Key Point

Respiratory therapists are significantly more likely to develop asthma than are physical therapists.

VANCOUVER, BRITISH COLUMBIA—An elevated risk of asthma among respiratory therapists has been previously reported in two studies, one showing nearly a fivefold risk increase and the other more than a twofold risk increase.^1,2 In both studies, the excess risk appeared following participants’ entry into the respiratory therapy profession.

Because of these findings, it was recommended that efforts be made to identify potential causes of occupational asthma in respiratory therapists—a task that Helen Dimich-Ward, PhD, and colleagues undertook in their recent investigation comparing asthma risk in respiratory therapists and physical therapists.³ This study identified two particularly relevant influences on asthma risk in respiratory therapists: the administration of aerosolized ribavirin and delivery of aerosolized agents using an oxygen tent or hood.

AEROSOLIZED RIBAVIRIN IMPLICATED

An association between aerosolized ribavirin and subsequent increase in the risk of asthma is plausible because levels of ribavirin in the area around the individual administering the drug have been shown to be highest when it is delivered through an oxygen tent, explained Dr. Dimich-Ward, an Associate Professor in the Respiratory Division at the University of British Columbia in Vancouver. “Known adverse reactions to ribavirin include acute worsening of asthma, deterioration of pulmonary function, and dyspnea,” she added.

MORE ASTHMA SYMPTOMS, ELEVATED ORs

Dr. Dimich-Ward and colleagues analyzed the responses of 275 respiratory therapists and 628 physical therapists to a mailed questionaire that inquired about personal characteristics, work environment, and respiratory symptoms experienced during the preceding 12 months. The work-related section of the questionnaire asked respondents to list up to six aerosolized substances that they administered most frequently, along with the method, dose, and duration of drug delivery.

Only 8% of the respiratory therapists reported giving aerosolized agents by small-particle aerosol generator or using the ribavirin units designed specifically to deliver aerosolized ribavirin. In contrast, 90.5% said that they administered aerosols by mist mask, making that by far the most common aerosol delivery method. Sixty-seven percent of the respiratory therapists wore personal protective gear—usually, latex gloves or eye protection.

Compared to the physical therapists surveyed, respiratory therapists had higher rates of asthma attack (13% vs 6%), reported asthma (7% vs 5%), wheeze (22% vs 14%), cough (10% vs 7%), phlegm production (9% vs 7%), and being awakened by dyspnea (9% vs 5%) in the 12 months preceding the survey. The two groups reported similar rates of chest tightness (16% for the respiratory therapists and 15% for the physical therapists) and of being awakened by cough (37% in both groups) during that time.

After adjustment for age, gender, childhood asthma, and smoking status, the odds ratios (ORs) among respiratory therapists for wheeze, reported asthma, asthma attack, and being awakened by dyspnea were 2.3, 2.4, 2.6, and 2.6, respectively, compared to physical therapists.

Among respiratory therapists who administered aerosolized ribavirin, the ORs for asthma attack and reported asthma were 2.4 and 2.6. These respiratory therapists also had nonsignificant increases in the ORs for wheeze and chest tightness.

The OR for reported asthma was 8.3 among respiratory therapists who delivered aerosolized agents by oxygen tent or hood. This method of aerosol administration was also associated with significantly elevated ORs for wheeze and asthma attack of 2.5 and 3.6, respectively.

FINDINGS COULD HAVE A POSITIVE INFLUENCE

It is important to remember, stressed Dr. Dimich-Ward, that the study merely showed statistical associations and not proven cause-and-effect relationships between asthma and the risk factors studied; additional studies are needed to produce such proof. Furthermore, she acknowledged that the prevalence of reported asthma in the study was quite low.

The study’s findings, however, “may have positive effects on the health of respiratory therapists through improvements in work practices,” Dr. Dimich-Ward suggested. It could, for example, draw attention to the need for adequate general ventilation, effective scavenging systems, and aerosol containment devices.

—Timothy Begany

References
1. Kern DG, Frumkin H. Asthma in respiratory therapists. Ann Intern Med. 1989;110:767-773.
2. Christiani DC, Kern DG. Asthma risk and occupation as a respiratory therapist. Am Rev Respir Dis. 1993;148:671-674.
3. Dimich-Ward H, Wymer ML, Chan-Yeung M. Respiratory health survey of respiratory therapists. Chest. 2004;126:1048-1053.

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