Exhalation Of Air Research Articles

Design and signal processing of plastic optical fiber respiratory sensors based on smartphones

A respiratory signal sensing scheme based on plastic optical fiber and smartphone is proposed. Respiratory signals are achieved by detecting the changes in abdominal circumference caused by the inhalation and exhalation of air from the lungs during breathing. A flexible clamp is prepared based on the 3D printing technology and the changes in abdominal circumference are leading to the lateral distance variation between the end face of the two plastic optical fibers in the clamp. The experiment demonstrates the scheme’s capability to detect a broad range of stable respiratory frequencies and weak signals. Finally, an automatic multi-scale peak detection algorithm is utilized to achieve real-time display of transient respiratory rate, which enables the timely feedback of apnea and abnormal signals. The proposed respiratory sensing system provides an efficient, accurate, convenient and low-cost solution for human physiological signal monitoring.

First record of a snake call in South America: the unusual sound of an ornate snail-eater Dipsas catesbyi

ABSTRACT The auditory systems and sound dynamics in snakes are frequent objects of debate. The known frequency of sounds produced by snakes ranges from 0.2 to 9.5 kHz. Here we report the first record of a vocalization by the South American snake Dipsas catesbyi. The call was recorded oportunistically in June 2021 upon manipulation, and had a duration of 0.06 seconds, reaching 3036 Hz in its peak frequency with a modulated note, emitted through exhalation of air through the larynx. We hypothesize that structured vocal emissions such as this are a reaction to a predation attempt and may be a feature shared by other species of Dipsadidae and other snakes.

Comparing LES and URANS results with a reference DNS of the transitional airflow in a patient-specific larynx geometry during exhalation

Air exhalation in the laryngeal area produces a complex transitional flow. A detailed investigation of the resulting flow features is very interesting from a fundamental point of view and useful to support medical researchers regarding treatment options. In the current study, the highly complex, unsteady, transitional flow in a patient-specific geometry has been described by three different numerical approaches, (1) using the unsteady Reynolds-averaged Navier–Stokes (URANS) equations with the k−ω shear stress transport (SST) turbulence model, (2) by large-eddy simulation (LES) with the WALE subgrid-scale model, and finally (3) using direct numerical simulation (DNS) – without any model needed. These three approaches deliver different pictures of the resulting flow, obviously with noticeable differences in terms of accuracy, but also regarding the associated computational efforts. The present article is devoted to the detailed comparison of these three approaches, using the DNS results as a reference. It has been found that even though URANS is able to predict with a fair accuracy the large-scale features of velocity and pressure in an average sense, it fails to predict correctly most relevant turbulent features; large differences are found concerning fluctuations, power spectral density, or spectral entropy. On the other hand, LES is able to reproduce both small-scale and large-scale flow features in a good agreement compared to DNS; additionally, LES delivers an appropriate description of the evolution of spectral entropy and can thus be used to predict flow transition. Obviously, DNS delivers an even more detailed and accurate view of the flow properties, but this comes with a tremendous increase in computing effort. For this configuration, a high-quality LES appears as best compromise between accuracy and computational requirements and, therefore, best suitable for medical studies of transitional airflows. All data-sets are publicly available under Abdelsamie et al. [1].

Measuring Total Filtration Efficiency of Surgical and Community Face Masks: Impact of Mask Design Features

Surgical and community face masks are used worldwide to reduce the transmission of respiratory infections in indoor environments. Performance parameters for these loose-fitting devices are mainly focused on material filtering efficiency, while, differently from face respirators, there are no standards methods for measuring the fraction of air leaking at the face seal. This study quantifies the total filtration efficiency (TFE), a parameter based both on filter efficiency and air leakage, of 50 face mask models with the aim of understanding the role of several mask design features on TFE performance. An instrumented head form equipped with sensors for measuring volumetric airflow and differential pressure was used to simulate the air exhalation from the mouth of a person wearing a face mask. A Response Surface Method (RSM) was used to model the TFE experimental data. Results showed that TFE values ranged over a wide interval (from 5 % to 73 %), with better values at higher flowrates. A significant positive correlation was found between TFE and filter breathability. The presence of a nosepiece showed to increase the TFE on average from 4 % to 6 %, according to the flowrate. Significant improvements were associated only to nosepieces incorporating a metallic wire. The RSM model evidenced that the increase in the number of the filter layers, and the use of a meltblown layer, result in higher TFE only when a nosepiece is in place. Differently, the benefit of the nosepiece is less marked for masks made of highly breathable filters. To improve overall mask performance, the design of loose-fitting face masks should carefully compromise between breathability and filtration efficiency of the filter materials. The addition of a metallic nosepiece help improving the TFE by limiting the air leaking at the face seal.

