is considerably smaller than the cricoid, any insertion on this level will require careful endoscopic guidance to avoid damage to the left mainstem bronchus.

Simulated dimensional compatibility of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children.

BACKGROUND: Cuffed tracheal tubes have recently been recommended for selective endobronchial intubation to establish single-lung ventilation even in smaller children. This implies that, compared with uncuffed tracheal tubes, the cuffed tracheal tubes selected will be smaller and therefore have a shorter length. We hypothesized that cuffed tracheal tubes might be of insufficient length for selective endobronchial intubation if the tube cuff were fully immersed in the left or right mainstem bronchus. METHODS: The distance from the proximal end of the tracheal tube to the upper border of the cuff in cuffed tracheal tubes and to the upper margin of the Murphy eye in uncuffed tracheal tubes, respectively, was assessed in sizes 3.0-7.0 mm internal diameter. The raw data sets of two previously performed studies obtained from 337 children aged from birth to 16 years, including the distances "teeth to tracheal tube tip" and "tracheal tube tip to carina," were used to calculate age-, weight-, and height-related data for the distance from "teeth to carina." Tracheal tube dimensions were compared with age-related distances from "teeth to carina," applying published recommendations for the selection of uncuffed and cuffed tracheal tubes for selective endobronchial intubation in children. RESULTS: The differences between the length of the age-related tracheal tube and the tracheal tube insertion length required to guarantee full insertion of the tracheal tube cuff or the Murphy eye within the mainstem bronchus ranged from -3.5 to 52.6 mm in cuffed tracheal tubes and from 42.3 to 83.3 mm in uncuffed tracheal tubes. CONCLUSIONS: For many age groups of patients requiring selective endobronchial intubation, the lengths of cuffed tracheal tubes, in contrast to those of uncuffed tracheal tubes, were revealed to be critically short for safe taping outside the oral cavity with the cuff placed completely within the right or left mainstem bronchus.

Cuffed pediatric endotracheal tubes-Outer cuff diameters compared to age-related airway dimensions.

BACKGROUND: Reliable sealing of the pediatric airway requires appropriately sized tracheal tube cuffs. The aim of this study was to compare residual cuff diameters of pediatric tracheal tubes with pediatric airway dimensions. METHODS: Cuff diameters of five different brands of locally marketed pediatric cuffed tracheal tubes with internal diameters of 3.0-7.0 mm were measured at a cuff pressure of 20 cm H2 O and compared with cuff diameters indicated by their manufacturers. The latter values were compared to tracheal dimensions using the Motoyama and Khine formulas for cuffed tracheal tube size selection. RESULTS: There is considerable heterogeneity in cuff diameters among pediatric tracheal tube brands, except for two brands from different manufacturers (Halyard and Parker Medical) which were identically designed. Cuffs made from polyurethane revealed fewer differences (91%-118%) between measured and manufacturer-indicated values for outer cuff diameters than did those made from polyvinylchloride (91%-146%). Particularly in smaller sized tracheal tubes, cuffs did not reach 100% of the tracheal lateral diameter, while others were oversized in larger tracheal tubes, independent of the two formulas used for cuffed tracheal tube size selection. Cuff diameters indicated by the manufacturer corresponded to 86%-188% of the median and 68%-157% of the maximum mid-tracheal lateral diameter of the corresponding upper age range. CONCLUSION: Our findings show that many of the cuff diameters of currently marketed tracheal tube brands lack an age-related anatomical rationale. A proposal for age-related anatomically based cuff diameters is provided for both recommendations for cuffed tracheal tube size selection in children.

Dimensional compatibility of balloon-tipped bronchial blockers with the pediatric airway anatomy using different recommendations for age-related size selection.

BACKGROUND: Age-related recommendations for size selection of bronchial blocker devices are based on a few dated anatomical autopsy and radiological studies determining lower airway dimensions in children. These recommendations are based on anterior-posterior internal bronchial diameters, which are smaller than the more relevant lateral internal bronchial diameters. METHODS: Outer diameters of bronchial blocker balloons inflated with the maximum recommended volume of air were compared to age-related lateral internal bronchial diameters of left and right proximal mainstem bronchi using five different recommendations for age-related size selection of bronchial blocker equipment in children published in the literature. RESULTS: The ratio of outer bronchial blocker diameters inflated with the maximal recommended volume of air to the median lateral internal diameters of the proximal mainstem bronchus ranged from 71.4% to 181.8% for the left side and from 61.7% to 162.6% for the right side. There were many settings where the blocker diameters did not reach the median lateral internal diameters of the proximal mainstem bronchus. This was more often observed for the right than for the left side (37 vs 22 settings). CONCLUSION: This analysis demonstrates that irrespective of the recommendation for size selection used, neither the two balloon-tipped vascular catheters included nor the Arndt endobronchial blockers are ideal for lung isolation in children are compared with the age-related relevant dimensions of pediatric airway anatomy. A redesign of bronchial blocker equipment with age-related anatomically based high-volume, low-pressure blocker balloons made from ultrathin membranes and with smaller catheters would be desirable.

