Measured diffusion capacity versus prediction equation estimates in blacks without lung disease

Delivering effective, comprehensive, multi-exercise component cardiac rehabilitation (CR) for chronic heart failure patients in low resource settings in sub-Saharan Africa: Queen Elizabeth Central Hospital-(QECH-CR) randomised CR study, Malawi

BACKGROUND

The delivery of Cardiac Rehabilitation (CR) and attaining evidence-based treatment goals are challenging in developing countries, such as Malawi. The aims of this study were to (i) assess the effects of exercise training/ CR programme on cardiorespiratory and functional capacity of patients with chronic heart failure (CHF), and (ii) examine the effectiveness of a novel, hybrid CR delivery using integrated supervised hospital- and home-based caregiver approaches.

METHODS

A pre-registered (UMIN000045380), randomised controlled trial of CR exercise therapy in patients with CHF was conducted between September 2021 and May 2022. Sixty CHF participants were randomly assigned into a parallel design-exercise therapy (ET) (n = 30) or standard of care (n = 30) groups. Resting hemodynamics, oxygen saturation, distance walked in six-minutes (6MWD) and estimated peak oxygen consumption (VO2 peak) constituted the outcome measures. The exercise group received supervised, group, circuit-based ET once weekly within the hospital setting and prescribed home-based exercise twice weekly for 12 weeks. Participants in both arms received a group-based, health behaviour change targeted education (usual care) at baseline, 8-, 12- and 16-weeks.

RESULTS

Most of the participants were female (57%) with a mean age of 51.9 ±15.7 years. Sixty-five percent (65%) were in New York Heart Association class III, mostly with preserved left ventricular ejection fraction (HFpEF) (mean Left Ventricular Ejection Fraction 52.9 ±10.6%). The 12-weeks ET led to significant reductions in resting haemodynamic measures (all P <0.05). The ET showed significantly higher improvements in the 6MWD (103.6 versus 13.9 m, p<0.001) and VO2 peak (3.0 versus 0.4 ml·kg-1·min-1, p <0.001). Significant improvements in 6MWD and VO2 peak (both p<0.001), in favour of ET, were also observed across all follow-up timepoints.

CONCLUSION

This novel, randomised, hybrid ET-based CR, delivered to mainly HFpEF patients using an integrated hospital- and home-based approach effectively improved exercise tolerance, cardiorespiratory fitness capacities and reduced perceived exertion in a resource-limited setting.

Reference equations for pulmonary diffusing capacity using segmented regression show similar predictive accuracy as GAMLSS models

Purpose

To determine whether generalised additive models of location, scale and shape (GAMLSS) developed for pulmonary diffusing capacity are superior to segmented (piecewise) regression models, and to update reference equations for pulmonary diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO), which may be affected by the equipment used for its measurement.

Methods

Data were pooled from five studies that developed reference equations for DLCO and DLNO (n=530 F/546 M; 5–95 years old, body mass index 12.4–39.0 kg/m²). Reference equations were created for DLCO and DLNO using both GAMLSS and segmented linear regression. Cross-validation was applied to compare the prediction accuracy of the two models as follows: 80% of the pooled data were used to create the equations, and the remaining 20% was used to examine the fit. This was repeated 100 times. Then, the root-mean-square error was compared between both models.

Results

In males, GAMLSS models were 7% worse to 3% better compared to segmented regression for DLCO and DLNO. In females, GAMLSS models were 2% worse to 5% better compared to segmented linear regression for DLCO and DLNO. The Hyp'Air Compact measured DLNO and alveolar volume (VA) that was approximately 16–20 mL/min/mm Hg and 0.2–0.4 L higher, respectively, compared to the Jaeger MasterScreen Pro. The measured DLCO was similar between devices after controlling for altitude.

Conclusions

For the development of pulmonary function reference equations, we propose that segmented linear regression can be used instead of GAMLSS due to its simplicity, especially when the predictive accuracy is similar between the two models, overall.

