Exponential fitting of pressure-volume curves: confidence limits and sensitivity to noise

1990 ◽  
Vol 69 (4) ◽  
pp. 1538-1541 ◽  
Author(s):  
D. H. Eidelman ◽  
H. Ghezzo ◽  
J. H. Bates
Keyword(s):  
Confidence Intervals ◽  
Static Pressure ◽  
Transpulmonary Pressure ◽  
Exponential Fitting ◽  
Confidence Limits ◽  
Data Set ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Parameter Values ◽  
Biased Estimates

It has recently become common to model the static pressure-volume curve of the lung as a monoexponential function of the form V = A - Be-KP, where V is volume and P is transpulmonary pressure. The parameters A, B, and particularly K have been employed as descriptors of the intrinsic mechanical properties of the lung. The purpose of the present study was to investigate the sensitivities of A, B, and K to noise in measurements of P and V and to incompleteness of data. Using Monte-Carlo simulation, we found that the presence of typical levels of noise in P led to biased estimates of K and that the 95% confidence intervals about A and K were large compared with the parameter values themselves. These effects were increased as points were systematically removed from either end of the data set. These findings show that values of K estimated from PV data are difficult to interpret without accompanying confidence intervals.

Static pressure-volume characteristics of lungs in normal males

1960 ◽  
Vol 15 (5) ◽  
pp. 819-825 ◽  
Author(s):  
Solbert Permutt ◽  
H. B. Martin
Keyword(s):  
Vital Capacity ◽  
Static Pressure ◽  
Muscle Power ◽  
Transpulmonary Pressure ◽  
Residual Volume ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Older Subjects ◽  
Normal Males ◽  
Volume Characteristics

The static pressure-volume characteristics of the lungs were determined in 28 normal males between the ages of 21 and 76 years. Transpulmonary pressures were measured in relation to absolute lung volumes throughout the entire range of the vital capacity, both on inspiration and expiration. There was an increase in residual volume and a decrease in vital capacity, but no change in the slope or position of the pressure-volume curve with advancing age. It appeared that the older subjects were unable to change transpulmonary pressure between residual volume and total lung capacity to the same extent as the younger subjects. The results suggest that with advancing age there is little change in the intrinsic static pressure-volume characteristics of the lungs themselves, and that all of the significant changes with age are more likely due to changes in either the compliance or muscle power of the thorax. Submitted on December 24, 1959

Improved measurements of shear modulus and pleural membrane tension of the lung

1979 ◽  
Vol 47 (1) ◽  
pp. 175-181 ◽  
Author(s):  
M. A. Hajji ◽  
T. A. Wilson ◽  
S. J. Lai-Fook
Keyword(s):  
Shear Modulus ◽  
Transpulmonary Pressure ◽  
Elastic Half Space ◽  
Concentrated Force ◽  
Membrane Area ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Pressure Independent ◽  
Work Done ◽  
The Continuum

The continuum solution for the deformation of an elastic half space covered by a membrane is used to interpret measurements of the indentation of lung lobes under a column of fluid. The shear modulus mu of the underlying parenchyma is found to be approximately 0.7 times transpulmonary pressure, independent of species size. The tension in the pleural membrane T increases rapidly with increasing membrane area. For dog lungs, the value of T is 10(3) to 10(4) dyn/cm. For the larger species tested, pigs and horses, T is larger. The continuum solution shows that a concentrated force applied to the pleural surface is distributed over a distance T/mu as it is transmitted across the pleural membrane. The membrane is important in determining the displacement produced by forces that act within a region that is small compared to this distance, approximately 2 cm for dog lungs. By comparing the tension-area curve of the pleural membrane with the pressure-volume curve of the lobe, it is found that the pleural membrane contributes about 20% of the work done by the lung during deflation.

