A patient interface device is includes a cushion and a frame assembly coupled to the cushion, the frame assembly including a main frame member and a stiffening structure coupled to the main frame member, the stiffening structure having a main arm, a first Y-portion coupled to a first end of the main arm having first and second front branches extending at upward and downward angles, respectively, from the first end of the main arm, and a second Y-portion coupled to a second end of the main arm having first and second rear branches extending at upward and downward angles, respectively, from the second end of the main arm.