Forced Vital Capacity Maneuvers Research Articles

Evaluating the impact of electrode planes on regional lung function assessment.

The aim of the study was to explore the influence of the measurement plane on regional lung function assessed via electrical impedance tomography (EIT). The forced vital capacity (FVC) maneuver was prospectively performed in 30 healthy male volunteers. Simultaneously, EIT measurements were conducted at the 3rd, 4th, and 5th intercostal spaces (ICS). The EIT-based spirometry parameters are calculated in a similar manner to their original definitions. The spatial and temporal distributions of the corresponding functional images were assessed and compared among the measurement planes. All subjects but one were able to perform the FVC maneuver according to the guidelines. Significant differences were found in 67% (6 out of 9) of the EIT-based parameters assessing the spatial and temporal distribution. The fEIT images were most homogeneous at ICS 4 compared to the other two measurement planes, except for the time required for 75% of FVC. The fEIT image FVCEIT distributed toward dorsal regions when the measurement planes moved from ICS 3 to ICS 5, whereas the identified lung areas became smaller. The spatial and temporal distribution of the regional lung function measured via EIT was influenced by the measurement planes. We recommend adhering to the same measurement plane for before-after comparison. ICS 4 was recommended for the sitting subjects performing lung function testing.

A pilot study for development of a pulmonary function test induction jacket to automate effort in performing the forced vital capacity manoeuvre

The pulmonary function test (PFT) induction jacket was invented to make the process of performing the forced vital capacity (FVC) manoeuvre with a computerized spirometer effortless and productive for both the patient and the medical practitioner. The jacket is composed of three layers of PVC material sealed together to form a single jacket with two chambers. The inner chamber is formed between the inner layer and the middle layer, in which cold water at a temperature of 10 °C is circulated using a connected water unit when triggered. Similarly, the outer chamber is formed between the middle layer and the outer layer, in which air is pressurized using a connected air unit. Thirty volunteers performed the FVC manoeuvre with and without wearing the jacket. There was no difference between the results in spirometry parameters in the participants without a jacket and those with a jacket. However, use of the jacket significantly reduced the number of trials the participants had to undergo to perform spirometry. The jacket automated the FVC manoeuvre by triggering a physiological inspiratory gasp using cold water and circumscribing pressurized air for expiration. Additionally, subsequent advancements in the jacket have been suggested.

Spirometry Reference Equations Including Existing and Novel Parameters.

Spirometry is an essential component of pulmonary function testing, with interpretation dependent upon comparing results to normal. Reference equations for mean and lower limit of normal (LLN) are available for usual parameters, including forced vital capacity (FVC), forced expiratory volume in the first second of an FVC maneuver (FEV1), and FEV1/FVC. However, standard parameters do not fully characterize the flow-volume loop and equations are unavailable for the upper limit of normal (ULN). The aim of this study was to develop reference equations for existing and novel spirometry parameters, which more fully describe the flow-volume loop, and to compare these to previously reported equations. Data from healthy participants in NHANES III was used to derive reference equations for existing and novel spirometry parameters accounting for birth sex, age, height, and ethnicity (Caucasian, Mexican American, Black) for ages 8 to 90 years. An iterative process determined %predicted LLN and ULN. Equations were compared to published reported equations. Reference equations were developed for mean, LLN and ULN for existing and novel spirometry parameters for ages 8 to 90. The derived equations closely match mean values of previously published equations, but more closely fit the LLN. Mexican-American and Caucasian values were similar (within 2%) so they were combined, while Black relative to Caucasian/Mexican-American values were lower for some parameters. These reference equations, which account for birth sex, age, height, and ethnicity for existing and novel spirometry parameters, provide a more comprehensive and quantitative evaluation of spirometry and the flow-volume curve.

Dysanapsis in men and women with obesity.

Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in women than in men when matched for lung size. We examined whether differences in pulmonary mechanics with obesity and sex were associated with the dysanapsis ratio (DR), an estimate of airway size when the expiratory flow is maximal, in men and women with and without obesity. In addition, we examined the ability to estimate DR using predicted versus measured static recoil pressure at 50% forced vital capacity (FVC; Pst50FVC). Participants completed pulmonary function testing and measurements of pulmonary mechanics. Flow, volume, and transpulmonary pressure were recorded while completing forced vital capacity (FVC) maneuvers in a body plethysmograph. Static compliance curves were collected using the occlusion technique. DR was calculated using measured values of forced midexpiratory flow and Pst50FVC. DR was also calculated using Pst predicted from previously reported data. There was no significant group (lean vs. obese) by sex interaction or main effect of group on DR. However, women displayed significantly larger DR compared with men. Predicted Pst50FVC was significantly greater than measured Pst50FVC. DR calculated from measured Pst was significantly greater than when using predicted Pst. In conclusion, although obesity does not appear to alter airway size, women may have larger airways compared with men when midexpiratory flow is maximal. In addition, DR estimated using predicted Pst should be used with caution.NEW & NOTEWORTHY It is unclear whether obesity in combination with sex influences the dysanapsis ratio (DR). These data indicate that DR is unaltered in adults with obesity and is greater in women than in men but similar between sexes when matched for lung volume. We also report a significant difference between predicted and measured static recoil pressure. Thus, we caution against predicting static recoil pressure in the calculation of DR.

A CROSS-SECTIONAL COMPARISON BETWEEN TWO TYPES OF FORCED EXPIRATORY MANEUVERS DURING PULMONARY FUNCTION SURVEILLANCE OF US COAL WORKERS, 2016-2019

SESSION TITLE: Education, Research, and Quality Improvement Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Recent spirometry standardization guidelines focus on the flow-volume loop maneuver [FVL] to measure both inspiratory and expiratory airflow during spirometry testing. However, many occupational health surveillance programs routinely perform ‘exhalation only’ maneuvers [EO]. Our aim was to determine spirometry quality differences based on the type of forced vital capacity (FVC) maneuver performed. METHODS: Between 2016–2019, the National Institute for Occupational Safety and Health (NIOSH) conducted health surveillance inclusive of spirometry testing for U.S. coal miners. Tests were conducted in a NIOSH mobile examination unit, by the same technicians using the same flow-type spirometer model. From 2016 to 2018, the EO-FVC maneuver was performed by miners. In 2018, NIOSH spirometry protocols were updated, and subsequent miners were tested using the FVL-FVC maneuver. We compared spirometry test quality differences between EO-FVC and FVL-FVC testing techniques. Quality metric variables of interest were number of acceptable maneuvers, repeatability of maneuvers, maximal expiration to zero flow, excessive hesitation, and overall test quality. Fisher’s exact tests identified univariate quality variable differences. Poisson regression models using SAS Proc GENMOD determined associations between the type of FVC maneuver and test-quality metrics with adjustment for sex, race, BMI, age, and test technician. RESULTS: We compared 2,010 EO-FVC and 3,340 FVL-FVC spirometry tests. Univariate analyses revealed that tests from FVL-FVC maneuvers were more likely to contain three acceptable maneuvers, be repeatable, and have quality grades ‘C ‘or better (p<0.0001, p=0.035, and p<0.0001, respectively). Exhalation to zero flow was more often achieved in EO-FVC maneuvers (p<0.0001). Poisson models indicated that FVL-FVC maneuvers produced significantly more tests with three acceptable maneuvers (PRR=1.07, 95% CI: 1.01, 1.15), and repeatable maneuvers (PRR=1.06, 95% CI: 1.01, 1.13). No significant associations were seen for excessive hesitation and maximal expiration to zero flow parameters. CONCLUSIONS: The type of FVC maneuver performed can influence spirometry test quality. FVL-FVC maneuvers were more likely to produce spirometry tests meeting criteria for acceptability and repeatability when compared to EO-FVC type maneuvers. CLINICAL IMPLICATIONS: Our findings will help inform occupational health surveillance programs as to which type of FVC maneuver they may choose to implement during worker spirometry testing. A change from the EO-FVC to FVL-FVC maneuver would also make occupational health surveillance spirometry records more comparable to spirometry testing being performed in acute care pulmonary function laboratories. DISCLOSURES: No relevant relationships by Kathleen Clark, source=Web Response No relevant relationships by scott hendricks, source=Web Response

Thoracic gas compression during forced expiration is greater in men than women.

