Maximal inspiratory and expiratory flow at moderate altitude: a study of a Latin American population.

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.

Risk factors associated with the detection of pulmonary emphysema in older asymptomatic respiratory subjects.

BACKGROUND: Several lung structural and functional abnormalities may occur associated with aging, including emphysema. In this study, we evaluated the frequency and risk factors associated with emphysema in respiratory asymptomatic individuals enrolled in our Lung Aging Program. From a cohort of 687 subjects, we found by high-resolution computed tomography (HRCT) 29 individuals (4%) with emphysematous changes that were compared with 87 controls (3:1) randomly selected from the same cohort. METHODS: This was a transversal, observational, case-control study where we examined demographics and functional characteristics, as well as telomere length and serum Klotho concentration, two conditions that have been associated with aging and some aging-associated diseases including emphysema. RESULTS: Individuals with subclinical pulmonary emphysema were older (72 ± 9 versus 67 ± 6 years), and primarily smoker males with low body mass index. Despite that they were asymptomatic, two of them exhibited a decrease of forced expiratory volume in 1 s (FEV1), with a lower FEV1/FVC suggesting airway obstruction. Cigarette smoking (OR = 5.43, CI95% 1.8-16.7), family history of lung disease (OR = 4.32, CI95% 1.0-19.0) and lower body mass index (OR 7.22, CI95% 1.2-3.5) were risk factors for the development of lung emphysematous changes. No association was found with telomere length and Klotho serum concentration. CONCLUSION: Our findings reveal that a small but important percentage of older people without respiratory symptoms, present pulmonary emphysema and indicate that smoking exposure and genetic background may contribute to etiological factors.

Screening Tool for Restrictive and Obstructive Ventilatory Abnormalities in a Population-Based Survey.

BACKGROUND: A 6 s spirometry with an inexpensive pocket spirometer efficiently selects individuals for a diagnostic-quality spirometry for airflow limitation, but could also be useful to identify individuals with a restrictive pattern. OBJECTIVES: We evaluated an inexpensive simplified spirometer (chronic obstructive pulmonary disease [COPD]-6) as a screening tool to identify spirometric abnormalities. METHODS: A population-based survey in Mexico City, with 742 participants performing pre- and post-BD spirometry and a three-maneuver 6 s spirometry (pre-BD) with a COPD-6. We evaluated forced expiratory volume in 1 s (FEV1), FEV6, and FEV1/FEV6 from the COPD-6, crude and expressed as the percentage of predicted (%P), to discriminate post-bronchodilator airflow obstruction (FEV1/forced vital capacity [FVC] < 5th percentile) or restriction (FVC or FEV1 <5th percentile with normal FEV1/FVC) through receiver operating characteristics and their area under the curve (AUC). RESULTS: FEV1%P was the best predictor to identify pre- and post-BD ventilatory abnormalities (best cutoff point 87%P, AUC 92% for restrictive pattern, 89% for obstructive pattern, and 91% for any spirometric abnormality). Deriving to clinical spirometry only those with < 87%P (26% of the sample) missed only 12% of spirometric abnormalities most of the latter mild. CONCLUSIONS: An FEV1 < 87%P from a pre-BD 6 s spirometry correctly identified individuals with spirometric ventilatory defects, either obstructive or restrictive.

[Inpatients days in patients with respiratory diseases and periodontal disease]. / Días de estancia hospitalaria (DEH) en pacientes con enfermedades respiratorias (ER) y enfermedad periodontal (EP).

INTRODUCTION: Periodontal disease is a chronic inflammatory gingival process that has been associated with the severity of respiratory diseases. In Mexico a prevalence of 78% was found in population with social security and > 60 years old. The aim of this study is to establish the association between periodontal disease and respiratory diseases according to the inpatient days. MATERIAL AND METHODS: A cross-sectional study was conducted from January to December 2011. We included hospitalized patients, ≥ 18 years of age, without sedation or intubated. A dentist classified patients into two groups according to the severity of the periodontal disease: mild-to-moderate and severe. We estimated medians of inpatient days by disease and severity. Negative binomial models were adjusted to estimate incidence rate ratios and predicted inpatient days. RESULTS: 3,059 patients were enrolled. The median of observed and predicted inpatient days was higher in the group of severe periodontal disease (p < 0.05). Patients with chronic obstructive pulmonary disease, tuberculosis, and influenza had the highest incidence rates ratios of periodontal disease (p < 0.05). CONCLUSIONS: The severity of periodontal disease is positively -associated with inpatient days of patients with respiratory diseases.

