I am sorry to hear you are worried about Duke, and this gurgling breathing worries me, too. My name is Rebecca. I am a veterinarian and will do my best to help. How long has he been having labored and gurgling breathing? If you look at his gums are they pink, or pale, or blue?
Can he breathe with his mouth closed, or does he have to open mouth pant to breathe?
The gurgling is a worry that he may have fluid in his lungs, and that is an emergency. If his gums are white, or blue, this is probably an emergency.
If his gums are pink, that is a better indication he is getting enough oxygen. Can you take his temperature with a thermometer?
If I could, I want to listen to him with a stethoscope, feel his pulses, palpate his lymph nodes, and if it sounds like there is fluid in his lungs, I would take a chest Xray.
There is a condition called Laryngeal paralysis that can make breathing noisy and difficult. It tends to come and go but usually gets gradually worse. There are medications that help, but some dogs with "lar par" need surgery.
Let me know about his gums, his temperature, and if there is an emergency clinic near you.