The apneustic centre (lower pons) prolongs inspiration; the pneumotaxic centre (upper pons/parabrachial nuclei) limits inspiration and facilitates expiration. A lesion of the pneumotaxic centre alone causes:

• A Apnoea — complete cessation of breathing
• B Biot breathing — irregular respiratory clusters with apnoeic pauses
• C Kussmaul breathing — deep regular hyperventilation
• D Apneusis — prolonged gasping inspiratory efforts with brief inadequate expirations ✓

Explanation

The pneumotaxic centre (nucleus parabrachialis) in the upper pons inhibits the apneustic centre and switches off inspiration, facilitating normal rhythmic breathing. When the pneumotaxic centre is lesioned (and vagal afferents from lung stretch receptors are also severed), the unopposed apneustic centre drives prolonged, sustained inspiratory cramps with shallow expiration — called apneusis. Biot breathing occurs with complete medullary lesions; Kussmaul is from metabolic acidosis; complete apnoea results from a medullary centre failure.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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