Mouth Inhalation Research Articles

Performance analysis of a novel personalized air curtain for preventing inhalation of particulate matters in industrial environments

Personalized air curtains promise to reduce respiratory exposure in industrial environments. This work explored the performance of normal safe helmets equipped with air curtains to prevent workers from particulate matters via computational fluid dynamics (CFD) method. The impact of human body heat, breathing modes (nose and mouth inhalation), and air curtain characters (opening angle, tilt angle, and opening width) on protective efficiency were analyzed under different air supply velocities. Results showed that the interaction between the downward jet supplied by the air curtain helmet and the free convection flow generated by the thermal human body significantly affects respiratory exposure. There is a critical air supply velocity, i.e., when the jet velocity is greater than this value, the flow field in the breathing zone was dominated by the downward jet; otherwise, it is dominated by free convection flow. Both human body heat and breathing modes have significant effects on the protective effect of the air curtain. The opening angle of 180o, the tilt angle of 0o, the opening width of 3 cm, and the air supply velocity of 0.5 m/s are recommended due to a high protection effect of around 1. This study can provide effective and intuitive guidance in applying personalized air curtains for respiratory protection in highly contaminated industrial environments.

Gold Standard? Method of Citric Acid Solution Swallowing Test as a Screening Test for Patients with Tracheostomy.

This study aimed to apply various ranges of citric acid levels in the mouth and T-cannula to compare the validity with instrumental aspiration measures in patients with tracheostomy. Sixty-one patients underwent the citric acid cough reflex test (CRT) and videofluoroscopic swallowing study (VFSS). Citric acid was delivered via facemask and T-cannula at concentrations of 0.4mol/L, 0.6mol/L, and 0.8mol/L. Further, we recorded the coughing count and presence of ≥ 2 (C2) and ≥ 5 (C5) coughs. CRT via facemask at 0.4mol/L C2, 0.6mol/L C5, and 0.8mol/L C2 and C5 were significantly associated with the presence of tracheal aspiration during VFSS. The sensitivity and specificity were optimized at 0.8mol/L C2 for mouth inhalation and at 0.8mol/L C5 for T-cannula inhalation. There was a significant difference in the coughing count during CRT at 0.4 mol/Land 0.8 mol/Lvia mouth inhalation between patients with or without tracheal aspiration, but not via T-cannula. The AUC for 0.8mol/L facemask inhalation was 0.701. The optimal cut-off value of coughing count was thrice with 84.62% sensitivity and 50.00% specificity on the ROC curve. Afferent sensory nerve desensitization around and below the tracheostomy site could affect coughing reflex initiation and decrease the sensitivity of detecting aspiration in tracheotomized patients. The citric acid CRT via facemask can reliably detect tracheal aspiration and presence of coughing reflex compared to that via T-cannula in patients with tracheostomy.

Signal Changes in Hippocampal Subfields during Controlled Breathing Patterns by Using Functional MRI

The purpose of this study was to investigate the functional properties of each hippocampal subfield and determine its association with decreased working memory due to abnormal breathing. Eleven healthy volunteers participated in this study and performed a breathing task in magnetic resonance imaging (MRI). To quantify the effects of various breathing patterns on the hippocampus, we segmented its subfields and then applied them to the functional MRI (fMRI) data to measure the signal change according to the respiration pattern. The results indicated that mouth breathing (mouth inhalation and exhalation) had the biggest effect on signal change. Of all subfields studied, the hippocampal head showed the greatest change. These findings imply that mouth breathing can significantly induce blood oxygenation level-dependent (BOLD) signal change in the hippocampus; especially, the hippocampal head is the most susceptible to breathing alterations, suggesting that it could be strongly associated with poor working memory in habitual mouth-breathers.

A semi-empirical model of aerosol deposition in the human respiratory tract for mouth inhalation.

A mathematical model for regional deposition of aerosols following inhalations via mouth has been developed. The model is in the form of algebraic equations which make it particularly efficient for computation of deposition of polydisperse aerosols. The parameters of the model were derived from average experimental data for "head' and tracheobronchial deposition which were supplemented by results of previous theoretical calculations and mass balance considerations. An example is presented to illustrate an application of the model to a problem in formulation of inhalation aerosols. To make the calculations more reliable for particular patho-physiological groups of patients, some modifications of the parameters used in the model are necessary. The model may be suitable, e.g. for testing the changes in regional deposition which would be likely to result from modification of particle size and related formulation properties of inhalation aerosols.

