Effects of breathing-gas pressure on pulmonary function and work capacity during immersion

Upright immersion induces respiratory mechanical changes that may impair pulmonary function during hyperbaric exercise. To evaluate this, 10 divers performed an incremental cycling protocol while immersed upright at 1.02 and 6.05 atmospheres absolute (atm abs). Air was supplied at each of two hydrostatic pressures: mouth pressure (Pm: to stimulate a mouth-held demand regulator) and lung centroid pressure (PLC). Subjects perceived air delivery at PLC to be more comfortable at each level of exercise at both absolute pressures (P less than 0.05). At 6.05 atm abs subjects perceived narcosis to be greater for Pm than for PLC air delivery. Hypoventilation was encountered at 6.05 atm abs with PLC air delivery and was further exacerbated when air was delivered at Pm (P less than 0.05). It was concluded that hypoventilation and narcosis are reduced whereas respiratory comfort is increased when air is delivered at PLC. This change is possibly due to improved pulmonary mechanics accompanying PLC air supply pressure.     

Physiologic responses to static, dynamic and combined work

The main objective of the present study was to determine the effects on cardiovascular stress of tasks that have varying degrees of static and dynamic components (weight holding, manual lifting and stepping). Heart rate, oxygen consumption and blood pressure were used as indices of cardiovascular stress. The results showed that oxygen consumption and heart rate responses to manual lifting are significantly lower than those of stepping and higher than those of weight holding. A low frequency lifting task evoked significantly lower systolic blood pressure than a high frequency lifting task. This study supported the idea that a physiologic fatigue criterion (PFC) based on stepping should not be applied directly to tasks such as manual lifting. In addition, a PFC for manual lifting should not be based only on oxygen consumption or heart rate; it also should incorporate systolic blood pressure as one of the monitored stress factors in setting lifting standards.     

Perceived exertion during simulated static work

The purpose of this study was to determine the effect of static work on the rating of perceived exertion (RPE). The subject were healthy, relatively fit young adults (16 men). Exercise was performed at 25% MVC both in a commonly-used work posture and in a non-typical working posture (overhead-work). Estimates of effort were recorded using the CR-20-Scale by Borg. A nonparametric analysis was carried out to examine the relationship between the level of static load and RPE. The results show that the level of static load is reflected in the RPE systematically. It is concluded that RPE measurements render possible comparative evaluation of strain by muscular static work demands.     

Pain perception during simulated static work

The purpose of this study was to determine the effect of current design recommendations (additional rest allowances) for static work on the development of temporary musculo-skeletal pains. The subjects were healthy, relatively fit young adults (16 men). Static work at 25% MVC was performed both in a commonly-used working posture and in a nontypical posture (overhead work). The ratios of work-to-rest corresponded to the ergonomical recommendations. Estimates of pain-perceptions concerning the neck, shoulders and back/trunk were recorded during the muscular exercise. The results show that under certain conditions (commonly-used working posture) the additional rest allowances render possible an exercise without musculoskeletal pains. During overhead work the development of temporary pain-perceptions is not inhibited by additional rest allowances. A revision of the current design recommendations for overhead work is suggested.     

A survey of static and dynamic work postures of operating room staff

Summary Work in health care units is associated with considerable physical strain and many musculoskeletal complaints. Most investigations have concentrated on the work of general hospital nurses; little is known about the physical stress load on other health care workers. We therefore carried out an ergonomic study amongst operating room staff in order to (i) determine the work (posture) stress load on this particular group of health care workers and the effect of static posture on this stress, (ii) identify activities involving poor work postures, and (iii) determine differences between specialities in regard to work posture stress load. The work postures and related work activities of four different groups of staff in operating rooms (surgeons, assistant anaesthesists, instrumentation nurses and circulating nurses) were recorded and evaluated using the specified Ovako Working posture Analysing System (OWAS). Observation during the course of 18 daily surgical programmes (total number of observations: 3714) in the specialities general surgery and ear-nose-throat (ENT) surgery revealed that the workload according to OWAS for circulating nurses and assistant anaesthesists was not harmful. Some work postures seen among instrumentation nurses and surgeons, however, need improvement. The work posture stress load in these groups is mainly due to the high prevalence of static work postures during the activities surgery (surgeons) and assisting surgery (instrumentation nurses). Significant differences in ergonomic stress load were observed between general surgeons and ENT surgeons. This survey in operating theatres relates work postures to basic activities and can be used as a starting point from which to improve work conditions in order to reduce or eliminate physical complaints among operating room staff.     

