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Biomedical subjects

D H Horstman

Publications and source records attributed to D H Horstman.

13 recordsLinked to original sources
PubMed1991

An air quality data analysis system for interrelating effects, standards, and needed source reductions: Part 11. A lognormal model relating human lung function decrease to O3 exposure.

Forced expiratory volume in 1 second (FEV1) was measured in 21 men exercising while exposed to four O3 concentrations (0.0, 0.08, 0.10, and 0.12 ppm). A lognormal multiple linear regression model was fitted to their mean FEV1 measurements to predict FEV1 percent decrease as a function of O3 concentration and exposure duration. The exercise level used was probably comparable to heavy manual labor. The longest O3 exposure studied was 6 h. Extrapolating cautiously to an 8-h workday of heavy manual labor, the model predicts that O3 concentrations of 0.08, 0.10, and 0.12 ppm would decrease FEV1 by 9, 15, and 20 percent, respectively.

Adult↗
PubMed1990

Ozone concentration and pulmonary response relationships for 6.6-hour exposures with five hours of moderate exercise to 0.08, 0.10, and 0.12 ppm.

The magnitudes of pulmonary responses we previously observed (1) following 6.6-h exposures to 0.12 ppm ozone (O3) suggested that responses would also occur with similar exposures at lower O3 concentrations. The objective of this study was to determine the extent of pulmonary function decrements, respiratory discomfort, and increased airway reactivity to methacholine induced by exposure to O3 below 0.12 ppm. Separate 6.6-h chamber exposures to 0.00, 0.08, 0.10, and 0.12 ppm O3 included six 50-min periods of moderate exercise (VE approximately equal to 39 L/min, HR approximately equal to 115 bpm, and VO2 approximately equal to 1.5 L/min). Each exercise period was followed by 10 min of rest. A 35-min lunch break was included midway through the exposure. Although not intended as an exact simulation, the overall duration, intensity, and metabolic requirements of the exercise performed were representative of a day of moderate to heavy work or play. Preexposure FEV1 averaged 4.39 L, and essentially no change (+0.03 L) occurred with exposure to 0.00 ppm O3. Significant decreases (p less than 0.01) of -0.31, -0.30, and -0.54 L were observed with exposures to 0.08, 0.10, and 0.12 ppm, respectively. The provocative dose of methacholine required to increase airway resistance by 100% (PD100) was 58 cumulative inhalation units (CIU) following exposure to 0.00 ppm and was significantly reduced (p less than 0.01) to 37 CIU at 0.08, 31 CIU at 0.10, and 26 CIU at 0.12 ppm O3; reductions in PD100 are considered indicative of increases in nonspecific airway responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Pulmonary function, airway responsiveness, and respiratory symptoms in asthmatics following exercise in NO2.

Two experiments were conducted to determine respiratory responses of persons with asthma performing intermittent moderate exercise while exposed to low concentrations of NO2. In the first, preliminary experiment, 13 male subjects, aged 19-35, with mild asthma were exposed on separate days in a chamber (natural breathing, 20 degrees C, 40% RH) to 0.30 ppm NO2 and to a control or "clean air" exposure (0.0 ppm NO2). Exposure included three 10-min periods of moderate treadmill exercise (VE = 44.5 liter/min), each followed by symptom measurement and pulmonary function testing. The average decrease in FEV1 following the initial 10 min exercise in 0.30 ppm was 11% which was significantly greater (p less than 0.05) than that observed in clean air (7%). Differences in FVC and SRaw were not significantly different at this time. Slight cough and dry mouth and throat were apparent only after the first exercise in NO2. After the second and third exercises, decreases in FEV1 and FVC and increases in SRaw were significantly greater in 0.30 than in 0.0 ppm NO2. Individual subject responses were variable. These results suggested that some asthmatics who perform moderate exercise while exposed to 0.30 ppm NO2 may experience bronchoconstriction and reduction in spirometric performance. Because of these preliminary findings, a more comprehensive, concentration-response experiment was conducted. Twenty-one male volunteers with mild asthma were exposed for 75 min with natural breathing to 0.0, 0.15, 0.30, and 0.60 ppm NO2. Exposure included three 10-min periods of moderate treadmill exercise (VE = 43 liter/min), each exercise followed by symptoms measurement and pulmonary function testing. In addition, airway responsiveness was measured two hr after each exposure by methacholine bronchial challenge testing. In the control exposures (0.0 ppm NO2), the exercise alone caused substantial decrements in pulmonary function. These decrements (as measured by decreases in FEV1 and FVC, and increases in SRaw) were not increased relative to the control exposure after any exercise session in any concentration of NO2. Furthermore, there was no overall group-averaged indication of a concentration-related effect of the NO2 on pulmonary function. Likewise, symptoms reported after NO2 exposure were not significantly different from those reported in clean air. Group-averaged airway responsiveness after exercise in NO2 was also not different from responsiveness after exercise in clean air. For only two subjects was there any indication of a concentration-related increase in airway responsiveness due to exposure to NO2.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Ozone-induced inflammation in the lower airways of human subjects.

