Evaluation of four airway training manikins as simulators for inserting the LMA Classictm*

Airway manikins have traditionally been used for teaching mask ventilation and tracheal intubation. There is an increasing need to use manikins for training in procedures such as insertion of the laryngeal mask airway. We have assessed four new airway training manikins (latest versions of the Airway Trainer (Laerdal, Norway), Airway Management Trainer (Ambu, UK), 'Bill 1' (VBM, Germany) and Airsim (Trucorp, Ireland)) as simulators for insertion of the LMA Classic laryngeal mask airway. Twenty volunteer anaesthetists inserted a size-4 laryngeal mask airway five times into each of the four manikins, in random order. Each insertion was assessed using objective and subjective tests. Subjective assessment varied widely but overall assessment indicated that the Airway Management Trainer was the poorest simulator for insertion of the laryngeal mask airway. The 'Bill 1' and Airsim manikins performed best as simulators for insertion of the laryngeal mask airway, although realistic ventilation with 'Bill 1' was not possible.

Color discrimination in carriers of color deficiency

Carriers of X-linked color vision deficiencies have previously been reported to exhibit mild abnormalities of color matching and discrimination. In a sample of 55 carriers of protan and deutan deficiencies and 55 age-matched normal controls, we measured chromatic discrimination along a red-green axis. We found that discrimination was impaired in the case of carriers of deutan deficiencies (which affect the middle-wave-sensitive cones of the retina), but was normal in the case of carriers of protan deficiencies (which affect the long-wave-sensitive cones). We argue that this result can be explained by the difference in the relative numbers of middle- and long-wave cones in heterozygous retinae: the imbalance of the two cone types is predicted to be much greater in the case of the deutan heterozygote than in the case of the protan heterozygote. In future studies it will be necessary to consider separately the two types of heterozygote.

A study of titanium release into body organs following the insertion of single threaded screw implants into the mandibles of sheep

BACKGROUND

Titanium is generally considered a safe metal to use in implantation but some studies have suggested that particulate titanium may cause health problems either at the site overlying the implant or in distant organs, particularly after frictional wear of a medical prosthesis. It was the purpose of this investigation to study the levels of dissemination of titanium from threaded screw type implants following placement of single implants in sheep mandibles.

METHOD

Twelve sheep were implanted with a single 10x3.75mm self-tapping implant for time intervals of one, four and eight to 12 weeks. Four unoperated sheep served as controls. Regional lymph nodes, lungs, spleens and livers were dissected, frozen and subsequently analysed by Graphite Furnace Atomic Absorption Spectroscopy.

RESULTS

Results associated with successful implants showed no statistically significant different levels of titanium in any organ compared to controls, although some minor elevations in titanium levels within the lungs and regional lymph nodes were noted. Two implants failed to integrate and these showed higher levels of titanium in the lungs (2.2-3.8 times the mean of the controls) and regional lymph nodes (7-9.4 times the levels in controls).

CONCLUSIONS

Debris from a single implant insertion is at such a low level that it is unlikely to pose a health problem. Even though the number of failed implants was low, multiple failed implants may result in considerably more titanium release which can track through the regional lymph nodes. Results suggest that sheep would be an excellent model for following biological changes associated with successful and failed implants and the effect this may have on titanium release.

A multi-institutional analysis of laparoscopic orchidopexy

OBJECTIVE

To combine and analyse the results from centres with a large experience of laparoscopy for the impalpable testis with small series, to determine the expected success rate for laparoscopic orchidopexy.

METHODS

A questionnaire was distributed to participating paediatric urologists; each contributor retrospectively reviewed the clinical charts for their cases of therapeutic laparoscopy for an impalpable testis, detailing 36 variables for each patient. The data were collated centrally into a computerized database. For inclusion, the testis was intra-abdominal (including 'peeping' at the internal ring) at laparoscopic examination, was not managed through an open approach and did not undergo orchidectomy. Three surgical groups were assessed, with success defined as lack of atrophy and intrascrotal position: group 1, primary laparoscopic orchidopexy; group 2, a one-stage Fowler-Stephens (F-S) orchidopexy; and group 3, a two-stage F-S orchidopexy.

