Dynamic Airway Pressure Research Articles

Ability of dynamic airway pressure curve profile and elastance for positive end-expiratory pressure titration

To evaluate the ability of three indices derived from the airway pressure curve for titrating positive end-expiratory pressure (PEEP) to minimize mechanical stress while improving lung aeration assessed by computed tomography (CT). Prospective, experimental study. University research facilities. Twelve pigs. Animals were anesthetized and mechanically ventilated with tidal volume of 7 ml kg(-1). In non-injured lungs (n = 6), PEEP was set at 16 cmH(2)O and stepwise decreased until zero. Acute lung injury was then induced either with oleic acid (n = 6) or surfactant depletion (n = 6). A recruitment maneuver was performed, the PEEP set at 26 cmH(2)O and decreased stepwise until zero. CT scans were obtained at end-expiratory and end-inspiratory pauses. The elastance of the respiratory system (Ers), the stress index and the percentage of volume-dependent elastance (%E (2)) were estimated. In non-injured and injured lungs, the PEEP at which Ers was lowest (8-4 and 16-12 cmH(2)O, respectively) corresponded to the best compromise between recruitment/hyperinflation. In non-injured lungs, stress index and %E (2) correlated with tidal recruitment and hyperinflation. In injured lungs, stress index and %E (2) suggested overdistension at all PEEP levels, whereas the CT scans evidenced tidal recruitment and hyperinflation simultaneously. During ventilation with low tidal volumes, Ers seems to be useful for guiding PEEP titration in non-injured and injured lungs, while stress index and %E (2) are useful in non-injured lungs only. Our results suggest that Ers can be superior to the stress index and %E (2) to guide PEEP titration in focal loss of lung aeration.

Influence of tongue muscle contraction and dynamic airway pressure on velopharyngeal volume in the rat

The mammalian pharynx is a collapsible tube that narrows during inspiration as transmural pressure becomes negative. The velopharynx (VP), which lies posterior to the soft palate, is considered to be one of the most collapsible pharyngeal regions. I tested the hypothesis that negative transmural pressure would narrow the VP, and that electrical stimulation of extrinsic tongue muscles would reverse this effect. Pressure (-6, -3, 3, and 6 cmH2O) was applied to the isolated pharyngeal airway of anesthetized rats that were positioned in a 4.7-T MRI scanner. The volume of eight axial slices encompassing the length of the VP was computed at each level of pressure, with and without bilateral hypoglossal nerve stimulation (0.1-ms pulse, one-third maximum force, 80 Hz). Negative pressure narrowed the VP, and either whole hypoglossal nerve stimulation (coactivation of protrudor and retractor muscles) or medial nerve branch stimulation (independent activation of tongue protrudor muscles) reversed this effect, with the greatest impact in the caudal one-third of the VP. The dilating effects of medial branch stimulation were slightly larger than whole nerve stimulation. Positive pressure dilated the VP, but tongue muscle contraction did not cause further dilation under these conditions. I conclude that the narrowest and most collapsible segment of the rat pharynx is in the caudal VP, posterior to the tip of the soft palate. Either coactivation of protrudor and retractor muscles or independent contraction of protrudor muscles caused dilation of this region, but the latter was slightly more effective.

Analysis of the dynamic airway pressure concavity and distribution of lung aeration in piglets

Analysis of the dynamic airway pressure concavity and distribution of lung aeration in piglets

Influence of respiratory efforts on b2-agonist induced bronchodilation in mechanically ventilated COPD patients: A prospective clinical study