Intrapleural pressure during a forced vital capacity (VC) maneuver is often in excess of that required to generate maximal expiratory airflow. This excess pressure compresses alveolar gas (i.e., thoracic gas compression [TGC]), resulting in underestimated forced expiratory flows (FEFs) at a given lung volume. It is unknown if TGC is influenced by sex; however, because men have larger lungs and stronger respiratory muscles, we hypothesized that men would have greater TGC. We examined TGC across the “effort‐dependent” region of VC in healthy young men (n = 11) and women (n = 12). Subjects performed VC maneuvers at varying efforts while airflow, volume, and esophageal pressure (POES) were measured. Quasistatic expiratory deflation curves were used to obtain lung recoil (PLUNG) and alveolar pressures (i.e., PALV = POES–PLUNG). The raw maximal expiratory flow–volume (MEFVraw) curve was obtained from the “maximum effort” VC maneuver. The TGC‐corrected curve was obtained by constructing a “maximal perimeter” curve from all VC efforts (MEFVcorr). TGC was examined via differences between curves in FEFs (∆FEF), area under the expiratory curves (∆AEX), and estimated compressed gas volume (∆VGC) across the VC range. Men displayed greater total ∆AEX (5.4 ± 2.0 vs. 2.0 ± 1.5 L2·s−1; p < .001). ∆FEF was greater in men at 25% of exhaled volume only (p < .05), whereas ∆VGC was systematically greater in men across the entire VC (main effect; p < .05). PALV was also greater in men throughout forced expiration (p < .01). Taken together, these findings demonstrate that men display more TGC, occurring early in forced expiration, likely due to greater expiratory pressures throughout the forced VC maneuver.

Validation of an app-based portable spirometer in adolescents with asthma

Objectives Objective measurements of asthma impairment could aid teens in recognition of changes in asthma status over time. Ready access to a conventional spirometer is not realistic outside of the clinical setting. In this proof-of-concept study, we compared the performance of the VitalFlo mobile spirometer to the nSpire KoKo® sx1000 spirometer for accuracy in measuring Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) in adolescents with asthma. Methods Two hundred forty pulmonary function measurements were collected from 48 adolescents with persistent asthma from the University of North Carolina’s pediatric allergy and pulmonology subspecialty clinics. Participants performed spirometry with the nSpireKoKo® sx1000 spirometer and the VitalFlo spirometer during their clinic visits. 119 simulated FVC maneuvers were conducted on both devices to standardize measurements. Pearson correlations, Bland-Altman procedure, and two-sample comparison tests were performed to assess the relationship between the two spirometers. Results VitalFlo measurements were significantly highly correlated with nSpireKoKo® spirometer values for FEV1, (r 2=0.721, [95% CI, 0.749 ± 0.120], P < 0.001) and moderately for FVC (r 2= 0.617, [95% CI, 0.640 ± 0.130], P < 0.001) measurements. There were no statistically significant differences of the mean FEV1 (M = 0.00764, SD = 0.364, t(59)=0.16, P = 0.87) and FVC measurements (M = 0.00261, SD = 0.565, t(59)=0.036, P = 0.97.) between the VitalFlo and nSpireKoKo® systems. Both devices demonstrated significantly high correlation when comparing the automated FVC (r 2 = 0.997, [95% CI, 1.00 ± 0.00974], P < 0.001) measurements. Bland-Altman plots did not demonstrate significant bias between devices for both FEV1 (0.00764 L) and FVC (0.00261 L) measurements. Conclusions Lung function measurements from the VitalFlo mobile spirometer were comparable to a commercially-available spirometer commonly used in clinical settings. This validated app-based spirometer for home use has the potential to improve asthma self-management.

