The Rate of Isometric Inspiratory Pressure Development as a Measure of Responsiveness to Carbon Dioxide in Man

1975 ◽  
Vol 49 (1) ◽  
pp. 57-68 ◽  
Author(s):  
A. W. Matthews ◽  
J. B. L. Howell
Keyword(s):  
Initial Rate ◽  
Ventilatory Response ◽  
Pressure Change ◽  
Normal Subjects ◽  
Inspiratory Pressure ◽  
Pulmonary Mechanics ◽  
Inspiratory Muscles ◽  
Pressure Development ◽  
Respiratory Centre ◽  
Very High

1. A technique has been developed for assessing CO2 responsiveness by measuring the maximum rate of isometric inspiratory pressure change at the mouth [(dP/dt)max.]. 2. By use of a rebreathing technique, the (dP/dt)max. response to CO2 was shown to correlate well with the ventilatory response in thirty-two normal subjects. 3. The addition of an external flow resistance sufficient to reduce the ventilatory response by a mean of 33.4% produced no significant mean change in the (dP/dt)max. response in thirty subjects. 4. In six patients recovering from bronchial asthma, reduction of airways obstruction led to a mean increase in the ventilatory response of 109% without any significant mean change in the (dP/dt)max. response. 5. An increase in lung volume did not reduce the (dP/dt)max. response in five normal subjects. 6. At very high lung volumes, six normal subjects were able to develop a higher (dP/dt)max. during voluntary inspiratory efforts than has been recorded during spontaneous breathing response to CO2. 7. It is believed that (dP/dt)max. represents the initial rate of development of force by the inspiratory muscles before this can be modified by mechanical loading, proprioceptive feedback mechanisms or conscious response and can therefore be used to study changes in the motor output of the respiratory centre in response to ventilatory stimuli independently of pulmonary mechanics.

Assessment of Responsiveness to Carbon Dioxide in Patients with Chronic Airways Obstruction by Rate of Isometric Inspiratory Pressure Development

1976 ◽  
Vol 50 (3) ◽  
pp. 199-205 ◽  
Author(s):  
A. W. Matthews ◽  
J. B. L. Howell
Keyword(s):  
Carbon Dioxide ◽  
Ventilatory Response ◽  
Pressure Change ◽  
Significant Negative Correlation ◽  
Inspiratory Pressure ◽  
Normal Range ◽  
Ventilatory Responses ◽  
Airways Obstruction ◽  
Pressure Development ◽  
Mechanical Factors

1. Responsiveness to CO2 was measured in forty patients with chronic airways obstruction in terms of ventilation and rate of isometric inspiratory pressure change [(dP/dt)max.]. 2. The ventilatory response was below the normal range in eighteen out of twenty-two patients with normal arterial CO2 tensions and in all of eighteen patients with CO2 retention. 3. The (dP/dt)max. response was distributed throughout the normal range in all but one of the patients with normal arterial CO2 tension. In all the patients with CO2 retention the (dP/dt)max. response was either at or below the lower limit of the normal range. 4. Although the ventilatory responses correlated significantly with FEV1 there was no such correlation for the (dP/dt)max. responses. 5. The (dP/dt)max. response showed a significant negative correlation with Pa,co2. 6. It is believed that the (dP/dt)max. response to CO2 can be used to assess central CO2 responsiveness in subjects with airways obstruction independently of mechanical factors limiting their ventilation.

Role of Impaired Inspiratory Muscle Function in Limiting the Ventilatory Response to Carbon Dioxide in Chronic Airflow Obstruction

1983 ◽  
Vol 64 (5) ◽  
pp. 487-495 ◽  
Author(s):  
H. R. Gribbin ◽  
I. T. Gardiner ◽  
G. J. Heinz ◽  
G. J. Gibson ◽  
N. B. Pride
Keyword(s):  
Muscle Activation ◽  
Ventilatory Response ◽  
Work Of Breathing ◽  
Airflow Obstruction ◽  
Normal Subjects ◽  
Inspiratory Muscle ◽  
Pleural Pressure ◽  
Pulmonary Mechanics ◽  
Respiratory Drive ◽  
Inspiratory Muscles

