Pulmonary Function and Clinical Exercise Physiology Unit, Division of Respiratory Diseases, Department of Medicine, Federal University of Sao Paulo (UNIFESP), São Paulo, Brazil.
Respirology. 2010 Nov;15(8):1185-91. doi: 10.1111/j.1440-1843.2010.01846.x.
Proportional assist ventilation (PAV) has been proposed as a more physiological modality of non-invasive ventilation, thereby reducing the potential for deleterious cardio-circulatory effects during exercise, in patients with COPD. We therefore evaluated whether PAV modulates the kinetic and 'steady-state' haemodynamic responses to exercise in patients with moderate-to-severe COPD.
Twenty patients underwent constant-load (75-80% peak work rate) cycle ergometer exercise testing to the limit of tolerance (T(lim)), while receiving PAV or breathing spontaneously. Stroke volume (SV), heart rate (HR) and cardiac output (CO) were monitored by impedance cardiography.
Compared with unassisted breathing, PAV increased T(lim) in 8/20 patients (median improvement 113% (range 8 to 212) vs -20% (range -40 to -9)). PAV had no significant effects on 'steady-state' haemodynamic responses either in patients with or those without increased T(lim) (P > 0.05). However, at the onset of exercise, SV kinetics were slowed with PAV, in 13/15 patients with analysable data. HR dynamics remained unaltered or failed to accelerate sufficiently in nine of these patients, thereby slowing CO kinetics (T(1/2) 61 s (range 81-30) vs 89 s (range 100-47)). These deleterious effects were not, however, associated with PAV-induced changes in T(lim) (P > 0.05).
PAV slowed the SV and CO kinetics at the onset of high-intensity exercise in selected patients with moderate-to-severe COPD. However, these adverse effects of PAV disappeared during the stable phase of exercise, and were not related to the ergogenic potential of PAV in this patient population.
比例辅助通气（PAV）被认为是一种更符合生理的无创通气模式，从而降低了 COPD 患者在运动过程中产生有害的心肺循环作用的可能性。因此，我们评估了 PAV 是否调节了中重度 COPD 患者运动时的动力学和“稳态”血流动力学反应。
20 例患者接受恒负荷（75-80%峰值工作率）功率自行车运动试验至耐受极限（Tlim），同时接受 PAV 或自主呼吸。通过阻抗心动图监测每搏量（SV）、心率（HR）和心输出量（CO）。
与自主呼吸相比，PAV 增加了 8/20 例患者（Tlim 中位数改善 113%（范围 8-212）%与-20%（范围-40-9）%）。在 Tlim 增加或不增加的患者中，PAV 对“稳态”血流动力学反应均无显著影响（P>0.05）。然而，在运动开始时，13/15 例可分析数据的患者的 SV 动力学因 PAV 而减慢。在这些患者中，有 9 例 HR 动力学保持不变或未能充分加速，从而使 CO 动力学减慢（T1/2 61 s（范围 81-30）%与 89 s（范围 100-47）%）。然而，这些有害影响与 PAV 引起的 Tlim 变化无关（P>0.05）。
在选定的中重度 COPD 患者中，PAV 在高强度运动开始时使 SV 和 CO 动力学减慢。然而，PAV 的这些不利影响在运动的稳定期消失，并且与 PAV 在该患者人群中的运动促进作用无关。
