Breathing Resistance Research Articles

Directed exploration is reduced by an aversive interoceptive state induction in healthy individuals but not in those with affective disorders.

Elevated anxiety and uncertainty avoidance are known to exacerbate maladaptive choice in individuals with affective disorders. However, the differential roles of state vs. trait anxiety remain unclear, and underlying computational mechanisms have not been thoroughly characterized. In the present study, we investigated how a somatic (interoceptive) state anxiety induction influences learning and decision-making under uncertainty in individuals with clinically significant levels of trait anxiety. A sample of 58 healthy comparisons (HCs) and 61 individuals with affective disorders displaying elevated anxiety symptoms (iADs; i.e., anxiety and/or depression) completed a previously validated explore-exploit decision task, with and without an added breathing resistance manipulation designed to induce state anxiety. Computational modeling revealed a significant group-by-condition interaction, such that information-seeking (i.e., directed exploration) in HCs was reduced by the anxiety induction (Cohen's d =.47, p =.013), while no change was observed in iADs. The iADs also showed slower learning rates than HCs across conditions (Cohen's d =.52, p =.003), suggesting more persistent uncertainty. These findings highlight a complex interplay between trait anxiety and state anxiety. Specifically, state anxiety may attenuate reflection on uncertainty in healthy individuals, while familiarity with anxious states in those with high trait anxiety may create an insensitivity to this effect.

Development of CPAP Overlay Interfaces for Efficient Administration of Aerosol Surfactant Therapy to Preterm Infants

The administration of surfactant aerosol therapy to preterm infants receiving continuous positive airway pressure (CPAP) respiratory support is highly challenging due to small flow passages, relatively high ventilation flow rates, rapid breathing and small inhalation volumes. To overcome these challenges, the objective of this study was to implement a validated computational fluid dynamics (CFD) model and develop an overlay nasal prong interface design for use with CPAP respiratory support that enables high efficiency powder aerosol delivery to the lungs of preterm infants when needed (i.e., on-demand) and can remain in place without increasing the work of breathing compared with a baseline CPAP interface. Realistic in vitro experiments were first conducted to generate baseline validation data, and then the CFD model, once validated, was used to explore key design parameters across a range of preterm infant nose-throat geometries and aerosol delivery conditions. The most important factors for efficient aerosol delivery were shown to be (i) maintaining the aerosol delivery flow rate below the tracheal flow rate (to minimize CPAP line loss) and (ii) concentrating the aerosol within the first portion of the inhalation waveform. An optimized design was shown to deliver approximately 37–60% of the nominal dose through the system and to the lungs with low intersubject variability (1050–2200 g infants) across two modes of device actuation (automated and manual) with room for further improvement. Ergonomic curvatures and streamlining of the prong geometries were also found to reduce work of breathing and flow resistance compared with a commercial alternative.Graphical

Influence of Humidity on FFP Masks with Electret Filter Media Under Real-Life Wearing Conditions

Most FFP (Filtering Face Piece) masks are made from nonwoven filter media that are electrostatically charged, resulting in the additional electrostatic capture mechanism of particles. The protective effect of these masks is therefore mainly dependent on the electric field surrounding the charged fibers. Upon prolonged wear, the mask becomes saturated with exhaled air, resulting in humidification on the wearer’s side. However, speaking, coughing, or sneezing also generate droplets, which can deposit on the mask from the person wearing it, as well as from other people. In order to investigate this influence on the filtration efficiency and the existing electric field, an experimental study was carried out. To imitate human breathing, a test setup was constructed using a Sheffield Head with different types of masks. This was followed by the cyclical humidification and drying of the masks through simulated breathing. By observing these phases in detail using sample sections, it was possible to continuously record the water content in the samples, the relative humidity, and the pressure drop (breathing resistance). The results demonstrate that moisture has an impact on the filtration efficiency of the electret FFP masks when worn under real-life conditions and that the initial condition can be restored with sufficient drying time.

Sterilization and Filter Performance of Nano- and Microfibrous Facemask Filters - Electrospinning and Restoration of Charges for Competitive Sustainable Alternatives.