RESULTS

Data were gathered from 10 centres in the USA, covering the period 1990-1999; 252 patients representing 310 testes were included and overall, 15.2% were lost to follow-up. There was no significant difference between success rates in the larger and smaller series. Atrophy occurred in 2.2% of 178 testes, 22.2% of 27 testes and 10.3% of 58 testes in groups 1-3, respectively. Testes were not in a satisfactory scrotal position in 0.6%, 7.4% and 1.7% of groups 1-3, respectively. The mean follow-up for each group was 7.7, 8.6 and 20.0 months, respectively. The overall success for all groups was 92.8% (97.2% group 1; 74.1% group 2; 87.9% group 3), with an atrophy rate of 6.1%.

CONCLUSION

Laparoscopic orchidopexy for the intra-abdominal testis, in both large and small series, can be expected to have a success rate higher than that historically ascribed to open orchidopexy. Within this series, single-stage F-S laparoscopic orchidopexy resulted in a significantly higher atrophy rate than the two-stage repair. However, when considering both F-S approaches, the laparoscopic approach gave greater success than previously reported for the same open approaches. Despite the weaknesses inherent in a retrospective unrandomized study, we conclude that laparoscopic orchidopexy is, if not the procedure of choice, an acceptable and successful approach to the impalpable undescended testicle.

The influence of diet and exercise on muscle and plasma glutamine concentrations

PURPOSE

This study examined the relationship between muscle glutamine, muscle glycogen, and plasma glutamine concentrations over 3 d of high-intensity exercise during which dietary carbohydrate (CHO) intake varied.

METHODS

Five endurance-trained men completed two exercise trials in randomized order, over a 14-d period. Each trial required subjects to perform 50 min of high-intensity continuous and interval exercise on three consecutive days while consuming a diet that provided 45% of the energy as CHO or a diet in which CHO provided 70% of the total energy. Four days of inactivity and consumption of a 55% CHO diet separated the two randomized trials. Menus and food were provided for the subjects and all food and drink consumed were weighed and recorded for later analysis. Before exercise on the first day of each trial, at the start of exercise on day 3 and on completion of exercise on day 3, muscle was biopsied from the vastus lateralis for the analysis of glutamine and glycogen concentrations. Venous blood was sampled before and twice after exercise on each day for the analysis of plasma glutamine and cortisol concentrations.

RESULTS

Mean plasma glutamine concentration was significantly higher during the 70% CHO exercise trial when compared with the 45% CHO trial (P < 0.05). Glycogen decreased by the same magnitude during both trials and there was no relationship between changes in plasma glutamine and changes in muscle glycogen concentration. Muscle glutamine concentration did not change in either trial.

CONCLUSIONS

These data suggest that the influence of carbohydrate intake upon the concentration of plasma glutamine is not mediated through the concentration of intramuscular glycogen.

A new type of hexaosmium boride cluster, H3Os6(CO)16B, that does not conform to electron counting rules

A new type of hexaosmium boride cluster, H3Os6(CO)16B, was produced in the thermolysis of H3Os3(CO)9(BCO). This complex is an 86 valence electron cluster, but the Os6 framework does not possess one of the geometries previously observed for Os6 clusters that have 86 valence electrons. [HOs6(CO)18]- and [Os6(CO)18]2- have octahedral frameworks while that of H2Os6(CO)18 is a face-capped square pyramid. The Os6 framework of H3Os6(CO)16B can be viewed as being derived from a pentagonal bipyramid that is missing one equatorial vertex. It contains an interior boron atom. Alternatively, it can be viewed like the 84 valence cluster Os6(CO)18 as either a bicapped tetrahedron, with a boron atom residing on the edge of the tetrahedron that is common to the capped faces, or a face-capped trigonal bipyramid, with the boron atom on an equatorial edge of the bipyramid that is also an edge of the capped face. H3Os6(CO)16B was characterized by 1H, and 11B, 13C NMR, IR, and mass spectroscopies and single-crystal X-ray diffraction analysis. The molecular structure was determined from two separate crystals. The analysis of each crystal yielded virtually identical structures, but their volumes differed by 36 A3 due to differences in packing in the unit cell. Data for crystal I of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.954(2) A, b = 15.780(4) A, c = 16.448(3) A, beta = 91.07(1) degrees, Z = 4. Data for crystal II of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.927(2) A, beta = 16.623(2) A, b = 16.0233(10) A, beta = 97.78(1) degrees, Z = 4.

