Pulmonary Function Laboratory Research Articles

A pilot comparison of helium dilution and plethysmographic lung volumes to assess the impact of a long-acting bronchodilator on lung hyperinflation in COPD

Background Currently, two methods for measuring TLC, RV, and FRC are used in clinical pulmonary function laboratories: body plethysmography and helium dilution. However, these methods are not interchangeable. In moderate-to-severe airflow obstruction, dilution method tends to underestimate and body plethysmography tends to overestimate RV. Purpose In 21 patients suffering from COPD (basal FEV 1: 56.69 ± 13.64), we investigated whether the two methods of measuring FRC and RV could respond differently to a 2-week treatment with tiotropium 18 μg/day. Main results Tiotropium induced a significant increase in FEV 1 and FVC but not in IC. At baseline, FRC pleth, RV pleth and TLC pleth were higher than FRC He, RV He and TLC He. At the end of the study FRC pleth, RV pleth and TLC pleth decreased and FRC He, RV He and TLC He increased but only changes in FRC pleth and RV pleth were statistically significant. Conclusion The use of body plethysmography seems to be more appropriate in clinical trials aimed at assessing the impact of a therapeutic procedure in patients with COPD and lung hyperinflation.

Matching donor to recipient in lung transplantation: How much does size matter?

The impact of size matching between donor and recipient is unclear in lung transplantation. Therefore, we determined the relation of donor lung size to 1) posttransplant survival and 2) pulmonary function as measured by forced expiratory volume in 1 second. From 1990 to 2006, 469 adults underwent lung transplantation with lungs from donors aged 7 to 70 years. Donor and recipient total lung capacities were calculated using established formulae (predicted total lung capacity), and actual recipient lung size was measured in the pulmonary function laboratory. Disparity between donor and recipient lung size was expressed as a ratio of donor predicted total lung capacity to recipient predicted total lung capacity-the predicted total lung capacity ratio-and predicted donor total lung capacity to actual recipient total lung capacity-the actual total lung capacity ratio. Survival was measured by multiphase hazard methodology and repeated measures of National Health and Nutrition Examination Survey-normalized forced expiratory volume in 1 second analyzed by temporal decomposition. Predicted total lung capacity ratio and actual total lung capacity ratio ranged widely, from 0.55 to 1.59 and 0.52 to 4.20, respectively. Overall survival was unaffected by predicted total lung capacity ratio (P = .3) or actual total lung capacity ratio (P = .5). Patients with emphysema and an actual total lung capacity ratio of 0.67 or less or 1.03 or greater had higher predicted mortality (P = .01). During the first posttransplant year, forced expiratory volume in 1 second increased and then gradually declined. Predicted total lung capacity ratio and actual total lung capacity ratio had a small impact on forced expiratory volume in 1 second, primarily in the late phase after transplant in a disease-specific manner. Size matching between donor and recipient using predicted total lung capacity ratio and actual total lung capacity ratio is an effective technique. Wide discrepancies in lung sizing do not affect overall posttransplant survival or pulmonary function. Therefore, a greater degree of lung size mismatch can likely be accepted, thereby improving patients' odds of undergoing transplantation.

Pulmonary Function Testing in the Evaluation of Patients with Allergic and Immunologic Disorders

