Effects of fenoterol on inspiratory effort sensation and fatigue during inspiratory threshold loading

1996 ◽  
Vol 80 (3) ◽  
pp. 727-733 ◽  
Author(s):  
J. Suzuki ◽  
S. Suzuki ◽  
T. Okubo
Keyword(s):  
Low Frequency ◽  
Normal Subjects ◽  
Motor Command ◽  
Inspiratory Effort ◽  
Double Blind ◽  
Endurance Time ◽  
Transdiaphragmatic Pressure ◽  
Mouth Pressure ◽  
Residual Capacity ◽  
Low Frequency Power

We studied the effects of a single dose of fenoterol on the relationship between inspiratory effort sensation (IES) and inspiratory muscle fatigue induced by inspiratory threshold loading in healthy subjects. The magnitude of the threshold was 60% of maximal static inspiratory mouth pressure (PI,mmax) at functional residual capacity, and the duty cycle was 0.5. Subjects continued the threshold loaded breathing until the target mouth pressure could no longer be maintained (endurance time). The intensity of the IES was scored with a modified Borg scale. Either fenoterol (5 mg) or a placebo was given orally 2 h before loading in a randomized double-blind crossover protocol. The endurance time with fenoterol (34.4 +/- 8.6 min) was longer than that with the placebo (22.2 +/- 7.1 min; P < 0.05). The ratio of high- to low-frequency power of the diaphragmatic electromyogram (EMGdi) decreased during loading; the decrease was less with fenoterol (P < 0.05). The EMGdi also decreased with loading; the decrease was greater on fenoterol treatment (P < 0.01). The PI,mmax and maximal transdiaphragmatic pressure (Pdi) were similarly decreased after loading on either treatment. The intensity of the IES rose with time during loading in both groups but was lower with fenoterol than with the placebo (P < 0.05). The ratio of Pdi to integrated activity of the EMGdi increased with fenoterol (P < 0.05). Fenoterol treatment increased both superimposed Pdi twitch and Pdi twitch of relaxed diaphragm and decreased the value of (1-superimposed Pdi twitch/Pdi twitch of relaxed diaphragm). Thus we conclude that in normal subjects fenoterol reduces diaphragmatic fatigue and decreases the motor command to the diaphragm, resulting in a decrease in IES during inspiratory threshold loading and a prolongation of endurance.

Expiratory muscle fatigue in normal subjects

1991 ◽  
Vol 70 (6) ◽  
pp. 2632-2639 ◽  
Author(s):  
S. Suzuki ◽  
J. Suzuki ◽  
T. Okubo
Keyword(s):  
Muscle Fatigue ◽  
Low Frequency ◽  
Normal Subjects ◽  
Work Load ◽  
Emg Activity ◽  
Transdiaphragmatic Pressure ◽  
Expiratory Muscle ◽  
Inspiratory Muscles ◽  
Loaded Breathing ◽  
Low Frequency Power

We examined expiratory muscle fatigue during expiratory resistive loading in 11 normal subjects. Subjects breathed against expiratory resistances at their own breathing frequency and tidal volume until exhaustion or for 60 min. Respiratory muscle strength was assessed from both the maximum static expiratory and inspiratory mouth pressures (PEmax and PImax). At the lowest resistance, PEmax and PImax measured after completion of the expiratory loaded breathing were not different from control values. With higher resistance, both PEmax and PImax were decreased (P less than 0.05), and the decrease lasted for greater than or equal to 60 min. The electromyogram high-to-low frequency power ratio for the rectus abdominis muscle decreased progressively during loading (P less than 0.01), but the integrated EMG activity did not change during recovery. Transdiaphragmatic pressure during loading was increased 3.6-fold compared with control (P less than 0.05). These findings suggest that expiratory resistive loaded breathing induces muscle fatigue in both expiratory and inspiratory muscles. Fatigue of the expiratory muscles can be attributed directly to the high work load and that of the inspiratory muscles may be related to increased work due to shortened inspiratory time.

Electromyogram pattern of diaphragmatic fatigue

1979 ◽  
Vol 46 (1) ◽  
pp. 1-7 ◽  
Author(s):  
D. Gross ◽  
A. Grassino ◽  
W. R. Ross ◽  
P. T. Macklem
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Normal Subjects ◽  
Progressive Increase ◽  
Transdiaphragmatic Pressure ◽  
Diaphragmatic Fatigue ◽  
Inspiratory Resistance ◽  
Residual Capacity ◽  
Emg Power Spectrum ◽  
Pressure Generator

