scholarly journals Quantification of Alveolar Recruitment for the Optimization of Mechanical Ventilation Using Quasi-Static Pressure Volume Curve

2018 ◽  
Author(s):  
Mohsen Nabian ◽  
Uichiro Narusawa
Keyword(s):  
Mechanical Ventilation ◽  
Respiratory System ◽  
Distress Syndrome ◽  
Alveolar Recruitment ◽  
System Optimum ◽  
Quantitative Characterization ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Ventilation Setting

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.

Lung volumes and alveolar expansion pattern in immature rabbits treated with serum-diluted surfactant

2004 ◽  
Vol 97 (4) ◽  
pp. 1408-1413 ◽  
Author(s):  
Yongmei Xu ◽  
Tsutomu Kobayashi ◽  
Xiaoguang Cui ◽  
Keisuke Ohta ◽  
Chiharu Kabata ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Distress Syndrome ◽  
Ringer Solution ◽  
Natural Surfactant ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Expansion Pattern

In acute respiratory distress syndrome, mechanical ventilation often induces alveolar overdistension aggravating the primary insult. To examine the mechanism of overdistension, surfactant-deficient immature rabbits were anesthetized with pentobarbital sodium, and their lungs were treated with serum-diluted modified natural surfactant (porcine lung extract; 2 mg/ml, 10 ml/kg). By mechanical ventilation with a peak inspiration pressure of 22.5 cmH2O, the animals had a tidal volume of 14.7 ml/kg (mean), when 2.5 cmH2O positive end-expiratory pressure was added. This volume was similar to that in animals treated with nondiluted modified natural surfactant (24 mg/ml in Ringer solution, 10 ml/kg). However, the lungs fixed at 10 cmH2O on the deflation limbs of the pressure-volume curve had the largest alveolar/alveolar duct profiles (≥48,000 μm2), accounting for 38% of the terminal air spaces, and the smallest (<6,000 μm2), accounting for 31%. These values were higher than those in animals treated with nondiluted modified natural surfactant ( P < 0.05). We conclude that administration of serum-diluted surfactant to immature neonatal lungs leads to patchy overdistension of terminal air spaces, similar to the expansion pattern that may be seen after dilution of endogenous surfactant with proteinaceous edema fluid in acute respiratory distress syndrome.

Alveolar Recruitment in Pulmonary and Extrapulmonary Acute Respiratory Distress Syndrome

2007 ◽  
Vol 106 (2) ◽  
pp. 212-217 ◽  
Author(s):  
Arnaud W. Thille ◽  
Jean-Christophe M. Richard ◽  
Salvatore M. Maggiore ◽  
V Marco Ranieri ◽  
Laurent Brochard
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Tidal Volume ◽  
Distress Syndrome ◽  
Alveolar Recruitment ◽  
High Peep ◽  
Static Compliance ◽  
Volume Curve ◽  
Pressure Volume Curve

Background Alveolar recruitment in response to positive end-expiratory pressure (PEEP) may differ between pulmonary and extrapulmonary acute respiratory distress syndrome (ARDS), and alveolar recruitment values may differ when measured by pressure-volume curve compared with static compliance. Methods The authors compared PEEP-induced alveolar recruitment in 71 consecutive patients identified in a database. Patients were classified as having pulmonary, extrapulmonary, or mixed/uncertain ARDS. Pressure-volume curves with and without PEEP were available for all patients, and pressure-volume curves with two PEEP levels were available for 44 patients. Static compliance was calculated as tidal volume divided by pressure change for tidal volumes of 400 and 700 ml. Recruited volume was measured at an elastic pressure of 15 cm H2O. Results Volume recruited by PEEP (10 +/- 3 cm H2O) was 223 +/- 111 ml in the pulmonary ARDS group (29 patients), 206 +/- 164 ml in the extrapulmonary group (16 patients), and 242 +/- 176 ml in the mixed/uncertain group (26 patients) (P = 0.75). At high PEEP (14 +/- 2 cmH2O, 44 patients), recruited volumes were also similar (P = 0.60). With static compliance, recruitment was markedly underestimated and was dependent on tidal volume (226 +/- 148 ml using pressure-volume curve, 95 +/- 185 ml for a tidal volume of 400 ml, and 23 +/- 169 ml for 700 ml; P &lt; 0.001). Conclusion In a large sample of patients, classification of ARDS was uncertain in more than one third of patients, and alveolar recruitment was similar in pulmonary and extrapulmonary ARDS. PEEP levels should not be determined based on cause of ARDS.

