Polese G, Vitacca M, Bianchi L, Rossi A, Ambrosino N
Centro Regionale Fibrosi Cistica, Azienda Ospedaliera di Verona, Italy.
Eur Respir J. 2000 Sep;16(3):491-8. doi: 10.1034/j.1399-3003.2000.016003491.x.
This study was undertaken to assess the physiological effects of proportional assist ventilation (PAV), administered noninvasively through a nose mask, on ventilatory pattern, arterial blood gases, lung mechanics, and inspiratory muscle effort in stable, hypercapnic patients with chronic obstructive pulmonary disease. In 15 patients, PAV was set by adjusting volume assist (VA) and flow assist (FA) according to the "run-away" technique and the patient's comfort respectively. The level of support was fixed at 80% of the total possible assistance and averaged 13.9+/-4.1 cmH2O x L(-1) and 4.1+/-1.3 cmH2O x L(-1) x s for VA and FA, respectively. Continuous positive airway pressure (CPAP) was established at 2 cmH2O and then increased to 5 cmH2O. Physiological measurements were made during spontaneous breathing (SB), after more than 40 min of PAV, and 20 min after the rise in CPAP. On average, PAV improved ventilation (10.3+/-2.1 to 12.5+/-2.0 L x m(-1)), tidal volume (0.60+/-0.11 to 0.76+/-0.24 L), arterial oxygen tension and arterial carbon dioxide pressure (from 6.7+/-0.7 to 7.1+/-0.9 and from 7.6+/-1.0 to 7.2+/-1.2 kPa, respectively). During SB, pulmonary resistance and dynamic lung elastance averaged 15.0+/-7.6 cmH2O x L(-1) s and 15.8+/-8.0 cmH2O x L(-1), respectively. Assuming a normal chest wall elastance (5 cmH2O x L(-1)), VA and FA relieved respectively approximately 70% of the elastic and 30% of the resistive burden, with PAV set with the procedure of this study. The overall magnitude of the patients' inspiratory effort, measured by means of the oesophageal and diaphragmatic pressure time product in 10 patients was significantly reduced by PAV, on average, 328+/-122 to 226+/-118 (-31%) and 361+/-119 to 254+/-126 (-30%) cmH2O x min(-1), respectively. In 10 patients the electrical activity of the diaphragm (Edi) was also reduced by PAV to approximately 70%, on average, of the SB activity. The rise of CPAP 25 cmH2O did not cause any further significant change in the physiological variables. In all instances there was a good patient-ventilator interaction, the ventilatory breath never entering into the patient's neural expiratory time. These data show that nasal proportional assist ventilation can provide physiological benefits to the stable hypercapnic chronic obstructive pulmonary disease patients. In fact, proportional assist ventilation, which was well tolerated by all patients, unloaded the inspiratory muscles and improved arterial blood gases. Further studies can clarify whether these beneficial physiological effects of nasal proportional assist ventilation can bear profitable consequences in the overall clinical management of chronic obstructive pulmonary disease patients with chronic carbon dioxide retention.
本研究旨在评估经鼻面罩无创给予比例辅助通气（PAV）对稳定期、高碳酸血症慢性阻塞性肺疾病患者通气模式、动脉血气、肺力学及吸气肌做功的生理影响。15例患者中，PAV分别根据“失控”技术和患者舒适度调整容量辅助（VA）和流量辅助（FA）来设置。支持水平固定为总可能辅助量的80%，VA和FA的平均值分别为13.9±4.1 cmH₂O·L⁻¹和4.1±1.3 cmH₂O·L⁻¹·s。持续气道正压通气（CPAP）初始设置为2 cmH₂O，随后增至5 cmH₂O。在自主呼吸（SB）期间、PAV超过40分钟后以及CPAP升高20分钟后进行生理测量。平均而言，PAV改善了通气（从10.3±2.1至12.5±2.0 L·m⁻¹）、潮气量（从0.60±0.11至0.76±0.24 L）、动脉血氧分压和动脉血二氧化碳分压（分别从6.7±0.7至7.1±0.9以及从7.6±1.0至7.2±1.2 kPa）。在SB期间，肺阻力和动态肺弹性平均值分别为15.0±7.6 cmH₂O·L⁻¹·s和15.8±8.0 cmH₂O·L⁻¹。假设胸壁弹性正常（5 cmH₂O·L⁻¹），按照本研究的方法设置PAV时，VA和FA分别减轻了约70%的弹性负荷和30%的阻力负荷。通过食管和膈肌压力时间乘积测量的10例患者吸气做功的总体幅度，平均而言，PAV使其显著降低，分别从328±122降至226±118（-31%）和从361±119降至254±126（-30%）cmH₂O·min⁻¹。10例患者中，膈肌电活动（Edi）也因PAV平均降低至SB活动的约70%。CPAP升高至25 cmH₂O未导致生理变量进一步显著变化。在所有情况下，患者与呼吸机之间均有良好的相互作用，通气呼吸从未进入患者的神经呼气时间。这些数据表明，经鼻比例辅助通气可为稳定期高碳酸血症慢性阻塞性肺疾病患者带来生理益处。事实上，所有患者对比例辅助通气耐受性良好，其减轻了吸气肌负荷并改善了动脉血气。进一步研究可阐明经鼻比例辅助通气的这些有益生理效应在慢性二氧化碳潴留的慢性阻塞性肺疾病患者的整体临床管理中是否能产生有益后果。