Computational fluid dynamics-based disease transmission modeling of SARS-CoV-2 Intensive Care Unit

Covid-19 has become one of the most severe diseases causing acute respiratory problems and has killed millions of people worldwide. It was declared as the ongoing pandemic by the World Health Organization. It is an infectious virus which can be transmitted by sneezing, coughing and exhalation of air by any infected person. There are certain places having high chances of becoming contaminated like hospital rooms. In this context, we studied the transmission of Covid-19 particles in an ICU room. We have considered the combined effect of both of air-conditioning (AC) and ceiling fan in the room. The infected person can transmit the disease when under influence of fan and AC. The work highlights the flow of aerosol particles considering the combined effect as well as the individual effects of fan and AC. The results also emphasized that the aerosol particle flow have a promising application in sanitizing the room.

A RANS-VoF Numerical Model to Analyze the Output Power of An OWC-WEC Equipped with Wells and Impulse Turbines in A Hypothetical Sea-State

Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter (OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT®, which is based on RANS-VoF (Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end (geometry is similar to that of the Pico’s plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m (each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency (relation between the average output and incident wave powers) of 46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.

At “half mask” or “nose commando:” A note demonstrating nasal breaths can spread microorganisms when improperly wearing a mask during COVID-19

Many individuals are wearing face masks improperly at ‘half mask’ and potentially breathing out microbes that can contaminate the air as well as anything below the nose. This note provides the first report that bacteria and fungi breathed out during nasal air exhalation are able to be cultured after landing on blood agar plates. The CFU’s are higher after both 10 breaths and extremely significant for 20 breaths compared to the control plates exposed to the air. Implications of this finding are that going ‘nose commando’ may be able to continue the spread of respiratory diseases such as COVID-19. Minute bioaerosols carrying bacteria may be designated as microsnot.

Affordable, Compact and Infection-Free BiPAP Machine.

Critical cases of COVID-19 require respiratory support provided primarily by mechanical ventilators. But, as per the current trend, about 15% of the cases require hospitalization and less than 5% cases are critical. Due to the massive number of COVID-19 cases all over the world, the ventilator requirement is increasing, and these traditional ventilators are quite expensive and are occupied for the critical cases, thus available in limited numbers. In this regard, BiPAP (Bilevel Positive Airway Pressure) ventilation support can be used for the less critical cases where patients do not require intubation by specialized staff and also minimizing the risk of infection during the procedure. The current article aims to deliver a design of an inexpensive BiPAP with an infection-free exhaust. BiPAP is a mode of ventilation which maintains positive pressure for air intake, and a low or zero pressure is created for expiration. The BiPAP suggested in the current article uses an air blower connected to an Arduino via a speed controller, the level of pressure and breathing rate are programmed in the Arduino, thus, the blower functions in BiPAP mode. The 3D printed mask proposed here comprises of a unique design for the intake and exhalation of air; and comprises of two sizes to fit all adults while avoiding any leakage. The design suggested is further tweaked for emergency use to support up to four patients using a single BiPAP. The mass production of the same would cost approx. INR 6500 or 85 USD.

Effect of reciprocating and unidirectional airflow on primary conversion of a pentagonal Backward Bent Duct Buoy

An Oscillating Water Column (OWC) device can output energy through reciprocating or unidirectional airflow. The unidirectional airflow is helpful to utilize a simple and high-efficiency unidirectional air turbine. The pentagonal BBDB proposed by us based on OWC principle can be regarded as a floating Oscillating Body and its Power Take-Off (PTO) consists of a chamber, a water column, a turbine and a generator. The Capture Width Ratio (CWR) of the pentagonal BBDB model with the reciprocating and unidirectional airflow was studied in this paper. The wave flume test results indicate the mean CWR of the pentagonal BBDB model with reciprocating airflow can reach up to 121.91% and the mean CWR of the model with unidirectional airflow could reach 100.94% during the whole wave cycle in regular waves. For irregular waves, the mean CWR of the model with the unidirectional airflow is as high as 62.83% during the whole wave cycle. Hopefully, the combination of the pentagonal BBDB with the check valve to output power during the air exhalation and conventional high-efficiency unidirectional turbine will improve the total efficiency of the BBDB.

