الفهرس 
Monitor gas exchangeOnly 14 pages are availabe for public view
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Abstract
The main goal of mechanical ventilation is to help restore gas exchange and reduce the work of breathing (WOB) by assisting respiratory muscle activity.
Monitoring of oxygenation and ventilation is important but before attempting to adjust the ventilator to correct the PaO2 and/or PaCO2 to normal levels, the underlying alteration in the respiratory physiology and mechanics needs to be understood. It is also essential to weigh the risk and benefits specifically in regard to mechanical stress on the lungs before attempting to correct abnormal blood gas values. Monitoring in the ICU should aim to keep the patients within a safety zone and does not imply the need to act on all abnormal values. First do no harm.
During mechanical ventilation the clinician must become familiar with all these properties of the lung and chest wall that determine the ease of chest expansion. Certain properties can be assessed only under passive conditions (eg, compliance), others require active breathing effort (eg, maximal inspiratory pressure), while others can be determined with or without active breathing effort (eg, lung‘s impedance properties). Finally, to separate static from dynamic variables, points of zero flow within the tidal cycle must be determined.For many years frequent measurement of arterial blood gas tensions has been the only physiological evaluation in these patients and the chief guide to setting the mode and pattern of ventilatory assistance. In the 1980s two factors contributed substantially to a change in this conventional attitude. Firstly, a growing amount of research indicated that respiratory muscle malfunction, overload, or ―fatigue‖ had a pivotal role in the pathophysiology of acute respiratory failure. Secondly, pressure support ventilation (PSV) a mode of mechanical ventilation whose primary goal is to unload the patient‘s respiratory muscles became widely popular and was increasingly used in the intensive care unit (ICU).
Patient-ventilator asynchrony is very common. Its prevalence depends on numerous factors, including timing and duration of observation, technique used for detection, patient population, type of asynchrony, ventilation mode and settings (eg, trigger, flow, and cycle criteria), and confounding factors (eg, state of wakefulness, sedation).
Patient-ventilator asynchrony is associated with adverse effects, including higher/wasted work of breathing, patient discomfort, increased need for sedation, confusion during the weaning process, prolonged mechanical ventilation, longer stay, and possibly higher mortality.On current modes of ventilation there are a number of features that can monitor and enhance synchrony. These include adjustments on the trigger variable, the use of pressure versus fixed flow-targeted breaths, and a number of manipulations of the cycle variable. Clinicians need to know how to use these modalities and monitor them properly, especially understanding airway pressure and flow graphics.
Future strategies are emerging that have theoretical appeal, but they await good clinical outcome studies before they become common in place. Foremost among these are electrical impedance tomography (EIT), acoustic monitoring, and pulmonary ultrasound.
Finally to improve accuracy, new monitoring devices for determining respiratory drive and patient ventilator synchrony are needed, determination of respiratory drive using diaphragm