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At least 19 recordsLinked to original sources
PubMed2005

Nap-titration: an effective alternative for continuous positive airway pressure titration.

When treating Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) several alternatives for standard (manual) continuous positive airway pressure (CPAP) titration are feasible. A practical alternative is titration without polysomnography during an afternoon nap (Nap-titration). The aim of the present study was to assess whether Nap-titration is appropriate for effective titration of CPAP. Following Nap-titration 24 eligible OSAHS patients started conventional CPAP therapy. The outcome of Nap-titration was verified after 2 weeks with CPAP pressure adjustments being performed in case of persisting OSAHS symptomatology. Polysomnography and a questionnaire evaluation were performed at baseline and 8 weeks after Nap-titration. Following Nap-titration 15 patients did not require pressure changes while in 9 patients' CPAP pressure was raised due to persisting OSAHS symptomatology. Control polysomnography after 8 weeks showed successful CPAP titration (Apnea-Hypopnea Index <5) in 23 out of 24 patients. A pressure raise following polysomnography was indicated in 1 patient only. In addition, significant improvements were found in OSAHS symptomatology and quality of life. This study shows that in 96% of OSAHS patients' successful CPAP titration is attained following Nap-titration whether or not supplemented by pressure adjustments. Therefore, Nap-titration with an adequate follow-up appears an appropriate procedure for the effective titration of CPAP.

Adult↗
PubMed2004

Comparison of conventional nighttime with automatic or manual daytime CPAP titration in unselected sleep apnea patients: study of the usefulness of daytime titration studies.

Daytime CPAP titration studies with full polysomnography have been successfully performed in patients with severe sleep apnea-hypopnea syndrome (SAHS). The implementation of daytime studies in unselected SAHS patients could help to reduce the waiting lists for CPAP titrations. The main purpose of this study was to compare the effectiveness of conventional versus manual or automatic daytime CPAP titration in unselected patients with SAHS. Ninety-three consecutive patients with SAHS in whom CPAP was indicated were assigned to conventional titration or to manual or automatic (AutoSet) daytime CPAP titration, after sleep deprivation. The number of valid studies, sleep architecture, final pressure selected and mean pressure in the different sleep stages were compared. Changes in sleepiness (Epworth sleepiness score) and hours of CPAP use were assessed after 3 months of treatment. Four patients did not sleep (3 AutoSet, 1 conventional daytime groups). Sleep latency was shorter during automatic daytime titration whereas REM latency was shorter in daytime studies; the percentage of sleep stages was similar during all types of titration. CPAP requirements were significantly higher during REM sleep in conventional and manual daytime titrations while mean pressure was unchanged throughout sleep stages during AutoSet titration. CPAP pressure selected with conventional or daytime manual titration (7.5(2.2) cm H2O and 7.4(1.5) cm H2O, ns) were significantly lower (P< 0.001) than with AutoSet (9.4(1.6) cm H20. All groups showed similar decrease of sleepiness and hours of use of CPAP at 3 months of follow-up. Automatic and manual daytime PSG studies after sleep deprivation are useful for CPAP titration in unselected patients with SAHS. Pressure selected with AutoSet is significantly higher than with conventional daytime or nighttime titration, although not significant in terms of treatment compliance and symptom improvement.

Adult↗
PubMed2002

Practice parameters for the use of auto-titrating continuous positive airway pressure devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome. An American Academy of Sleep Medicine report.

