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OBJECTIVES: This study aimed to evaluate pulmonary diffusing capacity for nitric oxide (DLNO) and pulmonary diffusing capacity for carbon monoxide (DLCO) in Mexican Hispanics born and raised at 2240 m altitude (midlanders) compared with those born and raised at sea level (lowlanders). It also aimed to assess the effectiveness of race-specific reference equations for pulmonary diffusing capacity (white people vs Mexican Hispanics) in minimising root mean square errors (RMSE) compared with race-neutral equations. METHODS: DLNO, DLCO, alveolar volume (VA) and gas transfer coefficients (KNO and KCO) were measured in 392 Mexican Hispanics (5 to 78 years) and compared with 1056 white subjects (5 to 95 years). Reference equations were developed using segmented linear regression (DLNO, DLCO and VA) and multiple linear regression (KNO and KCO) and validated with Least Absolute Shrinkage and Selection Operator. RMSE comparisons between race-specific and race-neutral models were conducted using repeated k-fold cross-validation and random forests. RESULTS: Midlanders exhibited higher DLCO (mean difference: +4 mL/min/mm Hg), DLNO (mean difference: +7 mL/min/mm Hg) and VA (mean difference: +0.17 L) compared with lowlanders. The Bayesian information criterion favoured race-specific models and excluding race as a covariate increased RMSE by 61% (DLNO), 18% (DLCO) and 4% (KNO). RMSE values for VA and KCO were comparable between race-specific and race-neutral models. For DLCO and DLNO, race-neutral equations resulted in 3% to 6% false positive rates (FPRs) in Mexican Hispanics and 20% to 49% false negative rates (FNRs) in white subjects compared with race-specific equations. CONCLUSIONS: Mexican Hispanics born and raised at 2240 m exhibit higher DLCO and DLNO compared with lowlanders. Including race as a covariate in reference equations lowers the RMSE for DLNO, DLCO and KNO and reduces FPR and FNR compared with race-neutral models. This study highlights the need for altitude-specific and race-specific reference equations to improve pulmonary function assessments across diverse populations.

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Background.Lung volumes can be measured by body plethysmography (BP), by inert gas dilution during a single-breath or multiple breaths and by radiographic methods based on chest roentgenogram or CT scanning. Our objective was to analyze the concordance between several methods including a new pressure-derived method (PDM) in a variety of pulmonary conditions.Methods. We recruited four groups of adult volunteers at the chronic obstructive pulmonary disease and tobacco clinic of a respiratory referral hospital: patients with lung bullae, with obstructive lung diseases, with restrictive lung diseases and healthy controls; all subjects underwent lung volume measurements according to ATS/ERS standards in random order with each method and then CT scanning. Differences among groups were estimated by Kruskal-Wallis tests. Concordance correlation coefficients (CCC) and Bland-Altman plots were performed.Results. Sixty-two patients were studied including 15 with lung bullae, 14 with obstructive lung diseases, 12 with restrictive lung disease and 21 healthy subjects. Highest concordance was obtained between BP and CT scanning (CCC 0.95, mean difference -0.35 l) and the lowest, with TLC-DLCOsb(CCC 0.65, difference -1.05 l). TLC measured by BP had a moderate concordance with the PDM (CCC = 0.91, mean difference -0.19 l). The PDM on the other hand had the lowest intra-test repeatability (2.7%) of all tested methods.Conclusions. Lung volumes measured by BP and CT had high concordance in the scenario of varied pulmonary conditions including lung bullae, restrictive and obstructive diseases. The new PDM device, had low intra-test variability, and was easy to perform, with a reasonable concordance with BP.

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BACKGROUND: Peak inspiratory and expiratory flows (PIF, PEF) are parameters used to evaluate the mechanics of the respiratory system. These parameters can vary based on whether they are measured using mechanical devices vs. spirometry and based on the barometric pressure at which the measurements are obtained. Our objectives were (1) to report the normal values and variability of PEF and PIF of a Latin American population living at a moderate altitude (2240 m above sea level), (2) to analyze the adjustment of reference values obtained at sea level with those obtained in healthy subjects living at a moderate altitude, and (3) to assess the correlation between PEF obtained by spirometry (PEFs) and PEF obtained by mechanical devices (PEFm). METHODS: In this prospective and transversal study, men and women with good respiratory health aged between 2.8 and 68 years old were invited to participate. Randomly, they underwent spirometry (to measure PEFs and PIFs) and mechanical flowmetry (to measure PEFm). RESULTS: A total of 314 subjects participated, with an average age of 24.3 ± 16.4 years; 59% were Women. The main determinants for the reference equations were age, weight, height and sex at birth. The agreement of the PEFm, PEFs and PIFs values was inconsistent with that reported by other authors, even at the same barometric pressure. The association between PEFm and PEFs was r = 0.91 (p < 0.001), and the correlation coefficient of concordance was 0.84. CONCLUSIONS: The PEFm, PEFs, and PIFs measurements in individuals living at moderate altitudes are different from those found by other authors in cities with different barometric pressures and ethnicities.

