Lim S, MacRae K D, Seed W A, Roberts C M
Department of Medicine, Charing Cross and Westminster Medical School, London, U.K.
Respir Med. 1998 Sep;92(9):1122-6. doi: 10.1016/s0954-6111(98)90405-x.
Guidelines on the management of chronic obstructive pulmonary disease (COPD) issued by the European Respiratory Society (ERS), British Thoracic Society (BTS), American Thoracic Society (ATS), and Department of Health for England and Wales (DoH) suggest differing values of forced expiratory volume in 1 s (FEV1) below which arterial blood gas analysis should be performed to determine the presence of severe hypoxaemia and possible long-term oxygen therapy (LTOT) requirement. This study aimed to determine the value of FEV1 at these different levels in screening for LTOT requirement defined as PaO2 < 7.3 kPa in subjects with stable COPD. Comparative measures were taken against other lung function tests of volume and diffusing capacity. A retrospective analysis of paired lung function and arterial oxygen measurements in 491 subjects was made. The positive and negative predictive values, sensitivity and specificity of FEV1 < 70% predicted (ERS), FEV1 < 50% predicted (ATS), FEV1 < 40% predicted (BTS) and FEV1 < 1.51 (DoH) were determined for fulfilling LTOT criteria (PaO2 < 7.3 kPa). The correlation between lung function variables and PaO2 was established. Logistic regression analysis was used to classify subjects with PaO2 < 7.3 kPa and PaO2 > or = 7.3 kPa. Using FEV1 to screen for LTOT requirement produced a high negative predictive value at all four suggested limits (FEV1 < 70% 100%, FEV1 < 50% 96%, FEV1 < 40% 95%, FEV1 < 1.51 97%). However, the positive predictive values were low (FEV1 < 70% 13%, FEV1 < 50% 16%, FEV1 < 40% 19%, FEV1 < 1.51 15%) as were sensitivities. No single lung function variable was a strong determinant of PaO2. FEV1 % pred (r = 0.40), FVC % pred (r = 0.34) and TLCO % pred (r = 0.27) had the strongest relationships. Logistic regression also placed FEV1 % pred and TLCO % pred as the best predictors of PaO2 < 7.3 kPa. We conclude no lung function variable correlates well with PaO2 in subjects with stable COPD. The best predictor of PaO2 < 7.3 kPa was FEV1 % pred. Whilst a low FEV1 is a poor predictor of LTOT requirement in an individual, PaO2 < 7.3 kPa is only found in subjects with a low FEV1. A high FEV1 may be used to exclude subjects from further investigation for LTOT and prevent unnecessary arterial sampling.
欧洲呼吸学会（ERS）、英国胸科学会（BTS）、美国胸科学会（ATS）以及英格兰和威尔士卫生部（DoH）发布的慢性阻塞性肺疾病（COPD）管理指南提出了不同的1秒用力呼气量（FEV1）值，低于该值时应进行动脉血气分析，以确定是否存在严重低氧血症以及是否可能需要长期氧疗（LTOT）。本研究旨在确定在这些不同水平下，FEV1值对于筛查LTOT需求（定义为稳定COPD患者的动脉血氧分压<7.3 kPa）的价值。同时针对其他肺容积和弥散功能测试进行了对比测量。对491名受试者的肺功能和动脉血氧测量结果进行了回顾性分析。确定了预测值低于70%（ERS）、低于50%（ATS）、低于40%（BTS）以及低于1.51（DoH）时FEV1的阳性和阴性预测值、敏感性和特异性，以确定是否符合LTOT标准（动脉血氧分压<7.3 kPa）。建立了肺功能变量与动脉血氧分压之间的相关性。采用逻辑回归分析对动脉血氧分压<7.3 kPa和动脉血氧分压≥7.3 kPa的受试者进行分类。使用FEV1筛查LTOT需求时，在所有四个建议限值下均产生了较高的阴性预测值（预测值低于70%为100%，低于50%为96%，低于当40%为95%，低于1.51为97%）。然而，阳性预测值较低（预测值低于70%为13%，低于50%为16%，低于40%为19%，低于1.51为15%），敏感性也较低。没有单一的肺功能变量是动脉血氧分压的强决定因素。预测FEV1%（r = 0.40）、预测用力肺活量（FVC）%（r = 0.34）和预测肺一氧化碳弥散量（TLCO）%（r = 0.27）的相关性最强。逻辑回归分析也表明，预测FEV1%和预测TLCO%是动脉血氧分压<7.3 kPa的最佳预测指标。我们得出结论，在稳定COPD患者中，没有肺功能变量与动脉血氧分压具有良好的相关性。动脉血氧分压<7.3 kPa的最佳预测指标是预测FEV1%。虽然低FEV1对个体LTOT需求的预测能力较差，但动脉血氧分压<7.3 kPa仅在FEV1较低的患者中出现。较高的FEV1可用于排除受试者进行进一步的LTOT调查，并避免不必要的动脉采血。
