Effect of methacholine on low-frequency mechanics of canine airways and lung tissue

1993 ◽  
Vol 75 (1) ◽  
pp. 55-62 ◽  
Author(s):  
J. Sato ◽  
B. Suki ◽  
B. L. Davey ◽  
J. H. Bates
Keyword(s):  
Continuous Distribution ◽  
Low Frequency ◽  
Constant Term ◽  
Ventilation Distribution ◽  
Regional Ventilation ◽  
Ventilation Inhomogeneity ◽  
Tracheal Pressure ◽  
Before And After ◽  
Volume Oscillation ◽  
Uneven Ventilation

We measured tracheal flow, tracheal pressure, and alveolar capsule pressure in four anesthetized paralyzed tracheostomized open-chest dogs. Lung impedance between 0.12 and 4.88 Hz was measured with a forced volume oscillation technique before and after the intravenous administration of methacholine (MCh). Before MCh administration, lung impedance was well described by a model featuring a single airway leading to an alveolar region surrounded by tissue with a continuous distribution of viscoelastic time constants as used by Hantos et al. (J. Appl. Physiol. 68: 849–860, 1990). After MCh, however, this model gave a poor fit to the impedances. The impedances were well accounted for, however, when the model was enhanced to include an extra time constant term, which we suspect is required to account for the uneven ventilation distribution produced by MCh. Airway impedance before MCh administration was well described by a simple resistance-inertance model, but a model incorporating serial inhomogeneity of ventilation was again required after MCh. Our results support those of previous studies indicating that the impedance of the normal dog lung is well described by a homogeneously ventilated viscoelastic tissue model. In contrast, our results after MCh administration show strong evidence of marked regional ventilation inhomogeneity in addition to the rheological properties of the tissues.

Effect of bronchomotor tone on static mechanical properties of lung and ventilation distribution

1987 ◽  
Vol 63 (6) ◽  
pp. 2278-2285 ◽  
Author(s):  
A. B. Crawford ◽  
M. Makowska ◽  
L. A. Engel
Keyword(s):  
Mechanical Properties ◽  
Normal Subjects ◽  
Elastic Recoil ◽  
Ventilation Distribution ◽  
Ventilation Inhomogeneity ◽  
Before And After ◽  
Static Mechanical ◽  
Lung Periphery ◽  
Static Mechanical Properties ◽  
Bronchomotor Tone

To study the relationship between bronchomotor tone, static mechanical properties of the lung, and ventilation distribution, we measured the pressure-volume (P-V) curve of the lung and several ventilatory indexes before and after intravenous atropine in eight normal subjects. The indexes of ventilation distribution were derived from multiple breath N2 washouts by a recently developed analysis (7,8). The latter not only provides a sensitive measure of overall ventilation inhomogeneity but distinguishes between the convection-dependent inhomogeneity (CDI) among larger lung units and that due to the interaction of convection and diffusion (DCDI) within the lung periphery. Atropine decreased lung elastic recoil but distensibility, as defined by the exponent (K) in the monoexponential analysis of the P-V data, was unchanged. The overall ventilation inhomogeneity increased by 37% after atropine (P less than 0.02) due to an increase in the CDI component. More importantly, there was a significant correlation between the loss of lung recoil (but not K) and each of the indexes of CDI among the subjects. There was no correlation between the changes in lung recoil and in DCDI. Our findings indicate that normal bronchomotor tone contributes to the elastic recoil of the lung. Furthermore, the tone is distributed in a way that enhances the uniformity of ventilation distribution among diffusion-independent lung units. Presumably this is achieved by minimizing interacinar intrinsic inequalities in static mechanical properties.

