Effect of lung inflation on regional lung expansion in supine and prone rabbits

1991 ◽  
Vol 71 (1) ◽  
pp. 76-82 ◽  
Author(s):  
Q. H. Yang ◽  
S. J. Lai-Fook
Keyword(s):  
Prone Position ◽  
Functional Residual Capacity ◽  
Supine Position ◽  
Vertical Gradient ◽  
Lung Inflation ◽  
Lung Expansion ◽  
Isolated Lung ◽  
Residual Capacity ◽  
Lung Deflation

At functional residual capacity, lung expansion is more uniform in the prone position than in the supine position. We examined the effect of positive airway pressure (Paw) on this position-dependent difference in lung expansion. In supine and prone rabbits postmortem, we measured alveolar size through dependent and nondependent pleural windows via videomicroscopy at Paw of 0 (functional residual capacity), 7, and 15 cmH2O. After the chest was opened, alveolar size was measured in the isolated lung at several transpulmonary pressures (Ptp) on lung deflation. Alveolar mean linear intercept (Lm) was measured from the video images taken in situ. This was compared with those measured in the isolated lung to determine Ptp in situ. In the supine position, the vertical Ptp gradient increased from 0.52 cmH2O/cm at 0 cmH2O Paw to 0.90 cmH2O/cm at 15 cmH2O Paw, while the vertical gradient in Lm decreased from 2.17 to 0.80 microns/cm. In the prone position, the vertical Ptp gradient increased from 0.06 cmH2O/cm at 0 cmH2O Paw to 0.35 cmH2O/cm at 15 cmH2O Paw, but there was no change in the vertical Lm gradient. In anesthetized paralyzed rabbits in supine and prone positions, we measured pleural liquid pressure directly at 0, 7, and 15 cmH2O Paw with dependent and nondependent rib capsules. Vertical Ptp gradients measured with rib capsules were similar to those estimated from the alveolar size measurements. Lung inflation during mechanical ventilation may reduce the vertical nonuniformities in lung expansion observed in the supine position, thereby improving gas exchange and the distribution of ventilation.

Regional variations in lung expansion in rabbits: prone vs. supine positions

1989 ◽  
Vol 67 (4) ◽  
pp. 1371-1376 ◽  
Author(s):  
Q. H. Yang ◽  
M. R. Kaplowitz ◽  
S. J. Lai-Fook
Keyword(s):  
Prone Position ◽  
Surface Pressure ◽  
Supine Position ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Liquid Pressure ◽  
Pleural Surface ◽  
Lung Expansion ◽  
Pleural Liquid Pressure

We studied the vertical gradient in lung expansion in rabbits in the prone and supine body positions. Postmortem, we used videomicroscopy to measure the size of surface alveoli through transparent parietal pleural windows at dependent and nondependent sites separated in height by 2–3 cm at functional residual capacity (FRC). We compared the alveolar size measured in situ with that measured in the isolated lungs at different deflationary transpulmonary pressures to obtain transpulmonary pressure (pleural surface pressure) in situ. The vertical gradient in transpulmonary pressure averaged 0.48 +/- 0.16 (SD) cmH2O/cm height (n = 10) in the supine position and 0.022 +/- 0.014 (SD) cmH2O/cm (n = 5) in the prone position. In mechanically ventilated rabbits, we used the rib capsule technique to measure pleural liquid pressure at different heights of the chest in prone and supine positions. At FRC, the vertical gradient in pleural liquid pressure averaged 0.63 cmH2O/cm in the supine position and 0.091 cmH2O/cm in the prone position. The vertical gradients in pleural liquid pressure were all less than the hydrostatic value (1 cmH2O/cm), which indicates that pleural liquid is not generally in hydrostatic equilibrium. Both pleural surface pressure and pleural liquid pressure measurements show a greater vertical gradient in the supine than in the prone position. This suggests a close relationship between pleural surface pressure and pleural liquid pressure. Previous results in the dog and pony showed relatively high vertical gradients in the supine position and relatively small gradients in the prone position. This behavior is similar to the present results in rabbits. Thus the vertical gradient is independent of animal size and might be related to chest shape and weight of heart and abdominal contents.

Effect of body position on regional diaphragm function in dogs

1990 ◽  
Vol 69 (6) ◽  
pp. 2296-2302 ◽  
Author(s):  
J. Sprung ◽  
C. Deschamps ◽  
S. S. Margulies ◽  
R. D. Hubmayr ◽  
J. R. Rodarte
Keyword(s):  
Prone Position ◽  
Regional Differences ◽  
Body Position ◽  
Vertical Gradient ◽  
Transdiaphragmatic Pressure ◽  
Lung Capacity ◽  
Volume Relationship ◽  
Residual Capacity ◽  
Fractional Shortening

