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Does noninvasive positive pressure ventilation have a role in managing hypercapnic respiratory failure due to an acute exacerbation of COPD?

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Yes. In selected patients with hypercapnic respiratory failure due to an acute exacerbation of chronic obstructive pulmonary disease (COPD), noninvasive positive pressure ventilation (NIPPV) is an effective adjunct to usual medical therapy. In controlled trials, it reduced the need for endotracheal intubation, the length of hospital stay, and the risk of death.

Acute COPD exacerbations are responsible for more than 500,000 hospitalizations yearly in the United States, and 6% to 34% of patients die.1

Many patients need invasive ventilatory assistance via an endotracheal tube, but such therapy puts the patient at risk of ventilator-associated pneumonia, pneumothorax, and tracheal stenosis.

WHAT IS NONINVASIVE POSITIVE PRESSURE VENTILATION?

Figure 1.
With NIPPV, the patient wears a tightly fitting nasal or full facial mask, avoiding the need for an endotracheal tube, laryngeal mask, or tracheostomy (Figure 1).2 The mask can be connected to a standard mechanical ventilator or, more commonly, to a continuous positive airway pressure or bi-level airway pressure unit. NIPPV has been used with variable success in a variety of conditions, including COPD exacerbations,3–6 acute cardiogenic pulmonary edema,7 hypoxemic respiratory failure,8 and ventilator weaning.9

WHY IS IT BENEFICIAL?

Several mechanisms may explain why noninvasive positive pressure ventilation is beneficial in acute exacerbations of COPD.

Patients with decompensated respiratory failure lack sufficient alveolar ventilation, owing to abnormal respiratory mechanics and inspiratory muscle fatigue.10 For these patients, breathing faster does not fully compensate. Noninvasive positive pressure ventilation partially counteracts these factors by providing a larger tidal volume with the same inspiratory effort.10,11

Additionally, this treatment can decrease the work of breathing by partially overcoming auto-PEEP (positive end-expiratory pressure) in certain situations.2 Auto-PEEP is pressure greater than the atmospheric pressure remaining in the alveoli at the end of exhalation.12 This condition is related to limited expiratory flow and is common in those with severe COPD. Noninvasive positive pressure ventilation decreases the pressure difference between the atmosphere and the alveoli, thereby reducing the inspiratory force needed for initiation of inspiratory effort, which may reduce the work of breathing. However, caution should be used when using this therapy in tachypneic patients, in whom NIPPV may not fully overcome the auto-PEEP.

WHAT STUDIES SHOWED

Several randomized trials have shown NIPPV to be beneficial in acute hypercapnic COPD exacerbations. A recent meta-analysis of eight studies13 showed that, compared with usual care alone, this therapy was associated with:

  • A lower mortality rate (relative risk 0.41; 95% confidence interval [CI] 0.26–0.64)
  • Less need for endotracheal intubation (relative risk 0.42; 95% CI 0.31–0.59)
  • A lower rate of treatment failure (relative risk 0.51; 95% CI 0.38–0.67)
  • Greater improvements in the 1-hour post-treatment pH and PaCO2 levels
  • A lower respiratory rate
  • A shorter length of stay in the hospital.

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