Evidence for increased intrathoracic fluid volume in man at high altitude

1979 ◽  
Vol 47 (4) ◽  
pp. 670-676 ◽  
Author(s):  
J. J. Jaeger ◽  
J. T. Sylvester ◽  
A. Cymerman ◽  
J. J. Berberich ◽  
J. C. Denniston ◽  
...  
Keyword(s):  
Pulmonary Edema ◽  
High Altitude ◽  
Transpulmonary Pressure ◽  
Fluid Volume ◽  
Pulmonary Mechanics ◽  
Volume Curve ◽  
Extravascular Fluid ◽  
Pressure Volume Curve ◽  
Transthoracic Electrical Impedance ◽  
Extravascular Fluid Volume

To determine if subclinical pulmonary edema occurs commonly at high altitude, 25 soldiers participated in two consecutive 72-h field exercises, the first at low altitude (200–875 m) and the second at high altitude (3,000–4,300 m). Various aspects of ventilatory function and pulmonary mechanics were measured at 0, 36, and 72 h of each exercise. Based on physical examination and chest radiographs there was no evidence of pulmonary edema at high altitude. There was, however, an immediate and sustained decrease in vital capacity and transthoracic electrical impedance as well as a clockwise rotation of the transpulmonary pressure-volume curve. In contrast, closing capacity and residual volume did not change immediately upon arrival at high altitude but did increase later during the exposure. These observations are consistent with an abrupt increase in thoracic intravascular fluid volume upon arrival at high altitude followed by a more gradual increase in extravascular fluid volume in the peribronchial spaces of dependent lung regions.

Series distribution of airway collapsibility in dogs

1981 ◽  
Vol 50 (2) ◽  
pp. 325-333 ◽  
Author(s):  
M. Nakamura ◽  
H. Sasaki ◽  
K. Sekizawa ◽  
M. Ishii ◽  
T. Takishima ◽  
...  
Keyword(s):  
Transpulmonary Pressure ◽  
Forced Expiration ◽  
Peripheral Airways ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Airway Collapsibility

We studied the series distribution of collapsibility in four different-sized airways in dogs. The trachea and the extrapulmonary main bronchi in situ were isolated from the rest of the lungs by glued beads of 6-12 mm OD. In excised dog lungs, the intrapulmonary large and small bronchi were isolated from the rest of the lung by glued beads of 1-9 mm OD. Pressure-volume relationships were measured directly in the trachea and in the extrapulmonary bronchi; those of the intrapulmonary bronchi were derived from orthogonal bronchograms. Airway collapsibility, defined as the slope of the pressure-volume curve, was found to increase in all airways as transpulmonary pressure (PL) decreased. At PL 30 cmH2O there was little difference of airway collapsibility among the different sized airways; but, as PL decreased, the peripheral airways became more collapsible than the central airways. It is concluded that the tissues surrounding the trachea provided as much or more stiffness than did the lung tissues that surrounded the intrapulmonary airways. The larger collapsibility in the peripheral airways. The larger collapsibility in the peripheral airways relative to that of the central airways at lower PL may account for the peripheral migration of the flow-limiting segment during forced expiration.

Gravitational independence of single-breath washout tests in recumbent dogs

1988 ◽  
Vol 64 (2) ◽  
pp. 642-648 ◽  
Author(s):  
S. Tomioka ◽  
S. Kubo ◽  
H. J. Guy ◽  
G. K. Prisk
Keyword(s):  
Prone Position ◽  
Regional Distribution ◽  
Transpulmonary Pressure ◽  
Phase Iii ◽  
Closing Volume ◽  
Body Rotation ◽  
Single Breath ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Phase Iv

To examine the mechanisms of lung filling and emptying, Ar-bolus and N2 single-breath washout tests were conducted in 10 anesthetized dogs (prone and supine) and in three of those dogs with body rotation. Transpulmonary pressure was measured simultaneously, allowing identification of the lung volume above residual volume at which there was an inflection point in the pressure-volume curve (VIP). Although phase IV for Ar was upward, phase IV for N2 was small and variable, especially in the prone position. No significant prone to supine differences in closing capacity for Ar were seen, indicating that airway closure was generated at the same lung volumes. The maximum deflections of phase IV for Ar and N2 from extrapolated phase III slopes were smaller in the prone position, suggesting more uniform tracer gas concentrations across the lungs. VIP was smaller than the closing volume for Ar, which is consistent with the effects of well-developed collateral ventilation in dogs. Body rotation tests in three dogs did not generally cause an inversion of phase III or IV. We conclude that in recumbent dogs regional distribution of ventilation is not primarily determined by the effect of gravity, but by lung, thorax, and mediastinum interactions and/or differences in regional mechanical properties of the lungs.