Global and regional degree of obstruction determined by electrical impedance tomography in patients with obstructive ventilatory defect.

BackgroundElectrical impedance tomography is a continuous imaging method capable of measuring lung volume changes. The purpose of this study was to examine whether EIT was capable of evaluating the degree of obstructive ventilatory defect (OVD) on the global and regional level.Methods41 healthy subjects with no lung diseases and 67 subjects suffering from obstructive lung diseases were examined using EIT and spirometry during forced vital capacity (FVC) maneuver. The subjects were divided into control group (n = 41), early airway obstruction group (n = 26), mild group (n = 17), moderate group (n = 16) and severe group (n = 8) according to the degree of obstruction. Forced expiratory volume in 1 second (FEV1) and FEV1/FVC were determined by EIT. The mode index (MI) was proposed to evaluate the degree of global and regional obstruction; the effectiveness of MI was validated by evaluating posture related change of lung emptying capacity in sitting and supine postures; the degree of regional obstruction was determined according to the cut-off values of MI obtained from receiver operating characteristic (ROC) analysis; regional obstruction was located in the four-quadrant region of interest (ROI) and the contour-map ROI with contour lines at the cut-off values of MI.ResultsSignificant differences were found between different groups (P<0.05) and the global MI was 0.93±0.03, 0.86±0.05, 0.81±0.09, 0.73±0.09 and 0.60±0.11 (mean ±SD), respectively. The cut-off MI value was 0.90, 0.83, 0.77, and 0.65, respectively.ConclusionThe results indicated the potential of EIT to evaluate the degree of obstruction in patients with obstructive ventilatory defect on the global and regional level.

Changes in lung function during exercise are independently mediated by increases in deep body temperature

BackgroundThis study examined whether an increase in deep body temperature contributes to increases in ventilatory flow indicative of bronchodilatation.MethodThe study employed a within-participant repeated measures design. Nine participants (mean (SD):...

Voluntary pulmonary function screening identifies high rates of undiagnosed asymptomatic chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is projected to be the third leading cause of death by 2020. Early detection and screening may alter the course and prognosis associated with lung disease. We investigated the effectiveness of a voluntary public lung function screening program and factors that had a predictive value for asymptomatic COPD in Xi'an, China. Pulmonary function testing (PFT) was conducted on volunteers recruited from four community centers in Xi'an, China, between July and August 2012. Participants underwent three forced vital capacity maneuvers. The maneuver with the best forced expiratory volume in first second was retained. Participants filled out a medical history and environmental exposure survey before undergoing the PFT. Patients who self-reported lung disease on the health survey were excluded from the analysis. Logistical regression was used to determine associations with airway obstruction. A total of 803 volunteers participated in this study, and 33 subjects were excluded as the participants did not meet the requirements of PFT. Of the 770 volunteers, 44 participants had been diagnosed with chronic respiratory diseases previously, and 144 participants (18.7%) met COPD criteria. Four hundred forty-four participants did not self-report any respiratory symptoms, and the remaining 282 participants self-reported respiratory symptoms. Of the asymptomatic participants, 98 volunteers had PFT results that were consistent with COPD and 68.1% of asymptomatic participants were undiagnosed. A greater percentage of women than men had moderate or severe airway obstruction (p = 0.004).Only smoking status (odds ratio = 2.64, 95% confidence interval 1.20-6.04) was associated with asymptomatic COPD. Voluntary public lung function screening programs in China are likely to identify a large number of undiagnosed, asymptomatic COPD. Smoking status is associated with airway obstruction and a greater percentage of women than men had moderate or severe airway obstruction.