COPD and heart failure: differential diagnosis and comorbidity.

Heart failure (HF) and chronic obstructive pulmonary disease (COPD) represent the most important differential diagnoses of dyspnea in elderly people. Heart failure is the inability of the heart to pump sufficient amounts of blood through the cardiovascular system. Pump failure is caused by compromised contractility and/or filling of the ventricles leading to forward and backward failure and subsequently to dyspnea. In COPD, the destruction and remodeling processes of the bronchiolar architecture inhibit proper exhalation of air, thereby leading to exhaustion of the thoracic muscles, insufficient oxygen diffusion, and dyspnea. Despite these fundamental differences in the pathophysiology of both disorders, their clinical presentation may be very similar. This renders accurate and timely diagnosis and therapy, especially in patients with coexisting disease, difficult. This clinical review summarizes typical problems in the diagnosis of COPD, HF, and coincident disease, and describes strategies that help avoid misdiagnosis and ineffective treatment.

Uncertainty assessment of the breath methane concentration method to determine methane production of dairy cows

The breath methane concentration method uses the methane concentrations in the cow's breath during feed bin visits as a proxy for the methane production rate. The objective of this study was to assess the uncertainty of a breath methane concentration method in a feeder and its capability to measure and rank cows' methane production. A range of controlled methane fluxes from a so-called artificial reference cow were dosed in a feed bin, and its exhaled air was sampled by a tube inside the feeder and analyzed. The artificial reference cow simulates the lungs, respiratory tract, and rumen of a cow and releases a variable methane flux to generate a concentration pattern in the exhaled breath that closely resembles a real cow's pattern. The strength of the relation between the controlled methane release rates of the artificial reference cow and the measured methane concentrations was analyzed by linear regression, using the coefficient of determination (R2) and the residual standard error as performance indicators. The effect of error sources (source-sampling distance, air turbulence, and cow's head movement) on this relation was experimentally investigated, both under laboratory and barn conditions. From the laboratory to the dairy barn at the 30-cm sampling distance, the R2-value decreased from 0.97 to 0.37 and the residual standard error increased from 75 to 86 ppm as a result of barn air turbulence, the latter increasing to a theoretical 94 ppm if modeled variability due to cow's head movement was accounted for as well. In practice, the effect of these random errors can be compensated by sampling strategies including repeated measurements on each cow over time, thus increasing the distinctive power between cows. However, systematic errors that may disturb the relation between concentration and production rate, such as cow variation in air exhalation rate and air flow patterns around sampling locations that differ between barns, cannot be compensated by repeated measurements. As a result, the methane concentrations of breath air will vary between cows with the same methane production. We conclude that the capability of the breath concentration measurement method to adequately measure and rank methane production rates among cows is highly uncertain and requires further investigation into variation sources with a systematic nature.

Resistive breathing and respiratory muscle fatigue: a load of concern just expired!

Pulmonary ventilation is a cyclical process of inhalation and exhalation of air providing dynamic tidal exchange between alveolar gas-exchanging units of the lungs and the external environment. This article is protected by copyright. All rights reserved

