Smoking exposure trajectories and pulmonary function in early adulthood in a Brazilian cohort

OBJECTIVES

To investigate smoking trajectories and their association with pulmonary function (PF) and respiratory symptoms at age 22.

METHODS

Data from a population-based cohort study of 3350 individuals and their spirometries were analysed. The outcomes were: forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), forced expiratory flow at the mid expiratory phase (FEF25-75 %), FEV1/FVC and FEF25-75/FVC ratio. Smoking data were collected at perinatal follow-up (gestational exposure) and 15, 18 and 22 years. Group-based trajectory model was applied.

RESULTS

Four groups were identified: no exposure (NE), gestational (GE), gestational and adulthood (GAE) and continuous (CE) exposure. Both CE and GAE trajectories were associated with lower values of FEV1/FVC (-1.77pp; p = 0.01 and -1.58 pp; p<0.001 respectively) and FEF25-75/FVC ratio (-7.27pp; p = 0.019 and -6.04pp; p<0.001 respectively) compared to the NE trajectory. Lower FEV1 and FEF25-75 % values were also related to the GAE trajectory (-68 ml; p = 0.03 and -253 ml/s;p<0.001 respectively). Compared to those who never smoked, individuals who smoked 10 or more cigarettes daily presented a reduction in the FEV1/FVC ratio by 1.37pp (p<0.001), FEF25-75 % by 126 ml (p = 0.012) and FEF25-75 %/FVC ratio by 3.62pp (p = 0.011). CE trajectory showed higher odds of wheezing (OR 4.14; p<0.001) and cough (OR 2.39; p = 0.002) compared to the non-exposed group.

CONCLUSIONS

The in-uterus exposure to maternal smoking reduces PF later in life. However, the perpetuation of smoking behaviour throughout adolescence and early adulthood is determinant for PF main reduction and the emergence of respiratory-related symptoms.

The global burden of chronic respiratory disease in adults

With an aging global population, chronic respiratory diseases are becoming a more prominent cause of death and disability. Age-standardised death rates from chronic obstructive pulmonary disease (COPD) are highest in low-income regions of the world, particularly South Asia and sub-Saharan Africa, although airflow obstruction is relatively uncommon in these areas. Airflow obstruction is, by contrast, more common in regions with a high prevalence of cigarette smoking. COPD mortality is much more closely related to the prevalence of a low forced vital capacity which is, in turn, associated with poverty. Mortality from asthma is less common than mortality from COPD, but it is also relatively more common in poorer areas, particularly Oceania, South and South-East Asia, the Middle East and Africa. Again this contrasts with the asthma prevalence among adults, which is highest in high-income regions. In high-income areas, mortality due to asthma, which is predominantly an adult problem, has fallen substantially in recent decades with the spread of new guidelines for treatment that emphasise the use of inhaled steroids to control the disease. Although mortality rates have been falling, the prevalence of atopy has been increasing between generations in Western Europe. Changes in the prevalence of wheeze among adults has been more varied and may have been influenced by the reduction in smoking and the increase in the use of inhaled steroids.

Summarising published results from spirometric surveys of COPD: the problem of inconsistent definitions

SETTING

The use of different spirometric definitions for chronic obstructive pulmonary disease (COPD) has made an informative review of the available prevalence surveys impossible.

OBJECTIVE

To derive adjustment factors that allow the comparison of studies using different spirometric criteria.

METHODS

Pre- and post-bronchodilator one-second forced expiratory volume (FEV1) and forced vital capacity (FVC) values were taken from the Burden of Obstructive Lung Disease (BOLD) survey in 16 centres. Using a post-bronchodilator FEV1/FVC ratio less than the lower limit of normal (LLN) as our reference prevalence, we calculated simple multiplicative adjustments to transform other reported prevalence estimates to reference values. These adjustments were then tested on independent data sets from six further BOLD centres and five centres from the PLATINO study, a Latin American survey on obstructive lung disease.

RESULTS

Prevalence estimates based on pre-bronchodilator fixed-ratio measurements were 5-25% higher than reference values, and were strongly positively biased with age and prevalence level. Applying simple adjustments provided prevalence estimates that were almost unbiased and within 5% of the reference values.

CONCLUSIONS

Using the BOLD data, we have been able to estimate COPD prevalences based on post-bronchodilator FEV1/FVC < LLN by adjusting estimates based on other common definitions, enabling more meaningful comparisons of published findings.

