 The pressures required to prevent apnea/hypopnea varied between 5 and 11 cm H2O.  The optimal pressure was 11 cm H2O, which prevented all of the apneas/hypopneas. 
The pressures required to prevent apnea / hypopnea varied between 5 and 11 cm H2O. The optimal pressure was 11 cm H2O , which prevented all of the apneas / hypopneas .