From the Book & New Media Review Editor's Desk

From the Book & New Media Review Editor's Desk Jessica Shumake As a journalist for my college newspaper, I frequently found myself tasked to initiate conversations with people attending campus events. I recall an assignment to write a story about residence hall move-in day. As I stood in a busy corridor, a Pentax camera strap around my neck, I attempted to initiate conversations with housing staff, parents, and new students as they carried cardboard boxes, plastic grocery bags, and rolled aluminum dollies. Few people wanted to talk with a student reporter on move-in day, though nearly all accepted the offer of an extra pair of hands to carry a load of stuff. After twenty minutes spent hesitating, I worked up the courage to ask a senior residence life advisor a question. Without a hint of irony, I ask if he had any "profound" thoughts to share with Captain's Log readers regarding being an RA. He looked at me, blinked a few times, and said "profound" with a rising intonation and an abrupt exhalation of air. Had I asked him to tell me a story about a day he felt challenged as an RA, about his biggest pet peeve, or about his hall's bulletin board design, the conversation may have gone in a useful direction. Instead, he turned away. With this misstep, the conversation ended before it ever really began: "move along, aspiring journalist, there's nothing 'profound' here worth discussing and people have real work to do." Even as a green reporter, I understood that a good quote, from the right source, is the lifeblood of a story worth reading. If no one I spoke with had anything substantial to say, there was no story. What I struggled with most as a reporter assigned to write a story about move-in day was my own confidence in drawing out strangers' stories. In fact, I did not write the student move-in article assigned to me and instead covered a soccer game as a photographer. As I reflect on the "profoundest" article I never wrote, it is the ordinariness of the situation that I turn over in my mind over twenty years later. As I read the reviews assembled in this issue, I am inspired by the firmness of purpose I know to be required in putting one's words into the world. Christopher M. Brown's review of Kelly Ritter's Reframing the Subject offers significant insight into post-WWII Coronet instructional films as proto-MOOCs (massively open online courses). Brown's review explores how these films addressed increasing enrollment and college access demands placed on educators due to the GI Bill. For large numbers of students, these films replaced "meaningful teacher-student interaction with oneway regurgitation of tasks modeled on-screen." Educational access narratives that require literacy instruction to be packaged as a commodity, through mass-delivery [End Page 74] systems, according to Brown's reading of Ritter, are more likely to be impediments to "social and economic mobility" than the salve they profess to be. Sandra Shattuck deploys a rhetoric of slowness and explores how our sense of time changes in the face our culture's obsession with speed in her review of Berg and Seeber's The Slow Professor. Rachel Buck's review of Composition in the Age of Austerity likewise explores labor and knowledge-building practices in writing studies and the impact of an increasingly stark fiscal landscape on the literacy needs and goals of our local communities. In Madelyn Pawlowski's review of Grassroots Literacies, she examines sexual literacy, collective action, and the normative narrative arcs through which LGBT and queer subjects navigate a politics of invisibility and becoming in Turkey. Sally Benson's review of The Desire for Literacy explores the unarticulated values and assumptions that constitute what literacy means for adults who seek to further their literacy learning in domains outside of formal school contexts. Eric A. House's review of Freedom Writing is keenly attentive to the function spirituality, music, and singing played in grassroots literacy education and civil rights activism for black people at the Sea Island Citizenship School in South Carolina. All of these reviews, and...

Energy cost and optimisation in breath-hold diving

We present a new model for calculating locomotion costs in breath-hold divers. Starting from basic mechanics principles, we calculate the work that the diver must provide through propulsion to counterbalance the action of drag, the buoyant force and weight during immersion. Compared to those in previous studies, the model presented here accurately analyses breath-hold divers which alternate active swimming with prolonged glides during the dive (as is the case in mammals). The energy cost of the dive is strongly dependent on these prolonged gliding phases. Here we investigate the length and impacts on energy cost of these glides with respect to the diver characteristics, and compare them with those observed in different breath-hold diving species. Taking into account the basal metabolic rate and chemical energy to propulsion transformation efficiency, we calculate optimal swim velocity and the corresponding total energy cost (including metabolic rate) and compare them with observations. Energy cost is minimised when the diver passes through neutral buoyancy conditions during the dive. This generally implies the presence of prolonged gliding phases in both ascent and descent, where the buoyancy (varying with depth) is best used against the drag, reducing energy cost. This is in agreement with past results (Miller et al., 2012; Sato et al., 2013) where, when the buoyant force is considered constant during the dive, the energy cost was minimised for neutral buoyancy. In particular, our model confirms the good physical adaption of dolphins for diving, compared to other breath-hold diving species which are mostly positively buoyant (penguins for example). The presence of prolonged glides implies a non-trivial dependency of optimal speed on maximal depth of the dive. This extends previous findings (Sato et al., 2010; Watanabe et al., 2011) which found no dependency of optimal speed on dive depth for particular conditions. The energy cost of the dive can be further diminished by reducing the volume of gas-filled body parts in divers close to neutral buoyancy. This provides a possible additional explanation for the observed exhalation of air before diving in phocid seals to minimise dive energy cost. Until now the only explanation for this phenomenon has been a reduction in the risk of decompression sickness.

