A retrospective study of two populations to test a simple rule for spirometry.

BACKGROUND: Chronic lung disease is common and often under-diagnosed. METHODS: To test a simple rule for conducting spirometry we reviewed spirograms from two populations, occupational medicine evaluations (OME) conducted by Saint Louis and Wake Forest Universities at 3 sites (n = 3260, mean age 64.14 years, 95 % CI 58.94-69.34, 97 % men) and conducted by Wake Forest University preop clinic (POC) at one site (n = 845, mean age 62.10 years, 95 % CI 50.46-73.74, 57 % men). This retrospective review of database information that the first author collected prospectively identified rates, types, sensitivity, specificity and positive and negative predictive value for lung function abnormalities and associated mortality rate found when conducting spirometry based on the 20/40 rule (≥20 years of smoking in those aged ≥ 40 years) in the OME population. To determine the reproducibility of the 20/40 rule for conducting spirometry, the rule was applied to the POC population. RESULTS: A lung function abnormality was found in 74 % of the OME population and 67 % of the POC population. Sensitivity of the rule was 85 % for an obstructive pattern and 77 % for any abnormality on spirometry. Positive and negative predictive values of the rule for a spirometric abnormality were 74 and 55 %, respectively. Patients with an obstructive pattern were at greater risk of coronary heart disease (odds ratio (OR) 1.39 [confidence interval (CI) 1.00-1.93] vs. normal) and death (hazard ratio (HR) 1.53, 95 % CI 1.20-1.84) than subjects with normal spirometry. Restricted spirometry patterns were also associated with greater risk of coronary disease (odds ratio (OR) 1.7 [CI 1.23-2.35]) and death (Hazard ratio 1.40, 95 % CI 1.08-1.72). CONCLUSIONS: Smokers (≥ 20 pack years) age ≥ 40 years are at an increased risk for lung function abnormalities and those abnormalities are associated with greater presence of coronary heart disease and increased all-cause mortality. Use of the 20/40 rule could provide a simple method to enhance selection of candidates for spirometry evaluation in the primary care setting.

Real-world diffusing capacity simulation data: how well do they fit current European Respiratory Society/American Thoracic Society acceptability criteria?

ERS/ATS D LCO standards recommend acceptability ranges for weekly D LCO simulation testing performed with a 3-L syringe. On some devices, the ERS/ATS limits may exceed or not fit a 3-sd range, in which case, simulation ranges based on 3 sd may be appropriate. https://bit.ly/3Z0YoZL.

The Role of Pulmonary Function Testing in the Diagnosis and Management of COPD.

Pulmonary function testing (PFT) has a long and rich history in the definition, diagnosis, and management of COPD. For decades, spirometry has been regarded as the standard for diagnosing COPD; however, numerous studies have shown that COPD symptoms, pathology, and associated poor outcomes can occur, despite normal spirometry. Diffusing capacity and imaging studies have called into question the need for spirometry to put the "O" (obstruction) in COPD. The role of exercise testing and the ability of PFTs to phenotype COPD are reviewed. Although PFTs play an important role in diagnosis, treatment decisions are primarily determined by symptom intensity and exacerbation history. Although a seminal study positioned FEV1 as the primary predictor of survival, numerous studies have shown that tests other than spirometry are superior predictors of mortality. In years past, using spirometry to screen for COPD was promulgated; however, this only seems appropriate for individuals who are symptomatic and at risk for developing COPD.

What is the clinical value of lung volumes?

Lung volumes are considered part of a complete pulmonary function test, but their value for enhancing clinical decision making is unknown. Unlike spirometry and diffusing capacity of the lung for carbon monoxide (D(LCO)), which do contribute to confirming or excluding a diagnosis, there are few clear indications when lung volumes are discriminatory. Confirming "restriction" when vital capacity (VC) or FVC is reduced is perhaps the most important. A restrictive pattern can have many etiologies, and clinicians often use VC or FVC as a primary index of lung volume. This makes "physiologic" sense because, in healthy subjects, and in patients with true restriction, VC comprises most of the total lung capacity (TLC). Mixed obstruction-restriction and the nonspecific pattern (ie, reduced FVC and FEV(1), normal FEV(1)/FVC and TLC) require measuring TLC to confirm the underlying physiology. In obesity, VC and TLC may remain within normal limits, but functional residual capacity (FRC) can exponentially decrease. Increased lung volumes, particularly residual volume (RV), are commonly observed in airway obstruction. TLC may be normal, but is frequently increased in the late stages of COPD. Hyperinflation and air-trapping are terms commonly used to reflect these changes, but are not well standardized. The variability of lung volumes related to degree of obstruction suggests that measuring gas-trapping may be needed to monitor therapy. Changes in inspiratory capacity, RV, or FRC may be important gauges of response to bronchodilators or other hyperinflation-reducing therapies. How lung volumes are measured may be important, especially in patients who have moderate or severe airway obstruction. Body plethysmography is often considered more accurate than gas dilution methods in the presence of obstruction. However, the differences between techniques are not completely understood. Newer approaches such as computed tomography, although not suitable for routine testing, may help to delineate the true underlying physiology.

