Read this. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3871630/
Its called pursed lip breathing and it does not maintain enough pressure to work like mechanical peep.

skywater wrote:Read this. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3871630/
Its called pursed lip breathing and it does not maintain enough pressure to work like mechanical peep.

Interesting results, but then why do human beings naturally PLB when under respiratory stress? I did PLB for decades before I even knew it had a name. I think the conclusion is that effects of PLB have yet to be determined.

I'm (very) late to the discussion as I just recently joined SP.
Pursed-lip breathing (PLB, Pressure Breathing, positive expiratory pressure) can improve oxygenation in a few ways. Some of these have been discussed already:

1.) It can improve ventilation-perfusion matching (i.e. the amount of oxygen arriving in the alveoli is ideal compared to the amount of blood flow in the capillaries)
2.) It can recruit additional alveoli that may have collapsed (microatelectasis) contributing to increased lung volumes - this is thought to happen in healthy individuals as well
3.) The additional pressure can drive any fluid that has leaked into the alveoli back into the capillaries, improving diffusion (subclinical edema)
4.) The additional pressure increases the pressure gradient for oxygen to diffuse into the pulmonary capillaries

In some cases, minute ventilation (the volume of air coming in and out of your lungs per minute) may be increased but this can vary. Ultimately, it is a combination of some or all of the above, that can lead to improved saturations.