The Pulmonary Function Laboratory plays an important role in the evaluation of patients with respiratory diseases, including those that have diseases that occur on an allergic or immunologic basis. The American Thoracic Society (ATS) and European Respiratory Society (ERS) created a task force to standardize lung function testing and published a series of position papers that serve as the most current resource available on this subject [1–5]. Physicians performing pulmonary function studies should refer to these guidelines and use them as the standard methodology so as to be consistent with all laboratories in North America and Europe. This issue will cover the performance of spirometry, lung volume measurements, the determination of the diffusing capacity that is also called transfer factor or carbon monoxide uptake, bronchoprovocation challenge, and a provocative discussion of the problems in the interpretation of the results of the studies. Spirometry is a dynamic test that is best for measuring flow rates. The FEV1 is a volume that is exhaled in 1 s and thus is a flow rate. The FVC is a volume and not a flow rate and is dependent on the total expiratory time, especially in patients with airway obstruction. Spirometry is an effortdependent study, and it is necessary to have the patient blow out as hard and as fast as possible to get optimum results. Thus, the technician performing the test must be well trained. There are two types of spirometers. Volume displacement spirometers are those where air is expelled into the device and this moves a bellows or piston. This motion is measured and provides the values used in patient evaluation. Volume displacement spirometers have the advantage of maintaining their calibration from day to day and week to week, although they do need to be regularly calibrated and checked for air leaks. The disadvantages of volume displacement spirometers are that they tend to be bulky and have moving parts that can be damaged. Thus, they are difficult to use in field studies. The other type of spirometer is an electronic device that measures airflow using a pneumotachygraph and then electronically converting the result into the various measurements used. They have the advantage of being small, lightweight, and have no moving parts. Their disadvantage is that electronic drift can occur and any material collecting on the screen in the pneumotachygraph will alter the values. They require more frequent calibration checks. The newer models have been devised to minimize these problems. Electronic spirometers are well suited for field studies. It is important that a calibrating syringe be available to check the calibration of all spirometers. These are usually 3-l syringes. Lung volume measurements are essentially static procedures and are best for determining volumes. The two general methods employed are 1) gas dilution using an inert gas that does not cross the alveolar barrier such as helium or neon and, in the past, by nitrogen washout with collection of the expired gases and 2) thoracic gas volume that is determined by plethysmography or radiographic techniques. The gas dilution and nitrogen washout techniques are less accurate when there is poor distribution of the gas throughout the lung, as is seen in patients with chronic obstructive pulmonary disease and asthma. This is because the percentage of the inhaled marker gas varies from area to area in the lung and the sampled expired specimen is apt to underestimate the total lung capacity due to the overall uneven distribution of the tracer gas throughout the lung. Clinic Rev Allerg Immunol (2009) 37:135–136 DOI 10.1007/s12016-009-8124-3

Espirometría forzada en preescolares sanos bajo las recomendaciones de la ATS/ERS: estudio CANDELA

Introduction Reference values for spirometry in healthy preschool children have not yet been obtained in accordance with American Thoracic Society (ATS) and the European Respiratory Society (ERS) guidelines. The objective was to establish reference values for spirometry in healthy preschoolers under the ATS/ERS 2007 statement. Material and method Children of at least 2 and under 7 years of age were tested in 9 pediatric pulmonary function laboratories. The technicians were trained to apply a standardized protocol to perform spirometry. Results Valid spirometry results were obtained in 455 (81.54%) out of 558 children: 242 boys (53.2%) and 213 girls (46.8%). Ages were as follows: 31 at least 2 and under 3 years old; 96, at least 3 and under 4; 108, at least 4 and under 5; 122, at least 5 and under 6 years, and 98, at least 6 and under 7 years. Formulas were used to calculate the reference values for all the spirometry variables in preschoolers. Conclusions Spirometry is feasible in the majority of preschool children under the new guidelines. The availability of the reference values presented is an important step, both for the care of preschoolers and for further research on pulmonary function.

The Carbon Monoxide Diffusing Capacity: Clinical Implications, Coding, and Documentation

The test for the diffusing capacity of the lung for carbon monoxide (DLCO) has been available for nearly 100 years for research and clinical purposes. The single-breath method is used almost exclusively in the United States It has been available in clinical pulmonary function laboratories for > 50 years. DLCO has great value in evaluating patients with lung diseases. Guidelines to standardize DLCO have been published by the American Thoracic Society and European Respiratory Society to reduce the interlaboratory variability that has existed. One code, 94720, should be reported for the billing for DLCO. Another code, 94725, the membrane diffusing capacity, exists for the measurement of the membrane and blood components of the DLCO. Currently, no clinical indications exist for the use of the membrane diffusing capacity. The finding that the number of tests in the Medicare population coded with 94725 has increased by > 1,000% from 2000 to 2005 is quite surprising. This rate is 14-times higher than the rate of increase in the utilization of 94720 over the same period. The possible reasons for these increases are discussed, but the most likely explanation is the financial gain derived from coding 94725. It is proposed that coding and billing of 94725 be stopped until the clinical indications for membrane diffusing capacity have been established. Those who code and bill for 94725 must be prepared to justify the use of this code to Medicare and third-party payers.

