Stimulation of small intestinal burst activity in the postprandial state differentially affects lipid and glucose absorption in healthy adult humans

Small intestinal motor activity is important for the optimal digestion and absorption of nutrients. These motor responses to feeding are frequently abnormal during critical illness, with the persistence of migrating bursts of contractions during enteral feeding. Whether this disturbance influences nutrient absorption is not known. In this study, the effects of small intestinal burst activity on lipid and glucose absorption were evaluated in 10 healthy human adults (6 males, 4 females, 19-47 yr). Upper gastrointestinal manometry was recorded for 6 h during and shortly after a 20-min intravenous infusion of either erythromycin (1 mg/kg), to stimulate burst activity, or saline (0.9%) in a double-blind randomized fashion. Simultaneously with the start of the intravenous infusion, 60 ml liquid feed mixed with 200 microl 13C-triolein and 2 g 3-O-methylglucose (3-OMG) was infused intraduodenally for 30 min. Absorption of lipid and glucose was assessed using the [13C]triolein breath test and plasma concentrations of 3-OMG, respectively. Infusion of erythromycin was followed by a more rapid onset of burst activity following commencement of the duodenal infusion compared with saline (30 +/- 6.1 vs. 58 +/- 10.7 min; P < 0.05). Erythromycin was associated with a slower recovery of 13CO2 (P < 0.01). A positive correlation existed between the time to onset of burst activity and 13CO2 recovery (P < 0.001). Erythromycin had no effect on 3-OMG absorption. In conclusion, stimulation of small intestinal burst activity reduces the rate of lipid absorption but not glucose absorption in healthy human adults.

Seasonal variation of serum lysozyme levels in Atlantic halibut (Hippoglossus hippoglossus L.)

Serum lysozyme was measured in Atlantic halibut (Hippoglossus hippoglossus L.) kept in a range of different conditions that included ambient photoperiod and temperature and controlled photoperiod and temperature. There was no significant difference between animals held in ambient conditions of 6 degrees C and those held in controlled conditions of 12 degrees C. Similarly, there was no significant difference between animals maintained in a long day photoperiod and those in a short day photoperiod. However, there was a significant difference between summer and winter readings. Whilst this would indicate a link between season and the defence system, there appears to be no link with apparent entrainment to different photoperiods and serum lysozyme levels.

In vitro interactions between Neoparamoeba sp. and Atlantic salmon epithelial cells

Neoparamoeba sp., including the putative aetiological agent of amoebic gill disease in cultured fish (N. pemaquidensis), were incubated in vitro with an Atlantic salmon gill epithelium (RGE-2) cell line. Proliferation by the amoeba population was dependent upon culture osmolarity; no growth occurred at 330 mm x kg(-1) but a sixfold increase was observed at 1000 mm x kg(-1). At 780 mm x kg(-1) there was a fourfold increase in the amoeba population but a concurrent decrease in RGE-2 cell density that was significantly greater than that caused by the high culture osmolarity alone. This apparent cytopathic effect (CPE) developed rapidly and resulted in complete cytolysis of the monolayer in 5 days. CPE occurred in multiple foci and presented as cell vacuolation, rounding and clumping, and the rapid clearance of large areas of the cell monolayer. The possibility that CPE is because of the presence of Neoparamoeba sp. derived cytolytic products is discussed in the context of the pathology of the disease in vivo and the occurrence of secreted cytopathogenic compounds in other amoeba species.

A common ancestral mutation (C128X) occurring in 11 non-Jewish families from the UK with factor XI deficiency

Factor XI (FXI) deficiency is a mild bleeding disorder that is particularly common in Ashkenazi Jews, but has been reported in all populations. In Jews, two FXI gene (F11) mutations (a stop codon in exon 5, E117X, type II, and a point mutation in exon 9, F283L, type III) are particularly common, but in other populations a variety of different mutations have been described. In the Basque region of France one mutation, C38R in exon 3, was found in eight of 12 families studied, haplotype analysis suggesting a founder effect. In the course of screening 78 unrelated individuals (including 15 Jewish and 12 Asian) we have found 10 Caucasian non-Jewish patients with the mutation C128X in exon 5. Individuals were investigated because of a personal or family history of bleeding, or finding a prolonged activated partial thromboplastin time. Individuals negative for the type II and type III mutations were screened by a combination of SSCP and heteroduplex analysis. The C128X mutation was found in 10 families (one previously described). Among three individuals with severe FXI deficiency, one was homozygous for the C128X mutation, and two were compound heterozygotes for the C128X and another mutation; other individuals were carriers of the C128X mutation. This is a nonsense mutation producing a truncated protein; individuals have FXI antigen levels concordant with FXI coagulant activity. Haplotype analysis of 11 families, including a further kindred previously reported from the USA, but which originally came from the UK (in which the index patient was homozygous for C128X), suggests a founder effect.