Dispersal kinetics of deuterated water in the lungs and airways following mouth inhalation: real-time breath analysis by flowing afterglow mass spectrometry (FA-MS)

Pulmonary oedema is a medical condition characterized by abnormal accumulation of fluid in the extravascular space in the alveoli. Effective oxygenation is impaired and this leads to significant short- and long-term morbidity and mortality. The detection and monitoring of pulmonary oedema by measuring lung water volume is therefore crucial in the initiation and guidance of therapeutic intervention. The current gold standard bedside measurement of extravascular lung water volume (EVLW) is the dilution method using various indicators, but despite the good correlation of the results with those obtained using the post-mortem gravimetric method, the invasiveness of the dilution technique limits its general application in the wider clinical setting. In the present preliminary experiments, the dispersal kinetics of deuterium (actually HDO) in exhaled breath of three healthy participants following the inhalation of deuterium oxide (D2O) vapour are explored as monitored using flowing afterglow mass spectrometry (FA-MS). Here, we present the basic ideas of lung water estimation using this novel technique, and briefly discuss its limitations and required future work.

Inhalability of micron particles through the nose and mouth

Aspiration efficiencies from nose and mouth inhalations are investigated at low and high inhalation rates by using the commercial Computational Fluid Dynamics (CFD) software CFX 11. A realistic human head with detailed facial features was constructed. Facial features were matched to represent the 50th percentile of a human male, aged between 20 and 65 years old, based on anthropometric data. The constant freestream velocity was 0.2 ms−1, normal to the face, and inhalation rates through the mouth and nose were 15 liters per minute (LPM) for light breathing and 40 LPM for heavy breathing. It was found that the flow field in the near breathing region exhibited vertical direction caused by the presence of the torso where the airstream diverges as it flows around and over the body. The critical area concept was used as a tool to determine the aspiration efficiency of particles. Comparisons between critical areas for the nose and mouth inhalations show similar geometric properties such as the area’s shape, and its vertical distance location on the x-z plane located at y = 80 cm upstream. The critical area sizes were found to be slightly larger for the mouth inhalation mainly due to the larger mouth area and also the aligned orientation of the mouth to the upstream flow, whereas the nose is perpendicular to the upstream flow. This study was undertaken to establish the flow field in the near breathing region that will help to characterize the flow and particle field for initial boundary conditions leading to a more holistic modeling approach of respiration through the internal nasal cavity and mouth.

Smoking Cessation Interventions in Clinical Practice

Objectives: Physicians are in a unique position to advise smokers to quit by integrating the various aspects of nicotine dependence. This review provides an overview of interventions for smokers presenting in a clinical setting. Results: Strategies used for smoking cessation counselling differ according to patient’s readiness to quit. For smokers who do not intend to quit smoking, physicians should inform and sensitise them about tobacco use and cessation. For smokers who are dissonant, physicians should use motivational strategies, such as discussing barriers to cessation and their solutions. For smokers ready to quit, the physician should show strong support, help set a quit date, prescribe pharmaceutical therapies for nicotine dependence, such as nicotine replacement therapy (i.e., gum, transdermal patch, nasal spray, mouth inhaler, lozenges, micro and sublingual tablets) and/or bupropion (atypical antidepressant thought to work by blocking neural reuptake of dopamine and/or nor epinephrine), with instructions for use, and suggest behavioural strategies to prevent relapse. The efficacy of all of these pharmacotherapies is comparable, roughly doubling cessation rates over control conditions. Varenicline is a promising new effective drug recently approved by many health authorities. Conclusion: Physician counselling and pharmacotherapeutic interventions for smoking cessation are among the most cost-effective clinical interventions.

Treating tobacco use and dependence in clinical practice

Physicians are in a unique position to advise smokers to quit by the ability to integrate the various aspects of nicotine dependence. This review provides an overview of the intervention strategies for smokers presented in a primary care setting. The strategies that are used for smoking cessation counselling differ according to the patient’s readiness to quit. For smokers who do not intend to give up smoking, physicians should inform about tobacco use and the benefits of cessation. For smokers who are dissonant, physicians should use motivational strategies, such as discussing the barriers to successful cessation and their solutions. For smokers who are ready to quit, the physician should show strong support, help set a date to quit, prescribe pharmaceutical therapies for nicotine dependence, such as nicotine replacement therapy (i.e., gum, transdermal patch, nasal spray, mouth inhaler, lozenges, and micro and sublingual tablets) and/or bupropion (an atypical antidepressant thought to work by blocking the neural re-uptake of dopamine and/or noradrenaline), with instructions for use, and suggest behavioural strategies to prevent relapse. The efficacy of all of these pharmacotherapies is comparable, roughly doubling the cessation rates over control conditions.

