A Mathematical Model of Mean Airway Pressure Based Upon Positive End-Expiratory Pressure, I:E Ratio, and Plateau Pressure

2003 ◽  
Vol 3 (4) ◽  
pp. 131-139 ◽  
Author(s):  
Glen M. Atlas
Keyword(s):  
Mathematical Model ◽  
Airway Pressure ◽  
Plateau Pressure ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure

Determinants of gas flow through a bronchopleural fistula

1989 ◽  
Vol 67 (4) ◽  
pp. 1591-1596 ◽  
Author(s):  
M. C. Walsh ◽  
W. A. Carlo
Keyword(s):  
Airway Pressure ◽  
Gas Flow ◽  
Bronchopleural Fistula ◽  
Peak Inspiratory Pressure ◽  
Intrathoracic Pressure ◽  
Transpulmonary Pressure ◽  
Inspiratory Pressure ◽  
Positive End Expiratory Pressure ◽  
Inspiratory Time ◽  
Mean Airway Pressure

To assess the determinants of bronchopleural fistula (BPF) flow, we used a surgically created BPF to study 15 anesthetized intubated mechanically ventilated New Zealand White rabbits. Mean airway pressure and intrathoracic pressure were evaluated independently. Mean airway pressure was varied (8, 10, or 12 cmH2O) by independent manipulations of either peak inspiratory pressure, positive end-expiratory pressure, or inspiratory time. Intrathoracic pressure was varied from 0 to -40 cmH2O. BPF flow varied directly with mean airway pressure (P less than 0.001). However, at constant mean airway pressure, BPF flow was not influenced independently by changes in peak inspiratory pressure, positive end-expiratory pressure, or inspiratory time. Resistance of the BPF increased as intrathoracic pressure became more negative. Despite increased resistance, BPF flow also increased. BPF resistance was constant over the range of mean airway (P less than 0.01) pressures investigated. Our data document the influence of mean airway pressure and intrathoracic pressure on BPF flow and suggest that manipulations which reduce transpulmonary pressure will decrease BPF flow.

Optimal Mean Airway Pressure during High-frequency Oscillation

2001 ◽  
Vol 94 (5) ◽  
pp. 862-869 ◽  
Author(s):  
Sven Goddon ◽  
Yuji Fujino ◽  
Jonathan M. Hromi ◽  
Robert M. Kacmarek
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
High Frequency ◽  
Airway Pressure ◽  
Distress Syndrome ◽  
High Frequency Oscillation ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Frequency Oscillation ◽  
Initial Injury

Background A number of groups have recommended setting positive end-expiratory pressure during conventional mechanical ventilation in adults at 2 cm H2O above the lower corner pressure (P(CL)) of the inspiratory pressure-volume (P-V) curve of the respiratory system. No equivalent recommendations for the setting of the mean airway pressure (Paw) during high-frequency oscillation (HFO) exist. The authors questioned if the Paw resulting in the best oxygenation without hemodynamic compromise during HFO is related to the static P-V curve in a large animal model of acute respiratory distress syndrome. Methods Saline lung lavage was performed in seven sheep (28+/-5 kg, mean +/- SD) until the arterial oxygen partial pressure/fraction of inspired oxygen ratio decreased to 85+/-27 mmHg at a positive end-expiratory pressure of 5 cm H2O (initial injury). The PCL (20+/-1 cm H2O) on the inflation limb and the point of maximum curvature change (PMC; 26+/-1 cm H2O) on the deflation limb of the static P-V curve were determined. The sheep were subjected to four 1-h cycles of HFO at different levels of Paw (P(CL) + 2, + 6, + 10, + 14 cm H2O), applied in random order. Each cycle was preceded by a recruitment maneuver at a sustained Paw of 50 cm H2O for 60 s. Results High-frequency oscillation with a Paw of 6 cm H2O above P(CL) (P(CL) + 6) resulted in a significant improvement in oxygenation (P < 0.01 vs. initial injury). No further improvement in oxygenation was observed with higher Paw, but cardiac output decreased, pulmonary vascular resistance increased, and oxygen delivery decreased at Paw greater than P(CL) + 6. The PMC on the deflation limb of the P-V curve was equal to the P(CL) + 6 (r = 0.77, P < 0.05). Conclusion In this model of acute respiratory distress syndrome, optimal Paw during HFO is equal to P(CL) + 6, which correlates with the PMC.

Effects of Inverse Ratio Ventilation versus  Positive End-expiratory Pressure on Gas Exchange and Gastric Intramucosal Pco2and pH under Constant Mean Airway Pressure in Acute Respiratory Distress Syndrome

2001 ◽  
Vol 95 (5) ◽  
pp. 1182-1188 ◽  
Author(s):  
Chung-Chi Huang ◽  
Mei-Ju Shih ◽  
Ying-Huang Tsai ◽  
Yu-Chen Chang ◽  
Thomas C. Y. Tsao ◽  
...  
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Gas Exchange ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Airway Pressure ◽  
Distress Syndrome ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Inverse Ratio Ventilation ◽  
Pressure Controlled