Facemask materials have been under constant development to optimize filtration performance, wear comfort, and general resilience to chemical and mechanical stress. While single-use polypropylene meltblown membranes are the established go-to material for high-performing mask filters, they are neither sustainable nor particularly resistant to sterilization methods. Herein an in-depth analysis is provided of the sterilization efficiency, filtration efficiency, and breathing resistance of selected aerosol filters commonly implemented in facemasks, with a particular focus on the benefits of nanofibrous filters. After establishing a general overview over face mask filters and machine washing parameters required for successful decontamination, respective changes in filter performance and structure are presented. Sustainably manufactured, highly efficient, but also more fragile electrospun membranes not only offer competitive performance as well as a more environment-friendly production and degradation process, but also support a subsequent sterilization and recharging approach via alcohol exposition and drying in an electric field. It is further elaborated on the prospective sustainability of each material to offer a clear outlook on electrospun membranes as the most promising filter membranes of the future.

Detection and perception of inspiratory resistive loads in older adults with and without chronic obstructive pulmonary disease.

Impairments in the detection and perception of resistive loads in healthy ageing and chronic obstruction pulmonary disease (COPD) have implications for airway protection and breathlessness. This study investigated load detection and perception in 18 participants with COPD, 17 older adults (i.e. age-matched controls; AMC) and 23 young adults (i.e. young controls; YC). Load detection was assessed as the minimal change in airway resistance that could be detected, and load perception as the perceived level of effort to breathe through a series of supra-threshold resistive loads, rated on a modified Borg scale. Young and older adults, with and without COPD, could detect similar changes in resistance (∼0.7 cmH2O/l/s) and inspiratory pressure (∼0.5 cmH2O), although this equated to a smaller proportion of predicted maximal inspiratory pressure (MIPpred) for young adults (∼0.5 %MIPpred) compared to older adults with and without COPD (∼1.0 %MIPpred; p<0.001). For load perception, the relationship between Borg ratings and resistance was steeper in older adult controls compared to both young adults (p<0.001) and older adults with COPD (p<0.01). Borg rating slopes were comparable across all participant groups with changes in inspiratory pressure. There was no correlation between load detection threshold and load perception. In older adults, heightened perception of loaded breaths with large changes in breathing resistance may be due to an increased effort to breathe at these loads.

Review on need for designing sustainable and biodegradable face masks: Opportunities for nanofibrous cellulosic filters.

The surge in microbial illnesses, notably seen during the COVID-19 pandemic, has led to the global use of face masks-cloth, surgical, medical, and respirator types-to curb respiratory pathogen spread. Widely used by the public, patients, and healthcare workers, masks play a key role in reducing airborne transmission. However, synthetic, non-biodegradable materials in these masks have sparked environmental concerns due to disposal issues. Moreover, challenges like limited microbial filtration, poor fit, breathing resistance, and low reusability raise further issues, as does the failure to neutralize trapped microbes. Addressing these issues calls for high-performance, biodegradable masks crafted from renewable nanofibrous materials using advanced technology. Antimicrobial nanomaterial coatings can further reduce contamination risks for users and the environment. Nanofibrous materials, with their high surface area, enhance filtration, allow customization, and improve capture efficiency. Research is progressing on sustainable, biodegradable filters, particularly with cellulose materials. This review outlines mask types and limitations, spotlighting nanofibrous filters for their filtration efficiency, breathability, and sustainability. It also delves into nanofiber manufacturing and assesses bacterial cellulose-a promising renewable nanofibrous material suited for air filtration.

Assessment of Physical and Mechanical Parameters of Spun-Bond Nonwoven Fabric.

