Single-breath carbon monoxide diffusing capacity

Diastolic Dysfunction in Systemic Sclerosis: Risk Factors and Impact on Mortality

OBJECTIVE

To determine the independent risk factors for diastolic dysfunction (DD) in patients with systemic sclerosis (SSc) and to evaluate the impact of DD on mortality.

METHODS

SSc patients enrolled in the Johns Hopkins Scleroderma Center Cohort between November 1, 2006 and November 1, 2017 with ≥1 analyzable 2-dimensional (2-D) echocardiogram in our system were included (n = 806). DD risk factors and SSc disease characteristics were prospectively obtained, and the presence or absence of DD was determined using the most recent 2-D echocardiogram. Logistic regression models examined associations between clinical risk factors and DD, and Cox proportional hazards models were used to assess survival.

RESULTS

DD was present in 18.6% of participants. The majority of participants were female (84%) with a median age of 58.4 years (interquartile range 48.8-68.1). Older age (odds ratio [OR] 1.12 [95% confidence interval (95% CI) 1.09-1.15], P < 0.001), coronary artery disease (OR 3.69 [95% CI 1.52-8.97], P = 0.004), obesity (OR 4.74 [95% CI 2.57-8.74], P < 0.001), longer SSc disease duration (OR 1.04 [95% CI 1.01-1.06], P = 0.004), diffusing capacity for carbon monoxide ≤60% of predicted (OR 2.41 [95% CI 1.40-4.16], P = 0.002), and history of scleroderma renal crisis (OR 3.18 [95% CI 1.12-9.07], P = 0.031) were all independently associated with an increased risk of DD. Anti-Scl-70 positivity (OR 0.49 [95% CI 0.26-0.93], P = 0.03) and severe gastrointestinal disease (OR 0.48 [95% CI 0.30-0.79], P = 0.004) were associated with a reduced risk of DD. The presence of DD was independently associated with an increase in the risk of mortality (hazard ratio 1.69 [95% CI 1.07-2.68], P = 0.027).

CONCLUSION

DD is independently associated with an increased risk of mortality in patients with SSc. Potentially modifiable risk factors, including coronary artery disease and obesity, should be addressed in patients with SSc to reduce mortality risk.

Assessment of Global Lung Function Initiative (GLI) reference equations for diffusing capacity in relation to respiratory burden in the Swedish CArdioPulmonary bioImage Study (SCAPIS)

The Global Lung Function Initiative (GLI) has recently published international reference values for diffusing capacity of the lung for carbon monoxide (D _LCO). Lower limit of normal (LLN), i.e. the 5th percentile, usually defines impaired D _LCO We examined if the GLI LLN for D _LCO differs from the LLN in a Swedish population of healthy, never-smoking individuals and how any such differences affect identification of subjects with respiratory burden.Spirometry, D _LCO, chest high-resolution computed tomography (HRCT) and questionnaires were obtained from the first 15 040 participants, aged 50-64 years, of the Swedish CArdioPulmonary bioImage Study (SCAPIS). Both GLI reference values and the lambda-mu-sigma (LMS) method were used to define the LLN in asymptomatic never-smokers without respiratory disease (n=4903, of which 2329 were women).Both the median and LLN for D _LCO from SCAPIS were above the median and LLN from the GLI (p<0.05). The prevalence of D _LCO <GLI LLN (and also <SCAPIS LLN) was 3.9%, while the prevalence of D _LCO >GLI LLN but <SCAPIS LLN was 5.7%. Subjects with D _LCO >GLI LLN but <SCAPIS LLN (n=860) had more emphysema (14.3% versus 4.5%, p<0.001), chronic airflow limitation (8.5% versus 3.9%, p<0.001) and chronic bronchitis (8.3% versus 4.4%, p<0.01) than subjects (n=13 600) with normal D _LCO (>GLI LLN and >SCAPIS LLN). No differences were found with regard to physician-diagnosed asthma.The GLI LLN for D _LCO is lower than the estimated LLN in healthy, never-smoking, middle-aged Swedish adults. Individuals with D _LCO above the GLI LLN but below the SCAPIS LLN had, to a larger extent, an increased respiratory burden. This suggests clinical implications for choosing an adequate LLN for studied populations.