Performance when breathing through different respirator inhalation and exhalation resistances during hard work

Respirator inspiratory and expiratory breathing resistances impact ventilation and performance when studied independently. However, it is less clear as to how various combinations of inhalation and exhalation resistance affect user performance. The present study investigated the performance of 11 individuals during constant load, demanding work to exhaustion while wearing respirators with eight different combinations of inhalation and exhalation resistance. Exercise performance time, performance rating, minute volume, and peak inspiratory and expiratory airflow were recorded at the end of each test trial, and independent correlations with inhalation resistance and exhalation resistance were assessed. The combined impacts of respirator inhalation and exhalation resistances were quantified as the total external work of breathing (WOB(tot)) and correlations between the test variables and WOB(tot) were also examined. Significantly linear decreases in performance were found with increased inhalation resistances independent of exhalation resistance (R(2) = 0.99; p < 0.001) and with increased WOB(tot) (R(2) = 0.92; p < 0.001). Performance also decreased with increased exhalation resistance but no significant relationships were found. Minute volume decreased linearly with increased inhalation resistance independent of exhalation resistance (R(2) = 0.99; p < 0.001), but the linear decrease observed between minute volume and WOB(tot) was weak (R(2) = 0.36; p < 0.05). These findings suggest that WOB(tot) serves as a reliable estimate of the combined impacts of respirator inhalation and exhalation resistances on user performance during hard work, but that inhalation resistance alone serves as a better predictor of ventilation during respirator wear.     

Measurement of arterial blood pressure during anaesthesia.

Regular measurement and recording of blood pressure, with pulse monitoring and ECG, are the 'minimal monitoring' without which no anaesthetic should take place. This is because blood pressure is an index of some of the most fundamental physiological processes.     

Inspiratory flow rates during hard work when breathing through different respirator inhalation and exhalation resistances

There has been a long-standing debate regarding the adequacy of airflow rates used in respirator certification testing and whether these test flow rates underestimate actual values. This study investigated breath by breath inspiratory peak flow rate, minute ventilation, and instantaneous flow rates of eight young, healthy volunteers walking on a treadmill at 80-85% of maximal aerobic capacity until exhaustion while wearing an air-purifying respirator with one of eight combinations of inhalation and exhalation resistance. An analysis of variance was performed to identify differences among the eight conditions. Scheffe's post hoc analysis indicated which means differed. The group of conditions with the highest average value for each parameter was identified and considered to represent a worst-case scenario. Data was reported for these conditions. A Gaussian distribution was fit to the data and the 99.9% probability levels determined. The 99.9% probability level for the peak and instantaneous flow rates were 374 L/min and 336 L/min, respectively. The minute ventilation distribution was not Gaussian. Less than 1% of the recorded minute ventilations exceeded 135 L/min. Instantaneous flow rates exceeded the National Institute for Occupational Safety and Health's respirator test standards of 64, 85, and 100 L/min constant flow 91%, 87%, and 82% of the time, respectively. The recorded minute ventilations exceeded the 40 L/min minute ventilation test standard (for tests with a sinusoidal flow pattern) 100% of the time. This study showed that young, healthy respirator wearers generated peak flow rates, minute ventilations, and instantaneous flow rates that consistently exceeded current test standards. Their flow rates should be higher than those of a respirator wearer performing occupational work and could be considered upper limits. Testing respirators and respirator cartridges using a sinusoidal breathing pattern with a minute ventilation of 135 L/min (peak flow rate approximately 424 L/min) would encompass 99% of the recorded minute ventilations and 99.9% of the predicted peak and instantaneous flow rates from this study and would more accurately reflect human respiration during strenuous exercise.     

Measurement of helium elimination from man during decompression breathing air or oxygen.

