Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil.
J Appl Physiol (1985). 2011 Nov;111(5):1400-9. doi: 10.1152/japplphysiol.00218.2011. Epub 2011 Jul 28.
Nasal expiratory positive airway pressure (nEPAP) delivered with a disposable device (Provent, Ventus Medical) has been shown to improve sleep-disordered breathing (SDB) in some subjects. Possible mechanisms of action are 1) increased functional residual capacity (FRC), producing tracheal traction and reducing upper airway (UA) collapsibility, and 2) passive dilatation of the airway by the expiratory pressure, carrying over into inspiration. Using MRI, we estimated change in FRC and ventilation, as well as UA cross-sectional area (CSA), in awake patients breathing on and off the nEPAP device. Ten patients with SDB underwent nocturnal polysomnography and MRI with and without nEPAP. Simultaneous images of the lung and UA were obtained at 6 images/s. Image sequences were obtained during mouth and nose breathing with and without the nEPAP device. The nEPAP device produced an end-expiratory pressure of 4-17 cmH(2)O. End-tidal Pco(2) rose from 39.7 ± 5.3 to 47.1 ± 6.0 Torr (P < 0.01). Lung volume changes were estimated from sagittal MRI of the right lung. Changes in UA CSA were calculated from transverse MRI at the level of the pharynx above the epiglottis. FRC determined by MRI was well correlated to FRC determined by N(2) washout (r = 0.76, P = 0.03). nEPAP resulted in a consistent increase in FRC (46 ± 29%, P < 0.001) and decrease in ventilation (50 ± 15%, P < 0.001), with no change in respiratory frequency. UA CSA at end expiration showed a trend to increase. During wakefulness, nEPAP caused significant hyperinflation, consistent with an increase in tracheal traction and a decrease in UA collapsibility. Direct imaging effects on the UA were less consistent, but there was a trend to dilatation. Finally, we showed significant hypoventilation and rise in Pco(2) during use of the nEPAP device during wakefulness and sleep. Thus, at least three mechanisms of action have the potential to contribute to the therapeutic effect of nEPAP on SDB.
经一次性使用设备（Provent、Ventus Medical）提供的鼻呼气正压通气（nEPAP）已被证明可改善某些患者的睡眠呼吸障碍（SDB）。可能的作用机制为 1）增加功能残气量（FRC），产生气管牵引，减少上气道（UA）塌陷，以及 2）呼气压力对气道产生被动扩张，延续至吸气。我们使用 MRI 来评估清醒患者在使用和不使用 nEPAP 设备时 FRC 和通气以及 UA 横截面积（CSA）的变化。10 名 SDB 患者接受了夜间多导睡眠图和 MRI 检查，包括使用和不使用 nEPAP。以 6 幅/秒的速度同时获得肺部和 UA 的图像。在使用和不使用 nEPAP 设备时，分别进行口鼻呼吸的图像序列采集。nEPAP 设备产生 4-17cmH2O 的呼气末压力。呼气末 Pco2 从 39.7±5.3mmHg 升高至 47.1±6.0mmHg（P<0.01）。通过对右肺的矢状 MRI 来估计肺容积的变化。通过在会厌上方的咽部进行的横断 MRI 来计算 UA CSA 的变化。通过 MRI 确定的 FRC 与通过 N2 冲洗法确定的 FRC 高度相关（r=0.76，P=0.03）。nEPAP 导致 FRC 持续增加（46±29%，P<0.001）和通气减少（50±15%，P<0.001），而呼吸频率没有变化。在呼气末，UA CSA 呈增加趋势。在清醒状态下，nEPAP 导致明显的过度充气，这与气管牵引增加和 UA 塌陷减少相一致。直接对 UA 的影像学影响不太一致，但存在扩张趋势。最后，我们发现清醒和睡眠期间使用 nEPAP 设备时存在明显的通气不足和 Pco2 升高。因此，至少有三种作用机制可能有助于 nEPAP 对 SDB 的治疗效果。