Sex determination by PCR analysis of DNA extracted from incinerated, deciduous teeth

Establishing the biological sex of human remains is a very important part of identifying victims of fire when severe soft tissue destruction has occurred. Deciduous (children's) teeth were exposed to a range of incineration temperatures 100-500 degrees C for 15 minutes. Polymerase Chain Reaction (PCR) amplification was used to identify specific human amelogenin regions. There was successful identification of human biological sex, from deciduous teeth exposed to incineration temperatures of 200 degrees C and below, using standard ethidium bromide gel staining. There was greater sensitivity using fragment analysis by laser induced fluorescence which achieved sex identification from some teeth heated to 400 degrees C.

114EFFECT OF CYTOCHALASIN B TREATMENT ON VITRIFICATION OF CAPRINE PARTHENOGENIC BLASTOCYSTS

Production of human recombinant proteins in the milk of transgenic animals has been shown to be a viable production system. Protection of the animal genetics involved is paramount. Vitrification of embryos is a simple, time-efficient way of preserving an animal’s genetics without the formation of damaging ice crystals during the freezing process. Cytochalasin B has been shown to increase the viability of porcine blastocysts by reducing damage to microfilaments and other cytoskeletal components. These experiments utilized caprine parthenogenic blastocysts as a model to compare the viability of parthenotes treated with or without cytochalasin B prior to and during vitrification. Abattoir oocytes were in vitro-matured in M199 with 10% goat serum containing FSH, LH and gentamycin for 18 to 21h. Parthenogenic blastocysts were produced by treating in vitro matured abattoir oocytes with ionomycin for 5min (5μM) and with 6-dMAP (3mM) for 3h followed by culturing in SOF+0.8% BSA for 7 to 8 days at 38°C with 6% O2, 5% CO2, and 89% N2 in a modular incubator chamber. The experimental group was treated with cytochalasin B (5μg/mL)in the culture media for 30 to 45min prior to and thereafter throughout the vitrification process. All blastocysts (both the experimental group and the control group) were washed through two ovum culture media (OCM) droplets for 5min each. The blastocysts were incubated in vitrification solutions 1 and 2 (10% glycerol in OCM and 10% glycerol+20% ethylene glycol in OCM, respectively) for 5min each, followed by vitrification solution 3 (25% glycerol+25% ethylene glycol in OCM). They were then aspirated immediately into a 0.25cc cryopreservation straw, followed by an air bubble, and then a 0.25M sucrose solution in OCM. The straws were immediately plunged into liquid nitrogen and stored at −196°C. One to four days later, straws were thawed in air for 5s at room temperature, then in 22°C water for 15s. After thawing, the contents of the straw were expelled, mixed, held for 5min, and finally placed in OCM for 5min. Recovered embryos were placed in SOF+20% FBS and incubated at 38°C with 5% CO2 in air overnight. Viability was determined by re-expanding and subsequent hatching of the blastocyst. As shown in Table 1, there were no significant differences between re-expansion and hatching of blastocysts with cytochalasin B treatment compared to blastocysts not treated with cytochalasin B. These results suggest that, unlike porcine embryos (Dobrinsky et al., 2000 Biol Reprod 62, 564–570), cytochalasin B treatment does not improve the post-thaw viability of vitrified caprine parthenogenic blastocysts. Table 1