Voluntary pulmonary function screening with GOLD standard: an effective and simple approach to detect lung obstruction.

The prevalence of lung obstruction is probably underestimated. Early detection and screening may alter the course and prognosis associated with lung disease. We investigated the effectiveness of voluntary lung function screening program and the agreement between the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and the lower limit of normal (LLN) standard for public screening in Xi'an China. Pulmonary function testing was conducted on volunteers recruited from eight community centers in Xi'an, China between July and August 2012. Participants underwent three forced vital capacity (FVC) maneuvers. The maneuver with the best FEV1 was retained. Participants filled out a medical history survey before undergoing pulmonary function testing. Patients that self-reported lung disease on the health survey were excluded from the analysis. A total of 803 volunteers participated in this study. And 722 participants (93.8%) did not self-report chronic lung disease and were analyzed. Of these participants, 143 subjects (19.8%) were diagnosed by GOLD standard and 134 subjects (18.6%) had obstruction with LLN definition. GOLD definition can identify more asymptomatic subjects (19.1%) with respect to LLN. GOLD definition can detect more lung obstruction in elder subjects compared with young people, the difference is significant (P=0.0007). The overall agreement between the 2 methods was good: the kappa estimate was 0.822. The agreement in subjects aged 40-49, 50-59 and 60-69 years was good: the kappa estimate was 0.82, 0.936 and 0.907 respectively and the agreement in subjects aged 18-29 was inferior: the kappa estimate was only 0.555. Voluntary lung function screening program with GOLD standard may be a simple and effective approach to ensuring high yield detection of lung obstruction in subjects aged 40-69.

The timing of the forced vital capacity.

Based on analysis of more than 2,500 forced vital capacity (FVC) maneuvers, we examined 2 aspects of the standards for spirometry recommended by the 1977 Snowbird Workshop concerning the timing of the FVC maneuver. We compared the forced expiratory volume in one sec (FEV1) when timing was initiated by the back extrapolation method with FEV1 when timing was initiated by flow or volume threshold to determine whether the latter offered a reliable equivalent. Although the mean differences appear to be relatively small, because of variability in initiating expiratory effort, neither alternative is likely to offer a uniformly accurate numeric equivalent to backward extrapolation. We also measured the volume expired before the initiation of the timing as a per cent of FVC to determine whether 10 per cent was a reasonable limit to apply for acceptability of a test. Although 2 SD from the mean of 4.35 per cent were well within this limit, it appears that the technician's judgment of acceptability is sufficient in most cases.

Sex, Lungs, And Forced Expiratory Flows

Women display lower maximal, forced expiratory flows (FEFs) across the vital capacity range compared with height- and age-matched men. This sex-difference on FEFs is believed to increase the prevalence of ventilatory constraint in women compared with men at a given ventilation during exercise. It remains unclear whether this sex-difference in FEFs is evident when absolute lung size is taken into account. Purpose: To investigate the influences of sex, TLC and residual volume on FEFs at rest, and during exercise in healthy adults. METHODS: Forty-seven untrained adults (24 women; 29 ± 6 yrs) with normal pulmonary function (>90% pred.) participated in this study. Subjects completed 9 min of constant-load cycling at 75% of the peak work rate achieved during an incremental cycling test. TLC and RV were obtained at rest and at the end of exercise using He-dilution, and inspiratory and forced vital capacity manoeuvres. FEFs were obtained at 25, 50 and 75% of vital capacity (FEF25%, FEF50% and FEF75%, respectively). Multivariate analyses of covariance (MANCOVA) were used to examine the effect of sex on FEFs after controlling for RV and TLC. RESULTS: Height, TLC and RV were larger for men than women (P < 0.05), as expected. The TLC to height ratio was greater in men than women (45 ± 9 ml·cm-1 v 35 ± 5 ml·cm-1, P < 0.05). FEFs increased during exercise for both sexes (P < 0.05), suggesting bronchodilation. The MANCOVA revealed a main-effect of sex on FEFs at rest and during exercise, where FEFs were systematically higher for men than women (P < 0.05). Importantly, however, the main-effect of sex on FEFs disappeared when TLC and RV were entered into the model as covariates. CONCLUSIONS: The differences in FEFs of our subjects could not be explained on the basis of sex alone. Instead, our analyses suggests that FEFs appear similar between young men and women if one controls for static lung volumes - a result that was also observed in the presence of exercise-induced bronchodilation. Thus, the higher prevalence of ventilatory constraint during exercise in women compared with height-matched men is likely the result of women having a smaller TLC relative to their height, as opposed to a sexual dimorphism in airway size/caliber for a given lung size (dysanapsis). Supported by NIH Grant HL71478