Standardization of spirometry in assessment of responders following man‐made disasters: World Trade Center worker and volunteer medical screening program

Spirometry is the most commonly used pulmonary function test to screen individuals for suspected lung disease. It is also used for screening workers with exposures to agents associated with pulmonary diseases. Although the American Thoracic Society (ATS) provides guidelines for spirometers and spirometry techniques, many factors are not standardized, so that results from individual pulmonary function laboratories vary substantially. These differences can create substantial difficulties in using data pooled from multiple sites to understand health consequences of disasters that involve exposures to pulmonary toxins. This article describes the approach used to minimize these differences for a consortium of institutions who are providing medical monitoring examinations to World Trade Center (WTC) responders. The protocol improved upon the minimal ATS guidelines. Spirometric measurements were obtained before and after use of a bronchodilator. A fourth-generation spirometer was chosen that exceeded ATS spirometer accuracy standards. The accuracy was verified at the beginning of each day of testing. Technologists who performed the spirometry tests were centrally trained and certified and received regular reports on their performance. Reference values and normal ranges were obtained from the National Health and Nutrition Examination Survey (NHANES III) data set. A standardized interpretation flowchart was followed to reduce misclassification rates for airway obstruction and restriction. Patients with spirometric abnormalities were referred for more extensive diagnostic testing. More than 12,000 spirometry tests were performed during the first examination. The 20 spirometers used at the 6 participating institutions maintained accuracy within 3% for more than 4 years. Overall, more than 80% of the test sessions met ATS quality goals. Spirometry abnormality rates exceeded those obtained for adults who participated in the NHANES III survey. The program allowed standardization of the performance and interpretation of spirometry results across multiple institutions. This facilitated reliable and rapid diagnosis of lung disease in the large number of WTC responders screened. We recommend this approach for postdisaster pulmonary evaluations in other settings.

Assessment of Differential Lung Function by Electrical Impedance Tomography

To compare unilateral lung function estimated by 2 methods: electrical impedance tomography (EIT) and ventilation-perfusion lung scintigraphy. This prospective clinical study was carried out in the pulmonary function laboratory of a general hospital. Twenty patients diagnosed with lung cancer (17 men and 3 women, ranging in age from 25 to 77 years) who were candidates for lung resection underwent ventilation-perfusion lung scanning breathing a radioactive gas. Differential lung function was estimated based on images taken at 2 intercostal spaces in which ventilation and perfusion were represented by changes in bioelectrical impedance. Each lung's contribution to overall respiratory function was also calculated based on scintigraphy. The right lung contributed a mean (SD) of 54% (9%) of ventilation (range, 32%-71%) according to EIT. Scintigraphy similarly estimated the right lung's contribution to be 52% (10%) of total ventilation (range, 31%-80%) and 50% (9%) of perfusion (range, 37%-71%). The difference between the 2 estimates was not significant (t test), and the correlation coefficients between them were r=0.90 for ventilation and r=0.72 for perfusion (P< .05 in both cases). The analysis of agreement showed that the mean difference between the methods was 1.9% (95% confidence interval [CI], 10.5% to -6.8%) for ventilation and 3.4% (95% CI, 17.1% to -10.3%) for perfusion. EIT is able to estimate differential lung function as accurately as ventilation-perfusion scintigraphy.

Inspiratory muscle training in chronic obstructive pulmonary disease. Where are we?