Effect of Passive Smoking on the Growth of Pulmonary Function and Respiratory Symptoms in Schoolchildren.

BACKGROUND: Environmental tobacco smoke affects the current and future health of children. OBJECTIVE: To determine whether schoolchildren aged 8-17 years old residing at an altitude of 2,240 m and exposed to tobacco smoke at home presented a reduction in the growth of pulmonary function and a greater problem of respiratory symptoms and infections compared with non-exposed children. MATERIALS AND METHODS: We followed, with questionnaires and spirometry, 1,632 boys and 1,555 girls from Mexico City and its metropolitan area (the Metropolitan Study to Evaluate the Chronic Effects of Pollution in School-age Children [EMPECE]) every six months for six years. The impact of passive smoking was estimated by mixed-effects models and Generalized Linear and Latent Mixed Models (GLLAMM), stratifying by gender and adjusting for age, height, weight, and ozone levels. RESULTS: Passive smoking (reported by one-half of participants) was associated with reduced spirometric lung function (log transformed or as Z-scores) and a higher frequency of self-reported respiratory symptoms and respiratory infections. Levels of forced expiratory volume in 1 second and forced vital capacity in individuals exposed to passive smoking were 6.8 and 14.1 ml, respectively, below those of non-exposed children, and these values decreased with increasing number of smokers at home and higher ozone levels. CONCLUSIONS: Passive smoking in children is a significant risk factor for respiratory disease and reduced lung function growth, which are additive with levels of air pollution, asthma, and the presence of respiratory symptoms.

Clinical Characteristics and Mortality of Influenza A H1N1 and Influenza-Like Illness in Mexico City in the 2013-2014 Winter Season.

BACKGROUND: The 2013-2014 influenza season in Mexico City was severe and mainly due to influenza A H1N1, as was the 2009 pandemic. OBJECTIVE: To describe features of the outbreak and to compare the characteristics of patients with and without viral identification. METHODS: We reviewed the medical charts of all individuals with influenza or influenza-like illness admitted to a referral hospital for respiratory diseases in Mexico City from January 2013 to March 2014, whether influenza virus was identified or not. RESULTS: We included 233 patients with influenza-like illness, 99 of whom had laboratory confirmed influenza; one-half of all patients required mechanical ventilation and 25% were admitted to the intensive care unit. Patients with confirmed influenza had a more severe disease than those without confirmation. A total of 52 (22.3%) patients died in hospital; survival was greater among patients hospitalized in the intensive care unit compared with those who remained in regular wards. CONCLUSIONS: Influenza A H1N1 continues to cause significant outbreaks in Mexico City. Patients with influenza-like illness had a similar clinical course regardless of laboratory confirmation of influenza, suggesting that their illness likely belonged to the same outbreak. Mechanical ventilation in regular hospital wards may be lifesaving, although the outcome is worse than at an intensive care unit.

[Prevalence of severe periodontal disease and its association with respiratory disease in hospitalized adult patients in a tertiary care center]. / Prevalencia de enfermedad periodontal grave (EPG) y su asociación con enfermedades respiratorias en pacientes adultos hospitalizados en un centro de tercer nivel.