Widespread occurrence of ephemeral funnel hoarfrost and related air ventilation in coarse‐grained sediments of a relict rock glacier in the seckauer tauern range, austria

This paper examines the occurrence of ephemeral hoarfrost crystals at funnel openings (funnel hoarfrost) detected between large blocks at the surface of the presumably relict chöneben ock lacier. Field mapping on 25 November 2011 identified 51 individual funnel openings with notable hoarfrost crystals distributed over the entire rock glacier. Hoarfrost was no longer detectable a few days after the initial mapping campaign. At least in the period 20–25 November 2011 temperature conditions at the rock glacier surface were favourable for hoarfrost formation and preservation as indicated by different types of measurements. A period of 24–48 h of hoarfrost‐suitable weather conditions would have been sufficient to form the observed hoarfrost if crystal growth rates of 2–4 mm h−1 are assumed. The void systems with funnel hoarfrost seem to be rather localised and limited in horizontal (10s of metres) and vertical (some metres) extent. Presumably the observed funnel hoarfrost was caused by the so‐called chimney effect, although no larger reversible air circulation systems with warm air exhalation were identified. Continuous ground temperature data from several sites at the rock glacier surface (period November 2011–December 2012) showed that hoarfrost sites are cooler and thermally buffered compared with non‐hoarfrost sites at similar elevations. This seems to be related to the decoupling of the air above the rock glacier and the pore air during periods of atmospheric warming. Only the combination of specific micro‐climatic (temperature/humidity), geometric (open void systems) and sedimentological (grain size/sediment structure) conditions allow the formation of the ephemeral funnel hoarfrost at this rock glacier.

Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy.

The anatomy and volume of the penguin respiratory system contribute significantly to pulmonary baroprotection, the body O2 store, buoyancy and hence the overall diving physiology of penguins. Therefore, three-dimensional reconstructions from computerized tomographic (CT) scans of live penguins were utilized to measure lung volumes, air sac volumes, tracheobronchial volumes and total body volumes at different inflation pressures in three species with different dive capacities [Adélie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and emperor (A. forsteri) penguins]. Lung volumes scaled to body mass according to published avian allometrics. Air sac volumes at 30 cm H2O (2.94 kPa) inflation pressure, the assumed maximum volume possible prior to deep dives, were two to three times allometric air sac predictions and also two to three times previously determined end-of-dive total air volumes. Although it is unknown whether penguins inhale to such high volumes prior to dives, these values were supported by (a) body density/buoyancy calculations, (b) prior air volume measurements in free-diving ducks and (c) previous suggestions that penguins may exhale air prior to the final portions of deep dives. Based upon air capillary volumes, parabronchial volumes and tracheobronchial volumes estimated from the measured lung/airway volumes and the only available morphometry study of a penguin lung, the presumed maximum air sac volumes resulted in air sac volume to air capillary/parabronchial/tracheobronchial volume ratios that were not large enough to prevent barotrauma to the non-collapsing, rigid air capillaries during the deepest dives of all three species, and during many routine dives of king and emperor penguins. We conclude that volume reduction of airways and lung air spaces, via compression, constriction or blood engorgement, must occur to provide pulmonary baroprotection at depth. It is also possible that relative air capillary and parabronchial volumes are smaller in these deeper-diving species than in the spheniscid penguin of the morphometry study. If penguins do inhale to this maximum air sac volume prior to their deepest dives, the magnitude and distribution of the body O2 store would change considerably. In emperor penguins, total body O2 would increase by 75%, and the respiratory fraction would increase from 33% to 61%. We emphasize that the maximum pre-dive respiratory air volume is still unknown in penguins. However, even lesser increases in air sac volume prior to a dive would still significantly increase the O2 store. More refined evaluations of the respiratory O2 store and baroprotective mechanisms in penguins await further investigation of species-specific lung morphometry, start-of-dive air volumes and body buoyancy, and the possibility of air exhalation during dives.

