34 - Principles of Mechanical Ventilation

Mechanical ventilation is central to critical care and came into routine practice after the polio outbreaks in the mid-20th century. A contemporary mechanical ventilator is a device made to deliver breaths using positive pressure (pressure above atmospheric level). The technology has become increasingly sophisticated in efforts to improve patient comfort and synchrony, as well to enhance ease of use. It is used for many indications, mainly for respiratory failure either from pulmonary or extrapulmonary sources, as well as to provide anesthesia. The most frequently used invasive modes in pediatric populations are synchronized pressure control ventilation with/without volume limitation and pressure support ventilation. While in special circumstances, such as congenital diaphragmatic hernia and severe hypoxemic respiratory failure, high frequency oscillatory ventilation may be a first choice, in most cases noninvasive ventilation and humidified high flow are increasingly used. However, positive pressure breathing can cause direct injury to lungs and has deleterious effects on hemodynamics. The overall goal therefore is to optimize patient needs and minimize risk of harm, while tailoring the ventilation strategy to the patient need. Hence, selection of right mode and strategy, optimization of respiratory mechanics and gas exchange, and provision of expert care are central to management of mechanical ventilation in critically ill children. These are addressed in this chapter.