Peter B. Raven

Prediction of distress for individuals wearing industrial respirators.

The purpose of the investigation was to evaluate the effectiveness of trait anxiety in predicting respiratory distress resulting from heavy physical work performed while wearing an industrial respirator. Spielbergers trait anxiety scale was administered to 45 male volunteers in order to identify individuals with elevated trait anxiety. This testing was followed by a pulmonary function test, resting 12-lead electrocardiogram (ECG), and an exercise ECG. Individuals with cardiovascular and/or pulmonary impairment did not continue with subsequent tests. The subjects next completed three treadmill tasks varying in intensity from 35% to 80% of VO2max, and each trial lasted for 10 minutes. Twenty-five of these individuals performed the exercise tasks while wearing a self-contained breathing apparatus (SCBA) in the demand mode, whereas the remaining 20 subjects used a pressure-demand SCBA. The reason for terminating exercise was classified as respiratory or non-respiratory on the basis of self-report responses on a 7-point dyspnea scale, as well as general responses concerning muscular fatigue and respiration. It was predicted, based upon trait anxiety scores, that six individuals would have respiratory distress, and five (83%) of these predictions were correct. It was also predicted that 39 of the 45 subjects would not experience distress and 38 (97%) of these predictions were correct. It was concluded that objective measures of trait anxiety can be used to identify those individuals who are most likely to experience distress while wearing an industrial respirator and performing heavy physical exercise.

Effects of Pressure-Demand Respirator Wear on Physiological and Perceptual Variables during Progressive Exercise to Maximal Levels

Current regulations governing the certification of respiratory protective devices are based on data published in the early 1950s. The limited data base of this early work and documented increases in the average height of the population underscore the need for additional information concerning the parameters of certification. In the present study, a protocol using an inclined treadmill (0.5% grade every 12 sec) was used to test a heterogeneous population (n = 38). Through submaximal up to and including maximal exercise levels with and without respirator wear, maximal oxygen uptake (VO2max) was significantly greater (p less than 0.01) with the respirator (44.11 +/- 1.3 mL/kg.min) than without the respirator (42.18 +/- 1.4 mL/kg.min) while maximal ventilation volumes (VEmax) were not significantly different (with = 118.7 +/- 4 L/min; without 119.6 +/- 5 L/min). While peak inspired flows (PFI) with the respirator (268 +/- 7 L/min) were less than without the respirator (281 +/- 9 L/min), p greater than 0.05, the lower peak expired flow (PFE) with the respirator (289 +/- 12 L/min) than without the respirator (324 +/- 13 L/min), p less than 0.01, indicated a significant blunting effect of the respiratory flows by the expired resistance during exercise to maximal levels. Peak inspired pressures (PPi) with and without the respirator were not significantly different (p greater than 0.05). The negative values obtained within the facepiece of the respirator (-7.65 +/- 0.8 cmH2O), however, indicate that the positive pressure within the facepiece was lost, and respiratory protection may be compromised. Peak expired pressure with the respirator (13.05 +/- 0.7 cmH2O) was significantly greater than without the respirator (10.7 +/- 0.5 cmH2O) indicating that, despite a lower PFE, greater force was required to overcome the resistances of the respirator on expiration. The dyspnea index, an index of physiological effort; suggests that the subjects were working at a higher percentage of their respiratory reserve with the respirator (p less than 0.05) than without. Perceptually, subjects also felt that breathing with the respirator was more difficult (p less than 0.05). The maximum heart rate and the ratings of perceived exertion were not significantly different between the two tests at maximal exercise levels. Maximum oxygen uptake was considered reached when subjects attained a respiratory exchange ratio of at least 1.15, when a heart rate response at or greater than age-predicted maximum was achieved, when ratings of perceived exertion indicated exhaustion, and/or when the measure of VO2 had plateaued during the final minute of exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

Exercise and air pollution

Abstract Will the air quality in Los Angeles be a matter of concern for athletes participating in the 1984 Olympics? This question and corollaries of it are being asked with increasing frequency as the time of the Olympics nears. This review identifies the major pollutants that have been shown to produce physiological changes which can and may effect athletic performance. Ozone is the major contaminant of Los Angles air which in recent times has received major research interest. Specifically, ozone has been documented as a potent airway irritant capable of initiating its effects at concentrations as low as 0.30 ppm. Recent evidence indicates that, when integrated with the sustained high ventilation volumes of the elite athlete, ozones airway constrictive effect is manifest at concentrations of 0.20 ppm. The effect of ozone causes an increase in breathing rate and a decrease in tidal volume for a given workload along with substernal pain. At the current ambient levels it is unlikely that sulphur dioxide w...

