Quality control in the pulmonary function laboratory

Quality control and proficiency testing are well recognized as means for evaluating equipment accuracy and technical proficiency use of spirometry in physicians' offices, clinics, and industry has brought attention to the need for standardization of calibration and testing techniques in pulmonary function testing. Minimum specifications for equipment accuracy provide the basis for consistency of interlaboratory measurements, and familiarity with operation, calibration, and maintenance procedures enhances personnel proficiency.     

A spirometry-based algorithm to direct lung function testing in the pulmonary function laboratory

OBJECTIVE: To design a spirometry-based algorithm to predict pulmonary restrictive impairment and reduce the number of patients undergoing unnecessary lung volume testing. DESIGN: Two prospective studies of 259 consecutive patients and 265 consecutive patients used to derive and validate the algorithm, respectively. SETTING: A pulmonary function laboratory of a tertiary care hospital. PATIENTS: Consecutive adults referred to the laboratory for lung volume measurements and spirometry. MEASUREMENTS: The sensitivity of the algorithm for predicting pulmonary restriction and the cost savings associated with its use. RESULTS: Total lung capacity correlated strongly with FVC (r = 0.66) and showed an inverse correlation with the FEV(1)/FVC ratio (r = - 0.41). According to the algorithm, only patients with an FVC < 85% of predicted and an FEV(1)/FVC ratio >or= 55% required lung volume measurements following spirometry. The algorithm had a high sensitivity for predicting restriction and a high negative predictive value (NPV) for excluding restriction (sensitivity, 96%; NPV, 98%). The diagnostic properties of the algorithm were reproducible in the validation study. Application of the algorithm would eliminate the need for lung volume testing in 48 to 49% of patients referred to the pulmonary function test (PFT) laboratory, reducing costs by 33%. CONCLUSIONS: A spirometry-based algorithm accurately excludes pulmonary restriction and reduces unnecessary lung volume testing in the PFT laboratory almost in half.     

A comparison of spirometry in general practice and a pulmonary function laboratory.

AIMS:: To compare the results of spirometry testing in primary care with those obtained at a pulmonary function laboratory and to explore whether differences were due to technique or equipment. METHODS:: Patients on the waiting list for spirometry in six participating practices had the test performed in their own practice and at the pulmonary function laboratory (PFL). RESULTS:: A total of 45 patients had spirometry performed at both locations. Practice nurses underestimated FEV(1) and FVC. The mean difference in FEV(1) was 0.109litres (6.69%, 95% CI 2.88, 9.51) compared with a bellows spirometer, and 0.07litres (6.2% 95% CI 0.89, 8.25) when the same type of spirometer was used. The mean difference in FVC was 0.413litres (15.0% 95% CI 9.3, 20.6) when compared with bellows, and 0.267litres (10.2% 95% CI 4.1, 16.2) when the same type of spirometer was used. All differences were statistically significant (p<0.05, paired t test). Agreement on categorization of COPD was moderate (Kappa 0.46) with practice nurses overestimating severity. Compared to PFL categorisation for the presence or absence of COPD using bellows spirometers, the sensitivity of practice nurse spirometry was 0.93 (95% CI: 0.76, 0.99) and specificity 0.65 (95% CI: 0.38, 0.86). CONCLUSION:: Spirometry results obtained by practice nurses were lower than those obtained in a PFL, leading to over-diagnosis of COPD severity.     

The role of pulmonary function testing in pulmonary fibrosis

Interstitial lung diseases are characterized by disruption of the distal pulmonary parenchyma. The clinical history manifestations, cough and dyspnea, and physical exam manifestations, inspiratory crackles, are nonspecific. Pulmonary function testing aids in the evaluation and management of patients with interstitial lung disease although the pattern of abnormality is nonspecific. Pulmonary function testing can provide an estimate of histologic severity but not a definitive quantification of histologic fibrosis or inflammation. Pulmonary function tests can provide a baseline estimation of prognosis and be used to monitor disease progression or response to therapy. The forced vital capacity and diffusion capacity are the most valuable serial measurements, but further data are required to examine composite scoring and exercise gas exchange.     

Hand carried echocardiography screening for LV systolic dysfunction in a pulmonary function laboratory.

