dear Hessa,

There is a lot of information on the internet. By googling chest fysiotherapy babies reflux I came up with:
http://www.ncbi.nlm.nih.gov/pmc/arti...v089p00435.pdf
Chest physiotherapy, gastro-oesophageal reflux, and arousal in infants with cystic fibrosis -- Button et al. 89 (5): 435 -- Archives of Disease in Childhood
http://erj.ersjournals.com/content/12/4/954.full.pdf
Gastroesophageal Reflux (GOR) in Infants: A Time for a Change?
Chest Physiotherapy

I am not specialized in this field. I do think this should help. From what I read, the head down position is not favourable, preference for lying the children flat in the cases of reflux.
Good luck with your search. Try Pubmed and the other scholarly sites.

Esther