EFFECTS OF DEEP BREATHING ABSENT IN COPD

In patients with asthma, the bronchodilatory effect of deep inspiration is impaired. To assess this phenomenon in COPD, Scichilone et al studied 19 patients with COPD and 17 healthy controls. They found that in COPD patients, deep inspiration does not produce a bronchodilatory effect.

All participants underwent clinical and functional assessment of lung function. The bronchodilatory effect of deep inspiration was measured following methacholine administration. In both groups, the amount of methacholine needed to produce a reduction in inspiratory vital capacity was similar.

Following deep inspiration, methacholine-induced bronchoconstriction was partially reversed in the control group but not in patients. Although aging reduces the effectiveness of lung inflation, in patients with COPD, disease status was the strongest predictor of bronchodilation on deep inspiration.

The authors proposed that disease-related structural changes in the lungs of COPD patients diminish the effect of deep inspiration on bronchoconstriction and may contribute to the chronic respiratory symptoms experienced by COPD patients.

Scichilone N, Marchese R, Catalano F, et al. Bronchodilatory effect of deep inspiration is absent in subjects with mild COPD. Chest. 2004;125:2029-2035.

A NEGATIVE RESULT FOR POSITIVE PRESSURE

Can noninvasive positive pressure ventilation (NPPV) decrease the need for reintubation after initially successful ventilator weaning? No, according to a large multicenter trial reported on by Esteban et al. They found no difference in reintubation rates among NPPV recipients—and a possible increased mortality risk.

Extubated patients who had received mechanical ventilation for at least 48 hours were randomized to receive either standard medical therapy (supplemental oxygen, physiotherapy, and bronchodilators) or NPPV. In patients who required reintubation, the single most relevant reason was recorded.

A total of 221 patients were recruited from 37 ICUs. One hundred fourteen received NPPV, and 107 received standard medical care. Of the patients who were reintubated, twenty-one patients in the NPPV group died, compared to 11 in the standard-care group.

Overall, there was no difference between groups in the number of patients needing reintubation. The median time between development of respiratory failure and reintubation was 12 hours in the NPPV group and two and one-half hours in the standard-care group. In both groups, the median length of stay in the ICU was 18 days.

The investigators acknowledged the possibility that the delay in reintubation after respiratory failure influenced the mortality rate in the NPPV group.

Esteban A, Frutos-Vivar F, Ferguson ND, et al. Noninvasive positive-pressure ventilation for respiratory failure after extubation. N Engl J Med. 2004;350:2452-2460.

OK TO WITHHOLD ANTICOAGULANTS AFTER SINGLE ULTRASONOGRAPHY?

Deep venous thrombosis (DVT) is diagnosed via ultrasonography, which is usually repeated after five to seven days. However, repeated ultrasonography is inconvenient, and some patients do not return for their follow-up examinations. Stevens et al evaluated the use of a single comprehensive duplex ultrasonography in detecting DVT and justifying the decision to withhold anticoagulant therapy. They found that it is safe to withhold anticoagulant therapy on the basis of a single comprehensive duplex ultrasonography.

Patients were referred because of a suspected first episode of DVT of the leg. All patients underwent comprehensive duplex ultrasonography. Patients who did not have evidence of DVT, and for whom anticoagulants were withheld, were interviewed three months after their ultrasonography. Patients with symptoms suggestive of DVT were evaluated with repeat ultrasonography after three months. The primary outcome was venous thromboembolism.

Four hundred forty-five patients took part in the study. According to comprehensive duplex ultrasonography, DVT was not apparent in 384 patients (negative cohort) and 61 patients had acute DVT. At three months, 22 patients who initially tested negative had symptoms suggestive of DVT. Three patients had DVT according to comprehensive duplex ultrasonography, making the overall rate of symptomatic venous thrombosis 0.80% in the negative cohort. The remaining symptomatic patients in the negative cohort were not given any anticoagulant therapy—none had evidence of venous thromboembolism three months later.

The authors concluded that withholding anticoagulant therapy on the basis of a single comprehensive duplex ultrasonography results in a low rate of venous thromboembolism during three months of follow-up.

Stevens SM, Elliott CG, Chan KJ, et al. Withholding anticoagulation after a negative result on duplex ultrasonography for suspected symptomatic deep venous thrombosis. Ann Intern Med. 2004;140:985-991.

