Characteristics of inspiratory inhibition by phasic volume feedback in cats

1978 ◽  
Vol 45 (1) ◽  
pp. 80-86 ◽  
Author(s):  
M. K. Younes ◽  
J. E. Remmers ◽  
J. Baker
Keyword(s):  
Lung Volume ◽  
Time Dependent ◽  
Inspiratory Time ◽  
Reversible Inhibition ◽  
Single Breath ◽  
Inspiratory Phase ◽  
Inspiratory Activity ◽  
The Relationship ◽  
Obvious Relation ◽  
Volume Range

The dependence of phrenic efferent discharge on vagal-volume feedback was examined in barbiturate-anesthetized, paralyzed cats ventilated by a phrenic-driven servo respirator. The characteristics of the respiratory were altered for a single breath, and the resulting change in phrenic activity was quantitated by comparison with phrenic activity without phasic volume feedback. The relation between volume feedback and phrenic inhibition was determined both when inspiratory termination occurred during the rising phase of phrenic discharge and during the plateau observed with barbiturate-induced apneusis. Inhibition of inspiratory activity occurred only when lung volume exceeded a time-dependent threshold. Above this threshold, andextending over a substantial volume range, volume feedback caused graded and reversible inhibition of phrenic discharge. The threshold for graded inhibition declined progressively during the inspiratory phase, showing no obvious relation to the level of inspiratory activity. At any particular time, the relation between volume and phrenic inhibition was convex to the volume axis, and the slope of the relationship increased with inspiratory time. The results indicate that a) volume feedback inhibits inspiration in a graded manner, b) partial inhibition of phrenic activity renders it more susceptible to additional inhibition, and c) inhibitory effectiveness of volume feedback increases with time.

Interactive effects of CO2 and upper airway negative pressure on breathing pattern

1987 ◽  
Vol 63 (1) ◽  
pp. 229-237 ◽  
Author(s):  
E. van Lunteren
Keyword(s):  
Tidal Volume ◽  
Respiratory Rate ◽  
Negative Pressure ◽  
Upper Airway ◽  
Interactive Effects ◽  
Inspiratory Time ◽  
Diaphragm Electrical Activity ◽  
Wide Range ◽  
Inspiratory Activity ◽  
The Relationship

The interactive effects of upper airway negative pressure and hypercapnia on the pattern of breathing were assessed in pentobarbital-anesthetized cats. At any given level of pressure in the upper airway, hypercapnia increased respiratory rate, reduced inspiratory time, and augmented tidal volume, inspiratory airflow, and the peak and rate of rise of diaphragm electrical activity. Conversely, at any given level of CO2, upper airway negative pressure decreased respiratory rate, prolonged inspiratory time, and depressed inspiratory airflow and diaphragm electromyogram (EMG) rate of rise. Application of negative pressure to the upper airway shifted the relationship between tidal volume and inspiratory time upward and rightward. The relationship between inspiratory and expiratory times, however, was linearly correlated over a wide range of chemical drives and levels of upper airway pressure. These results suggest that in the anesthetized cat upper airway negative pressure afferent inputs 1) interact in an additive fashion with hypercapnia to alter the pattern of breathing, 2) interact multiplicatively with CO2 to influence mean inspiratory airflow and diaphragm EMG rate of rise, 3) depress the generation of central inspiratory activity, 4) increase the time-dependent volume threshold for inspiratory termination, and 5) affect the ratio between inspiratory and expiratory times in a similar manner as alterations in PCO2.

scholarly journals Volume-timing relationships during cough and resistive loading in the cat

2000 ◽  
Vol 89 (2) ◽  
pp. 785-790 ◽  
Author(s):  
Donald C. Bolser ◽  
Paul W. Davenport
Keyword(s):  
Linear Relationship ◽  
Negative Slope ◽  
Inspiratory Time ◽  
Positive Slope ◽  
Single Breath ◽  
Resistive Loading ◽  
Resistive Loads ◽  
The Relationship ◽  
Pattern Regulation ◽  
Pulmonary Volume

The relationship between pulmonary volume-related feedback and inspiratory (CTi) and expiratory (CTe) phase durations during cough was determined. Cough was produced in anesthetized cats by mechanical stimulation of the intrathoracic tracheal lumen. During eupnea, the animals were exposed to single-breath inspiratory and expiratory resistive loads. Cough was associated with large increases in inspiratory volume (Vi) and expiratory volume (Ve) but no change in phase durations compared with eupnea. There was no relationship between Viand CTi during coughing. A linear relationship with a negative slope existed between Vi and eupneic inspiratory time during control and inspiratory resistive loading trials. There was no relationship between Ve and CTe during all coughs. However, when the first cough in a series or a single cough was analyzed, the Ve/CTe relationship had a positive slope. A linear relationship with a negative slope existed between Ve and eupneic expiratory time during control and expiratory resistive loading trials. These results support separate ventilatory pattern regulation during cough that does not include modulation of phase durations by pulmonary volume-related feedback.

