FIG. 37:  One of the effects of sleep apnea is development of very negative pressures in the chest.  For patients with OSA, the existence of negative pressures with apnea after apnea, night after night, may cause stretching in the thin-walled left atrium, and indeed, in the study summarized in the Figure,^[21] when newly diagnosed, otherwise healthy patients with OSA were compared to similarly obese, healthy subjects without OSA, the patients with OSA were found to have increased left atrial volumes compared to those who did not have OSA.