Why is respiratory rate so important?

in mental illness, particularly the syndrome of bipolar illness.

“Alveolar ventilation (a product of respiratory rate and tidal volume) is normally carefully controlled by the actions of central and peripheral chemoreceptors and lung receptors. Ventilation is driven by both the arterial partial pressure of oxygen (Pao2) and the arterial partial pressure of carbon dioxide (Paco2), with Paco2 being the most important driver. The body attempts to correct hypoxaemia and hypercarbia by increasing both tidal volume and respiratory rate. People like Paula cannot easily raise their respiratory rate at rest and thus cannot easily correct for hypoxaemia or hypercapnia. These conditions can be detected by measuring the respiratory rate.

 In effect, the respiratory rate is an important indicator of a severe derangement in many body systems, not just the respiratory system, and is therefore a key predictor of adverse events.

Pulse oximetry is not an indicator of adequate ventilation, and an arterial blood gas measurement is needed to identify hypercarbia.  Abnormal respiratory rate is a marker of serious illness.” Respiratory rate: the neglected vital sign Michelle A Cretikos, Rinaldo Bellomo, Ken Hillman, Jack Chen, Simon Finfer and Arthas Flabouris Med J Aust 2008; 188 (11): 657-659. ||  doi: 10.5694/j.1326-5377.2008.tb01825.x   Published online: 2 June 2008

If accompanied by changes in personality, locomotor activity and cognition, then arterial blood gases are necessary to look for respiratory acidosis and raised levels of carbon dioxide in the blood due to ventilatory failure. Because of mental confusion, ventilatory failure in causing mental illness is missed and is not treated.