Effect of negative-pressure breathing on lung mechanics and venous admixture

1964 ◽  
Vol 19 (4) ◽  
pp. 665-671 ◽  
Author(s):  
Tulio Velasquez ◽  
Leon E. Farhi
Keyword(s):  
Negative Pressure ◽  
Lung Compliance ◽  
Lung Mechanics ◽  
Positive Pressure ◽  
Venous Admixture ◽  
Respiratory Compliance ◽  
Anesthetized Dogs ◽  
Flow Through ◽  
Negative Pressure Breathing ◽  
Opening And Closing

Anesthetized dogs in the supine position show a spontaneous decrease in total respiratory compliance and an increase in venous admixture to the pulmonary circulation. Both these changes can be increased by negative-pressure breathing and reversed by positive-pressure breathing. If the changes in total respiratory compliance are due only to changes in lung compliance and these in turn result directly from the closure of alveoli, the relationship between compliance and inspiratory and expiratory pressure allows one to determine the scatter of opening and closing pressures in the alveoli. The venous admixture measures blood flow through collapsed alveoli, and its relationship to the negative pressure applied indicates the perfusion of the alveoli collapsing with each increment in negative pressure. By studying simultaneously changes in compliance and venous admixture, and using two basic assumptions, the dog's lungs can be described as a system composed of some elements receiving nearly 50% of the ventilation and 20% of the perfusion, relatively unstable mechanically, and having a very high Va/ Q ratio, while the remaining air spaces receive the same ventilation, but 80% of the perfusion. lung compliance; atelectasis; ventilation-perfusion ratio Submitted on October 28, 1963

Lung volumes, lung compliance and airway resistance during negative-pressure breathing

1960 ◽  
Vol 15 (4) ◽  
pp. 554-556 ◽  
Author(s):  
E. Y. Ting ◽  
S. K. Hong ◽  
H. Rahn
Keyword(s):  
Negative Pressure ◽  
Airway Resistance ◽  
Lung Compliance ◽  
Positive Pressure ◽  
Lung Volumes ◽  
Volume Curve ◽  
Supine Posture ◽  
Pressure Volume Curve ◽  
Esophageal Balloon ◽  
Negative Pressure Breathing

Lung volumes, airflow resistance and lung elastance were measured in seven subjects during various degrees of continuous negative-pressure breathing in the supine posture. At –30 cm H2O the expiratory reserve is reduced to about 30% of its normal value and the resistance to airflow is more than doubled. On the other hand, the pressure-volume curve of the lung measured with the aid of an esophageal balloon was not significantly altered by either negative-pressure or positive-pressure breathing. Submitted on February 8, 1960

Factors Influencing Alveolar-Arterial Oxygen Pressure Gradient

1956 ◽  
Vol 186 (3) ◽  
pp. 501-504 ◽  
Author(s):  
Robert J. Atwell ◽  
Joseph F. Tomashefski ◽  
Joseph M. Ryan
Keyword(s):  
Pressure Gradient ◽  
Oxygen Pressure ◽  
Negative Pressure ◽  
Pulmonary Ventilation ◽  
Arterial Oxygen ◽  
Venous Admixture ◽  
Factors Influencing ◽  
Anesthetized Dogs ◽  
Negative Pressure Breathing ◽  
Alveolar Oxygen

The A-a oxygen pressure gradient was determined in anesthetized dogs. Data obtained when pulmonary ventilation and alveolar oxygen tension are varied independently suggests that: a) the magnitude of the A-a oxygen pressure gradient correlates directly with the Paoo2. b) In the anesthetized dog venous admixture seems to be constant, unrelated to the changes in ventilation produced by positive-negative pressure breathing. c) Venous admixture is the most important factor in producing the A-a gradient in the dog.