The selection of an appropriate fabric for technical applications, such as protective masks, hinges on a thorough understanding of the fabric's physical and mechanical properties. This study addresses the challenge of selecting the optimal material structure for the upper layer of a protective mask, aiming to ensure adequate breathability while providing effective filtration against airborne particles and contaminants. We assessed and compared the physical-mechanical properties of five polymer spun-bond nonwoven fabrics from different suppliers. Our comprehensive evaluation included, as follows: a visual inspection; light permeability analysis; mass and thickness measurements; elongation and tensile strength tests; breathing resistance assessments; and filter penetration tests with paraffin oil. The results revealed significant variations in performance among the samples, with one fabric consistently outperforming the others across multiple parameters. Notably, this top-performing fabric met or exceeded the EN 149:2001+A1:2009 standard for breathing resistance and filtration efficiency and, in combination with additional filter layers, met the requirements or exceeded class FFP2 (filtering face piece). This study underscores the importance of meticulous material selection and quality control in optimizing PPE (personal protective equipment) performance and user safety, providing valuable insights for mask manufacturers and healthcare professionals.

Research of the influence of filter element resistance on the powered air-purifying respirator service life

The purpose of the research was to determine the influence of the increasing resistance of filter elements on the service life of powered air-purifying respirators during operation in mining conditions and to substantiate the parameters of the respirator power source. The research was conducted by the computer-based simulation methods for the powered air-purifying respirator operation, which allows estimating the additional resistance of the filter caused by dust accumulation. The simulation model of the powered air-purifying respirator was developed on the basis of its physical model and, taking into account the empirical dependence of the change in the filter element resistance during dust deposition, allows determining the flow of air through the filter and the dust aerosol concentration in the working area air. The following parameters of the simulation model of a powered air-purifying respirator were substantiated: controlling action – fan rotating speed, restrictions on air flow and air pressure in the respirator mask (depending on the mode of working arrangements of the user), concentration of dust in the air of the working area, capacity of the power source, power consumption of the electric motor of the fan and control system components, parameters of filter elements (fibre packing density, filter layer thickness, fibre diameter, etc.), input concentration of dust aerosol, which made it possible to establish the relationship between the value of the filter element resistance and the time to complete discharge of the power source. A critical value of the resistance of the filter elements of the powered air-purifying respirator was established, which results in a significant discharge of the power source, based on the different flow rate of the air supplied to the undermask space at a given dust concentration in the working area. Relationship between the change in breathing resistance of the filters and the discharge of the power source was established, which allows determining the period of safe operation of the powered air-purifying respirator, based on the concentration of dust in the working area air and the user’s working arrangement. The practical value involves determining the lifespan of the powered air-purifying respirator, based on the critical value of the filter resistance, which results in the rapid discharge of the power source

Sleep problems of children with Down syndrome in northern China.

Limited research has looked at the present-day sleep problems among Chinese children with Down syndrome (DS). This study aimed to investigate the situation of the sleep problems of school-aged children with DS in northern China. Parents of children with DS were a convenience sample recruited through the special education schools of Shandong Province in China. The Chinese version of the Children's Sleep Habits Questionnaire was applied to assess the sleep problems of children with DS. Parents of 334 children with DS reported the average sleep duration was 9.7 (9.3-10.2) hours per night, and 62.0% of children with DS were reported sleeping less than 10h per night. Additionally, the total prevalence rate of sleep problems among children with DS was 69.8%. Sleep-disordered breathing (59.2%), sleep duration (33.8%) and bedtime resistance (32.0%) were the three most commonly reported sleeping problems. Younger children with DS (age 6-8years) had severe problems with bedtime resistance, sleep anxiety and parasomnias than older children with DS (age 9-12years) (all P<0.05). Sleep problems are prominent among children with DS in northern China and are worthy of attention. Caregivers and health professionals should raise awareness of sleep problems in this group of children and implement targeted interventions to improve their sleep quality as early as possible.

A retrospective characterization of pediatric facemasks marketed in the United States and implications for future designs

