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Biomedical subjects

C Keller

Publications and source records attributed to C Keller.

At least 55 records · Page 3Linked to original sources
PubMed2004

Residual protein contamination of ProSeal laryngeal mask airways after two washing protocols.

The risk of prion protein cross-infection has focussed attention on the potential hazards of protein contamination of re-usable medical devices. This study determined the frequency of protein contamination of ProSeal laryngeal mask airways (PLMA) after two cleaning procedures and tested the hypothesis that the combination of hand- and machine-washing removes protein contamination more effectively than hand-washing alone. After clinical use fifty-four PLMAs were randomly allocated to be washed by hand or by hand then machine. All PLMAs were then autoclaved at 134 degrees C for 4 minutes. After processing, each PLMA was immersed in a 1.2% solution of erythrosin B and examined for uptake of stain. The site (outer surface, bowl and edges of the cuff airway and drain tube, finger strap) and severity (nil/mild/moderate/severe) of staining was scored by a blinded observer. There were no differences in the site or severity of staining between the two cleaning procedures. Staining was detected on 89% of PLMAs that were hand-washed and 78% of PLMAs that were hand-, then machine-washed (P=0.27). When staining occurred, it was mild in 98%, moderate in 2% and was never severe. Staining was more frequent on the edge than at any other location (all comparisons: P < or = 0.01). The strap never had any staining. We conclude that residual contamination of PLMAs with protein deposits is common even when machine-washing is used to augment hand-washing before autoclaving. The infection risk associated with these deposits remains to be determined.

Cross Infection↗
PubMed2004

Gum elastic bougie-guided insertion of the ProSeal Laryngeal Mask Airway.

We tested the hypothesis that gum elastic-bougie-guided insertion of the ProSeal Laryngeal Mask Airway is more frequently successful than introducer tool guided insertion after failed digital insertion. One hundred anaesthetized patients (ASA 1-2, aged 18 to 80 years) were randomized for the second insertion attempt using either the gum elastic bougie-guided or introducer tool techniques. The bougie-guided technique involved priming the drain tube with the bougie, placing the bougie in the oesophagus using laryngoscope guidance, digital insertion along the palato-pharyngeal curve, and bougie removal. The introducer tool technique involved attaching the introducer tool, single-handed rotation along the palatopharyngeal curve, and introducer tool removal. Failed insertion was classified as (i) failed passage into the pharynx, (ii) malposition, or (iii) ineffective ventilation. Any blood staining was documented. Insertion was more frequently successful (50/50 vs 15/50, P=0.0002) and faster (35+/-17 s vs 54+/-45 s, mean+/-SD, P=0.006) with the bougie-guided technique. All failed insertions with the introducer tool technique were successful with the bougie-guided technique. The aetiology of failed insertion was similar for the digital and introducer tool techniques in 94% (33/35) of patients. There was no blood staining on the bougie, laryngoscope or introducer tool at removal, but blood staining was more common on the ProSeal Laryngeal Mask Airway with the introducer tool technique (9/50 vs 2/50, P=0.03). We conclude that the gum elastic bougie-guided insertion has a higher success rate and causes less trauma than the insertion tool insertion technique after failed digital insertion of the ProSeal Laryngeal Mask Airway.

Adolescent↗
PubMed2004

Positive pressure versus pressure support ventilation at different levels of PEEP using the ProSeal laryngeal mask airway.

We compared positive pressure ventilation with pressure support ventilation at different levels of positive end expiratory pressure (PEEP) using the ProSeal laryngeal mask airway (PLMA). Forty-two anaesthetized adults (ASA 1-2, aged 19 to 63 years) underwent positive pressure ventilation and then pressure support ventilation each with PEEP set at 0, 5 and 10 cmH2O in random order. Pressure support ventilation was with the inspired tidal volume (VTInsp) set at 7 ml/kg and the respiratory rate adjusted to maintain the end-tidal CO2 (ETCO2) at 40 mmHg. Pressure support ventilation was with pressure support set at 5 cmH2O above PEEP and initiated when inspiration produced a 2 cmH2O reduction in airway pressure. Tidal volumes were similar during positive pressure and pressure support ventilation with PEEP, but were higher for the former without PEEP Respiratory rate and peak inspiratory flow rate were higher during pressure support than positive pressure ventilation (all P < 0.001). Peak airway pressure (Ppaw), mean airway pressure (Mpaw), peak expiratory flow rate, and expired airway resistance were lower during pressure support than positive pressure ventilation (all P < 0.001). With PEEP set at 10 cmH2O, ETCO2 was lower for pressure support than positive pressure ventilation. During positive pressure ventilation, there was an increase in Ppaw, Mpaw and dynamic compliance (Cdyn) with increasing levels of PEEP (all P < 0.01). During pressure support ventilation, there was an increase in inspired and expired tidal volume, Ppaw, peak inspiratory and expiratory flow rates and Cdyn, and a reduction in ETCO2, work of breathing, and expired airway resistance with increasing levels of PEEP (all P < 0.01). There were no differences in SpO2, non-invasive mean arterial pressure, heart rate or leak fraction. We conclude that pressure support ventilation provides equally effective gas exchange as positive pressure ventilation during PLMA anaesthesia with or without PEEP at the tested settings. During pressure support, PEEP increases ventilation and reduces work on breathing without increasing leak fraction.