Effect of continuous pressure breathing on right ventricular volumes

1967 ◽  
Vol 22 (6) ◽  
pp. 1053-1060 ◽  
Author(s):  
Maylene Wong ◽  
Edgardo E. Escobar ◽  
Gilberto Martinez ◽  
John Butler ◽  
Elliot Rapaport
Keyword(s):  
Right Ventricular ◽  
Negative Pressure ◽  
Atmospheric Pressure ◽  
Diastolic Pressure ◽  
Venous Pressure ◽  
Intrathoracic Pressure ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
End Diastolic Volume ◽  
Negative Pressure Breathing

We measured the end-diastolic volume (EDV) and stroke volume (SV) in the right ventricle of anesthetized dogs during continuous pressure breathing and compared them to measurements taken during breathing at atmospheric pressure. During intratracheal positive-pressure breathing, EDV, and SV decreased and end-diastolic pressure became more positive relative to atmospheric pressure. During intratracheal negative-pressure breathing, EDV enlarged and SV tended to increase; end-diastolic pressure became more negative. During extrathoracic negative-pressure breathing SV decreased, EDV fell, though not significantly, and end-diastolic pressure rose, but insignificantly. Changes in EDV observed during intratracheal positive-pressure breathing and intratracheal negative-pressure breathing were associated with minor shifts in transmural pressure (end-diastolic pressure minus intrapleural pressure) in the expected directions, but during extrathoracic negative-pressure breathing a large increase in transmural pressure took place with the nonsignificant reduction in EDV. We believe that intrathoracic pressure influences right ventricular filling by changing the peripheral-to-central venous pressure gradient. The cause of the alteration in diastolic ventricular distensibility demonstrated during extra-thoracic negative-pressure breathing remains unexplained. positive-pressure breathing; negative-pressure breathing; extrathoracic negative-pressure breathing Submitted on August 16, 1966

Cardiopulmonary effects of continuous pressure breathing in hypothermic dogs

1965 ◽  
Vol 20 (4) ◽  
pp. 669-674 ◽  
Author(s):  
J. Salzano ◽  
F. G. Hall
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Stroke Volume ◽  
Negative Pressure ◽  
Alveolar Ventilation ◽  
Positive Pressure ◽  
Negative Pressure Breathing ◽  
Continuous Positive Pressure ◽  
Respiratory Dead Space

Continuous pressure breathing was studied in hypothermic anesthetized dogs. Alveolar ventilation decreased during continuous positive-pressure breathing and increased during continuous negative-pressure breathing. The changes in alveolar ventilation were due to changes in respiratory rate as well as in respiratory dead space. Cardiac output fell significantly during continuous positive-pressure breathing due to a reduction in heart rate and stroke volume. During continuous negative-pressure breathing cardiac output was only slightly greater than during control as a result of a fall in heart rate and an increase in stroke volume. Oxygen consumption was reduced to 60% of control during continuous positive-pressure breathing of 16 cm H2O but was 25% greater than control during continuous negative-pressure breathing. Qualitatively, CO2 production changed as did O2 consumption but was different quantitatively during continuous negative-pressure breathing indicating hyperventilation due to increased respiratory rate. Mean pulmonary artery pressures and pulmonary resistance varied directly with the applied intratracheal pressure. The results indicate that the hypothermic animal can tolerate an imposed stress such as continuous pressure breathing and can increase its oxygen consumption during continuous negative-pressure breathing as does the normothermic animal. hypothermia; respiratory dead space; metabolic rate; cardiac output Submitted on December 8, 1964

Effect of increases in lung volume on clearance of aerosolized solute from human lungs

1985 ◽  
Vol 59 (4) ◽  
pp. 1242-1248 ◽  
Author(s):  
J. D. Marks ◽  
J. M. Luce ◽  
N. M. Lazar ◽  
J. N. Wu ◽  
A. Lipavsky ◽  
...  
Keyword(s):  
Lung Volume ◽  
Negative Pressure ◽  
Ambient Pressure ◽  
Pressure Control ◽  
Positive Pressure ◽  
Healthy Humans ◽  
Human Lungs ◽  
Solute Uptake ◽  
Residual Capacity ◽  
Negative Pressure Breathing