Several in vitro studies have shown that at similar tidal volume (VT), bronchodilator delivery to target sites is significantly lower during controlled mechanical ventilation (CMV) than that during simulated spontaneous breathing. However, the influence of active respiratory efforts on the magnitude of b2-agonist induced bronchodilation in mechanically ventilated patients has not been examined. To examine the influence of controlled and assisted modes of ventilatory support on the bronchodilative effect induced by b2-agonists administered with a metered dose inhaler (MDI) and a spacer device in a homogeneous group of mechanically ventilated patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). Prospective clinical study. Ten mechanically ventilated patients with acute exacerbation of COPD were prospectively randomized to receive 4 puffs of salbutamol (S, 100 micro g/puff) either with volume-controlled (VC) or pressure-support (PS) ventilation. On PS the pressure level was such that VT was comparable between ventilatory modes. After a 6-h washout period, patients were crossed-over to receive the drug by the alternative mode of ventilation. Static and dynamic airway pressures, minimum (R(int)) and maximum (R(rs)) inspiratory resistance, the difference between R(rs) and R(int) (DeltaR), end-inspiratory static compliance of the respiratory system (C(rs)), intrinsic positive end-expiratory pressure (PEEP(i)) and heart rate (HR) were measured before and at 15, 30, 60, 120, 180 and 240 min after S administration. S caused a significant decrease in dynamic and static airway pressures, PEEP(i), R(int) and R(rs). These changes were not influenced by the ventilatory mode and were evident at 15, 30, 60 and 120 min after S. HR, C(rs) and DeltaR did not change after S administration. Considering the use of propofol with its presumed bronchodilative properties as a shortcoming of our study, it is concluded that the magnitude of bronchodilation induced by salbutamol delivered by an MDI and a spacer device in mechanically ventilated COPD patients is not affected by the presence or absence of active respiratory efforts.

A prototype of a liquid ventilator using a novel hollow-fiber oxygenator in a rabbit model.

A functional total liquid ventilator should be simple in design to minimize operating errors and have a low priming volume to minimize the amount of perfluorocarbon needed. Closed system circuits using a membrane oxygenator have partially met these requirements but have high resistance to perfluorocarbon flow and high priming volume. To further this goal, a single piston prototype ventilator with a low priming volume and a new high-efficiency hollow-fiber oxygenator in a circuit with a check valve flow control system was developed. Prospective, controlled animal laboratory study. Research facility at a university medical center. Seven anesthetized, paralyzed, normal New Zealand rabbits The prototype oxygenator, consisting of cross-wound silicone hollow fibers with a surface area of 1.5 m2 with a priming volume of 190 mL, was tested in a bench-top model followed by an in vivo rabbit model. Total liquid ventilation was performed for 3 hrs with 20 mL.kg(-1) initial fill volume, 17.5-20 mL.kg(-1) tidal volume, respiratory rate of 5 breaths/min, inspiratory/expiratory ratio 1:2, and countercurrent sweep gas of 100% oxygen. Bench top experiments demonstrated 66-81% elimination of CO2 and 0.64-0.76 mL.min(-1) loss of perfluorocarbon across the fibers. No significant changes in PaCO2 and PaO2 were observed. Dynamic airway pressures were in a safe range in which ventilator lung injury or airway closure was unlikely (3.6 +/- 0.5 and -7.8 +/- 0.3 cm H2O, respectively, for mean peak inspiratory pressure and mean end expiratory pressure). No leakage of perfluorocarbon was noted in the new silicone fiber gas exchange device. Estimated in vivo perfluorocarbon loss from the device was 1.2 mL.min(-1). These data demonstrate the ability of this novel single-piston, nonporous hollow silicone fiber oxygenator to adequately support gas exchange, allowing successful performance of total liquid ventilation.

