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Respiratory Physiology & Neurobiology Jan 2013The explanted lung slice has become a popular in vitro system for studying how airways contract. Because the forces of airway-parenchymal interdependence are such...
The explanted lung slice has become a popular in vitro system for studying how airways contract. Because the forces of airway-parenchymal interdependence are such important modulators of airway narrowing, it is of significant interest to understand how the parenchyma around a constricting airway in a lung slice behaves. We have previously shown that the predictions of the 2-dimensional distortion field around a constricting airway are substantially different depending on whether the parenchyma is modeled as an elastic continuum versus a network of hexagonally arranged springs, which raises the question as to which model best explains the lung slice. We treated lung slices with methacholine and then followed the movement of a set of parenchymal landmarks around the airway as it narrowed. The resulting parenchymal displacement field was compared to the displacement fields predicted by the continuum and hexagonal spring network models. The predictions of the continuum model were much closer to the measured data than were those of the hexagonal spring network model, suggesting that the parenchyma in the lung slice behaves like an elastic continuum rather than a network of discrete springs. This may be because the alveoli of the lung slice are filled with agarose in order to provide structural stability, causing the parenchyma in the slice to act like a true mechanical continuum. How the air-filled parenchyma in the intact lung behave in vivo remains an open question.
Topics: Airway Resistance; Animals; Bronchi; Bronchoconstrictor Agents; Elasticity; Lung; Methacholine Chloride; Models, Biological; Muscle Contraction; Organ Culture Techniques; Stress, Mechanical
PubMed: 23128069
DOI: 10.1016/j.resp.2012.10.015 -
Journal of Speech, Language, and... Jun 2015The larynx has a dual role in the regulation of gas flow into and out of the lungs while also establishing resistance required for vocal fold vibration. This study...
PURPOSE
The larynx has a dual role in the regulation of gas flow into and out of the lungs while also establishing resistance required for vocal fold vibration. This study assessed reciprocal relations between phonatory functions-specifically, phonatory laryngeal airway resistance (Rlaw)-and respiratory homeostasis during states of ventilatory gas perturbations.
METHOD
Twenty-four healthy women performed phonatory tasks while exposed to induced hypercapnia (high CO2), hypocapnia (low CO2), and normal breathing (eupnea). Effects of gas perturbations on Rlaw were investigated as were the reciprocal effects of Rlaw modulations on respiratory homeostasis.
RESULTS
Rlaw remained stable despite manipulations of inspired gas concentrations. In contrast, end-tidal CO2 levels increased significantly during all phonatory tasks. Thus, for the conditions tested, Rlaw did not adjust to accommodate ventilatory needs as predicted. Rather, stable Rlaw was spontaneously accomplished at the cost of those needs.
CONCLUSIONS
Findings provide support for a theory of regulation wherein Rlaw may be a control parameter in phonation. Results also provide insight into the influence of phonation on respiration. The work sets the foundation for future studies on laryngeal function during phonation in individuals with lower airway disease and other patient populations.
Topics: Adolescent; Adult; Airway Resistance; Female; Homeostasis; Humans; Hypocapnia; Larynx; Middle Aged; Phonation; Respiration; Young Adult
PubMed: 25764093
DOI: 10.1044/2015_JSLHR-S-13-0270 -
Journal of Applied Physiology... Sep 2013Lung inflation has been shown to dilate airways by altering the mechanical equilibrium between opposing airway and parenchymal forces. However, it is not known how...
Lung inflation has been shown to dilate airways by altering the mechanical equilibrium between opposing airway and parenchymal forces. However, it is not known how heterogeneously such dilation occurs throughout the airway tree. In six anesthetized dogs, we measured the diameters of five to six central airway segments using high-resolution computed tomography, along with respiratory input impedance (Zrs) during generalized aerosol histamine challenge, and local histamine challenge in which the agonist was instilled directly onto the epithelia of the imaged central airways. Airway diameters and Zrs were measured at 12 and 25 cmH2O. The Zrs spectra were fitted with a model that incorporated continuous distributions of airway resistances. Airway heterogeneity was quantified using the coefficient of variation for predefined airway distribution functions. Significant reductions in average central airway diameter were observed at 12 cmH2O for both aerosolized and local challenges, along with significant increases upon inflation to 25 cmH2O. No significant differences were observed for the coefficient of variation of airway diameters under any condition. Significant increases in effective airway resistance as measured by Zrs were observed only for the aerosolized challenge at 12 cmH2O, which was completely reversed upon inflation. We conclude that the lung periphery may be the most dominant contributor to increases in airway resistance and tissue elastance during bronchoconstriction induced by aerosolized histamine. However, isolated constriction of only a few central airway segments may also affect tissue stiffness via interdependence with their surrounding parenchyma.