The Spinal Structure and Lung Function Relationship in an Untreated Nonambulatory Myelomeningocele Group of Patients

INTRODUCTION

The relationship between spinal structure and respiratory function has been coined as thoracic insufficiency syndrome and is defined as the inability of the thorax to support normal respiratory function or lung growth. Little is known about what supports this relationship in untreated nonambulatory myelomeningocele patients.

METHODS

A prospective cross-sectional study of nonambulatory myelodysplasia patients was performed. Anatomic, radiographic, and functional parameters were evaluated to validate the respiratory-spinal structure relationship. Thirty-one patients diagnosed with nonambulatory myelomeningocele fulfilled the inclusion criteria.

RESULTS

The imaging study confirmed the spinal deformity. Lung functions measured in this patient population describe reduced lung volumes by CT lung volume reconstruction, reduced vital capacity by spirometry, and reduced total lung capacity by the nitrogen washout method. Together, these findings suggest moderate restrictive respiratory disease. The blood count study did not show evidence of anemia or other blood disturbances. Echocardiogram analysis did not show pulmonary hypertension in any patient.

CONCLUSION

The data validate the relationship between spinal structure and lung function. However, there is no simple structural feature that could help to diagnose thoracic insufficiency syndrome. Thus, the diagnosis continues to be based on a combination of clinical findings and radiological and respiratory function evaluations.

LEVEL OF EVIDENCE

Level III.

Heritability and genome-wide association study of diffusing capacity of the lung

Although several genome-wide association studies (GWAS) have investigated the genetics of pulmonary ventilatory function, little is known about the genetic factors that influence gas exchange. The aim of the study was to investigate the heritability of, and genetic variants associated with the diffusing capacity of the lung.GWAS was performed on diffusing capacity of the lung measured by carbon monoxide uptake (D_LCO) and per alveolar volume (V_A) using the single-breath technique, in 8372 individuals from two population-based cohort studies, the Rotterdam Study and the Framingham Heart Study. Heritability was estimated in related (n=6246) and unrelated (n=3286) individuals.Heritability of D_LCO and D_LCO/V_A ranged between 23% and 28% in unrelated individuals and between 45% and 49% in related individuals. Meta-analysis identified a genetic variant in ADGRG6 that is significantly associated with D_LCO/V_A Gene expression analysis of ADGRG6 in human lung tissue revealed a decreased expression in patients with chronic obstructive pulmonary disease (COPD) and subjects with decreased D_LCO/V_AD_LCO and D_LCO/V_A are heritable traits, with a considerable proportion of variance explained by genetics. A functional variant in ADGRG6 gene region was significantly associated with D_LCO/V_A Pulmonary ADGRG6 expression was decreased in patients with COPD.

Ipilimumab and early signs of pulmonary toxicity in patients with metastastic melanoma: a prospective observational study

Ipilimumab, an immune checkpoint inhibitor, is approved for treatment metastastic melanoma and is a promising agent against other malignancies. There is some preliminary evidence from case reports that ipilimumab treatment may be associated with pulmonary side effects. However, data from prospective studies on ipilimumab-related pulmonary toxicity are still scarce. Serial spirometries and measurements of CO-diffusion capacity (DLCO) in patients with metastatic melanoma before and during treatment with ipilimumab were performed. A reduction from baseline of forced vital capacity (FVC) of ≥ 10%, or ≥ 15% of DLCO was defined as clinically meaningful and indicative for pulmonary toxicity. Of 71 patients included in this study, a clinically meaningful lung function decline was registered in 6/65 (9%), 5/44 (11%), and 9/38 (24%) patients after 3, 6, and 9 weeks of treatment initiation, respectively. Even after adjusting for age, concomitant melanoma treatment, progressive pulmonary metastases, and baseline pulmonary function values, mean ± SD DLCO decreased significantly during follow-up (-4.3% ± 13.6% from baseline, p = 0.033). Only 7% of patients reported respiratory symptoms. Clinically manifest ipilimumab-related pneumonitis was diagnosed only in one patient (1.4%). DLCO decline maybe an early indicator of subclinical pulmonary drug toxicity. Therefore, routine pulmonary function testing including DLCO measurement during treatment might help for risk stratification to screen for ipilimumab-related pneumonitis.

