Ingenito E P, Pichurko B M, Lafleur J, Drazen J M, Ingram R H, Solway J
Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.
Lung. 1990;168(1):23-34. doi: 10.1007/BF02719670.
To determine whether changes in breathing pattern alone affect respiratory heat loss (RHL) and the constrictor response to cold dry gas hyperpnea in asthmatic subjects, we performed the following 2 part study: first we measured RHL in 8 asthmatic and 8 normal subjects during controlled eucapnic hyperpnea while they breathed at inspiratory to expiratory ratios (I/E) of 1:3, 3:1, and 2:2, and we recorded postchallenge forced expiratory volume in 1 sec (FEV1) in the asthmatic group; we then performed the same measurements in 8 asthmatic and 8 normal subjects at fixed target minute ventilation (VE) for tidal volumes of 0.2 X Forced vital capacity (FVC), 0.4 X FVC, and 0.6 X FVC by varying the target respiratory rate appropriately. Our results show that (1) increasing I/E ratio or tidal volume-frequency ratio (VT/f) at fixed VE produced small but statistically significant increases (p less than 0.05) in overall heat loss per unit volume of respired gas (RHL/VE) in both asthmatic and nonasthmatic subjects of 1-4 cal/L; (2) changes in breathing pattern alone did not affect bronchoconstrictor response as assessed by lack of change in slopes and intercepts of % delta FEV1 vs. RHL dose-response curves; and (3) the increase in RHL per unit volume of respired gas resulting from increasing VT/f ratios during cold gas hyperpnea was significantly greater in asthmatic than in nonasthmatic subjects. We conclude that changes in breathing pattern may affect overall RHL measured at the mouth, although the maximum effect of such changes in both asthmatic and nonasthmatic subjects is small (10-15%); that such changes do not significantly alter airway constrictor response in asthmatic persons; and (3) that the effects of changing breathing pattern on RHL may be more pronounced in asthmatic than nonasthmatic subjects, which suggests that the asthmatic group may be less able to adapt to factors that alter the magnitude and site of RHL.
为了确定单纯呼吸模式的改变是否会影响哮喘患者的呼吸热损失（RHL）以及对冷干气体过度通气的收缩反应，我们进行了以下两部分研究：首先，我们在8名哮喘患者和8名正常受试者进行受控等碳酸过度通气时，测量了他们以吸气与呼气比（I/E）为1:3、3:1和2:2呼吸时的RHL，并记录了哮喘组激发后1秒用力呼气量（FEV1）；然后，我们通过适当改变目标呼吸频率，在8名哮喘患者和8名正常受试者中，针对潮气量为0.2×用力肺活量（FVC）、0.4×FVC和0.6×FVC的固定目标分钟通气量（VE）进行了相同的测量。我们的结果表明：（1）在固定VE的情况下，增加I/E比或潮气量-频率比（VT/f）会使哮喘和非哮喘受试者每单位呼吸气体体积的总热损失（RHL/VE）产生虽小但具有统计学意义的增加（p<0.05），增加幅度为1 - 4卡/升；（2）单纯呼吸模式的改变并未影响支气管收缩反应，这通过%ΔFEV1与RHL剂量反应曲线的斜率和截距无变化得以评估；（3）在冷气体过度通气期间，哮喘患者因VT/f比增加导致的每单位呼吸气体体积RHL增加显著大于非哮喘患者。我们得出结论：呼吸模式的改变可能会影响口腔处测量的总体RHL，尽管哮喘和非哮喘受试者中这种改变的最大影响较小（10 - 15%）；这种改变不会显著改变哮喘患者的气道收缩反应；（3）改变呼吸模式对RHL的影响在哮喘患者中可能比非哮喘患者更明显，这表明哮喘组可能较难适应改变RHL大小和部位的因素。