Background Device manufacturers who seek to market their pediatric facemasks in the United States (U.S.), as part of anthropometric data requirement, need to demonstrate their mask designs are expected to fit the intended user population. However, currently there are no well accepted test methodologies for pediatric facemasks. In addition, unlike N95 respirators, the expected maximum flow rate, and the pressure drop at that expected maximum flow rate for pediatric facemasks have not been established. Method The objective of this article is three-fold; use a literature survey to determine the worst-case flow rate, and an acceptable breathing resistance; and come up with a bench-test based protocol for assessing fit of pediatric facemasks. Results &amp; discussion The worst-case breathing flow rate for mask testing in the pediatric population is 45–60 Liters/minute (LPM), and the acceptable pressure drop at the worst-case flow rate is 2.0 mmH2O. A retrospective assessment of all the four brands of legally marketed facemasks in the U.S. that could be purchased, revealed that majority of the brands have high filtration efficiency (&gt;95%) at low flow rate 5 LPM which reduces to ~ 80% at 45 LPM. At 5 LPM, the pressure drop ranges from 0.3–0.6 mmH2O, remaining below the 2.0 mmH2O. However, at higher flow rates, (representing strenuous activities, or older children (&gt; 12 years)), most masks exhibited a pressure drop within the range of 2.9 to 6.0 mmH2O. Furthermore, opening the pleats of the facemasks completely results in a notable reduction in pressure drop (a 6.6-fold decrease, p = 0.03). To assess fit of these same brands of facemasks, we then updated our previous validated adult manikin fit-test method and used it in manikins in the age group of 2 to 14 years. Either poor nose-clip adherence to the manikin, low filtration efficiency of the pediatric facemasks, or off-label use (i.e. when donned on manikins representing 2 years to 14 years) contributed to low fit. Conclusions A new bench-top tool to evaluate quantitative fit of pediatric facemasks was developed. In addition, based on the research reported here, we provide practical implications for the members of the community: users, academia and medical device manufacturers.

FFP2 induced breathing resistance does not affect metabolism and well-being during brisk walking and stair climbing - a randomized controlled trial

ObjectivesN95 or Type II filtering face pieces (FFP2) are often worn during work hours or on public transportation to prevent airborne infection. The aim of this randomized controlled crossover study is to assess the impact of FFP2 induced breathing resistance on pulmonary function, blood gas values and discomfort during walking and stair climbing.MethodsN = 16 healthy adults (24.8 ± 2.2 years; 10 females, ) participated. Interventions included (1) six minutes of walking in a 16-meter-long hallway (612 m) and (2) eight minutes of stair climbing in a two-story staircase (420 stairs), both with and without a FFP2 (> 48 h wash-out). Spiroergometric data (Ventilation, breathing frequency, tidal volume, oxygen uptake and carbon dioxide exhalation (primary outcome), end tidal carbon dioxide- and oxygen pressure) and self-reported response (Perceived exertion, dyspnoea and pain) were assessed during activities. Blood gas analysis (capillary carbon dioxide- (pCO2) (primary outcome) and oxygen partial pressure (pO2), pH, lactate and base excess) was measured immediately after cessation of activities. Manipulation effects (FFP2 versus no mask) were tested using repeated measures analyses of variance.ResultsAnalysis showed no effect of FFP2 on pCO2 or other blood-gas parameters but on carbon dioxide exhalation during walking: (mean 1067, SD 209 ml/min) (mean 1908, SD 426 ml/min) (F(15) = 19.5; p < 0.001; ηp2 = 0.566) compared to no mask wearing (mean 1237, SD 173 ml/min; mean 1908, SD 426 ml/min). Ventilation was decreased and dyspnoea was increased by FFP2 during activities. FFP2 led to lower oxygen uptake and lower end tidal oxygen but higher end tidal carbon dioxide during stair climbing.ConclusionsFFP2 decreased ventilation based on slower breathing patterns and led to limitations in pulmonary gas exchange and increased subjective dyspnoea. However, invasive diagnostics revealed no signs of clinically relevant metabolic effects immediately after everyday physical activities.

Computational Mechanisms Underlying Multi-Step Planning Deficits in Methamphetamine Use Disorder.

Current theories suggest individuals with methamphetamine use disorder (iMUDs) have difficulty considering long-term outcomes in decision-making, which could contribute to risk of relapse. Aversive interoceptive states (e.g., stress, withdrawal) are also known to increase this risk. The present study analyzed computational mechanisms of planning in iMUDs, and examined the potential impact of an aversive interoceptive state induction. A group of 40 iMUDs and 49 healthy participants completed two runs of a multi-step planning task, with and without an anxiogenic breathing resistance manipulation. Computational modeling revealed that iMUDs had selective difficulty identifying the best overall plan when this required enduring negative short-term outcomes - a mechanism referred to as aversive pruning. Increases in reported craving before and after the induction also predicted greater aversive pruning in iMUDs. These results highlight a novel mechanism that could promote poor choice in recovering iMUDs and create vulnerability to relapse.

