Is there a tool or device for this???

Sometimes I don't feel right, like maybe it's my O2, or don't know what it is. Of course I have an oxi meter and read my O2 saturation level to make sure it's ok. I was just curious if a device exists that can measure the liters per minute you are receiving from the end of your cannula. They say that it's suppose to be the same weather your using a 4ft tube or 50 feet of tubing. My cats like to play with mine on the floor sometimes and thought maybe there might be one or even more little pin holes in the tubing that the O2 could be leaking from thus reducing the output delivered into my cannula. I suppose I could put water in the bathtub and look for bubbles to see if it's leaking but that wouldn't give me the output in liters or milli liters. Thanks people.