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Biomedical subjects

J D Hackney

Publications and source records attributed to J D Hackney.

96 records · Page 6Linked to original sources
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Effects of 0.2 ppm nitrogen dioxide on pulmonary function and response to bronchoprovocation in asthmatics.

To study the respiratory effects of nitrogen dioxide (NO2) at ambient concentrations, we exposed 31 asthmatic volunteers to purified air (control) and to 0.2 ppm NO2 for 2-h periods with light intermittent exercise. Bronchial reactivity (loss of forced expiratory performance in response to graded doses of methacholine chloride aerosol) was determined postexposure, using a newly developed apparatus that allowed accurate quantitation of methacholine dose. Forced expiratory performance, total respiratory resistance, and symptoms were also recorded immediately pre- and postexposure (prior to methacholine challenges). No significant direct effect of NO2 exposure on forced expiratory function or total respiratory resistance was observed. Symptoms showed a small significant (p less than 0.05) excess in purified air relative to NO2 exposures. Individual responses to methacholine varied greatly. About two-thirds of the subjects showed greater response after NO2 than after purified air, but the mean excess response was small. Mean changes attained significance in some but not all applicable statistical tests. Thus we cannot conclude unequivocally that NO2 exposure increased bronchial reactivity in this group, although there was some tendency in that direction.

Adolescent↗
PubMedDate not supplied

Activity patterns in elementary and high school students exposed to oxidant pollution.

We investigated activity patterns of 17 elementary school students aged 10-12, and 19 high school students aged 13-17, in suburban Los Angeles during the oxidant pollution season. Individuals' relationships between ventilation rate (VR) and heart rate (HR) were "calibrated" in supervised outdoor walking/jogging. Log VR was consistently proportional to HR; although "calibrations" were limited by a restricted range of exercise, and possibly by artifact due to mouthpiece breathing, which may cause overestimation of VR at rest. Each subject then recorded activities in diaries, and recorded HR once per minute by wearing Heart Watches, over 3 days (Saturday-Monday). For each activity the subject estimated a breathing rate--slow (like slow walking), medium (like fast walking), or fast (like running). VR ranges for each breathing rate and activity type were estimated from HR recordings. High-school students' diaries showed their aggregate distribution of waking hours as 68% slow inside, 8% slow outside, 10% medium inside, 9% medium outside, 1.5% fast inside, 1.5% fast outside. Elementary students' distribution was 47% slow inside, 15% slow outside, 20% medium inside, 12% medium outside, 2.5% fast inside, 3.5% fast outside. Sleep occupied 38% of high-school students' and 40% of elementary students' time; HR were generally lower in sleep than in slow waking activity. High school students' mean VR estimates were 13 L/min for slow breathing, 18 for medium, and 23 for fast; elementary students' were 14 slow, 18 medium, and 19 fast. VR distributions were approximately lognormal. Maximum estimated VR were approximately 70 L/min in elementary and approximately 100 L/min in high school students. Compared to adults studied similarly, students reported more medium or fast breathing, and had equal or higher VR estimates during slow and medium breathing despite their smaller size. These results suggest that, relative to body size, young people inhale larger doses of outdoor air pollutants than adults.

Activities of Daily Living↗
PubMedDate not supplied

Time-activity patterns and diurnal variation of respiratory status in a panel of asthmatics: implications for short-term air pollution effects.

To understand the short-term health risks to people from air pollution exposure, we investigated time-activity patterns and temporal variation of the respiratory status in 49 asthmatic Los Angeles area residents 18-50 years old. During the summer (May-September) and winter (November-March), subjects measured their lung function two to four times daily at home for one week periods, and every hour recorded their symptoms, medication, and activity hourly in diaries. Almost all subjects recorded heart rates (HR), which were converted to ventilation rate (VR) estimates using individual laboratory exercise data. Most subjects' lung function and symptoms varied diurnally, and were worst in early morning. For subjects with clinically mild asthma, diurnal forced expired volume in 1 sec (FEV1) changes averaged 7%, versus 12% in those with moderate symptoms, and 18% in severely asthmatic subjects. Lung function was similar in summer and winter, but symptoms and medication use decreased in winter. In the aggregate, subjects reported spending 75% of waking hours indoors at self-rated slow activity and 11% in vehicles. HR records usually corroborated reports of medium or fast activity. Mean estimated VR at slow, medium, and fast activity was 19, 37, and 61 L/min for men, and 16, 24, and 32 L/min for women. Outdoor fast activity, representing the greatest vulnerability to outdoor pollution, occupied approximately 0.2% of waking hours (2 min/day on average); outdoor medium activity occupied about 2% of waking hours (19 min/day on average). Estimated cumulative ventilation was higher than that of previous healthy panels because of asthmatics' higher VR at slow activity. If these activity patterns are typical, asthmatics may be especially vulnerable to pollutants with effects dependent on cumulative inhaled dose. Effects dependent on high inhaled dose rates over a short period, e.g., sulfur dioxide effects, would be unlikely, except perhaps for uncommonly active individuals in uncommonly polluted areas.

Adolescent↗
PubMedDate not supplied

Short-term air pollution exposures and responses in Los Angeles area schoolchildren.

We studied 269 school children from three Southern California communities of contrasting air quality in two successive school years, to investigate short-term effects of ambient ozone (O3), nitrogen dioxide (NO2), or particulate matter (PM) on respiratory health. We measured lung function and symptoms twice daily for one week each in fall, winter and spring; and concurrently assessed time-activity patterns and personal exposures. Average daily personal exposures correlated with pollutant concentrations at central sites (r = 0.61 for O3, 0.63 for NO2, 0.48 for PM). Questionnaire-reported outdoor activity increased slightly in communities/seasons with higher pollution. Lung function differences between communities were explainable by age differences. Morning forced vital capacity (FVC) decreased significantly with increase in PM or NO2 measured over the preceding 24 hours. Morning-to-afternoon change of forced expired volume in one second (FEV1) became significantly more negative with increase in PM, NO2, or O3 on the same day. Predicted FVC or FEV1 loss on highest- vs lowest-pollution days was < 2%. Daily symptoms showed no association with current or prior 24-hour pollution, but increased with decreasing temperature. Parents' questionnaire responses suggested excess asthma and allergy in children from one polluted community while children in the other polluted community reported more symptoms, relative to the cleaner community. We conclude that Los Angeles area children may experience slight lung function changes in association with day-to-day air quality changes, reasonably similar to responses seen by others in less polluted areas. Although short-term pollution effects appear small, they should be assessed in longitudinal lung function studies when possible, to allow maximally accurate measurement of longer-term function changes.

Air Pollution↗