Introduction

Traditionally, outcomes of mechanical ventilation for acute respiratory failure reported by investigators have been physiologic changes, mortality, duration of mechanical ventilation, and length of stay in both intensive care unit (ICU) and hospital. Various definitions for a mortality outcome have been used, often either an arbitrary period from acute disease onset such as 28 day mortality, or mortality at hospital discharge. Occasionally costs of the hospitalization have been included.

In recent years reports of longer term outcomes in patients with acute respiratory failure (and especially in acute lung injury [ALI]/acute respiratory distress syndrome [ARDS]) have been published. These outcomes have included long-term survival, pulmonary function, and - more recently - quality of life and conditions or complications of acute respiratory failure that could affect quality of life. These complications or conditions include neurocognitive and neuropsychological abnormalities and neuromuscular complaints and impairments.

The subject of this chapter is long-term outcomes after mechanical ventilation. For the most part, we are unable to differentiate which outcomes in survivors of acute respiratory failure are related to the use of mechanical ventilation and which are due either to the underlying condition for which mechanical ventilation was being performed or a variety of other factors including co-morbidity and the effects of other therapies. We will approach this issue by first describing long-term outcomes associated with mechanical ventilation for acute respiratory failure in a general way. We will describe survival, emphasizing when available data on long term follow-up of these patients, and also quality of life and complications occurring in survivors. Mechanical ventilation may allowthe occurrence or development of complications - but not be directly responsible for them. After a description of outcomes we will briefly discuss possible etiologic factors whenever data exist to allow this, including whether mechanical ventilation could be implicated. Most of the data will be reported separately for the differing underlying conditions or types of acute respiratoryfailure, mainly since the original papers most frequently report outcomes for particular disease cohorts, but also because the underlying condition is likely such an important determinant of outcome.

Why is it important that we know the long-term outcomes after mechanical ventilation for acute respiratory failure? The answers vary depending on the category of the outcomes being considered. Survival is important in order to know prognosis, which could play a role in decision making for both the patient and his or her surrogates and the caregivers during the ICU admission. Knowledge of long-term survival may also be important in resource development and utilization planning. Objectively measured physiologic outcomes such as pulmonary function can help connect events and therapy during the acute illness with other more patient-centered outcomes. These measurements may provide information about mechanisms and also may have predictive value. Patient-centered outcomes such as quality of life and symptoms are what patients care about. Also, by understanding the prevalence and severity of these outcomes, we can begin to link them with possible etiologic factors during the critical illness that are potentially modifiable. In this way we can begin to develop strategies for patient management both during the critical illness and in follow-up that maybe able to prevent or minimize these adverse long-term outcomes.

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