Pulmonary mechanics during rapid mechanical ventilation in rabbits with saline-lavaged lungs

1986 ◽  
Vol 61 (4) ◽  
pp. 1431-1437 ◽  
Author(s):  
J. J. Perez Fontan ◽  
B. S. Turner ◽  
G. P. Heldt ◽  
G. A. Gregory
Keyword(s):  
Tidal Volume ◽  
Gas Flow ◽  
Transpulmonary Pressure ◽  
Inspiratory Flow ◽  
Pulmonary Mechanics ◽  
Mechanically Ventilated ◽  
Ventilatory Rate ◽  
Residual Capacity ◽  
Pressure Volume Relationship ◽  
Linear Ramp

Infants with respiratory failure are frequently mechanically ventilated at rates exceeding 60 breaths/min. We analyzed the effect of ventilatory rates of 30, 60, and 90 breaths/min (inspiratory times of 0.6, 0.3, and 0.2 s, respectively) on the pressure-flow relationships of the lungs of anesthetized paralyzed rabbits after saline lavage. Tidal volume and functional residual capacity were maintained constant. We computed effective inspiratory and expiratory resistance and compliance of the lungs by dividing changes in transpulmonary pressure into resistive and elastic components with a multiple linear regression. We found that mean pulmonary resistance was lower at higher ventilatory rates, while pulmonary compliance was independent of ventilatory rate. The transpulmonary pressure developed by the ventilator during inspiration approximated a linear ramp. Gas flow became constant and the pressure-volume relationship linear during the last portion of inspiration. Even at a ventilatory rate of 90 breaths/min, 28–56% of the tidal volume was delivered with a constant inspiratory flow. Our findings are consistent with the model of Bates et al. (J. Appl. Physiol. 58: 1840–1848, 1985), wherein the distribution of gas flow within the lungs depends predominantly on resistive factors while inspiratory flow is increasing, and on elastic factors while inspiratory flow is constant. This dynamic behavior of the surfactant-depleted lungs suggests that, even with very short inspiratory times, distribution of gas flow within the lungs is in large part determined by elastic factors. Unless the inspiratory time is further shortened, gas flow may be directed to areas of increased resistance, resulting in hyperinflation and barotrauma.

Ventilation with Constant Versus Decelerating Inspiratory Flow in Experimentally Induced Acute Respiratory Failure

1996 ◽  
Vol 84 (4) ◽  
pp. 882-889. ◽  
Author(s):  
Agneta M. Markstrom ◽  
Michael Lichtwarck-Aschoff ◽  
Bjorn A. Svensson ◽  
K. Anders Nordgren ◽  
Ulf H. Sjostrand
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Tidal Volume ◽  
Airway Pressure ◽  
Arterial Oxygen Tension ◽  
Inspiratory Flow ◽  
Arterial Oxygen ◽  
Positive End Expiratory Pressure ◽  
Residual Capacity ◽  
Inspiratory Flow Pattern

Background Recognition of the potential for ventilator-associated lung injury has renewed the debate on the importance of the inspiratory flow pattern. The aim of this study was to determine whether a ventilatory pattern with decelerating inspiratory flow, with the major part of the tidal volume delivered early, would increase functional residual capacity at unchanged (or even reduced) inspiratory airway pressures and improve gas exchange at different positive end-expiratory pressure levels. Methods Surfactant depletion was induced by repeated bronchoalveolar lavage in 13 anesthetized piglets. Decelerating and constant inspiratory flow ventilation was applied at positive end-expiratory pressure levels of 22, 17, 13, 9, and 4 cm H(2)O. Tidal volume, inspiration-to-expiration ratio, and ventilatory frequency were kept constant. Airway pressures, gas exchange, functional residual capacity (using a wash-in/washout method with sulfurhexafluoride), central hemodynamics, and extravascular lung water (using the thermo-dye-indicator dilution technique) were measured. Results Decelerating inspiratory flow yielded a lower arterial carbon dioxide tension compared to constant flow, that is, it improved alveolar ventilation. There were no differences between the flow patterns regarding end-inspiratory occlusion airway pressure, end-inspiratory lung volume, static compliance, or arterial oxygen tension. No differences were seen in hemodynamics and oxygen delivery. Conclusions The decelerating inspiratory flow pattern increased carbon dioxide elimination, without any reduction of inspiratory airway pressure or apparent improvement in arterial oxygen tension. It remains to be established whether these differences are sufficiently pronounced to justify therapeutic consideration.

