Laryngeal trauma vs length of intubation

The frequency histograms of six patients' laryngographs were studied pre- and post-endotracheal intubation. The changes were correlated with the length of intubation. The post-operative hoarse voice was seen as an increase in the spread of the lower frequencies, and an increase in the fundamental frequency. The latter change was thought to be a subconscious compensation for the hoarseness. The increased lower frequency spread as measured by standard deviation was directly proportional to the length of intubation.