The effect of selective internal radiation therapy with yttrium-90 resin microspheres on lung carbon monoxide diffusion capacity

Background

Selective internal radiation therapy (SIRT) with embolization of branches of the hepatic artery is a valuable therapeutic tool for patients with hepatic malignancies; however, it is also associated with lung injury risk due to shunting. Diffusion capacity of the lungs for carbon monoxide (DLCO) is a clinically significant lung function test, and worsening in DLCO is suggested to reflect a limited gas exchange reserve caused by the potential toxicity of chemoradiotherapy or it may be a marker of related lung injury. This study aimed to examine the changes in DLCO during SIRT with resin microspheres in newly treated and retreated patients. Forty consecutive patients who received SIRT for a variety of malignant conditions were included. All subjects were treated with Yttrium-90 labelled resin microspheres. DLCO tests were performed after the procedures. In addition, patients were specifically followed for radiation pneumonitis.

Results

The mean DLCO did not significantly change after the first (82.8 ± 19.4 vs. 83.1 ± 20.9, p = 0.921) and the second treatments (87.4 ± 19.7 vs. 88.6 ± 23.2, p = 0.256). Proportion of patients with impaired DLCO at baseline was not altered significantly after the first (37.5 vs. 45.0%, p = 0.581) and the second treatments (27.3 vs. 27.3%, p = 1.000). Also, percent change in DLCO values did not correlate with radiation dose, lung shunt fraction, or lung exposure dose (p > 0.05 for all comparisons). None of the patients developed radiation pneumonitis.

Conclusions

Our results suggest that no significant change in DLCO in association with SIRT occurs, both after the first or the second treatment sessions. Further larger studies possibly with different protocols are warranted to better delineate DLCO changes after SIRT in a larger spectrum of patients.

Effect of rituximab on pulmonary function in patients with rheumatoid arthritis

BACKGROUND

Rituximab (RTX), a B-cell depleting monoclonal antibody is increasingly used in several antibody-mediated diseases. It has been reported to cause pulmonary toxicity, though mainly during polychemotherapy of malignant lymphoma. Prospective data on RTX-induced pulmonary complications in patients with rheumatoid arthritis (RA) are lacking.

METHODS AND METHODS

Serial spirometries and measurements of diffusion capacity of the lung for carbon monoxide (DLCO) in patients with RA before and 2, 4, 8, and 26 weeks after treatment with RTX were performed. A reduction from baseline of forced vital capacity (FVC) of ≥10%, or ≥15% of DLCO was defined as indicative for pulmonary toxicity.

RESULTS

Thirty-three patients (mean (SD) age 59 (12) years, 27% males) were included. Mean (SD) FVC predicted and DLCO predicted at baseline were 108% (18%) and 88% (18%), respectively. In contrast to FVC, DLCO showed a progressive decline during follow-up with a maximum reduction of 6.1% (95%CI 2.5%, 9.7%; p = 0.001) at 26 weeks compared with baseline. After 26 weeks, 22% of the patients had a ≥15% DLCO decline. None of the patients reported increased dyspnea during follow-up. Risk factors for pulmonary function changes after treatment with RTX were cigarette smoking, repeated administration of the drug, and co-medication with Prednisone.

CONCLUSION

Although no cases of symptomatic lung injury were observed, the progressive DLCO decline seems to indicate the presence of subclinical RTX-induced pulmonary toxicity.

Risk of COPD with obstruction in active smokers with normal spirometry and reduced diffusion capacity

Smokers are assessed for chronic obstructive pulmonary disease (COPD) using spirometry, with COPD defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) as airflow limitation that is not fully reversible with bronchodilators. There is a subset of smokers with normal spirometry (by GOLD criteria), who have a low diffusing capacity of the lung for carbon monoxide (DLCO), a parameter linked to emphysema and small airway disease. The natural history of these "normal spirometry/low DLCO" smokers is unknown.From a cohort of 1570 smokers in the New York City metropolitian area, all of whom had normal spirometry, two groups were randomly selected for lung function follow-up: smokers with normal spirometry/normal DLCO (n=59) and smokers with normal spirometry/low DLCO (n=46). All had normal history, physical examination, complete blood count, urinalysis, HIV status, α1-antitrypsin level, chest radiography, forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC ratio and total lung capacity. Throughout the study, all continued to be active smokers.In the normal spirometry/normal DLCO group assessed over 45±20 months, 3% developed GOLD-defined COPD. In contrast, in the normal spirometry/low DLCO group, followed over 41±31 months, 22% developed GOLD-defined COPD.Despite appearing "normal" according to GOLD, smokers with normal spirometry but low DLCO are at significant risk of developing COPD with obstruction to airflow.