Fiberoptic intubation of severely obese patients through supraglottic airway: A prospective, randomized trial of the Ambu® AuraGain™ laryngeal mask vs the i-gel™ airway.

INTRODUCTION: Airway management in severely obese patients remains a challenging issue for anaesthetists and may lead to life-threatening situations. Supraglottic airway devices, such as the i-gel™ or the AuraGain™, were developed, with the possibility to ventilate the patient or use them as a conduit for endotracheal intubation. METHODS: In our randomized prospective trial, we hypothesized a 10 seconds faster fiberoptic trans-device intubation time through the AuraGain™ laryngeal mask compared to the i-gel™ laryngeal mask in severely obese patients. We randomly assigned 44 patients to the AuraGain or i-gel group and measured trans-device intubation time after 5 minutes of successful ventilation through the device. Secondary parameters relating to the trans-device intubation success, oropharyngeal leak pressure, and parameters regarding insertion of the supraglottic airway devices were measured. Postoperative airway morbidity was determined 5 hours after surgery. RESULTS: Mean (SD) intubation time was 55.7 (5.8) seconds for the AuraGain™ vs 54.1 (8.5) for i-gel™ mask (95% CI -2.7 to 5.9; P = 0.474), respectively, on a mean body mass index (BMI) of 39.4 kg/m2 in the AuraGain™ group vs 38.9 kg/m2 in i-gel™ group. No difference could be found in the other studied parameters. CONCLUSIONS: Time for intubation through both supraglottic airway devices was similar. Attributed to fast possibility of securing the airway with both supraglottic airway devices, we believe that both, AuraGain™ and i-gel™, can be a good alternative in the airway management in obese patients.

Pediatric airway dimensions-A summary and presentation of existing data.

BACKGROUND: Age-related pediatric airway dimension reference values for cricoid, tracheal, and bronchial diameters as well as tracheal and bronchial lengths are essential for distinguishing normal from pathological airway findings and for manufacturing and selecting appropriately sized airway equipment. AIM: The aim of this work was to summarize and present existing pediatric airway dimension data for the larynx, trachea, and main stem bronchi from fetus to adolescence. METHODS: A systematic literature search was carried out using PubMed, Scopus, Embase, and Google Scholar. Publications containing original data on pediatric airway dimensions as mean or median in tabular form and spanning narrow age groups of 1 or 2 years were included in our study. Original data such as diameters, lengths, and cross-sectional areas of trachea, cricoid, left and right main bronchi in fetuses and children were collected and presented as figures. RESULTS: Pediatric airway dimension data were gathered and compiled from 15 studies fulfilling the inclusion criteria. Data were obtained from different measurement methods such as autopsy, chest X-ray, computed tomography, magnetic resonance imaging, rigid and flexible bronchoscopy as well as ultrasound examinations. There was considerable variation among age-related data due to biologic heterogeneity, different presentation of data, different definitions, and various measurement techniques. CONCLUSION: This investigation revealed heterogeneous data on pediatric airway dimensions, making it impossible to compile them into standard reference values for airway dimensions. New studies with structured and standardized measurements and data presentation in large populations of children are required to provide more valid pediatric airway dimension data.

Lower airway dimensions in pediatric patients-A computed tomography study.

BACKGROUND: The aim of this study was to obtain lower airway dimensions in children by means of computed tomography (CT). METHODS: Chest CT scans from 195 pediatric patients (118 boys/77 girls) aged 0.04-15.99 years were analyzed. Tracheal and bronchial lengths, anterior-posterior and lateral diameters, as well as cross-sectional area were assessed at the following levels: mid trachea, right proximal and distal bronchus, proximal bronchus intermedius, and left proximal and distal bronchus. Mediastinal angles of tracheal bifurcation were measured. Data were analyzed by means of linear and polynomial regression plots. RESULTS: The strongest correlations were found between tracheal and bronchial diameters and age as well as between tracheal and bronchial lengths and body length. All measured airway parameters correlated poorly to body weight. Bronchial angles revealed no association with patient's age, body length, or weight. CONCLUSION: This comprehensive anatomical database of lower airway dimensions demonstrates that tracheal and bronchial diameters correlate better to age, and that tracheal and bronchial length correlate better to body length. All measured airway parameters correlated poorly to body weight.