Continuous positive airway pressure (CPAP) is used to treat patients with the obstructive sleep apnea syndrome (OSAS). The current standard is for an attendant technician to titrate CPAP during full polysomnography to obtain a fixed single pressure. The patient uses CPAP nightly at this fixed single pressure. Recently, devices using new technology that automatically titrate positive airway pressure (APAP) have become available. Such devices continually adjust pressure, as needed, to maintain airway patency (APAP titration). These adjustments can be made with or without attendant technician intervention. Data obtained during APAP titration can be used to provide a fixed single pressure for subsequent treatment. Alternatively, APAP devices can be used in self-adjusting mode for treatment (APAP treatment). A task force of the Standards of Practice Committee of the American Academy of Sleep Medicine reviewed the available literature. Based on this review, the Standards of Practice Committee developed these practice parameters as a guide to the appropriate use of APAP. Recommendations are as follows: 1) A diagnosis of OSAS must be established by an acceptable method. 2) APAP titration and APAP treatment are not currently recommended for patients with congestive heart failure, significant lung disease (e.g., chronic obstructive pulmonary disease), daytime hypoxemia and respiratory failure from any cause, or prominent nocturnal desaturation other than from OSA (e.g., obesity hypoventilation syndrome). In addition, patients who do not snore (either due to palate surgery or naturally) should not be titrated with an APAP device that relies on vibration or sound in the device's algorithm. 3) APAP devices are not currently recommended for split-night studies since none of the reviewed research studies examined this issue. 4) Certain APAP devices may be used during attended titration to identify by polysomnography a single pressure for use with standard CPAP for treatment of OSA. 5) Once an initial successful attended CPAP or APAP titration has been determined by polysomnography, certain APAP devices may be used in the self-adjusting mode for unattended treatment of patients with OSA. 6) Use of unattended APAP to either initially determine pressures for fixed CPAP or for self-adjusting APAP treatment in CPAP naïve patients is not currently established. 7) Patients being treated with fixed CPAP on the basis of APAP titration or being treated with APAP must be followed to determine treatment effectiveness and safety, and 8) a re-evaluation and, if necessary, a standard attended CPAP titration should be performed if symptoms do not resolve or the CPAP or APAP treatment otherwise appears to lack efficacy.

Equipment Design↗
PubMed2006

A new approach to flow-batch titration. A monosegmented flow titrator with coulometric reagent generation and potentiometric or biamperometric detection.

Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations performed in monosegmented systems, because the reagent can be added without increasing the volume of sample injected. Also, biamperomeric and potentiometric detection of titration end-points can increase the versatility of the monosegmented titrator. The cell integrates coulometric generation of the titrand with detection of end-point by potentiometry or biamperometry. The resulting titrator is a flow-batch system in which the liquid monosegment, constrained by the interfaces of the gaseous carrier stream, plays the role of a sample of known volume to be titrated. The system has been used for determination of ascorbic acid, by coulometric generation of I2 with biamperometric detection, and for determination of Fe(II), by coulometric generation of Ce(IV) with potentiometric detection of the end-point, both in feed supplements.

Journal Article↗
PubMed2005

Titration of the bacteriorhodopsin Schiff base involves titration of an additional protein residue.

The retinal protein protonated Schiff base linkage plays a key role in the function of bacteriorhodopsin (bR) as a light-driven proton pump. In the unphotolyzed pigment, the Schiff base (SB) is titrated with a pK(a) of approximately 13, but following light absorption, it experiences a decrease in the pK(a) and undergoes several alterations, including a deprotonation process. We have studied the SB titration using retinal analogues which have intrinsically lower pK(a)'s which allow for SB titrations over a much lower pH range. We found that above pH 9 the channel for the SB titration is perturbed, and the titration rate is considerably reduced. On the basis of studies with several mutants, it is suggested that the protonation state of residue Glu204 is responsible for the channel perturbation. We suggest that above pH 12 a channel for the SB titration is restored probably due to titration of an additional protein residue. The observations may imply that during the bR photocycle and M photointermediate formation the rate of Schiff base protonation from the bulk is decreased. This rate decrease may be due to the deprotonation process of the "proton-releasing complex" which includes Glu204. In contrast, during the lifetime of the O intermediate, the protonated SB is exposed to the bulk. Possible implications for the switch mechanism, and the directionality of the proton movement, are discussed.

Amino Acid Substitution↗
PubMed1985

Generalized theory for two-phase ion-pair and complexometric titrations. II. Two-phase titrations with side reactions.

For the two-phase titration based on ion-pair and metal-complex formation full attention is given to side reactions in both phases. Their significance for the applicability of this type of titration is evaluated. Side reactions in the aqueous phase diminish and in the organic phase promote the 'titratability'. Equations for the calculation of the side reaction coefficients, the titration curve and the selection of the optimal pH and minimal side reaction interference (in the aqueous phase) are presented. Finally a full description is given of the two-phase titration including all parameters determining the 'titratability'. The merits of the developed theory are illustrated by literature examples.

Chemical Phenomena↗
PubMed1992

Electrochemical titration of the cytochrome hemes in the Rhodopseudomonas viridis reaction center. Cyclic equilibrium titrations yield midpoint potentials without evidence for heme cooperativity.

