Final answer:
Apnoea refers to D. the cessation of breathing. It is a significant concern in central sleep apnea, where the brain's respiratory centers do not properly trigger breathing, leading to potential health risks.
Step-by-step explanation:
Apnoea, or more commonly known as sleep apnea, refers to D. the cessation of breathing. It is a disorder characterized by pauses in breathing or periods of shallow breathing during sleep. Central sleep apnea is a form where the respiratory centers of the brain do not respond properly to rising carbon dioxide levels, failing to stimulate the muscles involved in breathing regularly. This can lead to dangerous consequences, including stroke, heart failure, and in severe cases, it can be a contributing factor in sudden infant deaths (SID). Therefore, apnoea does not directly relate to low or high blood pressure or cardiac arrest, but it can indirectly contribute to serious health issues if left untreated.