The value of forced expiratory volume in 1 s in screening subjects with stable COPD for PaO2 < 7·3 kPa qualifying for long-term oxygen therapy

Abstract

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.

NHANES III equations enhance early detection and mortality prediction of bronchiolitis obliterans syndrome after hematopoietic SCT

“…Although only nine patients required supplemental oxygen, limiting the ability to draw conclusions, there was a suggestion that FEV1% predicted calculated by NHANESIII correlated with a requirement for oxygen. Within the patients who required oxygen supplementation, using FEV1% predicted <40%, previously determined to be the best threshold for positive predictive value and specificity of oxygen requirements, 26 89% (8/9) of patients with FEV1 ≤40% by NHANESIII would be predicted to require supplemental oxygen as compared with 77% with FEV1≤40% by MGB.…”

“…The characterization of obstruction using the fifth percentile threshold (NHANES III) was also evaluated in a similar fashion using the same method. On the basis of sensitivity data, FEV1 of 40% 26 and 35% 21 predicted were used to predict oxygen requirement and mortality, respectively. The correlation between FEV1 and 2-min walk velocity was determined by Spearman rank correlation analysis, with | r | <0.30 being considered weak correlation.…”

Can pulse oximetry select patients for screening spirometry?

“…The measurement of arterial oxygen saturation may be an aid in the identification of these patients since arterial hypoxaemia in COPD occurs frequently and relatively early in the natural history of the disease. The PaO 2 in patients with COPD correlates with the forced expiratory volume in 1 s [6], and, in patients with asthma of varying severity hypoxaemia was related to the degree of obstruction [7]. The portability and 'easy to use' nature of pulse oximeters make them potentially attractive…”

Quality Indicators for the Care of Chronic Obstructive Pulmonary Disease in Vulnerable Elders

“…Long‐term oxygen therapy improves health‐related quality of life 54 . FEV 1 less than 50% predicted has a specificity of 91% and a negative predictive value of 96% for identifying patients with COPD with significant hypoxemia 55 . The role of evaluating oxygenation during sleep, exercise, or continuously during daily activities is unclear.…”