To study the effect of increases in lung volume on solute uptake, we measured clearance of 99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosol (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure [12 cmH2O continuous positive airway pressure (CPAP)] or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH2O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH2O; clearance and FRC were determined at CPAP of 12 cmH2O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method.

scholarly journals Lung mechanical and vascular changes during positive- and negative-pressure lung inflations: importance of reference pressures in the pulmonary vasculature

2009 ◽  
Vol 106 (3) ◽  
pp. 935-942 ◽  
Author(s):  
Ferenc Peták ◽  
Gergely Albu ◽  
Enikö Lele ◽  
Zoltán Hantos ◽  
Denis R. Morel ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Time Windows ◽  
Low Frequency ◽  
Lung Mechanics ◽  
Pulmonary Vasculature ◽  
Positive Pressure ◽  
Vascular Changes ◽  
Inflation Pressure ◽  
Lung Inflation ◽  
Impedance Data

The continuous changes in lung mechanics were related to those in pulmonary vascular resistance (Rv) during lung inflations to clarify the mechanical changes in the bronchoalveolar system and the pulmonary vasculature. Rv and low-frequency lung impedance data (Zl) were measured continuously in isolated, perfused rat lungs during 2-min inflation-deflation maneuvers between transpulmonary pressures of 2.5 and 22 cmH2O, both by applying positive pressure at the trachea and by generating negative pressure around the lungs in a closed box. Zl was averaged and evaluated for 2-s time windows; airway resistance (Raw), parenchymal damping and elastance (H) were determined in each window. Lung inflation with positive and negative pressures led to very similar changes in lung mechanics, with maximum decreases in Raw [−68 ± 4 (SE) vs. −64 ± 18%] and maximum increases in H (379 ± 36 vs. 348 ± 37%). Rv, however, increased with positive inflation pressure (15 ± 1%), whereas it exhibited mild decreases during negative-pressure expansions (−3 ± 0.3%). These results demonstrate that pulmonary mechanical changes are not affected by the opposing modes of lung inflations and confirm the importance of relating the pulmonary vascular pressures in interpreting changes in Rv.

scholarly journals Effects of Various Modes of Mechanical Ventilation in Normal Rats

2014 ◽  
Vol 120 (4) ◽  
pp. 943-950 ◽  
Author(s):  
Matteo Pecchiari ◽  
Ario Monaco ◽  
Antonia Koutsoukou ◽  
Patrizia Della Valle ◽  
Guendalina Gentile ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Lung Injury ◽  
Inflammatory Response ◽  
Negative Pressure ◽  
Positive Pressure Ventilation ◽  
Lung Mechanics ◽  
Whole Body ◽  
Positive Pressure ◽  
Negative Pressure Ventilation ◽  
Cytokine Levels

Abstract Background: Recent studies in healthy mice and rats have reported that positive pressure ventilation delivered with physiological tidal volumes at normal end-expiratory volume worsens lung mechanics and induces cytokine release, thus suggesting that detrimental effects are due to positive pressure ventilation per se. The aim of this study in healthy animals is to assess whether these adverse outcomes depend on the mode of mechanical ventilation. Methods: Rats were subjected to 4 h of spontaneous, positive pressure, and whole-body or thorax-only negative pressure ventilation (N = 8 per group). In all instances the ventilatory pattern was that of spontaneous breathing. Lung mechanics, cytokines concentration in serum and broncho–alveolar lavage fluid, lung wet-to-dry ratio, and histology were assessed. Values from eight animals euthanized shortly after anesthesia served as control. Results: No evidence of mechanical ventilation–dependent lung injury was found in terms of lung mechanics, histology, or wet-to-dry ratio. Relative to control, cytokine levels and recruitment of polymorphonuclear leucocytes increased slightly, and to the same extent with spontaneous, positive pressure, and whole-body negative pressure ventilation. Thorax-only negative pressure ventilation caused marked chest and lung distortion, reversible increase of lung elastance, and higher polymorphonuclear leucocyte count and cytokine levels. Conclusion: Both positive and negative pressure ventilation performed with tidal volumes and timing of spontaneous, quiet breathing neither elicit an inflammatory response nor cause morpho-functional alterations in normal animals, thus supporting the notion of the presence of a critical volume threshold above which acute lung injury ensues. Distortion of lung parenchyma can induce an inflammatory response, even in the absence of volotrauma.

