"I do not want to see what happens next!" he said, breathing out hard.
This officer rushed to Paris, breathing out threats of slaughter against all royalists, and entered into close relations with Barras.
It is essentially breathing out against a closed glottis much in the way that you would strain to lift or pass stool.
For example, the Bilevel Positive Airway Pressure device, or BiPAP, is designed to apply more pressure when breathing in, while reducing pressure while breathing out.
By breathing out with a moderate force through the resistance of the device, a positive pressure is created in the airways that helps to keep them open.