We read with great interest the study by Battaglia et al.1 which assessed the effectiveness of a new volumetric exerciser for improving some respiratory function parameters in patients with COPD. The purpose of this letter is to comment on what we consider to be important about the effectiveness of inspiratory muscle training (IMT) for improving the strength and endurance of respiratory muscles. Various studies in recent years have assessed the effectiveness of IMT for improving the strength and endurance of respiratory muscles in patients with COPD. When Threshold IMT equipment was not yet available commercially, Smith et al.2 published the first meta-analysis on the effects of IMT on the strength and endurance of the respiratory muscles, and the exercise capacity and functional status of patients with COPD. Little evidence was found for clinical benefits from IMT in patients with COPD. The authors suggested that the benefits of this training were related to the generation of adequate pressures in the mouth, considering that most studies included in the meta-analysis used a flow device for loading. Ten years later, Lotters et al.3 in a new meta-analysis that included 15 randomized controlled studies, concluded that IMT had significant effects on both the strength and endurance of respiratory muscles, thus raising the possibility of benefits from IMT in these patients. In a recent editorial, and later in correspondence between McConnell et al. and Hart et al.4 the pros and cons of the effectiveness of IMT were debated. Polkey et al.5 in a very interesting editorial, presented the scientific opinion of his research group concerning the insufficient evidence, based on the isolated use of dependent tests for assessing the function of respiratory muscles, that was used to support the possible benefits of IMT. In this editorial, the authors discussed the article of Weiner et al.6 They reported that several points are still unclear in relation to the results of IMT. Hart et al.7 recently introduced a new technique for assessing respiratory muscle endurance. These authors observed that the noticeable improvements in strength and endurance that are normally reported after IMT programmes, seem to be more related to an alteration of respiratory pattern, rather than a real increase in endurance capacity of the respiratory muscles.4, 8 Curiously, Battaglia et al.1 after an intervention with a simple volumetric inspiratory exerciser, a device that stimulates volume without a target resistance, found an increase in maximal inspiratory pressure (MIP) of around 30% after 6 months of training. This result seems to corroborate the hypothesis that, in isolation, the dependent tests used to assess the strength of respiratory muscles (the MIP test being the most widely used) are insufficient for measuring the effects of IMT, thus supporting the results of Polkey et al.5 If a volumetric inspiratory exerciser device is used to train the respiratory muscles, it is expected that compliance of the rib cage will increase and muscle performance in the test will improve. The MIP test is a dependent test that is related to the compliance of the rib cage, and in turn to pulmonary volume. However, despite doubts in relation to IMT, Ramirez-Sarmiento et al.9 recently studied structural adaptations in the external intercostal muscle after 5 weeks of IMT in patients with COPD. This was the first, and as yet only, published study showing evidence for clinical and physiological effectiveness, and for structural adaptation of a respiratory muscle after IMT. Therefore, the following points remain obscure in relation to IMT: the techniques that should be used to assess the effects of IMT, given that the new technique proposed by Hart et al.7 is neither simple nor inexpensive to use on a daily basis in pulmonary function laboratories; the degree of improvement that should realistically be expected after IMT, given that the diaphragm of patients with COPD seems to be more active and more susceptible to fatigue than that of healthy subjects;10 and finally, can IMT be considered a valid alternative for improving functional capacity in patients with COPD?

Assurance et management de la qualité en EFR

Pulmonary function laboratories (PFT labs) have the duty to provide diagnostic examinations at the request of clinicians. They must guarantee the accuracy and safety of these examinations while responding to the requirements of both the clinicians and the patients. After reviewing the historical background to quality standards this article details the principles that have led from quality assurance (ISO 9000 standards: 1994) to quality management (ISO 9000 standards: 2000), as well as the principles that it is advisable to implement to obtain certification or accreditation. In order to obtain these formal recognitions a laboratory should be in a position to control all the procedures underlying these examinations and be able to set up a systematic range of preventative and corrective measures. These elements are the basis of a programme of quality assurance and management. This article outlines the approach of the pulmonary function laboratory of the Hospital Saint Antoine, Paris that is certified ISO 9001: V2000 and accredited ISO 17025 for blood gas measurements.

Benefits of a modified spirometry technique

To the Editors: We applaud the American Thoracic Society (ATS) and the European Respiratory Society for their continuing efforts to optimise pulmonary function testing practice through disseminating guidelines, such as the recent spirometry guidelines 1. In reviewing this document, we wish to point out a spirometry practice that, although mentioned (but not endorsed) in the guidelines, can, in our experience, substantially improve and streamline the performance of spirometry by pulmonary function laboratories 2. Specifically, we point out the benefits of a modified spirometry technique in which the expiratory effort is relaxed after the first 3 s of expiration. As evaluated and reported in a small, randomised, controlled, crossover trial of two expiratory techniques and …

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

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. 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. 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%). 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.

Methacholine Challenge Testing: Identifying Its Diagnostic Role, Testing, Coding, and Reimbursement

Methacholine challenge testing (MCT), also sometimes described as bronchoprovocation testing, is widely performed for both research and diagnostic purposes. MCT is clinically useful when the patient presents with a history of symptoms suggesting asthma, but spirometry findings are normal. Typically, MCT is performed in a pulmonary function laboratory, a clinic, or a physician's office. MCT requires time, effort, and understanding. Two standard testing regimes are identified along with proper coding and reimbursement methodologies.