Addressing Race in Pulmonary Function Testing by Aligning Intent and Evidence With Practice and Perception

The practice of using race or ethnicity in medicine to explain differences between individuals is being called into question because it may contribute to biased medical care and research that perpetuates health disparities and structural racism. A commonly cited example is the use of race or ethnicity in the interpretation of pulmonary function test (PFT) results, yet the perspectives of practicing pulmonologists and physiologists are missing from this discussion. This discussion has global relevance for increasingly multicultural communities in which the range of values that represent normal lung function is uncertain. We review the underlying sources of differences in lung function, including those that may be captured by race or ethnicity, and demonstrate how the current practice of PFT measurement and interpretation is imperfect in its ability to describe accurately the relationship between function and health outcomes. We summarize the arguments against using race-specific equations as well as address concerns about removing race from the interpretation of PFT results. Further, we outline knowledge gaps and critical questions that need to be answered to change the current approach of including race or ethnicity in PFT results interpretation thoughtfully. Finally, we propose changes in interpretation strategies and future research to reduce health disparities.

The need for race-specific reference equations for pulmonary diffusing capacity for nitric oxide

BACKGROUND

Few reference equations exist for healthy adults of various races for pulmonary diffusing capacity for nitric oxide (DLNO). The purpose of this study was to collect pilot data to demonstrate that race-specific reference equations are needed for DLNO.

METHODS

African Americans (blacks) were chosen as the comparative racial group. In 2016, a total of 59 healthy black subjects (27 males and 32 females) were recruited to perform a full battery of pulmonary function tests. In the development of DLNO reference equations, a white reference sample (randomly drawn from a population) matched to the black sample for sex, age, and height was used. Multiple linear regression equations for DLNO, alveolar volume (VA), and pulmonary diffusing capacity for carbon monoxide (DLCO) using a 5-6 s breath-hold were developed.

RESULTS

Our models demonstrated that sex, age2, race, and height explained 71% of the variance in DLNO and DLCO, with race accounting for approximately 5-10% of the total variance. After normalizing for sex, age2, and height, blacks had a 12.4 and 3.9 mL/min/mmHg lower DLNO and DLCO, respectively, compared to whites. The lower diffusing capacity values in blacks are due, in part, to their 0.6 L lower VA (controlling for sex and height).

CONCLUSION

The results of this pilot data reveal small but important and statistically significant racial differences in DLNO and DLCO in adults. Future reference equations should account for racial differences. If these differences are not accounted for, then the risk of falsely diagnosing lung disease increase in blacks when using reference equations for whites.

Reduction in TLco and survival in a clinical population

How best to express the level of lung gas transfer (TLco) function has not been properly explored. We used the most recent clinical data from 13 829 patients (54% male, 10% non-European ancestry), median age 60.5 years (range 20-97), median survival 3.5 years (range 0-20) to determine how best to express TLco function in terms of its relation to survival. The proportion of subjects of non-European ancestry with Global Lung Function Initiative (GLI) TLco z-scores above predicted was reduced but was significantly increased between -1.5 to -3.5 suggesting the need for ethnicity appropriate equations. Applying GLI FVC ethnicity methodology to GLI TLco z-scores removed this ethnic bias and was used for all subsequent analysis. TLco z-scores using the GLI equations were compared with Miller's US equations with median TLco z-scores being -1.43 and -1.50 for GLI and Miller equations respectively (interquartile range -2.8 to -0.3 and -2.4 to -0.7, respectively). GLI TLco z-scores gave the best Cox regression model for predicting survival. A previously proposed six-tier grading system for level of lung function did not show much separation in survival risk in the less severe grades. A new four-tier grading based on z-scores of -1.645, -3 and -5 showed better separation of risk with hazard ratio for all-cause mortality of 2.0, 3.4 and 6.6 with increasing severity. Using GLI FVC ethnicity methodology to GLI TLco predictions removed ethnic bias and may be the best approach until relevant datasets are available.

Reference Values for Pulmonary Single-Breath Diffusing Capacity - Results of the "Study of Health in Pomerania"

OBJECTIVES

 The assessment of pulmonary single-breath diffusing capacity is a frequently performed diagnostic procedure and considered as an important tool in medical surveillance examinations of pulmonary diseases.The aim of this study was to establish reference equations for pulmonary single-breath diffusing capacity parameters in a representative adult-population across a wide age range and to compare the normative values from this sample with previous ones.