Influence of bronchomotor tone on regional ventilation distribution at residual volume

1976 ◽  
Vol 40 (3) ◽  
pp. 411-416 ◽  
Author(s):  
L. A. Engel ◽  
L. Landau ◽  
L. Taussig ◽  
R. R. Martin ◽  
G. Sybrecht
Keyword(s):  
Normal Subjects ◽  
Ventilation Distribution ◽  
Regional Ventilation ◽  
Critical Opening ◽  
Topographical Distribution ◽  
Before And After ◽  
Lower Lung ◽  
The Difference ◽  
Opening And Closing ◽  
Bronchomotor Tone

We studied the topographical distribution of 133Xe boluses inhaled slowly from RV, as well as the distribution of regional volumes at RV (RVr) in seven seated normal subjects before and after aerosolized isoprenaline (ISO) and after aerosolized methacholine hydrochloride (Mech). After Mech the ratio of inhaled 133Xe in the upper lung regions to that in lower lung regions (U/L) decreased from 3.21 +/- .33 (mean +/- 1 SE) to 1.27 +/- 0.12 (P less than 0.001) and returned to 3.89 +/- 0.55 after Iso. Iso alone increased U/L from 3.23 +/- 0.47 to 5.49 +/- 0.85 (P less than 0.025). The height of phase IV in expired 133Xe vs. volume plots correlated with U/L, being greater after Iso and smaller after Mech in each subject. The difference in RVr between upper and lower lung regions decreased after Mech in four out of five subjects from 0.22 TLC to 0.11 TLC. Iso alone did not change the gradient of RVr. The results are consistent with the concept that increased bronchomotor tone widens the range of critical opening and closing pressures with a more patchy and extensive distribution of airway closure.

scholarly journals The prone position results in smaller ventilation defects during bronchoconstriction in asthma

2009 ◽  
Vol 107 (1) ◽  
pp. 266-274 ◽  
Author(s):  
R. Scott Harris ◽  
Tilo Winkler ◽  
Guido Musch ◽  
Marcos F. Vidal Melo ◽  
Tobias Schroeder ◽  
...  
Keyword(s):  
Prone Position ◽  
Body Position ◽  
Low Frequency ◽  
Vertical Direction ◽  
Gas Content ◽  
Regional Ventilation ◽  
Positron Emission ◽  
Volume Ventilation ◽  
Lung Expansion ◽  
Before And After

The effect of body posture on regional ventilation during bronchoconstriction is unknown. In five subjects with asthma, we measured spirometry, low-frequency (0.15-Hz) lung elastance, and resistance and regional ventilation by intravenous 13NN-saline positron emission tomography before and after nebulized methacholine. The subjects were imaged prone on 1 day and supine on another, but on both days the methacholine was delivered while prone. From the residual 13NN after washout, ventilation defective areas were defined, and their location, volume, ventilation, and fractional gas content relative to the rest of the lung were calculated. Independent of posture, all subjects developed ventilation defective areas. Although ventilation within these areas was similarly reduced in both postures, their volume was smaller in prone than supine (25 vs. 41%, P < 0.05). The geometric center of the ventilation defective areas was gravitationally dependent relative to that of the lung in both postures. Mean lung fractional gas content was greater in the prone position before methacholine and did not increase as much as in the supine position after methacholine. In the prone position at baseline, areas that became ventilation defects had lower gas content than the rest of the lung. In both positions at baseline, there was a gradient of gas content in the vertical direction. In asthma, the size and location of ventilation defects is affected by body position and likely affected by small differences in lung expansion during bronchoconstriction.

scholarly journals Impact of artificial airway resistances on regional ventilation distribution during airway closure

2020 ◽  
Vol 6 (3) ◽  
pp. 32-35
Author(s):  
Melanie März ◽  
Sarah Howe ◽  
Bernhard Laufer ◽  
Knut Moeller ◽  
Sabine Krueger-Ziolek
Keyword(s):  
Pulmonary Function ◽  
Airway Resistance ◽  
Airway Closure ◽  
Ventilation Distribution ◽  
Regional Ventilation ◽  
Impedance Tomography ◽  
Artificial Airway ◽  
Normal Breathing ◽  
Airway Obstructions ◽  
Forced Breathing