Effect of Lanz pressure regulating valve on self-sealing mechanism and air leakage across the tracheal tube cuffs in a benchtop model.

BACKGROUND: The aim of the present study was to investigate the effect of the Lanz system on air sealing by self-inflation in high volume-low pressure (HVLP) tube cuffs. METHODS: In vitro tracheal air sealing was studied in HVLP tracheal tube cuffs (internal diameter [ID] 8.0 mm) made from polyurethane ([PU] Seal Guard tracheal tube, Covidien, Athlone, Ireland) and from polyvinylchloride ([PVC] HiLo tracheal tube, Covidien) with and without Lanz pressure regulating valve. Tube cuffs were placed in a vertical 22 mm ID artificial trachea and inflated to 5, 10, 15, 20, 25, or 30 cm H2O cuff pressures. Pressure control ventilation with peak inspiratory pressures (PIPs) of 20 or 25 cm H2O was applied and air leakage was assessed spirometrically as the ratio of expiratory to inspiratory tidal volumes. Nonparametric Mann-Whitney test was applied to compare the air leakage with and without Lanz system for both cuff types at each cuff pressure and PIP (P < .05). RESULTS: The PVC tube cuffs with Lanz system resulted in significant air leakage at both 20 and 25 cm H2O PIP as compared to those without the Lanz system, especially at cuff pressures lower than the preset PIP (P < .05). Although PU tube cuffs with Lanz system showed reduced air sealing when compared with cuffs without Lanz, the difference was not statistically significant. CONCLUSION: Cuff pressure compensation with the Lanz system during cyclic respiratory pressure changes interferes with the self-sealing mechanism in HVLP tube cuffs at cuff pressures lower than PIP level. This results in larger air leak across tube cuffs particularly in tube cuffs made from PVC.

Mutations in SLC6A19, encoding B0AT1, cause Hartnup disorder.

Hartnup disorder, an autosomal recessive defect named after an English family described in 1956 (ref. 1), results from impaired transport of neutral amino acids across epithelial cells in renal proximal tubules and intestinal mucosa. Symptoms include transient manifestations of pellagra (rashes), cerebellar ataxia and psychosis. Using homozygosity mapping in the original family in whom Hartnup disorder was discovered, we confirmed that the critical region for one causative gene was located on chromosome 5p15 (ref. 3). This region is homologous to the area of mouse chromosome 13 that encodes the sodium-dependent amino acid transporter B(0)AT1 (ref. 4). We isolated the human homolog of B(0)AT1, called SLC6A19, and determined its size and molecular organization. We then identified mutations in SLC6A19 in members of the original family in whom Hartnup disorder was discovered and of three Japanese families. The protein product of SLC6A19, the Hartnup transporter, is expressed primarily in intestine and renal proximal tubule and functions as a neutral amino acid transporter.

Influence of bupivacaine injection dose rate on cardiovascular depression, subsequent hemodynamic course, and related bupivacaine plasma levels in piglets.

PURPOSE: Systemic local anesthetic (LA) toxicity resulting from inadvertent intravascular injection of LA is a rare but potentially fatal event. Early recognition of intravascular injection and approaches to improve therapeutic safety are required. This study investigated the influence of intravascular injection dose rate of bupivacaine on bupivacaine plasma levels and timing of LA-induced cardiovascular compromise. METHODS: Forty-five piglets, anesthetized with sevoflurane, were randomized into three groups. Bupivacaine was intravenously infused at a rate of 1, 4, or 16 mg/kg/min (groups A, B, and C, respectively) until mean arterial pressure (MAP) dropped to 50% of initial value. Thereafter, bupivacaine infusion was stopped and spontaneous hemodynamic course was observed. Time to MAP 50%, amount of bupivacaine infused, bupivacaine plasma level at infusion stop, spontaneous survivors, or time from bupivacaine stop to circulatory arrest were recorded. RESULTS: Median time to MAP 50% was 297, 119, and 65 s, respectively, in groups A, B, and C (P < 0.001). Median corresponding total amounts of bupivacaine infused were 5.0, 7.8, and 17.0 mg/kg (P < 0.01), and median bupivacaine plasma levels were 53.8, 180.0, and 439.8 µmol/l (P < 0.001). Five of 15 piglets in group A recovered spontaneously; in groups B and C, all animals died within 120 and 21 s, respectively. CONCLUSION: Higher dose rates of bupivacaine showed much higher plasma bupivacaine levels related to absolute infused dose at MAP 50% and were associated with an increased mortality. Slow administration of LA is recommended to allow timely detection and stopping of inadvertent intravascular administration.

