Wood smoke-associated lung disease: a clinical, functional, radiological and pathological description.

BACKGROUND: Approximately half of the world's population, and up to 90% of households in rural areas of developing countries, depend on biomass for cooking and heating. SETTING: The National Institute of Respiratory Diseases, México City. OBJECTIVE: To describe wood smoke-associated lung disease (WSLD). DESIGN: Description of the clinical, functional and radiological manifestations of patients with WSLD, and a comparison of pathological findings of patients who died of WSLD and smokers who died of chronic bronchitis. RESULTS: All patients with WSLD were non-smoking women with chronic bronchitis, in whom asthma, bronchiectasis, tuberculosis, congestive heart failure, extreme obesity and alfa-1 antitrypsin deficiency had been excluded. All patients used wood for cooking and had been exposed to wood smoke for a median of 45 years. Dyspnoea, airway obstruction, air trapping, increased airway resistance, pathological evidence of anthracosis, chronic bronchitis, centrilobular emphysema and pulmonary hypertension were present in most patients with WSLD. Bronchial squamous metaplasia was a common finding. There were no significant differences in the histopathological findings between patients with WSLD and smokers. Diffuse interstitial fibrosis was absent in all patients. CONCLUSIONS: Patients with WSLD have obstructive lung disease, chronic bronchitis, emphysema and pulmonary hypertension comparable to smokers.

[Altitude, the ratio of PaO2 to fraction of inspired oxygen, and shunt: impact on the assessment of acute lung injury]. / La altitud modifica la relación entre la PaO2/FiO2 y el cortocircuito: impacto en la valoración de la lesión pulmonar aguda.

The ratio of PaO2 to the fraction of inspired oxygen (PaO2/FIO2) is commonly used to determine the severity of acute lung injury and acute respiratory distress syndrome (ARDS). The research presented here used computational models of the lung to analyze the effect of altitude on the PaO2/FIO2 ratio and pulmonary shunt. At a given shunt, the PaO2/FIO2 ratio is lower at higher altitudes. Therefore, when evaluating for ARDS based on a PaO2/FIO2 ratio of <200 mm Hg, patients residing at high altitudes will have less shunt and, presumably, less severe lung injury than patients at sea level. This should be taken into consideration when comparing patients from different altitudes. Shunt should more often be measured directly or be estimated assuming a constant arteriovenous oxygen content difference.

Diabetes modifies the male:female ratio in pulmonary tuberculosis.

SETTING: Socio-cultural factors have been invoked to explain the male predominance among patients with pulmonary tuberculosis, but there is no conclusive evidence of their role. OBJECTIVE: To assess male predominance in a group of diabetics with pulmonary tuberculosis compared with patients with pulmonary tuberculosis alone. DESIGN: Clinical records of in-patients with pulmonary tuberculosis and with (TBDM group, n = 202) or without (TB group, n = 226) diabetes mellitus were reviewed, and the male percentages in each of six age groups (15-29, 30-39, 40-49, 50-59, 60-69, > or = 70 years) calculated. RESULTS: In the TB group, no gender difference (51% males) was found in the first age period, followed by a male predominance thereafter (71%, 68%, 75%, 63% and 58%). The TBDM group showed a similar pattern in the first two age groups (56% and 74%), followed by a steadily decline (r(S) = -0.90, P = 0.04) in male percentage (60%, 44%, 45%, 27%), leading to a female predominance after age 50. The association of age and gender was also corroborated by logistic regression in TBDM (P = 0.02), but not in TB (P = 0.19) patients. CONCLUSIONS: Diabetes was associated with a progressive shift of male predominance in pulmonary tuberculosis. Because diabetes is a disease that affects social activities similarly in men and women, our results suggest that factors other than socio-cultural ones are also important for determining the male predominance in pulmonary tuberculosis.

[Reproducibility of spirometry in Mexican workers and international reference values]. / Reproducibilidad de espirometrías en trabajadores mexicanos y valores de referencia internacionales.