Pulmonary involvement in Fabry disease: overview and perspectives

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by deficiency of alpha-galactosidase A, which leads to storage of sphingolipids in virtually all human cells and consequently to organ dysfunction. Pulmonary involvement is still debated. But, obstructive lung disease is up to ten times more prevalent in patients with FD compared to general public. Also, an accelerated decline in forced expiratory volume in one second (FEV1) over time was observed in these patients. Lysosomal storage of glycosphingolipids is considered leading to small airway disease via hyperplasia of the bronchiolar smooth muscle cells. Larger airways may become involved with ongoing disease process. There is no evidence for involvement of the lung interstitium in FD. The effect of enzyme replacement therapy on respiratory involvement remains to be determined in large, prospective controlled trials.

Lung disease with anti-CCP antibodies but not rheumatoid arthritis or connective tissue disease

OBJECTIVE

We sought to characterize a novel cohort of patients with lung disease, anti-cyclic citrullinated peptide (CCP) antibody positivity, without rheumatoid arthritis (RA) or other connective tissue disease (CTD).

METHODS

The study sample included 74 subjects with respiratory symptoms, evaluated January 2008-January 2010 and found to have a positive anti-CCP antibody but no evidence for RA or other CTD. Each underwent serologic testing, pulmonary physiology testing, and thoracic high-resolution computed tomography (HRCT) scan as part of routine clinical evaluation.

RESULTS

The majority of subjects were women, and most were former cigarette smokers. Four distinct radiographic phenotypes were identified: isolated airways disease (54%), isolated interstitial lung disease (ILD) (14%), mixed airways disease and ILD (26%), and combined pulmonary fibrosis with emphysema (7%). This cohort had a predominance of airways disease, either in isolation or along with a usual interstitial pneumonia-pattern of ILD. Among subjects with high-titer anti-CCP positivity (n=33), three developed the articular manifestations of RA during a median follow-up of 449 days.

CONCLUSION

We have described a unique cohort of patients with anti-CCP antibody positivity and lung disease in the absence of existing RA or other CTD. The lung phenotypic characteristics of this cohort resemble those of established RA and a few of these patients have developed articular RA within a short period of follow-up. The implications of a positive anti-CCP antibody among patients with lung disease but not RA are not yet known, but we believe requires further investigation.

End-Stage Pulmonary Disease and Brachial Plexus Regional Anesthesia

The authors present the challenging clinical scenario of managing a patient with end-stage chronic obstructive pulmonary disease requiring anesthesia for a proximal humerus open reduction and internal fixation who likely would have failed to wean from mechanical ventilation if general anesthesia and endotracheal intubation had been chosen as the maintenance technique. They discuss the effects of general and regional anesthesia on respiratory physiology and describe the perioperative implications of severe pulmonary disease. They also review the various brachial plexus block options that could achieve a satisfactory outcome, with the objective of helping guide practitioners to a rational choice of anesthetic techniques when caring for patients with end-stage pulmonary disease.

Pulmonary function in the morbidly obese

BACKGROUND

Only limited data exist on the relationship of lung function to patients with extreme obesity. To assess the relationship between lung function tests and clinical characteristics in a cohort of morbidly obese patients undergoing evaluation for bariatric procedures in a university hospital in the United States.

METHODS

Consecutive patients undergoing clinical evaluation were reviewed. The variables included demographic, anthropometric, clinical, and pulmonary function data.

RESULTS

A total of 229 patients underwent a standardized preoperative evaluation. Of these 229 patients, 136 (59%) had evaluable data and 102 (75%) were women. The mean +/- standard deviation age was 45 +/- 10 years, the mean weight was 164 +/- 42 kg, and the mean body mass index was 57 +/- 13 kg/m2. Smoking or asthma was reported in 38% and 24% of patients, respectively. The mean forced vital capacity and forced expiratory volume in 1 s was 80% +/- 17% of predicted and 76% +/- 19% of predicted, respectively. Of the 136 patients, 29% had a measured forced expiratory volume in 1 s/forced vital capacity of >or=.08 below the predicted ratio. The mean total lung capacity was 86% +/- 14% of predicted; 26% of subjects had a total lung capacity <80% of predicted. Multivariate logistic regression analysis demonstrated an association of obstructive ventilatory defects with male gender (odds ratio [OR] 2.35, 95% confidence interval [CI] 1.00-5.50) and current or previous smoking (OR 2.41, 95% CI 1.10-5.30), but not body mass index. Restrictive defects were associated with body mass index (OR 1.06, 95% CI 1.01-1.10), in particular, obesity hypoventilation syndrome (OR 3.7, 95% CI 1.2-11.1).

