Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers.

Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging.

The automatic implantable cardioverter-defibrillator. Implications for anaesthetists.

This paper describes the anaesthetic management of a patient who had an automatic implantable cardioverter-defibrillator. The working principles of the device, the indications for its insertion and the postoperative complications, are discussed. An increasing number of cardioverter-defibrillators are being implanted in the UK. At least two general anaesthetics are required for each patient; one for implantation of the device and a second for testing its efficiency in terminating ventricular tachycardia and ventricular fibrillation. In future, the number of patients presenting for noncardiac surgical procedures is likely to increase, therefore every anaesthetist should be aware of the problems involved in management.

The effect of propofol on the neutrophil respiratory burst.

We have examined the effect of propofol on the neutrophil respiratory burst. Chemiluminescence was used as a measure of the respiratory burst following stimulation with 10(-5) M N-formyl-L-methionyl-L-leucyl-L-phenylalanine. Propofol 1.25, 2.5 and 5.0 x 10(-5) M inhibited neutrophil chemiluminescence by 29.6, 43.0 and 57.6%, respectively, in neutrophils prepared from healthy adult volunteers, and by 25.5, 37.4 and 54.7% in cells from patients with severe sepsis. We conclude that propofol interferes with the ability of human neutrophils to generate reactive oxygen species.

Nitric oxide: description of a pipeline delivery system.

We describe a pipeline system suitable for the delivery of nitric oxide gas to an 18-bed intensive care unit. The pipeline was developed and installed according to the current UK regulations HTM 2022, which relates to the supply of piped medical gases. Where HTM 2022 did not specify the appropriate standard, we consulted widely to achieve a safe solution. We continue to monitor all aspects of the performance of the pipeline to ensure safe operating practices and recommend changes to the standards.

Extravascular lung water and acute respiratory distress syndrome--oxygenation and outcome.

We studied eleven consecutive patients to assess the influence of extravascular lung water on clinical outcome. All patients were mechanically ventilated using a standardized protocol. Inspired oxygen concentration was adjusted to an initial target PaO2 of greater than 8.0 kPa (60.8 mmHg). All patients received inhaled nitric oxide (NO) at a concentration of 20 ppm. Extravascular lung water index (EVLWI) was measured by a dual indicator technique (COLD Z-021 monitoring system, Pulsion, Munich, Germany). Patients were managed with fluids and inotropes according to a standard protocol. Median age was 45 (range 27-60) years, mean APACHE II score on admission 31 (range 17-36), duration of mechanical ventilation 15 (range 6-28) days, mean admission Murray lung injury score 2.5 (range 2-3) and admission EVLWI 20.8 (range 8.7 to 54.7) ml.kg-1. The only variables independently predictive of PaO2/FiO2 ratio were serum albumin (B = 1.7 +/- 1.61) and EVLWI (B = -2.1 +/- 0.47), r2 = 0.33, P < 0.0001. In severe ARDS, (PaO2/FiO2 < 150 mmHg), mean EVLWI was 24.4 (22.4 to 26.4, 95% confidence intervals) ml.kg-1 compared with 15.1 (12.2 to 18.0) ml.kg-1 during moderate ARDS (P < 0.001). Serum albumin likewise differed, 29.4 (27.6 to 31.2) vs 35.1 (31.8 to 38.4) g.l-1, P < 0.005. PAOP was higher during periods of poor oxygenation, 12.7 (11.9 to 13.5) vs 9.3 (7.9 to 10.7) mmHg, P < 0.001. The four survivors had greater initial EVLWI than non-survivors, 31 (24.1 to 37.9) vs 20.7 (16.0 to 25.4) ml.kg-1, P = 0.034 and showed a greater reduction in lung water, 15.2 (9.3 to 21.1) vs 5.4 (2.1 to 8.7) ml.kg-1, P = 0.013.