Cause for fluctuating B. P. Fluctuating.

My father is admitted in hospitalfor last 3 days.He is under cancer medication. He was diagnosed with lung Cancer a month and half ago.3 days back he suddenly felt very restless and uncomfortableand was feeling difficulty in breathing.His Spo2 level suddenly dropped to 66.So he was brought to hospital.His B.P. was fluctuating drastically.It was from 38/80 to 120/190.Dr. took an X-ray of chest and he found that there is no increase in infectionwhen he compared it with an X-ray took amonth and half back .He kept him on ventilator. Now Oxygen level is improved but B.P. is still fluctuating. Today afternoon they removed the ventilator but provided him with oxygen mask.There is swelling in his face and throat.I wanted to know the reason for fluctuating B.P. He is also taking heart medication as two stunts were put in his  two arteries two years back. He is also diabetic. He takes medicine as well as insulin once a day.In this condition we can't shift him to any super speciality hospital.