AIMS: Dyspnea is a common indication for pulmonary evaluation but also a common symptom in heart failure. Identification of dyspneic patients with significant LV systolic dysfunction is critical because of high morbidity of untreated heart failure. We sought to determine whether screening patients referred for pulmonary function testing (PFT) using a hand carried ultrasound (HCU) device could identify LV systolic dysfunction. METHODS: Forty-nine subjects were recruited from a pulmonary function lab to undergo a brief echocardiographic examination by an internist using a HCU device. All subjects also received an examination with a full-featured echocardiogram machine as a gold standard. RESULTS: All subjects with normal PFT had normal LV systolic function. Among subjects with abnormal PFT, 6 (15%) had LV systolic dysfunction and the remainder had normal LV systolic function. No subjects with LV systolic dysfunction by full-featured echocardiograms were missed by the HCU (sensitivity 100%, specificity 95%, negative predictive value 100%, positive predictive value 75%). CONCLUSIONS: LV systolic dysfunction is prevalent among patients with pulmonary disease and can be accurately screened for by a physician using a hand carried ultrasound device with subsequent confirmation with complete echocardiography.     

Advances in pulmonary laboratory testing

This review examines emerging technologies that are of potential use in the routine clinical pulmonary laboratory. These technologies include the following: the measurement of exercise tidal flow-volume (FV) loops plotted within the maximal FV envelope for assessment of ventilatory constraint during exercise; the use of negative expiratory pressures to asses expiratory flow limitation in various populations and under various conditions; the potential use of expired nitric oxide for assessing airway inflammation; and the use of forced oscillation for assessment of airway resistance. These methodologies have been used extensively in the research setting and are gaining increasing popularity and clinical application due to the availability of commercially available, simplified, and automated systems. An overview of each technique, its potential advantages and limitations will be discussed, along with suggestions for further investigation that is considered necessary prior to extensive clinical use.     

Occupational inhalant exposure and respiratory disorders among never-smokers referred to a hospital pulmonary function laboratory

BACKGROUND: Multiple reports have described associations between occupational inhalant exposure and lung disease. Previous occupational lung disease investigations have studied populations consisting of both smokers and nonsmokers. Smoking complicates interpretation of toxicant exposure-response relationships. The objective of this study was to determine whether, among never-smokers, occupational exposure to gases, dusts, or fumes is associated with a history of respiratory disorders and pulmonary function test defined obstructive lung disease. METHODS: We performed a retrospective analysis of 517 never-smoker patients who underwent pulmonary function testing in our clinical laboratory between 1986 and 1999. We calculated the relative risks of developing adverse respiratory health outcomes given a history of exposure to occupational inhalants. RESULTS: Compared with persons with a negative occupational exposure history, exposed persons had an increased risk of reporting a history of bronchitis [relative risk (RR), 1.59; 95% confidence interval (CI), 1.20-2.12], recurrent lung infections (RR, 2.09; 95% CI, 1.14-3.82), and bronchodilator use (RR, 1.61; 95% CI, 1.26-2.06). There was also a statistically significant association between a history of inhalant exposure and the finding of an obstructive ventilatory defect on pulmonary function testing (RR, 1.79; 95% CI, 1.12-2.85). A history of inhalant exposure was not associated with self-reported asthma (RR, 1.08; 95% CI, 0.83-1.41). The population attributable risk estimates for respiratory disorders due to inhalant exposure were: bronchitis, 23.6%; recurrent lung infection, 36.3%; bronchodilator use, 24.3%; and obstructive lung disease, 29.6%. CONCLUSIONS: Occupational inhalant exposure is a strong risk factor for lung disease in this population of never smokers. A significant burden of respiratory disease in this population may be attributable to occupational inhalant exposure.     

侵袭性肺曲霉病实验室诊断现状

目前,随着免疫受损人群的逐渐上升,侵袭性肺曲霉病(IPA)已日渐成为严重免疫受损者,如接受器官移植、皮质类固醇激素的长期应用、肿瘤化疗或患有慢性粒细胞减少症、白血病、HIV感染及其他急危重病的患者死亡的主要肺部感染性疾病之一。而IPA的确诊需综合考虑患者临床表现、免疫状态、职业史等及各项实验诊断方法检测等。由于传统检查手段的局限性使IPA诊断困难,容易漏诊误诊,导致治疗不及时或过度治疗,增加了IPA的病死率。因此早期快速、准确诊断是治疗IPA的关键,为此,该文综述近年来国内外文献资料关于IPA早期诊断的相关研究成果,为提高临床诊断IPA感染的水平提供一定的参考。     

The effect of pollutional haze on pulmonary function

Detrimental health effects of atmospheric exposure to ambient particulate matter (PM) have been investigated in numerous studies. Exposure to pollutional haze, the carrier of air pollutants such as PM and nitrogen dioxide (NO₂) has been linked to lung and cardiovascular disease, resulting increases in both hospital admissions and mortality. This review focuses on the constituents of pollutional haze and its effects on pulmonary function. The article presents the available information and seeks to correlate pollutional haze and pulmonary function.     