Fiber-in-Tube Electrifiable Structure for Virus Filtration Self-Generated Static Electricity by Vibration/Sound.

Fiber has been considered as an ideal material for virus insulation due to the readily available electrostatic adsorption. However, restricted by the electrostatic attenuation and filtration performance decline, their long-lasting applications are unable to satisfy the requirements of medical protective equipment for major medical and health emergencies such as global epidemics, which results in both a waste of resources and environmental pollution. We overcame these issues by constructing a fiber-in-tube structure, achieving the robust reusability of fibrous membranes. Core fibers within the hollow could form generators with tube walls of shell fibers to provide persistent, renewable static electricity via piezoelectricity and triboelectricity. The PM0.3 insulation efficiency achieved 98% even after 72 h of humidity and heat aging, through beating and acoustic waves, which is greatly improved compared with that of traditional nonwoven fabric (∼10% insulation). A mask spun with our fiber also has a low breathing resistance (differential pressure <24.4 Pa/cm2). We offer an approach to enrich multifunctional fiber for developing electrifiable filters, which make the fiber-in-tube filtration membrane able to durably maintain a higher level of protective performance to reduce the replacement and provide a new train of thought for the preparation of other high-performance protective products.

Asymmetric aerosol volume transmission: A computational approach toward infection prevention efficiency of face masks

Wearing face masks is considered as one of the infection prevention and control options for respiratory viruses (e.g., SARS-CoV-2) that acts by blocking virus-laden aerosols. It is generally thought that aerosol blockage occurs when air passes through the face mask fabric. We calculated air flows through face masks and through peripheral leakages, based on reported breathing resistance values of face masks (FFP/N95, surgical masks, and cloth masks) and found that most of the inhaled and exhaled air passes through these peripheral leakages. Nevertheless, face masks remain effective as an infection prevention option, because additional calculations showed that the majority of aerosol volume cannot follow the tortuous path of air around the face mask. The filtering efficiency through the peripheral leakages can be described as a function of breathing conditions, vocal activities, the leakage geometry and tortuous pathway, aerosol properties (diameter, composition) and ambient conditions (e.g., evaporation, ventilation). Inclusion of these parameters explains the asymmetric filtering behavior of face masks, i.e., the risk of infection from person A to person B does not necessarily equal the risk of infection from person B to person A. Our findings explain thus why masking an infectious person is more effective than masking an exposed person. Establishing that the tortuous pathway of air around the face mask is the sole contributor to face mask efficiency opens new opportunities for designing safer face masks.

Incorporating uncertainty within dynamic interoceptive learning.

Interoception, the perception of the internal state of the body, has been shown to be closely linked to emotions and mental health. Of particular interest are interoceptive learning processes that capture associations between environmental cues and body signals as a basis for making homeostatically relevant predictions about the future. One method of measuring respiratory interoceptive learning that has shown promising results is the Breathing Learning Task (BLT). While the original BLT required binary predictions regarding the presence or absence of an upcoming inspiratory resistance, here we extended this paradigm to capture continuous measures of prediction (un)certainty. Sixteen healthy participants completed the continuous version of the BLT, where they were asked to predict the likelihood of breathing resistances on a continuous scale from 0.0 to 10.0. In order to explain participants' responses, a Rescorla-Wagner model of associative learning was combined with suitable observation models for continuous or binary predictions, respectively. For validation, we compared both models against corresponding null models and examined the correlation between observed and modeled predictions. The model was additionally extended to test whether learning rates differed according to stimuli valence. Finally, summary measures of prediction certainty as well as model estimates for learning rates were considered against interoceptive and mental health questionnaire measures. Our results demonstrated that the continuous model fits closely captured participant behavior using empirical data, and the binarised predictions showed excellent replicability compared to previously collected data. However, the model extension indicated that there were no significant differences between learning rates for negative (i.e. breathing resistance) and positive (i.e. no breathing resistance) stimuli. Finally, significant correlations were found between fatigue severity and both prediction certainty and learning rate, as well as between anxiety sensitivity and prediction certainty. These results demonstrate the utility of gathering enriched continuous prediction data in interoceptive learning tasks, and suggest that the updated BLT is a promising paradigm for future investigations into interoceptive learning and potential links to mental health.

