BOTT, J. A randomised controlled study of nasal intermittent positive pressure ventilation in acute exacerbations of chronic obstructive airways disease. Lancet. 1993, 341, 1555-1557
KRAMER, N. Randomized, prospective trial of noninvasive positive pressure ventilation in acute respiratory failure. Am J Respir Crit Care Med. 1995, 151, 1799-1806