Day Care and Older Siblings Protect Children from Asthma
According to a recent study, infants who attend day care or have older siblings are protected from developing asthma later in life. The research, which was a collaboration of the Arizona Respiratory Sciences Center and the Steele Memorial Children’s Research Center at the University of Arizona Health Sciences Center, Tucson, was published in the New England Journal of Medicine.

“The huge increase in the numbers of children with asthma worldwide, particularly in developed countries, has been well documented,” says Thomas M. Ball, MD, MPH, assistant professor of clinical pediatrics at the University of Arizona, who conducted the study. “It’s crucial to better understand the biological causes of the current asthma epidemic in order to develop new approaches to asthma prevention.”

The study followed more than 1,000 children who have been part of the Tucson Children’s Respiratory Study from birth. Studying more than 15 years of collected data on the children’s health and environment, researchers looked at two specific variables—older siblings and day care—to determine their impact on asthma development.

Clinical tests were used to ascertain the children’s susceptibility to allergies, a factor that contributes to the likelihood of developing asthma. Children were also evaluated for frequent wheezing. Researchers found that children who attended day care during the first 6 months of life, or had two or more older siblings, were less allergic at ages 6 and 11 and wheezed less at ages 6 and 13 than children who did not attend day care or have older siblings.

“One theory suggests that infections play an important role in the maturation of the immune system, causing the immune system to become less allergic,” says senior author Anne L. Wright, PhD, research professor of pediatrics at the University of Arizona. “This study supports the view that infections, or exposure to other children, protect against the development of asthma and allergies.”

Gastroesophageal Reflux May Be Associated with Asthma
Susan M. Harding, MD, from the Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, and two colleagues found that 16 of 26 stable asthma patients without gastrointestinal reflux symptoms showed abnormal levels of esophageal acid when tested over a 24-hour period. The research was published in the July issue of the American Journal of Respiratory and Critical Care Medicine.

Researchers say that patients with symptomatic gastroesophageal reflux had more severe asthma than asymptomatic patients, and that the role of acid reflux in asthma is not known at this time. They note that research has shown that treating gastroesophageal reflux improves asthma control.

Thirty patients with reflux symptoms served as controls, while 26 patients without symptoms were tested. Of these 26, nine had mild asthma, 16 had moderate disease, and one had severe asthma. Investigators used 24-hour pH testing to measure the reflux acidity. They placed two pH electrodes with a catheter through the patient’s nose into the upper and lower portion of the esophagus.

Continuing their daily activities and avoiding acidic foods, patients recorded when they ate meals, when they lay down to sleep, and when they arose in the morning. They also recorded respiratory and esophageal symptoms during the 24-hour period. Researchers say that false-positive results from the test are rare.

The research team found that patients with asymptomatic gastroesophageal reflux had higher amounts of acid, and advised that “clinically silent” reflux patients be included in future studies that evaluate asthma outcome. They also urged that the use of aggressive antireflux therapy also needs investigation.

New Lung Function Data for Chinese Children and Adolescents
New research by Mary S.M. Ip, MD, Department of Medicine, Queen Mary Hospital, Hong Kong, People’s Republic of China, and four associates found that flow volume capacity (FVC) in Hong Kong-born Chinese boys is 8% to 10% lower than figures for white children. A significant increase in forced expiratory volume in 1 second (FEV1) was reported compared with prior Hong Kong data on Chinese children from 1985. The study, which centered on new lung function data, was conducted with information from 392 male and 460 female Hong Kong-born Chinese children and adolescents between the ages of 7 and 19.

The children filled out a questionnaire, underwent pulmonary function testing at seven schools, and were measured for height, weight, arm span, and other physiologic variables. The study points to external factors, such as childhood health, environmental smoke and pollution, nutritional status, and exercise, as the contributing elements to differences in pulmonary function among races. These factors can impact the size and shape of the rib cage, respiratory muscle strength, and lung development.

Ip found that height was the most important physiologic variable. “Compared with over a decade ago, this study, using height-adjusted values, showed an increase in FVC and FEV1 for both boys and girls across all height groups,” Ip says. “Girls demonstrated a particular improvement. Our research highlights the importance of obtaining updated normative values for lung function in different populations at varying intervals.” The study was published in the August issue of the American Journal of Respiratory and Critical Care Medicine.