CONCLUSION

The mean preoperative spirometry, lung volumes, and gas exchange values were within the established reference ranges. Restrictive ventilatory defects were less common than obstructive ventilatory patterns and were most prominently associated with obesity hypoventilation syndrome.

Assessment of the relationship between lung parenchymal destruction and impaired pulmonary perfusion on a lobar level in patients with emphysema

PURPOSE

To assess the relationship between lung parenchymal destruction and impaired pulmonary perfusion on a lobar level using CT and MRI in patients with emphysema.

MATERIAL AND METHODS

Forty-five patients with severe emphysema (GOLD III and IV) underwent inspiratory 3D-HRCT and contrast-enhanced MR-perfusion (1.5T; 3.5mmx1.9mmx4mm). 3D-HRCT data was analyzed using a software for detection and visualization of emphysema. Emphysema was categorized in four clusters with different volumes and presented as overlay on the CT. CT and lung perfusion were visually analyzed for three lobes on each side using a four-point-score to grade the abnormalities on CT (1: predominantly small emphysema-clusters to 4: >75% large emphysema-clusters) and MRI (1: normal perfusion to 4: no perfusion).

RESULTS

A total of 270 lobes were evaluated. At CT, the score was 1 for 9 lobes, 2 for 43, 3 for 77, and 4 for 141 lobes. At MRI, the score was 1 for 13 lobes, 2 for 45, 3 for 92, and 4 for 120 lobes. Matching of lung parenchymal destruction and reduced perfusion was found in 213 lobes (weighted kappa=0.8). The score was higher on CT in 44, and higher on MRI in 13 lobes.

CONCLUSION

3D-HRCT and 3D MR-perfusion show a high lobar agreement between parenchymal destruction and reduction of perfusion in patients with severe emphysema.

Functional lung imaging using hyperpolarized gas MRI

The noninvasive assessment of lung function using imaging is increasingly of interest for the study of lung diseases, including chronic obstructive pulmonary disease (COPD) and asthma. Hyperpolarized gas MRI (HP MRI) has demonstrated the ability to detect changes in ventilation, perfusion, and lung microstructure that appear to be associated with both normal lung development and disease progression. The physical characteristics of HP gases and their application to MRI are presented with an emphasis on current applications. Clinical investigations using HP MRI to study asthma, COPD, cystic fibrosis, pediatric chronic lung disease, and lung transplant are reviewed. Recent advances in polarization, pulse sequence development for imaging with Xe-129, and prototype low magnetic field systems dedicated to lung imaging are highlighted as areas of future development for this rapidly evolving technology.

Retrospective study of pulmonary function tests in patients presenting with isolated reduction in single-breath diffusion capacity: implications for the diagnosis of combined obstructive and restrictive lung disease

OBJECTIVE

To examine the frequency and spectrum of diseases associated with isolated reduction in the diffusing capacity of lung for carbon monoxide (D(Lco)).

PATIENTS AND METHODS

We retrospectively identified all potentially dyspneic patients who had pulmonary function tests (PFTs) performed at the Mayo Clinic in Jacksonville, Fla, between January 1, 1990, and June 30, 2000, that showed reduced D(Lco) (< 70% of predicted), normal lung volumes (total lung capacity and residual volume > 80% and < 120% of predicted, respectively), and airflow variables (forced expiratory volume in 1 second and forced vital capacity values > 80% of predicted and forced expiratory volume in 1 second/forced vital capacity ratio > 70% of predicted). Only patients who had also undergone chest computed tomography (CT) and echocardiography within 1 month of PFTs were studied.

RESULTS

Of the 38,095 patients who underwent PFTs during the study period, 179 (0.47%; 95% confidence interval [CI], 0.40%-0.54%) had isolated D(Lco) abnormalities. The 27 patients (15.1%; 95% CI, 10.2%-21.2%) who had also undergone chest CT and echocardiography within 1 month of PFTs form the study cohort reported herein. Their mean D(Lco) was 50% +/- 15% (95% CI, 45%-56%) with average normal pulse oxygen saturation at rest and mild hypoxemia with activity. Thirteen of the 27 patients (48%; 95% CI, 28.7%-68.1%) had underlying emphysema evident on CT. Eleven of these 13 patients had emphysema associated with a restrictive lung process. The 14 patients without emphysema had interstitial lung disease, pulmonary vascular disease, and other isolated findings. Six patients with combined emphysema and idiopathic pulmonary fibrosis accounted for the largest percentage (22%) of patients with Isolated D(Lco) reduction. The mean +/- SD smoking history of the 27 patients in the study cohort was 36 +/- 33 pack-years (range, 0-116 pack-years).