We studied the effect of breathing at various levels of transdiaphragmatic pressure (Pdi) on the EMG power spectrum of the diaphragm. The diaphragmatic EMG was measured simultaneously with a bipolar esophageal electrode (EE) and surface electrode (SE) placed on the ventral portion of the sixth and seventh intercostal spaces in five normal subjects breathing at functional residual capacity (FRC) against an inspiratory resistance. During each fatigue run the subjects generated a Pdi, with each inspiration, that was 25, 50, or 75% of maximum Pdi (Pdimax) for a period up to 15 min. During runs at 50 and 75% of the Pdimax, which are known to produce fatigue, we found for both EE and SE a progressive increase in the amplitude of the low-frequency (L = 20-46.7 Hz) and a decrease in the high-frequency (H = 150-350 Hz) component of the EMG. These changes were not seen at 25% of Pdimax. The diaphragmatic H/L ratio was independent of Pdi when the diaphragm was not fatigued. H/L fell while the diaphragm performed fatiguing work and this was more rapid at higher Pdi's. It was thus concluded that frequency spectrum analysis of the EMG can detect diaphragmatic fatigue reliably, prior to the time when the diaphragm fails as a pressure generator.

Effects of theophylline and enprofylline on diaphragmatic contractility

1987 ◽  
Vol 63 (1) ◽  
pp. 51-57 ◽  
Author(s):  
D. Murciano ◽  
M. Aubier ◽  
N. Viires ◽  
H. Mal ◽  
R. Pariente
Keyword(s):  
Adenosine Receptors ◽  
Normal Subjects ◽  
Underlying Mechanism ◽  
Double Blind ◽  
Transdiaphragmatic Pressure ◽  
Residual Capacity ◽  
Phrenic Nerves ◽  
Blind Crossover Study ◽  
Double Blind Crossover Study ◽  
Cell Membrane Level

Experimental data suggest that theophylline (T) enhances diaphragmatic contractility by increasing the influx of calcium at the cell membrane level through an inhibition of adenosine receptors (Aubier et al., J. Appl. Physiol. 54: 460–4, 1983). Enprofylline (E) is a xanthine drug that has poor ability to antagonize physiological actions of adenosine. The aim of this study was to compare the effects on diaphragmatic contractility of T and E in order to determine whether antagonism of adenosine receptors was the underlying mechanism of the inotropic effect of T on diaphragmatic contractility. Ten normal subjects were studied in the sitting position. The contractile properties of the diaphragm were assessed by measuring the transdiaphragmatic pressure (Pdi) generated at functional residual capacity during bilateral electrical stimulation of the phrenic nerves. The subjects were randomized, and after control measurements were performed, they received T or E. This was a double-blind crossover study, the measurements being repeated with the second drug after one week. Both drugs were administered intravenously with a loading dose of 6 and 2 mg/kg administered in 30 min for T and E and a maintenance dose of 0.9 and 0.075 mg.kg-1 X h-1 for T and E, respectively. Measurements were performed before and 60 min after T or E administration. Plasmatic levels of both drugs were also analyzed. In all the subjects, therapeutic levels of T or E were reached (14.8 +/- 0.6 and 3.9 +/- 0.42 mg/l for T and E, respectively, at 30 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between QT interval variability and muscle sympathetic nerve activity in normal subjects

2015 ◽  
Vol 309 (7) ◽  
pp. H1218-H1224 ◽  
Author(s):  
Fatima El-Hamad ◽  
Elisabeth Lambert ◽  
Derek Abbott ◽  
Mathias Baumert
Keyword(s):  
Supine Position ◽  
Sympathetic Nerve ◽  
Qt Interval ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Low Frequency ◽  
Normal Subjects ◽  
Nerve Activity ◽  
Head Up Tilt ◽  
Low Frequency Power

Beat-to-beat variability of the QT interval (QTV) is sought to provide an indirect noninvasive measure of sympathetic nerve activity, but a formal quantification of this relationship has not been provided. In this study we used power contribution analysis to study the relationship between QTV and muscle sympathetic nerve activity (MSNA). ECG and MSNA were recorded in 10 healthy subjects in the supine position and after 40° head-up tilt. Power spectrum analysis was performed using a linear autoregressive model with two external inputs: heart period (RR interval) variability (RRV) and MSNA. Total and low-frequency power of QTV was decomposed into contributions by RRV, MSNA, and sources independent of RRV and MSNA. Results show that the percentage of MSNA power contribution to QT is very small and does not change with tilt. RRV power contribution to QT power is notable and decreases with tilt, while the greatest percentage of QTV is independent of RRV and MSNA in the supine position and after 40° head-up tilt. In conclusion, beat-to-beat QTV in normal subjects does not appear to be significantly affected by the rhythmic modulations in MSNA following low to moderate orthostatic stimulation. Therefore, MSNA oscillations may not represent a useful surrogate for cardiac sympathetic nerve activity at moderate levels of activation, or, alternatively, sympathetic influences on QTV are complex and not quantifiable with linear shift-invariant autoregressive models.

