Techniques in mechanical ventilation: principles and practice.

The principles and practice ofmanaging mechanical ventilation are often daunting to chest physicians. It is easy to see why this should be. Firstly, the physician's experience of ventilators is usually in intensive care units where the responsibility rests largely, but often to a loosely defined degree, with anaesthetists. The complex and rapidly changing medical problems of patients require frequent adjustments to the ventilator settings. In addition, there is a wide range of ventilators and the details of their performance characteristics are often unavailable to the user. The classification of ventilators is becoming more complex and more unsatisfactory as their versatility increases, and the nomenclature of the various modes ofventilation is inconsistent and confusing.' Many of these have been inadequately assessed and their clinical indications are uncertain. Lastly, there is an increasing range of interfaces (such as nasal and face masks and new designs of tracheostomy tubes) between the ventilator and the patient to choose from and with which few doctors are familiar.2 Patients with both extrapulmonary restrictive disorders and chronic airflow obstruction are, however, being treated with ventilators in increasing numbers on medical wards and in their homes, as well as in intensive care units. Decisions about how and when to initiate ventilation, how to wean the patient from the ventilator, and how to provide long term ventilatory support are having to be faced increasingly frequently. This review addresses the principles and some of the practical issues of this type of treatment.