Pre-oxygenation in pregnancy: the effect of fresh gas flow rates within a circle breathing system.

We have investigated the effect of oxygen flow rate on pre-oxygenation in pregnant patients at term using a circle system. Twenty patients presenting for elective Caesarean section maintained tidal volume breathing through a standard circle system for 3 min. Subjects were pre-oxygenated using oxygen flow rates of 5 l.min(-1), 10 l.min(-1) and 15 l.min(-1) presented in random order. The mean (SD) fractional end-tidal oxygen at the end of 3 min was 0.86 (0.07) for 5 l.min(-1), 0.92 (0.05) for 10 l.min(-1)and 0.90 (0.09) for 15 l.min(-1) (p < 0.001). Entrainment of air occurred in 22% of pre-oxygenation sessions. Oxygen flow rates of 10 l.min(-1) or above provide optimal pre-oxygenation using a circle system in term parturients. In our study, entrainment of air occurred in a surprisingly high percentage of cases.

Use of the HemoCue near patient testing device to measure the concentration of haemoglobin in suction fluid at elective caesarean section.

We have investigated the suitability of the HemoCue photometer to measure the concentration of haemoglobin in suction fluid obtained at elective caesarean section in 30 women. Laboratory analysis was used as a gold standard against which values generated by the HemoCue were compared. We used the method of Bland and Altman to analyse the data. The bias and the limits of agreement were -0.013 and -0.39 to 0.36 mg x dl(-1) respectively, indicating a good level of agreement. Mean (SD) total blood loss calculated using these data, combined with the weight of the swabs, was consistently greater than clinical estimation: 768 (496) ml versus 506 (249) ml respectively (p < 0.001). We have found that the HemoCue near patient testing device may be used to estimate blood loss accurately in the suction fluid obtained at elective Caesarean section.

The effect of temporary reductions in incubation temperature on growth characteristics and lipid utilisation in the chick embryo.

The effect(s) of finite exposure(s) to 22.0 degrees C on embryo weight gain, 3rd tarsus length, transfer of lipid from the yolk and uptake of specific lipid components by the liver, were measured in the chick embryo. Embryo growth was completely suspended over the period of temperature reduction, but resumed unimpaired when the optimum temperature of 37.5 degrees C was restored. Two successive periods of embryonic exposure to 22.0 degrees C (36 h at d 3 followed by 24 at d 10) were additive in their effect on growth retardation. Embryos subjected to temperature reductions on d 3 of incubation displayed significant changes in lipid concentrations and polyunsaturated fatty acid profiles within the liver when measured at d 18 of incubation. Yolk lipid uptake was significantly reduced but not suspended by embryonic exposure to 22.0 degrees C. It is suggested that the observed suspension of embryonic development was the result of a temperature dependent reduction in metabolism according to a Q10 approximately 2, which is typical of an ectothermic organism.

Body size and cell size in Drosophila: the developmental response to temperature.

In Drosophila, like most ectotherms, development at low temperature reduces growth rate but increases final adult size. Cultures were shifted from 25 degrees C to low (16.5 degrees C) or to high (29 degrees C) temperature at regular intervals through larval and pupal stages, and the flies of both sexes showed an increase or decrease, respectively, in the size of thorax, wing and abdominal tergite. Size changes in the wing blade resulted from changes in the size of the epidermal cells (with only a small increase in cell number in males reared at low temperature). The temperature-shifts became less effective as they were made at successively later developmental stages, demonstrating a cumulative effect of temperature on adult size. The thorax and wing develop from the same imaginal disc, with most cell division occurring in larval stages, but they differ in timing of temperature sensitivity, which extends only to pupariation or into the late pupal stage, respectively. Growth of the adult abdomen occurs largely after pupariation but its size is temperature-sensitive through both larval and pupal stages. We discuss growth control in Drosophila and the likely effects of temperature on food assimilation, growth efficiency and allocation of nutrients to the production of different tissues.