The incidence and risk factors of difficult mask ventilation
ABSTRACT The ability to ventilate and oxygenate a patient using a bag-mask breathing system may be lifesaving in the case of failure of the initial intubation attempt. In this study, we aimed to determine the incidence of difficult mask ventilation (DMV) and to find preoperative risk factors for this procedure.
Based on methods used for overcoming some difficulties with bag-mask ventilation (MV), classification has been made into four categories: easy MV, awkward MV, difficult MV, and impossible MV. A univariate analysis was performed to identify potential risk factors predicting DMV, followed by a stepwise forward binary logistic regression, and the odds ratio and 95% confidence interval were calculated.
A total of 576 patients were studied. Incidence of easy MV, awkward MV, and difficult MV were found to be 75.5% (n = 435), 16.7% (n = 96), and 7.8% (n = 45), respectively. Height, weight, age, male gender, increased Mallampati class, history of snoring, lack of teeth, and beard were found to be DMV risk factors (P < 0.05). Using a multivariate analysis, Mallampati class 4, male, history of snoring, age, and weight were found to be significantly associated with DMV. Although the incidence of DMV in general was 7.8% (n = 45), the incidence of DMV among patients with difficult intubation (n = 123) was found to be 15.5% (n = 19).
Mallampati class 4, male patients, history of snoring, increasing age, and increasing weight were found to be risk factors for DMV in our study.
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ABSTRACT: An important restriction to a broader application of continuous wave radar systems for long-range measurement is their inherent sensitivity against strong nearby reflections. These often cause a receiver saturation and thus make target detection impossible. One approach to optimize the signal-to-noise ratio (S/N) and to improve the system performance of CW radar is the use of spatial filtering techniques /1,2/. The advantageous implementation of frequency hopping of the transmitter carrier signal was demonstrated /3/. In combination with a pseudo noise binary phase shift keying (PNBPSK) of the RF carrier a CW radar with high range resolution is possible. A suitable correlation receiver is realized by a surface acoustic wave (SAW) convolver. The dynamic capabilities of such a system are analysed. The results show that the limits of the system are given by the physical data of the convolver.Microwave Conference, 1987. 17th European; 10/1987
Conference Paper: An improved online delay evaluation for networked control systems[Show abstract] [Hide abstract]
ABSTRACT: Due to communication network introduced into control systems, it arouses many problems. The most important one is network-induced delays. These delays deteriorate the performance of the systems. Worse, they may be a potential source of instability for the systems. In order to compensate for these delays, an improved online delay evaluation method is presented. By this method we can get the exact delays in the control loops, which is based on the compensation information of the controller. Depending on these delay values, we can modify the parameters of the controller, so as to ensure the desired performance of control systems. Experiment results show that this method is valid.Intelligent Control and Automation, 2004. WCICA 2004. Fifth World Congress on; 07/2004