Turnbull Chris D, Manuel Ari R, Stradling John R
Oxford Centre for Respiratory Medicine and NIHR Oxford Biomedical Research Centre, Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, OX3 7LJ, UK.
Sleep Breath. 2016 May;20(2):647-52. doi: 10.1007/s11325-015-1267-y. Epub 2015 Oct 8.
The pressures delivered by autotitrating continuous positive airways pressure (CPAP) devices not only treat obstructive sleep apnoea (OSA) effectively but also give potentially interesting physiological information about the forces impinging on the pharynx. In earlier work from this unit, we used correlations between autoCPAP pressure and both OSA severity and obesity, to construct an algorithm to estimate the fixed CPAP pressure a patient required for subsequent clinical use. We wished to discover if these relationships could be reliably extended to a much more obese group.
We performed a prospective cohort study in an obese population. Measurements of obesity were made, OSA severity was recorded, and the 95th centile autoCPAP pressure was recorded during 1 week of autoCPAP. Spearman's rank correlation was performed between measurements of obesity and autoCPAP pressure, and between OSA severity and autoCPAP pressure.
Fifty-four obese individuals (median body mass index (BMI) 43.0 kg/m(2)), 52 % of whom had OSA (apnoea-hypopnoea index (AHI) ≥ 15), had a median 95th centile autoCPAP pressure of 11.8 cmH2O. We found no significant correlation between autoCPAP pressure and neck circumference, waist circumference or BMI. There was a moderate correlation between autoCPAP pressure and OSA severity (AHI r = 0.34, p = 0.02; oxygen desaturation index (ODI) r = 0.48, p < 0.001).
In this population, neither BMI nor neck circumference nor waist circumference is predictive of autoCPAP pressure. Therefore, the previously derived algorithm does not adequately predict the fixed CPAP pressure for subsequent clinical use in these obese individuals. In addition, some subjects without OSA generated high autoCPAP pressures, and thus, the correlation between OSA severity and autoCPAP pressure was only moderate.
自动调压持续气道正压通气（CPAP）设备所输送的压力不仅能有效治疗阻塞性睡眠呼吸暂停（OSA），还能提供有关作用于咽部的力量的潜在有趣生理信息。在本研究组早期的工作中，我们利用自动CPAP压力与OSA严重程度及肥胖之间的相关性，构建了一种算法，以估计患者后续临床使用所需的固定CPAP压力。我们希望了解这些关系是否能可靠地扩展到更肥胖的人群。
我们在肥胖人群中进行了一项前瞻性队列研究。测量肥胖情况，记录OSA严重程度，并在自动CPAP治疗1周期间记录第95百分位数的自动CPAP压力。对肥胖测量值与自动CPAP压力之间以及OSA严重程度与自动CPAP压力之间进行Spearman等级相关性分析。
54名肥胖个体（中位体重指数（BMI）为43.0kg/m²），其中52%患有OSA（呼吸暂停低通气指数（AHI）≥15），第95百分位数的自动CPAP压力中位数为11.8cmH₂O。我们发现自动CPAP压力与颈围、腰围或BMI之间无显著相关性。自动CPAP压力与OSA严重程度之间存在中度相关性（AHI r = 0.34，p = 0.02；氧饱和度下降指数（ODI）r = 0.48，p < 0.001）。
在该人群中，BMI、颈围和腰围均不能预测自动CPAP压力。因此，先前推导的算法不能充分预测这些肥胖个体后续临床使用的固定CPAP压力。此外，一些无OSA的受试者产生了较高的自动CPAP压力，因此，OSA严重程度与自动CPAP压力之间的相关性仅为中度。