OBJECTIVE: To describe spirometric function and adjustment to foreign prediction equations in Mexican workers claiming work related disability. MATERIAL AND METHODS: We reviewed 5771 spirometries done at the Mexican National Institute of Respiratory Diseases performed with equipment and methods proposed by the American Thoracic Society. With the spirometries we generated multiple regression equations separated for men and women based on age and height, compared to other in common use reported by Knudson and Hankinson in North America and by Quanjer in europeans. RESULTS: 80% of the tests were reproducible for FVC and FEV1 according to ATS, whereas 10% were reproducible for neither. Mean FVC in men was 12% above values reported by Quanjer, 22% above Knudson, 3% above Hankinson and 6% above Rodriguez-Reynaga, whereas similar values for women were 18%, 10%, 0% and 1%. Excluding obese and those who had less than 2 acceptable maneuvers, the numbers increase by 1-2%. FEV1 was also above predicted. CONCLUSIONS: Most workers requesting disability are able to generate a reproducible spirometry. However for the same gender, age and height, workers had a FEV1 and a FVC above normal values reported by Knudson and Quanjer and are more similar to those reported by Hankinson in Mexican-Americans. While a set of appropriate reference values are obtained, regression equations obtained from the studied group will generate less error in the evaluation of disability in mexican workers. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

[Estimation of gasometric values at different altitudes above sea level in Mexico]. / Estimación de los valores gasométricos en diferentes alturas sobre el nivel del mar en México.

We calculated reference values for arterial blood gases at different altitudes in Mexico assuming that sea level PaCO2 is 40 Torr, and in Mexico City (2.24 km. above the sea level) is 31.13 Torr, average of reported reference values. With the previous two points, it is possible to calculate a linear regression: PaCO2 = 40-3.96(altitude in km.). The equation is very similar to that calculated from reports in alveolar gas in North-Americans (Fitzgerald < 5 km): PACO2 = 39.3-3.11(altitude in km), and from subjects acclimatized to acute altitude exposure (< 5 km): PACO2 = 38.3-2.5 (altitude in km). It is also similar to a alinear equation that can be calculated assuming that hyperventilation in permanent habitants of moderate altitudes is inversely proportional to inspired molar concentration of O2: PaCO2 = PIO2/3.74. On the other hand, the equation is very different than that obtained from Andean natives (Hurtado): PaCO2 = 40.4-1.35(altitude in km). The proposed linear equation for Mexico gives very similar results (< 2 Torr difference) than a complex curvilinear equation by Morris et al. appropriate only up to 2.3 km. Evidence from acute exposure to altitude (acclimatized) and in North-Americans (alveolar gas) supports a reasonably accurate linear relationship up to 4 km. and also that the increase in ventilation in response to moderate altitudes in adult permanent residents is inversely proportional to molar concentration of O2. PAO2 was calculated with alveolar gas equation and resting the P(A-a)O2 we obtained PaO2. In conclusion, according to reference values in Mexico City, PaCO2 decreases about 4 Torr per km of altitude above the sea level. The decrease is similar to that reported in North-Americans and in acute exposure to altitude (acclimatized), but much less than that reported in native Peruvians. Ventilation is inversely proportional to the molar concentration of O2 at least up to an altitude where SaO2 is at or above 90%.

[Ketotifen (Zaditen and K-Asthmal): a drug with sales disproportionate to its demonstrated effectiveness]. / El ketotifeno (Zaditen y K-asmal): medicamento con ventas desproporcionadas para su efectividad demostrada.