Improving Breath Detection From Pulsed-Flow Oxygen Sources Using a New Nasal Interface.

Patients with COPD and other lung diseases are treated with long-term oxygen therapy (LTOT). Portable oxygen sources are required to administer LTOT while maintaining patient autonomy. Existing portable oxygen equipment has limitations that can hinder patient mobility. A novel nasal interface is presented in this study, aiming to enhance breath detection and triggering efficiency of portable pulsed-flow oxygen devices, thereby improving patient mobility and independence. To examine the effectiveness of the new interface, 8 respiratory therapists participated in trials using different oxygen sources (tank with oxygen-conserving device, SimplyGo Mini portable oxygen concentrator [POC], and OxyGo NEXT POC) and breathing types (nasal and oral) while using either the new nasal interface or a standard cannula. Each trial was video recorded so participant breaths could be retroactively matched with a pulse/no-pulse response, and triggering success rates were calculated by dividing the number of oxygen pulses by the number of breaths in each trial. After each trial, volunteers were asked to rate their perceived breathing resistance. Nasal breathing consistently resulted in higher triggering success rates compared to oral breathing for pulsed-flow oxygen devices. POCs exhibited higher triggering success rates than did the oxygen tanks with conserving device. However, there were no significant differences in triggering success rates between the two POC models. The new nasal interface demonstrated improved triggering success rates compared to the standard cannula. Whereas the new nasal interface was associated with a slight increase in perceived breathing resistance during nasal breathing trials, participants reported manageable resistance levels when using the interface. This study demonstrates that the new nasal interface can improve triggering success rates of pulsed-flow oxygen devices during both nasal and oral breathing scenarios. Further research involving patient trials is recommended to understand the clinical implications of improved pulse triggering.

Investigating effects of FFP2 wearing during physical activity on gas exchange, metabolism and affective state using a randomized controlled trial

Concerns are repeatedly raised about possible adverse respiratory effects of wearing filtering face pieces (FFP) during physical activity. This study compared the impact of FFP type 2 (NF95) on pulmonary function, blood gas values, metabolism and discomfort during light, moderate and vigorous physical activity. Healthy adults (n = 13; 6 females, 7 males; mean 31.3, SD 5.5 years) participated in this randomized two-armed (Ergometer cycling with a FFP type 2 vs. no mask) crossover trial. Baseline cardiopulmonary exercise testing and two interventions (masked and unmasked ergometer cycling 40%, 50% and 70% VO2max, 10 min each) were separated by 48 h washout periods. Spiroergometric data (End tidal carbon dioxide partial pressure PetCO2; breathing frequency; inspiration time), blood gas analysis outcomes (capillary carbon dioxide partial pressure, pCO2) and subjective response (Breathing effort and perceived exertion) were contrasted between conditions using ANOVAs. All participants completed the crossover trial, seven started with the FFP2 condition (No adverse events or side effects). FFP2 decreased breathing frequency, prolonged inspiration time, increased perceived breathing effort and PetCO2 (p < .05). Blood pCO2 in millimetres mercury increased during exercise with 50%VO2max (mean 36.67, SD 3.19 vs. mean 38.46, SD 2.57; p < .05) and 70%VO2max (35.04, 2.84 vs. 38.17, 3.43; p < .05) but not during exercise with 40%VO2max (36.55, 2.73 vs. 38.70). Perceived exertion was not affected (p > 0.05) by mask wearing. Conclusion: Mask-induced breathing resistance decreased respiratory performance and limited pulmonary gas exchange. While FFP2 affected subjective breathing effort per se, invasive diagnostics showed that statistically significant metabolic effects are induced from moderate intensity upwards.Trial registration: DRKS-ID: DRKS00030181, Date of registration: 05/09/2022 (German Register for Clinical Trials).