1. Twenty patients with severe chronic airflow obstruction (CAFO), four of whom were hypercapnic, had greatly reduced ventilatory responses to rebreathing CO2 under hyperoxic conditions, compared with the responses in normal subjects. 2. Mouth occlusion pressure (P0.1) responses to CO2 were also reduced in the patients compared with those of normal subjects but the reduction was less severe than in the ventilatory response. 3. in ten patients with CAFO minimum pleural pressure during tidal breathing [Ppl min. (dynamic)] at a Pco2 of 8.0 kPa was only slightly less negative than in the normal subjects (−16.2 cm water vs −23.4 cm water). 4. During rebreathing end-expiratory volume (EEV) fell progressively in the normal subjects (mean fall = 800 ml); in the patients there was a progressive rise in EEV (mean rise = 390 ml). 5. When Ppl min. (dynamic) was compared with minimum static pleural pressures at the same lung volume the patients were generating a much higher proportion of their available static pressure (47.0%) than the normal subjects (26.4%) at a Pco2 of 8.0 kPa, suggesting that despite the slightly less negative Ppl min. (dynamic), inspiratory muscle activation was greater in the patients than in normal subjects. Similar conclusions were reached from an analysis of the inspiratory work of breathing. 6. We conclude that hyperinflation, by impairing the capacity of the inspiratory muscles to lower pleural pressure, reduces the ventilatory response to CO2 and adds to the effects of abnormalities in pulmonary mechanics so that measurements of absolute pleural pressure or work of breathing underestimate inspiratory muscle activation in patients with severe CAFO. 7. Hyperinflation and severe airflow obstruction also reduce the change in P0.1 for a given degree of inspiratory muscle activation. 8. Our results suggest that, despite the impaired pressure and ventilatory response to rebreathing CO2 in the patients, their central respiratory drive was greater than that of the normal subjects.

scholarly journals Effects of diaphragmatic control on multiparametric analysis of the sniff nasal inspiratory pressure test and inspiratory muscle activity in healthy subjects

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253132
Author(s):  
Kadja Benício ◽  
Vanessa R. Resqueti ◽  
Fernando A. L. Dias ◽  
Francesca Pennati ◽  
Andrea Aliverti ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Relaxation Rate ◽  
Muscle Activity ◽  
Healthy Subjects ◽  
Contractile Properties ◽  
Inspiratory Pressure ◽  
Diaphragm Muscle ◽  
Inspiratory Muscles ◽  
Pressure Test ◽  
Pressure Development

Background We investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate, contractile properties and electrical activity of the inspiratory muscles of healthy subjects. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively. Methods Twenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values were used for analysis. Results The maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01), contraction times (CT) (p = 0.02) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles. In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes. Conclusion The diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change force velocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.

Sex and age differences in pulmonary mechanics in normal nonsmoking subjects

1976 ◽  
Vol 41 (1) ◽  
pp. 20-25 ◽  
Author(s):  
G. J. Gibson ◽  
N. B. Pride ◽  
C. O'cain ◽  
R. Quagliato
Keyword(s):  
Sex Differences ◽  
Elderly Women ◽  
Young Men ◽  
Maximum Flow ◽  
Normal Subjects ◽  
Pulmonary Mechanics ◽  
Elastic Recoil ◽  
Inspiratory Muscles ◽  
Maximum Expiratory Flow ◽  
Effects Of Aging

Maximun flow-volume, static pressure-volume, and maximum flow static recoil curves of three groups of nonsmoking, normal subjects (young men, youngwomen, elderly women) were used to assess age and sex differences in pulmonary mechanics. No significant sex differences in maximum flow were seen butthe young men showed higher lung recoil pressures at full inflation. When the influence of the inspiratory muscles and chest wall was excluded by exponential extrapolation of the pressure-volume curves to a maximum volume thebulk elastic properties of the lungs of young men and women appeared identical. Loss of maximum expiratory flow at low lung volumes and of lung recoilpressure occurred with age in nonsmoking women in whom emphysema should be minimal and therefore indicate true physiological effects of aging. The changes in pulmonary mechanics with age are consistent with an increase in unstressed dimensions and loss of elastic recoil of both alveoli and airways.