Dynamic Correlation between Whisking and Breathing Rhythms in Mice

Sniffing, a high-frequency, highly rhythmic inhalation and exhalation of air through the nose, plays an important role in rodent olfaction. Similarly, whisking, the active rhythmic movement of whiskers, plays an important role in rodent tactile sensation. Rodents whisk and sniff during exploratory behavior to sample odorants and surfaces. Whisking is thought to be coordinated with sniffing and normal respiratory behavior, but the precise temporal relationships between these movements are not known. Here, using direct measurements of whisking and respiratory movements, we examined the strength and temporal dynamics of the correlation between large-amplitude whisker movements and respiratory rhythm in mice. Whisking movements were detected using an optical sensor, and respiration was monitored with a thermistor placed close to the nostril. Our measurements revealed that breathing and whisking movements were significantly correlated only when the whisking rhythm was <5 Hz. Only a fraction (~13%) of all large-amplitude whisker movements occurred during episodes of high-frequency (>5 Hz) respiration typically associated with sniffing. Our results show that that the rhythms of respiratory and whisking movements are correlated only during low-frequency whisking and respiration. High-frequency whisking and sniffing behaviors are not correlated. We conclude that whisking and respiratory rhythms are generated by independent pattern-generating mechanisms.

Sniffing Behavior of Mice during Performance in Odor-Guided Tasks

Sniffing, a rhythmic inhalation and exhalation of air through the nose, is a behavior thought to play a critical role in shaping how odor information is represented and processed by the nervous system. Although the mouse has become a prominent model for studying olfaction, little is known about sniffing behavior in mice. Here, we characterized mouse sniffing behavior by measuring intranasal pressure transients in behaving mice. Sniffing was monitored during unstructured exploratory behavior and during performance of 3 commonly used olfactory paradigms: a habituation/dishabituation task, a sand digging-based discrimination task, and a nose poke-based discrimination task. We found that respiration frequencies in quiescent mice ranged from 3 to 5 Hz--higher than that reported for rats. During exploration, sniff frequency increased up to approximately 12 Hz and was highly dynamic, with rapid changes in frequency, amplitude, and waveform. Sniffing behavior varied strongly between tasks as well as for different behavioral epochs of each task. For example, mice performing the digging-based task showed little increase in sniff frequency prior to digging, whereas mice performing a nose poke-based task showed robust increases. Mice showed large increases in sniff frequency prior to reward delivery in all tasks. Mice also showed increases in sniff frequency when nose poking in a nonodor-guided task. These results show that mouse sniffing behavior is highly dynamic, varies with behavioral context, and is strongly modulated by olfactory as well as nonolfactory events.

Assessment of side exhaust systems for residential kitchens in Taiwan

In response to concerns about the health of housewives who are regularly exposed to excessive quantities of air pollutants when cooking, a number of domestic documents have recommended solutions such as: ‘decreasing the installation height of the range hoods’ or ‘using desk-top ventilators’. However, few if any studies have addressed the issue of how to make improvements to the traditional Taiwanese style of range hood. This study investigated the design and experimental assessment of side exhaust systems in a full-scale model kitchen. Tests were carried out to understand how different exhaust configurations could affect the overall exhaust performance. It was found that single-slot, twin-slot, and fence-slot exhausts close to the pot rims performed well in air exhalation, and ensured the indoor air quality in the kitchen was maintained an acceptable level. Practical application: That innovative side-sucking exhausts, installed closer to the pot rim in the residential kitchens, considered the pathway of the aerosol and made improvements to the traditional style of range hood. The proposed prototypes ensured that the indoor air quality in the kitchen was maintained at an acceptable level.

Thermal desorption-gas chromatographic determination of ethane and pentane in breath as potential markers of lipid peroxidation.

Formation of free radicals and lipoperoxidation occur at the onset of cellular damage. These effects are produced during normal metabolism and in pathological states. The peroxidation of polyunsaturated fatty acids, i.e. linoleic acid and linolenic acid, which are both cellular membrane compounds, induces ethane and pentane formation in pulmonary air exhalation. These two volatile hydrocarbons can be considered as potential lipoperoxidation markers. Methodological difficulties limit the use of these gases for assessment of free oxygen radical activity but we have developed and validated a non-invasive technique. A study was performed with ten healthy volunteers.