Pulmonary function testing.

Pulmonary function testing is often considered the basis for diagnosis in many categories of pulmonary disease. Although most of the testing methodologies are well established and widely employed, there are still many questions regarding how tests should be performed, how to ensure that reliable data are produced, what reference values and rules should be used, and how pulmonary function tests (PFTs) should be interpreted to best support clinical decision making. This conference was organized around a set of questions aimed at many of these issues. Each presenter was asked to address a specific topic regarding what tests should be done, how those test should be performed to answer a particular clinical question, and to relate test results to an accurate diagnosis and appropriate treatment of the patient. These topics included testing of adults and children, with concentration on important disease entities such as COPD, asthma, and unexplained dyspnea. Special emphasis was given to discussing reference values, lower limits of normal, interpretive strategies to optimize disease classification, and those factors directly affecting data quality. Established techniques for spirometry, lung volumes, diffusing capacity, exercise testing, and bronchial challenges were compared and contrasted with new technologies, and with technologies that might be part of pulmonary function laboratories in the near future.

Respiratory care year in review 2010: part 1. asthma, COPD, pulmonary function testing, ventilator-associated pneumonia.

The purpose of this paper is to review the recent literature related to asthma, COPD, pulmonary function testing, and ventilator-associated pneumonia. Topics covered related to asthma include genetics and epigenetics; exposures; viruses; diet, obesity and exercise; exhaled nitric oxide; and drug therapy (ß agonists, macrolides, tiotropium and monteleukast). Topics covered related to COPD include childhood disadvantage factors and COPD; vitamin D deficiency and COPD; ß-blockers and COPD; corticosteroid therapy during COPD exacerbations; oxygen administration during pre-hospital transport of patients with COPD exacerbation; and prognosis of patients admitted to the hospital for COPD exacerbation. Topics related to pulmonary function testing include methods and techniques; predicted values; natural history, pulmonary function in health and disease; and the COPD controversy. Finally, the paper includes the following topics related to ventilator-associated pneumonia: the tube, the intubation route, and the cuff; mechanical ventilation; the bundle; and cost. These topics were chosen and reviewed in a manner that is most likely to have interest to the readers of Respiratory Care.

Multi-wavelength pulse oximeter is not suitable for adjusting D(LCO) measurements.

BACKGROUND: Diffusing capacity of the lung for carbon monoxide (D(LCO)) can be affected by abnormal hemoglobin (Hb) or carboxyhemoglobin (COHb) levels. Predicted D(LCO) can be adjusted to reflect abnormal Hb or COHb levels. Until recently, blood sampling was required to determine Hb and COHb levels, but a new pulse oximeter, the Masimo RAD-57, can measure Hb and COHb noninvasively. We hypothesized that there would be no significant difference between the invasive and noninvasive Hb and COHb measurements for adjusting D(LCO). METHODS: In patients referred to our university hospital for D(LCO) testing, we simultaneously took arterial blood gas samples and measured Hb and COHb with the RAD-57 (SpHb and SpCOHb, respectively). We analyzed the paired values and the Hb-adjusted and COHb-adjusted predicted D(LCO) values with t tests and Bland-Altman plots. We compared the differences in predicted D(LCO) to a clinical threshold of 3 mL/min/mm Hg. RESULTS: SpHb differed from Hb measured via arterial blood analysis (12.1 ± 2.4 g/dL vs 13.3 ± 2.1 g/dL, P < .001). SpCOHb did not differ significantly from COHb (ie, measured via arterial blood analysis) (2.1 ± 4.0 vs 2.5 ± 2.3, P = .25), but there was wide variability. There were small but statistically significant differences in the adjusted predicted D(LCO), depending on whether blood or pulse oximetry values were used. Predicted D(LCO) adjusted for both Hb and COHb was 22.5 ± 4.8 mL/min/mm Hg measured with the RAD-57 and 23.5 ± 4.5 mL/min/mm Hg via arterial blood analysis (P < .001). The limits of agreement for pulse oximetry adjusted D(LCO) exceeded the clinical threshold of 3 mL/min/mm Hg for Hb adjustments and combined Hb + COHb. Predicted D(LCO) values differed by > 3 mL/min/mm Hg in 17% of patients. CONCLUSIONS: Pulse oximetry may be of limited usefulness for adjusting either predicted or measured D(LCO) values, but might be useful to screen patients for invasive testing, particularly if the D(LCO) is close to the lower limit of normal.

Weight-based reference equations for the 6-min walk test can be misleading in obese patients.

