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.

Implementation of an Integrated Total Quality Management System in a Pulmonary Function Laboratory.

BACKGROUND AND OBJECTIVES: A worldwide objective in the area of health is to offer high-quality services supported by certification strategies that contribute to improving standards for processes commonly used in medicine. However, few pulmonary function test laboratories (PFTLs) follow official standards in their daily operations or are organized around an integrated total quality management system (ITQMS) focused on their established processes. The aim was to determine the feasibility of implementing an ITQMS to accredit the International Organization for Standardization (ISO) 9001:2015 standard in a high-demand PFTL where 13 respiratory function tests are routinely performed together with teaching and research activities. METHODS: This project was conducted at the PFTL of the Instituto Nacional de Enfermedades Respiratorias in Mexico City from November 2014 to August 2017 and involved the implementation of an ITQMS guided by ISO 9001:2015 in 5 phases: (1) the establishment of a work team; (2) the elaboration of situational diagnoses; (3) the development of guidelines for the ITQMS; (4) the implementation of the ITQMS model; and (5) the evaluation of the ITQMS. RESULTS: Upon completing the 5 phases, an evaluation of the system by an internal audit identified 3 minor cases of nonconformity (NC), while additional observations and an external audit found 5 minor cases of NC. These issues were addressed through a root-cause analysis to establish an action plan for each one. At the end of the process, the institution was granted the ISO 9001:2015 certification for its 3 processes: medical attention in support of diagnoses, teaching, and research. CONCLUSIONS: It is possible to implement an ISO quality management system as a routine operating methodology in a high-demand PFTL.

Gas Exchange Impairment During COVID-19 Recovery.

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.

Functional Respiratory Evaluation in the COVID-19 Era: The Role of Pulmonary Function Test Laboratories.

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?

Shorter corridors can be used for the six-minute walk test in subjects with chronic lung diseases.

BACKGROUND: The main limitation of the six-minute walk test (6-MWT) is that not all pulmonary function testing facilities have an indoor flat, 30-m-long corridor. Therefore, this study aimed 1) to evaluate the correlation and agreement of the distances walked in 30-m- vs. 15-m-long corridors by subjects with chronic lung diseases (CLD group) and 2) to compare the levels of oxygen saturation (nSpO2), blood pressure (BP), heart rate recovery at minute one post-exercise (HRR1), and Borg scale scores for dyspnea and fatigue between the two distances walked. METHODS: A prospective, cross-sectional study was conducted at the National Institute of Respiratory Diseases in Mexico City. Subjects with chronic lung diseases and healthy adults were invited to participate. The distance of the 6-MWT was randomly assigned based on whether the first test was in the 15-m or 30-m corridor. RESULTS: Ninety individuals were included; the correlation in meters walked between the two corridors was r = 0.96 in CLD; the 95% limits of agreement for the 6-MWT ranged from -73 to +37 m. Most subjects walked further in the 30-m corridor (82%); however, the percent predicted values for the CLD group were 3.5% lower for the 15-m corridor than the 30-m corridor. Only 10.5% of the subjects with CLD would have been falsely classified as having a normal 6-MWT (false negative). No significant differences in the nSpO2, Borg scale, BP or HRR1 were found between the two 6-MWT corridor lengths. CONCLUSION: The 6-MWT can be performed using a 15-m corridor in subjects with CLD, and the results for the distance walked, HRR1, nSpO2, and Borg scale scores are similar to between the 15-m and 30-m corridors.

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.

Estandarización de la oscilometría de impulso y generación de ecuaciones piloto para generar valores de referencia en el Hospital Central Militar / Standardization of impulse oscillometry and the generation of pilot equations to generate reference values in the Central Military Hospital

