Its little chest was laboring but it wasn't breathing!

He was having trouble breathing; his chest labored.

My chest labored against the ground.

Lobia's rheumy eyes danced with self-deprecating mirth, even as her chest labored to maintain the rhythm of breathing.

Her pulses raced, chest labored.

Gillian's chest labored with the rise and fall of her lungs.

His chest was laboring as he carried the tarp-wrapped body up the hill.

His chest labored for air.

His chest ached from the water he'd swallowed, making his breathing slow and labored.

His lips were slightly blue, and his chest labored as he fought to recover his breath.