Biomedical subjects

W C Adams

Publications and source records attributed to W C Adams.

77 records · Page 5Linked to original sources

PubMedDate not supplied

Duration of enhanced responsiveness upon re-exposure to ozone.

It has been repeatedly observed that ozone (O3) re-exposure within 24 h elicits enhanced pulmonary function responses. However, there are only limited observations concerning re-exposure to O3 at intervals between 24 h and several days. The present study was designed to assess the effects of re-exposure to 0.35 ppm O3 at intervals of 24, 48, 72, and 120 h. Forty young adult male subjects were assigned randomly to one of four groups in ascending order of time to re-exposure (groups 1-4). Each exercised on a bicycle ergometer for 60 min at a workload that elicited a mean ventilation of 60 l/min on three occasions: protocol 1 (P1), filtered air (FA); protocol 2 (P2), 0.35 ppm O3; and protocol 3 (P3), 0.35 ppm O3. In addition to standard pulmonary function measures, specific airway resistance (SRaw); exercise ventilatory pattern, i.e., respiratory frequency (fR) and tidal volume (VT); and subjective symptoms (SS) were assessed. Statistical analysis revealed significant differences (p less than .05) for all groups between the FA (P1) responses and those for the two O3 exposures (P2, P3) for forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), SRaw, fR, VT, and SS. When the two O3 exposures (P2 and P3) were compared, only group 1 (24 h) responses were statistically significant upon re-exposure: FEV1.0, -16.1 vs. -30.4% (p less than .003); SRaw, 20.5 vs. 34.5% (p less than .05); fR, 44.2 vs. 65.3% (p less than .001); and SS (p less than .015).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMedDate not supplied

Oral and oronasal breathing during continuous exercise produce similar responses to ozone inhalation.

Breathing route has a profound effect on sulfur dioxide-induced pulmonary function response in human subjects. There is comparatively little evidence of the effects of oral, nasal, and oronasal breathing on ozone (O3)-induced responses in humans. In this study, six young adult males were exposed on five occasions to 0.40 parts per million (ppm) O3 while exercising continuously at one of two workloads (minute ventilation, VE, of approximately 30 and 75 l/min). The VE exposure time product was similar for all protocols. Four exposures were delivered randomly with a Hans-Rudolph respiratory valve attached to a silicone facemask, with breathing route effected with and without noseclip. A 2 x 2 analysis of variance revealed no statistically significant differences (p less than .05) across conditions in pulmonary function, exercise ventilatory pattern, or subjective symptoms responses. The fifth exposure, delivered via the same respiratory valve with mouthpiece, but without facemask, revealed significantly greater forced expiratory volume in 1 s (FEV1.0) impairment than that observed for the respiratory valve, facemask with noseclip exposure (-20.4% and -15.9%, respectively). The latter suggests partial O3 reactivity to the facemask and clean shaven facial surface of the subjects, although reduced oral scrubbing by mouthpiece-induced bypassing of the oral vestibule might account, in part, for this difference. Recent O3 uptake evidence from another laboratory, however, supports our conclusion that breathing route during moderate and heavy continuous exercise does not affect acute physiologic responses to 0.40 ppm O3.

Adult↗

PubMedDate not supplied

Pulmonary function response to equivalent doses of ozone consequent to intermittent and continuous exercise.