Topics: Aerosols; Airway Resistance; Animals; Bronchoconstriction; Dogs; Histamine; Lung; Lung Compliance; Male; Respiratory Mechanics; Respiratory Mucosa
PubMed: 23813528
DOI: 10.1152/japplphysiol.00476.2013 -
Jornal Brasileiro de Pneumologia :... 2012To measure airway resistance with the interrupter resistance (Rint) technique in patients with cystic fibrosis (CF) and to determine whether Rint values correlate with...
OBJECTIVE
To measure airway resistance with the interrupter resistance (Rint) technique in patients with cystic fibrosis (CF) and to determine whether Rint values correlate with spirometric parameters, as well as to evaluate the accuracy of the Rint technique in determining the airway response to a bronchodilator.
METHODS
This was a cross-sectional study involving 38 children and adolescents with CF followed at the Cystic Fibrosis Outpatient Clinic of the São Lucas Hospital, located in the city of Porto Alegre, Brazil. After Rint had been measured, the subjects underwent spirometry. To evaluate bronchodilator response, we repeated the measurements after the use of inhaled albuterol.
RESULTS
There was a strong correlation between inverse Rint and FEV1 (r = 0.8; p < 0.001), and there was a moderate correlation between inverse Rint and FEF25-75% (r = 0.74; p < 0.001), as well as between inverse Rint and body mass index (r = 0.62; p < 0.001). We used a ROC curve to compare the bronchodilator response, as determined by Rint, with spirometric values. For a Rint cut-off point of -28%, the area under the curve was 0.75, with a sensitivity of 66% and a specificity of 82%.
CONCLUSIONS
Our findings suggest that Rint correlates well with spirometric parameters, although the Rint technique was not sufficiently accurate to replace spirometry in the evaluation of bronchodilator responses.
Topics: Adolescent; Airway Resistance; Albuterol; Brazil; Bronchodilator Agents; Child; Child, Preschool; Cross-Sectional Studies; Cystic Fibrosis; Female; Humans; Male; Respiratory Function Tests; Spirometry
PubMed: 22576426
DOI: 10.1590/s1806-37132012000200007 -
The European Respiratory Journal Jan 2002
Topics: Airway Resistance; Altitude; Environment, Controlled; Humans; Nose
PubMed: 11843326
DOI: 10.1183/09031936.02.00282902 -
European Journal of Orthodontics Aug 2004The purpose of this study was to evaluate nasal airway resistance (NAR) during rapid maxillary expansion (RME) using acoustic rhinometry (AR). The sample comprised 22...
The purpose of this study was to evaluate nasal airway resistance (NAR) during rapid maxillary expansion (RME) using acoustic rhinometry (AR). The sample comprised 22 children (13 girls and nine boys) with maxillary constriction. The mean age was 12.9 +/- 1.54 years and all patients were found to have normal nasal cavities following anterior rhinoscopic examination. A modified bonded splint type RME appliance was used for expansion. AR was used to measure NAR before (T1), during (T2) and after (T3) expansion, and at the end of retention (T4). Each AR recording was performed, for each patient, with and without the use of a decongestant. Subjective evaluation of reported changes in nasal breathing were also undertaken at T3. The results showed that NAR was significantly reduced with the use of RME, with the main decrease observed during expansion (P < 0.05). The use of a decongestant was not found to have any effect on the results. Subjective evaluation showed that 59 per cent of patients considered that their nasal breathing had improved following RME.
Topics: Adolescent; Airway Resistance; Child; Endoscopy; Female; Follow-Up Studies; Humans; Male; Malocclusion; Maxillary Diseases; Nasal Cavity; Nasal Decongestants; Nose; Orthodontic Appliance Design; Palatal Expansion Technique; Patient Satisfaction; Respiration; Rhinometry, Acoustic
PubMed: 15366384
DOI: 10.1093/ejo/26.4.397 -
Journal of Applied Physiology... Jul 1994In five open-chest dogs and with four to five alveolar capsules we used an optimal ventilator waveform (OVW) to follow frequency and tidal volume (VT) dependence of...