Pulmonary mechanics during exercise in normal males

1980 ◽  
Vol 49 (3) ◽  
pp. 506-510 ◽  
Author(s):  
D. G. Stubbing ◽  
L. D. Pengelly ◽  
J. L. Morse ◽  
N. L. Jones
Keyword(s):  
Transpulmonary Pressure ◽  
Progressive Increase ◽  
Cycle Ergometer ◽  
Pulmonary Mechanics ◽  
Normal Male ◽  
Tidal Breathing ◽  
Control Value ◽  
Pulmonary Compliance ◽  
Capillary Blood Volume ◽  
Residual Capacity

A body plethysmograph adapted to contain the pedals of an electrically braked cycle ergometer was used to measure pulmonary mechanics during steady-state exercise in 12 normal male subjects aged 22-65 yr. During exercise there was a progressive increase in residual volume to 119% of the value at rest (P less than 0.01), but functional residual capacity and total lung capacity did not change. The maximum expiratory flow-volume (MEFV) curves did not change and flow rates during tidal breathing did not exceed the MEFV curve. Dynamic pulmonary compliance fell to 91.3% of the control value and static expiratory pulmonary compliance fell to 76.9% of the control value (P less than 0.05). Pulmonary resistance did not change during exercise. Transpulmonary pressure during tidal breathing was negative even at the highest power outputs. The fall in compliance may be due to an increase in pulmonary capillary blood volume. These results demonstrate the importance of measuring absolute thoracic gas volume and the elastic properties of the lung when comparing pulmonary mechanics at rest and during exercise.

Mechanism of action of ozone on the human lung

1989 ◽  
Vol 67 (4) ◽  
pp. 1535-1541 ◽  
Author(s):  
M. J. Hazucha ◽  
D. V. Bates ◽  
P. A. Bromberg
Keyword(s):  
Functional Residual Capacity ◽  
Airway Resistance ◽  
Transpulmonary Pressure ◽  
Dynamic Compliance ◽  
Exposure Period ◽  
Pulmonary Mechanics ◽  
Residual Volume ◽  
Residual Capacity ◽  
Controlled Exposure ◽  
Change Dynamic

Fourteen healthy normal volunteers were randomly exposed to air and 0.5 ppm of ozone (O3) in a controlled exposure chamber for a 2-h period during which 15 min of treadmill exercise sufficient to produce a ventilation of approximately 40 l/min was alternated with 15-min rest periods. Before testing an esophageal balloon was inserted, and lung volumes, flow rates, maximal inspiratory (at residual volume and functional residual capacity) and expiratory (at total lung capacity and functional residual capacity) mouth pressures, and pulmonary mechanics (static and dynamic compliance and airway resistance) were measured before and immediately after the exposure period. After the postexposure measurements had been completed, the subjects inhaled an aerosol of 20% lidocaine until response to citric acid aerosol inhalation was abolished. All of the measurements were immediately repeated. We found that the O3 exposure 1) induced a significant mean decrement of 17.8% in vital capacity (this change was the result of a marked fall in inspiratory capacity without significant increase in residual volume), 2) significantly increased mean airway resistance and specific airway resistance but did not change dynamic or static pulmonary compliance or viscous or elastic work, 3) significantly reduced maximal transpulmonary pressure (by 19%) but produced no changes in inspiratory or expiratory maximal mouth pressures, and 4) significantly increased respiratory rate (in 5 subjects by more than 6 breaths/min) and decreased tidal volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Chest wall mechanics during artificial ventilation

1975 ◽  
Vol 38 (4) ◽  
pp. 576-580 ◽  
Author(s):  
G. Grimby ◽  
G. Hedenstierna ◽  
B. Lofstrom
Keyword(s):  
Tidal Volume ◽  
Chest Wall ◽  
Gas Flow ◽  
Artificial Ventilation ◽  
Conscious State ◽  
Rib Cage ◽  
Chest Wall Mechanics ◽  
Pressure Volume Relationship ◽  
Relationship Of ◽  
Gas Volume

Chest wall mechanics were studied in six healthy volunteers before and during anesthesia prior to surgery. The intratracheal, esophageal, and intragastric pressures were measured concurrently. Gas flow was measured by pneumotachography and gas volume was obtained from it by electrical integration. Rib cage and abdomen movements were registered with magnetometers, these being calibrated by “isovolume” maneuvers. During spontaneous breathing in the conscious state, rib cage volume displacement corresponded to 40% of the tidal volume. During anesthesia and artificial ventilation, this rose to 72% of the tidal volume. The relative contributions of rib cage and abdomen displacements were not influenced by a change in tidal volume. Compliance was higher with a larger tidal volume, a finding which could be due to a curved pressure-volume relationship of the overall chest wall.

A respiratory function jacket for measuring tidal volume and changes in FRC

1983 ◽  
Vol 55 (1) ◽  
pp. 263-266 ◽  
Author(s):  
D. W. Cartwright ◽  
G. A. Gregory ◽  
M. M. Willis
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Strain Gauge ◽  
Respiratory Function ◽  
Base Line ◽  
Simple Application ◽  
Mechanically Ventilated ◽  
Residual Capacity

We describe a simple application of a mercury-in-rubber strain gauge in a jacket used to measure tidal volume in paralyzed, mechanically ventilated rabbits. The jacket produces a record with a straight base line. Shifts of this base line can be used to assess changes in functional residual capacity (FRC).

