Where's my oxygen?

Michael started on his portable O2 tank around noon and they told us it would last 8 hours. We are still waiting for the O2 delivery at 4:42 PM and the tank is almost empty. It sure didn't last 8 hours, only about half that time. I called the O2 dispatch again for the third time and told them that the tank registers in the red zone. I got the same response as Michael was told, they would contact the driver. Meanwhile Michael turned down his tank to .5 liters instead of the 1 liter he is supposed to be on. We can only hope they come pretty soon.