Heres a scenario that demonstrate why I recommend attaching the leash to a harness instead of a collars. Collars should still be used, but for Identification and rabies tags instead.
An older yellow lab is rushed into the ICU being carried by frantic owners screaming “ HE CAN’T BREATHE!”
His tongue, a deep purple as He gasps for air, but in vain. His airway is completely closed.
With a swift injection of a sedative, and the skilled placement of a plastic tube passed his closed vocal folds, airflow is restored. His color returns within seconds, his heart rate normalizes, he can breathe again.
So, why did this happen!? How can this be prevented? It boils down to pressure on the neck. Controlling your dog by the neck means putting pressure on, and thus damaging, the recurrent laryngeal nerve. This nerve controls the airway which opens with each breath and closes with each swallow. Damaging this nerve means the airway can’t appropriately open. The good news is this damage is easily avoided by using a harness.