Paid employment in subjects with and without chronic obstructive pulmonary disease in five Latin American cities: the PLATINO study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a costly condition that frequently causes permanent work disabilities. Little information exists regarding the impact of COPD on work force participation and the indirect costs of the disease in developing countries.

OBJECTIVE

To examine the frequency of paid employment and factors influencing it in a Latin-American population-based study.

METHODS

Post-bronchodilator FEV(1)/FVC < 0.70 (forced expiratory volume in 1 s/forced vital capacity) was used to define COPD. Information regarding paid work was assessed by the question 'At any time in the past year, have you worked for payment?'

RESULTS

Interviews were conducted with 5571 subjects; 5314 (759 COPD and 4554 non-COPD) subjects underwent spirometry. Among the COPD subjects, 41.8% reported having paid work vs. 57.1% of non-COPD (P < 0.0001). The number of months with paid work was reduced in COPD patients (10.5 ± 0.17 vs. 10.9 ± 0.06, P < 0.05). The main factors associated with having paid work in COPD patients were male sex (OR 0.33, 95%CI 0.23-0.47), higher education level (OR 1.05, 95%CI 1.01-1.09) and younger age (OR 0.90, 95%CI 0.88-0.92). COPD was not a significant contributor to employment (OR 0.83, 95%CI 0.69-1.00, P = 0.054) in the entire population.

CONCLUSIONS

Although the proportion of persons with paid work is lower in COPD, having COPD appears not to have a significant impact on obtaining paid employment in the overall population of developing countries.

Respiratory health effects of indoor air pollution

Domestic pollution is relevant to health because people spend most of their time indoors. One half of the world's population is exposed to high concentrations of solid fuel smoke (biomass and coal) that are produced by inefficient open fires, mainly in the rural areas of developing countries. Concentrations of particulate matter in kitchens increase to the range of milligrams per cubic meter during cooking. Solid fuel smoke possesses the majority of the toxins found in tobacco smoke and has also been associated with a variety of diseases, such as chronic obstructive pulmonary disease in women, acute respiratory infection in children and lung cancer in women (if exposed to coal smoke). Other tobacco smoke-associated diseases, such as tuberculosis, asthma, respiratory tract cancer and interstitial lung diseases, may also be associated with solid fuel smoke inhalation, but evidence is limited. As the desirable change to clean fuels is unlikely, efforts have been made to use efficient, vented wood or coal stoves, with varied success due to inconsistent acceptance by the community.

Can a normal peak expiratory flow exclude severe chronic obstructive pulmonary disease?

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is underdiagnosed. One barrier to diagnosis is the limited availability of spirometry testing, but in adults at risk for COPD, a normal pre-bronchodilator (pre-BD) peak expiratory flow (PEF) may rule out clinically significant COPD.

OBJECTIVE

To identify post-BD airway obstruction using data from 13 708 individuals aged >or=40 years from the PLATINO and BOLD studies.

METHODS

We evaluated different cut-off points of pre-BD. The PEF was obtained from a diagnostic-quality spirometer (not a mechanical PEF meter). At least one of the following COPD risk factors was present in 77% of the subjects: chronic respiratory symptoms; exposure to tobacco smoke, biomass smoke or dust in the workplace; or a previous diagnosis of asthma, COPD, emphysema or chronic bronchitis.

RESULTS

Although the positive predictive value was low as expected, a pre-BD PEF of >or=70% predicted effectively ruled out Stages III and IV COPD of the Global Initiative for Chronic Obstructive Lung Disease. Among those with at least one risk factor, only 12% would require confirmatory spirometry using this criterion.

CONCLUSIONS

Adding PEF measurement to a screening questionnaire may rule out severe to very severe COPD without the need for pre- and post-BD spirometry testing. Confirmation is needed from a study using inexpensive PEF meters or pocket spirometers with a staged screening protocol.

Worldwide burden of COPD in high- and low-income countries. Part II. Burden of chronic obstructive lung disease in Latin America: the PLATINO study

SETTING

Five Latin American cities: São Paulo, Brazil; Mexico City, Mexico; Montevideo, Uruguay; Santiago, Chile; Caracas, Venezuela.

OBJECTIVE

To describe the burden of chronic obstructive pulmonary disease (COPD) in Latin America.

