Changes In Airflow Resistance Research Articles

Acute effects of inhaled sulphur dioxide on pig nasal vascular and airway resistances.

People complain about nasal stuffiness after SO2 exposure. This study was to investigate the acute effects of SO2 on nasal vascular and airway resistances in anaesthetized pigs for elucidating the underlying vascular and control mechanisms. Controlled ventilation was passed to the lungs or retrogradely through each nasal cavity. Nasal airway and lower airway pressures were measured to reflect airflow resistance changes. Systemic arterial pressure and nasal arterial flow were measured to calculate nasal vascular resistance. Nasal and pulmonary SO2 challenges were given. At 2 ppm, SO2 decreased systemic blood pressure and nasal vascular resistance but increased nasal airway and lower airway resistances. With increasing level to 8 ppm, SO2 increased systemic arterial pressure, nasal vascular and lower airway resistances but decreased nasal airway resistance. Nasal and pulmonary challenges induced similar responses. Ipsilateral nasal challenge elicited bilateral responses. Ruthenium red abolished the responses to nasal challenges. Bilateral vagosympathectomy eliminated the responses to lung challenges. Hence, SO2 at 2 ppm causes nasal congestion through sensory reflex vasodilatation but at higher levels nasal decongestion through sensory reflex vasoconstriction. Nasal congestion coupled with bronchoconstriction at levels of SO2 below short-term exposure limit (STEL) (≤ 2 ppm) would limit SO2 entering the lungs. Nasal decongestion at levels of SO2 beyond STEL (> 2 ppm) can effectively decrease total airway resistance as concurrent strong bronchoconstriction may impair ventilation.

Effects of surface smoothness on inertial particle deposition in human nasal models

Computational fluid dynamics (CFD) predictions of inertial particle deposition have not compared well with data from nasal replicas due to effects of surface texture and the resolution of tomographic images. To study effects of geometric differences between CFD models and nasal replicas, nasal CFD models with different levels of surface smoothness were reconstructed from the same MRI data used to construct the nasal replica used by Kelly, Asgharian, Kimbell, and Wong (2004a) [ Aerosol Science and Technology, 38,1063–1071]. One CFD model in particular was reconstructed without any surface smoothing to preserve the detailed topology present in the nasal replica. Steady-state inspiratory airflow and Lagrangian particle tracking were simulated using Fluent software. Particle deposition estimates from the smoother models under-predicted nasal deposition from replica casts, which was consistent with previous findings. These discrepancies were overcome by including surface artifacts that were not present in the reduced models and by plotting deposition efficiency versus the Stokes number, where the characteristic diameter was defined in terms of the pressure-flow relationship to account for changes in airflow resistance due to wall roughness. These results indicate that even slight geometric differences have significant effects on nasal deposition and that this information should be taken into account when comparing particle deposition data from CFD models with experimental data from nasal replica casts.

The tendency to altered perception of airflow resistance in aged subjects might be due mainly to a reduction in diaphragmatic proprioception

Elderly patients with asthma, particularly those above the age of 80 years, appear less able to detect early worsening of their airflow resistance and hence might not take 'rescue' bronchodilator medication promptly. No consistent explanation for the observation has been posited. We hypothesize that deterioration in the sensitivity and accuracy of inspiratory (mainly diaphragmatic) proprioception is a plausible mechanism. This contention is supported by observations that indicate the central role of afferent phrenic nerve fibres arising from mechanoreceptors in diaphragmatic muscle and entheses in the ability to sense changes in intrathoracic pressure and volume. Other sensory afferent sources appear less important in this context because the ability to detect intrathoracic pressure and volume changes is preserved in patients with heart-lung transplants (parenchymal and airway denervation), topically anaesthetized upper airways and spinal cord transection below C4 (intact phrenic function) but not cord transection above C2 (phrenic function absent) if the airways are simultaneously anaesthetized. Further support for the hypothesis comes from demonstration of reduced integrated proprioceptive function in older subjects, such as increased postural sway, reduced ability to judge changes in joint position and slower recovery from eye and hand perturbation. In the context of asthma, the detection of a change in airflow resistance depends mainly on the subconscious detection of a mismatch between the inspiratory effort and the volume change achieved; the resulting discrepancy between length (volume) and tension (muscular effort) is felt as a sensation of obstructed breathing, resulting in greater effort to breath and conscious actions such as self-medication. Our hypothesis proposes that a reduced ability to detect accurately the volume change during tidal breathing delays the sensing of the obstruction in older subjects.