The in situ lengths of muscle bundles of the crural and three regions of the costal diaphragm between origin and insertion were determined with a video roentgenographic technique in dogs. At total lung capacity (TLC) in both the prone and supine positions, the length of the diaphragm is not significantly different from the unstressed excised length, suggesting that the diaphragm is not under tension at TLC and that there is a hydrostatic gradient of pleural pressure on the diaphragmatic surface. Except for the ventral region of the costal diaphragm, which does not change length at lung volumes greater than 70% TLC, all other regions are stretched during passive deflations from TLC. Therefore below TLC the diaphragm is under passive tension and supports a transdiaphragmatic pressure (Pdi). The length of the diaphragm relative to its unstressed length is not uniform at functional residual capacity (FRC) and does not follow a strict vertical gradient that reverses when the animal is changed from the supine to the prone position. By inference, the length of muscle bundles is determined by factors other than the vertical gradient of Pdi. During mechanical ventilation, regional shortening is identical to the passive deflation length-volume relationship near FRC. Prone and supine FRC is the same, but the diaphragm is slightly shorter in the prone position. In both positions, during spontaneous ventilation there are no consistent differences in regional fractional shortening, despite regional differences in initial length relative to unstressed length.

Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo

1991 ◽  
Vol 70 (6) ◽  
pp. 2611-2618 ◽  
Author(s):  
T. Mutoh ◽  
W. J. Lamm ◽  
L. J. Embree ◽  
J. Hildebrandt ◽  
R. K. Albert
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Functional Residual Capacity ◽  
Total Lung Capacity ◽  
Abdominal Cavity ◽  
Abdominal Distension ◽  
Abdominal Pressure ◽  
Lung Capacity ◽  
Lung Expansion ◽  
Residual Capacity

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.

Effect of body posture on lung volumes

1961 ◽  
Vol 16 (1) ◽  
pp. 27-29 ◽  
Author(s):  
Francisco Moreno ◽  
Harold A. Lyons
Keyword(s):  
Tidal Volume ◽  
Prone Position ◽  
Supine Position ◽  
Total Lung Capacity ◽  
Minute Ventilation ◽  
Normal Subjects ◽  
Body Posture ◽  
Mean Values ◽  
Lung Capacity ◽  
Residual Capacity

The changes produced by body posture on total lung capacity and its subdivisions have been reported for all positions except the prone position. Twenty normal subjects, twelve males and eight females, had determinations of total lung capacity in the three body positions, sitting, supine and prone. Tidal volume, minute ventilation and O2 consumption were also measured. The changes found on assumption of the supine position from the sitting position were similar to those previously reported. For the prone position, a smaller inspiratory capacity and a larger expiratory reserve volume were found. The mean values were changed, respectively, –8% and +37%. Associated with these changes was a significant increase of the functional residual capacity by 636 ml. Ventilation did not change significantly from that found during sitting, unlike the findings associated with the supine position, in which position the tidal volume was decreased. Respiratory frequency remained the same for all positions. Submitted on April 5, 1960

Mechanical implications of in vivo human diaphragm shape

1992 ◽  
Vol 72 (4) ◽  
pp. 1407-1412 ◽  
Author(s):  
M. Paiva ◽  
S. Verbanck ◽  
M. Estenne ◽  
B. Poncelet ◽  
C. Segebarth ◽  
...  
Keyword(s):  
Surface Area ◽  
Functional Residual Capacity ◽  
Three Dimensional ◽  
Vertical Gradient ◽  
Total Surface Area ◽  
Diaphragm Muscle ◽  
Posterior Half ◽  
Transdiaphragmatic Pressure ◽  
Residual Capacity

Using magnetic resonance imaging, we measured the three-dimensional form of the diaphragm in vivo in four supine relaxed subjects at functional residual capacity and calculated its total surface area, the right and left surface areas in the zone of apposition, and the principal radii of curvature as a function of height. The area of apposition comprised 45 +/- 1.5% (SE) of the total surface area of the diaphragm. Available data on the area of the central tendon indicate that a considerable part of the muscular part of the diaphragm is lung apposed. The curvature was linearly related to height over 7 cm of the posterior half of each hemidiaphragm. From the linear portion of this graph and assuming a vertical gradient of transdiaphragmatic pressure of 0.75 cmH2O/cm, we applied the Laplace law and calculated tensions of 54 and 32 g/cm for right and left sides, respectively. We conclude that the shape of at least part of the posterior half of the relaxed human diaphragm in the supine position at functional residual capacity can be explained by the Laplace law, suggesting that both the lung and abdominal contents behave sufficiently as fluids so that they do not impose their shape on the diaphragm. Because diaphragm muscle is partly lung apposed, it is unlikely that the diaphragm functions simply as a piston.