DESIGN

This is a multicentre study. Post-bronchodilator spirometry was used and the main outcome measure was FEV(1)/FVC < 0.7 (fixed ratio criterion). Global Obstructive Lung Disease (GOLD) stages were also analysed.

RESULTS

The combined population aged > or =40 years in the five countries included in the study was approximately 85.3 million. Of these, it was estimated that 12.2 million have airflow obstruction, which corresponds to our prevalence estimate of 14.3%. The proportion of subjects in Stages II-IV of the GOLD classification was 5.6%. Risk factors presenting the highest aetiological fractions for COPD were age, current smoking, indoor exposure to coal and exposure to dust in the workplace. Smoking, the modifiable factor with the strongest aetiological fraction for COPD, affects 29.2% of adults aged > or =40 years in these cities, corresponding to approximately 25 million smokers in this age group.

CONCLUSION

Prevention of smoking and exposure to pollutants, such as coal and dust, are the interventions most likely to succeed against COPD in Latin America. The information obtained by a collaborative study has been vast and encouraging for other similar studies.

Hidden respiratory disease-associated deaths

OBJECTIVE

To bring together all deaths of respiratory origin, whether concentrated under Group J of the International Classification of Diseases (ICD-10) or in other codes, and including the upper and lower airways and thorax, for a more accurate assessment of the public importance of respiratory diseases.

METHODS

The most recent disaggregated mortality database (data from 86 countries) available from the World Health Organization using the ICD-10 was reviewed.

RESULTS

Respiratory problems caused 16.6% of the deaths in the countries analysed (95%CI 7.9-27.1); 61% were considered chronic respiratory ailments (95%CI 17-85). Of all respiratory-related deaths, 44% were outside Group J and 7.8% were hidden in codes other than J, thoracic tumours, tuberculosis and diseases of pulmonary circulation. Hidden respiratory deaths were more common in low-income countries, but approximately 5% of respiratory deaths in high-income countries were also hidden. Respiratory deaths were the leading cause of death in five countries even when compared to the total number of cardiovascular and cancer deaths.

CONCLUSIONS

A significant proportion of respiratory deaths are 'hidden' in several ICD-10 codes, and are more numerous in countries with a high rate of acute respiratory disease and a low rate of chronic respiratory disease.

Outdoor and indoor air pollution and COPD-related diseases in high- and low-income countries

Chronic obstructive pulmonary disease (COPD) is an important cause of morbidity and mortality in both high- and low-income countries. While active cigarette smoking is the most important preventable risk factor globally, outdoor and indoor air pollutants can cause or exacerbate COPD. In high-income countries, historic air pollution events provide clear evidence that exposure to high levels of outdoor air pollutants is associated with increased mortality and morbidity due to COPD and related cardiorespiratory diseases. Studies in the last 20 years continue to show increased risk associated mainly with particulate matters, even at much lower levels. Populations in low-income countries are largely exposed to indoor air pollutants from the combustion of solid fuels, which contributes significantly to the burden of COPD-related diseases, particularly in non-smoking women. Effective preventive strategies for COPD may vary between countries, and include continued improvements in air cleaning technology, air quality legislation and dissemination of improved cooking stoves. A joint effort from both society and governments is needed for these endeavors.

Efficacy of the FEV1/FEV6 ratio compared to the FEV1/FVC ratio for the diagnosis of airway obstruction in subjects aged 40 years or over

The present cross-sectional, population-based study was designed to evaluate the performance of the FEV1/FEV6 ratio for the detection of airway-obstructed subjects compared to the FEV1/FVC <0.70 fixed ratio test, as well as the lower limit of normality (LLN) for 1000 subjects (3)40 years of age in the metropolitan area of São Paulo, SP, Brazil. After the exclusion of 37 (3.7%) spirometries, a total of 963 pre-bronchodilator (BD) and 918 post-BD curves were constructed. The majority of the post-BD curves (93.1%) were of very good quality and achieved grade A (762 curves) or B (93 curves). The FEV1/FEV6 and FEV1/FVC ratios were highly correlated (r(2) = 0.92, P < 0.000). Two receiver operator characteristic curves were constructed in order to express the imbalance between the sensitivity and specificity of the FEV1/FEV6 ratio compared to two FEV1/FVC cut-off points for airway obstruction: equal to 70 (area under the curve = 0.98, P < 0.0001) and the LLN (area under the curve = 0.97, P < 0.0001), in the post-BD curves. According to an FEV1/FVC <0.70, the cut-off point for the FEV1/FEV6 ratio with the highest sum for sensitivity and specificity was 0.75. The FEV1/FEV6 ratio can be considered to be a good alternative to the FEV1/FVC ratio for the diagnosis of airway obstruction, both using a fixed cut-off point or below the LLN as reference. The FEV1/FEV6 ratio has the additional advantage of being an easier maneuver for the subjects and for the lung function technicians, providing a higher reproducibility than traditional spirometry maneuvers.