THE INFLUENCE OF FRESH GAS FLOW AND I/E RATIO ON TIDAL VOLUME AND PaCO2 IN ANESTHETIZED PATIENTS

1988 ◽  
Vol 67 (Supplement) ◽  
pp. 195
Author(s):  
M S Scheller ◽  
B L Jones ◽  
J L Benumof
Keyword(s):  
Tidal Volume ◽  
Gas Flow

Effect of ventilatory frequency on regional transpulmonary pressure in normal adults

1981 ◽  
Vol 51 (3) ◽  
pp. 678-685 ◽  
Author(s):  
W. Hida ◽  
S. Suzuki ◽  
H. Sasaki ◽  
Y. Fujii ◽  
T. Sasaki ◽  
...  
Keyword(s):  
Balloon Catheter ◽  
Transpulmonary Pressure ◽  
Dynamic Compliance ◽  
Local Dynamic ◽  
Ventilatory Frequency ◽  
Catheter System ◽  
Residual Capacity ◽  
Resistive Component ◽  
Normal Adults ◽  
Zero Frequency

The relation between the ventilatory frequency and the elastic (delta Pel) or resistive (delta Prs) components of changes of the regional pleural pressure (delta PL) was studied at functional residual capacity (FRC) in six normal adults. The regional delta PL was measured simultaneously at three levels in the esophagus using a three-balloon-catheter system. Elastic components of regional delta PL normalized by overall tidal volume (delta Pel/delta V) increased with frequency at all three balloon positions; the percentages of delta Pel/delta V at 60 breaths/min to those at zero frequency were 107, 119, and 157% in the upper, middle, and lower balloon, respectively. The resistive component of regional delta PL normalized by overall air flow (delta Prs/delta V) did not show significant dependence on frequency at any of the three positions and was almost the same everywhere. It is suggested that the increase of local delta Pel with frequency might reflect mainly the frequency dependence of local dynamic compliance (Cdyn) and that the change of the local Cdyn with frequency might be larger in dependent than in upper lung.

Dynamic mechanisms determine functional residual capacity in mice, Mus musculus

1979 ◽  
Vol 46 (5) ◽  
pp. 867-871 ◽  
Author(s):  
A. Vinegar ◽  
E. E. Sinnett ◽  
D. E. Leith
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Flow Volume ◽  
Linear Portion ◽  
Volume Curve ◽  
Flow Volume Curve ◽  
Residual Capacity ◽  
Expiratory Flow ◽  
The Difference ◽  
Pentobarbital Sodium Anesthesia

Awake mice (22.6--32.6 g) were anesthetized intravenously during head-out body plethysmography. One minute after pentobarbital sodium anesthesia, tidal volume had fallen from 0.28 +/- 0.04 to 0.14 +/- 0.02 ml and frequency from 181 +/- 20 to 142 +/- 8. Functional residual capacity (FRC) decreased by 0.10 +/- 0.02 ml. Expiratory flow-volume curves were linear, highly repeatable, and submaximal over substantial portions of expiration in awake and anesthetized mice; and expiration was interrupted at substantial flows that abruptly fell to and crossed zero as inspiration interrupted relaxed expiration. FRC is maintained at a higher level in awake mice due to a higher tidal volume and frequency coupled with expiratory braking (persistent inspiratory muscle activity or increased glottal resistance). In anesthetized mice, the absence of braking, coupled with reductions in tidal volume and frequency and a prolonged expiratory period, leads to FRCs that approach relaxation volume (Vr). An equation in derived to express the difference between FRC and Vr in terms of the portion of tidal volume expired without braking, the slope of the linear portion of the expiratory flow-volume curve expressed as V/V, the time fraction of one respiratory cycle spent in unbraked expiration, and respiratory frequency.

STUDIES OF RESPIRATORY PHYSIOLOGY IN CHILDREN

PEDIATRICS ◽  
1959 ◽  
Vol 24 (2) ◽  
pp. 181-193
Author(s):  
C. D. Cook ◽  
P. J. Helliesen ◽  
L. Kulczycki ◽  
H. Barrie ◽  
L. Friedlander ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Respiratory Rate ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Lung Compliance ◽  
Respiratory Physiology ◽  
Residual Volume ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Residual Capacity

Tidal volume, respiratory rate and lung volumes have been measured in 64 patients with cystic fibrosis of the pancreas while lung compliance and resistance were measured in 42 of these. Serial studies of lung volumes were done in 43. Tidal volume was reduced and the respiratory rate increased only in the most severely ill patients. Excluding the three patients with lobectomies, residual volume and functional residual capacity were found to be significantly increased in 46 and 21%, respectively. These changes correlated well with the roentgenographic evaluation of emphysema. Vital capacity was significantly reduced in 34% while total lung capacity was, on the average, relatively unchanged. Seventy per cent of the 61 patients had a signficantly elevated RV/TLC ratio. Lung compliance was significantly reduced in only the most severely ill patients but resistance was significantly increased in 35% of the patients studied. The serial studies of lung volumes showed no consistent trends among the groups of patients in the period between studies. However, 10% of the surviving patients showed evidence of significant improvement while 15% deteriorated. [See Fig. 8. in Source Pdf.] Although there were individual discrepancies, there was a definite correlation between the clinical evaluation and tests of respiratory function, especially the changes in residual volume, the vital capacity, RV/ TLC ratio and the lung compliance and resistance.

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