METHODS

 Diffusing capacity measurement was carried out in 3566 participants (1811 males) of a cross-sectional, population-based survey ("Study of Health in Pomerania - SHIP").

RESULTS

 Individuals with cardiopulmonary disorders and current smoking habits were excluded, resulting in 1786 healthy individuals (923 males), aged 20 - 84 years. Prediction equations for both sexes were established by quantile regression analyses, taking into consideration the influence of age, height, weight and former smoking.

CONCLUSION

 The study provides a novel set of prediction equations for pulmonary single-breath diffusing capacity in an adult Caucasian population. The results are comparable to previously reported equations, underline their importance and draw attention to the need for up-to-date reference equations that adequately take into account both the subjects' origin, age, anthropometric characteristics and the equipment used.

Genome-Wide Association Analysis of Single-Breath DlCO

Dl_CO is a widely used pulmonary function test in clinical practice and a particularly useful measure for assessing patients with chronic obstructive pulmonary disease (COPD). We hypothesized that elucidating genetic determinants of Dl_CO could lead to better understanding of the genetic architecture of COPD. We estimated the heritability of Dl_CO using common genetic variants and performed genome-wide association analyses in four cohorts enriched for subjects with COPD (COPDGene [Genetic Epidemiology of COPD], NETT [National Emphysema Treatment Trial], GenKOLS [Genetics of Chronic Obstructive Lung Disease study], and TESRA [Treatment of Emphysema With a Gamma-Selective Retinoid Agonist study]) using a combined European ancestry white dataset and a COPDGene African American dataset. We assessed our genome-wide significant and suggestive associations for Dl_CO in previously reported genome-wide association studies of COPD and related traits. We also characterized associations of known COPD-associated variants and Dl_CO. We estimated the SNP-based heritability of Dl_CO in the European ancestry white population to be 22% (P = 0.0004). We identified three genome-wide significant associations with Dl_CO: variants near TGFB2, CHRNA3, and PDE11A loci (P < 5 × 10^-8). In addition, 12 loci were suggestively associated with Dl_CO in European ancestry white (P < 1 × 10^-5 in the combined analysis and P < 0.05 in both COPDGene and GenKOLS), including variants near NEGR1, CADM2, PCDH7, RETREG1, DACT2, NRG1, ANKRD18A, KRT86, NTN4, ARHGAP28, INSR, and PCBP3. Some Dl_CO-associated variants were also associated with COPD, emphysema, and/or spirometric values. Among 25 previously reported COPD loci, TGFB2, CHRNA3/CHRNA5, FAM13A, DSP, and CYP2A6 were associated with Dl_CO (P < 0.001). We identified several genetic loci that were significantly associated with Dl_CO and characterized effects of known COPD-associated loci on Dl_CO. These results could lead to better understanding of the heterogeneous nature of COPD.

Lung diffusing capacity in sub-Saharan Africans versus European Caucasians

Single breath measurements of lung diffusing capacity (DL) for carbon monoxide (CO) and nitric oxide (NO) were performed in age-, sex-, weight- and height-matched 32 sub-Saharan Africans (13 women) and 32 Caucasian Europeans, and repeated in 14 of each group at 80% of maximum exercise capacity. In Africans versus Caucasians respectively, DL_NO was 153±31 vs 176±38ml/mmHg/min at rest (P<0.001) and 210±48 vs 241±52ml/mmHg/min at exercise (P<0.01) while hemoglobin-adjusted DL_CO was 29±6 vs 34±6ml/mmHg/min at rest (P<0.001), and 46±11 vs 51±13ml/mmHg/min at exercise (P<0.01). However there were no differences in DL_CO/alveolar volume(V_A) (K_CO) and DL_NO/V_A(K_NO). The sitting-to-standing height ratio was lower in the Africans. Differences in lung volume with respect to body height explain lower DL_NO and DL_CO in sub-Saharan Africans as compared to Caucasian Europeans.

