"The hospital smell combs my nostrils as they go bobbing along green and yellow corridors."
The speaker begins with the recognisingly strong, unique hospital smell.
The personification 'combs my nostrils' suggests the smell is active and almost tactile. The image is synecdochic, as the word 'nostrils' in representing himself there.
He develops the image by stating that 'they go bobbing along', as though his nostrils are dissociated from himself, again emphasising the smell, though the word 'bobbing' is almost whimsical.
The adjectives 'green and yellow' are symbolic, not only of illness, but also of his own upset emotions.