A Study of the Nonsteady-State Filtration Process in a Fibrous Material in Conditions of Real Dust Loading

The study concerns ways to describe filtration efficiency and gas flow resistance while particles are deposited in fibrous respiratory protective filters under conditions characteristic for their use. The performance of fibrous filter materials of varied structure and electrostatic properties was studied, using polydisperse coarse-grained aerosols and submicron aerosols of sodium chloride. Evidence was found that changes in airflow resistance depended to a large extent on air humidity and the concentration of the aerosol. A relationship was also found between the electrostatic properties of filter media and their decreasing efficiency with time. A numerical model was developed to simulate the phenomenon of nonsteady-state filtration for 2 mechanisms of deposition, which permitted assessment of the filtration characteristics of filter media of any design and in any conditions.

Clogging of Filtering Material Systems Used for Disposable Respirators

The article shows the problem of clogging in connection with the parameters of filtering materials used in respiratory protective equipment. The results of investigations of airflow resistance changes during the depositing of dust inside the filtering material are presented. The configuration of layers differing in mass per unit area and the number of layers, were taken into consideration. For each configuration, the clogging abilities and the changes of airflow resistance as a reason of loading with dust were assessed. The analysis of tested materials confirms the hypothesis that there is an important coincidence between the properties of the material used in filtering equipment and the clogging coefficient. The results show that the filter should have a layered structure and that the outer layer should be made of a nonwoven of relatively high surface density.

Reciprocating nasal airflow resistances.

Reciprocal changes in airflow resistance between nasal cavities are induced by lateral recumbency, and also by unilateral pressures to body surfaces in postures which avoid hydrostatic differences between sides. The reciprocating spontaneous nasal cycle in erect subjects and these nasal responses to lateral posture and pressure maintain total nasal resistance in the range of 2-3 cmH2O (0.2-0.3 KPa)/l/sec. In the resting subject, erect or recumbent, the centrally mediated autonomic tone of capacitance vessels of nasal erectile mucosa maintains an adequately patent nasal airway despite marked differences in airflow resistance between the nasal cavities which accompany lateral recumbency, asymmetrical body surface pressures or the spontaneous nasal cycle. In addition to passive hydrostatic influences on nasal mucosal blood content, activity of the vasomotor centre modified by impulses from pressure sensors of the body surfaces reciprocally alters the tone of the nasal capacitance vessels. Nasal disorders hamper these stabilizing reciprocal adjustments in airflow resistance and adversely affect breathing mechanics in recumbent subjects.

Perception of changes in airflow resistance in obstructive pulmonary disorders.

The perception of changes in airflow resistance was examined in normal subjects, asthmatics, and patients with chronic obstructive pulmonary disease (COPD) using the psychophysical tests of just noticeable differences and magnitude estimation. The just noticeable difference in airflow resistance expressed as a percentage of the baseline resistance (JND%) was 18 ± 2% SE in normal subjects and this value was not altered by changes in baseline resistance. The exponent for the magnitude estimation (ME) of airflow resistance was 0.93 ± 0.04 SE in normal subjects. Neither JND% nor ME were significantly different from normal in asthmatics. However, in patients with COPD, JND% was increased to 49 ± 7% SE (p < 0.01) and ME was reduced to 0.64 ± 0.10 SE (p < 0.01). In contrast to the abnormalities in the perception of changes in airflow resistance, the perception of heaviness during the lifting of small weights was the same in patients with COPD as in normal subjects and asthmatics. Measures of the perception of ch...

Respiratory responses to changes in airflow resistance in conscious man

The time course and magnitude of adjustments in respiratory activity during the application and following the removal of inspiratory resistive loads were determined in conscious men. Changes in airflow resistance were made periodically during rebreathing of a gas mixture of carbon dioxide and oxygen. Ventilation, the ratio of tidal volume to inspiratory duration and the mouth pressure during airway occlusion, 100 ms after the onset of inspiration were used as measures of inspiratory neuromuscular activity. The occlusion pressure was measured during each breath using an electrically activated solenoid shutter which obstructed the airway for only the first 100 ms of each inspiration. During the second breath following the application of the resistive load, there was an increase in inspiratory output which occured independently of changes in P CO 2 and P O 2 . Further increases in inspiratory activity during successive loaded breaths, however, were due exclusively to changing chemical drive. The level of inspiratory neuromuscular activity remained elevated for a single breath following removal of the added resistance. Adjustments in respiratory activity were greater the more severe the load. The results suggest that non-chemically mediated respiratory compensation in conscious individuals develops rapidly and is important in maintaining ventilation when breathing is encumbered.