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Abstract Background: Exhaled nitric oxide (eNO) is a noninvasive marker of airway inflammation that has been used in children, using the "offline" technique. To the extent of our knowledge, no article reported in literature compares the concordance and correlation between the two different technologies used to measure eNO at tidal volume offline. This study aimed to report the concordance and correlation of the eNO measured "offline" at tidal volume, using chemioluminiscence (cl) vs electrochemical devices (eq). Methods: A cross-sectional, observational, and prospective study was conducted in the National Institute of Respiratory Diseases (Instituto Nacional de Enfermedades Respiratorias), Mexico City. Healthy children and those with a lung disease between 1 and 11 years of age were included. The exhaled air sample at tidal volume was obtained by attaching a mask connected to a Mylar® bag. Results: We studied 36 children. The mean ± standard deviation (SD) age of the study population was 6 ± 2.6 years; 25% of the subjects included were healthy, and the rest had a lung disease. The concordance correlation coefficient between the two measuring devices was 0.98 (p < 0.001), with a mean difference of 1.46 ± 3.5 ppb and 95% limits of agreement from -5.3 ppb to 8.3 ppb. The linear regression model equation for the estimation of eNO was eNOcl = (eNOeq·1.0718) - 0.1343 (r2 = 0.97). Conclusions: The measurement of eNO at tidal volume by the offline method can be analyzed by electrochemical devices, and the results are interchangeable with those analyzed by chemiluminescence technology.

Resumen Introducción: El óxido nítrico exhalado (eNO) es un marcador no invasivo de inflamación de la vía aérea que se ha utilizado en niños mediante técnica «fuera de línea¼. Por lo que sabemos, en la literatura no existen reportes que comparen la concordancia y la correlación entre dos técnicas diferentes a volumen corriente. El objetivo de este trabajo es informar la concordancia y la correlación del eNO obtenido por la técnica fuera de línea a volumen corriente en los equipos de quimioluminiscencia (cl) y electroquímico (eq). Métodos: Se realizó un estudio transversal, observacional y prospectivo en el Instituto Nacional de Enfermedades Respiratorias, en Ciudad de México. Se incluyeron niños sanos y con enfermedad pulmonar de 1-11 años de edad. La muestra de aire exhalado se obtuvo a volumen corriente mediante una máscara con conexión a una bolsa de Mylar®. Resultados: Se estudiaron 36 niños. La edad promedio con su desviación estándar de la población de estudio fue de 6 ± 2.6 años. El 25% de los sujetos incluidos estaban sanos y el resto tenían alguna enfermedad pulmonar. El coeficiente de correlación de concordancia entre los dos equipos fue de 0.98 (p < 0.001), con una diferencia media de 1.46 ± 3.5 ppb y unos límites de concordancia del 95% de −5.3 a 8.3 ppb. La ecuación del modelo de regresión lineal del eNO fue eNOcl = (eNOeq·1,0718) − 0.1343 (r2 = 0.97). Conclusiones: La medición del eNO por el método fuera de línea a volumen corriente puede analizarse en dispositivos electroquímicos. Los resultados son intercambiables con los de quimioluminiscencia.

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Background: Exhaled nitric oxide (eNO) is a noninvasive marker of airway inflammation that has been used in children, using the "offline" technique. To the extent of our knowledge, no article reported in literature compares the concordance and correlation between the two different technologies used to measure eNO at tidal volume offline. This study aimed to report the concordance and correlation of the eNO measured "offline" at tidal volume, using chemioluminiscence (cl) vs electrochemical devices (eq). Methods: A cross-sectional, observational, and prospective study was conducted in the National Institute of Respiratory Diseases (Instituto Nacional de Enfermedades Respiratorias), Mexico City. Healthy children and those with a lung disease between 1 and 11 years of age were included. The exhaled air sample at tidal volume was obtained by attaching a mask connected to a Mylar® bag. Results: We studied 36 children. The mean ± standard deviation (SD) age of the study population was 6 ± 2.6 years; 25% of the subjects included were healthy, and the rest had a lung disease. The concordance correlation coefficient between the two measuring devices was 0.98 (p < 0.001), with a mean difference of 1.46 ± 3.5 ppb and 95% limits of agreement from -5.3 ppb to 8.3 ppb. The linear regression model equation for the estimation of eNO was eNOcl = (eNOeq·1.0718) - 0.1343 (r2 = 0.97). Conclusions: The measurement of eNO at tidal volume by the offline method can be analyzed by electrochemical devices, and the results are interchangeable with those analyzed by chemiluminescence technology.