Clinical Pulmonary Function Tests as Predictors of Work Performance during Respirator Wear

The Occupational Safety and Health Administration (OSHA) mandate requiring medical information for respirator users provides the physician with little or no guidance as to what objective criteria may be valuable in assessing the workers ability to use a respirator safely. Therefore, the purpose of this study is to use the results of clinical pulmonary function testing to predict performance time on maximal- and endurance-type exercise tests. Respirator mask wear reduced clinical pulmonary function measures from 7%-15% from mouthpiece controls. The resistances of the mask reduced forced vital capacity by an average of 11.6% (0.65 L); forced expiratory volume in 1 sec by 7.3% (0.33 L); and maximum voluntary ventilation in 15 sec by 7.4% (12.4 L/min). Stepwise linear regression analysis was used to determine the clinical pulmonary function measures that were the best predictors of work performance. The MVV.25 with the respirator was determined to be the best predictor of maximal exercise performance both with and without the respirator. The difference in peak inspired flow with and without the respirator was the best predictor of performance time with the respirator during the endurance walk to exhaustion. Recommendations are made to the physician for procedures for determining a workers pulmonary capacity and calculating the effect of the respirator in reducing that capacity. This information then will allow the physician to determine safe levels of ventilation for a particular work task.

The effect of cardiac autonomic blockade on ventricular response to changes in preload

Echocardiographic (E) assessment of left ventricular response to increases (I) and decreases (D) in preload of 9 volunteer male subjects (mean age 25 +/- 2.0 years) was made during both control (C) and cardiac blocked (B) conditions. Cardiac autonomic blockade was produced by intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg), while I was produced by 5 degrees head-down tilt (T) for 90 min and D by lower body negative pressure to -40 Torr. Increases in resting heart rate of 44% and diastolic blood pressure of 13% occurred after B, (P less than 0.05). During C, the alterations in preload produced mean changes in end-diastolic volume (EDV) ranging from 135 +/- 10 cm3 for I to 96 +/- 9.1 cm3 for D. Changes in stroke volume during condition C were significantly related to changes in EDV during preload alterations and conformed to a normal LV function curve and were described by SV = 0.6 EDV + 4.5 cm3 (r = 0.85; P less than 0.001). Similarly during B, SV = 0.43 EDV + 5.8 cm3 (r = 0.75; P less than 0.001). Comparison of the LV function curves produced during C and B showed that both slope of regression and r were significantly different (P less than 0.01). These data indicate that cardiac autonomic blockade produces a downward shift in the LV function curve indicating a depression in myocardial contractility. In addition, the data indicate that changes observed in LV function during wide variations in preload are independent of autonomic nervous system influences and are independent of the intrinsic heart rate.

Effects of Acute Alcohol Ingestion on the Left Ventricular Performance of Normal Subjects Before and After Incomplete Autonomic Blockade

The effects of acute alcohol ingestion on the left ventricular performance of nine normal subjects, mean age 25 years, were studied before and after incomplete autonomic blockade, produced by atropine, 0.04 mg/kg body weight, and propranolol, 0.2 mg/kg body weight. Left ventricular (LV) function curves (stroke volume vs. end-diastolic volume) were plotted from data generated before and after large variations in cardiac preload. Increase in preload was produced by five degrees of head-down tilt for 90 minutes; decrease in preload was produced by graduated lower body negative pressure to -40 mmHg. After incomplete autonomic blockade, the negative inotropic effects of acute alcohol ingestion were minimal but significant and manifest by the reduction in mean velocity of circumferential fiber shortening (p less than 0.05). Studies during wide variations in preload confirmed the importance of maintaining central blood volume after alcohol ingestion. Lower body negative pressure after both incomplete autonomic blockade and alcohol produced a further deterioration in mean velocity of circumferential fiber shortening (p less than 0.05).

A Guideline for cardiopulmonary conditioning in the middle-aged recreational athlete A physiologic base

The aging process predisposes man to a greater con cern for and sensitivity to his health and fitness. Regular exercise can improve and maintain an individuals gen eral health regardless of the fitness level at the onset of the exercise regimen. We have noted that age does not significantly reduce the benefits (trainability) at tained from exercise; however, it does appear that a prolonged sedentary lifestyle will diminish the fitness level that can be achieved. Cardiopulmonary fitness is primarily a function of the oxygen transport system and, therefore, is monitored by determining maximal aerobic capacity (VO2max). The VO2max is a highly reproducible parameter related to cardiac output and the arteriovenous oxygen differ ence. Exercise conditioning can improve the VO2max by augmenting both the cardiac output and the oxygen extraction within the capillaries. Resting stroke volume is increased by a conditioning effect and resting brady cardia is common. Changes in total peripheral resist ance (TPR) and blood pressure are not as readily demonstrable. To produce a conditioning effect and maintain fitness it is recommended that dynamic exer cise at intensities of 60 to 90% of the maximum heart rate reserve for at least 15 minutes should be per formed at least 3 days/week. The total work load (as a function of intensity and duration) appears to be the most important criterion for producing a conditioning effect. Proper testing and evaluation is necessary for a clinician in prescribing an exercise program that is safe and effective. With the middle-aged individual precau tions must be taken to discern any risks for a cardio vascular event or structural injury.

Effect of 60-minute head-down tilt on arterial baroreflex function in anesthetized dogs.

Arterial baroreflex control of heart rate was assessed in 6 anesthetized dogs with a bolus infusion of phenylephrine before and during cardiopulmonary receptor stimulation by 6 degrees head-down tilt (HDT) for 60 min. No difference in arterial baroreflex function was observed between the control and HDT conditions. It appears that the attenuation of baroreflex function that occurs during acute stimulation of cardiopulmonary baroreceptors disappears when cardiopulmonary baroreceptors reset after prolonged stimulation.