Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your girl Chanel seems off post-whelping, with increased panting and gagging.
You say she just had them, but has it been hours or days since delivery?
Is she eating and drinking normally?
Are the puppies nursing well and do they seem satisfied between feedings (not crying, sleeping soundly)?
Did you have an ultrasound or radiographs done before she delivered so you know how many puppies she had to deliver?
Is this her first litter?
Any foul smelling vaginal discharge?
Is she running a fever? (rectal temperature greater than 103F)
Do her mammary glands look normal (no red, hard, tender areas)?
It may be that she is a nervous first time bitch, and perhaps there is too much activity going on around her so she feels unsettled. Increased anxiety will cause her to pant.
But it may also be that she didn't deliver all of her pups for some reason (uterine inertia, very large puppy, dead puppy) and that is something that should be looked into. If you don't know how many puppies she was carrying that is a concern.
Pregnancy and producing milk for a litter of puppies is a lot of work for any dog and can be very taxing on their bodies. Some dogs develop hypocalcemia (low blood calcium) due to the demands of producing milk for a litter of puppies. These dogs will have panting, restlessness, drooling, vomiting, tremors, weakness, may have a change in personality due to the effects of low blood calcium on the brain as well as stiffness in their gait. It can progress to seizures and if not treated, death.
If this is what is going on with her this is a true medical emergency and she needs to be seen by a veterinarian immediately. They will check her blood calcium levels and start intravenous calcium immediately. If this is her diagnosis the puppies will need to be bottle fed and weaned now, she cannot feed them any more or she will become hypocalcemic again.
Other possibilities are an infection, either mastitis or a post-whelping uterine infection.
I recommend that you check her mammary chain and look for any signs of redness, firm swelling or pain. If those are present then mastitis is possible.
Does she have any yellow, or foul smelling vaginal discharge? If so a post-whelping uterine infection is possible.
If she were my girl I'd take her temperature, evaluate her mammary chain and look for any abnormal vaginal discharge.
If her temperature is normal, her mammary chain looks good, you know she only had 8 puppies to deliver, she is eating and drinking normally, and her puppies seem to be feeding well and satisfied then she might just need to have a quieter nesting area and some time.
But the safest thing would be to have her examined and get an abdominal radiograph to make sure there aren't any remaining pups or signs of a brewing post-whelping infection or low blood calcium.
Please let me know if you have any further questions.