[1] MCGILL UNIV, FAC MED, DEPT PEDIAT, MONTREAL, PQ, CANADA
[2] INSERM, U14, F-54511 VANDOEUVRE LES NANCY, FRANCE
[3] UNIV CATHOLIQUE LOUVAIN, CLIN UNIV ST LUC, B-1200 BRUSSELS, BELGIUM
[4] INST CHILD HLTH, INTENS CARE & RESP MED UNIT, LONDON, ENGLAND