The physiological sigh
A 2023 study compared breathing techniques for calming the body down. The one that stood out was the physiological sigh: two inhales through the nose (one big, one short top-up), then a long, slow exhale through the mouth, repeated for five minutes. A few of those before you speak can help you settle. Box breathing (in for four, hold four, out four, hold four) also works and is easier to do silently in a meeting.