.
Rebreathing carbon dioxide (for short, safe periods) has many, many benefits for Zoe. It forces her to take bigger breaths during the time her air is restricted and therefore, increases her lung capacity. The carbon dioxide also dilates her blood vessels which after the mask is removed, allows her to get more oxygen to her brain.
The intended outcomes for doing this are - greater endurance, more robust immunity, stronger voice, better chewing/swallowing, increased mental clarity/capacity. The list goes on and on.
When Zoe was younger, her laugh was silent. We would tickle her or do something funny and she'd give this wide open mouth smile and her eyes would shut tight with joy. She was full of laughter but no sound would erupt. You know when you laugh so hard you can't get your breath and your stomach hurts and only tears come out? That's what it was like for her.
Now she laughs out loud all the time and shrieks with delight. And if laughter is the best medicine, certainly hearing a child's laugh is healing at its best. Hope you enjoy hearing a little of her laughter - it's not her loudest laugh but it's the most recent on video (and ignore the annoying Mom voice on film). Hahaha - keep laughing!