Continuous Measurement of Multiple Inert and Respiratory Gas Exchange in an Anaesthetic Breathing System by Continuous Indirect Calorimetry

A method was tested which permits continuous monitoring from a breathing system of the rate of uptake of multiple gas species, such as occurs in patients during inhalational anaesthesia. The method is an indirect calorimetry technique which uses fresh gas rotameters for control, regulation and measurement of the gas flows into the system, with continuous sampling of mixed exhaust gas, and frequent automated recalibration to maintain accuracy. Its accuracy was tested in 16 patients undergoing pre-cardiopulmonary bypass coronary artery surgery, breathing mixtures of oxygen/air and sevoflurane with/without nitrous oxide, by comparison with the reverse Fick method. Overall mean bias [95% confidence interval (CI)] of rate of uptake was 17.9 [7.3 to 28.5] ml min⁻¹ for oxygen, 0.04 [−0.42 to 0.50] ml min⁻¹ for sevoflurane, 10.9 [−16.1 to 37.8] for CO₂, and 8.8 [−14.8 to 32.4] ml min⁻¹ for nitrous oxide where present. The method proved to be accurate and precise, and allows continuous monitoring of exchange of multiple gases using standard gas analysis devices. Stuart-Andrews C, Peyton P, Humphries C, Robinson G, Lithgow B. Continuous measurement of multiple inert and respiratory gas exchange in an anaesthetic breathing system by continuous indirect calorimetry.     

Polymer‐free versus permanent polymer‐coated drug eluting stents for the treatment of coronary artery disease: A meta‐analysis of randomized trials

Background

Polymer‐free drug eluting stents (PF‐DES) were developed, in part, to overcome risk of late ischemic events observed with permanent polymer‐coated DES (PP‐DES). However, trial results are inconsistent with longer‐term safety and efficacy of PF‐DES remaining unknown. We performed a meta‐analysis of randomized trials assessing outcomes of patients receiving PF‐DES versus PP‐DES for treatment of coronary artery disease (CAD).

Methods

Electronic searches were performed for randomized trials comparing outcomes between PF‐DES and PP‐DES. Trials reporting major adverse cardiovascular events (MACE), myocardial infarction (MI), stent thrombosis (ST), all‐cause death, target lesion/vessel revascularization (TLR/TVR), and late lumen loss (LLL) were included. Analyses were performed at longest follow‐up and landmarked beyond 1‐year.

Results

Twelve trials (6,943 patients) were included. There was no significant difference in MACE between PF‐DES and PP‐DES at longest follow‐up (Odds Ratio [OR] 0.96, 95%CI 0.85‐1.10, P = 0.59) or landmark analysis beyond 1‐year (OR 0.96, 95%CI 0.76‐1.20, P = 0.70). Although PF‐DES were associated with a significant reduction in all‐cause death (OR 0.85, 95%CI 0.72‐1.00, P < 0.05), this effect was not present on landmark analysis beyond 1‐year (OR 0.89, 95%CI 0.73‐1.10, P = 0.30). There were no differences observed for MI (OR 1.00, 95%CI 0.77‐1.28, P = 0.99) or ST (OR 0.95, 95%CI 0.54‐1.68, P = 0.86), with similar efficacy outcomes including TVR (OR 1.07, 95%CI 0.91‐1.26, P = 0.42), TLR (OR 1.03, 95%CI 0.88‐1.21, P = 0.68) and angiographic LLL (pooled mean difference 0.01 mm, 95%CI ?0.08 to 0.11, P = 0.76).

Conclusions

PF‐DES are as safe and efficacious as PP‐DES for the treatment of patients with CAD, but do not significantly reduce late ischemic complications.

     

Clinical evaluation of four composite resins in posterior teeth. Five-year results

Four different composite resins (three small particle and one microfill) were placed in 106 posterior teeth and followed over a five-year period. Colour and marginal discoloration characteristics were assessed from standard photographs, and wear evaluated by standardized measurement of cavity wall exposure and scanning electron microscopy of replicas. The colour of the materials changed, but not to an unacceptable degree, over the five-year period, and marginal discoloration increased slightly. The wear rate of the four materials was similar, and appeared to decrease after about 2-4 years. Some materials exhibited surface damage, and some of the microfill restorations failed catastrophically.     

Comparison of denture acrylic resins cured by boiling water and microwave energy

Transverse strength, hardness, water sorption, loss of mass by leaching and porosity were measured in accordance with Australian Standards on acrylic denture base resins cured by boiling water and microwave energy. The level of residual monomer measured by extraction in acetone and the degree of cross-linking by immersion in chloroform were also studied. Results indicated similar physical properties and identical microstructures in the resins cured by the two methods. Using a previously recommended microwave curing programme, porosity was observed in thick specimens with a cross-section of 14 mm × 10 mm. However, the microwave programme can be optimized to prevent porosity without prolonging the curing time or sacrificing the physical properties of the resins by starting the curing process at low wattage.