The redox and spectral characteristics of the 4-heme cytochrome c unit of the photochemical reaction center from Rhodopseudomonas viridis were studied by a combination of protein electrochemistry and spectroscopy using an ultra thin-layer spectroelectrochemical cell. Quantitative and reversible reduction of the high-potential and the low-potential hemes was performed in cyclic titrations to record the optical difference spectra in the alpha-band region. The titration of the absorbance from the high-potential hemes can be approximated with a sum of 2 Nernst functions with Em = 0.113 V and Em = 0.175 V. The corresponding titration of the absorbance from the low-potential hemes yielded Em = -0.257 V and Em = -0.175 V (all potentials quoted vs. Ag/AgC1/3 M KCl; add 0.208 V for potentials vs. standard hydrogen electrode). The high-potential hemes equilibrate rapidly and titrate identically for oxidative and reductive titrations. Under identical conditions, the low-potential hemes exhibit a hysteresis, thus indicating much slower equilibration with the applied potential. Cyclic titrations with increasing equilibration periods, however, indicate the disappearance of the hysteresis for equilibration periods approximately twice as long as for the high-potential hemes. We take this as evidence for a slower internal equilibration, but against a cooperativity of the low-potential hemes as observed for other multi-heme cytochromes.

Cytochrome c Group↗
PubMed1995

Microculture virus titration--a simple colourimetric assay for influenza virus titration.

Influenza antigens can be detected by several well established methods. However, when it is important to determine the titre of infective virions, a bioassay should be employed. The standard and the most widely used tests for influenza infectivity are titration carried out in embryonated hen eggs, or the plaque assay employing tissue culture techniques. A simple colourimetric assay for influenza virus detection and titration is described. Samples of allantoic fluid or mice lung homogenates were used to infect MDCK cultures in microplate wells. After an incubation period, the tetrazolium (MTT) colourimetric assay was used to determine cell viability, and when compared to untreated culture control enabled the detection and titration of several influenza strains. When samples were assayed simultaneously in embryonated eggs and by the MCVT method, good correlation in determined titres was obtained. The availability of an additional method for influenza titration allows more flexibility in the choice of titration method according to the specific needs of the study. Furthermore, this method lends itself to full automatization. Similar procedures should also be applicable to titration of other cytopathic viruses.

Animals↗
PubMed2005

Rapid titration versus conventional titration of quetiapine in the treatment of bipolar mania: a preliminary trial.

The present trial was designed as a pilot study to re-examine how fast the dose of quetiapine in combination with mood stabilizers can be titrated upward in acutely ill patients with bipolar mania. Patients were assigned to either a rapid titration group (RTG) or a conventional titration group (CTG). Quetiapine was administered twice daily in a 3-day period in the RTG (200 mg/day on day 1; 400 mg/day on day 2; and 600 mg/day on day 3) and in a 5-day period in the CTG (50 mg/day on day 1; 100 mg/day on day 2; 200 mg/day on day 3; 300 mg/day on day 4; and 400 mg/day on day 5). The Young Mania Rating Scale (YMRS) and Clinical Global Impression-Severity (CGI-S) scores were assessed at days 1 (baseline), 3, 5, 7, 14 and 21. The Barnes Akathisia Rating Scale and Simpson-Angus Rating Scale (SARS) were assessed at days 1, 2, 3, 4, 5, 6, 7, 14 and 21. RTG and CTG showed significant improvement on the scores of YMRS and CGI-S during the study without group differences. Both treatments were well tolerated without clinically significant differences in tolerability measures. Treatment was not limited by adverse events in the two groups. This study demonstrates the potential benefit and tolerability of rapid titration of quetiapine in the treatment of acutely ill bipolar disorder. This preliminary study proposes that rapid titration of quetipaine in combination with a mood stabilizer for the treatment of bipolar mania is effective and tolerable in comparison with conventional titration. A controlled study with a larger cohort should be performed.

Adolescent↗
PubMed2006

Propofol alone titrated to deep sedation versus propofol in combination with opioids and/or benzodiazepines and titrated to moderate sedation for colonoscopy.