CONCLUSION

Dyspneic patients with respiratory symptoms and normal lung volumes and airflows associated with Isolated reduction in D(Lco) should be evaluated for underlying diseases such as emphysema, with or without a concomitant restrictive process, and pulmonary vascular disease.

Comparison of carbon monoxide (CO) single breath pulmonary diffusing capacity with non-rebreathing, open-circuit CO pulmonary diffusing capacity in healthy children

INTRODUCTION

The standard technique for assessing pulmonary diffusing capacity of the lungs (DL) for carbon monoxide (CO) is the single breath (SB) technique. SB_DLco in children can be problematic because it requires a vital capacity >1.5 L. We have developed an open-circuit technique (OC), which uses the wash-in of CO over a series of 8-10 normal breaths that does not require rebreathing. In this study, we compared the SB_DLco against the OC_DLco.

METHODS

Nineteen healthy children between 7 and 18 years performed SB_DLco and OC_DLco tests. The mean SB_DLco was significantly larger than the mean OC_DLco. The mean difference OC_DLco minus SB_ DLco was: -2.92 +/- 4.21 ml/min/mm Hg, though the difference was negatively correlated with the mean of the two (r = 0.73). The lower mean OC_DLco was in part due to lower lung volume (as measured by alveolar volume (VA)) during the maneuver. In both groups there was a positive correlation between VA and DLco, and the mean VA was -2.17 +/- 1.07 L lower using OC compared to SB. The difference was again negatively correlated with the mean (r = 0.82). The mean OC minus SB difference in DLco/VA was: 6.06 +/- 1.98 ml/min/mm Hg/L, though this difference was positively correlated with the mean, r = 0.76.

CONCLUSIONS

We found a good correlation between both techniques for DLco, VA, and DLco/VA. The OC offers the advantage of minimal subject cooperation, and may be preferable to use in children.

Melatonin Administration Acutely Decreases the Diffusing Capacity of Carbon Monoxide in Human Lungs

BACKGROUND

Most physiological measurements of the pulmonary diffusing capacity use carbon monoxide (CO) as a tracer gas. Similar to CO, melatonin binds the hemoglobin in the blood.

OBJECTIVE

The present study was designed to assess the effect of exogenous melatonin administration on pulmonary functions including diffusing capacity for carbon monoxide (DL(CO)) in healthy subjects.

METHODS

The study was performed in a randomized, double-blind, placebo-controlled manner. DL(CO) was measured in 22 healthy male volunteers (age 18-25 years) who were randomized to melatonin (n = 11) and placebo administration (n = 11). At baseline, DL(CO), alveolar volume (V(A)) and other spirometric parameters such as forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), peak expiratory flow (PEF) and maximal voluntary ventilation (MVV) were measured. DL(CO) was then corrected for the hemoglobin concentration. Measurements were repeated in a double-blind fashion 60 min after the administration of melatonin (1 mg) or placebo.

RESULTS

DL(CO) was significantly decreased (39.31 +/- 4.75 vs. 34.82 +/- 6.18 ml/min/mm Hg) 60 min after the melatonin administration (p = 0.01), while FEV(1), FVC, FEV(1)/FVC, PEF and MVV values did not demonstrate significant differences. Placebo administration did not result in significant alteration in any of these parameters.

CONCLUSIONS

In healthy subjects, oral administration of melatonin acutely influences the DL(CO) without affecting other pulmonary function test results. We conclude that melatonin may have a reducing effect on the DL(CO) in the lungs.

Early emphysematous changes in asymptomatic smokers: detection with 3He MR imaging

PURPOSE

To prospectively compare apparent diffusion coefficient (ADC) measurements derived from diffusion-weighted hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging with functional and structural findings using spirometric tests and thin-section computed tomography (CT) of the lungs in asymptomatic smokers and healthy nonsmokers of similar age.