Tracheal fluid leakage in benchtop trials: comparison of static versus dynamic ventilation model with and without lubrication.

PURPOSE: Longitudinal folds in tracheal tube (TT) cuffs cause leakage of pooled secretions past the tube cuff, and the most common in vitro method to test the efficacy of a new tube is a benchtop model using an artificial rigid trachea. This study compared the potential of a static and dynamic ventilation benchtop model and cuff lubrication in testing the tracheal sealing properties of a given TT cuff. METHODS: Static trial Six brands of 7.5 mm internal diameter (ID) cuffed TT (n = 8) with high volume-low pressure cuffs were inflated in an artificial trachea (18 mm ID) without and with lubrication. Dynamic trial The same tube cuffs, without lubrication, were subjected to positive pressure ventilation (PPV) + positive end-expiratory pressure (PEEP) of 5cmH(2)O or to PPV alone (without PEEP) or to PEEP alone (without PPV). Clear water (5 ml) was placed above the tube cuff, and fluid leakage (ml) was measured up to 60 min. RESULTS: Gel lubrication, PEEP alone and PPV + PEEP completely prevented fluid leakage across the tube cuffs in all six TT brands tested within 60 min when compared to the static unlubricated model (0% leak versus 100% leak; P < 0.01). Fluid leakage in the static unlubricated model and the PPV group was 1.38-4.76 ml and 0.23-4.47 ml, respectively. CONCLUSION: Gel lubrication, PEEP alone, and PPV + PEEP in the benchtop model had a much stronger protective effect than PPV alone on fluid leakage. Studies testing the fluid sealing efficiency of tube cuffs might be more conclusive in a static benchtop model without lubrication than in a dynamic model.

Airway dimensions from fetal life to adolescence-A literature overview.

BACKGROUND: Data on airway dimensions in pediatric patients are important for proper selection of pediatric airway equipment such as endotracheal tubes, double-lumen tubes, bronchial blockers, or stents. The aim of the present work was to provide a synopsis of the available data on pediatric airway dimensions. METHODS: A systematic literature search was carried out in the PubMed database, Scopus, Embase, Web of Science, Prisma, and Google Scholar and secondarily completed by a reference search. Based on inclusion and exclusion criteria, a final selection of 109 studies with data on pediatric airway dimensions published from 1923 to 2018 were further analyzed. RESULTS: Six different airway measurement methods were identified. They included anatomical examinations, chest X-ray, computed tomography, magnetic resonance tomography, bronchoscopy, and ultrasound. Anatomical studies were more abundant compared to other methods. Data provided were very heterogeneously presented and powered. In addition, due to different study conditions, they are hardly comparable. Among all, anatomical and computer tomography studies are thought to provide the most reliable data. Ultrasound is an upcoming technique to estimate airway parameters of fetus and premature infants. There was, in general, a lack of comprehensive studies providing a complete range of airway dimensions in larger groups of patients from birth to adolescence. CONCLUSIONS: This work revealed a large heterogeneity of studies providing data on pediatric airway dimensions, making it impossible to compare, or assemble them to normograms for clinical use. Comprehensive studies in large population of children are needed to provide full range nomograms on pediatric airway dimensions.

An amino acid transporter involved in gastric acid secretion.

