I believe that Atwood employs a metaphor to demonstrate that Offred cannot see the world and also has metaphorically restricted freedom to explore. Here, Offred is referring to how the white "wings" of her headdress prevent her from seeing the world around her easily, which indicates the oppressive nature of this regime and society, as even the handmaids' physical reality is restricted from them, and they are restricted from being seen by others. This creates the sense that they are being "protected", when in reality they are simply being controlled. As readers, we see Gilead in ‘gasps’ too, in Offred’s view - just like her, we do not see the full view. This also affects her reliability as a narrator.
Another possible technique is an allusion, which, with respect to this text, is a subtle reference to an event and/or person that is intended to be noticed by readers. Essentially, this statement reveals the acceptance of fate for women to lead repressed lives, alluding to the fact that Offred is able to identify grey areas in the regime where she once again feels like herself in the past. This means that it is almost as if she is gasping for air from a society that suffocates her.
I hope this helps!