BACKGROUND: Severe periodontal disease is a chronic inflammatory gingival process associated with systemic diseases. OBJECTIVE: To determine the prevalence of severe periodontal disease and its association with respiratory diseases among hospitalized patients at the Institute of Respiratory Diseases "Ismael Cosio Villegas" (INER) in 2011. MATERIAL AND METHODS: A cross-sectional study was developed. The severe periodontal disease was diagnosed by the Department of Stomatology. The International Classification of Diseases 10th revision was used. A multinomial logistic was fit to estimate relative-risk. RESULTS: Three thousand and fifty-nine patients were included; 772/3,059 (25.2%) had severe periodontal disease. After controlling for age, sex, inpatient days, death, and socioeconomic status, the infectious respiratory diseases that were significantly associated with severe periodontal disease were: HIV/AIDS (RR: 10.6; 95% CI: 9.1-23.3; p < 0.0001); pneumonia (RR: 2.6; 95% CI: 2.2-5.7; p < 0.0001); pulmonary tuberculosis and its sequels (RR: 2.1; 95% CI: 1.6-4.9; p < 0.0001); and lung abscess (RR: 2.6; 95% CI: 1.6-7.8; p = 0.002). Lung cancer and pleural diseases were also significantly associated with severe periodontal disease. CONCLUSIONS: High prevalence of severe periodontal disease was observed in the different respiratory diseases. Severe periodontal disease was associated with both infectious and non-infectious respiratory diseases. It is important to study an oral health intervention.

Obesity and pro-inflammatory mediators are associated with acute kidney injury in patients with A/H1N1 influenza and acute respiratory distress syndrome.

BACKGROUND: The obesity has been shown to increase the severity of A/H1N1 infection and the development of acute respiratory distress syndrome (ARDS) and organ involvement. METHODS: Circulating levels of C-peptide, insulin, glucagon, leptin, acute phase reactants (procalcitonin, C-reactive protein, tissue plasminogen activator, and serum amyloids A and P), were measured in samples from 32 critically ill patients with A/H1N1 virus infection, 17 of whom had ARDS complicated by acute kidney injury (AKI) and 15 of whom had ARDS but did not develop AKI. RESULTS: Patients with ARDS and AKI (ARDS/AKI) had higher BMI and higher levels of C-peptide, insulin, leptin, procalcitonin and serum amyloid A compared to those ARDS patient who did not develop AKI. Adjusting for confounding variables using logistic regression analysis, higher levels of C-peptide (>0.75 ng/mL) (OR=64.8, 95% CI = 2.1-1980, p = 0.0006) and BMI>30 Kg/m(2) (OR = 42.0, 95% CI = 1.2-1478, p = 0.04) were significantly associated with the development of AKI in ARDS patients. CONCLUSION: High levels of C-peptide and BMI>30 kg/m(2) were associated with the development of AKI in ARDS patients due to A/H1N1 infection. These metabolic/obesity indicators, together with the profiles of pro-inflammatory acute phase proteins, may be important links between obesity and poor outcomes in A/H1N1 09 infection.

Reply to: Height seems to be the only variable that determines lung oscillometry indices.

Age, sex and BMI, as well as height, should be used in IOS reference equations https://bit.ly/3VMUMLz.

Reference equations using segmented regressions for impulse oscillometry in healthy subjects aged 2.7-90 years.

Background: Published reference equations for impulse oscillometry (IOS) usually encompass a specific age group but not the entire lifespan. This may lead to discordant predicted values when two or more non-coincident equations can be applied to the same person, or when a person moves from one equation to the next non-convergent equation as he or she gets older. Thus, our aim was to provide a single reference equation for each IOS variable that could be applied from infancy to old age. Methods: This was an ambispective cross-sectional study in healthy nonsmokers, most of whom lived in Mexico City, who underwent IOS according to international standards. A multivariate piecewise linear regression, also known as segmented regression, was used to obtain reference equations for each IOS variable. Results: In a population of 830 subjects (54.0% female) aged 2.7 to 90 years (54.8% children ≤12 years), segmented regression estimated two breakpoints for age in almost all IOS variables, except for R5-R20 in which only one breakpoint was detected. With this approach, multivariate regressions including sex, age, height and body mass index as independent variables were constructed, and coefficients for calculating predicted value, lower and upper limits of normal, percentage of predicted and z-score were obtained. Conclusions: Our study provides IOS reference equations that include the major determinants of lung function, i.e. sex, age, height and body mass index, that can be easily implemented for subjects of almost any age.

[Adult asthma in Mexico City: a population-based study]. / Prevalencia y riesgos asociados con pacientes adultos con asma de 40 años o más de la Ciudad de México: estudio de base poblacional.

