Hypocapnia Attenuates, and Nitrous Oxide Disturbs the Cerebral Oximetric Response to the Rapid Introduction of Desflurane

The aim of this study was to develop a nonlinear mixed-effects model for the increase in cerebral oximetry (rSO2) during the rapid introduction of desflurane, and to determine the effect of hypocapnia and N2O on the model. Twelve American Society of Anesthesiologist physical status class 1 and 2 subjects were allocated randomly into an Air and N2O group. After inducing anesthesia, desflurane was then increased abruptly from 4.0 to 12.0%. The PETCO2, PETDESF and rSO2 were recorded at 12 predetermined periods for the following 10 min. The maximum increase in rSO2 reached +24-25% during normocapnia. The increase in rSO2 could be fitted to a four parameter logistic equation as a function of the logarithm of PETDESF. Hypocapnia reduced the maximum response of rSO2, shifted the EC50 to the right, and increased the slope in the Air group. N2O shifted the EC50 to the right, and reduced the slope leaving the maximum rSO2 unchanged. The N2O-effects disappeared during hypocapnia. The cerebrovascular reactivity of rSO2 to CO2 is still preserved during the rapid introduction of desflurane. N2O slows the response of rSO2. Hypocapnia overwhelms all the effects of N2O

A 1.9-GHz CMOS power amplifier using three-port asymmetric transmission line transformer for a polar transmitter

A 1.9-GHz CMOS differential power amplifier for a polar transmitter is implemented with a 0.18-mu m RF CMOS process. All of the matching components, including the input and output transformers, are fully integrated. The concepts of injection locking and variable load are applied to increase the efficiency and dynamic range of the amplifier. An asymmetric three-port transmission line transformer is proposed to embody the variable load effectively. The power amplifier achieved a power-added efficiency of 40% at a maximum output power of 32 dBm. The dynamic range was 20 dB at supply voltages ranging from 0.5 to 3.3 V. The improvement of the low power efficiency was 290% at an output power of 16 dBm.ope

A 1.9-GHz triple-mode class-E power amplifier for a polar transmitter

A 1.9-GHz CMOS power amplifier for polar transmitters was implemented with a 0.25-mu m radio frequency CMOS process. All the matching components, including the input and output transformers, were fully integrated. The concepts of mode locking and adaptive load were applied in order to increase the efficiency and dynamic range of the amplifier. The amplifier achieved a drain efficiency of 33% at a maximum output power of 28 dBm. The measured dynamic range was 34 dB for a supply voltage that ranged from 0.7 to 3.3 V. The measured improvement of the low power efficiency was 140% at an output power of 16 dBm.ope

Fully integrated 1.9-GHz CMOS power amplifier for polar transmitter applications

A 1.9-GHz CMOS differential power amplifier for polar transmitter applications was implemented with a 0.25 mu m RF CMOS process. All of the matching components, input transformer, and output transformer are fully integrated with 50 Omega input and output matching. Each power transistor in each differential branch is split again and controlled separately to obtain a high power mode and a low power mode. The amplifier achieved a drain efficiency of 32% at the maximum output power of 29.5 dBm. The dynamic range is measured at approximately 275 dB with a supply voltage range of 0.7 similar to 3.3 V.ope