Effect of Altitude on Respiratory Functional Status in COVID-19 Survivors: Results from a Latin American Cohort-FIRCOV.

Laura Gochicoa-Rangel, Santiago C. Arce, Carlos Aguirre-Franco, Wilmer Madrid-Mejía, Mónica Gutiérrez-Clavería, Lorena Noriega-Aguirre, Patricia Schonffeldt-Guerrero, Agustín Acuña-Izcaray, Arturo Cortés-Telles, Luisa Martínez-Valdeavellano, Federico Isaac Hernández-Rocha, Omar Ceballos-Zúñiga, Rodrigo Del Rio Hidalgo, Sonia Sánchez, Erika Meneses-Tamayo, and Iván Chérrez-Ojeda; and on Behalf of the Respiratory Physiology Project in COVID-19 (FIRCOV). Effect of altitude on respiratory functional status in COVID-19 survivors: results from a Latin American Cohort-FIRCOV. High Alt Med Biol 24:37-48, 2023. Persistent symptoms and lung function abnormalities are common in COVID-19 survivors. Objectives: To determine the effect of altitude and other independent variables on respiratory function in COVID-19 survivors. Methods: Analytical, observational, cross-sectional cohort study done at 13 medical centers in Latin America located at different altitudes above sea level. COVID-19 survivors were invited to perform pulmonary function tests at least 3 weeks after diagnosis. Results: 1,368 participants (59% male) had mild (20%), moderate (59%), and severe (21%) disease. Restriction by spirometry was noted in 32%; diffusing capacity of the lung for carbon monoxide (DLCO) was low in 43.7%; and 22.2% walked less meters during the 6-minute walk test (6-MWT). In multiple linear regression models, higher altitude was associated with better spirometry, DLCO and 6-MWT, but lower oxygen saturation at rest and during exercise. Men were 3 times more likely to have restriction and 5.7 times more likely to have a low DLCO. Those who had required mechanical ventilation had lower DLCO and walked less during the 6-MWT. Conclusions: Men were more likely to have lower lung function than women, even after correcting for disease severity and other factors. Patients living at a higher altitude were more likely to have better spirometric patterns and walked farther but had lower DLCO and oxygen saturation.

Comparing Spirometric Reference Values From Childhood to Old Age Estimated by LMS and Linear Regression Models.

BACKGROUND: Proper reference values for lung function testing are essential for achieving adequate interpretations. The LMS procedure (lambda, mu, sigma) permits continuous analyses of entire populations avoiding gaps in the transition between childhood and adulthood. It also allows more precise calculations of average values, dispersion, and 5th percentiles, which are usually considered the lower limit of normality. The objective of this study was to compare our results fitted with the LMS method with standard multiple linear regression, and with those from international Global Lung Function Initiative (GLI) equations. METHODS: Data from 9835 healthy residents of the metropolitan area of Mexico City aged 8-80 years were compiled from several studies: EMPECE, PLATINO, adult Mexican workers and two unpublished studies. The LMS procedure and multiple linear regression models were fit to obtain reference equations using R software. RESULTS: Residuals from the LMS models had a median closer to zero, and smaller dispersion than those from the linear model, but differences although statistically significant were very small and of questionable practical relevance. For example, for females and ln(FEV1), median residual was -0.001 with p25 of -0.08 and p75 of 0.08 for LMS, compared with 0.004 (-0.08, 0.09) [p<0.05] for the linear model. Average spirometric values for a given height for our population, were higher than those predicted by the GLI study. CONCLUSION: Continuous reference equations for the Mexican population calculated using the LMS technique showed slightly better fit than linear regression models.

Diffusing Capacity of the Lung for Carbon Monoxide in Mexican/Latino Children. Quality Control and Reference Values.

RATIONALE: Single-breath diffusing capacity of the lung for carbon monoxide (DlCOsb) values are used to evaluate gas exchange; however, the quality of maneuvers performed by children has not been evaluated, and reference values for young people living at moderate altitudes are not well established. OBJECTIVES: Our objectives were 1) to determine whether DlCOsb maneuvers performed by a pediatric population would meet 2017 European Respiratory Society/American Thoracic Society (ERS/ATS) quality control standards; and 2) to report normal DlCOsb values for Mexican/Latino children and adolescents living at moderate altitudes. METHODS: This study involved healthy young people 4-20 years of age from the metropolitan area of Mexico City (2,240 m above sea level) who were recruited in schools from July 2014 to August 2017. DlCOsb testing was performed according to the 2005 ATS/ERS standards, and the quality control of each maneuver was analyzed according to the 2017 ERS/ATS standards. We constructed models for DlCOsb with linear and quadratic terms for weight, height, and age as independent variables using shrinkage statistics, variance inflation factors, the Akaike information criterion, and R2 to compare the results of different models. RESULTS: Results were obtained for 420 individuals (53% boys) with a mean age of 11.7 ± 4.5 standard deviation (SD) years; 47% of maneuvers from children age 4-6 years were grade A (13% grade B), and 90% of those in children older than 13 years were grade A or B. Forty-six percent of the subjects had a DlCOsb repeatability of <1 ml/min/mm Hg. The mean DlCOsb was higher for boys than for girls (32.4 ± 13.6 [SD] vs. 24.1 ± 7.5 ml/min/mm Hg, respectively). The reference equation for boys was DlCOsb = exp(1.63469 + [0.03251 × age] + [0.00846 × height] + [0.00304 × weight]), R2 = 0.87; for girls, the best equation was DlCOsb = exp(1.56516 + [0.0193 × age] + [0.00893 × height] + [0.00273 × weight]), R2 = 0.75. The single-breath transfer coefficient of the lung for carbon monoxide remained constant with age and height, with a lower limit of normal of 6.5 ml/min/mm Hg/L in boys and 5.4 ml/min/mm Hg/L in girls. Measured DlCOsb was higher than predicted by other authors (P < 0.001 by paired t test). CONCLUSIONS: Individuals 4-20 years of age can complete high-quality DlCOsb tests. Children and adolescents living at 2,240 m have higher DlCOsb values than those living at sea level. Reference equations for DlCOsb obtained at sea level are poor predictors of the values measured at moderate altitude.

Prueba de toxitoide tetánico: Evaluación del estado inmunológico de pacientes con estado nutricional adecuado versus pacientes con desnutrición / Tetanus toxoid test: inmunologic states of patients who were well nourished versus malnourished children

Guatemala es uno de los países con cifras más altas de desnutrición infantil. Diversos estudios sugieren una relación significativa entre el estado nutricional y el riesgo de padecer infecciones. Las pruebas de hipersensibilidad tardía son útiles para evaluar la inmunidad celular, un agente que puede utilizarse para ello es el toxoide tetánico.