Effects of bronchoactive agents on static pressure-volume characteristics of dog lungs

1964 ◽  
Vol 206 (2) ◽  
pp. 321-326 ◽  
Author(s):  
Seiichi Yoshida
Keyword(s):  
Static Pressure ◽  
Pulmonary Arteries ◽  
Drug Infusion ◽  
Bronchial Arteries ◽  
Airway Pressures ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
The Difference ◽  
Volume Characteristics ◽  
Surface Tension Forces

Static pressure-volume characteristics of the lung in the thoracotomized dog have been studied during continuous infusion of bronchoconstrictor agents into the isolated bronchial arteries, or of sympathomimetic amines into the pulmonary arteries. At inflation pressures less than 20 mm Hg, static airway pressures were higher for a given volume during histamine or acetylcholine infusion than those of the controls. The difference in pressure was marked during inflation from the collapsed state; it was small when inflation was initiated from the end-inspiratory level. When the lung was fully expanded the difference in pressure was insignificant, i.e., drug infusion had no effect on airway pressures. During deflation the pressure-volume curve nearly retraced that of the controls, and pulmonary compliance calculated from the middle third of the deflation curves showed minimal differences. Infusions of epinephrine or norepinephrine into the pulmonary artery did not alter static pressure-volume characteristics. The present findings suggest that bronchoconstriction may lead to closure of some of the pulmonary air spaces by surface tension forces, resulting in a decrease in the number of units sharing a given air volume.

EFFECTS OF VOLUME AND DISTRIBUTION OF MILK ON THE OXYTOCIN-INDUCED CONTRACTION OF THE LACTATING RAT MAMMARY GLAND IN VIVO

1971 ◽  
Vol 51 (3) ◽  
pp. 437-446 ◽  
Author(s):  
D. J. DeNUCCIO ◽  
C. E. GROSVENOR
Keyword(s):  
Mammary Gland ◽  
Static Pressure ◽  
Pressure Response ◽  
Progressive Reduction ◽  
Equilibrium Pressure ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Rat Mammary Gland ◽  
Different Doses

SUMMARY Milk was added intraductally in 0·2 ml increments to previously emptied mammary glands in rats. Direct microscopic observations of the glands showed that each increment of milk did not distribute evenly either within a single lobule or among lobules. Increase of the intramammary pressure either by i.v. injection of oxytocin or by compression of the gland between thumb and forefinger, distributed the milk more evenly within the gland. These observations led to the routine injection of 1·6–3·2 mu. oxytocin in order to distribute each increment of milk evenly throughout the gland. The intramammary pressure response of the gland to different doses of oxytocin was then determined. The rises in intramammary pressure above equilibrium pressure in response to 0·8 and 1·6 mu. oxytocin increased fourfold on average with increasing gland volume over the compliant portion of the static pressure-volume curve. The slopes of the dose oxytocin-intramammary pressure response lines became progressively steeper and shifted to the left as the volume of the mammary gland increased, indicating a progressive reduction in the dose of oxytocin required to elicit a given response. No differences were noted between rats lactating for 9–13 days and those lactating for 20–24 days. In a related study the duct system of the rat gland was found to contain little fluid even after 8 h of non-suckling, though it became filled swiftly after a single i.v. injection of oxytocin. Non-suckling for 16–24 h was required to overcome passively the resistance to entry of milk from the alveoli.

