[1] Childrens Hosp Pittsburgh, Pulm Med, Pittsburgh, PA 15213 USA
[2] Univ La Laguna, Santa Cruz De Tenerife, Spain
[3] Univ Fed Bahia, Salvador, BA, Brazil
[4] UCSF, San Francisco, CA USA
[5] Univ Puerto Rico, San Juan, PR 00936 USA
[6] Univ Pittsburgh, Biostat, Pittsburgh, PA USA
[7] Hosp Nacl Ninos Dr Carlos Saenz Herrera, San Jose, Costa Rica
[8] Univ Connecticut, Farmington, CT USA
[9] Hosp Cima San Jose, San Jose, Costa Rica
[10] Channing Div Network Med, Boston, MA USA
[11] Univ Pittsburgh, Pittsburgh, PA USA