AbstractElectrical impedance tomography (EIT), a noninvasive and radiation-free imaging technique can be used in pulmonary function monitoring for determining regional ventilation distribution within the lung. Gold standard in pulmonary function monitoring is spirometry/body plethysmography, a method using forced breathing maneuvers to obtain global lung function parameters. However, this method is heavily dependent on the cooperation of the patients. Within this observational study, a method under normal breathing was tested with 5 healthy volunteers, which provides regional information about ventilation distribution. The occlusion method Rocc, a method for determining airway resistance, was used to create a short-term airway closure. Regional ventilation during the airway closure was examined with EIT. Simultaneously four different artificial airway resistances were used to simulate airway obstructions. Results show that EIT in combination with the ROcc method is suitable for the detection of regional differences in ventilation during airway closure for all four artificial airway resistances. Although the sum of relative impedances at the end of the shutter maneuver are smaller (nearly -0.100 AU) for the airway resistances Ø 12.5 mm, Ø 10.5 mm and Ø 9.5 mm than for the smallest one with Ø 30.0 mm (~ -0.070 AU), the changes in impedance from the start to the end of the shutter maneuver differs only slightly between the four artificial airway resistances. All impedance changes are in the range of 0.100 to 0.130 AU. The combination of EIT and the ROcc method provides not only global parameters such as airway resistance under normal breathing conditions, but also results of regional ventilation, which could enable the identification of areas affected by airway obstructions. However, the obtained results indicate that EIT might be a useful tool in the diagnosis and follow-up of obstructive lung diseases.

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

Comparative study on effect of neutral spinal bath and neutral spinal spray on blood pressure, heart rate and heart rate variability in healthy volunteers

2018 ◽  
Vol 16 (2) ◽  
Author(s):  
Arundhati Goley ◽  
A. Mooventhan ◽  
NK. Manjunath
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Healthy Volunteers ◽  
Group Analysis ◽  
Low Frequency ◽  
Single Session ◽  
Arterial Blood ◽  
Before And After ◽  
Instantaneous Heart Rate

Abstract Background Hydrotherapeutic applications to the head and spine have shown to improve cardiovascular and autonomic functions. There is lack of study reporting the effect of either neutral spinal bath (NSB) or neutral spinal spray (NSS). Hence, the present study was conducted to evaluate and compare the effects of both NSB and NSS in healthy volunteers. Methods Thirty healthy subjects were recruited and randomized into either neutral spinal bath group (NSBG) or neutral spinal spray group (NSSG). A single session of NSB, NSS was given for 15 min to the NSBG and NSSG, respectively. Assessments were taken before and after the interventions. Results Results of this study showed a significant reduction in low-frequency (LF) to high-frequency (HF) (LF/HF) ratio of heart rate variability (HRV) spectrum in NSBG compared with NSSG (p=0.026). Within-group analysis of both NSBG and NSSG showed a significant increase in the mean of the intervals between adjacent QRS complexes or the instantaneous heart rate (HR) (RRI) (p=0.002; p=0.009, respectively), along with a significant reduction in HR (p=0.002; p=0.004, respectively). But, a significant reduction in systolic blood pressure (SBP) (p=0.037) and pulse pressure (PP) (p=0.017) was observed in NSSG, while a significant reduction in diastolic blood pressure (DBP) (p=0.008), mean arterial blood pressure (MAP) (p=0.008) and LF/HF ratio (p=0.041) was observed in NSBG. Conclusion Results of the study suggest that 15 min of both NSB and NSS might be effective in reducing HR and improving HRV. However, NSS is particularly effective in reducing SBP and PP, while NSB is particularly effective in reducing DBP and MAP along with improving sympathovagal balance in healthy volunteers.

Reversal of muscle fatigue during 16 h of heavy intermittent cycle exercise

2004 ◽  
Vol 97 (6) ◽  
pp. 2166-2175 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
S. Ferth ◽  
G. P. Holloway ◽  
M. M. Thomas ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Muscle Fatigue ◽  
Intermittent Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Stimulation Frequency ◽  
Peak Oxygen Consumption ◽  
Force Frequency ◽  
Reduction In Force ◽  
Before And After