Air breathing was compared with oxygen breathing during decompression from an 80-20% helium-oxygen dive to a depth equivalent to 120 fsw (4.6 ATA) in a dry chamber to see which was the most efficient gas for helium elimination. Helium elimination was measured in a closed circuit system for 90 min at the 40-fsw (2.2 ATA) stop. No significant difference was found in the efficiency of helium elimination breathing either air or oxygen in the five subjects tested.     

Effect of environmental stress on blood pressure during the work shift

OBJECTIVE: To evaluate blood pressure (BP) and heart rate (HR) behavior in individuals during the working journey in two environments with different work stressors. METHODS: The study comprised 46 male individuals working in a wood processing factory in Botucatu, Brazil. Twenty seven (27.4+/-5.4 yrs, mean+/-SD) worked in the production line performing intense physical activity (G1) at high room temperatures and noise levels. Nineteen (33.2+/-7.6 yrs old) performed managerial tasks mostly comfortably seated at low noise, air-conditioned offices (G2). After anthropometric measurements (obesity, total and local adiposity) and blood biochemistry analyses (glucose, triglycerides and cholesterol), their BP and HR were registered during three consecutive days at 3 different time of the day: in the beginning, in the middle and at the end of the working journey. RESULTS: There were similar BP and HR changes during the journey for G1 and G2, but G1 showed higher rates. Due to the wide variability of BP responses within each group, participants were divided in two subgroups: responders (GR1 and GR2) with BP increase >10%, and non-responders (GN1 and GN2). Both subgroups showed similar anthropometric and biochemical patterns differing only in their BP response and, in the case of GR1,family history for hypertension. GR1 showed higher BP and HR than GR2. CONCLUSIONS: Individual changes of BP and HR responses to environmental stressors during the working journey indicates that these factors should be considered while evaluating BP measurements and might be considered as potential factors for hypertension.     

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 worker's 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 worker's 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.     

Intermittent positive pressure breathing and the treatment of acute asthma

Whether or not intermittent positive pressure breathing (IPPB) is beneficial in the treatment of asthma has been controversial for 30 years. IPPB is expensive and has been associated with pulmonary infection, pneumomediastinum, pneumothorax, and death. The exact factors involved in the observed effectiveness of IPPB remain undetermined. With evidence from a literature review, it is concluded that in cases of severe asthma failing to respond to other methods of beta-agonist inhalation, there is sufficient evidence for the use of IPPB.     

Acute response to precision, time pressure and mental demand during simulated computer work

OBJECTIVES: The electromyographic (EMG) activity of shoulder and forearm muscles was recorded during a standardized computer task with different combinations of time pressure, precision demands, and mental demands to study the interaction of these factors and their effect on muscular response during simulated computer work. METHODS: The computer task lasted 5 minutes, and it was performed by 14 female computer-aided design (CAD) operators during 8 exposure combinations that differed with respect to time pressure, precision demand, and mental demand. Performance (number of produced drawings, mouse clicks, and errors) were recorded. The EMG activity was recorded from the trapezius, infraspinatus, deltoid, and extensor digitorum muscles. An electrogoniometer was used to measure wrist postures and movements. RESULTS: High time pressure (combined with low precision and low mental demands) resulted in higher EMG activity for all the muscles and in a small increase in the number of produced drawings. High precision demands caused a large reduction in the number of produced drawings, but not always a change in EMG activity. High precision demands and high mental demands led to no change or a reduction in muscle activity because the number of drawings was greatly reduced. CONCLUSIONS: The interaction between work pace and other exposure factors must be taken into account when the effects of changes in exposure demands on muscular response are predicted. Only then can it be predicted whether changing demands will constitute a risk of developing musculoskeletal disorders.     

Sex- and age-related differences in blood pressure response to local muscular work during noise

During noise exposure (90 dB [A]) and during local muscular work (30% MVC) combined with noise (90 db [A]) the blood pressure was measured in 20 men and 20 women (20-29 years; 30-39 years). In the group of younger subjects the blood pressure was taken also during the recovery period of 60 minutes. Age- and sex-related differences in blood pressure response were observed not only during noise exposure but also during combined exposure. The different return of the diastolic blood pressure to the resting value after the period of combined exposure referred to sex-related differences in the response of the cardiovascular system during the recovery period, too.