Ventilator management for hypoxemic respiratory failure attributable to H1N1 novel swine origin influenza virus

Ramsey.C.D. et al. Critical Care Medicine 2010: 38

This article looks into patients who develop severe respiratory failure from pandemic Novel H1N1 influenza needing mechanical ventilation.

Mechanical ventilation using lung-protective strategy and previous trials including the ARMA trial/ ARDS Network protocol, were reviewed here: with low tidal volumes (Vt 6ml/kg), plateau pressures (<30 - 35cm H2O), and optimal PEEP aiming SpO2 88-90%.  However, trials are lacking in H1N1 patient groups and the author comments that physician preference on ventilator settings vary.

In some patients with severe persistent hypoxaemia (SpO2 <88-90% with high PEEP and FIO2>0.8), alternative methods of ventilation are discussed, such as high-frequency oscillatory ventilation (HFOV), airway pressure release ventilation, and prone positioning, are reviewed.  At present, data of each of these methods are still very limited thus choice depends on perceived benefit v.s. risks.

The author discouraged the use of NIV, as it was not successful in the majority of severe hypoxia from H1N1 and majority of patients still required mechanical ventilation eventually.  There has been concerns that NIV can increase the risks of H1N1 transmission by generating more aerosol.  It "may be considered for patients with milder disease whose anticipated need for ventilatory support is short".  The author explained the reason for poor results of NIV in critically ill patients may be due to greater proportion of type 1 than type 2 respiratory failure, as NIV demonstrated more consistent benefit in avoiding intubation among patients with hypercapnic as opposed to hypoxaemic respiratory failure (e.g. CCF, COPD exacerbations, pulmonary edema, and immunocompromised).

http://journals.lww.com/ccmjournal/Fulltext/2010/04001/Ventilator_management_for_hypoxemic_respiratory.8.aspx