PIKO‐6® vs. forced spirometry in asthmatic children

The PIKO-6® is an electronic device that measures forced expiratory volume at seconds 1 (FEV1) and 6 (FEV6) of a forced vital capacity (FVC) maneuver. This device could aid in diagnosing obstructive respiratory diseases. To determine the concordance of FEV1, FEV6, and the FEV1/FEV6 quotient achieved with PIKO-6® versus spirometric values from asthmatic patients, and compare results with measures from healthy children. A cross-sectional study with asthmatic and healthy 6-to-14-year-old children, all of whom performed a forced spirometry as well as a PIKO-6® test. The study included 82 subjects (58 asthmatics, 24 healthy children). Except for the functional parameters, the basal characteristics of the two groups were similar. The concordance correlation coefficient (CCC) for FEV1 was 0.938 (P < 0.001), with 95% limits of agreement of -0.591 to 0.512 L, and an average of differences of -0.040 L. For FEV6, CCC was 0.927 (P < 0.001), and the 95% limits of agreement were -0.751 to 0.598 L with an average of differences of -0.077 L. The concordance analysis and the FEV1 and FEV6 associations were better in children with controlled asthma and healthy subjects, as well as in the post-bronchodilator results. The concordance between PIKO-6® and spirometry was lower in patients with partially controlled or uncontrolled asthma compared to controlled or healthy children. The broad limits of agreement show that the FEV1, FEV6, and FEV1/FEV6 obtained with the PIKO-6® are not interchangeable with spirometry results. Longitudinal evaluations of asthma patients are necessary to assess the utility of PIKO-6®.

Disturbance of respiratory muscle control in a patient with early-stage multiple sclerosis

To the Editor: Respiratory dysfunction from multiple sclerosis (MS) is most commonly of insidious onset and related to progressive respiratory muscle weakness [1]. Disorders of respiratory muscle coordination are poorly recognised and challenging to diagnose. We present a case of a patient with MS and no clear muscle weakness whose dyspnoea was associated with a disorder of respiratory muscle control. The potential utility of oesophageal manometry for diagnosis of unexplained dyspnoea is highlighted. A 54-year-old female with relapsing-remitting MS presented with 2 weeks of dyspnoea and orthopnoea. She was ambulatory with a low extended disability score of 1.5. 6 months earlier she started cyclophosphamide for disease progression recognised by magnetic resonance imaging (MRI). A week after her last infusion she developed severe dyspnoea and orthopnoea. She had no other symptoms. Her vital signs were normal. Her laboratory tests and arterial blood gas were unremarkable. Chest computed tomography showed no pulmonary parenchymal disease. Echocardiography was unremarkable. Pulmonary function testing (PFTs) demonstrated severe restriction, with a 14% lower vital capacity in the supine position. Her dyspnoea and PFTs improved over the following 1–2 months, but she did not return to her baseline level of pulmonary function. Electromyography (EMG) with phrenic nerve conduction studies demonstrated no abnormalities. MRI was prohibited by her orthopnoea. Previously, MRI demonstrated extensive demyelination in the brain and brainstem that was asymptomatic. Oesophageal manometry was performed to exclude the possibility of bilateral diaphragmatic dysfunction and to elucidate her unexplained dyspnoea. A balloon-catheter was inserted via the nose to position the balloon in the distal oesophagus to estimate pleural pressure. Repeated attempts to perform a forced vital capacity manoeuvre consistently demonstrated fluctuating exhalations, as evidenced by the saw tooth pattern of the flow volume curve (fig. …