STREPTOKINASE IMPROVES OUTCOMES IN PATIENTS WITH EMPYEMA

Intrapleural streptokinase has been shown to increase fluid drainage and improve outcomes in patients with pulmonary infections. Diacon et al performed a randomized controlled trial evaluating the effect of streptokinase on the need for surgery and on long-term outcomes: Streptokinase, used with chest tube drainage, improves survival and reduces the need for surgery in patients with pleural empyema.

Patients with lung infections and pleural effusion and empyema were included. Chest tubes were inserted and patients received rinse solutions containing 100 mL of saline or saline plus 250,000 IU of streptokinase. Patients also received broad-spectrum antibiotics, which were adjusted following culture results. The primary outcomes measured were death, response to treatment, and need for surgery.

Forty-four patients were randomized to each pleural rinse group. Streptokinase significantly improved outcomes when used as an adjunct to chest tube drainage. Ten patients in the saline group were referred for surgery, compared to three in the streptokinase group.

In this study, the benefits of streptokinase therapy appeared three to seven days after chest drain insertion. This delay may have been due to the severity of the patients’ illness.

Diacon AH, Theron J, Schuurmans MM, et al. Intrapleural streptokinase for empyema and complicated parapneumonic effusions. Am J Respir Crit Care Med. 2004;170:49-53.

RHINOVIRUS IN OFFICE BUILDINGS RELATED TO VENTILATION

The literature has suggested that the incidence of viral respiratory infections can be reduced by increasing ventilation in buildings. By taking air samples and using the concentration of exhaled breath (CO₂) as an indicator of office ventilation, Myatt et al demonstrated that workers in office buildings with a low outdoor air supply may be at increased risk for transmission of respiratory viruses.

Three office buildings were studied over 20 months. All offices had large open areas with cubicles surrounded by private offices. Air filters were used to sample the amount of CO₂ in the office buildings. Air samples were collected weekly at centralized locations from 9 AM to 5 PM. Building workers with upper respiratory tract infections were asked to volunteer a nasal mucus sample. Samples were tested for viruses using polymerase chain reaction.

A total of 181 filters were analyzed with an average sampling time of 47 hours. Of these, 58 were positive for picornavirus. Twenty-nine office workers identified themselves as having cold symptoms. Of these, 17 had detectable respiratory microorganisms. Four of 10 samples that were positive for picornavirus were collected the same week or the week after an air sample from that building also tested positive.

Exhaled breath samples greater than 30 L were correlated with detection of airborne rhinovirus. Thus, lower ventilation rates resulting in increased CO₂ levels increased the risk of exposure to infectious droplets. The authors noted that these results were from well-ventilated office buildings and recommended that similar studies be performed in schools, which have poorer ventilation and higher rates of respiratory infections.

Myatt TA, Johnston SL, Zuo Z, et al. Detection of airborne rhinovirus and its relation to outdoor air supply in office environments. Am J Respir Crit Care Med. 2004;169:1187-1190.

ORAL CORTICOSTEROIDS MAY ADVERSELY AFFECT PERINATAL OUTCOMES

Asthma can complicate pregnancy, but what about asthma therapies? Findings from two multicenter studies sponsored by the National Institutes of Health and the National Institute of Child Health and Human Development showed that theophylline, inhaled ß-agonists, and inhaled corticosteroids do not adversely affect pregnancy outcomes. However, oral corticosteroids were associated with preterm delivery and low birth weight.

The studies included 2,123 pregnant women with asthma. Medication use was recorded for all participants, and perinatal data were obtained from postpartum chart reviews.

The use of inhaled ß-agonists, inhaled corticosteroids, theophylline, or nedocromil-sodium were not associated with adverse perinatal outcomes. Oral corticosteroid use was associated with an increased incidence of preterm birth (but not stillbirth) and low birth weight (Table). These associations remained even after adjusting for relevant covariates.

Although more adverse outcomes occurred in infants born to mothers who used oral corticosteroids during pregnancy, it was unclear whether the medication or the severity of the mother’s asthma was the cause.

Schatz M, Dombrowski MP, Wise R, et al. The relationship of asthma medication use to perinatal outcomes. J Allergy Clin Immunol. 2004;113:1040-1045.

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