Ketotifen is a sedative antihistamine promoted heavily for asthma treatment. Controlled trials are inconsistent: several did not find ketotifen better than placebo or cromoglycate. We do not have published controlled trials against inhaled steroids, the comparison most important to evaluate the efficacy of ketotifen. Ketotifen is poorly effective against exercise-induced asthma, and unable to reduce bronchial hyperactivity. The sedation and delay in therapeutic effect is also bothersome. Because of the uncertainties of its effect, ketotifen is not a first line drug against asthma, according to several international guidelines. Despite this information, ketotifen represented 17% of all antiasthmatic drug sales in Mexico in 1996, clearly exaggerated for the efficacy demonstrated. Ketotifen for asthma can be substituted with advantage by inhaled cromoglycate or corticosteroids. As a sedative antihistamine it is very expensive. The authorized publicity concerning ketotifen should be reevaluated with the current information available.

[The domestic inhalation of the smoke from firewood and of other biological materials. A risk for the development of respiratory diseases]. / La inhalación doméstica del humo de leña y otros materiales biológicos. Un riesgo para el desarrollo de enfermedades respiratorias.

A high proportion of the world population, especially in developing countries, is exposed to indoor pollutants produced by inefficient biomass stoves. The levels of pollutants, including toxins and carcinogens in the kitchen are usually very high. This potential pathogenic exposure has been scarcely studied. The exposure to biomass smoke has been associated to chronic bronchitis and chronic airflow obstruction in adults and to acute respiratory infections in children. At the National Institute of Pulmonary Diseases in Mexico, we have observed the entire spectrum of diseases associated with tobacco in people who never smoked and who were exposed to wood smoke. Women exposed to wood smoke had a five-fold risk of chronic bronchitis and chronic airflow obstruction, as compared to the non-exposed, according to a recent case-control study done at our Institute. The indoor levels of suspended particles smaller than 10 microns were frequently above 1,000 micrograms/m3 in a rural community in the state of Mexico. This information supports a causal role for biomass smoke for the genesis of several respiratory diseases, representing a potentially public health problem.

[Normal ventilatory response to hypoxia and hypercapnia at an altitude of 2240 meters]. / Respuesta ventilatoria normal a hipoxia e hipercapnia a una altitud de 2240 metros.

OBJECTIVE: To evaluate the ventilatory response to hypoxia and hypercapnia in healthy residents of Mexico City at 2240 m above sea level. METHODS: 15 healthy subjects, 10 women and 5 men, were studied (mean age 38; range 26-76). All completed one or two tests of ventilatory response to hypoxia and hypercapnia as described by Rebuck-Campbell and Read, respectively. The results were analyzed by linear regression using the minute ventilation as the dependent variable and SaO2 (hypoxia) or PCO2 (hypercapnia) as the independent variables. RESULTS: Seven subjects had very low or no response to hypoxia. The mean hypoxia slope was 0.7 +/- 0.6 L/min/% (+/- SD) and the hypercapnia slope was 3.0 +/- 1.4 L/min/mmHg. The intercepts were 176 +/- 278 for SaO2 and 3.0 +/- 7 for PCO2. CONCLUSIONS: A low respiratory response to hypoxia was found in Mexico City Healthy residents. The response to hypercapnia was similar in slope to other studies but had an intercept shifted to lower values. The Mexico City residents showed a behavior typical of patients with chronic hypoxemia or of dwellers at high altitudes.

Characteristics of the snoring noise in patients with and without occlusive sleep apnea.

We analyzed snoring noise from 10 nonapneic heavy snorers and nine patients with obstructive sleep apnea (OSA). Sound was recorded simultaneously through two microphones, one attached to the manubrium sterni and one suspended in the air 15 cm from the patient's head. Signals were stored on magnetic tape, digitized, and displayed in the time and frequency domains. Most of the power of snoring noise was below 2,000 Hz, and the peak power was usually below 500 Hz. When snores were generated during nose-only breathing (nasal snores), the sound spectrum was made up of a series of discrete, sharp peaks, with a fundamental note and harmonics similar to the spectrum of voiced sounds. When snores were generated during breathing through nose and mouth (oronasal snores), the spectra showed a mixture of sharp peaks and broad-band white noise. Patients with apnea showed a sequence of snores with spectral characteristics that varied markedly through an apnea-respiration cycle. The first postapneic snore consisted mainly of broad-band white noise with relatively more power at higher frequencies, so that the ratio of power above 800 Hz to power below 800 Hz could be used to separate snorers from patients with OSA. Other breaths in the cycle resembled oronasal or nasal snores in nonapneic subjects. Characteristics of the noise give information about the possible mechanism of sound generation and thus about the behavior of the pharynx during snoring. Quality of snoring sound may help to separate patients with obstructive apnea from those with simple snoring.

