Noninvasive Ventilation for Weaning and Post Extubation Failure

Introduction

In the event of acute respiratory failure (ARF), invasive mechanical ventilation (IMV) is a required practice to support gas exchanges and to unload respiratory muscles. Even if it is a life-saving procedure, it is not lacking from complications that actually make worse morbidity and mortality in intubated patients. Firstly, nosocomial infections, and in particular ventilator-associated pneumonia (VAP), are associated with a longer hospital stay and an increased risk of death.1 In fact, it is well known that an endotracheal tube can predispose to the development of pneumonia by impairing cough and mucociliary clearance because contaminated secretions can accumulate above the cuff and leak around the cuff or because bacterial binding to the surface of bronchial epithelium is increased. Invasive ventilatory support also increases the risk of feeding aspiration that can be shown in almost 50% of patients receiving prolonged ventilation.2 Gastrointestinal hemorrhages3 and generalized myopathy4 are other important possible complications. Heavy sedation or curarization during the first days of ventilation as well as sepsis and multiple organ failure (MOF) is an important risk factor for the development of both myopathy and neuropathy.5 The evidence of all these complications may, per se, explain why trying to reduce the duration of invasive ventilation, when it is not possible to avoid it, should be the most important goal in patients needing for prolonged invasive mechanical ventilation. Weaning is defined as the process of gradual removal of mechanical ventilation support toward spontaneous ventilation. In more than 70% of patients needing invasive mechanical ventilation, if accurately monitored about the readiness for a spontaneous breathing trial (SBT), weaning is possible in a few days (a median of 1 and 3 days in the intervention and control group, respectively).6 However, there is a group of ventilated patients requiring a gradual and longer withdrawal of respiratory support.7 There are no differences between the two most popular weaning methods, either the gradual progressive reduction of pressure support level or T-piece breathing. In fact, they result to be equally effective, and the operator confidence with one or the other technique should be the criteria of choice.8

Abstract

Invasive Mechanical Ventilation (IMV) is a life-saving procedure not lacking from complications that enhances morbidity and mortality for intubated patients; therefore, it is important to minimize the duration of IMV. When the weaning fails, it is associated with an increased risk of death and prolonged intensive care unit (ICU) stay. Many investigators examined the possibility to wean patients ventilated invasively by Noninvasive ventilation (NIV). Several studies, tested, in patients affected by chronic respiratory disorders (ie, chronic obstructive pulmonary disease), the use of NIV as a weaning strategy after a failure of a spontaneous breathing trial; as a result, NIV reduced mortality, minimized ventilator-associated pneumonia, and shortened length of hospital stay. Further studies will be needed to assess the real impact of NIV on other form of respiratory failure.\Another major clinical problem in ICU is the post extubation failure. In fact, more than 15% of patients need to be reintubated within the first 72 hours. After a successful weaning trial,their prognosis is poor with an hospital mortality that exceeds 30%–40%. Randomized controlled studies have demonstrated that when NIV is applied to treat an overt episode of post extubation respiratory failure, it can be indeed harmful perhaps due to the delay of reintubation. Conversely, promising results were obtained using NIV to prevent the development of a post extubation failure in patients considered at high risk, particularly in those affected by hypercapnia at the time of a successful T-piece trial.

Keywords

noninvasive ventilation, NIV, extubation, mechanical ventilation, extubation failure, reintubation, weaning.