Resumen Introducción La oscilometría de impulso es una prueba que evalúa la mecánica respiratoria a través de la aplicación de pequeños pulsos de presión que producen oscilaciones de flujo a una frecuencia determinada. Su aplicación relevante es en el estudio de las enfermedades de la vía aérea pequeña. El software integrado al equipo que ejecuta esta prueba genera cálculos de valores predictivos para cada uno de los parámetros oscilométricos, los cuales se basan en datos de población alemana. Objetivo Estandarizar la prueba de oscilometría de impulso y obtener ecuaciones piloto para valores de referencia. Material y métodos Se realizó un estudio experimental, analítico, prospectivo y longitudinal con sujetos voluntarios sanos. Se llevaron a cabo pruebas de espirometría y oscilometría de impulso basales y, tras broncodilatador, se registraron las impedancias, resistencias y reactancias del sistema respiratorio a 5, 10, 15 y 20 Hz. Los resultados se analizaron por sexo, edad, talla y peso. Se de 127 participantes sanos ingresaron al estudio, 51.5% del sexo efectuó un modelo de regresión lineal múltiple. Resultados Un total masculino (68) y 48.5% (64) del femenino, con edad promedio de 39.65 ± 15.26 años; la talla tuvo un promedio de 1.63 ± 0.09 m. Se demostró que el sexo influye en los valores de la oscilometría en el volumen corriente (VT), la impedancia, las resistencias y el área de reactancia (p < 0.05), y no afecta las reactancias (XRs) (p > 0.05); este parámetro está mayormente asociado a la talla (r = 0.727, r2 = 0.528). La edad incide en los valores de la oscilometría, ya que las resistencias (Rrs) son menores en los grupos más jóvenes; el IMC y el peso no comprometieron los valores de IOS. Conclusiones Este estudio proporciona ecuaciones piloto de referencia para los índices comunes de oscilometría de impulso en sujetos mexicanos. Así, integra una prueba de función pulmonar para facilitar la detección de alteraciones funcionales en vía aérea pequeña. Sugerimos realizar más trabajos en población mexicana, sobre todo de edad avanzada, para confirmar nuestros resultados y proporcionar una base más sólida a las ecuaciones de referencia para IOS, con un fin clínico y epidemiológico.

Abstract Introduction Impulse oscillometry is a test that evaluates the respiratory mechanics by the application of small pulses of pressure, which produce flow oscillations to a certain frequency. Its main application is in the study of the illnesses of the small airline. The integrated software of the test equipment generates predictive values for each of the oscillometric parameters, based on German population data. Objective To standardize the impulse oscillometry test in order to design pilot equations for reference values in our population. Material and methods We performed a pilot, experimental, analytical, longitudinal study with healthy volunteer subjects. Spirometry and impulse oscillometry tests were performed, both basal impedances, resistances, and reactances of the respiratory system to and after bronchodilator application; we measured and registered the 5, 10, 15, and 20 Hz. The results were analyzed by sex, age, height, and weight. The analysis was performed using a model of multiple linear retrogression. Results A total of 127 healthy participants were recruited, 51.5% men (68) and 48.5% (64) women, with an average age of 39.65 ± 15.26 years; their height was an average of 1.63 ± 0.09 m. It was proved that the gender influences the oscillometry values of tidal volume (VT), the impedance, the resistances and reactance area (p < 0.05), but not the reactances (XRs) (p > 0.05); this parameter is mainly associated with the size (r = 0.727, r2 = 0.528). The age influences the oscillometry values since the resistances (Rrs) are lower in the youngest groups; the BMI and the weight had no influence on the values of IOS. Conclusions This study provides pilot reference equations for the common indexes of impulse oscillometry in Mexican subjects, in order to integrate this test of pulmonary function to facilitate the detection of functional alterations in the small airline. We suggest more studies should be done on Mexican population, and especially on people of advanced age, to confirm our results and to provide a more solid base for the equations of reference to IOS, with clinical and epidemiologic purposes.

Long-Term Stability of a Portable Carbon Monoxide Single-Breath Diffusing Capacity Instrument.

BACKGROUND: The 2005 American Thoracic Society/European Respiratory Society guidelines for single-breath diffusing capacity of the lung for carbon monoxide (DLCO) recommend a weekly biological control test and/or DLCO simulator to detect instrument error drift. Very little has been published regarding the results of such a quality assurance program. Our aim was to analyze the long-term stability of a portable DLCO instrument. METHODS: We used a new EasyOne Pro system and checked its accuracy using a DLCO simulator with 2 reference gases (concentration A: carbon monoxide [CO] = 0.1% and helium = 6.52%; concentration B: CO = 0.08% and helium = 7.21%) during the first 3 y of use in our large clinical laboratory. To detect instrument drift, a healthy woman (MSC), age 43 y old at baseline, tested herself every week during this period of time. RESULTS: More than 6,000 spirometry and 5,000 DLCO maneuvers were done using this instrument for patients during these 3 y. There were no failures in the daily volume and flow checks or the CO and helium calibration checks performed automatically by the instrument. The differences between the simulator DLCO and the measured DLCO were -0.91 ± 1.33 mL/min/mm Hg and -0.61 ± 1.45 mL/min/mm Hg for concentration A and concentration B, respectively. The results of the 110 biological control tests were: mean 30.8 ± 1.7 mL/min/mm Hg (95% CI 30.5-31.1), coefficient of variation of 5.4% in DLCO, and repeatability of 2.5 mL/min/mm Hg. Only 4 measurements were outside ±3 mL/min/mm Hg (3.6%). Her mean alveolar volume was 4.2 ± 0.25 L with coefficient of variation of 6.2%; her inspired volume was 3.05 ± 0.14 L, and coefficient of variation = 4.5%. CONCLUSIONS: Measurements of DLCO were stable over the 3-y period without any need for manual recalibration of the instrument. The biological control was as good as the DLCO simulator to evaluate this kind of device in a long-term laboratory quality control program.