The Efficiency of Respiratory Exercises in Rehabilitation of Low Back Pain: A Systematic Review and Meta-Analysis.

Low back pain (LBP) is a common musculoskeletal disorder, and respiratory exercise is considered a nonsurgical management method. Therefore, this systematic review and meta-analysis aims to estimate the results of randomized controlled trials on the effect of respiratory training in reducing LBP and its dose relationship. The present study was conducted from January 2020 to January 2022, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (2020). Relevant studies were searched in multiple databases including PubMed, Web of Science, the Cochrane Library, EBSCO, Scopus, ScienceDirect, Wan Fang and China Knowledge Network, ClinicalTrials.gov, and Google Scholar, using a combination of MeSH/Emtree terms and free-text words. The heterogeneity of the studies was assessed using the I2 statistic. A total of 14 publications were included in the meta-analysis, with a total sample size of 698 individuals, aged 60-80years. Respiratory exercise was effective in relieving LBP (standardized mean difference = -0.87, P < .00001) and improving physical disability (standardized mean difference = -0.79, P < .00001). The type of breathing and the total duration of breathing exercises were found to be the source of heterogeneity in this study by subgroup analysis. Subgroup analysis revealed that the most significant effect sizes of breathing resistance exercise to reduce LBP and the most significant effect sizes of breathing relaxation techniques to alleviate physical disability were performed 3 to 5 times per week and period >4weeks. Respiratory exercise reducing LBP and improving functional disability was most effective when the total duration of the intervention was >500minutes. Funnel plots showed that the results of the 2 overall studies were reliable without publication bias. Respiratory exercise can effectively reduce LBP and improve physical disability. Therefore, these exercises can be regarded as a part of a LBP management plan. We recommend an exercise program with 30 to 50 minutes, 3 to 5 times per week, and >4weeks of breathing resistance exercise program as the most effective for treating LBP.

Evaluation of the effect of nozzle diameter on the breathing performance of a diving breathing apparatus

Abstract The article was inspired by information in the literature regarding damage to medium-pressure diving hoses, which, as a result of the crystallisation of material on their inner surface and the detachment of particles, caused significant interference with the output of the pressure regulator. A dangerous consequent ‘clogging’ of the airflow in stage II of the breathing apparatus and an increase in the effort in the diver’s lungs to overcome the increased breathing resistance resulted. This problem was investigated in the paper. Nozzles with reduced diameters were fabricated to simulate the deterioration of the automaton conditions. A suitably selected regulator from a domestic manufacturer’s was used for the tests. A series of measurements was carried out in a breathing simulator for the established experimental conditions specified in the standard PN-EN 250:2014. Following the test, the results obtained were analysed and interpreted based on statistical description methods.

Effects of masks on physiological and thermal responses of college students during outdoor activities

In the post COVID-19 era, people have adjusted to coexistence with viruses and air pollution, and masks have become basic personal protective equipment. However, we know little about the physiological and thermal feedback when wearing masks and performing outdoor activities varying in intensity. We combined mask types (no mask, surgical, N95, and cloth) and activity intensities (light, moderate, and vigorous) to investigate personal physiological and thermal responses in outdoor environments. We had four principal findings: 1) perioral temperature (Talocal) was the highest under cloth masks and perioral relative humidity (RHlocal) was the highest under cloth or N95 masks during moderate and vigorous intensity activities; 2) “breathing resistance” scores were the highest at all stages when wearing masks; 3) wearing masks had a positive effect on the decrease of mean skin temperature (MST), and this effect was the greatest for surgical masks; and 4) during exercise, thermal sensation vote (TSV) was mainly influenced by Talocal and RHlocal in the dead space under masks. TSV was primarily affected by RHlocal and ΔAH under surgical and cloth masks, while TSV was primarily influenced by Tg under N95 masks. Our findings provide basic information supporting mask selections linked to activity intensity in outdoor settings.