CPAP PLACEBO DEMONSTRATES TREATMENT'S EFFECTIVENESS

Continuous positive airway pressure (CPAP) is believed to be the best treatment for sleep apnea/hypopnea syndrome (SAHS), but until recently its efficacy had never been clearly proved. The development of a sham CPAP treatment as placebo allowed a randomized trial to demonstrate CPAP’s effectiveness in improving daytime function and SAHS-related symptoms.

Montserrat et al stratified 48 patients with moderate to severe SAHS into four groups according to the severity of their disease. These groups were then randomized to receive either optimal or sham CPAP for six weeks. The Epworth Sleepiness Scale (ESS), Functional Outcomes Sleep Questionnaire (FOSQ), and Short Form Health Survey were completed by all patients at inclusion and again by the 45 patients who completed follow-up. Ten days of washout followed, and the placebo group was reassessed before and after follow-up treatment with optimal CPAP.

The researchers found that FOSQ measures of vigilance, general productivity, relief of sleepiness, and other SAHS-related symptoms were better in the group receiving optimal CPAP than in the placebo cohort. Furthermore, the placebo cohort experienced improvement in ESS scores after subsequently being treated with optimal CPAP. The researchers concluded that CPAP is effective in treating moderate to severe SAHS.

Montserrat JM, Ferrer M, Hernandez L, et al. Effectiveness of CPAP treatment in daytime function in sleep apnea syndrome. Am J Respir Crit Care Med. 2001;164:608-613.

WASTING PREDICTS CF OUTCOMES

Body wasting is a significant predictor of survival for patients with cystic fibrosis (CF). Independent of lung function and of arterial oxygen tension (PaO2) and carbon dioxide tension (PaCO2), this measurement reliably predicts outcome for at least five years.

Sharma et al studied 584 CF patients with a mean age of 21 years. Forced expiratory volume in one second (FEV1) averaged 26% of predicted. PaO2 and PaCO2 averaged 9.8 and 5.0 kPa, respectively, and average body weight was 92% of ideal. Neither patients’ age nor sex was predictive of outcome after five years. However, patients’ weight was predictive: 83% of subjects weighing more than 85% of ideal survived past five years, compared with 54.3% of those who weighed 85% of ideal or less. Additionally, patients with FEV1 greater than 30% of predicted had significantly better outcomes than did those whose FEV1 was 30% or less. Neither PaO2 nor PaCO2 was found to accurately predict survival.

Probability of death increased most dramatically as body weight fell. The researchers stated that the development of cachexia in CF patients should be considered a serious warning sign. They recommend that cachexic patients be considered for lung or heart-lung transplantation earlier than patients with normal nutritional status. Delaying transplant surgery to improve nutritional status first would not have a positive result, they said; previous work has demonstrated that preoperative body mass does not influence survival after surgery.

Sharma R, Florea VG, Bolger AP, et al. Wasting as an independent predictor of mortality in patients with cystic fibrosis. Thorax. 2001;56:746-750.

ANTI-INFLAMMATORIES UNDERUSED BY INNER-CITY KIDS WITH ASTHMA

Because asthma is a major cause of morbidity in inner-city children, Warman et al attempted to determine how sociodemographics influenced asthma treatment in this population. They found that only about one third of inner-city children with asthma were receiving daily anti-inflammatory agents.

The study’s subjects were 219 children who had been hospitalized with asthma between January 1995 and September 1996. The researchers determined the subjects’ asthma severity by asking their caregivers about the frequency of nocturnal and daily symptoms during the preceding four weeks. The children were then classified according to 1997 National Asthma Education and Prevention Program (NAEPP) guidelines.

Overall, only 35% of the children were given anti-inflammatory agents on a regular basis. Even more alarming, the researchers found that although 83% of the children met NAEPP criteria for persistent asthma, just 39% of those with persistent asthma received anti-inflammatory therapy on a daily basis. Even among the children with moderate to severe asthma, anti-inflammatory treatment was often inadequate: Only 42% of them received these agents daily.

No sociodemographic factors were found to influence whether a child would receive anti-inflammatory medications. However, families with a primary care provider and those who knew how to reach their child’s physician were twice as likely as were other caregivers to report that their children were using daily anti-inflammatories.

Warman KL, Silver EJ, Stein REK. Asthma symptoms, morbidity, and antiinflammatory use in inner-city children. Pediatrics. 2001;108:277-282.

PEF POOR PREDICTOR OF SMALL AIRWAYS FUNCTION

Although peak expiratory flow (PEF) measurements are recommended as follow-up for patients with asthma, they may not be effective in predicting small airways obstruction in asthmatic children.

Goldberg et al compared this measurement with forced expiratory flow at 50% of vital capacity (FEF50) in 111 asthmatic children. The children were grouped into one of three categories, depending on whether forced expiratory volume in one second (FEV1) was within normal range, mildly reduced, or moderately to severely reduced. The researchers found an overall correlation between FEF50 and PEF, but in 42% of the patients there was a difference of more than 20% between actual FEF50 and that calculated through PEF measurements.

Surprisingly, PEF was best able to predict FEF50 in the patients with moderate to severe asthma. Among the patients with normal FEV1, the correlation between PEF and FEF50 had only borderline significance, and there was no correlation between the two variables among those with mild disease. The variability in PEF’s accuracy in predicting FEF50 was sufficiently great that the researchers ruled out PEF as a reliable indicator of small airways obstruction. Thus, they recommend that home PEF monitoring be augmented by regular spirometric analysis.

The researchers acknowledge that no association has yet been established between FEF50 and the clinical status of asthma patients. Nevertheless, they believe that accurate assessment of small airways function will have an important role in asthma treatment.

Goldberg S, Springer C, Avital A, et al. Can peak expiratory flow measurements estimate small airway function in asthmatic children? Chest. 2001;120:482-488.

GUIDELINES DO NOT PREDICT PEDIATRIC PNEUMONIA

Recent guidelines have suggested that pneumonia can be excluded in young children if respiratory distress, tachypnea, crackles, and decreased breath sounds are absent. An observational study conducted by Rothrock et al has disproved this conclusion.

In this four-month study, 329 children 5 years or younger were eligible for evaluation. Chest films were used to evaluate patients for pneumonia; a final diagnosis was made when senior board-certified radiologists interpreted films and confirmed the presence of pneumonia or an infiltrate. Isolated atelectasis, pleural effusion, or elevated hemidiaphragm were not included in the diagnosis of pneumonia. Rothrock et al found that 67 of the 329 children (20%) had pneumonia. The guidelines demonstrated only 45% sensitivity and 66% specificity for the disease. Positive and negative predictive values were 25% and 82%, respectively.

One problem cited as a reason for the guidelines’ poor predictive value was variations in the definition of tachypnea used in previous studies, which could range from 40 to 59 breaths per minute. Rothrock et al also suggested that high interobserver variability has clouded the definition of respiratory distress and rales, making unreliable any guidelines incorporating these as diagnostic criteria for pneumonia. Before guidelines are made available for clinical use, the authors concluded, they should be prospectively evaluated in clinical settings, must comprise reproducible criteria, and must minimize interobserver variability.