Agree on a "safe word" either of you can use to call a time-out when you are feeling overwhelmed in an argument. Often couples choose a word that is random or even funny, like "elephant." When you use your safe word, agree on a time when you will resume talking.
Using a safe word is a great way to prevent defensiveness, blow-ups and also stony silences. You are creating a safe space to calm down and reconnect more productively.