The prevalence of central apnoea and periodic breathing is increased in the elderly. This implies that the chemical control of breathing might become less stable with ageing. To investigate this, we measured loop gain in healthy elderly individuals using proportional assist ventilation. Loop gain is an engineering term that describes the stability of a system controlled by feedback loops, such as the respiratory control system. A loop gain close to zero indicates a stable system, whereas a loop gain close to or greater than one indicates an unstable system. Eleven healthy elderly subjects were studied with a mean ± s.d. age and body mass index (BMI) of 71 ± 5 years and 25 ± 3 kg m−2, respectively. We also studied a small group of elderly individuals with obstructive sleep apnoea (OSA) for comparison (n = 3, age 68 ± 1 years, BMI 32 ± 11 kg m−2). Comparisons were made with previously studied young individuals (age 27 ± 4 years, BMI 23 ± 1 kg m−2). We found significantly lower loop gains in the healthy elderly group (loop gain ≤ 0.25) compared with the young group (loop gain ≤ 0.47, P = 0.001). Also, we found quite low loop gains in the elderly OSA group (loop gain ≤ 0.26). We conclude that the chemical control of breathing does not become unstable with ageing and is thus an unlikely cause of central (and possibly obstructive) apnoeas in this population.
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机译：老年人中枢性呼吸暂停和定期呼吸的患病率增加。这意味着随着年龄的增长，呼吸的化学控制可能会变得不稳定。为了对此进行调查，我们使用比例辅助通气测量了健康老年人的循环增益。环路增益是一个工程术语，用于描述受反馈环路控制的系统（如呼吸控制系统）的稳定性。环路增益接近零表示系统稳定，而环路增益接近或大于1表示系统不稳定。对11名健康的老年受试者进行了平均±s.d的研究。年龄和体重指数（BMI）分别为71±5岁和25±3 kg m -2 。我们还研究了一小群患有阻塞性睡眠呼吸暂停（OSA）的老年个体进行比较（n = 3，年龄68±1岁，BMI 32±11 kg m −2 ）。与先前研究的年轻人（年龄27±4岁，BMI 23±1 kg m -2 ）进行了比较。我们发现健康的老年组（环路增益≤0.25）与年轻组（环路增益≤0.47，P = 0.001）相比，环路增益显着降低。此外，我们发现老年OSA组的环路增益非常低（环路增益≤0.26）。我们得出的结论是，呼吸的化学控制不会随着年龄的增长而变得不稳定，因此这不是该人群中枢性（可能是阻塞性）呼吸暂停的原因。
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