Watson R A, Pride N B
Respiratory Medicine National Heart and Lung Institute, Faculty of Medicine, Imperial College, London, United Kingdom.
J Appl Physiol (1985). 2005 Feb;98(2):512-7. doi: 10.1152/japplphysiol.00430.2004. Epub 2004 Oct 8.
Reduced functional residual capacity (FRC) is consistently found in obese subjects. In 10 obese subjects (mean +/- SE age 49.0 +/- 6 yr, weight 128.4 +/- 8 kg, body mass index 44 +/- 3 kg/m2) without respiratory disease, we examined 1) supine changes in total lung capacity (TLC) and subdivisions, 2) whether values of total respiratory resistance (Rrs) are appropriate for mid-tidal lung volume (MTLV), and 3) estimated resistance of the nasopharyngeal airway (Rnp) in both sitting and supine postures. The results were compared with those of 13 control subjects with body mass indexes of <27 kg/m2. Rrs at 6 Hz was measured by applying forced oscillation at the mouth (Rrs,mo) or the nose (Rrs,na); Rnp was estimated from the difference between sequential measurements of Rrs,mo and Rrs,na. All measurements were made when subjects were seated and when supine. Obese subjects when seated had a restrictive defect with low TLC and FRC-to-TLC ratio; when supine, TLC fell 80 ml and FRC fell only 70 ml compared with a mean supine fall of FRC of 730 ml in control subjects. Values of Rrs,mo and Rrs,na at resting MTLV in obese subjects were about twice those in control subjects in both postures. Relating total respiratory conductance (1/Rrs) to MTLV, the increase in Rrs,mo in obese subjects was only partly explained by their reduced MTLV. Rnp was increased in some obese subjects in both postures. Despite the increased extrapulmonary mass load in obese subjects, further falls in TLC and FRC when supine were negligible. Rrs,mo at isovolume was increased. Further studies are needed to examine the causes of reduced TLC and increases in Rrs,mo and sometimes in Rnp in obese subjects.
肥胖受试者中经常发现功能残气量（FRC）降低。在10名无呼吸系统疾病的肥胖受试者（平均±标准误年龄49.0±6岁，体重128.4±8 kg，体重指数44±3 kg/m²）中，我们检查了：1）仰卧位时肺总量（TLC）及其细分部分的变化；2）总呼吸阻力（Rrs）值是否适用于潮气量中期肺容积（MTLV）；3）测量坐位和仰卧位时的鼻咽气道阻力（Rnp）。将结果与13名体重指数<27 kg/m²的对照受试者的结果进行比较。通过在口腔（Rrs,mo）或鼻腔（Rrs,na）施加强迫振荡来测量6 Hz时的Rrs；Rnp通过连续测量Rrs,mo和Rrs,na之间的差异来估计。所有测量均在受试者坐位和仰卧位时进行。肥胖受试者坐位时存在限制性缺陷，TLC和FRC与TLC的比值较低；仰卧位时，与对照受试者仰卧位时FRC平均下降730 ml相比，TLC下降80 ml，FRC仅下降70 ml。肥胖受试者静息MTLV时Rrs,mo和Rrs,na的值在两种体位下均约为对照受试者的两倍。将总呼吸传导率（1/Rrs）与MTLV相关联，肥胖受试者中Rrs,mo的增加仅部分归因于MTLV的降低。一些肥胖受试者在两种体位下Rnp均增加。尽管肥胖受试者肺外质量负荷增加，但仰卧位时TLC和FRC的进一步下降可忽略不计。等容时Rrs,mo增加。需要进一步研究以检查肥胖受试者TLC降低、Rrs,mo增加以及有时Rnp增加的原因。
