Objective: To determine the expected vital capacity in persons with chronic spinal cord injury (SCI) in relation to injury level, completeness of injury, smoking and duration of injury, as an aid to diagnosis and management of respiratory complications. Setting: A New York City veterans' hospital and a Los Angeles public rehabilitation hospital. Methods: Case series from the two hospitals were pooled. Participants (adult outpatients with SCI of duration 41 year, not ventilator-dependent) were evaluated by conventional forced expiratory spirometry. Cross-sectional analysis was performed, using multiple regression, on the entire population and de®ned subgroups. The principal outcome measure was forced vital capacity (FVC). Results: In the subjects with complete-motor lesions, FVC ranged from near 100% of normal predicted values in the group with low paraplegia, to less than 50% in those with high tetraplegia. Incomplete lesions mitigated FVC loss in tetraplegia. In subjects with paraplegia, longer duration of injury was associated with greater loss, and smoking-related loss was evident at older but not at younger ages, presumably due to greater pack years in older subjects. Conclusions: Vital capacity/SCI level relationships determined here may have diagnostic and prognostic value. Smoking-related FVC loss is important in persons with SCI as in others, although at higher levels it may be obscured by SCI-related loss.
The development of attenuated response ("tolerance") to daily ozone (O3) exposures in the laboratory is well established in healthy adult volunteers. However, the capability of asthmatics to develop tolerance during multiday ozone exposures is unclear. We exposed 10 adult volunteers with mild asthma to 0.4 ppm O3 in filtered air for 3 h/d on 5 consecutive d. Two similar filtered-air exposures during the preceding week served as controls. Follow-up O3 exposures were performed 4 and 7 d after the most recent consecutive exposure. All exposures were performed in an environmental chamber at 31 degrees C and 35% relative humidity. The subjects performed moderate exercise (mean ventilation rate of 32 l/min) for 15 min of each half-hour. Responses were measured with spirometry and symptom evaluations before and after each exposure, and a bronchial reactivity test (methacholine challenge) was conducted after each exposure. All response measurements showed clinically and statistically significant day-to-day variation. Symptom and forced-expiratory-volume-in-1-s responses were similarly large on the 1st and 2nd O3 exposure days, after which they diminished progressively, approaching filtered air response levels by the 5th consecutive O3 day. This tolerance was partially lost 4 and 7 d later. Bronchial reactivity peaked after the first O3 exposure and remained somewhat elevated after all subsequent O3 exposures, relative to its control level following filtered-air exposures. Individual responses varied widely; more severe initial responses to O3 predicted less rapid attenuation. We concluded that asthmatics can develop tolerance to frequent high-level O3 exposures in much the same manner as normal subjects, although the process may be slower and less fully effective in asthmatics.
Symptoms represent an important dimension of people's responses to irritant air pollutants and deserve careful attention in clinical exposure studies. Scientific investigation is handicapped somewhat in that symptoms cannot be verified objectively, nor can they be quantitated rigorously like common physiological observations. Symptom evaluations in exposure studies may take the form of verbal descriptions, incidence or prevalence rates (counts of symptomatic versus asymptomatic subjects), or scores on an arbitrary ordinal scale (for example, with larger numbers representing greater degrees of severity). Our experience supports the use of written multiple-choice questionnaires with ordinal scoring. In groups of subjects large enough for meaningful statistical analyses, the questionnaire technique compares favorably with pulmonary physiological tests, in terms of its sensitivity in detecting responses to pollutant exposure. However, any given individual may show little correlation between symptoms and physiological response. Widespread standardization of symptom questionnaires has been useful in epidemiology and should by considered in clinical exposure studies.
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