Respiratory mechanics and breathing pattern during and following maximal exercise

1984 ◽  
Vol 57 (6) ◽  
pp. 1773-1782 ◽  
Author(s):  
M. Younes ◽  
G. Kivinen
Keyword(s):  
Time Course ◽  
Maximal Exercise ◽  
Dynamic Pressure ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Esophageal Pressure ◽  
Inspiratory Pressure ◽  
Elastic Recoil ◽  
Inspiratory Muscles ◽  
Inspiratory Muscle Fatigue

We looked for evidence of changes in lung elastic recoil and of inspiratory muscle fatigue at maximal exercise in seven normal subjects. Esophageal pressure, flow, and volume were measured during spontaneous breathing at increasing levels of cycle exercise to maximum. Total lung capacity (TLC) was determined at rest and immediately before exercise termination using a N2-washout technique. Maximal inspiratory pressure and inspiratory capacity were measured at 1-min intervals. The time course of instantaneous dynamic pressure of respiratory muscles (Pmus) was calculated for the spontaneous breaths immediately preceding exercise termination. TLC volume and lung elastic recoil at TLC were the same at the end of exercise as at rest. Maximum static inspiratory pressures at exercise termination were not reduced. However, mean Pmus of spontaneous breaths at end exercise exceeded 15% of maximum inspiratory pressure in five of the subjects. We conclude that lung elastic recoil is unchanged even at maximal exercise and that, while inspiratory muscles operate within a potentially fatiguing range, the high levels of ventilation observed during maximal exercise are not maintained for a sufficient time to result in mechanical fatigue.

Inspiratory muscle forces and endurance in maximum resistive loading

1985 ◽  
Vol 58 (5) ◽  
pp. 1608-1615 ◽  
Author(s):  
G. L. Jones ◽  
K. J. Killian ◽  
E. Summers ◽  
N. L. Jones
Keyword(s):  
Peak Inspiratory Pressure ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Inspiratory Pressure ◽  
Endurance Capacity ◽  
Breathing Patterns ◽  
O2 Uptake ◽  
Maximum Resistance ◽  
Inspiratory Muscles ◽  
Resistive Loads

The ability of the respiratory muscles to sustain ventilation against increasing inspiratory resistive loads was measured in 10 normal subjects. All subjects reached a maximum rating of perceived respiratory effort and at maximum resistance showed signs of respiratory failure (CO2 retention, O2 desaturation, and rib cage and abdominal paradox). The maximum resistance achieved varied widely (range 73–660 cmH2O X l-1 X s). The increase in O2 uptake (delta Vo2) associated with loading was linearly related to the integrated mouth pressure (IMP): delta Vo2 = 0.028 X IMP + 19 ml/min (r = 0.88, P less than 0.001). Maximum delta Vo2 was 142 ml/min +/- SD 68 ml/min. There were significant (P less than 0.05) relationships between the maximum voluntary inspiratory pressure against an occluded airway (MIP) and both maximum IMP (r = 0.80) and maximum delta Vo2 (r = 0.76). In five subjects, three imposed breathing patterns were used to examine the effect of different patterns of respiratory muscle force deployment. Increasing inspiratory duration (TI) from 1.5 to 3.0 and 6.0 s, at the same frequency of breathing (5.5 breaths/min) reduced peak inspiratory pressure and increased the maximum resistance tolerated (190, 269, and 366 cmH2O X l-1 X s, respectively) and maximum IMP (2043, 2473, and 2913 cmH2O X s X min-1, but the effect on maximum delta Vo2 was less consistent (166, 237, and 180 ml/min). The ventilatory endurance capacity and the maximum O2 uptake of the respiratory muscles are related to the strength of the inspiratory muscles, but are also modified through the pattern of force deployment.

scholarly journals Effect of expiratory resistive loading on the noninvasive tension-time index in COPD