Effect of lung volume on ventilation distribution

1989 ◽  
Vol 66 (6) ◽  
pp. 2502-2510 ◽  
Author(s):  
A. B. Crawford ◽  
D. J. Cotton ◽  
M. Paiva ◽  
L. A. Engel
Keyword(s):  
Lung Volume ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mixing Efficiency ◽  
Ventilation Distribution ◽  
Single Breath ◽  
Wide Range ◽  
Residual Capacity ◽  
Phase Iii Slope ◽  
Volume Range

To examine the effect of preinspiratory lung volume (PILV) on ventilation distribution, we performed multiple-breath N2 washouts (MBNW) in seven normal subjects breathing 1-liter tidal volumes over a wide range of PILV above closing capacity. We measured the following two independent indexes of ventilation distribution from the MBNW: 1) the normalized phase III slope of the final breaths of the washout (Snf) and 2) the alveolar mixing efficiency during that portion of the washout where 80–90% of the lung N2 had been cleared. Three of the subjects also performed single-breath N2 washouts (SBNW) by inspiring 1-liter breaths and expiring to residual volume at PILV = functional residual capacity (FRC), FRC + 1.0, and FRC - 0.5, respectively. From the SBNW we measured the phase III slope over the expired volume ranges of 0.75–1.0, 1.0–1.6, and 1.6–2.2 liters (S0.75, S1.0, and S1.6, respectively). Between a PILV of 0.92 +/- 0.09 (SE) liter above FRC and a PILV of 1.17 +/- 0.43 liter below FRC, Snf decreased by 61% (P less than 0.001) and alveolar mixing efficiency increased from 80 to 85% (P = 0.05). In addition, Snf and alveolar mixing efficiency were negatively correlated (r = 0.74). In contrast, over a similar volume range, S1.0 and S1.6 were greater at lower PILV. We conclude that, during tidal breathing in normal subjects, ventilation distribution becomes progressively more inhomogeneous at higher lung volumes over a range of volumes above closing capacity.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional ventilation in excised lobes exposed to a transpulmonary pressure gradient

1988 ◽  
Vol 64 (2) ◽  
pp. 771-780 ◽  
Author(s):  
D. O. Warner ◽  
R. E. Hyatt ◽  
K. Rehder
Keyword(s):  
Pressure Gradient ◽  
Lung Volume ◽  
Inflection Point ◽  
Transpulmonary Pressure ◽  
Accurate Estimate ◽  
Airway Closure ◽  
Single Breath ◽  
Lower Lung ◽  
The Relationship ◽  
Phase Iv

We performed the quasi-static single-breath oxygen test (SBO2) in 16 excised canine lower lung lobes while the lobes were first suspended in air and then later immersed in stable foams that provided a vertical transpulmonary pressure gradient. In lobes suspended in air, an approximately linear alveolar plateau (AP) was obtained. The AP during foam immersion was markedly curvilinear, with phase IV seen at end expiration. The observed AP during foam immersion could be predicted by a mathematical model that assumed a homogeneous transpulmonary pressure-regional volume relationship equal to the overall pressure-volume (PV) relationship measured with the lobe suspended in air. The accuracy of this model was further confirmed by measuring the washout of nitrogen injected into different lung regions through alveolar capsules. We also used the model to examine the relationship between the onset of dependent airway closure and two of its proposed indicators: the onset of phase IV and the inflection point of the overall PV relationship. In most lobes, the lung volume at the onset of phase IV was less than the modeled lung volume at dependent airway closure. The lung volume at the inflection point was always less than the modeled lung volume at dependent airway closure. We show that the overall PV relationship measured in lobes suspended in air provides an accurate estimate of regional PV relationships during foam immersion.

Plasminogen Depletion during Streptokinase Treatment or Two-Chain Urokinase Incubation Correlates with Decreased Clot Lysability Ex Vivo and In Vitro

1993 ◽  
Vol 70 (06) ◽  
pp. 0998-1004 ◽  
Author(s):  
Páll T Önundarson ◽  
H Magnús Haraldsson ◽  
Lena Bergmann ◽  
Charles W Francis ◽  
Victor J Marder
Keyword(s):  
Myocardial Infarction ◽  
Ex Vivo ◽  
Time Dependent ◽  
State Variables ◽  
Thrombolytic Treatment ◽  
Direct Proportion ◽  
Plasmin Activity ◽  
Plasma Exposure ◽  
The Relationship

SummaryThe relationship between lytic state variables and ex vivo clot lysability was investigated in blood drawn from patients during streptokinase administration for acute myocardial infarction. A lytic state was already evident after 5 min of treatment and after 20 min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen 0.2 g/1. Lysis of radiolabeled retracted clots in the patient plasmas decreased from 37 ± 8% after 5 min to 21 ± 8% at 10 min and was significantly lower (8 ± 9%, p <0.005) in samples drawn at 20, 40 and 80 min. Clot lysability correlated positively with the plasminogen concentration (r = 0.78, p = 0.003), but not with plasmin activity. Suspension of radiolabeled clots in normal plasma pre-exposed to 250 U/ml two-chain urokinase for varying time to induce an in vitro lytic state was also associated with decreasing clot lysability in direct proportion with the duration of prior plasma exposure to urokinase. The decreased lysability correlated with the time-dependent reduction in plasminogen concentration (r = 0.88, p <0.0005). Thus, clot lysability decreases in conjunction with the development of the lytic state and the associated plasminogen depletion. The lytic state may therefore limit reperfusion during thrombolytic treatment.