Quantitative EEG patterns during nose versus mouth inhalation of filtered room air in young adults with and without self-reported chemical odor intolerances

Individuals who report illness (e.g. nausea, headache) from common chemical odors tend to report CNS symptoms suggestive of olfactory-limbic system involvement. This study compared the resting quantitative electroencephalographic (qEEG) patterns of young adult college students reporting subjectively elevated chemical odor intolerance ratings (HICI) with those of controls reporting little or no odor intolerance (LOCI). Each group was subdivided into those with higher (HIDEP) vs. lower (LODEP) ratings of concomitant depression. Nineteen channels of EEG were recorded during a single session over four separate rest periods, respectively, following baseline, cognitive, chemical exposure and olfactory identification tests. Each recording involved two 30-s, eyes-closed, filtered room air breathing conditions: (1) nose inhalation followed by mouth exhalation and (2) mouth inhalation followed by mouth exhalation. HICI showed significantly less beta 1 (β1) over the temporal–central region during nose than during mouth inhalation. Over some temporal and central leads, task, DEP and CI interacted to influence β1 as well. For theta (θ), CI differences emerged during nose inhalation after the cognitive task at Cz, after chemical exposures at C3, Cz and C4 and after the olfactory ID task at C4. CI differences emerged during mouth breathing after the olfactory ID task at Cz, C4 and T4. The T5–T6 coronal array showed significant CI differences after chemical exposures during nose breathing and during mouth breathing after the cognitive and olfactory ID tasks. The θ findings in the HICI may be related to reports of disturbed attention in CI.

Brain and odor: IL EEG activity during nose and mouth breathing

Previous investigations have suggested that low, undetectable concentrations of odor chemicals alter central nervous system (CNS) activity. Since there can be no odor-free environment, room air also may alter CNS activity. To examine this hypothesis, EEG data were recorded from 20 subjects while they inhaled room air through the mouth or the nose. Results of the experiment indicated that EEG alpha activity in the left hemisphere was reduced for individuals inhaling through the nose, and that EEG beta activity showed greater spatial diversity during nose inhalations. These results demonstrate that room air passing through the nose has a desynchroniz-ing effect upon the EEG and may contain odor information not available through mouth inhalation. These results further substantiate the hypothesis that undetected odors markedly alter ongoing CNS activity.

The human head as a blunt aerosol sampler

A mathematical model is developed of the human head to investigate the aspiration of particles by mouth and nose breathing. It is assumed that the particles are suspended without sedimentation in a fluid which is flowing past the head. The model potential problem is solved using a numerical approach and results are given for two cases, namely when the particles are assumed to (i) bounce off the sampler surface and (ii) adhere to the sampler surface. These results are compared with the existing experimental data. As this is a first attempt at mathematically modelling the problem for nose breathing a two-dimensional model is postulated and when comparing this model with a two-dimensional model for mouth breathing the results are found to be similar, thus in agreement with experimental evidence. The results are also found to display the same broad trends as the experimental data. From the similarity of the results for nose and mouth inhalation it appears that only one of the two situations needs to be considered and therefore the three-dimensional model of mouth breathing presented here could be adapted for a future study of human inhalation.

Prediction of Drug Residence Times in Regions of the Human Respiratory Tract Following Aerosol Inhalation

A mathematical model was developed for predicting drug residence kinetics in various regions of the human respiratory tract (RT). The model allows for regional deposition of different dose fractions (following mouth inhalation of various particle sizes according to four popular breathing regimes). Predicted alveolar deposition was dependent on the mode of inhalation and breath-holding. Deposition in the ciliated airways, however, was largely unaffected by breath-holding and was at a maximum for aerodynamic diameters between 5–9 μm (slow inhalation) and 3–6 μm (fast inhalation). Selected mucociliary and absorption rate constants determined the durations (T) taken to deplete the initial deposition in a chosen lung region to a selected minimum dose fraction (MDF). Values of T for an MDF of 0.01 in the ciliated airways were dependent on aerosol size, mode of inhalation, and rate of dissolution. In the case of rapidly dissolving solutes, the maximum duration was short (1–2 h) and occurred at particle sizes and modes of inhalation which maximized deposition in the conducting airways. For less soluble particles, however, T in the same airways could approach 12h due to a prolonged supply of particles from the alveolar regions. The optimal size distribution and the mode of inhalation for maximum duration differed substantially in each case. The model enables formulation of testable hypotheses relating to the extension of local drug residence in the RT following inhalation of therapeutic aerosols.