The Perception of Changes in Airflow Resistance in Normal Subjects and Patients with Chronic Airways Obstruction

The Perception of Changes in Airflow Resistance in Normal Subjects and Patients with Chronic Airways Obstruction

The perception of changes in airflow resistance in normal subjects and patients with chronic airways obstruction

The perception of changes in airflow resistance in normal subjects and patients with chronic airways obstruction

Effect of Neo-Synephrine Nasal Spray on Pulmonary Resistance in Man

The study to be presented was undertaken in an attempt to investigate whether airflow stimulation in nose can or cannot initiate a change in tracheobronchial airway resistance in man. Eight subjects with nasal obstruction were tested both before and after the application of neo-synephrine nasal spray. Measurements of nasal resistance and pulmonary resistance were made during both nose and mouth breathing. The resistance of the conducting airways below the pharynx was obtained by subtracting the nasal resistance from the pulmonary resistance during nose breathing. Each airflow resistance was analyzed according to the Rohrer's equation. Probability was determined by studying the significance of the difference in airflow resistance before and after the application of the nasal spray. Its application resulted in a significant reduction in resistance during nose breathing. The main effect of the spray manifested itself as a reduction in the value of <i>k</i>₂. No statistically significant changes were noted concerning the value of <i>k</i>₁. There was a consistent change in airflow resistance after the application of neo-synephrine nasal spray during nasal breathing, whereas the pressure-flow patterns were similar to each other. However, no significant change was found during oral breathing. The interacting mechanism between nasal and pulmonary resistance that was observed after the application of neo-synephrine nasal spray was not explainable.

Pressures developed by loaded inspiratory muscles in conscious and anesthetized man.

ArticlePressures developed by loaded inspiratory muscles in conscious and anesthetized man.D J Read, S Freedman, and E R KaferD J Read, S Freedman, and E R KaferPublished Online:01 Aug 1974https://doi.org/10.1152/jappl.1974.37.2.207MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByResponse of roosters to resistive loads at constant chemical drive to breatheRespiration Physiology, Vol. 90, No. 2Effects of slow wave sleep on ventilatory compensation to inspiratory elastic loadingRespiration Physiology, Vol. 55, No. 1Theory of resistive load detectionRespiration Physiology, Vol. 51, No. 2Respiratory responses to changes in airflow resistance in conscious manRespiration Physiology, Vol. 36, No. 2Breathing pattern in men during inspiratory elastic loadsRespiration Physiology, Vol. 34, No. 2Vagal control of diaphragm timing in cat while breathing at elevated lung volumesRespiration Physiology, Vol. 30, No. 1-2 More from this issue > Volume 37Issue 2August 1974Pages 207-18 https://doi.org/10.1152/jappl.1974.37.2.207PubMed4853759History Published online 1 August 1974 Published in print 1 August 1974 Metrics

Reflex effects of chemical irritation of the upper airways on the laryngeal lumen in cats

Changes in airflow resistance of the larynx isolated in situ have been measured in spontaneously breathing cats, vagotomised in the chest, during chemical stimulation of the nose and larynx. Insufflation of ammonia vapour into the larynx inhibited breathing with a large increase in expiratory laryngeal resistance. These responses were abolished by cutting the superior laryngeal nerves, which established the afferent path for the reflex. Insufflation of ammonia into the nose caused sneezing or inhibition of breathing with expiratory increases in laryngeal resistance, which were smaller after sensory denervation of the larynx. The main afferent pathway for this reflex is probably in the trigeminal nerves. The laryngeal reflexes were generally more sensitive than those with the same stimuli affecting breathing.

The Effect of Cold Air Inhalation on Respiratory Gas Exchange During Exercise in Patients With Chronic Obstructive Pulmonary Disease

This study was done to determine whether gas exchange is affected, both at rest and with exercise, by airflow resistance alterations previously observed during cold air breathing in patients with chronic obstructive lung disease with a history of sensitivity to cold air. Nine patients with cold air sensitivity were studied at rest and daring treadmill exercise breathing room temperature and ?12°C air. Seven of the nine patients had more distress during cold air breathing, but there were no significant differences in heart rates, O2 consumption and arterial blood Po2 and Pco2 between room temperature and ?12°C air breathing, either at rest or during exercise. These results give support to the concept that the most marked change in air flow resistance during cold air breathing occurs in poorly ventilated lung areas.