Rib cage and abdominal restrictions have different effects on lung mechanics

1980 ◽  
Vol 49 (6) ◽  
pp. 946-952 ◽  
Author(s):  
C. A. Bradley ◽  
N. R. Anthonisen
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Lung Mechanics ◽  
Elastic Recoil ◽  
Rib Cage ◽  
Lung Capacity ◽  
Single Breath ◽  
Restrictive Procedures ◽  
Maximum Expiratory Flow ◽  
Per Se

The effects of a variety of restrictive procedures on lung mechanics were studied in eight healthy subjects. Rib cage restriction decreased total lung capacity (TLC) by 43% and significantly increased elastic recoil and maximum expiratory flow (MEF). Subsequent immersion of four subjects with rib cage restriction resulted in no further change in either parameter; shifts of blood volume did not reverse recoil changes during rib cage restriction. Abdominal restriction decreased TLC by 40% and increased MEF and elastic recoil, but recoil was increased significantly less than was the case with rib cage restriction. Further, at a given recoil pressure, MEF was less during rib cage restriction than during either abdominal restriction or no restriction. Measurements of the unevenness of inspired gas distribution by the single-breath nitrogen technique showed increased unevenness during rib cage restriction, which was significantly greater than that during abdominal restriction. We conclude that lung volume restriction induces changes in lung function, but the nature of these changes depends on how the restriction is applied and therefore cannot be ascribed to low lung volume breathing per se.

A model for the relation between respiratory neural and mechanical outputs. III. Validation

1981 ◽  
Vol 51 (4) ◽  
pp. 990-1001 ◽  
Author(s):  
M. Younes ◽  
W. Riddle ◽  
J. Polacheck
Keyword(s):  
Respiratory System ◽  
Pressure Wave ◽  
Time Course ◽  
Present Report ◽  
Occlusion Pressure ◽  
Single Breath ◽  
Wave Forms ◽  
Inspiratory Activity ◽  
Good Agreement

In the preceding two communications we described a model for the relation between respiratory neural and mechanical outputs. In the present report we test the accuracy of the model in predicting volume and flow from occlusion pressure wave forms, and vice versa. We performed single-breath airway occlusions in 21 unconscious subjects and determined the time course of occlusion pressure. We also measured the passive properties of the respiratory system. The time course of volume and flow was predicted from the occlusion pressure wave forms, and the results were compared with the spontaneous breaths immediately preceding occlusion. Inspiratory duration, shape and amplitude of occlusion-pressure wave forms, and the passive properties of the respiratory system varied widely among subjects. There was good agreement between predicted and observed values in all cases. Except for some prolongation of inspiration (Hering-Breuer reflex), diaphragmatic activity did not change during occlusion. Since occlusion pressure is proportional to inspiratory activity, we conclude that the model described provides a good approximation of the relation between inspiratory activity and spirometric output.

The Relationship between Lung Volume and Standard Scalar ECG Parameters in Normal Subjects

CHEST Journal ◽  
1989 ◽  
Vol 95 (3) ◽  
pp. 530-534
Author(s):  
John D. Parker ◽  
John E. Fay ◽  
F. James Brennan ◽  
Lutz Forkert
Keyword(s):  
Lung Volume ◽  
Normal Subjects ◽  
The Relationship

Coordination between rib cage muscles and diaphragm during quiet breathing in humans

1984 ◽  
Vol 57 (3) ◽  
pp. 899-906 ◽  
Author(s):  
A. De Troyer ◽  
M. Estenne
Keyword(s):  
Tidal Volume ◽  
Marked Reduction ◽  
Emg Activity ◽  
Quiet Breathing ◽  
Rib Cage ◽  
Intercostal Muscles ◽  
Inspiratory Activity ◽  
Normal Humans ◽  
Volume Range

The pattern of activation of the scalenes and the parasternal intercostal muscles was studied in relation to the pattern of rib cage and abdominal motion during various respiratory maneuvers in the tidal volume range in five normal humans. Electromyograms (EMG) of the scalenes and parasternal intercostals were recorded with bipolar needle electrodes, and changes in abdominal and rib cage displacement were measured using linearized magnetometers. The scalenes and parasternal intercostals were always active during quiet breathing, and their pattern of activation was identical; in both muscles the EMG activity usually started together with the beginning of inspiration, increased in intensity as inspiration proceeded, and persisted into the early part of expiration. In addition, like the parasternal activity the scalene inspiratory activity persisted until the tidal volume was trivial, increased during tidal inspirations performed with the rib cage alone, and was nearly abolished during diaphragmatic isovolume maneuvers. However, attempts to perform tidal inspiration with the diaphragm alone, while causing an increase in parasternal EMG activity, were associated with a marked reduction or a suppression of scalene EMG activity and a reduced substantially distorted rib cage expansion. In particular, the upper rib cage was then moving paradoxically.(ABSTRACT TRUNCATED AT 250 WORDS)

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