Tuberculosis and airflow obstruction: evidence from the PLATINO study in Latin America

The aim of the present study was to evaluate the association between history of tuberculosis and airflow obstruction. A population-based, multicentre study was carried out and included 5,571 subjects aged > or =40 yrs living in one of five Latin American metropolitan areas: Sao Paulo (Brazil); Montevideo (Uruguay); Mexico City (Mexico); Santiago (Chile); and Caracas (Venezuela). Subjects performed pre- and post-bronchodilator spirometry and were asked whether they had ever been diagnosed with tuberculosis by a physician. The overall prevalence of airflow obstruction (forced expiratory volume in one second/forced vital capacity post-bronchodilator <0.7) was 30.7% among those with a history of tuberculosis, compared with 13.9% among those without a history. Males with a medical history of tuberculosis were 4.1 times more likely to present airflow obstruction than those without such a diagnosis. This remained unchanged after adjustment for confounding by age, sex, schooling, ethnicity, smoking, exposure to dust and smoke, respiratory morbidity in childhood and current morbidity. Among females, the unadjusted and adjusted odds ratios were 2.3 and 1.7, respectively. In conclusion, history of tuberculosis is associated with airflow obstruction in Latin American middle-aged and older adults.

Prevalence of oxygen desaturation and use of oxygen at home in adults at sea level and at moderate altitude

The aim of this study was to determine the prevalence of oxygen desaturation in adults aged>or=40 yrs as altitude above sea level increases. A population-based, cross-sectional study with a multistage cluster sampling of 1,063 subjects from metropolitan Mexico City (Mexico; 2,240 m above sea level), 1,357 from Caracas (Venezuela; 950 m) and 943 from Montevideo (Uruguay; 35 m). The mean of six measurements of arterial oxygen saturation (SP,O2) was estimated using a pulse oximeter. Mean SP,O2 decreased with altitude. No subject from Montevideo had a mean SP,O2<or=88%. Prevalence of subjects with SP,O2<or=88%, a common criterion used for oxygen prescription, was 1.0% in Caracas and 6.0% in Mexico City. Additional predicting factors for hypoxaemia in multiple regression models were age, body mass index and a low forced expiratory volume in one second as a percentage of the predicted value. In Mexico City and Caracas, <10% of the hypoxaemic subjects reported use of domiciliary oxygen, whereas at least half of the subjects reporting use of oxygen at home had a resting SP,O2>88%. In conclusion, the prevalence of hypoxaemia was closely related to altitude. Priorities for oxygen prescription must be defined in moderate altitudes because it is unfeasible to provide it to all subjects fulfilling the criteria commonly used.

Indoor air pollution in developing countries: a major environmental and public health challenge

Around 50% of people, almost all in developing countries, rely on coal and biomass in the form of wood, dung and crop residues for domestic energy. These materials are typically burnt in simple stoves with very incomplete combustion. Consequently, women and young children are exposed to high levels of indoor air pollution every day. There is consistent evidence that indoor air pollution increases the risk of chronic obstructive pulmonary disease and of acute respiratory infections in childhood, the most important cause of death among children under 5 years of age in developing countries. Evidence also exists of associations with low birth weight, increased infant and perinatal mortality, pulmonary tuberculosis, nasopharyngeal and laryngeal cancer, cataract, and, specifically in respect of the use of coal, with lung cancer. Conflicting evidence exists with regard to asthma. All studies are observational and very few have measured exposure directly, while a substantial proportion have not dealt with confounding. As a result, risk estimates are poorly quantified and may be biased. Exposure to indoor air pollution may be responsible for nearly 2 million excess deaths in developing countries and for some 4% of the global burden of disease. Indoor air pollution is a major global public health threat requiring greatly increased efforts in the areas of research and policy-making. Research on its health effects should be strengthened, particularly in relation to tuberculosis and acute lower respiratory infections. A more systematic approach to the development and evaluation of interventions is desirable, with clearer recognition of the interrelationships between poverty and dependence on polluting fuels.