Role of autonomic nervous system controlling surface tension in fetal rabbit lungs

1977 ◽  
Vol 43 (6) ◽  
pp. 1039-1045 ◽  
Author(s):  
A. J. Corbet ◽  
P. Flax ◽  
A. J. Rudolph
Keyword(s):  
Nervous System ◽  
Adrenergic Receptors ◽  
Static Pressure ◽  
Parasympathetic Nervous System ◽  
Uterine Wall ◽  
System A ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Stimulation Of

After the maternal abdomen was opened under methoxyflurane anesthesia, fetal rabbits of 27.5 days gestation were given injections through the intact uterine wall of saline, pilocarpine, isoxsuprine, muscarine, phenylephrine, atropine, phenoxybenzamine, or propranolo, alone or in appropriate combinations. Fetal rabbits were delivered by hysterotomy and killed without breathing 2.5 h later. Static pressure-volume curves with air showed improved retention on deflation in fetal rabbits that had injections of pilocarpine, or isoxsuprine, but not of muscarine or phenylephrine. The effect of pilocarpine on the pressure-volume curve was blocked by atropine, phenoxybenzamine, and propranolol, and the effect of isoxsuprine was blocked by propranolol but not phenoxybenzamine. The data suggest that pilocarpine produces secretion of surfactant into lung air spaces by exciting the sympathetic nervous system, a known function of pilocarpine, rather than the parasympathetic nervous system. This may result in stimulation of the same beta-adrenergic receptors affected by isoxsuprine which is also thought to stimulate surfactant secretion.

Positive airway pressure and vertical transpulmonary pressure gradient in man

1975 ◽  
Vol 38 (5) ◽  
pp. 896-899 ◽  
Author(s):  
K. Rehder ◽  
N. Abboud ◽  
J. R. Rodarte ◽  
R. E. Hyatt
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Pressure Gradient ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Normal Subjects ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Consistent Change

Static transpulmonary pressure (Pao-Pes) and the vertical gradient of transpulmonary pressure were determined in five sitting conscious normal subjects at mean airway pressures of 0 (ambient), 11, and 21 cmH2O. All subjects exhibited a nonuniform transpulmonary pressure gradient down the esophagus. The vertical pressure gradient was consistently larger in the lower (8–20cm below esophageal artifact) than in the middle region (0–8cm) of the esophagus. The gradient was not significantly altered by continuous positive airway pressure (11 and 21 cmH2O) or by changes in lung volume (60, 70, and 80% of total lung capacity (TLC)). Continuous positive airway pressure also did not result in a consistent change of the overall static pressure-volume curve of the lung. There was a small but statistically significant increase in TLC with each increase in airway pressure.

Effects of airway versus arterial CO2 changes on lung mechanics in dogs

1975 ◽  
Vol 38 (4) ◽  
pp. 603-607 ◽  
Author(s):  
R. H. Ingram
Keyword(s):  
Partial Pressure ◽  
Normal Level ◽  
Static Pressure ◽  
Artery Occlusion ◽  
Lung Mechanics ◽  
Small Airways ◽  
Co2 Partial Pressure ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Unilateral Pulmonary Artery Occlusion

The effects of changes in airway CO2 partial pressure (PAco2) and arterial CO2 partial pressure (Paco2) on lung mechanics were studied in dogs by utilizing unilateral pulmonary artery occlusion and a tracheal divider which allowed separate variation of PAco2 and Paco2. When Paco2 was held at a reasonably normal level, lower than normal PAco2 levels resulted in large compliance decreases, alteration of the complete static pressure-volume curves, and increases in resistance. Invreases in PAco2 to hypercapnic levels did not produce changes. When PAco2 was held at a reasonably normal level, changes in Paco2 levels were positively and directly related to resistance with small and inconsistent effects on compliance and on complete static pressure-volume curves. A combination of low PAco2 and high Paco2 produced large increases in resistance, alterations of the static pressure-volume curve, and decreases in compliance. Vagotomy during the combined stimulus resulted in only a decrease in resistance without change in lung elastic properties. The results suggest that the mechanical effects of airway hypocapnia and systemic hypercapnia are additive. However, small airways effects of low PAco2 appear to be maximal and uninfluenced by the vagally mediated response to Paco2 increases.

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