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EditorialsAuto-PEEP and Proximal Airway Pressure: Need for Clarification
References (2)
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Relationship of endotracheal tube size to auto-PEEP at high minute ventilation
Respir Care
(1986) - Moore KL. Clinically oriented anatomy: anatomy is. Baltimore, Md: Williams & Wilkins Co; 1980;...
Cited by (4)
Effects of end inspiratory pause with a constant T<inf>i</inf>/T<inf>tot</inf> during mechanical ventilation in normal lungs
1993, Reanimation UrgencesL'influence de la pause de fin d'inspiration (EIP) à fréquence, volume courant, FIO2, et Ti/Ttot constants a été étudiée chez 11 patients, sans antécédent respiratoire, en ventilation contrôlée pour coma séquellaire d'une atteinte cérébrable. Sous neurosédation et curare, ils ont été soumis à 2 rapports Ti/Ttot : un rapport conventionnel Ti/Ttot = 0,35 comprenant une EIP de 0,10, et 20 p. 100 et un rapport allongé Ti/Ttot = 0,5 avec et sans pause de 20 p. 100. L'ordre d'administration de chaque mode ventilatoire a été randomisé. Les mesures des débits et volumes (pneumotachographe de Fleish no 2), des pressions des voies aériennes, des variations de CRF (pléthysmographie d'inductance), des gazométries artérielles et veineuses mêlées, des paramètres hémodynamiques et des distributions des rapports V̇A/Q̇ pulmonaires par la méthode des gaz inertes ont été réalisées. Les différents paramètres ont été comparés par une analyse de variance.
En ventilation avec un rapport Ti/Ttot conventionnel, la suppression de la pause ne provoque qu'une augmentation de l'effet shunt associée à une distribution plus hétérogène de la ventilation. Ces variations sont insuffisantes pour provoquer une modification gazométrique. Par contre, lá suppression du temps de pause provoque une diminution du pic d'insufflation. A Ti/Ttot = 0,5, la suppression du temps de pause provoque un déplacement des courbes de distribution de la ventilation et de la perfusion vers les bas V̇A/Q̇ conduisant à une hypoventilation relative avec augmentation de PaCO2. L'absence de variation de PaO2 est liée à l'augmentation de Pv̄O2 due à l'élévation de Q̇tot en rapport avec la baisse de la pression intrathoracique. Pour les 2 Ti/Ttot, il n'y a pas de variation significative de CRF. Les mêmes résultats gazométriques sont obtenus quand les patients sont soumis à Ti/Ttot = 0,67 sans pause.
En conclusion, en ventilation à rapport Ti/Ttot conventionnel, l'absence de pause est compensée par l'effet bénéfique lié à la diminution des débits d'insufflation ; par contre, lors de l'utilisation de Ti/Ttot allongés, l'EIP est nécessaire afin de permettre une meilleure distribution V̇A/Q̇.
The influence of end inspiratory pause (EIP) without changing tidal volume, frequency, FIO2 and Ti/Ttot was investigated in 11 normal lung patients undergoing mechanical ventilation because of cerebral attack. All patients were anesthetized and paralyzed. Two different Ti/Ttot were used : Ti/Ttot = 0,35 with EIP = 0 p. 100, 10 p. 100, 20 p. 100 versus Ti/Ttot = 0,5 with EIP = 0 p. 100 and 20 p. 100. At each ventilator setting, randomly administered, were obtained : flow and volume (Fleish pneumotachograph no 2), arterial and mixed venous blood gases, hemodynamic data and V̇A/Q̇ ratios distribution using multiple inert gas technique.
In conventionnal ventilation, EIP suppression only provided an increase in venous admixture and a more heterogenous ventilation distribution. These changes were not sufficient to alter significantly blood gases and the benefit was only a lower peak inspiratory pressure. At high insufflation time, EIP suppression provided more deleterious effects by shifting both ventilation and perfusion distribution curves towards low V̇A/Q̇ units. It led to a higher PaCO2 due to a relative hypoventilation. The absence of simultaneous PaO2 change was due to an increase in Pv̄O2 linked to a higher cardiac output allowed by the lower intrathoracic pressure. In both comparison, there was no significant change in FRC. Same results were obtained when Ti/Ttot = 0,67 without EIP.
