RATIONALE No systematic investigation into dyspnea in patients receiving prolonged ventilation (>21 days) after recovering from critical-illness has been published. OBJECTIVES To determine magnitude, nature and pathophysiological basis of dyspnea during an unassisted-breathing trial in prolonged-ventilation patients. METHODS Dyspnea intensity and descriptor selection were investigated in 27 prolonged-ventilation patients during a 60-min unassisted-breathing trial. Pressure-time product (PTP), respiratory mechanics, and transcutaneous PCO2 (PtcCO2) were also measured. MEASUREMENTS AND MAIN RESULTS Of 10 patients who reported dyspnea during assist-control ventilation, 9 (90.0%) selected "Not getting enough air" to characterize dyspnea. Tidal-volume setting was lower in dyspneic than non-dyspneic patients: 480.0 versus 559.4 ml (p<0.046). During the unassisted-breathing trial (n=26), patients developed increases in dyspnea (p<0.01) and PtcCO2 (p<0.01), but no change in minute ventilation. Dyspnea score was strongly linked to PtcCO2 (p<0.012) and airway resistance (p<0.013) but not respiratory work (although PTP was almost 3 times higher than normal). At 60 min into the trial, 83.3% of patients selected "Not getting enough air" on its own or in combination with "Too much effort" to describe discomfort whereas only 16.7% selected "Too much effort" on its own (p<0.001). Across the dyspnea spectrum, patients chose "Not getting enough air" overwhelmingly over other descriptor options (p<0.001). CONCLUSIONS Patients developed increases in dyspnea and PtcCO2 but unchanged minute ventilation and work of breathing during an unassisted-breathing trial; patients selected air-hunger descriptors overwhelmingly over excessive effort; the observations support the belief that air hunger results from heightened respiratory-center stimulation combined with incapacity to increase minute ventilation.

中文翻译：

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空气饥饿远远超过机械通气和脱机试验期间的呼吸困难努力感。


基本原理 尚未发表对危重病恢复后接受延长通气 （>21 天） 的患者呼吸困难的系统研究。目的 确定长时间通气患者无辅助呼吸试验期间呼吸困难的程度、性质和病理生理学基础。方法 在 60 分钟的无辅助呼吸试验中，调查了 27 名长通气患者的呼吸困难强度和描述符选择。还测量了压力时间积 （PTP） 、呼吸力学和经皮 PCO2 （PtcCO2）。测量和主要结果在报告辅助控制通气期间呼吸困难的 10 例患者中，9 例 （90.0%） 选择“空气不足”来表征呼吸困难。呼吸困难患者的潮气量设置低于非呼吸困难患者：480.0 对 559.4 ml （p<0.046）。在无辅助呼吸试验 （n=26） 期间，患者出现呼吸困难 （p<0.01） 和 PtcCO2 （p<0.01） 增加，但每分钟通气量没有变化。呼吸困难评分与 PtcCO2 （p<0.012） 和气道阻力 （p<0.013） 密切相关，但与呼吸功无关 （尽管 PTP 几乎比正常值高 3 倍）。在试验进行 60 分钟时，83.3% 的患者选择了“没有得到足够的空气”单独或与“太多努力”相结合来描述不适，而只有 16.7% 的患者选择了“太多努力”来单独描述 （p<0.001）。在整个呼吸困难谱系中，患者压倒性地选择了“没有得到足够的空气”而不是其他描述符选项 （p<0.001）。 结论 在无辅助呼吸试验期间，患者呼吸困难和 PtcCO2 增加，但每分钟通气量和呼吸功没有变化;患者压倒性地选择了空气饥饿描述符，而不是过度努力;这些观察结果支持这样一种信念，即空气饥饿是由于呼吸中心刺激增加加上无法增加每分钟通气量造成的。