scholarly journals Response to Recruitment Maneuver Influences Net Alveolar Fluid Clearance in Acute Respiratory Distress Syndrome

2007 ◽  
Vol 106 (5) ◽  
pp. 944-951 ◽  
Author(s):  
Jean-Michel Constantin ◽  
Sophie Cayot-Constantin ◽  
Laurence Roszyk ◽  
Emmanuel Futier ◽  
Vincent Sapin ◽  
...  
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Distress Syndrome ◽  
Recruitment Maneuver ◽  
Alveolar Recruitment ◽  
Alveolar Fluid Clearance ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Before And After

Background Alveolar fluid clearance is impaired in the majority of patients with acute respiratory distress syndrome (ARDS). Experimental studies have shown that a reduction of tidal volume increases alveolar fluid clearance. This study was aimed at assessing the impact of the response to a recruitment maneuver (RM) on net alveolar fluid clearance. Methods In 15 patients with ARDS, pulmonary edema fluid and plasma protein concentrations were measured before and after an RM, consisting of a positive end-expiratory pressure maintained 10 cm H2O above the lower inflection point of the pressure-volume curve during 15 min. Cardiorespiratory parameters were measured at baseline (before RM) and 1 and 4 h later. RM-induced lung recruitment was measured using the pressure-volume curve method. Net alveolar fluid clearance was measured by measuring changes in bronchoalveolar protein concentrations before and after RM. Results In responders, defined as patients showing an RM-induced increase in arterial oxygen tension of 20% of baseline value or greater, net alveolar fluid clearance (19 +/- 13%/h) and significant alveolar recruitment (113 +/- 101 ml) were observed. In nonresponders, neither net alveolar fluid clearance (-24 +/- 11%/h) nor alveolar recruitment was measured. Responders and nonresponders differed only in terms of lung morphology: Responders had a diffuse loss of aeration, whereas nonresponders had a focal loss of aeration, predominating in the lower lobes. Conclusion In the absence of alveolar recruitment and improvement in arterial oxygenation, RM decreases the rate of alveolar fluid clearance, suggesting that lung overinflation may be associated with epithelial dysfunction.

Letters to the Editor

1998 ◽  
Vol 85 (5) ◽  
pp. 1998-2000
Author(s):  
Hans-G. Sonander
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Goodness Of Fit ◽  
Distress Syndrome ◽  
Letters To The Editor ◽  
Mechanically Ventilated ◽  
Pulmonary Pressure ◽  
Volume Curve ◽  
Pressure Volume Curve

The following is the abstract of the article discussed in the subsequent letter: Venegas, José G., R. Scott Harris, and Brett A. Simon. A comprehensive equation for the pulmonary pressure-volume curve. J. Appl. Physiol. 84(1): 389–395, 1998.—Quantification of pulmonary pressure-volume (P-V) curves is often limited to calculation of specific compliance at a given pressure or the recoil pressure (P) at a given volume (V). These parameters can be substantially different depending on the arbitrary pressure or volume used in the comparison and may lead to erroneous conclusions. We evaluated a sigmoidal equation of the form, V = a + b[1 +  e −(P− c)/ d ]−1, for its ability to characterize lung and respiratory system P-V curves obtained under a variety of conditions including normal and hypocapnic pneumoconstricted dog lungs ( n = 9), oleic acid-induced acute respiratory distress syndrome ( n = 2), and mechanically ventilated patients with acute respiratory distress syndrome ( n = 10). In this equation, a corresponds to the V of a lower asymptote, b to the V difference between upper and lower asymptotes, c to the P at the true inflection point of the curve, and d to a width parameter proportional to the P range within which most of the V change occurs. The equation fitted equally well inflation and deflation limbs of P-V curves with a mean goodness-of-fit coefficient ( R 2) of 0.997 ± 0.02 (SD). When the data from all analyzed P-V curves were normalized by the best-fit parameters and plotted as (V −  a)/ b vs. (P −  c)/ d, they collapsed into a single and tight relationship ( R 2 = 0.997). These results demonstrate that this sigmoidal equation can fit with excellent precision inflation and deflation P-V curves of normal lungs and of lungs with alveolar derecruitment and/or a region of gas trapping while yielding robust and physiologically useful parameters.

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