Sleep Apnea May Require Two-Night Test for Diagnosis
Although a one-night test is standard for a sleep apnea diagnosis, a second session may reduce false-negative results and misdiagnoses, according to a study conducted by Olivier Le Bon, MD, of the Brugmann Hospital Sleep Unit, Brussels, Belgium, and six associates.

Sleep apnea affects approximately 18-25 million Americans, but fewer than 1 million are aware of their condition. Expenses from loss of productivity, industrial and personal accidents, and medical bills cost society about $60 billion annually.

“Our study confirms that an important number of patients presented false-negative results on night one, which turned out to be more frequent among severe cases,” Le Bon says. “This underscores the need for a second test recording when the results of night one are negative.”

Researchers studied 243 patients admitted to the unit between 1992 and 1998 to determine if they had sleep apnea-hypopnea syndrome. All of the patients experienced excessive daytime sleepiness, fatigue, snoring, or sleep interruption. Patients were tested during two separate nights.

During the first night, 101 patients had an apnea-hypopnea index (AHI) of more than 20 events per hour, and 74 of these patients, who were not part of the night two comparative data, tried nasal continuous positive airway pressure (nCPAP) on the second night.

“The comparison between nigh one and night two recordings indicates a clear classic first-night effect (on night one) as shown by a shorter sleep period and less total sleep time, worse sleep efficiency, longer sleep onset latency, more wake time after sleep onset, a higher awakening index, less rapid eye movement sleep time, and long rapid eye movement sleep latency.” Le Bon says.

The comparison group for night two included 169 individuals who did not use nCPAP therapy. Of these, 62 patients scored higher than 20 AHI, while 32 patients’ scores dropped.

“This study proves it is worth performing two consecutive sleep test sessions or at least a second one when the results of testing on the first night are negative in all patients admitted for sleep apnea detection,” Le Bon says. The study was published in the August issue of Chest.

Study Shows Diesel Exhaust Pollution of Increasing Concern
Ten healthy, nonsmoking volunteers participated in a recent study that tested the respiratory effects of diesel exhaust exposure. Peter J. Barnes, MD, of the Department of Thoracic Medicine, National Heart and Lung Institute, London, and his associates discovered an inflammatory response to inhaled diesel exhaust. The study was published in the July issue of the American Journal of Respiratory and Critical Care Medicine.

The participants, who had an average age of 28 years, were exposed to diesel particles collected from the exhaust vent of a stationary diesel engine under conditions chosen to represent the operating conditions of a light-duty vehicle. The subjects returned after a 4-week period for an alternative exposure to either air or diesel exhaust.

The participants, who had normal lung function and no history of respiratory or allergic disease, experienced no change in cardiovascular parameters or lung function. However, researchers measured increases in neutrophils, or large white blood cells that ingest antigens, in the sputum of eight of the 10 volunteers. An increased level of hemoprotein and higher exhaled carbon monoxide levels indicating oxidant stress were also recorded after a 2-hour exposure to the tiny diesel exhaust particles in a test chamber.

Researchers note that diesel exhaust particles compose the majority of traffic pollution. They say that although the test subjects did not experience adverse effects or symptoms, road traffic should still be considered a public health problem.

HIV-Related PCP Survival Rates Increase with Respiratory Support, Study Says
In a recent study that shows a 40% rise in survival rates for patients requiring mechanical ventilation, researchers urge physicians to reconsider the withdrawal of respiratory support for patients with HIV-related Pneumocytis carinii pneumonia (PCP) who have suffered severe respiratory failure. The study appeared in the August issue of the American Journal of Respiratory and Critical Care Medicine.

J. Randall Curtis, MD, MPH, of the Division of Pulmonary and Critical Care Medicine, University of Washington and Harborview Medical Center, Seattle, and four associates researched the hospital records of 1,660 PCP patients in 71 public and private hospitals in seven geographic areas in the United States. They reported a twofold improvement in patient survival rates during 1995-1997, when antiretroviral therapy was introduced to fight HIV, versus 1992-1995.

Of the 1,660 hospitalized patients, 237 were admitted to intensive care units with 155 receiving mechanical ventilation for respiratory failure. Of these, nearly 40% survived to hospital discharge.

Investigators noted that patients on mechanical ventilation for more than 2 weeks had a 17% survival rate, not zero as reported in some smaller studies. About 33% of those who received mechanical ventilation for 1 to 2 weeks survived, and more than 40% survived after less than a week of mechanical ventilation.