"he sido lo suficiente rapida."

"he sido lo suficiente rapida."
 

I read the following sentence (the red part is the part I don't understand):

Casi siento deseos de reir cuando advierto que he sido lo suficientemente rapida.

I know "he sido" = "I have been," and I believe "suficientemente rapida" = sufficiently fast (?), but I can't figure out why "lo" would follow "he sido."

Any help is appreciated!

it is the neutral article, mostly equivalent to it.

Is there anymore context?

You can say: he sido suficientemente rápida en/para darme cuenta que no debía reírme... etc.

Can you post the sentences that preceed and follow the quoted sentence?

Casi siento deseos de reir cuando advierto que he sido lo suficientemente rapida.
I almost want to laugh when I notice I was fast enough (to do it)
Where it depends on the context.
Example:
-¿has podido llegar a clase a tiempo?,
- Si, he sido lo suficientemente rápida (Iwas fast enough to arrive on time)

- ¿Has limpiado las pruebas antes de que llegase la policióa?
- Sí, he sido lo suficientemente rápida. (I was fast enough to clean all)

saludos :D

I agree with Sosia, we use the adverb "suficientemente" to modify the adjective "rápida". The construction of these sentences is with "lo" (it gives noun function to that construction).