The role of commercial plasmapheresis banks on the AIDS epidemic in Mexico

OBJECTIVE

To characterize the circumstances underlying the epidemic of AIDS associated with blood transfusion in Mexico and to explore the possible mechanisms for its dissemination.

METHODS

A retrospective analysis comparing the total number of AIDS cases and transfusion-associated AIDS cases and the male:female ratio reported in Mexico and the U.S. from 1981 to 1996 was done. We analyzed the relationship between the location of plasmapheresis banks and the geographic distribution of transfusion-associated AIDS cases and AIDS cases among paid donors in order to assess the possible role of plasmapheresis banks in its dissemination.

RESULTS

The proportion of transfusion-associated AIDS in the total number of cases was significantly higher in Mexico than in the U.S. from 1987 through 1996 (p < .0001). A rapid drop in the male:female ratio of AIDS was observed in Mexico but not in the U.S. coinciding with a growing number of transfusion associated cases; transfusion has been the main risk factor for AIDS in women in our country. In 1986, seven States and Mexico City had plasmapheresis banks: they reported 90% of the cases associated to paid donation and 75% of those associated to transfusion, despite the fact that commercial blood banks without plasmapheresis facilities existed in 23 of the other 24 States.

CONCLUSION

There was a difference on the frequency of transfusion associated AIDS between Mexico and the U.S. which reached epidemic proportions in Mexico. We believe that plasmapheresis banks played a major role in the dissemination of the infection in Mexico as paid donors provided a third of the blood used in Mexico in 1986. These findings highlight important implications for the prevention of AIDS in developing countries where commercial plasmapheresis practices are still in operation.

Prevalence of high hematocrits in patients with interstitial lung disease in Mexico City

Erythrocytosis, a known response to chronic hypoxemia, is considered infrequent in interstitial lung diseases. We studied the prevalence of high hematocrit (Hct) values and the relationship between Hct and SaO2 in 79 patients with chronic pigeon breeder's lung (PBL) and 34 with idiopathic pulmonary fibrosis (IPF), all of whom lived in the Mexico City metropolitan area (2,240 m above sea level). Lung biopsy was performed in 31 patients with IPF and 71 with PBL. We analyzed only one simultaneous measurement of Hct and SaO2 per patient (usually the initial measurement) before treatment. No additional cause for anemia or erythrocytosis was detected. Forty-eight percent of the patients with PBL (38/79) and 62 percent of those with IPF (21/34) had high Hct values (greater than 2 SD above mean values for Mexico City); in 14 (12.3 percent) of the 113 patients (nine with PBL and five with IPF), the Hct was above 60 percent. The Hct and SaO2 values displayed a poor correlation for the whole group: Hct = 65.7-0.16(SaO2), r = 0.24, p = 0.012. The correlation between Hct and SaO2 was nonsignificant if patients were separated by diagnosis. For an SaO2 of less than 80 percent, the slope of SaO2 vs Hct was zero. Half of our patients with PBL and IPF had Hct values that were high for the altitude. In most cases, Hct responses fell within the confidence limits reported as normal at high altitudes. We found a poor relationship between Hct and awake SaO2.

Exponential analysis of the lung pressure-volume curve in patients with chronic pigeon-breeder's lung

Pigeon-breeder's lung (PBL) is extremely common in Mexico City and often progresses to irreversible pulmonary fibrosis. The exponential analysis of the lung pressure-volume (PV) curve (V = A - Be-kp) has been suggested as a method to separate the lung restriction caused by inflammation from that caused by pulmonary fibrosis; a significantly decreased value for the exponential constant, k, suggests a change in the mechanical properties of the functioning lung parenchyma, while a normal value accompanied by restriction suggests subtraction of lung units without a change in the mechanical properties of the functioning units. We measured lung volumes and static PV curves in 29 patients who had persistent lung restriction following a biopsy-proven diagnosis of PBL. Mean values in the 29 subjects were as follows: age, 43 +/- 13 years; TLC, 61 +/- 15 percent of predicted; VC, 46 +/- 19 percent of predicted; and k, 55 +/- 17 percent of predicted. Twenty-four of the 29 patients had values for k that were below the 95 percent confidence level, and five had "normal" values. There was no difference in TLC and VC (percent of predicted) between those with or without a decreased value for k. Four of five patients with a normal value for k improved subsequent to diagnosis, while only one of 21 patients with a decreased k improved. We conclude that increased lung elasticity manifested by a low value for k is common in patients with chronic PBL. These results support the observation of frequent irreversible lung fibrosis in these patients. Measurements of k could prove a good prognostic indicator at the time of initial diagnosis.