[Gasometric values reported in healthy subjects from the Mexican population: review and analysis]. / Valores gasométricos en sujetos sanos reportados en la población Mexicana: revisión y análisis.

We do not know the normal relationship between altitude and PaCO2 in Mexico. We collected and analyzed the reports of reference values for gasometry in Mexico City (2240 m above sea level and a mean barometric pressure of 585 Torr) and other places in the country. The reports include arterial, capillary and expired gases in children and adults, with measurements done in resting and exercising subjects, breathing room air and 100% oxygen. In Mexico City we found 18 studies in normal subjects reporting a mean PaCO2 ranging from 25.5 to 38.4 Torr. Averaging arterial studies from children and adults, adjusting for the number of subjects studied, and discarding data with mean pH below 7.37 or above 7.43 (suggesting non steady state), 10 studies with a total of 581 subjects have the following average values (Torr, means and SD): PaCO2 = 31.1 +/- 2.6, PaO2 = 67.7 +/- 2.6, calculated PAO2 and P(A-a)O2 73.6 +/- 3.3 y 6.1 +/- 3.7 respectively. The PaCO2 found was much lower than that reported for native Peruvians in the Andes who have a mean PaCO2 of 37.8 Torr at an altitude of 2390 m, and a mean PaCO2 of 33.0 Torr only at 4860 m above the sea level. On the other hand, the average values in Mexico are similar to those found in North Americans who have a mean PACO2 of 33.1 Torr at 2131 m of altitude, a mean PACO2 of 30.7 at 2371 m and a mean PaCO2 of 31 Torr at 2238 m. Normal values for gasometry in Mexico are scarce and some of the existing ones are erroneous probably due to lack of adequate calibrations and to poor quality control. Values of PaCO2 in Mexico are more similar to those found in the USA than to those found in Peruvian natives.

[The challenge of evaluating clinical competence]. / El desafío de la evaluación de la competencia clínica.

The study is divided in two parts. The first one deals with theoretical aspects of evaluation. In the second part, the development of an instrument intended to explore clinical competence is presented. The importance of considering evaluation as part of a research process is emphasized in the first part. The diverse theoretical and action trends in the field of education are synthetized in two main tendencies: the active-participating and the passive-receptive. The influence of these two tendencies in the selection the objects for evaluation is also discussed. An evaluation instrument developed by us to explore clinical competence is placed within the active-participating tendency of education; the present state of this instrument is given in the second part. The instrument consists of multiple choice options of the true, false, don't know type. The instrument in its present version is the result of a long validation process. It explores particularly iatrogenic behaviors by omission or commission. The sample studied were 457 applicants for specialization courses in medicine. Of these, 127 were foreign applicants. The instrument was applied to the whole sample in one single session. The results showed a low general clinical competence, with similar results in mexican and foreign applicants. A clear difference was found in commission iatrogenia which was significantly more frequent than omission iatrogenia. The theoretical superiority of our test in relation the others is discussed.

[Ethical attitudes related to problems of managing patients with acquired immunodeficiency syndrome]. / Actitudes éticas ante los problemas de manejo de los pacientes con el síndrome de inmunodeficiencia adquirida.