Effects of body position and lung volume on in situ operating length of canine diaphragm

1990 ◽  
Vol 69 (5) ◽  
pp. 1702-1708 ◽  
Author(s):  
S. S. Margulies ◽  
G. A. Farkas ◽  
J. R. Rodarte
Keyword(s):  
Lung Volume ◽  
Body Position ◽  
Vertical Gradient ◽  
Postoperative Recovery ◽  
Optimal Force ◽  
Residual Capacity ◽  
Crural Diaphragm

The performance of the diaphragm is influenced by its in situ length relative to its optimal force-generating length (Lo). Lead markers were sutured to the abdominal surface of the diaphragm along bundles of the left ventral, middle, and dorsal regions of the costal diaphragm and the left crural diaphragm of six beagle dogs. After 2-3 wk postoperative recovery, the dogs were anesthetized, paralyzed, and scanned prone and supine in the Dynamic Spatial Reconstructor (DSR) at a total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV). The location of each marker was digitized from the reconstructed DSR images, and in situ lengths were determined. After an overdose of anesthetic had been administered to the dogs, each marked diaphragm bundle was removed, mounted in a 37 degrees C in vitro chamber, and adjusted to Lo (maximum tetanic force). The operating length of the diaphragm, or in situ length expressed as percent Lo, varied from region to region at the lung volumes studied; variability was least at RV and increased with increasing lung volume. At FRC, all regions of the diaphragm was shorter in the prone posture compared with the supine, but there was no clear gravity-dependent vertical gradient of in situ length in either posture. Because in vitro length-tension characteristics were similar for all diaphragm regions, regional in vivo length differences indicate that the diaphragm's potential to generate maximal force is nonuniform.

Effect of artificial surfactant on pulmonary function in preterm and full-term lambs

1990 ◽  
Vol 69 (2) ◽  
pp. 465-472 ◽  
Author(s):  
I. M. Gladstone ◽  
A. O. Ray ◽  
C. M. Salafia ◽  
J. Perez-Fontan ◽  
M. R. Mercurio ◽  
...  
Keyword(s):  
Surface Tension ◽  
Functional Residual Capacity ◽  
Dynamic Compliance ◽  
Full Term ◽  
Tween 20 ◽  
Minimum Surface ◽  
Natural Surfactant ◽  
Equilibrium Surface Tension ◽  
Lung Expansion ◽  
Residual Capacity

We hypothesized that agents very different from surfactant may still support lung function. To test this hypothesis, we instilled FC-100, a fluorocarbon, and Tween 20, a detergent, which have higher minimum surface tensions and less hysteresis than surfactant, into 15 full-term and 14 preterm lambs. FC-100 and Tween 20 were as efficient as natural surfactant in improving gas exchange and compliance in preterm lambs with respiratory failure. Dynamic compliance correlated with the equilibrium surface tension of the alveolar wash in both full-term (P less than 0.02) and preterm (P less than 0.008) lambs. Functional residual capacity in full-term and preterm lambs was lower after treatment with the two test agents than with surfactant, findings consistent with qualitative histology. Oxygenation in full-term lambs correlated with mean lung volumes (P less than 0.003), suggesting that the hysteresis and/or low minimum surface tension of surfactant may improve mean lung volume, and hence oxygenation, by maintaining functional residual capacity. The effects of the test agents suggest that agents with biophysical properties different from surfactant may still aid lung expansion.

scholarly journals Respiratory-related neurons of the fastigial nucleus in response to chemical and mechanical challenges

1997 ◽  
Vol 82 (4) ◽  
pp. 1177-1184 ◽  
Author(s):  
Fadi Xu ◽  
Donald T. Frazier
Keyword(s):  
Skeletal Muscle ◽  
Muscle Contraction ◽  
Firing Rate ◽  
Functional Residual Capacity ◽  
Fastigial Nucleus ◽  
Related Activity ◽  
Lung Inflation ◽  
Single Breath ◽  
Skeletal Muscle Contraction ◽  
Residual Capacity

Xu, Fadi, and Donald T. Frazier. Respiratory-related neurons of the fastigial nucleus in response to chemical and mechanical challenges. J. Appl. Physiol. 82(4): 1177–1184, 1997.—Responses of cerebellar respiratory-related neurons (CRRNs) within the rostral fastigial nucleus and the phrenic neurogram to activation of respiratory mechano- and chemoreceptors were recorded in anesthetized, paralyzed, and ventilated cats. Respiratory challenges included the following: 1) cessation of the ventilator for a single breath at the end of inspiration (lung inflation) or at functional residual capacity, 2) cessation of the ventilator for multiple breaths, and 3) exposure to hypercapnia. Nineteen CRRNs having spontaneous activity during control conditions were characterized as either independent (basic, n = 14) or dependent (pump, n = 5) on the ventilator movement. Thirteen recruited CRRNs showed no respiratory-related activity until breathing was stressed. Burst durations of expiratory CRRNs were prolonged by sustained lung inflation but were inhibited when the volume was sustained at functional residual capacity; it was vice versa for inspiratory CRRNs. Multiple-breath cessation of the ventilator and hypercapnia significantly increased the firing rate and/or burst duration concomitant with changes noted in the phrenic neurogram. We conclude that CRRNs respond to respiratory inputs from CO2 chemo- and pulmonary mechanoreceptors in the absence of skeletal muscle contraction.

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