Central neurogenic hyperventilation

Abnormal pattern of breathing

Central neurogenic hyperventilation (CNH) is an abnormal pattern of breathing characterized by deep and rapid breaths at a rate of at least 25 breaths per minute. Increasing irregularity of this respiratory rate generally is a sign that the patient will enter into coma. CNH is unrelated to other forms of hyperventilation, like Kussmaul's respirations. CNH is the human body's response to reduced carbon dioxide levels in the blood. This reduction in carbon dioxide is caused by contraction of cranial arteries from damage caused by lesions in the brain stem. However, the mechanism by which CNH arises as a result from these lesions is still very poorly understood. Current research has yet to provide an effective means of treatment for the rare number of patients who are diagnosed with this condition.

Symptoms of CNH have been observed to vary according to the progression of CNH. The initial symptoms of CNH include a low arterial partial pressure of carbon dioxide, a high or normal arterial partial pressure of oxygen, high arterial pH, and tachypnea. The partial pressure of carbon dioxide has been noted by Yushi et al. to drop as low as 6.7 mmHg, while oxygen saturation remains at 99 100%.

For the clinical diagnosis of CNH, it is essential that the symptoms, particularly respiratory alkalosis, persist while the patient is both awake and asleep. The presence of hyperventilation during sleep excludes any possible emotional or psychogenic causes for the sustained hyperventilation. There must also be no evidence of drug or metabolic causes, including cardiac or pulmonary disease, or recent or current use of respiration stimulating drugs. Plum and Swanson described the symptoms of nine comatose patients, defining CNH as a syndrome consisting primarily of elevated arterial oxygen tension, decreased arterial carbon dioxide tension, and progressive tachypnea. Postmortem examination of the nine patients' brains reported by Plum and Swanson, revealed necrosis of the central pons in five of the nine patients, and indirect compression of the pons in one additional patient. The condition is considered extremely uncommon, and only 21 additional cases of tumor inducing CNH were reported up until 2005.

Current mechanisms by which CNH functions still remain poorly developed. In addition, a standard form of treatment has not been established to treat CNH. These characteristics make CNH an important condition that still needs to be investigated in adults and children, though the extreme rarity of the condition makes it difficult for research to successfully examine clinical cases.