Total Liquid Ventilation: Dynamic Airway Pressure and the Development of Expiratory Flow Limitation

Expiratory flow limitation occurs during total liquid ventilation (TLV), and is characterized by the sudden development of excessively negative intratracheal pressures without increases in flow. The purpose of this study was to identify a dynamic signal for the servoregulation of expiratory flow (Ve), by determining the range of dynamic intratracheal pressures [P(T)], which mark the onset of flow limitation during liquid expiration, where choke occurs at the critical pressure (Pc). The lungs of rabbits were filled with perflurocarbon to an end-inspiratory lung volume (EILV) of 20, 30, or 40cc/kg and connected to a piston driven liquid ventilator, which removed perfluorocarbon at a rate (Vs) of 2.5, 5.0, or 7.5 ml/s. Nine animals per EILV group were used (27 animals total), and within each EILV group each (Vs) was used three times. P(T) and (Ve) (T) were measured at the tracheostomy tube, and dP/dT was calculated from P(T). Pc was determined within each EILV/(Vs) group by examining the average dP/dT curve for the first significant change from baseline. Pc ranged from -6.02 +/- 1.83 to -9.02 +/- 3.2 mm Hg. In general, the higher the EILV, the more negative the Pc. We conclude that Pc during TLV varies within a limited range in rabbits. These data may be used to maximize expired volume during TLV by sequentially tapering flow rates as this critical range of pressures is approached.

Bronchodilator delivery by metered-dose inhaler in mechanically ventilated COPD patients: influence of tidal volume

The delivery of bronchodilator drugs with metered-dose inhaler (MDI) and a spacer in mechanically ventilated patients has become a widespread practice. However, the various ventilator settings that influence the efficacy of MDI are not well established. The tidal volume (VT) during drug delivery has been suggested as one of the factors that might increase the effectiveness of this therapy. To test this, the effect of two different VT on the bronchodilation induced by beta 2-agonists administered with MDI and a spacer in a group of mechanically ventilated patients with chronic obstructive pulmonary disease (COPD) was examined. Nine patients with COPD, mechanically ventilated on volume-controlled mode, were prospectively randomised to receive six puffs of salbutamol (S, 100 micrograms/puff) either with a VT of 8 ml/kg (normal VT, 582 +/- 85) or with a VT of 12 ml/kg (high VT, 912 +/- 137). With both modes inspiratory flow was identical. S was administered with an MDI adapted to the inspiratory limb of the ventilator circuit using an aerosol cloud enhancer spacer. After a 6-h washout, patients were crossed-over to receive S by the alternative mode of administration. Static and dynamic airway pressures, minimum (Rint) and maximum (Rrs) inspiratory resistance, the difference between Rrs and Rint (delta R), static end-inspiratory respiratory system compliance (Cst,rs), intrinsic positive end-expiratory pressure (PEEPi) and heart rate (HR) were measured before and at 15, 30 and 60 min after S. S caused a significant decrease in dynamic and static airway pressures, PEEPi, Rint and Rrs. These changes were not influenced by VT and were evident at 15, 30 and 60 min after S. With normal and high VT, Cst,rs, delta R and HR did not change after S. We conclude that S delivered with an MDI and a spacer device induces significant bronchodilation in mechanically ventilated patients with COPD, the magnitude of which is not affected by at least a 50% increase in VT. These results do not support the VT manipulations when bronchodilators are administered in adequate doses during controlled mechanical ventilation.

Test of wave-speed theory of flow limitation in elastic tubes.

