Arterial Blood Gases in Normal Subjects at 2240 Meters Above Sea Level: Impact of Age, Gender, and Body Mass Index

Background

The values of arterial blood gases (ABG) change with altitude above sea level; empirical verification is essential because ventilatory acclimatization varies with ethnicity and a population's adaptation.

Objective

The aim of the study was to describe ABG in a healthy population residing at 2,240 meters above sea level, to identify the mean level of alveolar ventilation (PaCO₂), and to know whether a progressive increase in PaCO₂ occurs with age and the impact of increasing body mass index (BMI).

Methods

We conducted a cross-sectional study in a referral center for respiratory diseases in Mexico City. Associations among variables with correlation coefficient and regression models of PaO₂, SaO₂, and P(A-a)O₂ as dependent variables as a function of age, BMI, minute ventilation, or breathing frequency were explored.

Results

Two hundred and seventeen healthy subjects were evaluated with a mean age of 40 ± 15 years, mean of the PaO₂ was 71 ± 6 mmHg, SaO₂ 94% ± 1.6%, PaCO₂ 30.2 ± 3.4 mmHg, HCO₃ 20 ± 2 mmol/L, BE-2.9 ± 1.9 mmol/L, and the value of pH was 7.43 ± 0.02. In a linear regression, the main results were PaO₂ = 77.5-0.16*age (p < 0.0001) and with aging P(A-a)O₂ tended to increase 0.12 mmHg/year. PaCO₂ in women increased with age by 0.075 mmHg/year (p = 0.0012, PaCO₂ =26.3 + 0.075*age). SaO₂ and PaO₂ decreased significantly in women with higher BMI 0.14% and 0.52 mmHg per kg/m², (p = 0.004 and 0.002 respectively).

Conclusion

Mean PaCO₂ was 30.7 mmHg, implying a mean alveolar ventilation of around 30% above that at sea level.

Functional impact of sequelae in drug-susceptible and multidrug-resistant tuberculosis

BACKGROUND: Evidence on the impact of tuberculosis (TB) treatment on lung function is scarce. The aim of this study was to evaluate post-treatment sequelae in drug-susceptible and drug-resistant-TB (DR-TB) cases in Mexico and Italy.METHODS: At the end of TB treatment the patients underwent complete clinical assessment, functional evaluation of respiratory mechanics, gas exchange and a 6-minute walking test. Treatment regimens (and definitions) recommended by the World Health Organization were used throughout.RESULTS: Of 61 patients, 65.6% had functional impairment, with obstruction in 24/61 patients (39.4%), and 78% with no bronchodilator response. These effects were more prevalent among DR-TB cases (forced expiratory volume in 1 s/forced vital capacity [FEV1/FVC] < lower limit of normality, 14/24 vs. 10/34; P = 0.075). DR-TB patients showed moderately severe (FEV1 < 60%) and severe obstruction (FEV1 < 50%) (P = 0.008). Pre- and post-bronchodilator FEV1 and FEV1/FVC (% of predicted) were significantly lower among DR-TB cases. Plethysmography abnormalities (restriction, hyperinflation and/or air trapping) were more frequent among DR-TB cases (P = 0.001), along with abnormal carbon monoxide diffusing capacity (DLCO) (P = 0.003).CONCLUSION: The majority of TB patients suffer the consequences of post-treatment sequelae (of differing levels), which compromise quality of life, exercise tolerance and long-term prognosis. It is therefore important that lung function is comprehensively evaluated post-treatment to identify patient needs for future medication and pulmonary rehabilitation.

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.

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.

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 (D_LCO) recommend a weekly biological control test and/or D_LCO 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 D_LCO instrument.

METHODS

We used a new EasyOne Pro system and checked its accuracy using a D_LCO 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 D_LCO 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 D_LCO and the measured D_LCO 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 D_LCO, 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 D_LCO were stable over the 3-y period without any need for manual recalibration of the instrument. The biological control was as good as the D_LCO simulator to evaluate this kind of device in a long-term laboratory quality control program.

[Frequency and clinical, biochemical and histological characteristics of nonalcoholic fatty liver disease in patients with gallstone disease]

BACKGROUND

In 1980, nonalcoholic fatty liver disease (NALFD) was described. It is related to the genesis of gallstones and is considered as a manifestation of the metabolic syndrome. In order to determine the frequency, anatomoclinical characteristics and biochemical and histological alterations in NAFLD, patients underwent cholecystectomy (GD). For this reason, we considered carrying out this study.

METHODS

This was a prospective and observational study. The study population was comprised of patients with gallstone disease who were treated at the "Hospital Español" in Veracruz, Mexico from January 1, 2005 to November 30, 2006 and underwent cholecystectomy and liver biopsy. Analyzed variables were anthropometric characteristics and risk factors, and in each patient biochemical tests, abdominal ultrasound (US) and histological liver study were performed.