OBJECTIVES: To determine the prevalence of asthma and the association between sociodemographic characteristics, spirometry, respiratory symptoms, quality of life and sleep in adults > 40 years. MATERIALS AND METHODS: This report is part of our study (Latin American Research Project Obstructive Pulmonary), held in Mexico City and the metropolitan area in 2003. We used logistic regression models adjusted for study design, where asthma was the dependent and independent variable respiratory symptoms, sociodemographic and clinical characteristics among others. RESULTS: The prevalence of physician-diagnosed asthma was: 3.3% in men and 6.2% in women. Decreased lung function in asthmatics was observed. In multivariate analysis, after adjusting for potential confounders, asthmatics had a higher risk of excessive daytime sleepiness more snoring [OR = 3.2 (95% CI 1.4-7.4), p= 0.008], and more frequent work absences due to respiratory problems [OR = 5.1 (95% CI 2.5-10.4), p<0.0001]. CONCLUSIONS: The prevalence of asthma was 5%. Asthmatics showed lower quality of life and lung function.

Risk of Pulmonary Fibrosis and Persistent Symptoms Post-COVID-19 in a Cohort of Outpatient Health Workers.

Background: Infection by SARS-CoV-2 has been associated with multiple symptoms; however, still, little is known about persistent symptoms and their probable association with the risk of developing pulmonary fibrosis in patients post-COVID-19. Methods: A longitudinal prospective study on health workers infected by SARS-CoV-2 was conducted. In this work, signs and symptoms were recorded of 149 health workers with a positive PCR test for SARS-CoV-2 at the beginning of the diagnosis, during the active infection, and during post-COVID-19 follow-up. The McNemar chi-square test was used to compare the proportions and percentages of symptoms between the baseline and each follow-up period. Results: The signs and symptoms after follow-up were cardiorespiratory, neurological, and inflammatory. Gastrointestinal symptoms were unusual at the disease onset, but unexpectedly, their frequency was higher in the post-infection stage. The multivariate analysis showed that pneumonia (HR 2.4, IC95%: 1.5−3.8, p < 0.001) and positive PCR tests still after four weeks (HR 5.3, IC95%: 2.3-12.3, p < 0.001) were factors associated with the diagnosis of post-COVID-19 pulmonary fibrosis in this study group. Conclusions: Our results showed that pneumonia and virus infection persistence were risk factors for developing pulmonary fibrosis post-COVID-19, after months of initial infection.

Offline exhaled nitric oxide in children: chemiluminescence vs. electrochemical devices.

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.

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.

Determination of the phenotypic age in residents of Mexico City: effect of accelerated ageing on lung function and structure.

INTRODUCTION: Phenotypic age better represents age-related biological dysregulation than chronological age. Recently, a multisystem-based ageing measure, which integrates chronological age and nine biomarkers, was proposed. METHODS: Phenotypic age was determined in 774 residents of Mexico City over 60 years old and without respiratory problems. We arbitrarily classified as "accelerated" ageing, those showing >4 years compared with their chronological age, and "slowed" ageing, those with <4 years compared with chronological age. Demographic risk factors were analysed with structured questionnaires. Lung structure was evaluated by high-resolution computed tomography and functional competence was analysed by forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), diffusion capacity of carbon monoxide (D LCO), and the 6-minute walk test (6MWT). RESULTS: Overall, 13% of this cohort showed accelerated ageing, which was corroborated with four independent biomarkers of ageing, 42% had normal ageing and 46% had slowed ageing. Risk factors associated with accelerated ageing were male sex (OR 4.4, 95% CI 2.4-7.9; p<0.01), diabetes mellitus (OR 9.7, 95% CI 5.5-17.2; p<0.01), and long-term sleep duration (OR 2.9 95% CI 1.34-6.35, p<0.01). Among smokers, there was a slight but significant association with the number of pack-years. Subjects with accelerated ageing showed decreased FVC (p<0.0001), FEV1 (p<0.0001), D LCO (p<0.02) and walking distance in the 6MWT (p=0.0001). Slowed-ageing subjects presented less frequently with emphysematous lesions compared with those with accelerated ageing. CONCLUSIONS: A small but significant proportion of residents of Mexico City age rapidly, which is associated with male sex, diabetes, and long-term sleep duration. They exhibit lower levels of lung function and develop emphysema more frequently.