Combined effects of mild-to-moderate obesity and asthma on physiological and sensory responses to exercise.

Despite the close link between asthma and obesity, there are no studies that have evaluated the sensory and physiological responses to exercise in obese asthmatics. We recently demonstrated that normal weight asthmatics with well controlled disease have preserved cardiorespiratory and sensory responses to exercise relative to non-asthmatic controls. However, these similarities may not hold true in patients with combined obesity and asthma. Accordingly, we sought to determine if combined asthma and obesity was associated with deleterious effects on cardiorespiratory fitness, exercise performance, dyspnoea, and physiological responses to exercise. Fourteen well-controlled obese asthmatics and fourteen age-matched normal weight asthmatics performed routine spirometry and underwent an incremental cardiopulmonary cycle test to assess the ventilatory, pulmonary gas exchange, cardiovascular, and sensory responses to exercise. Groups were well matched for age, height, spirometry, and asthma control. Obese asthmatics had a significantly greater body mass index (33 ± 3 vs. 23 ± 1 kg/m(2), p < 0.001) and lower self-reported activity levels by 47 % relative to normal weight asthmatics (p < 0.05). Obese asthmatics had a significantly lower maximal oxygen uptake (VO(2)) (82 ± 14 vs. 92 ± 10 %predicted) and work rate (75 ± 8 vs. 89 ± 13 %predicted) relative to normal weight asthmatics (p < 0.05). The anaerobic threshold occurred at a lower VO(2) in obese asthmatics vs. normal weight asthmatics (54 ± 15 vs. 66 ± 16 %predicted, p < 0.05). Ventilatory responses were superimposed throughout exercise with no evidence of a ventilatory limitation in either group. Cardiovascular responses were normal in both groups. Dyspnoea responses were similar but the obese asthmatics experienced greater leg fatigue ratings at submaximal work rates. In conclusion, obese individuals with well controlled asthma have reduced cardiorespiratory fitness and greater leg fatigue ratings relative to normal weight asthmatics. The relatively reduced cardiorespiratory fitness and exercise performance in obese compared to normal weight asthmatics is most likely driven by their more sedentary lifestyle and resultant deconditioning rather than due to respiratory factors.

Cardiorespiratory and sensory responses to exercise in well-controlled asthmatics.

OBJECTIVES: The purpose of this study was to evaluate detailed ventilatory, cardiovascular and sensory responses to cycle exercise in sedentary patients with well-controlled asthma and healthy controls. METHODS: Subjects included sedentary patients meeting criteria for well-controlled asthma (n = 14), and healthy age- and activity-matched controls (n = 14). Visit 1 included screening for eligibility, medical history, anthropometrics, physical activity assessment, and pre- and post-bronchodilator spirometry. Visit 2 included spirometry and a symptom limited incremental cycle exercise test. Detailed ventilatory, cardiovascular and sensory responses were measured at rest and throughout exercise. RESULTS: Asthmatics and controls were well matched for age, body mass index and physical activity levels. Baseline forced expiratory volume in 1 second (FEV(1)) was similar between asthmatics and controls (98 ± 10 versus 95 ± 9% predicted, respectively, p > 0.05). No significant differences were observed between asthmatics and controls for maximal oxygen uptake (31.8 ± 5.6 versus 30.6 ± 5.9 ml/kg/min, respectively, p > 0.05) and power output (134 ± 35 versus 144 ± 32 W, respectively, p > 0.05). Minute ventilation (V(E)) relative to maximum voluntary ventilation (V(E)/MVV) was similar between groups at maximal exercise with no subjects showing evidence of ventilatory limitation. Asthmatics and controls achieved similar age-predicted maximum heart rates (92 ± 7 versus 93 ± 8% predicted, respectively, p > 0.05). Ratings of perceived breathing discomfort and leg fatigue were not different between groups throughout exercise. CONCLUSIONS: The results of this study indicate that sedentary patients with well-controlled asthma have preserved sensory and cardiorespiratory responses to exercise with no evidence of exercise impairment or ventilatory limitation.