58ESTRUS SYNCHRONIZATION OF DAIRY GOATS UTILIZED AS RECIPIENTS FOR CAPRINE NUCLEAR TRANSFER EMBRYOS

The timing of estrus synchrony between donor and recipient does is an important consideration in an embryo transfer program. Experiments were conducted to determine the optimal time of estrus synchrony between donor and recipient dairy goats used in a commercial nuclear transfer (NT) program. Donor and recipient synchronization was achieved by implanting either a 3-mg norgestomet ear implant (Crestar®, Intervet Int. B.V., Boxmeer, Holland) or a 300-mg progesterone vaginal implant (CIDR-G®, Pharmacia and Upjohn Ltd. Co., Auckland, NZ) on Day 0. A single 5mg intramuscular injection of prostaglandin (Lutalyse®, Pharmacia and Upjohn, Kalamazoo, MI, USA) was administered on Day 7. Recipients received a single 200–500IU intramuscular injection of PMSG (Calbiochem, LaJolla, CA, USA) on Day 13. Alternatively, starting on Day 12 donors received twice daily intramuscular injection (64mg/day) of FSH (Folltropin®, Vetrepharm, Ontario, Canada) over four consecutive days. On Day 15 the implants were removed from both donors and recipients and the animals were mated several times daily to vasectomized bucks over two consecutive days. In Experiment 1, estrus synchrony or asynchrony was achieved by removing the implant from recipients at the same time or 12h later than donors, respectively. In Experiment 2, only estrus asynchrony was utilized and was achieved by removing the implant from recipients either 12 or 18h later than donors. In vivo-ovulated MII oocytes surgically recovered from superovulated donors on Day 17 were enucleated and reconstructed with transfected caprine fetal or adult skin cells or transgenic adult skin cells. Couplets were simultaneously fused, activated, and then cultured in SOF/BSA for 48h at 38°C. Two-to-eight-cell NT embryos at 48h post-fusion and activation were surgically transferred to the oviducts of surrogate recipients with similar implant types and PMSG doses. Pregnancies were determined by ultrasonography starting at approximately Day 28 post-fusion and activation and then monitored weekly. In Experiment 1, there were significantly more pregnant asynchronous recipients compared with synchronous recipients (6 of 24 v. 12 of 124 does, respectively). While there were no significant differences, more offspring were produced per embryo transferred to asynchronous recipients compared with synchronous recipients (5 of 135 v. 11 of 690 offspring per embryo transferred, respectively). In Experiment 2, while not significant, there were more pregnant +12-h asynchronous recipients compared with +18-h asynchronous recipients (16 of 72 v. 5 of 36 does, respectively). Again, while there were no significant differences, more offspring were produced per embryo transferred to +12h compared with +18h asynchronous recipients (11 of 424 v. 3 of 224 offspring per embryo transferred, respectively). These results suggest that asynchrony of estrus between recipients and donors is more beneficial in a commercial caprine NT program, and that +12h may be a more optimal period of asynchrony for recipient does receiving NT embryos. Table 1 Summary of recipient estrus synchronization

Atlantic salmon, Salmo salar L., previously infected with Neoparamoeba sp. are not resistant to re-infection and have suppressed phagocyte function

Previous studies have indicated that Atlantic salmon, Salmo salar L., affected by amoebic gill disease (AGD) are resistant to re-infection. These observations were based upon a comparison of gross gill lesion abundance between previously infected and naïve control fish. Anecdotal evidence from Atlantic salmon farms in southern Tasmania suggests that previous infection does not protect against AGD as indicated by a lack of temporal change in freshwater bathing intervals. Experiments were conducted to determine if previous infection of Atlantic salmon with Neoparamoeba sp. would provide protection against challenge and elucidate the immunological basis of any protection. Atlantic salmon were infected with Neoparamoeba sp. for 12 days then treated with a 4-h freshwater bath. Fish were separated into two groups and maintained in either sea water or fresh water for 6 weeks. Fish were then transferred to one tank with a naïve control group and challenged with Neoparamoeba sp. Fish kept in sea water had lower mortality rates compared with first time exposed and freshwater maintained fish, however, these data are believed to be biased by ongoing mortalities during the sea-water maintenance phase. Phagocyte function decreased over exposure time and freshwater maintained fish demonstrated an increased ability to mount a specific immune response. These results suggest that under the challenge conditions herein described, antigen exposure via infection does not induce protection to subsequent AGD.