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.

scholarly journals Effects of umeclidinium/vilanterol on exercise endurance in COPD: a randomised study

2018 ◽  
Vol 4 (1) ◽  
pp. 00073-2017 ◽  
Author(s):  
John H. Riley ◽  
Chris J. Kalberg ◽  
Alison Donald ◽  
David A. Lipson ◽  
Muhammad Shoaib ◽  
...  
Keyword(s):  
Forced Expiratory Volume ◽  
Chronic Obstructive ◽  
Post Dose ◽  
Double Blind ◽  
Endurance Time ◽  
Obstructive Pulmonary Disease ◽  
Once Daily ◽  
Randomised Study ◽  
Residual Capacity ◽  
Exercise Endurance

This multicentre, randomised, double-blind, placebo-controlled, two-period crossover study assessed the effect of umeclidinium/vilanterol (UMEC/VI) on exercise capacity in patients with chronic obstructive pulmonary disease (COPD) using the endurance shuttle walk test (ESWT).Patients were randomised 1:1 to one of two treatment sequences: 1) UMEC/VI 62.5/25 µg followed by placebo or 2) placebo followed by UMEC/VI 62.5/25 µg. Each treatment was taken once daily for 12 weeks. The primary end-point was 3-h post-dose exercise endurance time (EET) at week 12. Secondary end-points included trough forced expiratory volume in 1 s (FEV1) and 3-h post-dose functional residual capacity (FRC), both at week 12. COPD Assessment Test (CAT) score at week 12 was also assessed.UMEC/VI treatment did not result in a statistically significant improvement in EET change from baseline at week 12 versus placebo (p=0.790). However, improvements were observed in trough FEV1 (206 mL, 95% CI 167–246), 3-h post-dose FRC (−346 mL, 95% CI −487 to −204) and CAT score (−1.07 units, 95% CI −2.09 to −0.05) versus placebo at week 12.UMEC/VI did not result in improvements in EET at week 12 versus placebo, despite improvements in measures of lung function, hyperinflation and health status.

Influence of inspiratory flow rate and frequency on O2 cost of resistive breathing in humans

1988 ◽  
Vol 65 (2) ◽  
pp. 760-766 ◽  
Author(s):  
D. S. Dodd ◽  
P. W. Collett ◽  
L. A. Engel
Keyword(s):  
Flow Rate ◽  
Duty Cycle ◽  
Normal Subjects ◽  
Work Rate ◽  
Inspiratory Flow ◽  
Inspiratory Flow Rate ◽  
Contraction Frequency ◽  
Mouth Pressure ◽  
Resistive Breathing ◽  
Residual Capacity

We examined the combined effect of an increase in inspiratory flow rate and frequency on the O2 cost of inspiratory resistive breathing (VO2 resp). In each of three to six pairs of runs we measured VO2 resp in six normal subjects breathing through an inspiratory resistance with a constant tidal volume (VT). One of each pair of runs was performed at an inspiratory muscle contraction frequency of approximately 10/min and the other at approximately 30/min. Inspiratory mouth pressure was 45 +/- 2% (SE) of maximum at the lower contraction frequency and 43 +/- 2% at the higher frequency. Duty cycle (the ratio of contraction time to total cycle time) was constant at 0.51 +/- 0.01. However, during the higher frequency runs, two of every three contractions were against an occluded airway. Because VT and duty cycle were kept constant, mean inspiratory flow rate increased with frequency. Careful selection of appropriate parameters allowed the pairs of runs to be matched both for work rate and pressure-time product. The VO2 resp did not increase, despite approximately threefold increases in both inspiratory flow rate and contraction frequency. On the contrary, there was a trend toward lower values for VO2 resp during the higher frequency runs. Because these were performed at a slightly lower mean lung volume, a second study was designed to measure the VO2 resp of generating the same inspiratory pressure (45% maximum static inspiratory mouth pressure at functional residual capacity) at the same frequency but at two different lung volumes. This was achieved with a negligibly small work rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of thoracoabdominal breathing patterns on inspiratory effort sensation

1987 ◽  
Vol 62 (4) ◽  
pp. 1665-1670 ◽  
Author(s):  
J. W. Fitting ◽  
D. A. Chartrand ◽  
T. D. Bradley ◽  
K. J. Killian ◽  
A. Grassino
Keyword(s):  
Normal Subjects ◽  
Motor Command ◽  
Esophageal Pressure ◽  
Inspiratory Effort ◽  
Breathing Patterns ◽  
Borg Scale ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Main Variable ◽  
Unique Relationship