The bronchoprotective effect of deep inspiration is flow rate dependent

Deep inspiration (DI) protects against methacholine-induced bronchoconstriction in healthy subjects. We hypothesized that this bronchoprotective effect of DI depends upon the inspiratory flow rate. Prospective, controlled study. Pulmonary function laboratory within a large tertiary medical center. Ten healthy nonsmokers without asthma or rhinitis. First, we performed a methacholine challenge in the absence of DI to determine the concentration sufficient to reduce FEV(1) by 20%. On two subsequent days, the challenge was repeated with the addition of either a fast or slow DI immediately before the threshold concentration of methacholine. We calculated the % reduction in FEV(1) and FVC from baseline. Mean % reduction in FEV(1) and FVC was significantly less with a fast DI than with no DI (20+/-3% vs. 34+/-4% for FEV(1), p=0.02; 12+/-3% vs. 23+/-3% for FVC, p=0.03); slow DIs did not significantly affect the methacholine-induced reduction in lung function. A fast DI is bronchoprotective while a slow DI is not. Elucidating the conditions that maximize or alternatively, eliminate bronchoprotection in healthy subjects may ultimately provide insight into the pathophysiology of asthma.

Determination of functional residual capacity by oxygen washin-washout: a validation study

To validate a new system for functional residual capacity (FRC) measurements using oxygen washin/washout in spontaneously breathing humans. The system (LUFU, Drägerwerk AG, Lübeck, Germany) consists of an unmodified EVITA 4 ventilator, a side-stream paramagnetic oxygen sensor and a dedicated software. Laboratory study and measurements in spontaneously breathing volunteers. Pulmonary function laboratory of a university hospital. 20 healthy and 15 lung diseased volunteers. FRC was measured by LUFU (LUFU-FRC) and by helium dilution (He-FRC); intra-thoracic gas volume (ITGV) was determined by body plethysmography. Each measurement cycle consisted of four independent LUFU-FRC determinations (step change of FiO(2) from 0.21 to 0.5 and back and from 0.21 to 1.0 and back), two helium-dilution runs and two body box measurements. Repeatability and agreement between methods were determined by comparing different measurements of one technique and by comparing different techniques among each other. Repeatability of LUFU-FRC was estimated by comparing washin to washout and the different FiO(2)steps. The difference of the means was 3.7% at the most. Agreement between methods resulted in the following differences (mean+/-standard deviation of differences) for healthy and lung-diseased volunteers, respectively: LUFU-FRC vs. He-FRC -0.40+/-0.50 L (0.02+/-0.95 L), LUFU-FRC vs. ITGV -0.43+/-0.54 L (-0.18+/-0.61 L) and He-FRC vs. ITGV -0.03+/-0.43 L (-0.20+/-0.98 L). LUFU is a non-invasive method for the determination of FRC that requires only minor additional equipment and no modification to the ventilator. It can be used in difficult conditions such as breathing patterns with variations from breath to breath. The results of this study show that LUFU is sufficiently reliable and repeatable to warrant its clinical application.

Determinants of Pulmonary Arterial Hypertension in Scleroderma

To define risk factors associated with pulmonary arterial hypertension (PAH) in a large cohort of patients with systemic sclerosis (SSc). SSc patients undergoing screening for PAH by means of Doppler echocardiography were identified and their charts were retrospectively reviewed. In all patients, we recorded systolic pulmonary artery pressure along with pulmonary function testing, clinical, and laboratory data. PAH was defined as right ventricular systolic pressure equal or greater than 40 mm Hg. Of 114 SSc patients with echocardiographic measurements, PAH was found in 33 (29%) patients. In a multiple logistic regression analysis, the presence of pulmonary fibrosis on thoracic computed tomography (OR 6.78, CI 1.54 to 29.9), forced vital capacity less than 80% predicted (OR 3.03, CI 1.1 to 8.35), and duration of Raynaud's phenomenon preceding the onset of skin changes for at least 3 years (OR 5.75, CI 1.9 to 17.41) were found to be independent predictors of PAH. Age, disease duration, disease subtype, or autoantibodies were not associated with PAH in our patients. The present analysis identified pulmonary fibrosis and Raynaud's phenomenon preceding SSc skin manifestations by at least 3 years as risk factors for PAH in our scleroderma cohort. Screening for PAH in these high-risk patients may detect PAH at an earlier stage and guide decisions on therapeutic interventions.