RESULTS

In 95 patients, according to liver biopsy diagnoses, we found a frequency of 54.74% of NAFLD associated with gallstones. Females were more affected (71.15%) and the average age was 55.6 +/- 17.87 years. Risk factors were obesity (67.3%), diabetes mellitus (17.3%), and dyslipidemia (76.92%). Patients with NAFLD had elevated levels of glucose, glycosylated hemoglobin, cholesterol, triglycerides and HDLcholesterol, and aminotransferases. Abdominal US did not show sufficient specificity and sensitivity to detect NAFLD. Histological findings showed stage I steatosis in 51.93%, stage II in 28.84% and stage III in 19.23%. Cirrhosis was found in 3.15%.

DISCUSSION

Results of our study confirm the high frequency of NAFLD in association with gallstone disease. We consider this the first work to analyze and describe the primary clinical, biochemical and morphological characteristics.

[Role of physical, psychological and sexual abuse in functional digestive disorders. A case-controls trial.]

INTRODUCTION

Abuse has been considered a significant factor on the development of functional gastrointestinal disorders (FGID), especially for severe and treatment-refractory patients. The aim of our study was to evaluate the presence of all FGID according to Rome II criteria, in a group of women with history of physical, psychological and/or sexual abuse.

MATERIAL AND METHODS

A cross sectional study was performed in 96 women (37 +/- 12 years of age) with history of physical, psychological and/or sexual abuse (cases); and 96 open population women (36 +/- 14 years of age) (controls). The following evaluations were administered: Rome II questionnaire, a self-administered instrument to evaluate history of physical (beating), psychological(insults, public humiliation) and/or sexual abuse (rape, coercion), and HAD questionnaire.

RESULTS

Among 96 women with history of abuse,91 (95%) reported to have suffered psychological abuse, 72 (75%) physical abuse, and 24 (25%)sexual abuse. Women with history of abuse had a higher prevalence of rumination (6% vs. 0%, p= 0.02), functional heartburn (26% vs. 13%, p =0.04), aerofagia (17% vs. 5%, p = 0.019), irritable bowel syndrome (38% vs. 18%, p = 0.002), fecalin continence (16% vs. 4%, p = 0.01), elevator anisyndrome (5% vs. 0%, p = 0.05), and proctalgia fugax (29% vs. 15%, p = 0.02) compared to controls. There was a positive correlation between anxiety (r = 0.5, p = 0.001) and depression scores(r = 0.45, p = 0.001), and the number of FGID.

CONCLUSION

We demonstrated a high prevalence of FGID among women with history of physical,psychological, and/or sexual abuse. In this association,concomitant anxiety and depression play a significant role.

[Frequency of NAFLD in a group of patients with metabolic syndrome in Veracruz, Mexico]

INTRODUCTION

Nonalcoholic fatty liver disease is a very common disease that is being described principally in obese, diabetic and hiperlipidemic patients without significant alcohol consumption (less than 28 ethanol Units per week). Nowadays it is considered as the hepatic manifestation of the metabolic syndrome. The frequency of Non Alcoholic Sreatohepatic (NASH) is 30 to 35% in general population, but it reaches to 70% in patients whose Body Mass Index (BMI) is above 30 kg/m2 as it occurs with diabetic patients. In Mexico there are only isolated reports about it's frequency, nearly 7.1% in general population and 18.5% in diabetic patients.

OBJECTIVE

To know the frequency of the Nonalcoholic fatty liver disease in patients who receive medical attention at the city of Veracruz.

MATERIAL AND METHODS

We studied 337 patients, who were divided into 4 groups: Normal Weight, Overweight, Obese and Diabetes type 2 patients. The individuals who reported previous hepatitis and alcohol consumption were excluded. All patients made a test in order to determinate: age, gender, presence of hepatic stigmata and complaints. Laboratory tests were done to all patients including: Blood glucose, seric lipids, transaminases, proteins and alkaline phosphatase. In those cases with impairment in transaminases results, it was done upper abdominal ultrasound (USG) and hepatic biopsy, in patients who accepted.

RESULTS

We identified 53 cases (15.72%) with characteristics of Nonalcoholic fatty liver disease. The frequency in patient with normal weight and overweight was 7.14% to 7.76%, while in obese subjects it was 14.15% and 28% in diabetic patients; 73.58% of all patients were female and the other 28.41% were males. The average age of the group was 48.11 years, it was similar the specific age of the normal weight and obese patients, in overweight patients was 61.5 years and the average age in diabetics was 56.42 years. There were significant differences in the results of blood glucose level, glycosilated hemoglobin, cholesterol, seric lipid values and aminotransferases in obese and diabetic patients compared with normal subjects and overweight patients in our study, the USG did not show sensibility and specificity to detect Non alcoholic fatty liver disease (NAFLD).

DISCUSSION

The results of this study show a lower frequency compared with the rest of the world, however it was higher in diabetic population than the frequency published by Bernal in Hidalgo, Mexico. The aminotransferases level resulted elevated in all patients with metabolic syndrome and NAFLD so we consider that elevated aminotransferases levels is the best predictor to suspect the presence of NAFLD. That is why it's very important to consider the possibility to avoid the progression to cirrhosis and hepatocarcinoma.