In five open-chest dogs and with four to five alveolar capsules we used an optimal ventilator waveform (OVW) to follow frequency and tidal volume (VT) dependence of lung, airway, and tissue resistance (R) and elastance (E) before and during constant infusion of histamine (16 micrograms.kg-1.min-1). OVW contains sufficient flow energy between 0.234 and 4.7 Hz, avoids nonlinear harmonic interactions, and simultaneously ventilates with physiological VT. Each OVW breath permits a smooth estimate of frequency dependence of R and E for the whole lung. A constant-phase model analysis provided estimates of purely viscous resistance (Rvis), which represents the sum of airway resistance (Raw) and any purely newtonian component of tissue resistance (Rti), and parameters G and H, which govern frequency dependence of Rti and tissue elastance (Eti), respectively. Tissue structural damping (eta) is calculated as G/H. This model was applied to the whole lung and tissue impedance as estimated from each capsule. We found a small but inconsequential purely newtonian component of Rti, even during constriction. Four dogs showed a peak response at approximately 4 min in lung Rvis coupled (in time) to initial increases in G, H, eta, and airway inhomogeneities. In two of these dogs the response was severe. Tissue properties estimated from whole lung impedance (G, H, and eta) were nearly identical to values estimated from unobstructed capsules throughout infusion. By using a technique independent of alveolar capsules, our results indicate that a major if not dominant response to a constrictive agonist occurs in lung tissues, resulting in a large increase in Rti and Eti. With severe constriction, significant increases occur in Raw and airway inhomogeneities as well. Finally, separation of airway and tissue properties using input impedance estimated from the frequency-rich OVW avoids use of alveolar capsules and may prove an effective tool for partitioning airway and tissue properties in humans.
Topics: Airway Resistance; Animals; Bronchoconstriction; Carbon Dioxide; Dogs; Female; Histamine; Lung; Lung Compliance; Male; Models, Biological; Pulmonary Alveoli; Respiration, Artificial; Respiratory Mechanics; Respiratory Physiological Phenomena; Respiratory System
PubMed: 7961260
DOI: 10.1152/jappl.1994.77.1.373 -
Journal of Voice : Official Journal of... Sep 1998A noninvasive pressure-flow technique was used to compare laryngeal airway resistances in nine female classroom teachers with symptoms of vocal fatigue and seven... (Comparative Study)
Comparative Study
A noninvasive pressure-flow technique was used to compare laryngeal airway resistances in nine female classroom teachers with symptoms of vocal fatigue and seven teachers without symptoms of vocal fatigue. Data were collected two times per day on the Monday, Wednesday, and Friday of a typical work-week. No significant between-group differences were found, but two within-group differences were notable. Airflow in the fatigued subjects decreased across the sampling period (p = .0009). In the controls, air pressure increased across the sampling period (p = .021). These findings suggest that both groups may have reacted to vocal demands during the week by employing two different strategies to maintain habitual laryngeal airway resistance: laryngeal adjustments alone or laryngeal adjustments plus increased respiratory drive. The first strategy, employed by the fatigued subjects, may have been less efficient, thereby provoking conditions associated with their vocal fatigue.
Topics: Adult; Airway Resistance; Fatigue; Female; Humans; Larynx; Occupational Diseases; Phonation; Teaching; Voice Quality
PubMed: 9763179
DOI: 10.1016/s0892-1997(98)80019-2 -
Sheng Li Xue Bao : [Acta Physiologica... Feb 2014People complain about nasal stuffiness after SO2 exposure. This study was to investigate the acute effects of SO2 on nasal vascular and airway resistances in...
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.
Topics: Administration, Inhalation; Airway Resistance; Animals; Lung; Nasal Cavity; Respiration; Sulfur Dioxide; Swine; Vascular Resistance; Vasodilation
PubMed: 24553872
DOI: No ID Found -
Chest Nov 2015
Topics: Airway Resistance; Humans; Oscillometry; Respiratory Tract Diseases
PubMed: 26020800
DOI: 10.1378/chest.15-0106