Focus on Diagnosis: Spirometry

1. Kamakshya P. Patra, MD 1. Department of Pediatrics, Mayo Clinic, Rochester, MN. * Abbreviations: FEF25%–75%: : forced expiratory flow, midexpiratory phase FEV1: : forced expiratory volume fraction in 1 second FVC: : forced vital capacity PEFR: : peak expiratory flow rate Office spirometry, traditionally done by the pulmonary specialist, has become commonplace in the pediatric primary care office. The National Asthma Education and Prevention Program guidelines recommend routine use of spirometry for the initial diagnosis and ongoing management of asthma. A nationwide survey demonstrated that only 21% of physicians used spirometry for the management of children with asthma, as per the guidelines. And, approximately one half of the physicians were unable to interpret the results of spirometry. Office spirometry has been shown to result in change in asthma management in 15% of children. In 45% of cases, the severity of asthma was underrated by the providers in the absence of spirometry. A peak flow meter, which measures peak expiratory flow rate (PEFR), is a simple, inexpensive, and portable device that may be helpful in the management of asthma. However, PEFR is effort-dependent and does not reflect small airway function. The average cost of a good spirometer is in the $1,500 to $2,000 range. There must be training of the office personnel who perform the spirometry, and the spirometer should be calibrated at least daily. In general, patients must be at least age 4 to 4.5 years to perform reliable forced vital capacity (FVC) maneuvers required for spirometry. A 7-year-old girl has experienced wheezing since age 3 years and has been diagnosed as having asthma. Her symptoms did not improve despite therapy with albuterol, corticosteroids, salmeterol, and monteleukast. She was referred to the pediatric pulmonology clinic for persistent symptomatology. Spirometry was performed, which revealed a fixed obstruction. Flow volume loops revealed truncation of inspiratory and expiratory limbs (Fig 1). Computed tomography scan of the …

Focus on Diagnosis

Focus on Diagnosis

Spatial and temporal heterogeneity of regional lung ventilation determined by electrical impedance tomography during pulmonary function testing

Electrical impedance tomography (EIT) is a functional imaging modality capable of tracing continuously regional pulmonary gas volume changes. The aim of our study was to determine if EIT was able to assess spatial and temporal heterogeneity of ventilation during pulmonary function testing in 14 young (37 ± 10 yr, mean age ± SD) and 12 elderly (71 ± 9 yr) subjects without lung disease and in 33 patients with chronic obstructive pulmonary disease (71 ± 9 yr). EIT and spirometry examinations were performed during tidal breathing and a forced vital capacity (FVC) maneuver preceded by full inspiration to total lung capacity. Regional inspiratory vital capacity (IVC); FVC; forced expiratory volume in 1 s (FEV(1)); FEV(1)/FVC; times required to expire 25%, 50%, 75%, and 90% of FVC (t(25), t(50), t(75), t(90)); and tidal volume (V(T)) were determined in 912 EIT image pixels in the chest cross section. Coefficients of variation (CV) were calculated from all pixel values of IVC, FVC, FEV(1), and V(T) to characterize the ventilation heterogeneity. The highest values were found in patients, and no differences existed between the healthy young and elderly subjects. Receiver-operating characteristics curves showed that CV of regional IVC, FVC, FEV(1), and V(T) discriminated the young and elderly subjects from the patients. Frequency distributions of pixel FEV(1)/FVC, t(25), t(50), t(75), and t(90) identified the highest ventilation heterogeneity in patients but distinguished also the healthy young from the elderly subjects. These results indicate that EIT may provide additional information during pulmonary function testing and identify pathologic and age-related spatial and temporal heterogeneity of regional lung function.