The history of the pulmonary diffusing capacity for nitric oxide DL,NO

The DL,NO (TL,NO) had its unexpected origins in the Paris "events" of 1968 and the unsuccessful efforts of the UK tobacco industry in the 1970's to create a "safer cigarette". Adoption of the technique has been slow due to the instability of NO in air, lack of standardisation of the technique and lack of agreement as to whether DL,NO is equal to or merely reflects membrane diffusing capacity (DM). With the availability of inexpensive analysers, standardisation of the technique and publication of reference equations we believe that its worldwide use will increase.

Pulmonary diffusing capacity in healthy African-American and Caucasian children

Previous studies of pulmonary diffusing capacity in healthy children primarily focused upon Caucasian (C) subjects. Since lung volumes in African-Americans (AA) are smaller than lung volumes in C subjects of the same height, diffusing capacity values in AA children might be interpreted as low or abnormal using currently available equations without adjusting for race. Healthy AA (N = 151) and C (N = 301) children between 5 and 18 years of age performed acceptable measurements of single breath pulmonary diffusing capacity for carbon monoxide (DLCO ) and alveolar volume (VA ) according to current ATS/ERS guidelines. The natural log of DLCO and VA were associated with height, gender, age, and race; AA children had lower DLCO and VA compared to C children. Adjustment of DLCO for Hemoglobin (Hgb) resulted in no significant difference in DLCO among these healthy subjects with normal Hgb. In summary, we report prediction equations for DLCO and VA that include adjustment for race (C; AA) demonstrating that AA have lower DLCO and VA compared to C children for the same height, gender, and age.

Refractory ceramic fiber (RCF) toxicity and epidemiology: a review

This paper provides a review of the relevant literature on refractory ceramic fibers (RCFs), summarizing relevant data and information on the manufacture, processing, applications, potential occupational exposure, toxicology, epidemiology, risk analysis, and risk management. RCFs are amorphous fibers used for high-temperature insulation applications. RCFs are less durable/biopersistent than amphibole asbestos, but more durable/biopersistent than many other synthetic vitreous fibers (SVFs). Moreover, as produced/used, some RCFs are respirable. Toxicology studies with rodents using various exposure methods have shown that RCFs can cause fibrosis, lung cancer, and mesothelioma. Interpretation of these animal studies is difficult for various reasons (e.g., overload in chronic inhalation bioassays). Epidemiological studies of occupationally exposed cohorts in Europe and the United States have demonstrated measurable effects (e.g., mild respiratory symptoms and pleural plaques) but no disease (i.e., no interstitial fibrosis, no excess lung cancer, and no mesothelioma) to date. The RCF industry, working cooperatively with various government agencies in the United States, has developed a comprehensive product stewardship program (PSP) to identify and control risks associated with occupational exposure. One provision of the PSP is the adoption of a voluntary recommended exposure guideline (REG) of 0.5 fibers/milliliter (f/ml). Selected on the basis of prudence and demonstrated feasibility, compliance with the REG should reduce risks to levels between 0.073/1000 and 1.2/1000, based on extrapolations from chronic animal inhalation studies.

Differences between Finnish and European reference values for pulmonary diffusing capacity

OBJECTIVES

To compare European (ECSC) and Finnish reference values for single-breath diffusing capacity for carbon monoxide (DL(CO)).

STUDY DESIGN

Finnish reference values for DL(CO), specific diffusing capacity (DL(CO)/VA) and total lung capacity (TLC) were compared with ECSC reference values calculated for different age, height and weight groups. In addition, 10 healthy subjects performed the test with both the Finnish method (inhaled volume 90% of vital capacity, VC) and the ECSC method (inhaled volume 100% of VC).

METHODS

Percentual differences between the ECSC and Finnish reference values for DL(CO), TLC and DL(CO)/VA were calculated. The results of measurements of DL(CO) and TLC by using inhaled volume of 100% of VC and 90% of VC in 10 healthy subjects were compared.

RESULTS

The Finnish DL(CO) reference value for men was 3-12% and for women 8-20% smaller than the ECSC reference value. TLC calculated according to Finnish equations was 2-14% greater than that based on ECSC equations. The ECSC reference value for DL(CO)/VA was about 20% greater than the Finnish reference value in men and 30% greater than that in women. The 10 healthy subjects had significantly higher DL(CO) when measured according to the ECSC method as compared with the Finnish one (p < 0.004).

