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Toxic and Asphyxiating Hazards in Confined Spaces
Published in Neil McManus, Safety and Health in Confined Spaces, 2018
The significance of breathing pattern on alveolar ventilation is illustrated in Table 3.7. This table illustrates the impact of various combinations of breathing depth and rate. Note that minute ventilation (tidal volume x frequency) remains constant in all cases at 6,000 mL/min. That is, the same volume of air is breathed per minute in each case.
The relationship between heart rate and oxygen uptake during non-steady state exercise
Published in Thomas Reilly, Julie Greeves, Advances in Sport, Leisure and Ergonomics, 2003
Twenty-eight healthy subjects (12 females and 16 males) volunteered to participate in the first experiment after they had given written informed consent. Their physical characteristics are summarized in table 1. All subjects were familiar with the equipment and procedures of the tests. Each subject performed a maximal test on an electrically driven brake cycle ergometer (Lode Instruments, Groningen, The Netherlands) to determine maximum oxygen uptake (V̇O2max) and maximum heart rate (HRmax). These maximal values were used to normalize the data. On a different day one of the two non-steady state tests, either an interval test on a cycle ergometer or a field test with various leg exercises, was performed. Both tests involved dynamic exercise with a large muscle mass. During all experiments, HR was monitored continuously using a short-range radio telemeter (Sport Tester PE4000, Polar Electro Inc., Kempele, Finland). During both the maximal test and the interval test, the FO2, minute ventilation (V̇E) and respiratory exchange ratio (RER) were measured continuously using an on-line V̇O2 and CO2 analyser (Oxycon Ox4, Mijnhardt, Bunnik, The Netherlands). Average values were calculated over 30-s periods. During the field test, 30-s samples of expired air were collected using portable Douglas bags (de Groot et al. 1983). Gas analysis took place using an electronic V̇O2 and CO2 analyser (Oxylyser UG55 Capnolyser UG64, Mijnhardt, Bunnik, The Netherlands). The subject operated the two-way valve system that connected the Douglas bags with the mouthpiece. The two-way valve system contains a stopwatch to record actual air collection time. Both the gas analysing systems were calibrated against known gas mixtures before each test. For each 30-s air collection period, a simultaneous mean HR was calculated.
Parameters of high-frequency jet ventilation using a mechanical lung model
Published in Journal of Medical Engineering & Technology, 2022
Evgeni Kukuev, Evgeny Belugin, Dafna Willner, Ohad Ronen
In the first set of experiments, the frequency of the high-frequency ventilation was tested from 120 to 180 breaths per minute, while the I:E ratio was set on 1:1.5. Volume and pressure were measured separately for lung compliances ranging from 20 to 80 ml/cmH2O (Table 1). The most prominent differences in volume were observed in the group of low compliance, and the smallest difference was in the group with high compliance (Figure 2). The overall trend observed was a reduction in minute ventilation (MV) alongside a rise in RR. Minute ventilation (MV) was calculated using the formula MV = Vt (tidal volume) x RR. Therefore, the reduced tidal volume alongside a rising frequency was possible because of considerable linear decline in tidal volumes. When compliance was set to 20 ml/cmH2O, the tidal volumes dropped from 0.081 ml when the RR was 120/min to 0.048 (almost 50%) when the RR was set to 180/min, with an accompanying reduction in the MV by almost 15%. At higher (close to the “normal”) lung compliances, the reduction in Vt was relatively modest (approximately 25%), with only a 10% reduction in the minute ventilation. Yet, even in this high-compliance group, the relationship between the RR and MV was almost inverse linear, with a negative effect of the RR on the MV.
Variability of the penetration of particles through facemasks
Published in Aerosol Science and Technology, 2022
Buddhi Pushpawela, Stavros Amanatidis, Yuanlong Huang, Richard C. Flagan
Different masks and respirators are designed and manufactured to meet different standards, e.g., the National Institute for Occupational Safety and Health (NIOSH) standards for N95 FFRs, ASTM standards for US medical masks (ASTM F2101-19), and for cloth masks (barrier face covering ASTM FF3502-21); similar standards are imposed by agencies in other countries around the world (Rengasamy, Eimer, and Shaffer 2009). Each of these standards specifies air flow rates at which masks are to be tested, based mainly on the minute ventilation and peak inspiratory flow rates data derived by Silverman et al. (1943). The minute ventilation rate is the total volume of air inhaled (or exhaled), typically measured over many breaths, divided by the total time over which those breaths were taken (not just the inhalation or exhalation time). Roughly half of that total time is required to inhale that volume, the subject is exhaling during most of the remaining time. Thus, the actual volumetric flow rate through the filter medium is at least double the minute ventilation rate, and peak flow rates are even higher.
The relation between physical and mental load, and the course of physiological functions and cognitive performance
Published in Theoretical Issues in Ergonomics Science, 2022
It seems that there are quantitative and qualitative differences in the two R parameters (and in R patterns in general) depending on whether they are provoked mentally (through cognitive processes, volitional effort, emotions) or physically (physical work, exercise; Ganong 2005; Švancara 2003; Wientjes 1993; de Waard 1996). At light to moderate physical loads, higher minute ventilation (MV) is primarily induced by increased tidal volume (VT), while respiratory rate (RR) increases considerably only with a heavy physical load. In contrast, with increasing cognitive load – generally with a slight amount of mental arousal – RR accelerates but VT is shallower (Davies, Haldane, and Priestley 1919; Filo 2014; Veltman and Gaillard 1998; Wientjes 1993; Wilson, Fullenkamp, and Davis 1994). MV, which is a product of RR and VT over the course of one minute, increases as well. Hence, with mental effort RR accelerates greater than VT decreases. In summary, VT and MV in general are usually distinctly higher with physical load than with cognitive load; however, there is only a minimum difference in RR with the two types of loads (Wientjes 1993).