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Mechanical ventilation delivers pressure, flow, and/or volume to the patient with the aim of improving ventilation and reducing inspiratory work. Depending on various circumstances, such as the level of sedation, paralysis, or if the ventilator support is patient triggered or not, the goals of mechanical ventilation (improved ventilation and reduced work of breathing) may be achieved in different ways.

Non-invasive ventilation (NIV) for the treatment of acute and chronic respiratory failure has achieved an increasingly important role over the last decade. Until the mid-eighties, mechanical ventilation in intensive care unit (ICU) patients with acute respiratory failure was generally delivered invasively via an endotracheal or tracheostomy tube. With growing knowledge of pathophysiology, it became apparent that there are also risks and complications, not only related to mechanical ventilation itself (volu- and barotrauma), but especially if mechanical ventilation is delivered invasively, such as the increased rate of nosocomial pneumonias []. Hoarseness, sore throat or vocal cord dysfunction becoming apparent after extubation may also result in long term complications [], Therefore, the application of NIV techniques seems logical.

Endotracheal intubation and mechanical ventilation are required for the majority of critically ill patients in tertiary care intensive care units (ICUs) []. During mechanical ventilation, patients often have imbalances in regional lung ventilation due to heterogeneity of lung mechanics. The current methods generally available for assessing lung function in mechanically ventilated patients include arterial blood gas analysis and graphic waveforms from ventilators (flow, pressure and volume over time as well as pressure-volume, pressure-flow and flow-volume loops). At best, these methods reflect only overall lung function, while failing to give information on disparate regional functionality Unlike data collected from the ventilator or the blood, lung imaging allows for regional assessment of anatomy or function. Methods which pro-vide the capability of quantifying these regional differences in mechanically ventilated patients are of great interest.

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are clinical entities with a broad spectrum of increasing severity of lung injury consisting of widespread damage to cells and structures of the alveolar capillary membrane that occurs within hours to days following a predisposing insult []. ALI/ARDS is a major cause of acute respiratory failure with high morbidity and mortality in critically ill patients []. There is reason to believe that the incidence of ARDS may even increase significantly in the future because of the rising frequency of predisposing conditions such as sepsis []. Although mortality in patients with ALI/ARDS may have declined over the last 15 years, it remains high (30–40%) [, ]. Endotoxin-induced injury is a very useful experimental and model closely resembling ALI and ARDS in humans. Upon stimulation with lipopolysaccharide (LPS), enhanced expression of adhesion molecules, cytokines, and chemokines seems to play a crucial role in the inflammatory orchestration [–].

Clinicians and researchers are becoming increasingly conscious of the potentially harmful effects of mechanical ventilation, and more attention is being focused on methods of ventilation that may reduce these complications. Indeed the paradigm for mechanical ventilation in patients with acute lung injury (ALI) and acute respi-ratory distress syndrome (ARDS) has evolved in the last 10 years from a goal of nor-malizing blood gases to one of avoiding ventilator-induced lung injury (VILI) while maintaining adequate gas exchange. Lung protection during mechanical ventilation begins with limitation of tidal volume on conventional ventilation, but the optimal method remains to be determined []. One potential modality that may be useful in the avoidance of VILI is high-frequency oscillation (HFO). In this chapter, we will introduce HFO, provide a brief discussion of ARDS and VILI, and focus on the preclinical and clinical data available to date supporting the use of HFO as a primary modality to avoid VILI in adults.

Cardiac surgery is associated with a pulmonary and systemic inflammatory response. The pulmonary effects of this inflammatory reaction are often modest: decreased lung compliance, pulmonary edema, increased intrapulmonary shunt fraction and decreased functional residual capacity (FRC) [], Less than 2% of patients undergoing cardiac surgery develop full blown respiratory failure, the acute respiratory distress syndrome (ARDS) []. For example, after cardiac surgery, FRC is reduced up to 40–50% during the first 24 hours after extubation []. However, after general anesthesia, FRC is only decreased by 20–30% []. This exaggerated disturbance of pulmonary function is not yet fully understood. It has been suggested that this impaired pulmonary function is the result of pulmonary inflammation, triggered by cardiopulmonary bypass (CPB), ischemia-reperfusion injury, the surgical procedure itself, or by mechanical ventilation.

The static pressure volume (P/V) curve has been regarded as the gold standard tool for assessment of the mechanical properties of the lung. On this curve, a lower inflection point (LIP) can be detected in some patients and in most patients an upper inflection point (UIP) can be seen. The most common interpretation of the LIP and the UIP is that LIP represents the point where alveoli collapse at the end of expiration and reopen at the start of inspiration and that the UIP represents the pressure above which alveoli become overdistended. It has been proposed that in order to avoid cyclic closing and opening and overdistension of alveoli, ventilation should be performed with pressures between the LIP and UIP, where the compliance of the lungs is highest.

The world is aging fast: in 2000 there were 600 million people aged 60 and over; there will be 1.2 billion by 2025 and 2 billion by 2050 []. Health care for this aging population has become a vital challenge not only in industrialized societies but also in many developing countries. Today, about two thirds of all older people are living in the developing world; by 2025, it will be 75 %. For instance, by the year 2036, the number of elderly Chinese people (aged 65 and above) is anticipated to surge to over 300 million and represent up to 20% of the nation’s total population [, ]. An identical aging trend is also apparent in the developed world, where the very old (age 80+) are the fastest growing population group (Fig. la). Interestingly, women outlive men in virtually all societies; consequently in very old age the ratio of women to men is 2:1 []. By the year 2050, 1 in 12 Americans will be older than 80 years [], which will indeed impose a major burden on health care resources (Fig. 1b) [].

Arrhythmias are common in the intensive care unit (ICU) and represent a major source of morbidity and increased length of stay. Arrhythmias are most likely to occur in patients with structural heart disease. The inciting factor for an arrhythmia in a given patient may be a transient imbalance, often related to hypoxia, infection, cardiac ischemia, catecholamine excess (endogenous or exogenous), or an electrolyte abnormality. Management includes correction of these imbalances as well as medical therapy directed at the arrhythmia itself.

Sepsis is a clinical syndrome that results from the systemic response of the body to infection []. It is a serious clinical problem, accounting for substantial morbidity and mortality. The majority of these patients die of refractory hypotension and of cardiovascular collapse [].