The effects on pulmonary function of inhaling the same effective dose of ozone, as well as subjective responses during continuous exercise and intermittent exercise, were studied in 12 aerobically trained men. Each subject completed 1 h of continuous exercise at work rates that elicited a mean minute ventilation of 60 l/min, and two additional 2-h intermittent exercise exposures eliciting a mean exercise minute ventilation of 45-47 l/min (i.e., total minute ventilation for each protocol was approximately 3,600 l). Subjects were exposed in randomized sequence to 0.30 ppm ozone on three occasions and to filtered air on three occasions. Forced expiratory volume in 1 s decrements of -17.6%, -17.0%, and -17.9%, respectively, for the 1-h continuous exercise exposure and the two 2-h intermittent exercise exposures to 0.30 ppm ozone were significantly different. Exposure to ozone caused significant differences between postexposure subjective symptom responses; that is, responses associated with continuous exercise were greater than those for either intermittent exercise protocol. However, the overall symptom severity responses during the last minute of exercise for the two intermittent exercise protocols (at 90 and 105 min, respectively) were not significantly different from the continuous exercise postexposure value. The findings indicate that when the ozone effective dose is equivalent at a given ozone concentration, there is no difference between pulmonary function responses to continuous exercise or intermittent exercise exposures of 2-h duration (or less), although subjective symptoms are reduced somewhat during the last rest period of intermittent exercise.

Adult↗

PubMedDate not supplied

Effects of ozone exposure at ambient air pollution episode levels on exercise performance.

Ozone is a principal component of photochemical air pollution endogenous to numerous metropolitan areas, which may induce irritant effects on the respiratory tract which impair pulmonary function, result in subjective symptoms of respiratory discomfort, including cough and shortness of breath, and can limit exercise performance. The effects of moderate ambient photochemical air pollution observed in a mobile laboratory have also been shown to be similar to those induced in laboratory chamber exposures to the same level of ozone alone. The metabolic demand of exercise increases minute ventilation (VE) and thus, the rate of ozone inhalation over that at rest. Potentially, exercise can also enhance the effects of ozone by: (a) reducing nasal passage absorption; (b) increasing the uniformity of ventilation throughout the lungs; and (c) replacing reacted ozone at a faster rate. However, results from 2-hour intermittent exercise and 1-hour continuous exercise exposures at the same total ventilation and ozone concentration have been shown to yield similar pulmonary function effects. It has been shown via significant variation in exercise intensity, and thus VE, that the simple product of ozone concentration, VE and exposure time (termed the ozone effective dose) predicts pulmonary function and exercise ventilatory pattern (induced rapid, shallow breathing) effects more precisely than ozone concentration alone. Better prediction of pulmonary function effects has been achieved via multiple regression analysis in which ozone concentration is given a greater weighting than VE and exposure time. Light intermittent exercise was first studied in 2-hour laboratory exposures to ozone at concentrations rarely seen in the ambient environment. In recent studies, heavy continuous exercise has been used in 1-hour exposures to ozone at levels routinely observed in photochemical episodes (less than or equal to 0.35 ppm). Statistically significant impairment of exercise performance has been observed at 0.18 ppm, a level reached for 1 hour, or more, on about 180 days per year in the Los Angeles basin. Responses of subpopulation groups, such as children, young adult females, older adults, and those with pre-existing pulmonary disease are not notably different from those of young adult males provided that the ozone effective dose is proportional to body size. Conversely, highly trained endurance athletes demonstrate significant responses at rather low ozone concentrations due to their ability to sustain very high VE over prolonged periods.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMedDate not supplied

Dynamic ultrasonographic measurement of passive coxofemoral joint laxity in puppies.

A new method of dynamic ultrasonographic evaluation of passive coxofemoral joint laxity was used to examine a total of 30 greyhound (n = 13) and nongreyhound (n = 17) puppies. Puppies were evaluated sonographically at four, six, eight, 12, 16, and 26 weeks of age. The coxofemoral joints were distracted manually, and the femoral head displacements were measured during distraction. The greyhounds had significantly smaller (p less than 0.01) maximum distraction distance (mean +/- standard deviation [SD], 0.11 +/- 0.04 cm) than nongreyhound puppies (mean +/- SD, 0.26 +/- 0.10 cm). In six- to eight-week-old puppies, the maximum distraction distance was correlated significantly (p of 0.0001, adjusted correlation coefficient [r2] of 0.27) with stress radiographic indices. Coxofemoral joints interpreted as being abnormal on hip-extended radiographs taken at one year of age were associated significantly (p of 0.0001) with higher maximum distraction distances in six- to eight-week-old puppies.

Analysis of Variance↗