Background In patients with acute respiratory distress syndrome, whether inverse ratio ventilation differs from high positive end-expiratory pressure (PEEP) for gas exchange under a similar mean airway pressure has not been adequately examined. The authors used arterial oxygenation, gastric intramucosal partial pressure of carbon dioxide (PiCO(2)), and pH (pHi) to assess whether pressure-controlled inverse ratio ventilation (PC-IRV) offers more benefits than pressure-controlled ventilation (PCV) with PEEP. Methods Seventeen acute respiratory distress syndrome patients were enrolled and underwent mechanical ventilation with a PCV inspiratory-to-expiratory ratio of 1:2, followed by PC-IRV 1:1 initially. Then, they were randomly assigned to receive PC-IRV 2:1, then 4:1 or 4:1, and then 2:1, alternately. The baseline setting of PCV 1:2 was repeated between the settings of PC-IRV 2:1 and 4:1. Mean airway pressure and tidal volume were kept constant by adjusting the levels of peak inspiratory pressure and applied PEEP. In each ventilatory mode, hemodynamics, pulmonary mechanics, arterial and mixed venous blood gas analysis, PiCO(2), and pHi were measured after a 1-h period of stabilization. Results With a constant mean airway pressure, PC-IRV 2:1 and 4:1 decreased arterial and mixed venous oxygenation as compared with baseline PCV 1:2. Neither the global oxygenation indices with oxygen delivery and uptake nor PiCO(2) and pHi were improved by PC-IRV. During PC-IRV, applied PEEP was lower, and auto-PEEP was higher. Conclusion When substituting inverse ratio ventilation for applied PEEP to keep mean airway pressure constant, PC-IRV does not contribute more to better gas exchange and gastric intramucosal PiCO(2) and pHi than does PCV 1:2 for acute respiratory distress syndrome patients, regardless of the inspiratory-to-expiratory ratios.

Mean airway pressure vs. positive end-expiratory pressure during mechanical ventilation

1985 ◽  
Vol 13 (1) ◽  
pp. 34-37 ◽  
Author(s):  
ANTONIO PESENTI ◽  
ROBERTO MARCOLIN ◽  
PAOLO PRATO ◽  
MASSIMO BORELLI ◽  
ANNA RIBONI ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Airway Pressure ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure

Effects of Alterations of Inspiratory and Expiratory Pressures and lnspiratory/Expiratory Ratios on Mean Airway Pressure, Blood Gases, and Intracranial Pressure

PEDIATRICS ◽  
1981 ◽  
Vol 67 (4) ◽  
pp. 474-481
Author(s):  
A. R. Stewart ◽  
N. N. Finer ◽  
K. L. Peters
Keyword(s):  
Intracranial Pressure ◽  
Significant Relationship ◽  
Airway Pressure ◽  
Peak Inspiratory Pressure ◽  
Blood Gases ◽  
Hyaline Membrane Disease ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Hyaline Membrane ◽  
End Tidal

Twenty neonates requiring mechanical ventilation for respiratory failure, including 13 with hyaline membrane disease, were studied to assess the effects of alterations in ventilator settings on mean airway pressure (MAP), blood gases, and intracranial pressure (ICP). The study involved random alterations in peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), and inspiratory/expiratory ratio while MAP, Pao2, ICP, and end-tidal Pco2 were continuously monitored. The results showed a significant relationship between MAP and Pao2 that was expressed as the change in Pao2 per millimeter of mercury change in MAP (ΔPa02/ΔMAP) with a mean ΔPao2/ΔMAP of 4.92. The ΔPao2/ΔMAP was highest for changes in PEEP (6.08), followed by PIP (5.07), and inspiratory/expiratory ratio (1.9). There was a significant relationship between alterations in PEEP and PIP vs Paco2 and pH. Increases in PEEP and decreases in PIP resulted in an elevated Paco2 and a lowered pH, and decreases in PEEP and increases in PIP resulted in a decreased Paco2 and an elevated pH. There was no significant relationship between MAP and ICP, but there was a significant association between ΔICP and ΔPaco2 during alterations in PIP (r = .64, P <.001). Increases in PEEP will lead to the greatest increase in Pao2 per change in MAP, followed by increases in PIP and inspiratory /expiratory ratio using a pressure-limited ventilator.

scholarly journals The effects of positive end-expiratory pressure in alveolar recruitment during mechanical ventilation in pigs

2008 ◽  
Vol 23 (4) ◽  
pp. 310-314 ◽  
Author(s):  
Gabriel Ribeiro Madke ◽  
Eduardo Sperb Pilla ◽  
Pablo Geraldo Sanchez ◽  
Rafael Foernges ◽  
Gustavo Grün ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Venous Return ◽  
Respiratory Mechanic ◽  
Plateau Pressure ◽  
Alveolar Recruitment ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Volume Controlled Ventilation ◽  
Volume Controlled ◽  
Lateral Thoracotomy

PURPOSE: To evaluate the effects of alveolar recruitment based on mean airway pressure (MAP) on pig lungs submitted to thoracotomy through blood gas exchange and hemodynamic parameters. METHODS: Twelve pigs weighting approximately 25Kg were intubated and ventilated on volume controlled ventilation (tidal volume 10ml/Kg, respiratory rate 16min, FiO2 1.0, inspiratory:expiratory ratio 1:2, PEEP 5cmH2O). The animals were then randomized into two groups: control and left lateral thoracotomy. The PEEP was increased at each 15-minute intervals to reach a MAP of 15, 20 and 25cmH2O, respectively. Hemodynamic, gas exchange and respiratory mechanic data were measured immediately before each PEEP change. RESULTS: There were no significant differences between both groups in all parameters analyzed (P=1.0). The PaO2, PaCO2, MAP, PAP and plateau pressure were significantly worse at MAP of 25cmH2O, when compared with the other values of MAP (P=0.001, P=0.039, P=0.001, P=0.016 e P=0.027, respectively). The best pulmonary performance according to the analyzed parameters was observed at MAP of 20cmH2O. CONCLUSION: PEEP adjusted to MAP of 20cmH2O resulted in best arterial oxygenation, without compromising the venous return, as opposed to MAP of 25cmH2O, which caused deterioration of gas exchange, hemodynamics and respiratory mechanic.

Sign in / Sign up

Export Citation Format

Share Document