Systemic Inflammation and Its Response to Treatment in Patients With Asthma

Asthma is an obstructive airway disease characterized by airway inflammation. To measure systemic inflammation in asthma patients, and to assess the effect of treatment on systemic inflammation. In 30 newly diagnosed non-randomized adult asthma patients we measured systemic inflammation markers (serum high-sensitivity C-reactive protein, total leukocyte count, and erythrocyte sedimentation rate) before and after a 6-week standard treatment with inhaled steroids and inhaled β(2) agonist. The comparison group comprised 20 healthy control subjects. All the subjects were non-smokers. The measured systemic inflammation markers were higher in the asthma patients: high-sensitivity C-reactive protein 4.8 ± 6.0 mg/dL vs 1.5 ± 1.4 mg/dL, P < .001; total leukocyte count 8,936 ± 2,592 cells/μL versus 7,741 ± 1,924 cells/μL, P < .001; erythrocyte sedimentation rate 24.8 ± 12.3 mm/h versus 15.3 ± 6.5 mm/h, P < .001. In the asthma patients, high-sensitivity C-reactive protein negatively correlated with percent-of-predicted FEV(1) (r = -0.64, P = .001), percent-of-predicted forced vital capacity (FVC) (r = -0.39, P = .03), FEV(1)/FVC% (r = -0.71, P < .001), and percent-of-predicted forced expiratory flow during the middle half of the FVC maneuver (FEF(25-75)) (r = -0.51, P = .004). Total leukocyte count negatively correlated with percent-of-predicted FEV(1) (r = -0.64, P = .001), percent-of-predicted FEV(1)/FVC (r = -0.74, P < .001), and percent-of-predicted FEF(25-75) (r = -0.58, P = .001). Body mass index positively correlated with high-sensitivity C-reactive protein (r = 0.65, P < .001). Multiple linear regression showed significant correlation of high-sensitivity C-reactive protein (r(2) = 0.75) with age (β = 0.31, P = .008), body mass index (β = 0.99, P = .001), family size (β = 0.33, P = .008), and weight (β = -0.45, P = .01). The systemic inflammation markers decreased significantly (P < .001 for all comparisons) after 6 weeks of treatment: high-sensitivity C-reactive protein decreased from 4.8 ± 6.0 mg/dL to 2.4 ± 5.4 mg/dL, total leukocyte count decreased from 8,936 ± 2,592 cells/μL to 6,960 ± 1,785 cells/μL, and erythrocyte sedimentation rate decreased from 24.8 ± 12.3 mm/h to 15.8 ± 10.1 mm/h. Inhaled steroids plus inhaled β(2) agonist significantly reduced systemic inflammation in asthma patients.

Analysis of cardiovascular system responses to forced vital capacity in COPD

The forced vital capacity (FVC) test is routinely performed to evaluate pulmonary function in patients with chronic obstructive pulmonary disease (COPD). However, the influence of the FVC maneuver on the cardiovascular system of patients with COPD is poorly understood. To analyze the behavior of heart rate (HR), blood pressure (BP) and heart rate variability (HRV) during the FVC test in COPD patients. Nineteen men with COPD (72±7 years, GOLD stage I=3, II=5, III=7 and IV=4 patients) performed the FVC test while having their HR monitored. HRV was assessed in time (rMSSD) and frequency domains (LF, HF and LF/HF) at rest, before and after the best FVC maneuver. BP was measured at rest, immediately before and at the end of the test, as well as 10 minutes after the end of the test. At the beginning of the FVC maneuver, HR decreased (p<0.001) and then increased gradually until the end of the test (p<0.001). After the end of maneuver, HR continued to increase until it reached a peak (p<0.001), and then it fell quickly to below at-rest values (p<0.001) prior to returning to baseline. The BP and HRV indices did not change during the assessment. The FVC test influences the behavior of COPD patient HR without changing autonomic control or BP.