Weight-based reference equations for the 6-min walk test can produce normal results despite poor performance. Using ideal body weight- or non-weight-based reference equations for the 6-min walk test may produce more clinically meaningful results. https://bit.ly/2wE9Sdn.

Exercise-Induced Oxygen Desaturation during the 6-Minute Walk Test.

The 6-minute walk test (6MWT) is not intended to document oxygen (O2) desaturation during exertion but is often used for this purpose. Because of this, it only has modest reproducibility in determining the need for ambulatory O2 therapy in patients with cardiopulmonary disease. The diagnostic and prognostic value of detecting exertional O2 desaturation is still unknown. The aims of this study were to estimate the prevalence of O2 desaturation during a 6MWT based on pulse oximetry measurements at the beginning and end of a 6MWT in a clinical population of patients with suspected cardiopulmonary disease and to determine whether the pulmonary function test (PFT) can predict exercise-induced desaturation during a 6MWT. This retrospective cohort study reviewed the results of the 6MWT and the PFT (i.e., spirometry, lung volumes, and diffusion capacity) of all patients who were evaluated for suspected cardiopulmonary disease at an academic medical center during a 5-year study period. The patients were categorized into three groups based on the change in O2 saturation by pulse oximetry (SpO2) from start to end of the 6MWT: (1) SpO2 decreased by ≥3%; (2) SpO2 unchanged (-2 ≤ Δ ≤ 0%); and (3) SpO2 increased by ≥1%. Demographic, anthropometric, and lung function measurements were analyzed to determine which factors predicted O2 desaturation during the 6MWT. Of the 319 patients who underwent the 6MWT and the PFT from November 2005 until December 2010 (mean age = 54 ± 0.78 years, 63% women, 58% Whites, body mass index = 29.63 ± 8.10 kg/m2), 113 (35%) had a decreased SpO2, 146 (46%) had no change, and 60 (19%) had an increased SpO2 from the start to end of test. Our bivariate analysis found age, spirometric measures, and diffusion capacity for carbon monoxide (DLCO) had statistically significant inverse associations with the SpO2 change category (p < 0.001). Both a 3% and 4% drop in SpO2 during the 6MWT were statistically significantly associated with an older age, a higher prevalence of obstruction, and reduced forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, DLCO and 6-minute walk distance (6MWD). Multivariable logistic regression analyses revealed that only DLCO was a significant independent predictor of the change in SpO2 and a ≥ 4% O2 desaturation during a 6MWT. Receiver operating curve analysis indicates DLCO cut-off of 45% is 82% sensitive and 40% specific in identifying ≥4% O2 desaturators, with an area under the curve of 0.788 ± 0.039 (p < 0.001). The prevalence of a ≥ 3% oxygen desaturation via pulse oximetry during a 6MWT in our clinical population of patients with suspected cardiopulmonary disease was 35%. Although age, spirometric lung volumes, and DLCO had statistically significant unadjusted inverse associations with the change in SpO2 during a 6MWT, the DLCO is the only significant independent predictor of both the magnitude of the change in SpO2 and the occurrence of O2 desaturation of at least 4%, respectively, during the test. Clinical Implications: A DLCO cut-off of 45% may be useful in identifying patients at risk for exertional hypoxemia during a 6MWT.

Pulmonary Function Reference Equations: A Brief History to Explain All the Confusion.

Predicted values for pulmonary function tests differ significantly from the reference values used for many other diagnostic tests. Historically, simple equations using age, height, and sex were used to "predict" normal lung function. However, these multiple factors interact in complex ways to determine what the expected lung function values are in healthy subjects. Healthy individuals exhibit a wide range of variability for most pulmonary function variables, and this variability is not consistent across all age ranges. Recent analysis of large groups of healthy subjects has allowed the development of sophisticated prediction models that take into account not only variability but also skew that occurs as the lungs develop and mature. These modern reference equations provide uninterrupted expected values from early childhood, through adolescence and adulthood, and extending into the ninth decade. Modern equations use upper and lower limits of normal to offer a statistically robust means of defining who is within normal limits. Despite these advances, interpretation of pulmonary function test results has not been highly standardized, largely because interpretation depends on the reference equations used and, more importantly, how they are applied. This review discusses the strengths and limitations of using reference equations to interpret pulmonary function data in the context of research and clinical practice.

Should spirometer quality control be treated like other laboratory devices?

The ATS/ERS spirometer calibration standards may not be adequate http://ow.ly/Pqdq30nwAmb.

Office Spirometry in Primary Care for the Diagnosis and Management of COPD: National Lung Health Education Program Update.

