Turner D J, Stick S M, Lesouëf K L, Sly P D, Lesouëf P N
Department of Pediatrics, University of Western Australia, Perth.
Am J Respir Crit Care Med. 1995 May;151(5):1441-50. doi: 10.1164/ajrccm.151.5.7735598.
We have developed a new technique that allows assessment of infant lung function over an extended volume range. The lungs are rapidly inflated to a predetermined inflation pressure (PP) using a modified diaphragm pump. Forced expiratory flow-volume (FEFV) curves are then generated from raised lung volumes using an inflatable plastic jacket. We studied 26 normal infants with a median age of 14 mo (range, 3 to 23 mo). FEFV curves were obtained in each infant from end-tidal inspiration and from lung volumes set by a range of PP (15 to 20 cm H2O). Mean (SE) volume above FRC was 107 ml (9 ml), and mean forced expiratory time was 0.73 s (0.05 s) at end-tidal inspiration. Both measurements increased progressively with increases in PP to 251 ml (13 ml) and 1.04 s (0.06 s), respectively, at 20 cm H2O PP (p < 0.0001). Mean intrasubject coefficient of variation was 15.5% (95% confidence interval, 12 to 19%) for maximal flow at FRC, but it was less than 6% (95% CI, 4 to 8%) for forced expiratory volume-time (FEVt) measurements at all levels of PP. Twenty-seven recurrently wheezy infants with a median age of 13 mo (range, 6 to 18 mo) were subsequently studied using a PP of 17.5 cm H2O. Wheezy infants had a lower VmaxFRC [mean (1.39 ml/s/cm) and 95% CI (1.15 to 1.63 ml/s/cm)] than did normal infants (1.78 ml/s/cm; CI, 1.51 to 2.05) (p < 0.05). FEV1 measurements were all lower in wheezy infants than in normals infants: mean FEV0.5, 1.86 ml/cm (CI, 1.73 to 1.98) and 2.31 ml/cm (CI, 2.15 to 2.48), respectively (p < 0.0001); FEV0.75, 2.20 ml/cm (CI, 2.07 to 2.32) and 2.72 ml/cm (CI, 2.52 to 2.91), respectively (p < 0.0001); FEV1.0, 2.42 ml/cm (CI, 2.26 to 2.58) and 2.84 ml/cm (CI, 2.63 to 3.06), respectively (p < 0.005). The Ci values of each FEVt measurement did not overlap between the wheezy and normal groups; however, the CI values of VmaxFRC overlapped markedly. In addition, FEVt parameters showed greater sensitivity in detecting reduced lung function (71 to 89%) than did VmaxFRC parameters (56%). We conclude that (1) FEVt measurements derived from a lung volume set by a standardized pressure are more reproducible than flow measurements in the tidal volume range; (2) FEVt measurements are significantly lower in wheezy infants than in normal infants, show less overlap than flow measurements in the tidal volume range, and therefore are better able to separate the two populations.
我们开发了一种新技术，可在更大的容积范围内评估婴儿肺功能。使用改良的隔膜泵将肺迅速充气至预定的充气压力（PP）。然后使用可充气塑料外套从升高的肺容积生成用力呼气流量-容积（FEFV）曲线。我们研究了26名正常婴儿，中位年龄为14个月（范围3至23个月）。在每个婴儿中，从潮气末吸气以及从一系列PP（15至20 cm H₂O）设定的肺容积获取FEFV曲线。在潮气末吸气时，高于功能残气量（FRC）的平均（标准误）容积为107 ml（9 ml），平均用力呼气时间为0.73 s（0.05 s）。随着PP增加至20 cm H₂O的PP时，这两个测量值分别逐渐增加至251 ml（13 ml）和1.04 s（0.06 s）（p < 0.0001）。在FRC时最大流量的平均受试者内变异系数为15.5%（95%置信区间，12%至19%），但在所有PP水平下，用力呼气容积-时间（FEVt）测量的变异系数均小于6%（95% CI，4%至8%）。随后使用17.5 cm H₂O的PP研究了27名反复喘息婴儿，中位年龄为13个月（范围6至18个月）。喘息婴儿的FRC时最大流速[平均（1.39 ml/s/cm）和95% CI（1.15至1.63 ml/s/cm）]低于正常婴儿（1.78 ml/s/cm；CI，1.51至2.05）（p < 0.05）。喘息婴儿的FEV₁测量值均低于正常婴儿：平均FEV₀.₅分别为1.86 ml/cm（CI，1.73至1.98）和2.31 ml/cm（CI，2.15至2.48）（p < 0.0001）；FEV₀.₇₅分别为2.20 ml/cm（CI，2.07至2.32）和2.72 ml/cm（CI，2.52至2.91）（p < 0.0001）；FEV₁.₀分别为2.42 ml/cm（CI，2.26至2.58）和2.84 ml/cm（CI，2.63至3.06）（p < 0.005）。每个FEVt测量的CI值在喘息组和正常组之间不重叠；然而，FRC时最大流速的CI值有明显重叠。此外，FEVt参数在检测肺功能降低方面比FRC时最大流速参数（56%）表现出更高的敏感性（71%至89%）。我们得出结论：（1）从由标准化压力设定的肺容积得出的FEVt测量值比潮气量范围内的流量测量值更具可重复性；（2）喘息婴儿的FEVt测量值显著低于正常婴儿，在潮气量范围内的重叠比流量测量值少，因此能更好地区分这两组人群。
