机械通气患者呼吸机相关性肺炎临床分析与护理

目的探讨呼吸机相关性肺炎的临床相关因素及病原学特点,以指导临床防治。方法对100例呼吸机患者的呼吸机管路、下呼吸道感染病菌的菌种种类、呼吸机时间进行统计,分析与呼吸机相关性肺炎发病的因素。结果呼吸机管路和下呼吸道病原菌构成比具有同源性表现,呼吸机相关性肺炎发生率为36%,使用呼吸机时间长短与呼吸机相关性肺炎发生率呈正相关(P0.01)。结论呼吸机相关性肺炎与多种临床因素有关,使用时间越长,发病率越高。     

Mechanical work of breathing during maximal voluntary ventilation

With the use of the esophageal balloon technique, the workingcapacity of the respiratory muscles was assessed in four normal subjects by measuring the work per breath (W) and respiratory power() during maximal voluntary ventilationwith imposed respiratory frequencies (f) ranging from 20 to 273 cycles/min. Measurements were made in a body plethysmograph to assessthe work wasted as a result of alveolar gas compressibility(Wg'). In line with other types of human voluntary muscleactivity, W decreased with increasing f, whereas exhibited a maximum at f of ~100cycles/min. Up to this f value, Wg' was small relative to W. Withfurther increase in f, the Wg'/W ratio increased progressively,amounting to 8-22% of at f of 200 cycles/min.

     

Mechanical ventilation for imaging the small animal lung

This review emphasizes some of the challenges and benefits of in vivo imaging of the small animal lung. Because mechanical ventilation plays a key role in high-quality, high-resolution imaging of the small animal lung, the article focuses particularly on the problems of ventilation support, control of breathing motion and lung volume, and imaging during different phases of the breathing cycle. Solutions for these problems are discussed primarily in relation to magnetic resonance imaging, both conventional proton imaging and the newer, hyperpolarized helium imaging of pulmonary airways. Examples of applications of these imaging solutions to normal and diseased lung are illustrated in the rat and guinea pig. Although difficult to perform, pulmonary imaging in the small animal can be a valuable source of information not only for the normal lung, but also for the lung challenged by disease.     

Mechanical ventilation: lessons from the ARDSNet trial

The acute respiratory distress syndrome (ARDS) is an inflammatory disease of the lungs characterized clinically by bilateral pulmonary infiltrates, decreased pulmonary compliance and hypoxemia. Although supportive care for ARDS seems to have improved over the past few decades, few studies have shown that any treatment can decrease mortality for this deadly syndrome. In the 4 May 2000 issue of New England Journal of Medicine, the results of an NIH-sponsored trial were presented; they demonstrated that the use of a ventilatory strategy that minimizes ventilator-induced lung injury leads to a 22% decrease in mortality. The implications of this study with respect to clinical practice, further ARDS studies and clinical research in the critical care setting are discussed.     

Mechanical and gas-distribution behavior of a collateral ventilation model

We extended the theoretical analysis of Otis et al. (J. Appl. Physiol. 8: 427-443, 1956) to study the effects of collateral ventilation on lung mechanics and gas distribution. Equations were developed to express the effective compliance, the effective resistance, and the distribution of airflow and tidal volume in a two-compartment model incorporating a collateral communication. The analysis of the model showed that, in general, collateral ventilation tends to attenuate the degree of frequency dependence of compliance and resistance, the magnitude of this effect being dependent on the mechanical properties of the model, including collateral resistance. The influence of collateral ventilation is important when the model simulates the mechanical characteristics of the emphysematous lung (marked time-constant inequality with regionally high airway resistance, and relatively low collateral resistance). Under these conditions, a large fraction of the tidal volume of the high airway resistance lung compartment is contributed by the collateral communication. The effects of collateral ventilation on the mechanical behavior of the model are negligible when collateral resistance largely exceeds airway resistance (simulating experimental findings in normal lungs). The present theoretical data suggest that the use of equations based on a model incorporating collateral ventilation is justified, at least in predicting the mechanical and gas-distribution behavior of the lung in emphysema.