We evaluated, with a questionnaire, ethical attitudes towards the clinical attention of patients with AIDS in 88 physicians. Most of the surveyed were residents and all were working in two mexican hospitals with experience managing patients with AIDS: The National Institute of Nutrition and the National Institute of Respiratory Diseases. None of the questions was answered similarly by all physicians and some of them considered ethically unquestionable, behaviours that traditionally are immoral or even illegal. Reproducibility of the results, evaluated in 10 doctors 5 months later, was acceptable. Ethical attitudes were heterogeneous and inconsistent in the surveyed. This can be the results of a poor or absent training in Medical Ethics in medical schools and during residencies. We believe this deficiency helps maintaining discriminatory attitudes against patients with AIDS and may decrease the quality of medical services to the group.

Rapid shallow breathing caused by pulmonary vascular congestion in cats.

The vasculature of one lung of unanesthetized spontaneously breathing decerebrate cats was isolated and congested with blood. Such pulmonary vascular congestion (PVC) consistently resulted in a shallow tachypnea associated with expiratory activation of the diaphragm and thyroarytenoid muscles, signifying augmented expiratory braking. With progressive increases in pulmonary vascular pressure, tachypnea and expiratory braking increased progressively and ultimately obscured phasic activity in the diaphragm and thyroarytenoid. Thus the apnea caused by PVC constitutes not an arrest of neural respiratory activity but rather a continuous activation of thoracic inspiratory and laryngeal adductor muscles. When capsaicin, a neurotoxin that activates nonmyelinated afferents, was injected into the pulmonary artery of the isolated lung, it produced changes in timing and distribution of respiratory motor output that resembled those with PVC but were more abrupt in onset. Capsaicin, applied perineurally to the cervical vagi, preferentially blocked the conduction of nonmyelinated afferent fibers. This procedure, which produced little degradation in Hering-Breuer reflexes, eliminated tachypnea and expiratory braking caused by PVC or capsaicin injection. The results indicate that activation of pulmonary vagal afferent fibers of C or A-delta category in unanesthetized cats reflexly modifies the respiratory motor output in a way that resembles the human response to PVC or pulmonary embolism. This is a brain stem reflex.

[Method for calculating the distribution of randomly expected scores in a false-true-do not know-type of test]. / Método para calcular la distribución de las calificaciones esperadas por azar en un examen del tipo falso, verdadero y no sé.

Multiple choice tests have been used widely in the evaluation of knowledge. The lowest passing limit is generally chosen arbitrarily. Better and more objective criteria may arise from analyzing the distribution of correct and incorrect answers as expected by chance. In order to calculate the distribution of correct answers and the difference between correct and incorrect answers (core) we propose the use of a method based on a gaussian distribution. The distribution of scores expected by chance is approximated by a gaussian distribution with a mean of zero and a standard deviation SD = square root of n(pA + pE), and the distribution of the total number of correct answers has a mean of npA and SD = square root of npApE, where n is the total number of questions, and pA and pE are the probabilities of having a correct and an incorrect answer, respectively. The formulae are applicable to questions type false/true/do not know and to the more common type of one correct in five options. Once the chance distribution is known, it can be compared with the distribution of scores or correct answers obtained, which can then be used to separate people in two groups: those that answer the test as expected or worse than expected by chance, and those that answer the test better than expected by chance. The first group should not be passed. The passing of individuals in the second group can be decided by additional criteria.

Snoring in normal young adults: prevalence in sleep stages and associated changes in oxygen saturation, heart rate, and breathing pattern.