2000 ◽  
Vol 89 (5) ◽  
pp. 2007-2014 ◽  
Author(s):  
William H. Thompson ◽  
Paula Carvalho ◽  
James P. Souza ◽  
Nirmal B. Charan
Keyword(s):  
Normal Subjects ◽  
Respiratory Cycle ◽  
Inspiratory Pressure ◽  
Occlusion Pressure ◽  
Time Index ◽  
Inspiratory Muscles ◽  
Copd Patients ◽  
Resistive Loading ◽  
Tension Time ◽  
Mouth Occlusion Pressure

Expiratory resistive loading (ERL) is used by chronic obstructive pulmonary disease (COPD) patients to improve respiratory function. We, therefore, used a noninvasive tension-time index of the inspiratory muscles (TTmus =P̄i/Pi max × Ti/Tt, where P̄i is mean inspiratory pressure estimated from the mouth occlusion pressure, Pi max is maximal inspiratory pressure, Ti is inspiratory time, and Tt is total respiratory cycle time) to better define the effect of ERL on COPD patients. To accomplish this, we measured airway pressures, mouth occlusion pressure, respiratory cycle flow rates, and functional residual capacity (FRC) in 14 COPD patients and 10 normal subjects with and without the application of ERL. TTmus was then calculated and found to drop in both COPD and normal subjects ( P < 0.05). The decline in TTmus in both groups resulted solely from a prolongation of expiratory time with ERL ( P < 0.001 for COPD, P < 0.05 for normal subjects). In contrast to the COPD patients, normal subjects had an elevation in P̄i and FRC, thus minimizing the decline in TTmus. In conclusion, ERL reduces the potential for inspiratory muscle fatigue in COPD by reducing Ti/Tt without affecting FRC andP̄i.

Activity of respiratory muscles in upright and recumbent humans

1981 ◽  
Vol 51 (6) ◽  
pp. 1552-1561 ◽  
Author(s):  
W. S. Druz ◽  
J. T. Sharp
Keyword(s):  
Respiratory Muscles ◽  
Pressure Change ◽  
Normal Subjects ◽  
Oblique Muscle ◽  
Upright Posture ◽  
Tonic Activity ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Supine Posture ◽  
Gastric Pressure

It is established that during tidal breathing the rib cage expands more than the abdomen in the upright posture, whereas the reverse is usually true in the supine posture. To explore the reasons for this, we studied nine normal subjects in the supine, standing, and sitting postures, measuring thoracoabdominal movement with magnetometers and respiratory muscle activity via integrated electromyograms. In eight of the subjects, gastric and esophageal pressures and diaphragmatic electromyograms via esophageal electrodes were also measured. In the upright postures, there was generally more phasic and tonic activity in the scalene, sternocleidomastoid, and parasternal intercostal muscles. The diaphragm showed more phasic (but not more tonic) activity in the upright postures, and the abdominal oblique muscle showed more tonic (but not phasic) activity in the standing posture. Relative to the esophageal pressure change with inspiration, the inspiratory gastric pressure change was greater in the upright than in the supine posture. We conclude that the increased rib cage motion characteristic of the upright posture owes to a combination of increased activation of rib cage inspiratory muscles plus greater activation of the diaphragm that, together with a stiffened abdomen, acts to move the rib cage more effectively.

scholarly journals Effects of Diaphragmatic Control on Multiparametric Analysis of the Nasal Inspiratory Pressure Test and Inspiratory Muscle Activity in Healthy Subjects

2020 ◽  
Author(s):  
Kadja Benício ◽  
Vanessa R. Resqueti ◽  
Fernando A. L. Dias ◽  
Francesca Pennati ◽  
Andrea Aliverti ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Relaxation Rate ◽  
Muscle Activity ◽  
Healthy Subjects ◽  
Contractile Properties ◽  
Inspiratory Pressure ◽  
Diaphragm Muscle ◽  
Inspiratory Muscles ◽  
Pressure Test ◽  
Pressure Development

Abstract Background:We investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate and contractile properties, as well as the electrical activity of inspiratory muscles, assessed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively, in healthy subjects. Methods:Twenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values ​​were used for analysis. Results: The maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles; as well as significant longer contraction (CT) times (p = 0.02). In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes. Conclusion:The diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change forcevelocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.

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