Approaches to ventilation in intensive care

Abstract

Background: Mechanical ventilation is a common and often life-saving intervention in intensive care medicine. About 35% of all patients in intensive care are mechanically ventilated; about 15% of these patients develop a ventilation-associated pneumonia. The goal of ventilation therapy is to lessen the work of respiration and pulmonary gas exchange and thereby maintain or restore an adequate oxygen supply to the body's tissues. Mechanical ventilation can be carried out in many different modes; the avoidance of ventilation-induced lung damage through protective ventilation strategies is currently a major focus of clinical interest.

Method: This review is based on pertinent articles retrieved by a selective literature search.

Results: Compared to conventional lung-protecting modes of mechanical ventilation, the modern modes of ventilation presented here are further developments that optimize lung protection while improving pulmonary function and the synchrony of the patient with the ventilator. In high-frequency ventilation, tidal volumes of 1-2 mL/kgBW (body weight) are given, at a respiratory rate of up to 12 Hz. Assisted forms of spontaneous respiration are also in use, such as proportional assist ventilation (PAV), neurally adjusted ventilatory assist (NAVA), and variable pressure-support ventilation. Computer-guided closed-loop ventilation systems enable automated ventilation; according to a recent meta-analysis, they shorten weaning times by 32% .

Conclusion: The currently available scientific evidence with respect to clinically relevant endpoints is inadequate for all of these newer modes of ventilation. It appears, however, that they can lower both the invasiveness and the duration of mechanical ventilation, and thus improve the care of patients who need ventilation. Randomized trials with clinically relevant endpoints must be carried out before any final judgments can be made.

Figure

Local and systemic effects of mechanical ventilation – The use of high tidal volumes (volutrauma) and high airway pressures (barotrauma) and the cyclical collapse and reopening of alveolar territories (atelectrauma) can lead to the development of ventilation-induced lung damage. The pulmonary parenchyma sustains structural injury, and pro-inflammatory and pro-fibrotic mediators may be released and/or activated. This pulmonary inflammatory reaction is called biotrauma. Impaired alveolocapillary integrity can also result in a systemic inflammatory reaction, leading to multiple organ system failure. The physiological effects of ventilation-induced lung damage include an increase of the physiological dead space, reduced pulmonary compliance, and impaired pulmonary gas exchange.