The use of office spirometry was recommended by the National Lung Health Education Program (NLHEP) consensus conference in 1999 for detection and management of COPD. Since that time, spirometry utilization has increased, but its role in the diagnosis of COPD is still evolving. This update reviews the role of spirometry for screening and case finding in COPD as well as for asthma. Spirometry has been used for disease management in patients with airway obstruction, with varying results. The diagnostic criteria for COPD using spirometry have also evolved in the past 17 years, with differences arising between the Global Initiative for Chronic Obstructive Lung Disease and NLHEP recommendations. More sophisticated spirometers as well as new reference equations are widely available. Standardization guidelines from the American Thoracic Society/European Respiratory Society published in 2005 provide a robust framework for performing and interpreting spirometry, but clinicians still need hands-on training and meaningful feedback to perform high-quality spirometry in the office setting.

Bronchodilator Response in FVC Is Larger and More Relevant Than in FEV1 in Severe Airflow Obstruction.

BACKGROUND: Recommendations on interpreting tests of bronchodilator responsiveness (BDR) are conflicting. We investigated the dependence of BDR criteria on sex, age, height, ethnicity, and severity of respiratory impairment. METHODS: BDR test data were available from clinical patients in the Netherlands, New Zealand, and the United States (n = 15,278; female subjects, 51.7%) and from surveys in Canada, Norway, and five Latin-American countries (n = 16,250; female subjects, 54.7%). BDR calculated according to FEV1, FVC, and FEV1/FVC was expressed as absolute change, a percentage of the baseline level (% baseline), a percentage of the predicted value (% predicted), and z score. RESULTS: Change (Δ) in FEV1 and FVC, in milliliters, was unrelated to the baseline value but was biased toward age, height, sex, and level of airways obstruction; ΔFEV1 was significantly lower in African Americans. In 1,106 subjects with low FEV1 (200-1,621 mL) the FEV1 increased by 12% to 44.7% relative to baseline but < 200 mL. Expressing BDR as a percentage of the predicted value or as a z score attenuated the bias and made the 200-mL criterion redundant, but reduced positive responses by half. ΔFEV1 % baseline increased with the level of airflow obstruction but decreased with severe obstruction when expressed as z scores or % predicted; ΔFVC, however expressed, increased with the level of airflow obstruction. CONCLUSIONS: Expressing FEV1 responsiveness as % baseline spuriously suggests that responsiveness increases with the severity of respiratory impairment. Expressing change in FEV1 or FVC as % predicted or as z scores eliminates this artifact and renders the required 200-mL minimum increase redundant. In severe airways obstruction ΔFVC should be critically evaluated as an index of clinically important relief of hyperinflation, with implications for bronchodilator drug trials.

Residual Volume and Total Lung Capacity to Assess Reversibility in Obstructive Lung Disease.

BACKGROUND: Reversibility of obstructive lung disease is traditionally defined by changes in FEV1 or FVC in response to bronchodilators. These may not fully reflect changes due to a reduction in hyperinflation or air-trapping, which have important clinical implications. To date, only a handful of studies have examined bronchodilators' effect on lung volumes. The authors sought to better characterize the response of residual volume and total lung capacity to bronchodilators. METHODS: Responsiveness of residual volume and total lung capacity to bronchodilators was assessed with a retrospective analysis of pulmonary function tests of 965 subjects with obstructive lung disease as defined by the lower limit of normal based on National Health and Nutritional Examination Survey III prediction equations. RESULTS: A statistically significant number of subjects demonstrated response to bronchodilators in their residual volume independent of response defined by FEV1 or FVC, the American Thoracic Society and European Respiratory Society criteria. Reduced residual volume weakly correlated with response to FEV1 and to FVC. No statistically significant correlation was found between total lung capacity and either FEV1 or FVC. CONCLUSIONS: A significant number of subjects classified as being nonresponsive based on spirometry have reversible residual volumes. Subjects whose residual volumes improve in response to bronchodilators represent an important subgroup of those with obstructive lung disease. The identification of this subgroup better characterizes the heterogeneity of obstructive lung disease. The clinical importance of these findings is unclear but warrants further study.

Aerosol Use in the Pulmonary Function Lab.

Aerosolized medications are frequently used in the pulmonary function laboratory. The 2 most common implementations are bronchodilators and bronchial challenge agents. Bronchodilator administration is not well standardized, largely because of the various methods of delivery available for clinical practice. Metered-dose inhalers used with spacer devices are the most common route for bronchodilator administration, but many laboratories use small-volume nebulizers. Interpretation of pre- and post-bronchodilator studies is confounded by the definitions of airway obstruction and bronchodilator responsiveness. Protocols for administering bronchial challenge aerosols (methacholine, mannitol, hypertonic saline) are well defined but are susceptible to some of the same problems that limit comparison of bronchodilator techniques. Bronchial challenges with inhaled aerosols are influenced not only by the delivery device but by the patient's breathing pattern, particularly in protocols that include deep inspiratory efforts.