MATERIALS AND METHODS

All studies were HIPAA compliant and were approved by the institutional review board. Informed consent was obtained. Ventilation and diffusion-weighted 3He MR images were obtained in healthy subjects: 11 smokers (five women, six men; mean age, 47 years+/-18 [standard deviation]; range, 23-73 years) and eight nonsmokers (<100 cigarettes in lifetime) (four women, four men; mean age, 46 years+/-16; range, 23-69 years). Mean ADC values for smokers and nonsmokers were compared with spirometric values, diffusing capacity of the lung for carbon monoxide (Dlco), age, and pack-years with Spearman rank correlation coefficient (rs) and multiple linear regression analysis. Mean ADC value and thin-section CT emphysema index of relative area less than -950 HU (RA950) were compared on a regional basis by using linear mixed-effect models.

RESULTS

Mean ADC values and number of pack-years were significantly correlated (rs=0.60; 95% confidence interval (CI): 0.21, 1.00; P=.007); relationship remained significant after adjustment for age (P=.003). Dlco was strongly correlated with pack-years (rs=-0.63; 95% CI: -0.97, -0.29; P=.004). Negative correlations between mean ADC values and percentage predicted Dlco (rs=-0.79; 95% CI: -0.93, -0.64; P<.001) and the ratio of forced expiratory volume in 1 second to forced vital capacity (rs=-0.72; 95% CI: -0.92, -0.52; P=.001) were statistically significant. Correlations between spirometric values or RA950 and number of pack-years were not significant (.05 level).

CONCLUSION

Correlations between mean ADC values and pulmonary function test measurements for diagnosing emphysema, especially Dlco, were statistically significant.

Detection of age-dependent changes in healthy adult lungs with diffusion-weighted 3He MRI

RATIONALE AND OBJECTIVES

To investigate changes in lung microstructure in healthy adult subjects with no smoking history using diffusion-weighted 3He MRI.

MATERIALS AND METHODS

Diffusion magnetic resonance imaging using hyperpolarized helium 3 (3He) was applied to healthy volunteers to explore the dependence of lung microstructural changes with age, reflected by changes in the apparent diffusion coefficient (ADC) of 3He in lung air spaces. Data from three sites (University of Virginia (UVa), N = 25; University of Wisconsin (UW), N = 8; University of Nottingham (UN), N = 11) were combined in pooled analysis, including a total of N = 44 subjects (age range, 18-69 years; average age, 41.7 +/- 16.7 years).

RESULTS

ADC was found to depend on age at all three sites (UW, R = +0.95, P = .0003; UVa, R = +0.74, P < .0001; UN, R = +0.96, P < .0001). Increases in mean ADCs with age appeared similar across sites (UW, +0.0017 cm2 s(-1) y(-1); UVa, +0.0015 cm2 s(-1) y(-1); pooled, +0.0015 cm2 s(-1) y(-1); P = .71). In a regional analysis performed on UW data, the increase in ADC affected all regions of the lung, but the apical and middle regions showed a greater increase compared with the base of the lung.

CONCLUSION

Results suggest the observed age dependence of the ADC may be caused by changes in lung microstructure that increase alveolar volume during the aging process.

Determinants of health-related quality of life in patients with pulmonary emphysema

QUESTION OF THE STUDY

The aim of our study was to examine the relationship between health-related quality of life (HRQL), lung function parameters and intensity of dyspnea in order to determinate what variables influence the HRQL in patients with pulmonary emphysema.

PATIENTS AND METHODS

Forty (mean aged 66+/-9) consecutive male patients with pulmonary emphysema were evaluated. All patients underwent spirometry, measurement of lung volumes, inspiratory and expiratory respiratory pressure (MIP and MEP), measurement of corrected carbon monoxide diffusing capacity (KCO), and 6-min walking test (6MWT). The scale of dyspnea by the baseline dyspnea index (BDI) and British Medical Council Research (MCR), and the quality of life by Chronic Respiratory Question Disease (CRQD) were also assessed.

RESULTS

FEV1, FVC, 6MWT, KCO, MEP, MIP, BDI and MCR were correlated with dimensions of CRQD. Factor analysis reduced these variables to four factors, which accounted for 86.2% of the total variance: (1) airway obstruction, (2) dyspnea, (3) capacity of effort, (4) maximum static respiratory pressure. In the multiple regression model BDI and MEP explained the 64% of the total variance of CRQD.