Effects of dopamine receptor D4 variation on alcohol and tobacco use and on novelty seeking: multivariate linkage and association analysis

The dopamine D4 receptor gene contains a polymorphic sequence consisting of a variable number of 48-base-pair (bp) repeats, and there have been a number of reports that this polymorphism is associated with variation in novelty seeking or in substance abuse and addictive behaviors. In this study we have assessed the linkage and association of DRD4 genotype with novelty seeking, alcohol use, and smoking in a sample of 377 dizygotic twin pairs and 15 single twins recruited from the Australian Twin Registry (ATR). We found no evidence of linkage or association of the DRD4 locus with any of the phenotypes. We made use of repeated measures for some phenotypes to increase power by multivariate genetic analysis, but allelic effects were still non-significant. Specifically, it has been suggested that the DRD4 7-repeat allele is associated with increased novelty seeking in males but we found no evidence for this, despite considerable power to do so. We conclude that DRD4 variation does not have an effect on use of alcohol and the problems that arise from it, on smoking, or on novelty seeking behavior.

Synthesis of Porous Emulsion-Templated Polymers Using High Internal Phase CO2-in-Water Emulsions

Highly porous emulsion-templated materials were synthesized by polymerization of concentrated CO(2)-in-water (C/W) emulsions. The method does not use any organic solvents, in either the synthesis or purification steps, and no solvent residues are left in the materials. It was found that the emulsion stability is strongly affected both by the nature of the surfactant and by the viscosity of the aqueous continuous phase. By optimizing these parameters, it was possible to generate a highly porous, low-density polyacrylamide material with a pore volume of 5.22 cm(3)/g, an average pore diameter of 9.72 microm, and a bulk density of 0.14 g/cm(3). We have broadened the scope of this approach significantly by identifying inexpensive hydrocarbon surfactants to stabilize the C/W emulsions (e.g., Tween 40) and by developing redox initiation routes that allow the synthesis to be carried out at modest temperatures and pressures (20 degrees C, 65 bar). We have also extended the method to the polymerization of monomers such as hydroxyethyl acrylate, which suggests that it is possible to prepare a range of solvent-free biomaterials by this route.

Pilot-scale evaluation of select nitrate removal technologies

Due to the extensive application of artificial nitrogen-based fertilizers and animal manure on land, many water agencies face problems of increasing concentrations of nitrate in groundwater. The contamination of groundwater by nitrate may pose a significant public health problem. The threat of methemoglobinemia is well documented and reflected in the US drinking water standard of 10 mg/L as nitrate-nitrogen. Approximately 45% of Saskatchewan's population use groundwater for drinking purposes, out of which, approximately 23% (230,000) are rural residents. The water used is made available from over 48,000 privately owned wells in regions where there is an extensive application of chemical fertilizers. Biological denitrification, ion exchange, and reverse osmosis (RO) processes were selected for a field study. Field studies were conducted on these processes. The sulfur/limestone autotrophic denitrification (SLAD) process was selected to achieve biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions. An ion exchange study was conducted using Ionac A554 which is a strong anion exchange resin. In the case of groundwater containing low sulfate concentrations, A554 offered high nitrate removal. However, the disposal of regenerant brine can be a problem. A reverse osmosis unit with Filmtec membrane elements (FT30-Element Family) was used in the study on nitrate removal. The unit effluent average nitrate concentration was less than the maximum allowable concentration.

Cefazolin does not accelerate gastric emptying in the critically ill

OBJECTIVE

To evaluate the effect of intravenous cefazolin on gastric emptying measured by the C-13 octanoic acid breath test.

DESIGN

Prospective, double-blind, cross-over, randomised, placebo-controlled trial.

SETTING

Mixed multidisciplinary intensive care unit in a university hospital.

PATIENTS

Fourteen critically ill, mechanically ventilated patients.

INTERVENTIONS

After a 4-h fast patients received either 50 mg cefazolin or 20 ml saline over 20 min immediately prior to measurement of gastric emptying. The next day the study was repeated with the alternative therapy.

MEASUREMENTS AND RESULTS

Breath samples were analysed for the concentration of (13)CO2 by mass spectrometer, and the gastric emptying coefficient (GEC) and half-emptying time (t(50)) were calculated. Results are mean (standard deviation). Data were analysed with the paired t-test (saline vs cefazolin). Two patients were excluded for technical problems. Twelve patients remained (six male/six female), aged 57 (+/-16) years, with an APACHE II score of 20 (+/-8). Both GEC and t(50) were unchanged after administration of cefazolin compared with placebo (t(50) cefazolin, 138 (+/-54) vs saline 122 (+/-46) min, P=0.32; GEC cefazolin 3.27 (+/-0.83) vs saline 3.55 (+/-0.6), P=0.24). Two patients had abnormal t(50) after saline and five after cefazolin. There was no order effect of the study day.