The respiratory sensations evoked by added inspiratory loads are currently thought to be largely mediated by the activity of the inspiratory muscles. Because of the differences in proprioceptors and in afferent and efferent innervations among the inspiratory muscles, we hypothesized that the sensation evoked by a given load would be different when the motor command is directed mainly to rib cage muscles or mainly to the diaphragm. To test this hypothesis, we studied six normal subjects breathing against several inspiratory resistances while emphasizing the use of rib cage muscles, or the diaphragm, or a combination of both. At the end of 10 loaded breaths the subjects rated the perceived magnitude of inspiratory effort on a Borg scale. A linear and unique relationship (r = 0.96 +/- 0.02; P less than 0.001) was found between the sensation and esophageal pressure (Pes) in the three thoracoabdominal breathing patterns. We conclude that the level of Pes, whether generated mainly by the rib cage muscles or the diaphragm, is the main variable related to the sensation of inspiratory effort under external inspiratory loads.

Assessment of transdiaphragmatic pressure in humans

1985 ◽  
Vol 58 (5) ◽  
pp. 1469-1476 ◽  
Author(s):  
D. Laporta ◽  
A. Grassino
Keyword(s):  
Pulmonary Disease ◽  
Visual Feedback ◽  
Random Order ◽  
Normal Subjects ◽  
Chronic Obstructive ◽  
Disease Group ◽  
Obstructive Pulmonary Disease ◽  
Transdiaphragmatic Pressure ◽  
Residual Capacity ◽  
Group 1

Maximal force developed by the diaphragm at functional residual capacity is a useful index to establish muscle weakness; however, great disparity in its reproducibility can be observed among reports in the literature. We evaluated five maneuvers to measure maximal transdiaphragmatic pressure (Pdimax) in order to establish best reproducibility and value. Thirty-five naive subjects, including 10 normal subjects (group 1), 12 patients with chronic obstructive pulmonary disease (group 2), and 13 patients with restrictive pulmonary disease (group 3), were studied. Each subject performed five separate maneuvers in random order that were repeated until reproducible values were obtained. The maneuvers were Mueller with (A) and without mouthpiece (B), abdominal expulsive effort with open glottis (C), two-step (maneuver C combined with Mueller effort) (D), and feedback [two-step with visual feedback of pleural (Ppl) and abdominal (Pab) pressure] (E). The greatest reproducible Pdimax values were obtained with maneuver E (P less than 0.01) (group 1: 180 +/- 14 cmH2O). The second best maneuvers were A, B, and D (group 1: 154 +/- 25 cmH2O). Maneuver C produced the lowest values. For all maneuvers, group 1 produced higher values than groups 2 and 3 (P less than 0.001), which were similar. The Ppl to Pdi ratio was 0.6 in maneuvers A and B, 0.4 in D and E, and 0.2 in C. We conclude that visual feedback of Ppl and Pab helped the subjects to elicit maximal diaphragmatic effort in a reproducible fashion. It is likely that the great variability of values in Pdimax previously reported are the result of inadequate techniques.

Effect of abdominal compression on maximum transdiaphragmatic pressure

1990 ◽  
Vol 68 (6) ◽  
pp. 2296-2304 ◽  
Author(s):  
D. R. Hillman ◽  
J. Markos ◽  
K. E. Finucane
Keyword(s):  
Applied Pressure ◽  
Abdominal Muscle ◽  
Inspiratory Effort ◽  
Neural Activation ◽  
Abdominal Compression ◽  
External Compression ◽  
Transdiaphragmatic Pressure ◽  
Trained Subjects ◽  
Maximum Effort ◽  
Residual Capacity

Transdiaphragmatic pressure (Pdi) is lower during maximum inspiratory effort with the diaphragm alone than when maximum inspiratory and expulsive efforts are combined. The increase in Pdi with expulsive effort has been attributed to increased neural activation of the diaphragm. Alternatively, the increase could be due to stretching of the contracted diaphragm. If this were so, Pdi measured during a combined maximum effort would overestimate the capacity of the diaphragm to generate inspiratory force. This study determined the likely contribution of stretching of the contracted diaphragm to estimates of maximum Pdi (Pdimax) obtained during combined inspiratory and expulsive effort. Three healthy trained subjects were studied standing. Diaphragmatic Mueller maneuvers were performed at functional residual capacity and sustained during subsequent abdominal compression by either abdominal muscle expulsive effort or externally applied pressure. Measurements were made of changes in abdominal (Pab) and pleural (Ppl) pressure, Pdi, rib cage and abdominal dimensions and respiratory electromyograms. Three reproducible performances of each maneuver from each subject were analyzed. When expulsive effort was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 86 +/- 12 to 148 +/- 14 (SD) cmH2O within the 1st s and was 128 +/- 14 cmH2O 2 s later. When external compression was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 87 +/- 16 to 171 +/- 19 cmH2O within the 1st s and was 152 +/- 16 cmH2O 2 s later.(ABSTRACT TRUNCATED AT 250 WORDS)

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