This study examined the effects of extended sessions of heavy intermittent exercise on quadriceps muscle fatigue and weakness. Twelve untrained volunteers (10 men and 2 women), with a peak oxygen consumption of 44.3 ± 2.3 ml·kg−1·min−1, exercised at ∼91% peak oxygen consumption for 6 min once per hour for 16 h. Muscle isometric properties assessed before and after selected repetitions (R1, R2, R4, R7, R12, and R15) were used to quantitate fatigue (before vs. after repetitions) and weakness (before vs. before repetitions). Muscle fatigue at R1 was indicated by reductions ( P < 0.05) in peak twitch force (135 ± 13 vs. 106 ± 11 N) and by a reduction ( P < 0.05) in the force-frequency response, which ranged between ∼53% at 10 Hz (113 ± 12 vs. 52.6 ± 7.4 N) and ∼17% at 50 Hz (324 ± 27 vs. 270 ± 30 N). No recovery of force, regardless of stimulation frequency, was observed during the 54 min between R1 and R2. At R2 and for all subsequent repetitions, no reduction in force, regardless of stimulation frequency, was generally found after the exercise. The only exception was for R2, where, at 20 Hz, force was reduced ( P < 0.05) by 18%. At R15, force before repetitions for high frequencies (i.e., 100 Hz) returned to R1 (333 ± 29 vs. 324 ± 27 N), whereas force at low frequency (i.e., 10 Hz) was only partially ( P < 0.05) recovered (113 ± 12 vs. 70 ± 6.6 N). It is concluded that multiple sessions of heavy exercise can reverse the fatigue noted early and reduce or eliminate weakness depending on the frequency of stimulation.

scholarly journals Factors Influencing Equity Return Correlations between China’s Pairs of A- and B-Share Markets: Effect of QFII’s Implementation

2017 ◽  
Vol 8 (2) ◽  
pp. 105
Author(s):  
Jung-Lieh Hsiao ◽  
Teng-Tsai Tu ◽  
Mei-Chun Chen
Keyword(s):  
Interest Rate ◽  
Turnover Rate ◽  
Constant Term ◽  
Influential Factors ◽  
Policy Implications ◽  
Return Volatility ◽  
Market Sentiment ◽  
Factors Influencing ◽  
Before And After ◽  
Relative Return

This paper was intended to examine factors influencing the correlations between A- and B-shares of individual firms, and explore the effects of Qualified Foreign Institutional Investor’s (QFII) implementation on correlations. The empirical results show that interest rate differential, relative turnover rate, relative return volatility, and market sentiment had impacts on correlation both before and after the QFII’s implementation. After its implementation, correlations became more sensitive to premium, relative turnover rate and market sentiment. Furthermore, the estimated constant term for overall market correlation became more negative (raw values from -0.3413 to -0.8815), indicating an increasing correlation between A- and B-shares’ returns. The policy implications are that much benefit of diversification into emerging markets such as paired A-and B-shares can be accomplished, together with taking several influential factors into account.

Near-maximal voluntary hyperpnea and ventilatory muscle function

1984 ◽  
Vol 57 (6) ◽  
pp. 1742-1748 ◽  
Author(s):  
T. R. Bai ◽  
B. J. Rabinovitch ◽  
R. L. Pardy
Keyword(s):  
Muscle Function ◽  
Low Frequency ◽  
Normal Subjects ◽  
Pressure Time ◽  
Before And After ◽  
Expiratory Muscles ◽  
Four Levels ◽  
Frequency Relationship ◽  
Low Frequency Power ◽  
Relationship Of

Because of its potential relevance to heavy exercise we studied the ventilatory muscle function of five normal subjects before, during, and after shortterm near-maximal voluntary normocapnic hyperpnea. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made at four levels of ventilation: 76, 79, and 86% maximal voluntary ventilation (MVV) and at MVV. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made. The pressure-stimulation frequency relationship of the diaphragm obtained by unilateral transcutaneous phrenic nerve stimulation was studied in two subjects before and after hyperpnea. Decreases in maximal inspiratory (PImax) and transdiaphragmatic (Pdimax) strength were recorded posthyperpnea at 76 and 79% MVV. Decreases in the pressure-frequency curves of the diaphragm and the ratio of high-to-low frequency power of the diaphragm EMG occurred in association with decreases in Pdimax. Analysis of the pressure-time product (P X dt) for the inspiratory and expiratory muscles individually indicated the increasing contribution of expiratory muscle force to the attainment of higher levels of ventilation. Demonstrable ventilatory muscle fatigue may limit endurance at high levels of ventilation.

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