Behavior of the pulmonary circulation at rest and during exercise in miliary tuberculosis

We studied the hemodynamic behavior of the pulmonary circulation at rest and during exercise in six patients with MTB. As a group, in contrast to advanced fibrocaseous tuberculosis, these patients exhibited normal pulmonary hemodynamics at rest and during exercise. Only minor abnormalities in pulmonary vascular resistance at exercise (increased PAd-PWP gradient) were noted in two of the patients. The increase in Rp during exercise does not appear to be related to acute hypoxic vasoconstruction but rather to functional changes (compliance or recruitment or both) of the pulmonary microvasculature. In the genesis of these functional changes, chronic alveolar hypoxia and the inflammatory-fibrotic process might be interacting.

PaO2 increases with coughing in patients with chronic lung disease

We considered if the cyanosis frequently observed during a cough attack in patients with chronic lung disease was due to worsening hypoxemia. To investigate the effects of cough on PaO2, we measured arterial blood gases before and after a voluntary coughing period of 45 sec, in 11 patients with Interstitial Lung Disease (ILD) and 14 patients with Chronic Obstructive Lung Disease (COPD). All patients significantly increased (p less than 0.05) their PaO2 (COPD: from 49 +/- 2 to 60 +/- 2 mmHg; ILD from 44 +/- 2 to 51 +/- 3 mmHg, mean +/- SD) and decreased their PaCO2. We conclude that stable patients with COPD and ILD increase their PaO2 with coughing most likely due to hyperventilation. The cyanosis observed could be due to peripheral circulatory effects of coughing.

Hypercapnia and sleep O2 desaturation in chronic obstructive pulmonary disease

There is a wide clinical spectrum in chronic obstructive pulmonary disease (COPD). The extremes of this spectrum, the "pink puffer" (PP) and "blue bloater" (BB) stereotypes differ in their degree of sleep hypoxemia and pulmonary hypertension. Most patients cannot be characterized as either PP or BB. The data amassed in the recent nocturnal oxygen therapy trial provide an opportunity to see to what extent differences in sleep oxygenation and hemodynamics in a large hypoxemic COPD population are related to awake hypoxemia and hypercapnia. From a large hypoxemic COPD population sleep SaO2 was examined in those with (PaCO2 greater than 44 mm Hg) and without (PaCO2 less than or equal to 44 mm Hg) hypercapnia. Hypercapnic patients (mean PaCO2 49.8 mm Hg) had the same PaO2 and degree of airflow obstruction as normocapnic patients (PaCO2 37.4 mm Hg) but had far greater sleep hypoxemia (measured by mean sleep SaO2, low sleep SaO2, and awake-low sleep SaO2, p less than 0.05). In addition, arterial blood gases of the large sleep O2 desaturaters were compared with those of the small desaturaters; PaO2 was similar in both groups, whereas PaCO2 was different (p less than 0.01). Two common subsets of hypoxemic patients were also compared; one was hypercapnic and overweight, the other normocapnic and hyperinflated. We found that patients in the hypercapnic group had far worse sleep hypoxemia, although they had better lung function. We conclude that hypercapnia is a marker for sleep O2 desaturation in hypoxemic COPD.

Perfluorochemical artificial blood as a volume expander in hypoxemic respiratory failure in dogs