In conclusion, although EIP was compensated by a lower inspiratory flow in conventional Ti/Ttot, EIP, in high inspiratory time with identical pulmonary volume, was necessary to provide a better V̇A/Q̇ distribution.
The influence of inspiratory flow rate (TI), without changing respiratory frequency, tidal volume, and FIo2, was investigated in 11 normal lungs in patients undergoing mechanical ventilation because of central respiratory failure due to stable coma. The patients were anesthetized and paralyzed. They first received a conventional ventilation (TI = 25 percent, pause = 10 percent) and then, were submitted to four different TI values, randomly administered without any end-inspiratory pause (EIP) (TI = 20 percent; TI = 33 percent; TI = 50 percent; TI = 67 percent). In the middle and at the end of the procedure, a return to basal conditions was introduced. At each ventilator setting, the following were obtained: respiratory flow (Pneumotachograph Fleish No. 2), airway pressure, FRC changes (inductive plethysmography), arterial and mixed venous blood gases, hemodynamic data, and ratios distribution using multiple inert gases technique. EIP suppression provides a significant increase in mismatch (until TI = 50 percent) and in shunt effect (between 3 and 9 percent of cardiac output . The absence of simultaneous PaO2 change is due to increasing P linked to a higher . The shorter the Ti, the higher the PaCO2 connected with a relative alveolar hypoventilation. However, increasing TI without EIP significantly decreases ventilation distribution inequalities. This improvement is concomitant with a rise in FRC (FRC67-FRC20 = 0.340 ± 0.450, p<0.05) without any change in other variables or auto-PEEP production. In summary, in subjects with very slight mechanical lung impairment (peak inspiratory pressure = 20.5 ± 5.3 cm H2O at TI = 20 percent and 15.2 ± 3.3 cm H2O at TI = 67 percent), this study confirms the deleterious effect of EIP suppression and TI decrease. One can compensate for this effect of EIP absence by increasing TI as soon as it reaches TI = 67 percent, ie, inverse ratio ventilation.
We have developed a computerized protocol that provides a systematic approach for management of pressure control-inverse ratio ventilation (PCIRV). The protocols were used for 1,466 h in ten around-the-clock PCIRV evaluations on seven patients with severe adult respiratory distress syndrome (ARDS). Patient therapy was controlled by protocol 95 percent of the time (1,396 of 1,466 h) and 90 percent of the protocol instructions (1,937 of 2,158) were followed by the clinical staff. Of the 221 protocol instructions, 88 (39 percent) not followed were due to invalid PEEPi measurements. Compared with preceding values during CPPV, the expired minute ventilation was reduced by 27 percent during PCIRV while maintaining a pH that was not clinically different (mean difference in pH = 0.02). There was no difference in the PaO2, PEEPi, or the FIO2 between PCIRV and CPPV. The PEEP setting was reduced by 33 percent from 9 ±0.05 to 6 ±0.6 and the I:E ratio increased from 0.64 ± 0.04 to 2.3 ± 0.10. Peak airway pressure was reduced by 24 percent (from 59 ± 1.5 to 45 ±0.6) and mean airway pressure increased by 27 percent (from 22 ±0.8 to 28 ±0.6) in PCIRV. Right atrial and pulmonary artery pressures were higher and cardiac output lower in PCIRV but blood pressure was unchanged. The success of this protocol has demonstrated the feasibility of using PEEPi as a primary control variable for oxygenation. This computerized PCIRV protocol should make the future use of PCIRV less mystifying, simpler, and more systematic.
Peep/f<inf>io2</inf> ardsnet scale grouping of a single ventilator for two patients: Modeling tidal volume response
2020, Respiratory Care