What could cause occasional shallow breathing in a person suffering from pheochromocytoma?

Hello doctor,

I have recently lost weight, my weight is around 180 pounds and I am 160 centimeters. I have a suspected pheochromocytoma on the left adrenal gland, I had occasional shallow breathing after taking Pholcodine (Broncalene), it worsened in heat. I went to the emergency room and despite telling the doctor my problem and having a 100 percent oxygen level, he suggested me a Ventolin (Albuterol) nebulizer, since then, it has been four days my breathing is tight and I am short of breaths as though I have to make myself breathe, if I sleep I would wake up sweating and feel sick a lot of the day. I went back to the hospital and they said it is stress, it is not as it is constantly there and this is the fifth day. My blood pressure can range from 120/70 mm/Hg to 190/113 mm/Hg, heartbeat often over 100 beats per minute. I Am on Candesartan (Atacand) 12 milligrams. Can anything be done to get my lungs so they start working again? It is as if they are left with half a strength and I appear to hold my breath.

I have a past medical history that includes vertigo due to heatstroke six months ago. I had pain in the left side of the stomach just above the ribcage and also suffered from diarrhea. I am on a light diet since then. I could not put on weight after that, I had a head CT (computed tomography) and I am awaiting the MRI (magnetic resonance imaging) results. My breathing is fine now and I had pholcodine for the cough. I had shallow breaths and they worsened with time but nobody believe me as the oxygen level was at 100 percent. My fbc (full blood count) is normal too.

I hope to hear from you soon.

Thank you.