Researchers recently did a study of patients who had a disorder called spondylothoracic dysplasia. One of the problems that people with this disorder have is a smaller torso and a rib cage that can compromise the breathing.
While many with this disorder die as infants because of respiratory problems, the researchers found that there were patients who survived well into adulthood. These older patients had, except for one patient, adapted well to their condition and were living comfortably. One theory the researchers suggested was that the patients' smaller size demanded less oxygen and their body simply adapted to what oxygen was available.