Three days post op front amputation

My lovely girl Lucy is now three days post op from her front leg amputation.  She is a bit more alert with her Fentanyl patch to be removed tomorrow.  He appetite is poor. Although shaky in the legs, when she does get up, she is managing hoping around fine.  She tires very easily.  My main concern is her rate of breathing.  It seems as though her resting breath rate is 45-50 breaths per minute.  Her confirmed diagnosis is not yet in but is probably osetosarcoma as the bone on her xray was eaten away.  My worry is that it is already in her lungs making her breathing compromised.  How do dogs present when the cancer has invaded her lungs?  She really only presented a few weeks ago with a limp.Lucy with added toys