Six men and three women, asymptomatic light snorers ranging in age from 25-34 years, were studied during sleep to determine the prevalence of snoring in the different sleep stages, the associated changes in oxygen saturation (SaO2), heart rate (HR), and breathing frequency (f), and the associated breathing arrhythmias. Snoring was defined as a 1-minute epoch with more than 80% of the breaths associated with snores. Most of the snoring epochs as well as the apneas and hypopneas occurred during stage 2, mainly because it is the most prolonged sleep stage. The prevalence of snoring, however, normalized for differences in length of sleep stages, was highest in stages 3 and 4 but low in REM, whereas the converse was true for apneas and hypopneas. Snoring caused no change in the mean SaO2, mean HR, or f, as compared with nonsnoring periods in the same sleep stage. Continuous snoring in normal subjects can occur without significant O2 desaturation or breathing arrhythmia. Continuous snoring and breathing arrhythmia tended to occur together in a given subject but were unrelated in time, suggesting a different pathogenesis.

[Accuracy of an the ear oximeter Biox-III and its sensitivity to carboxyhemoglobin in Mexico City]. / Exactitud del oxímetro de oído (Biox-III) en la ciudad de México y su sensibilidad a la carboxihemoglobina.

Ear oximeters estimate arterial oxygen saturation (Sa02) measuring the characteristics of light transmission through the ear lobe. We tested the accuracy of a new ear oximeter (Biox-III) in Mexico City comparing its estimates (Sa02OXI) with Sa02 measured by a Co-Oximeter, in a simultaneously taken arterial blood sample. We used two indexes in the arterial sample: Sa02 of the total hemoglobin (Sa02T) given directly by the Co-Oximeter and Sa02 of the hemoglobin available for oxygenation (Sa02A) which corrects for the presence of carboxyhemoglobin and metahemoglobin. We studied 21 subjects with a total of 100 simultaneous samples with a Sa02T ranging from 36.2% to 97.2%. The samples were obtained with the subjects resting, during light exercise, during rebreathing and increasing the Fi02. Spearman and Pearson's correlation coefficients between Sa02OXI and Sa02A were 0.97, and between Sa02OXI and Sa02T were 0.96. Lineal regression equations were: Sa02T = 2.047 (Sa02OXI) -8.5 and Sa02A = 1.102 (Sa02OXI) -9.32. Slopes of the equations and correlation coefficients were statistically significant (P less than 0.001). Mean error of Sa02OXI compared with Sa02T (Sa02T-Sa02OXI) was -4.4% and compared with Sa02A (Sa02A-Sa02OXI) was -0.4%, with a standard deviation of 3.4% and 3.5% respectively. In the presence of carboxyhemoglobin the ear oximeter overestimates Sa02T but not Sa02A. Measurement error increases during rebreathing maybe because error increases at low Sa02 and because of the delay in oximeter's response in a situation of a continuously falling Sa02. Ear oximeter Biox-III estimates Sa02 in Mexico City as accurately as the Biox-IIA at sea level. Sa02 measurement is quick, easy, continuous and non-invasive, which increase its potential clinical and research application.

Implicaciones clinicas del roncar. / Clinical implications of the snoring

El roncar es muy frecuente en la poblacion general, especialmente en hombres, en obesos y a edad avanzada. Dentro del grupo de personas que roncan, se pueden reconocer 3 subgrupos: 1) los pacientes con el sindrome de apnea obstructiva del sueno (SAOS), quienes tienen ademas sueno intranquilo, somnolencia, alteraciones de conducta y diversos sintomas matutinos. Estos pacientes requieren tratamiento agresivo con drogas, presion positiva a la via aerea o aun cirugia dependiendo de la gravedad del sindrome. 2) Los roncadores habituales sin el SAOS frecuentemente tienen episodios aislados de apneas obstructivas y maior incidencia de hipertension arterial y cardiopatia que los no roncadores.3) El mayor grupo de roncadores son los que lo hacen intermitentemente, sin apenas obstructivas y en quienes no se ha demostrado que el roncar represente un riesgo para la salud.Dentro de estos 3 grupos de pacientes, se deben buscar factores predisponentes susceptibles de correccion como obstruccion de la via aerea superior, obesidad, mixedema o acromegalia. Al resto de roncadores "idiopaticos" sin el SAOS se les puede ofrecer muy poco actualmente