CONCLUSION

In mechanically ventilated patients, cefazolin had no effect on gastric emptying. These data do not support the use of low-dose cefazolin as a pro-kinetic agent in critically ill patients.

Inactivation of Listeria monocytogenes/Flavobacterium spp. biofilms using chlorine: impact of substrate, pH, time and concentration

AIMS

To determine the effect of chlorine on mixed bacterial biofilms on stainless steel (SS) and conveyor belt surfaces.

METHODS AND RESULTS

Biofilms were exposed to pH-adjusted (6.5) and non-pH-adjusted solutions of chlorine (200, 400 and 600 ppm) for either 2, 10 or 20 min and survivors enumerated. There were significant differences in cell death relating to chlorine concentration and exposure time for the cells attached to the SS, with solutions adjusted to pH 6.5 being more effective at reducing numbers. In contrast, on conveyor belt surfaces cell numbers decreased by less than two logs after 20 min regardless of treatment.

CONCLUSIONS

Chlorine effectiveness is dependent on its concentration, solution pH, exposure time, the nature of the surface and the microbial species present. SIGNIFICANCE AND IMPACT OF THE STUDY the interests of food safety it is important that sanitizer users are aware of the conditions that effect their performance.

Patterns of antropyloric motility in fed healthy preterm infants

BACKGROUND

Antropyloric motility is important for regulation of gastric emptying and has not been adequately characterised in premature infants.

AIM

To evaluate fed patterns of antropyloric motility in premature infants.

SUBJECTS

Forty three healthy premature infants, 30-38 weeks of postmenstrual age.

METHODS

Postprandial antropyloric motility was measured using a micromanometric feeding assembly (outer diameter 1.8 mm) incorporating a pyloric sleeve sensor. The occurrence of isolated pyloric pressure waves (IPPWs) and antral pressure wave sequences (PWSs) was characterised. Sequences were further classified as being antegrade, synchronous, antegrade-synchronous, and retrograde according to the direction of propagation.

RESULTS

A total of 7289 pressure wave events were recorded, 48% IPPWs and 52% PWSs (18% antegrade, 12% synchronous, 13% antegrade-synchronous, 2% retrograde, and 7% undefined). IPPWs predominated in the first postprandial hour, peaking at 30-60 minutes. PWSs predominated in the period after one hour postprandially. Mean (SEM) half gastric emptying time was 42 (4) minutes.

CONCLUSIONS

Monitoring of antropyloric motor patterns in healthy premature infants indicates that the neuroregulatory mechanisms responsible for the coordination of antropyloric motility and gastric emptying are well developed by 30 weeks of postmenstrual age.

Atypical multiple, papilliform, xanthomatous, cutaneous neoplasia in a goose (Anser anser)

An 18-month-old, male greylag goose was presented for assessment of multiple, semi-pedunculated cutaneous masses limited to non-feathered areas of skin. Initial biopsy and histopathology revealed a mesenchymal neoplasm suggestive of lipoblastomatosis or atypical xanthoma. Immunohistochemistry was unsuccessful in determining the tissue type of origin. Surgical resection of all masses was prevented by the mucocutaneous location of several masses. Chemotherapy using intralesion cisplatin was unsuccessful in resolving the masses but was well-tolerated by the goose. Serum lipid and lipoprotein analysis revealed a persistent hypercholesterolaemia and hypertriglyceridaemia without biochemical evidence of an underlying metabolic disease. The persistent hyperlipidaemia may have contributed to the formation of the masses identified in this case.

Noninvasive breath tests can detect alterations in gastric emptying in the mouse

BACKGROUND

Noninvasive breath tests may have significant utility for the measurement of gastric emptying in mice, but the tests' sensitivity for detection of changes in gastric emptying has not been evaluated.

MATERIALS AND METHODS

Hydroxypropyl methyl cellulose was incorporated into a liquid meal to delay gastric emptying, and mice were injected with erythromycin to accelerate emptying of a liquid or solid meal. All test meals were labelled with (13)C-acetic acid or (13)C-octanoic acid. Breath samples collected at intervals were analysed for (13)CO(2) content, and gastric emptying rates were calculated from the resultant (13)CO(2) excretion curves.