Although ozone (O3) has been shown to induce inflammation in the lungs of animals, very little is known about its inflammatory effects on humans. In this study, 11 healthy nonsmoking men, 18 to 35 yr of age (mean, 25.4 +/- 3.5), were exposed once to 0.4 ppm O3 and once to filtered air for 2 h with intermittent exercise. Eighteen hours later, bronchoalveolar lavage (BAL) was performed and the cells and fluid were analyzed for various indicators of inflammation. There was an 8.2-fold increase in the percentage of polymorphonuclear leukocytes (PMN) in the total cell population, and a small but significant decrease in the percentage of macrophages after exposure to O3. Immunoreactive neutrophil elastase often associated with inflammation and lung damage increased by 3.8-fold in the fluid while its activity increased 20.6-fold in the lavaged cells. A 2-fold increase in the levels of protein, albumin, and IgG suggested increased vascular permeability of the lung. Several biochemical markers that could act as chemotactic or regulatory factors in an inflammatory response were examined in the BAL fluid (BALF). The level of complement fragment C3 alpha was increased by 1.7-fold. The chemotactic leukotriene B4 was unchanged while prostaglandin E2 increased 2-fold. In contrast, three enzyme systems of phagocytes with potentially damaging effects on tissues and microbes, namely, NADPH-oxidase and the lysosomal enzymes acid phosphatase and beta-glucuronidase, were increased neither in the lavaged fluid nor cells. In addition, the amounts of fibrogenic-related molecules were assessed in BALF.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1979

Perception of effort during constant work to self-imposed exhaustion.

The purpose of this study was to describe the pattern of change in effort sense and the value of this pattern in predicting work end-point at relatively high work intensity (80% VO2 max). The patterns of change of various physiological functions were also observed. Two modes of work (walking and running) were compared to ascertain generalizability of results. 26 healthy male volunteers served as subjects. Time to exhaustion (ET) did not differ between walking and running. As work continued during both tasks, significant increases of VE, VE/VO2, VE/VCO2 and HR and a significant decrease of ETCO2 were observed; while VO2 and R remained fairly constant. VO2 and VE during the run were about 5% greater than during the walk; there were no differences in other measures. Ratings of perceived exertion (RPE) from the Borg Scale were identical for both conditions, increasing in a near linear fashion from a value of 12.9 at 25% of total work time to 18.9 at exhaustion. Ratings obtained at 25 and 50% ET were extrapolated to time of exhaustion; the point of intercept corresponded to ratings of perceived exertion for maximal work. At exhaustion, subjects rated perception of respiratory exertion for the walk as less than that for the run; perception of leg exertion was not different for the two conditions. Plasma lactate, epinephrine and norepinephrine concentrations following exercise did not differ between the two conditions. The findings for the walking experiment were essentially replicated in a second investigation involving another 28 subjects. It is concluded that, with the exception of VO2 and some ventilatory parameters, walking and running at the same relative work intensity resulted in comparable perceptual and physiological responses. Psychophysical judgments made early during work were reasonably accurate predictors of exhaustion time.

Adult↗
PubMed1979

The nature of the perception of effort at sea level and high altitude.

The purpose of this study was to compare perceptual responses (RPE) and selected physiological measures during both short term and prolonged exercise of equal relative intensities at 4300 m to those at sea level. Specifically, we compared results obtained (n=20) for 6 min of exercise at 60, 80 and 95% VO2max and at 5 min intervals during exercise to exhaustion at 85% VO2max. At 4300 m, VO2max was reduced 19%, while VEmax and Rmax increased 17 and 8%, respectively. HRmax and RPEmax was unchanged. For any given relative exercise intensity, VO2 and absolute exercise intensity (kpm-min-1) were reduced, while VE was about 12% and R about 7% greater at 4300 m; HR was unchanged. At 4300 m, RPE at the lower intensities of submaximal exercise and early during prolonged exercise were significantly less than at sea level. These differences were reduced and finally eliminated as exercise intensity increased toward maximal or as prolonged exercise continued to exhaustion. Endurance time to exhaustion at 4300 m was not different from that at sea level. To account for the perceptual differences between exercise at 4300 m an sea level, we proposed that local factors (muscular strain) exert greater influence on the perception of effort at exercise intensities which do not greatly stress ventilation and circulation, while central factors exert greater influence on the perception of effort at exercise intensities at which tachypnea and tachycardia are of sufficient magnitude to be perceived as extremely stressful.

Adult↗
PubMed1978

Psychometric correlates of pain perception.