Adult↗
PubMed2003

Efficacy and safety of DALI LDL-apheresis at high blood flow rates: a prospective multicenter study.

Direct adsorption of lipids (DALI) is the first LDL-apheresis method compatible with whole blood. Usually, the blood flow rate is adjusted at 60-80 ml/min, which results in session times of about 2 hr. The present study was performed to test the safety and efficacy of low-density lipoprotein cholesterol (LDL-C) and lipoprotein (a) [Lp(a)] removal by DALI at high blood flow rates in order to reduce treatment time. Thirteen chronic DALI patients in seven centers suffering from hypercholesterolemia (LDL-C 162 +/- 42 mg/dl at baseline) and coronary artery disease were treated on a weekly or biweekly basis by DALI apheresis. The blood flow rate QB was held constant for at least two sessions, respectively, and was increased from 60 to 80, 120, 160, 200, and 240 ml/min. All patients had pre-existing av-fistulas. The anticoagulation was performed by a heparin bolus plus ACD-A at a ratio of citrate:blood ranging from 1:20 to 1:90. Clinically, the sessions were well tolerated and only 26/201 sessions (12%) of the treatments were fraught with minor adverse events. Acute LDL-C reductions (derived from LDL-C levels determined by lipoprotein electrophoresis) averaged 72/66/60/53/50/48% for QB=60/80/120/160/200/240 ml/min. Lp(a) reductions were 68/67/62/60/58/56%, whereas HDL-C losses were < or =10%. Routine blood chemistries and blood cell counts remained in the normal range. Treatment times averaged 142/83/45 min at Qb=60/120/240 ml/min. On average, DALI LDL-apheresis could be performed safely and effectively at high blood flow rates up to at least 120 ml/min in patients with good blood access, which significantly reduced treatment time from 142 to 83 min (-42%).

Adsorption↗
PubMed2003

[Comparison of algorithms for management of the difficult airway].

Management of the difficult airway and maintenance of the oxygenation are the most important tasks of the anaesthetist. Respiratory problems are still the most important single cause for anaesthesia-related accidents with poor outcome. Algorithms are step-wise procedures developed from a great number of recommendations and are well suited to automation and training procedures. There is strong agreement among consultants that specific strategies lead to improved outcome, although, strictly speaking the degree of benefit on airway management cannot be clearly determined. Several anaesthesia societies, including the American Society of Anesthesiology,have developed their own algorithms for management of the difficult airway. The comparison of published algorithms shows that the management of the anticipated difficult airway has to be performed in the awake patient and fiberoptic intubation is a crucial part of that procedure. There are different techniques (different blades, guide wire, laryngeal mask, fiber optics) for the management of the unanticipated difficult airway. The laryngeal mask, transtracheal access and the Combitube are recommended for the management of the cannot intubate, cannot ventilate situation. More important than the questions which algorithm, which technique and which instruments should be used,is that each department has and practices its own algorithm. This strongly depends on local circumstances and personal preferences. Daily practice is the condition for the successful use in an emergency situation. The management is easier if one uses a simple algorithm and as few instruments as possible.

Algorithms↗
PubMed2003

Stability of the LMA-ProSeal and standard laryngeal mask airway in different head and neck positions: a randomized crossover study.

BACKGROUND AND OBJECTIVE: The LMA-ProSeal laryngeal mask airway is a new laryngeal mask airway with a modified cuff and drainage tube. We compared oropharyngeal leak pressure, intracuff pressure and anatomical position (assessed fibreoptically) for the Size 5 LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway in different head-neck positions and using different intracuff inflation volumes. METHODS: Thirty paralysed anaesthetized adult male patients were studied. The LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway were inserted into each patient in random order. The oropharyngeal leak pressure, intracuff pressure, and anatomical position of the airway tube and drainage tube (LMA-ProSeal laryngeal mask airway only) were documented in four head and neck positions (neutral first, then flexion, extension and rotation in random order), and at 0-40 mL cuff volumes in the neutral position in 10 mL increments. RESULTS: Compared with the neutral position, the oropharyngeal leak pressure for both the LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway was higher in flexion and rotation (all P < or = 0.02), but lower in extension (all P < or = 0.01). Changes in head-neck position did not alter the anatomical position of the airway tube or the drainage tube. The oropharyngeal leak pressure was always higher for the LMA-ProSeal laryngeal mask airway (all P < or = 0.005) and anatomical position better for the classic laryngeal mask airway (all P < or = 0.04). CONCLUSIONS: The anatomical position of the LMA-ProSeal and the classic laryngeal mask airway is stable in different head-neck positions, but head-neck flexion and rotation are associated with an increase, and head-neck extension a decrease, in oropharyngeal leak pressure and intracuff pressure. The Size 5 LMA-ProSeal laryngeal mask airway is capable of forming a more effective seal than the Size 5 classic laryngeal mask airway in males.