CONCLUSIONS

Quality of life measured by CRQD in patients with emphysema is predominantly determined by dyspnea, and in minor degree by expiratory muscle strength. Our results underscore the usefulness of dyspnea scales and MEP in the evaluation of HRQL in patients with emphysema.

Normal Pulmonary Capillary Blood Volume in Patients With Chronic Infiltrative Lung Disease and High Pulmonary Artery Pressure

STUDY OBJECTIVES

Pulmonary capillary blood volume (Qc), a component of diffusing capacity of the lung for carbon monoxide (Dlco), is increased in postcapillary pulmonary hypertension due to valve disease, but is decreased in primitive and thromboembolic pulmonary hypertension. This study was performed to evaluate which way pulmonary Qc is affected in patients with chronic infiltrative lung disease according to the value of systolic pulmonary artery pressure (SPAP).

PATIENTS AND METHODS

Twenty-four patients who were nonsmokers and had chronic infiltrative lung disease secondary to connective tissue disease (12 patients), asbestosis (1 patient), sarcoidosis (5 patients), or of unknown origin (6 patients), and 8 control subjects underwent pulmonary function tests and Doppler echocardiography.

MEASUREMENTS AND RESULTS

Total lung capacity, alveolar-arterial oxygen pressure difference, Dlco, and conductance of the alveolar-capillary membrane (Dm) did not differ between patients with low SPAP (LPAP) [ie, < 30 mm Hg] or high SPAP (HPAP). Patients with LPAP, but not HPAP, experienced significant decreases in pulmonary Qc, whatever the cause of the disease. There was a strong positive correlation between SPAP and Qc scaled by Dm to account for infiltrative disease severity (r = 0.68; p < 0.001).

CONCLUSIONS

We thus conclude that pulmonary Qc is not decreased as expected in patients with chronic infiltrative lung disease and high pulmonary artery pressure. A high Qc/Dm ratio should encourage the physician to look for HPAP compatible with pulmonary hypertension, whatever the etiology of lung infiltrative disease.

Clinical significance of elevated diffusing capacity

STUDY OBJECTIVE

Single-breath diffusing capacity of the lung for carbon monoxide (DLCO) is used as a pulmonary function test (PFT) to assess gas transfer in the lungs. The implications of a low DLCO are well-recognized, but the clinical significance of a high DLCO is not clear. The aim of this study was to identify the clinical correlates of a high DLCO.

PATIENTS AND METHODS

We identified 245 patients with a high DLCO (ie, > 140% predicted) and a matched group of 245 patients with normal DLCO (ie, 85 to 115% predicted), who were selected from a laboratory database of 45,000 patients tested between January 1997 and December 1999. We compared the demographic features, clinical diagnoses, and PFT data between the two groups.

SETTINGS

Large multispecialty group practice.

RESULTS

The patients in the high DLCO group were heavier (mean [+/- SD] weight, 96.0 +/- 22.9 vs 85.0 +/- 21.3 kg, respectively; p < 0.001), had a higher mean body mass index (32.9 +/- 7.4 vs 29.4 +/- 6.4 kg/m(2), respectively; p < 0.001), larger body surface area (p < 0.001), and larger mean total lung capacity (p = 0.007) and alveolar volume (p < 0.001). The clinical diagnoses of obesity (p < 0.001) and asthma (p < 0.001) were more common among patients with high DLCO values. The majority of patients (62%) with a high DLCO had a diagnosis of obesity, asthma, or both. Polycythemia, hemoptysis, and left-to-right shunt were uncommon.

CONCLUSION

A high DLCO on a PFT is most frequently associated with large lung volumes, obesity, and asthma. Other conditions are much less common. A clinical condition, which typically reduces DLCO, may deceptively normalize DLCO in such patients.

Pulmonary impairment and disability

Respiratory disorders, including occupational and environmental lung diseases, are prevalent. Physicians are frequently called upon to determine impairment and aid in the assessment of disability caused by these conditions, either as the treating physician or as an independent medical examiner. In this article we reviewed the role of physicians in determining the presence and severity of pulmonary disorders. A comprehensive clinical assessment and appropriate standardized tests, to objectively characterize the severity of impairment, are the key elements of the evaluation. This assessment may also include the physician's opinion regarding causative factors. Finally, disability determination is made by nonclinicians, through administrative means, based on the degree of impairment and a review of circumstances specific to the individual. Knowledge of these components of disability evaluation will help physicians to better serve their patients and supply appropriate data to the adjudicating system.