Shift in Rayleigh matches after adaptation to monochromatic light of various intensities

The action spectrum for inducing a long-lasting protan shift in colour matches was investigated. Rayleigh matches were measured before and after 30 min adaptation to monochromatic light of 520, 550, 580 or 620 nm. For each wavelength, seven retinal illuminances, ranging from 3.0 to 5.0 log td, were chosen in random order. Results for one colour-normal observer show that the shift in Rayleigh match after adaptation increases monotonically as a function of the luminance of the adapting light. The dynamic response range is from 3.3 to 4.7 log td. The wavelength of the adapting light had no systematic influence on the form of the response function. The results imply that the effect is triggered by light absorbed in the photopigments themselves.

Maintenance of motor pattern phase relationships in the ventilatory system of the crab

The central pattern generator responsible for the gill ventilation rhythm in the shore crab Carcinus maenas can produce a functional motor pattern over a large (eightfold) range of cycle frequencies. One way to continue to generate a functional motor pattern over such a large frequency range would be to maintain the relative timing (phase) of the motor pattern as cycle frequency changes. This hypothesis was tested by measuring the phase of eight events in the motor pattern from extracellular recordings at different rhythm frequencies. The motor pattern was found to maintain relatively constant phase relationships among the various motor bursts in this rhythm over a large (sevenfold) range of cycle frequencies, although two phase-maintaining subgroups could be distinguished. Underlying this phase maintenance is a corresponding change in the time delay between events in the motor pattern ranging from 470 to 1800 ms over a sevenfold (300&shy;2100 ms) change in cycle period. Intracellular recordings from ventilatory neurons indicate that there is very little change in the membrane potential oscillation in the motor neurons with changes in cycle frequency. However, recordings from nonspiking interneurons in the ventilatory central pattern generator reveal that the rate of change of the membrane potential oscillation of these neurons varies in proportion to changes in cycle frequency. The strict biomechanical requirements for efficient pumping by the gill bailer, and the fact that work is performed in all phases of the motor pattern, may require that this motor pattern maintain phase at all rhythm frequencies.

Long-Term Changes in Colour Matching Functions after Exposure to Artificial Sunlight

We have previously reported that relatively short exposures (30 to 60 min) to either sunlight or artificial sunlight are sufficient to shift Rayleigh matches for several hours in the protan direction (1995 Investigative Ophthalmology and Visual Science36 392). We have subsequently found that this effect cannot be explained by either an alteration in (i) the orientation of photoreceptors, ie no change was found in Stiles — Crawford I before and after adaptation (1995 Perception24 Supplement, 11), or by an alteration in (ii) the density of an observer's macular pigment. In order to distinguish more generally between a change in a pre-receptoral filter and a change in the spectral sensitivity of M or L cones, we are currently obtaining colour matching functions between 570 and 620 nm. Measurements are made before and after 45-min exposure to a white field receiving an illumination of about 40 000 lux from an arc lamp. The mixture primaries are 550 and 690 nm set at 100 td. The stimulus field subtends 2 deg. Matches are made by a temporal substitution method and two staircases are randomly interleaved. The standard wavelengths are randomised.