CONCLUSIONS

The Finnish reference values for DL(CO) were about 10% smaller, but TLC 10% and DL(CO)/VA 20-30% greater than ECSC reference values in subjects of the same age, height, weight and gender. The difference in DL(CO) is explained by the different inhaled lung volumes used in the two methods, the difference in lung volumes probably arising from ethnic differences in thoracic cavity.

Abnormal predicted diffusion capacities in healthy Asians: an inequality with a solution

BACKGROUND

Asian lung volumes are 10-15% less than those of Caucasians.

OBJECTIVES

To test the hypothesis that healthy Asians might be labeled as abnormal using three commonly used Caucasian-derived prediction equation estimates (PEE) of DLCO currently used. In addition, a Chinese-derived PEE of DLCO was tested to determine its validity in non-Chinese Asians.

METHODS

Forty-one healthy Asians underwent DLCO testing. Controls consisted of the PEE and 12 healthy Caucasians. Measured DLCO was compared with the Miller, Knudson, Crapo and one Chinese PEE. Abnormal was defined as a DLCO <80% predicted. Gas dilution and plethysmography estimated alveolar volume. Proportions in parentheses in the results below are DLCO adjusted for alveolar volume.

RESULTS

The average Asian DLCO was 25.75 +/- 5.55 ml/min/mm Hg, no different than the predicted DLCO of 25.29 +/- 5.53 seen with Chinese PEE. This was different (p < 0.01) than the predicted DLCO of 27.82 +/- 5.09, 33.66 +/- 6.29, and 31.64 +/- 5.33 for the Miller, Knudson, and Crapo equations, respectively. This resulted in 4/41 (0/41), 27/39 (2/39), 21/41 (3/41) and 1/41 (0/41) DLCO measurements being defined as abnormal using Miller, Knudson, Crapo and Chinese PEE, respectively. In Caucasians, the measured DLCO was similar to the Miller but significantly lower than the Knudson and Crapo PEE. Measured lung volumes were significantly smaller compared to predicted for the three Caucasian PEE in Asians, with no difference in Caucasians. There was no difference in measured lung volumes and Chinese PEE.

CONCLUSIONS

Current Caucasian PEE for DLCO when used in healthy Asians result in an abnormal reading that is incorrect from 10 to 50% of the time. This PEE failure is related to a reduction in lung volume not accounted for. The Chinese PEE for DLCO works for non-Chinese Asians and should replace Caucasian PEE in the US in all Asians.

Dissociation of Lung Function Changes with Humoral Immunity during Inhaled Human Insulin Therapy

RATIONALE

Inhaled human insulin (INH; Exubera [human insulin (recombinant DNA origin) Inhalation Powder]) causes small changes in pulmonary function and increases in insulin antibodies compared with subcutaneous (SC) insulin.

OBJECTIVES

To investigate the relationship between changes in pulmonary function and insulin antibodies and acute effects of INH on lung function.

METHODS

In a 24-wk multicenter study, 226 patients with type 1 diabetes were randomized to receive daily premeal INH or SC insulin for 12 wk (comparative phase), followed by SC insulin for 12 wk (washout phase).

MEASUREMENTS

Spirometry tests were conducted and insulin antibody levels were measured throughout the study. Acute insulin-induced changes in lung function were calculated as the difference between FEV1 before, and 10 and 60 min after, insulin.

MAIN RESULTS

There was a temporal dissociation between pulmonary function changes and insulin antibody generation. Small treatment group differences in changes in FEV1 from baseline, favoring SC insulin, were fully manifest by 2 wk of INH therapy, did not increase during the remainder of the comparative phase, and resolved within 2 wk of INH discontinuation. By contrast, insulin antibody levels remained low for the first 2 wk with INH, increased during Weeks 2 to 12, and gradually declined during washout. There was no evidence of acute insulin-induced alterations in lung function 10 and 60 min postinhalation.

CONCLUSION

The small lung function changes observed with INH therapy are not mediated by the humoral immune response, or associated with acute decrements in lung function immediately after insulin inhalation.