[Clinical pathological study of craniopharyngioma. Fifteen years at the National Institute of Neurology and Neurosurgery "Manuel Velasco Suárez"]. / Craneofaringioma, estudio clínico-patológico. Quince años del Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez".

BACKGROUND: Craniopharyngioma is a sellar region benign cyst It's frequency ranges from 1.2% to 4.6% of all brain tumors. OBJECTIVE: To carry out a clinical pathological correlation of craniopharyngioma among adults and describe the tumor's biological characteristics. METHODS: We included 115 craniopharyngiomas; 100 were adamantimomatous and 15 were papillary type. Patient's age range was 15-90 years (mean 52.5 yrs); 54 (47%) were males and 61 (53%) females. The most frequent location was the supraselar region in 49 (42.6%) of cases. Total exeresis was performed in 72 patients (62.6%) and partial exeresis in 43 (37.4%). RESULTS: We noted a recurrence among 50 patients (43%), of which 5/15 were papillary and 45/100 adamantinomatous. The mean patient age for recurrent tumors was 50.46+/-14.13yrs and 48.65+/-11.95 for non recurrent tumors. Thirteen patients died (11.3%). We observed a statistical correlation between recurrence, exeresis (p=0.014), and death (p=0.047). Follow-up was longer among females than males and in suprasellar tumor location, papillary type, external epithelium cysts and laxo stellate reticulum. CONCLUSIONS: However a good prognostic factor in craniopharyngiomas was observed in older female patients with complete exeresis, small tumors, external epithelium cysts, edematous stroma, inflammation, and absence of atypical cell and mitosis.

Quality of Pulmonary Function Tests in Participants with Down Syndrome.

INTRODUCTION: People with Down syndrome (DS) have high respiratory morbidity, evaluating their respiratory health with standardized, objective tests is desirable. Thus, the objective of this study was to evaluate the technical quality of Pulmonary Function Tests (PFTs) to determine which ones are most suitable for this population. METHODS: Participants included children, teenagers and adults with DS, 5 years of age or older (n=302). The technical quality of the impulse oscillometry system (IOS), forced spirometry, lung-diffusing capacity for carbon monoxide (DLCO), and 6-min walk test (6MWT) were analyzed by age group. Capnography and pulse oximetry were included in the study. Technical quality was determined on the basis of current international PFTs standards. RESULTS: Fifty-one percent of participants were males. A total of 184 participants (71%) who completed the IOS fulfilled the quality criteria, while 210 (70%) completed the 6MWT. Performance on forced spirometry and DLCO was poor. All pulse oximetries and 96% percent heart rates obtained had good quality, but exhaled carbon dioxide (PetCO2) and respiratory rate (RR) showed deficient repeatability. CONCLUSIONS: IOS appears to be the most reliable instrument for evaluating lung mechanics in individuals with DS.

Inspiratory Capacity and Vital Capacity of Healthy Subjects 9-81 Years of Age at Moderate-High Altitude.

BACKGROUND: Measurements of inspiratory capacity (IC) and vital capacity (VC) are used to recognize dynamic hyperinflation, but appropriate reference values are required to achieve accurate clinical interpretations. Altitude above sea level is a potential determining factor for lung volumes, including IC and VC. OBJECTIVE: To describe IC and VC for healthy people who live in Mexico City at an altitude of 2,240 m above sea level. METHODS: Healthy subjects ages 9-81 y completed slow spirometry by following 2005 American Thoracic Society/European Respiratory Society standards. Once associations were explored, linear regression models were constructed and values were compared with those from previously published equations. RESULTS: A total of 441 healthy subjects (55.1% women) participated. The mean age was 32 y (minimum age, 9 y; maximum age, 81 y). IC and VC measurements were associated with sex, age, height, and weight. An accelerated increase in IC and VC was evident from 9 to 20 y of age, followed by a gradual decrease in both sexes. In general, IC was higher in our population than predicted by previously published reference equations. CONCLUSIONS: IC in healthy people at 2,240 m above sea level was higher than that of previous reports about European and Latin-American subjects of the same height, sex, and age who were at sea level. The present study provided robust reference values for persons who lived at a moderate altitude.

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.