Though acapella and flutter devices facilitate the removal of secretion they are two different devices with similar performance characterisitics but with very few differences. one of the most significant differences between them is
a. the acapella's performance is not gravity dependent while the flutter is which may be easier to use for some patients
b. the flutter's performance is not gravity dependent while acapella is which may be easier to use for some patients
c. the acapella is battery operated while the flutter is not
d. the flutter is battery operated while the acapella is not