Schwartz A R, O'Donnell C P, Baron J, Schubert N, Alam D, Samadi S D, Smith P L
Johns Hopkins Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA.
Am J Respir Crit Care Med. 1998 Apr;157(4 Pt 1):1051-7. doi: 10.1164/ajrccm.157.4.9706067.
The structural properties of the upper airway determine its collapsibility during periods of muscle hypotonia. Both rapid-eye-movement (REM) sleep and increases in nasal pressure (PN) produce hypotonia, which persists even after nasal pressure is abruptly reduced. To determine the factors that influence the collapsibility of the hypotonic airway, the critical pressure (Pcrit) and nasal resistance upstream to the site of pharyngeal collapse (RN) were measured in the first three breaths after abrupt reductions in PN during non-REM and REM sleep. PN was reduced abruptly from 15.2+/-3.2 cm H2O (mean +/- SD) for three breaths in 19 apneic patients. Upper-airway pressure-flow relationships were analyzed to determine Pcrit for each breath in non-REM and REM sleep. We found that Pcrit rose (collapsibility increased, p < 0.001) and RN fell (p = 0.02) between the first and third breath after the decrease in PN, whereas no difference in Pcrit was detected between sleep stages. In six patients, genioglossus-muscle electromyograms (EMGs) were recorded. Peak phasic activity rose between the first and third breath (p = 0.03), but tonic and peak phasic EMG activity fell in REM as compared with non-REM sleep (p < 0.001). We conclude that the hypotonic upper airway becomes most collapsible by the third breath after an abrupt decrease in PN, regardless of sleep stage and despite an increase in genioglossus-muscle activity. Our findings suggest that predominantly mechanical rather than neuromuscular factors modulate the properties of the pharynx after abrupt reductions in nasal pressure.
上气道的结构特性决定了其在肌张力减退期间的可塌陷性。快速眼动（REM）睡眠和鼻压（PN）升高均会导致肌张力减退，即使鼻压突然降低，这种减退仍会持续。为了确定影响低张性气道可塌陷性的因素，在非快速眼动睡眠和快速眼动睡眠期间，于PN突然降低后的前三呼吸周期中，测量了临界压力（Pcrit）和咽塌陷部位上游的鼻阻力（RN）。在19例呼吸暂停患者中，PN从15.2±3.2 cm H2O（平均值±标准差）突然降低并维持三呼吸周期。分析上气道压力-流量关系以确定非快速眼动睡眠和快速眼动睡眠中每次呼吸的Pcrit。我们发现，PN降低后，第一呼吸周期和第三呼吸周期之间Pcrit升高（可塌陷性增加，p<0.001），RN降低（p = 0.02），而睡眠阶段之间未检测到Pcrit有差异。在6例患者中，记录了颏舌肌肌电图（EMG）。第一呼吸周期和第三呼吸周期之间，相位活动峰值升高（p = 0.03），但与非快速眼动睡眠相比，快速眼动睡眠中的紧张性和相位活动峰值EMG活动降低（p<0.001）。我们得出结论，PN突然降低后，无论睡眠阶段如何，尽管颏舌肌活动增加，但低张性上气道在第三呼吸周期时变得最易塌陷。我们的研究结果表明，鼻压突然降低后，主要是机械因素而非神经肌肉因素调节咽部特性。