Determination of bronchodilation in the clinical pulmonary function laboratory. Role of changes in static lung volumes

Improved airway resistance following bronchodilator inhalation is not always accompanied by improvement in forced expiratory flow. We studied 241 patients with airways obstruction to learn whether changes in static lung volumes (vital capacity and function residual capacity measured by body plethysmography [FRCB]) would reveal bronchodilation not demonstrated by expiratory flow rates (the ratio of forced vital capacity at one second to the total forced vital capacity [FEV1/FVC]), and the forced expiratory flow for the midportion of the forced vital capacity (FEF25--75%). A significant fall in Raw occurred in 129 patients, 46 of whom had a significant increase in vital capacity (mean of + 465 ml +/- 43, P less than 0.001) and a fall in FRCB (mean of -763 ml +/- 78 P less than 0.001) with no change in FEV1/FVC% of FEF25--75%. We interpret these data to indicate that improvement in static lung volumes can reflect bronchodilation in the absence of improved expiratory flow.     

Comparison of FEV6 and FVC for detection of airway obstruction in a community hospital pulmonary function laboratory

The National Lung Health Education Program recommends that primary care providers perform spirometry tests on cigarette smoking patients 45 years or older in order to detect airways obstruction and aid smoking cessation efforts [Ferguson GT, Enright Pl, Buist AS, et al. Office spirometry for lung health assessment in adults: a consensus statement from the national lung education program. Chest 2000; 117: 1146-61]. An abbreviated forced expiratory maneuver that requires exhalation for 6s (FEV6) has recently been proposed as a substitute for forced vital capacity (FVC) to facilitate performance of such spirometry. We set out to assess the accuracy of diagnosis of obstruction and abnormal pulmonary function using FEV6 in comparison to FVC in a community hospital population. One hundred pulmonary function tests performed at a community hospital were randomly selected and retrospectively analyzed. Sixty-three of the 100 tests had satisfactory 6-s expiration and were subject to further analysis. We compared the spirometric interpretation using Morris predictive equations for FEV1/FVC and Hankison predictive equations for FEV1/FVC and FEV1/FEV6. The Hankison set of equations is the only published reference formulas for prediction of FEV6. We found that versus our Morris gold standard, Hankison based FEV1/FVC interpretation was 100% sensitive and 67% specific for the diagnosis of obstruction and 100% sensitive and 65% specific for the diagnosis of any abnormality. The Hankison based FEV1/FEV6 interpretation was 97% sensitive and 47% specific for diagnosing obstruction and 100% sensitive and 50% specific for identifying any abnormality versus the Morris FVC based gold standard. In conclusion, in our hospital based pulmonary function laboratory, FEV6 based interpretation has excellent sensitivity for detection of spirometric abnormalities. However, its moderate specificity may hinder its utility as a screening test. Further testing is necessary to determine its reliability in different patient populations with less highly trained operators.     

Validation of the smoking habits of a sample of the patient population seen in a pulmonary function laboratory

From a structured history of 32 current smokers seen in the pulmonary function laboratory of a community hospital, we determined the number of cigarettes they smoked in 24 h. We also asked them to estimate their cigarette butt lengths from a visual model and to collect all cigarette butts over the next 24 h and mail them to us. We counted the butts, individually measured their lengths, and compared these with their previous estimates in order to validate their claims. While in the laboratory, we determined the level of carboxyhemoglobin in the peripheral blood of each patient. Patients tended to estimate the numbers of cigarettes that they smoked in units of five. Light smokers returned more butts and heavy smokers returned fewer butts than the numbers they reported as usually smoking. All patients were able to precisely estimate the average length of their cigarette butts, and they left butts of consistent lengths. There was no association between the numbers of cigarettes smoked and the butt lengths. Carboxyhemoglobin levels were positively associated with the numbers of cigarettes smoked in 24 h and negatively associated with the butt length and the time elapsed since the last cigarette was smoked, but these were not associated with the amount of tar in the cigarettes or with the number of years the person had smoked.     

Pediatric pulmonary function testing

Pulmonary function testing is an essential component in the diagnosis and monitoring of the pediatric asthmatic. Very young children are capable of performing spirometry, lung Volumes, airway mechanics, and other testing. Obtaining valid test results in children is dependent on multiple factors including equipment selection, environment, technologist training and competence level, and the child's developmental age. Multiple test methods are discussed to assess the degree of airway obstruction and reversibility.