Measurement of Fraction of Exhaled Nitric Oxide With the Portable NIOX-MINO Monitor in Healthy Adult

Measurement of the fraction of exhaled nitric oxide (FENO) provides a noninvasive way to monitor asthma treatment in clinical practice. The aim of this study was to determine FENO reference values for measurements recorded with the portable NIOX MINO monitor in a group of healthy volunteers. We also assessed the association between values recorded by the portable monitor and the N-6008 chemiluminescence analyzer used in our pulmonary function laboratory. The FENO values obtained with the portable monitor were consistently higher than those recorded by the N-6008 analyzer; the cutoff value for the portable monitor was 34 ppb (mean + 2 SD). We detected a direct correlation (r=0.92) between the FENO measurements recorded by the 2 monitors (P=.001). The following equation expresses the relationship between measurements from the 2 devices: FENO(NIOX MINO) = 10 + [1.5 FENO(N-6008)]. We did not observe statistically significant correlations between FENO measurements and age, sex, body mass index, or spirometry.

CERTIFICATION OF CARBON MONOXIDE DIFFUSING CAPACITY MEASUREMENTS FOR CLINICAL TRIALS OF INHALED INSULIN.

Clinical trials of AIR® Inhaled Insulin (AIR® is a registered trademark of Alkermes, Inc) include serial measurements of carbon monoxide diffusing capacity (DLco) as one of several safety parameters. The measurements are performed in the United States and other countries, in widely different laboratory settings, using 12 different pulmonary function-testing (PFT) systems. To ensure quality, laboratories follow standard calibration and testing methods outlined by the American Thoracic Society (ATS). Before testing patients in a clinical trial, laboratories use a DLco simulator (Hans Rudolph, Kansas City, MO) to validate and monitor the accuracy of their DLco measurements. The DLco simulator delivers a known inspired volume and precise, known “exhaled” gas concentrations. When combined with the breath-hold time from the PFT device, exact “target” values for DLco can be calculated. Simulations with four different target values are introduced into each device by varying exhaled gas concentrations and inspired volumes. Differences between measured and target values for alveolar volume (VA), inspired volume, and gas concentrations of carbon monoxide and the tracer gas are then evaluated. A DLco device is certified to be functioning properly if measured volumes are within 3% of target and DLco measures are within 3.0 standard DLco units (mL CO/min/mm Hg) of calculated target values. After initial certification, simulation testing is done each week for 3 months and then biweekly for the remainder of the study. Equipment at 31 sites (24.8%) failed the initial DLco simulation testing. After correcting instrument issues or purchasing new equipment, 124 (99.2%) sites were confirmed to be measuring DLco accurately. A significant percentage of the DLco devices in clinical pulmonary function laboratory tests are likely to be malfunctioning. This study underscores the need to certify and monitor DLco test quality in clinical trials and clinical laboratories.

The Relationship Between FEV1 and Peak Expiratory Flow in Patients With Airways Obstruction Is Poor