The perfluorochemical O2-transport fluid, Fluosol-DA 20 percent (PFC), is being clinically evaluated as a volume expander in patients who are unable to receive blood products. Since patients treated with Fluosol-DA may be at risk of developing adult respiratory distress syndrome (ARDS) as a complication of the original disorder for which they were transfused, we examined central hemodynamics and gas exchange in anesthetized O2-ventilated dogs with oleic-acid induced pulmonary edema before and after transfusion with 400 ml of either PFC (n = 5) or whole blood (n = 5). Transfusion produced similar increases in cardiac output, pulmonary and systemic vascular pressures and intrapulmonary shunt in the two groups. Arterial O2 tension, however, fell from 209 +/- 117 to 172 +/- 81 mmHg in the blood transfused group but increased from 219 +/- 145 to 302 +/- 138 mmHg in the PFC group. Arterial O2 content, on the other hand, increased in the blood transfused group due to an increase in hematocrit, but fell with PFC because of hemodilution. This lower total arterial O2 content in the PFC group was, however, compensated for by more efficient O2 transport by the PFC in that the PFC arteriovenous O2 content difference accounted for 26 percent of the total arteriovenous O2 content difference, making it about four times as efficient as hemoglobin in tissue O2 delivery. Fluosol DA, 20 percent, is an effective volume expander in this model of hypoxemic respiratory failure, and it can transport significant amounts of O2 even in the presence of a substantial intrapulmonary shunt.

Breathing during sleep in patients with interstitial lung disease

Patients with interstitial lung disease (ILD) have a rapid shallow breathing pattern while awake that is thought to be due to activation of lung reflexes. We wondered whether sleep would result in changes in respiratory control and thus cause hypoxemia and poor sleep quality. Eleven patients with ILD (5 men and 6 women) and 11 age- and sex-matched control subjects were studied during sleep. Sleep quality was worse in patients with ILD, with more time in Stage 1 (33.7% of total sleep time (TST) versus 13.5%) and less time in REM sleep (11.8 versus 19.9% TST) than found in control subjects, and more fragmentation of sleep (13.7 +/- 3.1 arousals/h and 24.3 +/- 6.0 sleep stage changes/h versus 6.9 +/- 1.0 and 12.7 +/- 1.4, respectively). Patients with ILD with awake SaO2 less than 90% had greater abnormalities in sleep structure than did those with SaO2 greater than 90%. The incidence of apneas and hypopnea periods in patients with ILD was low (apnea plus hypoventilation index of 1.3 +/- 0.45 versus 2.9 +/- 0.82 in control subjects, p = NS). Oxygen saturation dropped during REM sleep in patients, especially in those with more severe awake hypoxemia. Expiratory time (Te), inspiratory time (Ti), and their sum (Ttot) were shorter in the patients, whereas Ti/Ttot was the same as in control subjects. No systematic changes during sleep were seen in these variables. The variability of inspiratory volume index, Ti, Te, and Ti/Ttot was similar to that in control subjects, and was lowest during NREM sleep. The incidence of snoring was comparable in patients and control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of protriptyline in obstructive sleep apnea

Protriptyline, a non-sedating tricyclic agent, was evaluated in a double blind drug-placebo crossover trial in five obese patients with obstructive sleep apnea. Four of the five patients had improvement in somnolence. Protriptyline improved oxygenation. This seemed related primarily to a reduction (from 23% to 11%) in REM, with fewer of the more severe REM apneas. Arousal frequency remained quite high; thus the reason for the reduction in somnolence remains unclear. In three patients, at six months the improvement in clinical status and oxygenation persisted. We have now attempted long term treatment in nine patients. In five, anticholinergic side-effects necessitated stopping therapy. Four patients continue to do well. A trial of protriptyline is thus indicated in treatment of mild to moderate obstructive apnea or when the patient refuses more invasive treatment.

Sighs during sleep in adult humans

We analyzed sighs (breaths with a tidal volume at least twice that of baseline breaths) during sleep in 12 normal adults. We found a total of 124 sighs in the group, with an average of 1.66 sighs/h of sleep, but with great intersubject variation (range: 1-25 sighs/night). There were sighs in all sleep stages, but there were more per hour in stage 1. 64.4% of the sighs were associated with an increase in EMG activity or EEG frequency, starting either before or immediately after the sigh. The remainder of the sighs were not associated with any arousal or sleep stage changes. The normal variability of heart rate with breathing is exaggerated during sighs, probably because of the greater inflation and the associated arousal. Sighs have larger mean inspiratory flows (Vt/Ti), expiratory flows (Vt/Te), and a larger fraction of respiratory cycle spent in inspiration (Ti/Ttot) than the previous breaths, all evidence of a change in respiratory control. Sighs during sleep may occasionally be followed by central apneas, hypoventilation, or considerable slowing of respiratory rate. Although it has been shown that a sigh renders the respiratory centers refractory to another sigh, we found that sighs sometimes occur in pairs.