Adolescent↗
PubMed2003

Searching for the exercise factor: is IL-6 a candidate?

For years the search for the stimulus that initiates and maintains the change of excitability or sensibility of the regulating centers in exercise has been progressing. For lack of more precise knowledge, it has been called the 'work stimulus', 'the work factor' or 'the exercise factor'. In other terms, one big challenge for muscle and exercise physiologists has been to determine how muscles signal to central and peripheral organs. Here we discuss the possibility that interleukin-6 (IL-6) could mediate some of the health beneficial effects of exercise. In resting muscle, the IL-6 gene is silent, but it is rapidly activated by contractions. The transcription rate is very fast and the fold changes of IL-6 mRNA is marked. IL-6 is released from working muscles into the circulation in high amounts. The IL-6 production is modulated by the glycogen content in muscles, and IL-6 thus works as an energy sensor. IL-6 exerts its effect on adipose tissue, inducing lipolysis and gene transcription in abdominal subcutaneous fat and increases whole body lipid oxidation. Furthermore, IL-6 inhibits low-grade TNF-alpha-production and may thereby inhibit TNF-alpha-induced insulin resistance and atherosclerosis development. We propose that IL-6 and other cytokines, which are produced and released by skeletal muscles, exerting their effects in other organs of the body, should be named 'myokines'.

Adipose Tissue↗
PubMed2003

An in vitro study on spontaneous cervical contractility in the cow during oestrus and diestrus.

Cervical smooth muscle specimens were collected from slaughtered cows in oestrus and diestrus. Longitudinal and circular specimens were mounted in organ baths and after equilibration time and 2 g pre-load, their physiologic isometric contractility was recorded for 2.5 h. Area under the curve (AUC), maximal amplitude (Amax), mean amplitude (Amen) and minimal amplitude (Amin) were studied. Differences between cycle phases, between muscle layers and over the recorded time periods were statistically evaluated using linear mixed-effect models. In the cow, physiologic contractility of the cervix decreased significantly over time for all variables evaluated (time as covariate on a continuous scale). Furthermore, for Amax, there was a tendency for an influence of muscle layer (longitudinal > circular). Contractility was not influenced by cycle phases.

Animals↗
PubMed2003

Pharyngeal mucosal pressures with the laryngeal tube airway versus ProSeal laryngeal mask airway.

We tested the hypothesis that mucosal pressures are higher for the laryngeal tube airway trade mark than the ProSeal laryngeal mask airway. Fifteen fresh cadavers were studied. Microchip pressure sensors were attached to the laryngeal tube airway and ProSeal laryngeal mask airway at four similar anatomical locations (base of tongue, lateral pharynx, posterior pharynx and posterior hypopharynx) and three dissimilar locations (laryngeal tube airway trade mark, anterior and lateral hypopharynx; ProSeal laryngeal mask airway, pyriform fossa). The cuff volume (laryngeal tube airway, < or = 140 ml; ProSeal laryngeal mask airway, < or = 30 ml) was adjusted until the oropharyngeal leak pressure was 15 cm H2O and the mucosal pressures recorded. This was repeated at an oropharyngeal leak pressure of 20, 25 and 30 cm H2O. Mucosal pressures in the lateral pharynx were always similar. Mucosal pressures at the base of tongue and posterior pharynx were similar for the laryngeal tube airway and ProSeal laryngeal mask airway at 15 and 20 cm H2O, but were higher for the laryngeal tube airway at 25 cm H2O at 30 cm H2O. Mucosal pressures in the posterior hypopharynx were always higher for the laryngeal tube airway (all: p < 0.03). Mean mucosal pressures for the laryngeal tube airway ranged from 8-31, 2-13 and 15-41 cm H2O for the base of tongue, lateral pharynx and posterior pharynx (proximal cuff) respectively and 3-7, 3-7 and 7-18 cm H2O for the anterior, lateral and posterior hypopharynx (distal cuff) respectively. Mean mucosal pressures for the ProSeal laryngeal mask airway ranged from 6-23, 3-10, 8-25, 6-17 and 2-8 cm H2O for the base of tongue, lateral pharynx, posterior pharynx, pyriform fossa and posterior hypopharynx respectively. We conclude that mucosal pressures are higher for the laryngeal tube airway, particularly when oropharyngeal leak pressure greater than 25 cm H2O. This suggests that mucosal ischemic injury will be more common with the LTA than the PLMA.