Introducción: El óxido nítrico exhalado (eNO) es un marcador no invasivo de inflamación de la vía aérea que se ha utilizado en niños mediante técnica «fuera de línea¼. Por lo que sabemos, en la literatura no existen reportes que comparen la concordancia y la correlación entre dos técnicas diferentes a volumen corriente. El objetivo de este trabajo es informar la concordancia y la correlación del eNO obtenido por la técnica fuera de línea a volumen corriente en los equipos de quimioluminiscencia (cl) y electroquímico (eq). Métodos: Se realizó un estudio transversal, observacional y prospectivo en el Instituto Nacional de Enfermedades Respiratorias, en Ciudad de México. Se incluyeron niños sanos y con enfermedad pulmonar de 1-11 años de edad. La muestra de aire exhalado se obtuvo a volumen corriente mediante una máscara con conexión a una bolsa de Mylar®. Resultados: Se estudiaron 36 niños. La edad promedio con su desviación estándar de la población de estudio fue de 6 ± 2.6 años. El 25% de los sujetos incluidos estaban sanos y el resto tenían alguna enfermedad pulmonar. El coeficiente de correlación de concordancia entre los dos equipos fue de 0.98 (p < 0.001), con una diferencia media de 1.46 ± 3.5 ppb y unos límites de concordancia del 95% de −5.3 a 8.3 ppb. La ecuación del modelo de regresión lineal del eNO fue eNOcl = (eNOeq·1,0718) − 0.1343 (r2 = 0.97). Conclusiones: La medición del eNO por el método fuera de línea a volumen corriente puede analizarse en dispositivos electroquímicos. Los resultados son intercambiables con los de quimioluminiscencia.

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BACKGROUND: Persistent impairment of pulmonary function and exercise capacity has been known to last for months or even years in the survivors who recovered from other coronavirus pneumonia. Some reports showed that subjects with coronavirus disease 2019 pneumonia after being discharged could have several sequelae, but there are few studies on gas exchange and exercise capacity complications in these subjects. AIMS: To describe residual gas exchange abnormalities during recovery from coronavirus disease 2019 pneumonia. METHODS: In an observational study, ∼90 d after onset of disease, we scheduled almost 200 subjects for an out-patient visit with pulmonary function testing and computed tomography of the lungs. Lung mechanics by using body plethysmography, gas exchange with diffusing lung capacity for carbon monoxide determined by the single-breath technique (DLCOsb) and diffusing lung capacity for nitric oxide determined by the single-breath technique (DLNOsb), and exercise ability by using the 6-min walk test (6MWT) were measured in the subjects. The results were compared between those who required invasive mechanical ventilation and those who did not. RESULTS: A total of 171 subjects were included, the majority (96%) had signs of residual pneumonia (such as an excess of high attenuation areas) on computed tomography of the lungs. The DLCOSB results were below the lower limit of the normal range in 29.2% of the subjects; during the 6MWT, 67% experienced oxygen desaturation ([Formula: see text]) > 4%; and, in 81 (47%), the dropped below 88%. Subjects who required invasive mechanical ventilation (49.7%) were more likely to have lower lung volumes, more gas exchange abnormality, less exercise capacity and more radiologic abnormality. CONCLUSIONS: Subjects who recovered from severe COVID-19 pneumonia continued to have abnormal lung function and abnormal radiologic findings.

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The pandemic character of coronavirus disease-19 (COVID-19) requires strategy changes designed to guarantee the safety of patients and health-care professionals. We are greatly concerned by the limitations in the operation of pulmonary function test (PFT) laboratories, since there is a high risk of disease progression in patients with chronic pulmonary diseases, and we are now faced by the influx of a new group of individuals in the recovery phase of post-COVID-19-syndrome that requires evaluation and follow-up of their respiratory function. To reestablish the operation of PFT laboratories limiting the risk of cross-contamination, we herein present the consensus reached by a group of experts in respiratory physiology, most of whom work in PFT laboratories in several Latin American countries, on the applicable recommendations for severe acute respiratory syndrome coronavirus 2 pneumonia survivors when undergoing PFT. We present the safety and hygiene measures that must be adopted in laboratories or centers where PFT is conducted in adults and/or children. These recommendations answer the following questions: which PFT is most recommended in subjects that have recovered from COVID-19; what quality control and safety measures should PFT laboratories implement during this pandemic? And how should we approach non-COVID-19 patients requiring PFT?