RESULTS

As predicted, hydroxypropyl methyl cellulose slowed emptying compared with water (14.21 +/- 0.94 min vs. 9.17 +/- 0.47 min, P < 0.001), while erythromycin treatment accelerated emptying of liquids (10.96 +/- 0.78 min vs. 16.41 +/- 1.94 min, P < 0.05) and solids (108.81 +/- 18.06 vs. 157.95 +/- 12.01 min, P < 0.05) compared with the saline injected controls.

CONCLUSIONS

These data indicate that in mice the breath test is sensitive enough to detect differences in gastric emptying induced by meal composition and pharmacological agents. Noninvasive measurement of gastric emptying in mice will be useful as a method to evaluate the effect of nutrients or drugs on the motility of the gastrointestinal tract.

Trials comparing early vs late extubation following cardiovascular surgery

We identified 10 randomized trials that compared alternative management approaches to patient care during and following cardiovascular surgery. One overall strategy involved a modification of anesthesia, in particular, a reduction in the dosage of fentanyl and benzodiazepine or the substitution of fentanyl for propofol (five randomized controlled trials [RCTs]). Pooled results show a shorter duration of ventilation (7 h) and a shorter duration of hospital stay (approximately 1 day) associated with lower anesthetic doses. The second strategy involved early vs late extubation once patients were admitted to the ICU (five RCTs). Pooled results show a shorter duration of ventilation (13 h) and a shorter duration of ICU stay (half a day) associated with early extubation. An additional 8 nonrandomized trials had findings that were consistent with the 10 RCTs. Reintubation, complications, and mortality rates were too low to draw conclusions about these outcomes. Overall, these studies indicate that anesthetic, sedation, and early-extubation strategies in selected cardiac surgery patients are associated with a shorter duration of mechanical ventilation and shorter lengths of ICU and hospital stays.

Trials of miscellaneous interventions to wean from mechanical ventilation

We found eight randomized controlled trials (RCTs) of miscellaneous interventions that were designed to facilitate the process of weaning from mechanical ventilation. The two RCTs of high-fat/low-carbohydrate enteral nutrition found favorable physiologic effects on CO2 production and respiratory quotient, rendering this type of nutrition potentially useful in patients with impaired ventilatory reserve; however, no conclusions can be made about the outcomes of the duration of ventilation and weaning success. The two RCTs of postextubation use of noninvasive ventilation are conflicting, showing potential short-term physiologic benefit in one study, but no benefit in terms of reintubation rates or other morbidity. These RCTs are less promising than other applications of noninvasive ventilation such as those in patients with COPD exacerbations. One RCT showed no improvement in success of weaning with exogenous growth hormone administration. In the setting of very frequent baseline blood gas analyses, one RCT of oximetry and capnography was associated with significantly fewer blood gas analyses. Biofeedback to enhance safe and rapid weaning showed a dramatically lower duration of ventilation in one RCT that did not report the weaning methods used. One RCT of preextubation acupuncture showed lower rates of laryngospasm in the acupuncture group. Overall, these studies were underpowered for clinically important outcomes. Multidisciplinary, patient-centered, holistic, and non-pulmonary approaches to weaning may provide additional safe, effective adjunctive methods of hastening liberation from mechanical ventilation.

Trials of corticosteroids to prevent postextubation airway complications

We identified three randomized controlled trials (RCTs) that addressed whether preextubation steroid administration reduces postextubation complications in children. The pooled analysis of primary extubation in children demonstrated significantly less stridor (relative risk [RR], 0.57; 95% confidence interval [CI], 0.40 to 0.81) and a trend toward less reintubation (RR, 0.50; 95% CI, 0.02 to 13.87) with corticosteroids. One non-RCT in children who had failed extubation the first time found a significant reduction in duration of prolonged reintubation (> or = 6 days) and in failed reextubations. The four RCTs in adults reported very low reintubation rates, and no conclusions can be drawn. Only one RCT assessed postextubation stridor and found little difference. Overall, we found that corticosteroids decreased the risk of postextubation stridor in children by about 40%. However, the effect of corticosteroids in children and adults to reduce postextubation complications such as reintubation is uncertain.