Repair of obliterative vesicourethral stricture after radical prostatectomy: a technique for preservation of continence

We present the open surgical repair of complete obstruction of the bladder neck unresponsive to endoscopic management. By combining abdominal and perineal dissection, partial pubectomy, and omental wrapping, repeat anastomosis is possible without the need for bladder tubularization. Two patients have been repaired successfully. Although both men presented with indwelling suprapubic tubes and a defect of greater than 1.5 cm, they are now voiding normally at 18 and 7 months post-operatively without the need for pads, medication, or instrumentation. Complete obliteration of the bladder neck after radical prostatectomy can be functionally reconstructed. Postoperative continence will depend on the function of the membranous urethra. If incontinence occurs, this can be managed in a reconstructed open urethra.

Rayleigh matches and unique green

There are recurrent reports that Rayleigh matches are bimodally distributed in the colour-normal male population. Similar claims have been made for the distribution of the spectral locus of unique green. Moreover, a positive correlation has sometimes been reported between Rayleigh matches and unique green. Using a computer-controlled Maxwellian colorimeter and bias-free psychophysical methods, we measured both variables for 97 colour-normal male observers. We do not find a bimodal distribution either of Rayleight matches or of settings of unique green. Nor do we find any correlation between the two variables. However, we do observe a very significant relationship between the lightness of the subject's iris and the wavelength that he judges to be unique green.

[Problems of population in Tibet]

"The debate on Tibet's population and population issues is not a new one in the demographic literature. Drawing on the data of recent population censuses in China the author of the study gives a review of the problems. He uses documents--issued mostly in English--by means of which he can get a better insight into the reasons of the lack of data and into the assessment of the available data." (SUMMARY IN ENG)

A study of women heterozygous for colour deficiencies

We have examined the colour vision of 43 female subjects in the age range 30-59 yr of whom 31 were obligate carriers of various forms of colour deficiency and the rest were women who had no known colour-deficient relatives. In the case of all the carriers we established the phenotypes of their colour-deficient sons. As a group, carriers made significantly more errors on the Ishihara plates and showed enlarged matching ranges on the Nagel anomaloscope, but we could not replicate earlier reports of increased error scores on the Farnsworth-Munsell 100-Hue test or of systematic shifts in Rayleigh match mid-points. We did find that the colour matches of carriers of deuteranomaly were significantly displaced from those of normals in a ratio-matching task in which a mixture of 546 and 600 nm was matched with a mixture of 570 and 690 nm. Owing to X-chromosome inactivation, women who are heterozygous for anomalous trichromacy ought to have at least four types of cone in their retinae and we ask whether this affords them an extra dimension of colour vision, by analogy to New World monkeys where heterozygous females gain trichromacy in a basically dichromatic species. Many carriers of anomalous trichromacy exhibited no evidence for tetrachromacy, in that they accepted large-field Rayleigh matches following a rod bleach and they were unable to set unique matches in our ratio-matching task. However, eight carriers of anomalous trichromacy--and no other subject--refused large-field Rayleigh matches; and we found one carrier of deuteranomaly who was apparently able to make unique matches in the ratio-matching task.

The Nagel anomaloscope and seasonal variation of colour vision

In 1948 the German physicist, Manfred Richter, reported that colour vision has a seasonal variation. For four colour-normal subjects, he found a sinusoidal variation in the proportion of red and green required to match a monochromatic yellow, the equation known as the 'Rayleigh match'. In summer, subjects required more red in their mixture. The measurements were made with the Nagel anomaloscope, an instrument introduced in 1907 and which today, essentially unchanged, remains the definitive clinical instrument for classifying the many phenotypic variations in colour vision. The variation that Richter recorded in the red-green ratio was large (three Nagel units), and it now takes on fresh interest because it is comparable in size to the difference in Nagel settings later reported between normal observers of different genetic types. We have been able to replicate Richter's result, but report here that it is almost certainly instrumental: the Nagel anomaloscope proves to be very sensitive to ambient temperature.