This reminds me of an incident with my missus in the Red Sea on the Thistlegorm.
When we dived her I said at the beginning that I was emptying the tank to get the most time on the wreck. I led her round and arrived at the shot spot on with 20 bar and started up.By the time I was at 4m and had done a safety stop I was at 10 bar. She on the other hand had stopped at 8m and was looking down at the other divers on the wreck. She was quite happy hanging there while I waited for her to ascend so I could surface.
Eventually I completely ran out of air so I decided that I would be better off going down to her than popping up and leaving her. So I swam down, tapped her on the shoulder and signalled OOA. She gave me a blank look. I signalled again, another blank look! At this point I reched over and grabbed her octo and once it was in my mouth comprehension dawned in her eyes!    We both went up and onto the boat, the guide was unimpressed at 0bar and 10bar  
On my part i should have let her know I was getting so low and she needed to practise signals