Aged↗
PubMed2003

Cytokines in the seronegative spondyloarthropathies and their modification by TNF blockade: a brief report and literature review.

Rheumatoid arthritis (RA) is a disease well characterised by proinflammatory cytokine secretion (particularly tumour necrosis factor, interferon gamma, interleukin (IL) 1, and IL6). Less has been reported about the cytokine profiling in the spondyloarthropathies (SpA). Several trials suggest that, similar to RA, proinflammatory cytokines are globally expressed in the SpA. However, other studies report a down regulation of these cytokines in the SpA, with a relative anti-inflammatory polarisation (featuring increases in IL4, IL5, and IL10). This review summarises current published reports and the variation in cytokine data in the SpA. Additionally, results of cytokine profiles in patients with ankylosing spondylitis before and after treatment with etanercept are reported.

Antirheumatic Agents↗
PubMed2003

Feasibility, accuracy and optimal location for oesophageal core temperature measurements using the ProSeal laryngeal mask airway drain tube.

We determined the feasibility, accuracy and optimal location of oesophageal core temperature measurements using the ProSeal laryngeal mask airway drain tube. Thirty normothermic anaesthetized ventilated adults (ASA 1 to 2, aged 18 to 80 years) were studied. Temperatures were recorded using a thermistor at six different locations (middle of drain tube and at 0 to 20 cm distal to the drain tube in 5 cm increments) and compared to nasopharyngeal (thermistor) and aural (infrared tympanic thermometer) reference core temperatures. The temperature probe was successfully inserted into the oesophagus in all patients at the first attempt. Oesophageal temperature increased with depth from 0 to 5 cm (35.2 v 35.9, P < 0.0001) and 5 to 10 cm (35.9 v 36.3, P < 0.01), but was unchanged from 10 to 15 cm (36.3 v 36.6) and 15 to 20 cm (36.6 v 36.7). Aural temperature was higher than nasopharyngeal temperature (36.8 v 36.0, P < 0.0001). Aural temperature was 0.89 to 1.59 degrees C higher than the oesophagus at 0 to 5 cm and 0.21 to 0.30 degree C higher than the oesophagus at 15 to 20 cm. Nasopharyngeal temperature was 0.06 to 0.76 degree C higher than the oesophagus at 0 to 5 cm and 0.62 to 0.84 degree C lower than the oesophagus at 15 to 20 cm. The lowest temperature was in the mid-point of the drain tube (34.7). We conclude that oesophageal core temperature measurement is feasible and accurate using the ProSeal laryngeal mask airway. The optimal location for the temperature probe is at 15 to 20 cm.

Adult↗
PubMed2003

A comparison of the ProSeal and classic laryngeal mask airways for airway management by inexperienced personnel after manikin-only training.

We compared the ProSeal (PLMA) and Classic (LMA) laryngeal mask airway for airway management by inexperienced personnel. Nine nurses from the post-anaesthesia care unit, with no prior experience of LMA or PLMA insertion, were observed inserting the LMA and PLMA in 60 ASA 1 to 2 anaesthetized, paralyzed adults following manikin-only training. The time to achieve an effective airway (2 consecutive expired tidal volumes (6 ml/kg; maximum 2 minutes allowed), the number of insertion attempts and the reasons for failure (inability to insert into pharynx or inadequate ventilation) were determined by analysis of digital video recordings. The first attempt success rate (LMA, 85%; PLMA, 83%), overall success rate (LMA, 88%; PLMA, 90%) and effective airway time (LMA, 39 +/- 13 s; PLMA, 43 +/- 19 s) were similar. Failure was from an inability to insert into the pharynx in five with the LMA and three with the PLMA, and inadequate ventilation with two from the LMA and three from the PLMA. Effective airway time and the number of failures were similar for the first and second device. Failure of both devices occurred in four patients. We conclude that airway management in anaesthetized, paralyzed adults is equally successful for the LMA and PLMA by inexperienced personnel following manikin-only training. The PLMA is worthy of consideration as a tool for emergency airway management by inexperienced personnel.

Adult↗
PubMed2002

Separation quality of a geometric ratchet.

We consider an experimentally relevant model of a geometric ratchet in which particles undergo drift and diffusive motion in a two-dimensional periodic array of obstacles, and which is used for the continuous separation of particles subject to different forces. The macroscopic drift velocity and diffusion tensor are calculated by a Monte Carlo simulation and by a master-equation approach, using the corresponding microscopic quantities and the shape of the obstacles as input. We define a measure of separation quality and investigate its dependence on the applied force and the shape of the obstacles.

Journal Article↗