Gastric acid secretion is regulated by a variety of stimuli, in particular histamine and acetyl choline. In addition, dietary factors such as the acute intake of a protein-rich diet and the subsequent increase in serum amino acids can stimulate gastric acid secretion only through partially characterized pathways. Recently, we described in mouse stomach parietal cells the expression of the system L heteromeric amino acid transporter comprised of the LAT2-4F2hc dimer. Here we address the potential role of the system L amino acid transporter in gastric acid secretion by parietal cells in freshly isolated rat gastric glands. RT-PCR, western blotting and immunohistochemistry confirmed the expression of 4F2-LAT2 amino acid transporters in rat parietal cells. In addition, mRNA was detected for the B(0)AT1, ASCT2, and ATB(0+) amino acid transporters. Intracellular pH measurements in parietal cells showed histamine-induced and omeprazole-sensitive H+-extrusion which was enhanced by about 50% in the presence of glutamine or cysteine (1 mM), two substrates of system L amino acid transporters. BCH, a non-metabolizable substrate and a competitive inhibitor of system L amino acid transport, abolished the stimulation of acid secretion by glutamine or cysteine suggesting that this stimulation required the uptake of amino acids by system L. In the absence of histamine glutamine also stimulated H+-extrusion, whereas glutamate did not. Also, phenylalanine was effective in stimulating H+/K+-ATPase activity. Glutamine did not increase intracellular Ca2+ levels indicating that it did not act via the recently described amino acid modulated Ca2+-sensing receptor. These data suggest a novel role for heterodimeric amino acid transporters and may elucidate a pathway by which protein-rich diets stimulate gastric acid secretion.

Prevalence and characteristics of tracheal cobblestoning in children.

BACKGROUND: Tracheal follicular pattern or so-called tracheal cobblestoning is a poorly described entity in the literature and is depicted as a nodular or lumpy appearance of the tracheal wall mucosa suggesting tracheal irritation from factors like gastro-esophageal reflux (GERD) or pulmonary infection. The aim of the present study was to investigate the prevalence and characteristics of tracheal cobblestones in a large pediatric population. METHODS: A large database of rigid tracheoscopies recorded in children (0-6 years of age) undergoing general anesthesia with planned tracheal intubation for elective surgical procedures was retrospectively analyzed. Tracheoscopy records were reviewed by five pediatric airway experts (authors 3-7). Data were compared using the Mann-Whitney test, chi-square or Fisher exact test as appropriate (P < 0.05). RESULTS: A total of 971 rigid tracheoscopy records were analyzed. The median age of the patients was 3.3 years (range 0.4-6.0 yrs). Cobblestones were present in 377 out of 971 patients (38.8%) with a male to female prevalence of 254 (40.6%)/123 (35.5%). None of the children under four months of age showed the presence of cobblestones. The prevalence of cobblestones was significantly less in patients under 3 years of age compared to over 3 years (P < 0.01). There was no association between prevalence of cobblestones and GERD, current or recent respiratory infection or concomitant enlarged tonsils. CONCLUSION: The prevalence of tracheal cobblestones in otherwise healthy children is high and is not associated with GERD or respiratory infection. The gender and age related differences are novel interesting findings that require further investigations.

The prevalence of tracheal bronchus in pediatric patients undergoing rigid bronchoscopy.

BACKGROUND: Tracheal bronchus (TB) is defined as an abnormal bronchus that originates directly from the lateral wall of the trachea above the carina and goes towards the upper lobe territory of the lung. We analyzed rigid endoscopies of the trachea in children to determine the incidence and characteristics of TB. METHODS: In total, 1021 rigid endoscopies of the trachea recorded from children aged 0 to 6 years were analyzed. Endoscopic examination was performed from supraglottic region to carina using a 0-degree Hopkins rod-lens telescope. Patients with a TB were identified and the site of origin of the TB and its level above the carina was noted. Data of the identified patients was reviewed for the presence of preoperative airway findings such as stridor, upper lobe pneumonia and wheezing or atelectasis, other congenital anomalies, and intraoperative complications. RESULTS: TB was detected in 11 (1.06%) of 1021 upper airway endoscopic examinations. All originated from the right lateral wall of the trachea. Six children had retained secretions in the TB, and 3 children had perioperative airway problems unrelated to the TB. One child showed right main stem bronchus narrowing as seen at the true carina, in the presence of a TB. All the children with TB exhibited at least 1 additional congenital anomaly at birth besides TB. CONCLUSIONS: TB is a relatively common congenital endoscopic lower airway anomaly in childhood, which is itself rarely symptomatic, but almost always coexists with other congenital anomalies.

Massive aspiration past the tracheal tube cuff caused by closed tracheal suction system.

