Try this, it’s what they taught my pa in hospital after his quad hear bypass, to get fluid off the lungs caused by inactivity and after effects of surgery.
Breath in, really really deeply. Close mouth, and hold it in for a couple of seconds. Then, rather than breath out, try and breath in a tiny bit more, just throught he nose, and then hold it for a moment before breathing out. – Try it a few times, and then repeat every hour or so. If you do it right, it probably will make you cough, and its getting air as deeply into lungs and out, getting things moving as well as anyting else you can do in a room/office.