There is disagreement in the literature as to whether responsivity to painful stimuli possesses psychometric correlates. A series of methodological and statistical factors are specified in this paper which could account for the equivocality of the literature. A series of experiments were performed in which (a) various methodological and statistical issues were first resolved and (b) psychometric correlates of pain perception were then identified by means of a stepwise multiple regression procedure. The criterion variable consisted of the psychophysical judgment of pain during a 2-min. exposure to a 3,000 gm. force on the periosteum of the left fore-finger's second digit. The predictor variables consisted of selected psychological states and traits measured by the State-Trait Anxiety Inventory, Somatic Perception Questionnaire, Depression Adjective Checklist, Profile of Mood States, Eysenck Personality Inventory, and the Embedded Figures Test. The test-retest reliability of the pain test ranged from .64 to .84 across trials separated by a 3-wk. period. In the first experiment significant multiple regressions ranging between .57 and .72 were observed and psychological traits (field dependence, extraversion and trait anxiety) accounted for the variance in these analyses. In the next experiment significant multiple Rs ranging from .62 to .68 were observed. This served as cross-validation for the first experiment. The major difference was that psychological states (depression and vigor) as well as traits entered the multiple regression equations for certain of the analyses. It was concluded that selected psychological states and traits are significantly correlated with the perception of pain.

Adult↗
PubMed1977

Hypoxia-induced metabolic and core temperature changes in the squirrel monkey.

To identify components of reduced core temperature (Tre) with exposure to hypoxia, oxygen uptake (VO2) and skin temperatures were measured in chair-restrained squirrel monkeys during conditions of 21% O2, 11% O2, and 11% O2 + 5% CO2. Exposure to 11% O2 resulted in a 20% decrease in VO2 and a 1.8 degrees C reduction of Tre with skin temperatures closely paralleling Tre. The addition of 5% CO2 to 11% O2 effectively blocked the decrease of both VO2 and Tre. The responses of one monkey (LD) exhibiting decreased Tre (greater than 2.0 degrees C) and 20% decrease in VO2 were compared to those of another (SD) exhibiting decreased Tre (less than 0.5 degrees C) and little change of VO2 under the same experimental conditions. Increased mean arterial blood pressure (BPa) and heart rate (HR) occurred for monkey SD, while for monkey LD BPa decreased and HR increased slightly. Arterial pressure of oxygen (PaO2) and calculated arterial saturation of oxygen (SaO2) were higher, while PaCO2 was lower for monkey SD than for monkey LD. When 5% CO2 was added to 11% O2 both animals exhibited decreased PaO2, little change of Tre, VO2, PaCO2, arterial pH, and calculated SaO2, and increased BPa and HR. These data suggest that decreased Tre resulted from reduced heat production and reduced oxygen transport was primarily responsible for reduction of heat production.

Animals↗
PubMed1977

Normal acid-base status of arterial blood from the conscious, chair-restrained squirrel monkey.

Normal acid-base status of arterial blood (pHa =7.40, PaCO2=38.1 Torr) was demonstrated for conscious, restrained squirrel monkeys when environmental stimuli were minimized and monkeys are habituated to experimental procedures. These results indicate the potential for using squirrel monkeys in experiments in which normal acid-base status is a significant factor.

Acid-Base Equilibrium↗
PubMed1976

Effects of altering O2 delivery on VO2 of isolated, working muscle.

Maximal oxygen consumption (VO2 max) and muscle blood flow (Q max) were measured in an isolated gracilis muscle preparation before and after alteration in perfusion pressure (BP), arterial oxygen saturation (SaO2), and hemoglobin concentration (Hb). Q varied directly with BP and inversely with Hb (viscosity) but was unaffected by changes in arterial SaO2. VO2 max varied directly with oxygen delivery under all conditions. These results indicate that VO2 max is normally limited by oxygen delivery rather than any intrinsic limiting of oxygen consumption of the muscle.

Animals↗
PubMed1976

Amelioration of the symptoms of acute mountain sickness by staging and acetazolamide.

Treatment by 4 d of residence at 1600 m plus the administration of 500 mg acetazolamide b.i.d. for the last 2 d at 1600 m and the first 2 d at 4300 m was compared with no treatment prior to ascent to 4300 m for prophylaxis of acute mountain sickness. The treatment successfully prevented almost all symptoms of acute mountain sickness. It had no effect on the diminished capacity for maximal or prolonged heavy physical work. The treatment produced a relative acidosis and a comparatively greater arterial oxygen tension at 4300 m.

Acclimatization↗
PubMedDate not supplied

Respiratory response of humans exposed to low levels of ozone for 6.6 hours.

Recent evidence suggests that prolonged exposures of exercising men to 0.08 ppm ozone (O3) result in significant decrements in lung function, induction of respiratory symptoms, and increases in nonspecific airway reactivity. The purpose of this study was to confirm or refute these findings by exposing 38 healthy young men to 0.08 ppm O3 for 6.6 h. During exposure, subjects performed exercise for a total of 5 h, which required a minute ventilation of 40 l/min. Significant O3-induced decrements were observed for forced vital capacity (FVC, -0.25 l), forced expiratory volume in 1 s (FEV1.0, -0.35 l), and mean expiratory flow rate between 25% and 75% of FVC (FEF25-75, -0.57 l/s), and significant increases were observed in airway reactivity (35%), specific airway resistance (0.77 cm H2O/s), and respiratory symptoms. These results essentially confirm previous findings. A large range in individual responses was noted (e.g., percentage change in FEV1.0; 4% increase to 38% decrease). Responses also appeared to be nonlinear in time under these experimental conditions.

Adolescent↗