BACKGROUND: Propofol by nonanesthesiologists is controversial because the drug is commonly used to produce deep sedation or general anesthesia. Propofol in combination with opioids and/or benzodiazepines can be titrated to moderate sedation, which might be safer. AIM: To compare recovery time, patient satisfaction, and other end points with propofol alone titrated to deep sedation versus propofol combination therapy with opioids and/or benzodiazepines. METHOD: A randomized controlled clinical trial of propofol alone titrated to deep sedation versus fentanyl plus propofol versus midazolam plus propofol versus fentanyl plus midazolam plus propofol in 200 outpatients undergoing colonoscopy. Each combination regimen was titrated to moderate sedation. RESULTS: Patients receiving propofol alone received higher doses of propofol and had deeper sedation scores compared with combination therapy (both p < 0.001). Patients receiving combination regimens were discharged more quickly (median 13.0-14.7 versus 18.1 min) than those receiving propofol alone (p < 0.01). There were no differences in vital signs or oxygen saturations among the study arms. There were no significant differences in pain or satisfaction among the study arms in the recovery area. At a follow-up phone call, patients receiving fentanyl and propofol remembered more of the procedure than those in the other regimens (p < 0.005) and remembered more pain than those receiving propofol alone (p < 0.02). CONCLUSIONS: Propofol in combination with fentanyl and/or midazolam can be titrated to moderate levels of sedation without substantial loss of satisfaction and with shorter recovery times compared with propofol titrated to deep sedation throughout the procedure.

Adjuvants, Anesthesia↗
PubMed2004

Long-range nature of the interactions between titratable groups in Bacillus agaradhaerens family 11 xylanase: pH titration of B. agaradhaerens xylanase.

Xylanase from Bacillus agaradhaerens belongs to a large group of glycosyl hydrolases which catalyze the degradation of xylan. The protonation behavior of titratable groups of the uniformly (15)N- and (13)C-labeled xylanase was investigated by multinuclear NMR spectroscopy. A total of 224 chemical shift titration curves corresponding to (1)H, (13)C, and (15)N resonances revealed pK(a) values for all aspartic and glutamic acid residues, as well as for the C-terminal carboxylate and histidine residues. Most of the titratable groups exhibit a complex titration behavior, which is most likely due to the mutual interactions with other neighboring groups or due to an unusual local microenvironment. Subsite -1 containing the catalytic dyad shows a long-range interaction over 9 A with Asp21 via two hydrogen bonds with Asn45 as the mediator. This result illuminates the pivotal role of the conserved position 45 among family 11 endoxylanases, determining an alkaline pH optimum by asparagine residues or an acidic pH optimum by an aspartate. The asymmetric interactions of neighboring tryptophan side chains with respect to the catalytic dyad can be comprehended as a result of hydrogen bonding and aromatic stacking. Most of the chemical shift-pH profiles of the backbone amides exhibit biphasic behavior with two distinct inflection points, which correspond to the pK(a) values of the nearby acidic side chains. However, the alternation of both positive and negative slopes of individual amide titration curves is interpreted as a consequence of a simultaneous reorganization of side chain conformational space at pH approximately 6 and/or an overall change in the hydrogen network in the substrate binding cleft.

Aspartic Acid↗
PubMed1997

pH titration of native and unfolded beta-trypsin: evaluation of the delta delta G0 titration and the carboxyl pK values.

The stabilizing free energy of beta-trypsin was determined by hydrogen ion titration. In the pH range from 3.0 to 7.0, the change in free energy difference for the stabilization of the native protein relative to the unfolded one (delta delta G0 titration) was 9.51 +/- 0.06 kcal/mol. An isoelectric point of 10.0 was determined, allowing us to calculate the Tanford and Kirkwood electrostatic factor w. This factor presented a nonlinear behavior and indicated more than one type of titratable carboxyl groups in beta-trypsin. In fact, one class of carboxyl group with a pK = 3.91 +/- 0.01 and another one with a pK = 4.63 +/- 0.03 were also found by hydrogen ion titration of the protein in the folded state.

Enzyme Stability↗
PubMedDate not supplied

Reliable pKw values from potentiometric titrations: the striking effect of the titration final added volume.

Errors affecting the estimation of the ionic product of water from the potentiometric titration of weak acids have been analysed. A Fortran programme has been developed in order to simulate experimental titration data sets. This programme allows one to isolate experimental error sources and analyse their effect upon the final fitted equilibrium constant. pKw dependence with titration final added volume and the pK value of the weak acid, predicted with the simulation programme are coincident with experimental data, suggesting that obtaining reliable pKw values entails using experimental data of titrations up to a sufficiently large hydroxyl concentration which depends on the value of pK.

Environmental Monitoring↗