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目的:通过测算呼气时间常数（τn E）监测无创正压通气（NPPV）时不同肺力学模型的呼气阻力（Rexp）。n 方法:使用ASL 5000机械模拟肺模拟体质量为65~70 kg的半卧位健康成年人、高气道阻力及高气道阻力合并低胸肺顺应性（混合性通气障碍）患者，设置系统顺应性（Cn rs）为25（混合性通气障碍）和50 ml/cmHn 2O（1 cmHn 2O=0.098 kPa），Rn exp为5（健康成年人）和20 cmHn 2O·Ln -1·sn -1，吸气时间为1.6 s，呼吸频率为15次/min。Respironics V60呼吸机以S/T模式运行，呼气末正压（PEEP）为5 cmHn 2O，调整吸气压力水平使呼吸机输出潮气量（Vn T）分别达到5、7和10 ml/kg，后备通气频率为10次/min。收集系统泄漏量为25~28 L/min时的通气参数吸入潮气量（Vn TI）、呼出潮气量（Vn TE）、漏气量（Vn leak）、吸气峰压（PIP）、吸气峰流量（PIF）、呼气峰流量（PEF）和呼气时75%潮气量处的流量（TEFn 75）变化并测算τn E、Cn rs和Rn exp。n 结果:随着Vn TI、Vn TE的增大，Vn leak、PIP、PIF和PEF逐渐增高，Vn T为10 ml/kg时混合性通气障碍模型的PIP达到28 cmHn 2O, 3种肺力学模型的PIF和PEF较Vn T为5 ml/kg时增高近一倍（均n P0.01）。不同Vn T对高气道阻力模型的τn E值测算无明显影响。3种肺力学模型的Cn rs测算值均随Vn T增大而逐渐减小，高气道阻力条件下Cn rs值测算误差在Vn T为7 ml/kg时可<20%。随着通气支持水平的增高，3种肺力学模型的Rn exp测算值均逐渐增高，Vn T为7 ml/kg时Rn exp测算值与预设值的差异更低（<10%）。n 结论:通过测算τn E，可实现在不阻断自主呼吸连续监测接受NPPV支持患者的Rn exp。适宜的Vn T（7 ml/kg）是减少测算误差的关键，同时也保证有效的通气支持。n “,”Objective:To evaluate the expiratory resistance (Rn exp) in different lung mechanics models during noninvasive positive pressure ventilation (NPPV) according to estimated calculation of expiratory time constants (τn E) .n Methods:ASL 5000 mechanical lung simulator was used to mimic a semi-recumbent subject with a body mass of 65-70 kg, either being a healthy adult or a patient with high airway resistance with or without low thoraco-pulmonary compliance (mixed ventilatory disorder) . The system settings included: compliance (Cn rs) , 25 (for mixed ventilatory disorder) or otherwise 50 ml/cmHn 2O (1 cmHn 2O=0.098 kPa) ; Rn exp, 5 (for healthy adult) or otherwise 20 cmHn 2O·Ln -1·sn -1; inspiratory time, 1.6 s; respiratory rate, 15 times/min. The Respironics V60 ventilator was set to operate in S/T mode with a positive end-expiratory pressure (PEEP) of 5 cmHn 2O. Inspiratory pressure was adjusted to maintain a tidal ventilator output (Vn T) of 5, 7 and 10 ml/kg, respectively, and a backup ventilation frequency of 10 times/min. Ventilation parameters[inspiratory tidal volume (Vn TI) , expiratory tidal volume (Vn TE) , system leakage (Vn leak) , peak inspiratory pressure (PIP) , peak inspiratory flow (PIF) , peak expiratory flow (PEF) and the expiratory flow at 75% expiratory tidal volume (TEFn 75) ] were recorded at the Vn leak level of 25-28 L/min. Thereby τ n E, Cn rs and Rn exp were estimated and evaluated.n Results:With increasing Vn TI and Vn TE, Vn leak, PIP, PIF and PEF gradually increased. At the Vn T of 10 ml/kg, the PIP in the mixed ventilatory disorder model reached 28 cmHn 2O, and the PIF and PEF values in all of the three lung mechanics models were nearly two times higher than those at the Vn T of 5 ml/kg (all n P0.01) . The level of Vn T did not interfere obviously with the calculated τ n E value in the high airway resistance model. In all of the three lung mechanics models, the estimated Cn rs values gradually decreased with increasing Vn T. Under high airway resistance, the error of calculated Cn rs value was <20% when the V n T was 7 ml/kg. With increasing ventilation support, the measured Rn exp gradually increased in all of the three lung mechanics models. When the Vn T was 7 ml/kg, the difference between the measured Rn exp and the preset value became even lower (<10%) .n Conclusion:Estimated calculation of τ n E may allow for continuous monitoring of Rn exp in patients on NPPV support without interference of spontaneous breathing. Proper selection of Vn T (7 ml/kg) can be the key to reduce the measurement error while ensuring effective ventilation support.n