Study objectives To evaluate the correlation between FEV1 and peak expiratory flow (PEF) values expressed as a percentage of their predicted value, and to assess factors influencing differences between the two measurements. Design Cross-sectional. Setting Pulmonary function laboratory at a tertiary-level teaching hospital in northern India. Participants A total of 6,167 adult patients showing obstructive pattern on spirometry over a 6-year period. Interventions None. Measurements and results There was considerable variability between percentage of predicted FEV1 (FEV1%) and percentage of predicted PEF (PEF%). Locally weighted least-square modeling revealed that PEF% overestimated FEV1% in patients with less severe obstruction and underestimated it in those with more severe obstruction. Using Bland-Altman analysis, PEF% underestimated FEV1% by a mean of only 0.7%; however, limits of agreement were wide (− 27.4 to + 28.8%), indicating that these two measurements cannot be used interchangeably. PEF% and FEV1% were > 5% apart in approximately three fourths and differed by > 10% in approximately one half of the patients. On multivariate analysis, discordance > 5% was significantly influenced by female gender (odds ratio, 1.26; 95% confidence interval [CI], 1.01 to 1.58) and increasing FEV1% (odds ratio, 1.09 for every 10% increase; 95% CI, 1.04 to 1.14) but not by height or age. Conclusions FEV1% and PEF% are not equivalent in many patients, especially women and those with less severe airflow limitation. Assumptions of parity between PEF% and FEV1% must be avoided. To evaluate the correlation between FEV1 and peak expiratory flow (PEF) values expressed as a percentage of their predicted value, and to assess factors influencing differences between the two measurements. Cross-sectional. Pulmonary function laboratory at a tertiary-level teaching hospital in northern India. A total of 6,167 adult patients showing obstructive pattern on spirometry over a 6-year period. None. There was considerable variability between percentage of predicted FEV1 (FEV1%) and percentage of predicted PEF (PEF%). Locally weighted least-square modeling revealed that PEF% overestimated FEV1% in patients with less severe obstruction and underestimated it in those with more severe obstruction. Using Bland-Altman analysis, PEF% underestimated FEV1% by a mean of only 0.7%; however, limits of agreement were wide (− 27.4 to + 28.8%), indicating that these two measurements cannot be used interchangeably. PEF% and FEV1% were > 5% apart in approximately three fourths and differed by > 10% in approximately one half of the patients. On multivariate analysis, discordance > 5% was significantly influenced by female gender (odds ratio, 1.26; 95% confidence interval [CI], 1.01 to 1.58) and increasing FEV1% (odds ratio, 1.09 for every 10% increase; 95% CI, 1.04 to 1.14) but not by height or age. FEV1% and PEF% are not equivalent in many patients, especially women and those with less severe airflow limitation. Assumptions of parity between PEF% and FEV1% must be avoided.

DLCO versus DLCO/VA as predictors of pulmonary gas exchange

The diffusing capacity of the lung is usually reported as both the diffusing capacity (DLCO) and the diffusing capacity divided by the alveolar volume (DLCO/VA). However, it is unclear which measure to use when interpreting pulmonary gas exchange. We therefore conducted this study to determine whether the DLCO or the DLCO/VA is a better predictor of oxygen desaturation with exercise. We retrospectively analyzed the pulmonary function records of all patients who had measurement of their diffusing capacity and 6-min walk oximetry in our university pulmonary function laboratory over a 2-year period. There were data available on 97 patients, most of who had interstitial lung disease and/or lung volume restriction. The median DLCO was 51% predicted and the median DLCO/VA was 64% predicted. The prevalence of exercise desaturation was 43%. The overall sensitivity and specificity as determined by the area under the receiver operator characteristic (ROC) curve was higher for DLCO than DLCO/VA, with an optimal cut-off of normal of 55% predicted. The positive predictive values were equally low for both measures, ranging from 50% to 70%. After adjustment for VA, there were no differences between the ROC curves or predictive values for DLCO and DLCO/VA. After adjusting for VA, neither the DLCO nor the DLCO/VA was better at predicting oxygen desaturation with exercise. The optimal cut-off of normal was 55% predicted.

SAFETY AND EFFICACY OF LINEZOLID AND AZITHROMYCIN IN THE TREATMENT OF MULTIDRUG-RESISTANT TUBERCULOSIS

To evaluate the correlation between FEV1 and peak expiratory flow (PEF) values expressed as a percentage of their predicted value, and to assess factors influencing differences between the two measurements. Cross-sectional. Pulmonary function laboratory at a tertiary-level teaching hospital in northern India. A total of 6,167 adult patients showing obstructive pattern on spirometry over a 6-year period. None. There was considerable variability between percentage of predicted FEV1 (FEV1%) and percentage of predicted PEF (PEF%). Locally weighted least-square modeling revealed that PEF% underestimated [corrected] FEV1% in patients with less severe obstruction and overestimated [corrected] it in those with more severe obstruction. Using Bland-Altman analysis, PEF% underestimated FEV1% by a mean of only 0.7%; however, limits of agreement were wide (- 27.4 to + 28.8%), indicating that these two measurements cannot be used interchangeably. PEF% and FEV1% were > 5% apart in approximately three fourths and differed by > 10% in approximately one half of the patients. On multivariate analysis, discordance > 5% was significantly influenced by female gender (odds ratio, 1.26; 95% confidence interval [CI], 1.01 to 1.58) and increasing FEV1% (odds ratio, 1.09 for every 10% increase; 95% CI, 1.04 to 1.14) but not by height or age. FEV1% and PEF% are not equivalent in many patients, especially women and those with less severe airflow limitation. Assumptions of parity between PEF% and FEV1% must be avoided.