BACKGROUND: Aspiration past the tracheal tube cuff has been recognized to be a risk factor for the development of ventilator-associated pneumonia (VAP). This study investigated the effect of closed tracheal suctioning on aspiration of fluid past the tracheal tube cuff in an in vitro benchtop model. METHODS: High-volume low pressure tube cuffs of 7.5 mm internal diameter (ID) were placed in a 22 mm ID artificial trachea connected to a test lung. Positive pressure ventilation (PPV) with 15 cm H2O peak inspiratory pressure and 5 cm H2O positive end-expiratory pressure (PEEP) was used. A closed tracheal suction system (CTSS) catheter (size 14Fr) was attached to the tracheal tube and suction was performed for 5, 10, 15, or 20 seconds under 200 or 300 cm H2O suction pressures. Amount of fluid (mL) aspirated along the tube cuff and the airway pressure changes were recorded for each suction procedure. Fluid aspiration during different suction conditions was compared using Kruskal-Wallis and Mann-Whitney test (Bonferroni correction [α = .01]). RESULTS: During 10, 15, and 20 seconds suction, airway pressure consistently dropped down to -8 to -13 cm H2O (P < .001) from the preset level. Fluid aspiration was never observed under PPV + PEEP but occurred always during suctioning. Aspiration along the tube cuff was higher with -300 cm H2O than with -200 cm H2O suction pressure (P < .001) and was much more during 15 and 20 seconds suction time as compared to 5 seconds (P < .001). CONCLUSION: Massive aspiration of fluid occurs along the tracheal tube cuff during suction with the closed tracheal suction system.

Regulation of renal amino acid transporters during metabolic acidosis.

The kidney plays a major role in acid-base homeostasis by adapting the excretion of acid equivalents to dietary intake and metabolism. Urinary acid excretion is mediated by the secretion of protons and titratable acids, particularly ammonia. NH(3) is synthesized in proximal tubule cells from glutamine taken up via specific amino acid transporters. We tested whether kidney amino acid transporters are regulated in mice in which metabolic acidosis was induced with NH(4)Cl. Blood gas and urine analysis confirmed metabolic acidosis. Real-time RT-PCR was performed to quantify the mRNAs of 16 amino acid transporters. The mRNA of phosphoenolpyruvate carboxykinase (PEPCK) was quantified as positive control for the regulation and that of GAPDH, as internal standard. In acidosis, the mRNA of kidney system N amino acid transporter SNAT3 (SLC38A3/SN1) showed a strong induction similar to that of PEPCK, whereas all other tested mRNAs encoding glutamine or glutamate transporters were unchanged or reduced in abundance. At the protein level, Western blotting and immunohistochemistry demonstrated an increased abundance of SNAT3 and reduced expression of the basolateral cationic amino acid/neutral amino acid exchanger subunit y(+)-LAT1 (SLC7A7). SNAT3 was localized to the basolateral membrane of the late proximal tubule S3 segment in control animals, whereas its expression was extended to the earlier S2 segment of the proximal tubule during acidosis. Our results suggest that the selective regulation of SNAT3 and y(+)LAT1 expression may serve a major role in the renal adaptation to acid secretion and thus for systemic acid-base balance.

Differential localization of vacuolar H+-ATPases containing a1, a2, a3, or a4 (ATP6V0A1-4) subunit isoforms along the nephron.

Vacuolar H(+)-ATPase are multi-subunit containing pumps important for several processes along the nephron such as receptor mediated endocytosis, acidification of intracellular organelles, bicarbonate reabsorption and secretion, and H(+)- extrusion. Mutations in the human a4 (ATP6V0A4) subunit cause distal renal tubular acidosis (dRTA). There are 4 known isoforms of the 'a' subunit (a1-a4). Here we investigated the expression and localization of all four isoforms in mouse kidney. Real-time PCR detected mRNAs encoding all four 'a' isoforms in mouse kidney with a relative abundance in the following order: a4>a2=a1>a3. Immunolocalization demonstrated expression of all 'a' subunits in the proximal tubule and in the intercalated cells of the collecting system. In intercalated cells a1 and a4 isoforms appeared on both the apical and basolateral side and were expressed in all subtypes of intercalated cells. In contrast, a2, and a3 were only found in the apical membrane. a1 and a4 were colocalized in the same cells with AE1 or pendrin, whereas a2 was only found in AE1 positive cells but absent from pendrin expressing intercalated cells. These results suggest that vacuolar H(+)-ATPases containing different 'a' isoforms may serve specific and distinct functions and may help explaining why loss of the a4 isoform causes only dRTA without an apparent defect in the proximal tubule.