Pressure-Volume Curve of Total Respiratory System in Acute Respiratory Failure: Computed Tomographic Scan Study

Quasi-static, pulmonary pressure-volume (P-V) curves over an inflation-deflation cycle are analyzed using a respiratory system model (RSM), which had been developed for quantitative characterization of the mechanical behavior of the total respiratory system. Optimum mechanical ventilation setting of Positive End Expiratory Pressure (PEEP) for total alveolar recruitment is quantified based on the existing P-V curves of healthy and injured animal models. Our analytical predictions may contribute to the optimization of mechanical ventilation settings for the Acute Respiratory Distress Syndrome (ARDS) patients.

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Comparative aspects of the dynamics of breathing in newborn mammals

Journal of Applied Physiology ◽

10.1152/jappl.1983.54.5.1229 ◽

1983 ◽

Vol 54 (5) ◽

pp. 1229-1235 ◽

Cited By ~ 15

Author(s):

J. P. Mortola

Keyword(s):

Body Size ◽

Respiratory System ◽

Dynamic Properties ◽

Upper Airway ◽

Lung Compliance ◽

Expiratory Time ◽

Volume Curve ◽

Pressure Volume Curve ◽

Dynamic Lung Compliance ◽

Spontaneously Breathing

Static and dynamic properties of the respiratory system have been studied in anesthetized, tracheostomized newborns of six species, ranging in size from rats to piglets. Respiratory system compliance (Crs), total resistance of respiratory system (Rrs), and expiratory time constant (tau) have been measured in the paralyzed passively ventilated animals. Crs is found to be proportional to body weight (BW0.80) and Rrs to BW-0.75; tau is independent of body size, the shortest value being in kittens and guinea pigs and a value of about 0.14 s in the other species. Including the upper airway resistance, tau becomes approximately 0.22 s. This value is similar to the expiratory time of the fastest breathing species; therefore in the smallest species the high breathing rate can be regarded as a mechanism to raise end-expiratory level. On a few occasions, dynamic lung compliance and pulmonary resistance, measured in spontaneously breathing kittens, puppies, and piglets were, respectively, smaller and larger than Crs and Rrs, suggesting that the hysteresis of the pressure-volume curve may be substantial. Rrs was almost linear within the volume and flow range investigated, with the Rohrer's constant K2 always being less than 2.5% of K1. The Reynolds number increases with body size (alpha BW0.51) more than is predictable from the changes in tracheal diameter, since the tracheal flow velocity is not an interspecific constant.

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Surfactant Activity and the Pressure-Volume Curve of the Respiratory System

10.1007/978-3-030-73387-2_17 ◽

2021 ◽

pp. 235-241

Author(s):

Charles Corey Hardin ◽

Roger G. Spragg ◽

Atul Malhotra

Keyword(s):

Respiratory System ◽

Volume Curve ◽

Pressure Volume Curve ◽

Surfactant Activity

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Lower inflection point and recruitment with PEEP in ventilated patients with acute respiratory failure

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.1.441 ◽

2001 ◽

Vol 91 (1) ◽

pp. 441-450 ◽

Cited By ~ 25

Author(s):

M. Mergoni ◽

A. Volpi ◽

C. Bricchi ◽

A. Rossi

Keyword(s):

Respiratory Failure ◽

Acute Respiratory Failure ◽

Respiratory System ◽

Inflection Point ◽

Simple Method ◽

Lower Inflection Point ◽

Pressure Method ◽

System Pressure ◽

System P ◽

Significant Difference

The lower inflection point (LIP) on the total respiratory system pressure-volume (P-V) curve is widely used to set positive end-expiratory pressure (PEEP) in patients with acute respiratory failure (ARF) on the assumption that LIP represents alveolar recruitment. The aims of this work were to study the relationship between LIP and recruited volume (RV) and to propose a simple method to quantify the RV. In 23 patients with ARF, respiratory system P-V curves were obtained by means of both constant-flow and rapid occlusion technique at four different levels of PEEP and were superimposed on the same P-V plot. The RV was measured as the volume difference at a pressure of 20 cmH2O. A third measurement of the RV was done by comparing the exhaled volumes after the same distending pressure of 20 cmH2O was applied (equal pressure method). RV increased with PEEP ( P < 0.0001); the equal pressure method compares favorably with the other methods ( P = 0.0001 by correlation), although individual data cannot be superimposed. No significant difference was found when RV was compared with PEEP in the group of patients with a LIP ≤5 cmH2O and the group with a LIP >5 cmH2O (76.9 ± 94.3 vs. 61.2 ± 51.3, 267.7 ± 109.9 vs. 209.6 ± 73.9, and 428.2 ± 216.3 vs. 375.8 ± 145.3 ml with PEEP of 5, 10, and 15 cmH2O, respectively). A RV was found even when a LIP was not present. We conclude that the recruitment phenomenon is not closely related to the presence of a LIP and that a simple method can be used to measure RV.

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Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure: impact and clinical fallout through the following 20 years

Intensive Care Medicine ◽

10.1007/s00134-013-3066-x ◽

2013 ◽

Vol 39 (11) ◽

pp. 1909-1915 ◽

Cited By ~ 38

Author(s):

Luciano Gattinoni ◽

Antonio Pesenti ◽

Eleonora Carlesso

Keyword(s):

Respiratory Failure ◽

Acute Respiratory Failure ◽

Body Position ◽

Computed Tomographic

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Respiratory mechanics in adult rats hypercapnic in the neonatal period

Journal of Applied Physiology ◽

10.1152/jappl.1990.68.6.2274 ◽

1990 ◽

Vol 68 (6) ◽

pp. 2274-2279 ◽

Cited By ~ 10

Author(s):

R. Rezzonico ◽

R. D. Gleed ◽

J. P. Mortola

Keyword(s):

Mechanical Properties ◽

Respiratory System ◽

Neonatal Period ◽

Statistical Significance ◽

Lung Compliance ◽

Long Term Effects ◽

Adult Rats ◽

Volume Curve ◽

Pressure Volume Curve ◽

And Control

Because chronic hypoxia in the neonatal period has long-term effects on the mechanical properties of the respiratory system (S. Okubo and J. P. Mortola, J. Appl. Physiol. 66: 1772-1778, 1989), we asked whether similar effects would occur after neonatal exposure to hypercapnia. Three groups of rats were used. The first was exposed to 7% CO2 in normoxia from day 1 to 7 after birth and then returned to normocapnia (NB-CO2). The second was exposed to the same level and duration of hypercapnia from day 36 to 42, i.e., approximately 2 wk after weaning (AD-CO2). The third was raised in normoxia and normocapnia (control). At approximately 50 days, i.e., 1-2 wk after puberty, the passive mechanical properties of the respiratory system, lung, and chest were measured during artificial ventilation in the anesthetized and paralyzed animal. No differences were observed between AD-CO2 and control. NB-CO2 had higher compliance of the lung (approximately +40%) and respiratory system (+32%) than control or AD-CO2. Average values of resistance of the total respiratory system, lung, and chest wall were consistently lower in NB-CO2 than in control and AD-CO2, although the magnitude and statistical significance of the decrease depended on the method of measurement. In a separate group of NB-CO2, lung compliance was measured during spontaneous breathing, and it averaged 34% more than in control. The exponential constant of the deflation quasi-static pressure-volume curve of the liquid-filled lungs was also significantly higher than in control.(ABSTRACT TRUNCATED AT 250 WORDS)

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