Noninvasive ventilation airway clearance

Some studies suggest that liberation from mechanical ventilation is a requirement for decannulation (6), but this precludes the provision of noninvasive ventilation (NIV) as part of decannulation and may be impossible for some patients who could otherwise be dec-annulated. Other reports recognize that decannulation may proceed to NIV 24 hours a day without the requirement of an artificial airway (7) provided bulbar function is adequate and airway clearance is achieved (8). 

In this chapter we will discuss recommendations from the hterature regarding dec-aruiulation as well as our personal clinical experience. We will comment on the pathophysiology of ventilator dependence, the determination of candidates for weaning from ventilation and tracheostomy, and a stepwise approach to decannulation. Lastly, we will discuss the choices of noninvasive ventilatory supports and techniques that clinicians may utilize, such as lung volume recruitment (LVR), assisted coughing and mechanical airway clearance. 

There is an important distinction between dependence on an artificial airway and mechanical ventilation, which can be provided noninvasively (9). The requirement for an artificial airway may reflect bulbar impairment as, in those with adequate bulbar function, noninvasive ventilation will sustain adequate ventilation even with veiy limited respiratory muscle function. Therefore, tracheostomized patients with preserved bulbar control can undergo decannulation. Airway secretions are important determinants of dependence on mechanical ventilation through an artificial airway, and aspiration pneumonia may result from an impaired level of consciousness, poor bulbar function, or inability to cough effectively. Such issues must be addressed by airway clearance techniques, prior to decannulation. 

In patients with COPD there is a persistent and permanent dyspnea and airway obstruction, with incomplete reversibility with therapy. Normally, in these patients, the mucociliary transport is not so impaired, until an acute exacerbation occurs. During an acute exacerbation of COPD, hypersecretion is usually present and may be induced by bacterial infections. Secretion encumbrance and ineffectiveness of airway clearance is associated with failure of noninvasive ventilation (NIV), whereas endotraqueal intubation and mechanical ventilation is necessary in acute exacerbations of COPD. The duration of mechanical ventilation was correlated with hospital mortality (22). 

To appreciate the pathophysiology of respiratory failure, and to appropriately tailor therapy to the needs of the individual patient, the different components of the illness must be understood and assessed. The degree to which oxygenation, ventilation, airway protection, and secretion clearance are impaired, and what measures are required to manage each of them, are important determinants of where and by whom a particular patient may be cared for. They determine, for example, whether invasive or noninvasive ventilation will be more appropriate for that patient, how likely it is that the patient can be managed successfully at home, and how much external support in the form of equipment and personnel will be required. 

The effective elimination of airway mucus and other debris is one of the most important factor that permits successful use of chronic and acute ventilation support (noninvasive and invasive) for patients with either ventilatory or oxygenation impairment. In ventilatory dependent patients, the goals of intervention are to maintain lung compliance and normal alveolar ventilation at all times and to maximize cough flows for adequate bronchopulmonary secretion clearance (6). 

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