Immersion diuresis in dogs

1977 ◽  
Vol 42 (6) ◽  
pp. 915-922 ◽  
Author(s):  
J. T. Davis ◽  
A. B. DuBois
Keyword(s):  
Negative Pressure ◽  
Early Phase ◽  
Left Atrial ◽  
Stretch Reflex ◽  
Transmural Pressure ◽  
Cervical Vagotomy ◽  
Anesthetized Dogs ◽  
Immersion Diuresis ◽  
Negative Pressure Breathing ◽  
Average Left Atrial

The mechanism of diuresis during the 1st h of immersion was investigated using anesthetized dogs. Four different experiments were carried out. First, left atrial transmural pressure was measured before, during, and after immersion. The data suggest that, although the left atrium may or may not be stretched depending on the conditions of immersion, the amount of diuresis is independent of the amount of left atrial stretch, and therefore a causal relationship between diuresis and left atrial stretch could not be established. Second, bilateral cervical vagotomy was carried out. Immersion diuresis sometimes occurred despite this vagotomy, suggesting that the left atrial stretch reflex was not participating in those cases. Third, negative-pressure breathing was carried out to simulate the negative transthoracic pressure associated with uncompensated immersion. The average left atrial transmural pressure did not change. A slight hemodilution and a moderate diuresis occurred. There was no correlation between changes in left atrial transmural pressure and changes in urine ouput. Fourth, blood studies were done on splenectomized dogs subjected to immersion. Hemodilution occurred and was most marked in dogs which had had their kidneys removed. The hemodilution is sufficient to explain the early phase of the immersion diuresis. The data suggest that, in anesthetized dogs, hemodilution is the probable initiator of diuresis upon immersion and that, in dogs, left atrial stretch is unrelated to diuresis during immersion or negative-pressure breathing.

scholarly journals The Mechanism of Gill Ventilation in Three Freshwater Teleosts

1958 ◽  
Vol 35 (4) ◽  
pp. 807-823 ◽  
Author(s):  
G. M. HUGHES
Keyword(s):  
Negative Pressure ◽  
Time Course ◽  
Phase 1 ◽  
Quantitative Relationship ◽  
Differential Pressure ◽  
Positive Pressure ◽  
Pressure Curve ◽  
Suction Pump ◽  
Opening And Closing ◽  
Pressure Changes

1. A study has been made of the respiratory movements of three species of freshwater fish. The time course of pressure changes in the buccal and opercular cavities was recorded and movements of the mouth and operculum plotted from ciné films taken simultaneously. 2. Opening and closing of the mouth precede respectively abduction and adduction of the operculum by about one-fifth of a cycle. 3. The most prominent part of the buccal pressure curve is a positive pressure associated with mouth closing. The size of a negative pressure as the mouth opens is small in the trout but may be relatively large in the tench. 4. Abduction of the operculum produces a marked negative pressure in the opercular cavity of all three species and there is a slight positive pressure during its adduction. 5. The respiratory system is divided into a buccal and two opercular cavities and the concept of gill resistances separating them is introduced. 6. The respiratory cycle is made up of four phases which succeed one another. These are: phase (1) opercular suction pump predominant; phase (2) transition with a reduction in differential pressure between the buccal and opercular cavities; phase (3) buccal pressure pump predominant; and phase (4) transition with reversal of differential pressure. 7. With the exception of phase (4), which occupies only about one-tenth of a cycle, the pressure in the buccal cavity exceeds that in the opercular cavity throughout the cycle. It is therefore concluded that water will flow across the gills for almost the entire cycle but may reverse for this brief period. The quantitative relationship between the pressures and the volume of water flowing across the gills during different parts of the cycle will depend upon the properties of the gill resistances.

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