Of the need to reconcile discrepancies between two different reference equations for combined single-breath D LNO-D LCO in systemic sclerosis

Cardiac Fatigue in Male Athletes with Exercise-Induced Pulmonary Impairments After a Very Long-Distance Triathlon

INTRODUCTION

Prolonged strenuous exercise can transiently decrease cardiac function. Other studies have identified three major exercise-induced pulmonary changes: bronchoconstriction, dynamic hyperinflation and pulmonary oedema with reduced alveolar-capillary membrane diffusing capacity. This study investigated whether athletes with one of these pulmonary dysfunctions following a very long-distance triathlon exhibit similar cardiac alterations as those without dysfunctions.

METHODS

Sixty trained male triathletes (age 39 ± 9 years) underwent baseline and post-race assessments, including echocardiography (with standard, 2D-strain and myocardial work assessments), spirometry and double-diffusion technique to evaluate alveolar-capillary membrane diffusing capacity for carbon monoxide (DMCO). Cardiac function in athletes with exercise-induced bronchoconstriction (> 10% decrease FEV1), dynamic hyperinflation (> 10% decrease inspiratory capacity) or impaired diffusion capacity (> 20% decrease DMCO/alveolar volume) were compared with those without these dysfunctions.

RESULTS

The race lasted 14 h 20 min ± 1 h 26 min. Both systolic and diastolic cardiac functions declined post-race. Post-race, 18% of athletes had bronchoconstriction, 58% dynamic hyperinflation and 40% impaired diffusing capacity. Right and left ventricular standard and 2D-strain parameters were similar before the race in all subgroups and changed similarly post-race, except E/E', which decreased in the bronchoconstriction subgroup and increased in those with diffusion impairment. Global constructive work decreased by ~ 19% post-race (2302 ± 226 versus 1869 ± 328 mmHg%, P < 0.001), more pronounced in athletes with diffusion impairment compared with others (- 26 ± 13 versus - 15 ± 9%, P = 0.001) and positively correlated with DMCO/alveolar volume reduction.

CONCLUSION

After a very long-distance triathlon, bronchoconstriction and hyperinflation were not associated with significant cardiac changes, whereas impaired alveolar-capillary membrane diffusing capacity was associated with a more significant decline in myocardial function. These findings highlight the complex relationship between pulmonary gas exchange abnormalities and cardiac fatigue following prolonged strenuous exercise.

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.

Lung diffusing capacity for nitric oxide measured by two commercial devices: a randomised crossover comparison in healthy adults

In Europe, two commercial devices are available to measure combined single-breath diffusing capacity of the lung for nitric oxide (D_LNO) and carbon monoxide (D_LCO) in one manoeuvre. Reference values were derived by pooling datasets from both devices, but agreement between devices has not been established.

We conducted a randomised crossover trial in 35 healthy adults (age 40.0±15.5 years, 51% female) to compare D_LNO (primary end-point) between MasterScreen™ (Vyaire Medical, Mettawa, IL, USA) and HypAir (Medisoft, Dinant, Belgium) devices during a single visit under controlled conditions. Linear mixed models were used adjusting for device and period as fixed effects and random intercept for each participant.

Difference in D_LNO between HypAir and MasterScreen was 24.0 mL·min⁻¹·mmHg⁻¹ (95% CI 21.7–26.3). There was no difference in D_LCO (−0.03 mL·min⁻¹·mmHg⁻¹, 95% CI −0.57–0.12) between devices while alveolar volume (V_A) was higher on HypAir compared to MasterScreen™ (0.48 L, 95% CI 0.45–0.52). Disparity in the estimation of V_A and the rate of NO uptake (K_NO=D_LNO/V_A) could explain the discrepancy in D_LNO between devices. Disparity in the estimation of V_A and the rate of CO uptake (K_CO=D_LCO/V_A) per unit of V_A offset each other resulting in negligible discrepancy in D_LCO between devices. Differences in methods of expiratory gas sampling and sensor specifications between devices likely explain these observations.

These findings have important implications for derivation of D_LNO reference values and comparison of results across studies. Until this issue is resolved, reference values, established on the respective devices, should be used for test interpretation.

Large discrepancies between commercial devices to measure single-breath diffusing capacity of the lung for nitric oxide in healthy subjects caution against pooling or direct comparison of measurements obtained using different protocols and deviceshttps://bit.ly/3vKyF7U