ARTICLESTest of wave-speed theory of flow limitation in elastic tubesE. A. Elliott, and S. V. DawsonE. A. Elliott, and S. V. DawsonPublished Online:01 Sep 1977https://doi.org/10.1152/jappl.1977.43.3.516MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByMimicking a flow-limited human upper airway using a collapsible tube: relationships between flow patterns and pressures in a respiratory modelKaixian Zhu, Ramon Farré, Ira Katz, Sébastien Hardy, and Pierre Escourrou22 August 2018 | Journal of Applied Physiology, Vol. 125, No. 2Relation of concavity in the expiratory flow-volume loop to dynamic hyperinflation during exercise in COPDRespiratory Physiology & Neurobiology, Vol. 234State-dependent and reflex drives to the upper airway: basic physiology with clinical implicationsRichard L. Horner, Stuart W. Hughes, and Atul Malhotra*1 February 2014 | Journal of Applied Physiology, Vol. 116, No. 3Liquid VentilationTotal Liquid Ventilation: Dynamic Airway Pressure and the Development of Expiratory Flow LimitationASAIO Journal, Vol. 50, No. 5Assessment of the development of choked flow during total liquid ventilationCritical Care Medicine, Vol. 32, No. 1The Male Predisposition to Pharyngeal CollapseAmerican Journal of Respiratory and Critical Care Medicine, Vol. 166, No. 10Mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs. I. StaticsStephanie A. Tuck, and John E. Remmers1 June 2002 | Journal of Applied Physiology, Vol. 92, No. 6Mechanical properties of the passive pharynx in Vietnamese pot-bellied pigs. II. DynamicsStephanie A. Tuck, and John E. Remmers1 June 2002 | Journal of Applied Physiology, Vol. 92, No. 6Interdependence of flow between lobes reduces maximal emptying postresection in dogsDavid Ewing-Bui, and Steven N. Mink1 January 2002 | Journal of Applied Physiology, Vol. 92, No. 1Gender Differences in the Expression of Sleep-Disordered BreathingChest, Vol. 120, No. 5Modeling expiratory flow from excised tracheal tube lawsNikolai Aljuri, Lutz Freitag, and José G. Venegas1 November 1999 | Journal of Applied Physiology, Vol. 87, No. 5Effect of expiratory flow limitation on respiratory mechanical impedance: a model studyR. Peslin, R. Farré, M. Rotger, and D. Navajas1 December 1996 | Journal of Applied Physiology, Vol. 81, No. 6Air trapping in the lungs during cardiopulmonary resuscitation in dogs. A mechanism for generating changes in intrathoracic pressure.Circulation Research, Vol. 65, No. 4The effects of wall thickness, axial strain and end proximity on the pressure-area relation of collapsible tubesJournal of Biomechanics, Vol. 20, No. 9A consideration of density dependence of maximum expiratory flowRespiration Physiology, Vol. 52, No. 1Methods of study of airway smooth muscle and its physiologyPharmacology & Therapeutics, Vol. 7, No. 2 More from this issue > Volume 43Issue 3September 1977Pages 516-522 Copyright & PermissionsCopyright © 1977 the American Physiological Societyhttps://doi.org/10.1152/jappl.1977.43.3.516PubMed914722History Published online 1 September 1977 Published in print 1 September 1977 Metrics

Demand-controlled liquid ventilation of the lungs.

Demand-controlled liquid ventilation of the lungs.

Maximum expiratory flow and estimated CO 2 elimination in liquid-ventilated dogs' lungs.

ArticleMaximum expiratory flow and estimated CO 2 elimination in liquid-ventilated dogs' lungs.W H Schoenfisch, and J A KylstraW H Schoenfisch, and J A KylstraPublished Online:01 Jul 1973https://doi.org/10.1152/jappl.1973.35.1.117MoreSectionsPDF (1002 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByLiquid Ventilation in the Management of Preterm Infants28 August 2021 | Current Stem Cell Reports, Vol. 7, No. 3Liquid VentilationA Regulator for Pressure-Controlled Total-Liquid VentilationIEEE Transactions on Biomedical Engineering, Vol. 57, No. 9Effects of Respiratory Rate and Tidal Volume on Gas Exchange in Total Liquid VentilationASAIO Journal, Vol. 55, No. 4Expiratory Flow Limitation during Gravitational Drainage of Perfluorocarbons from Liquid-Filled LungsASAIO Journal, Vol. 51, No. 6Flow Limitation in Liquid-Filled Lungs: Effects of Liquid Properties6 February 2005 | Journal of Biomechanical Engineering, Vol. 127, No. 4A prototype of a liquid ventilator using a novel hollow-fiber oxygenator in a rabbit modelCritical Care Medicine, Vol. 32, No. 10Total Liquid Ventilation: Dynamic Airway Pressure and the Development of Expiratory Flow LimitationASAIO Journal, Vol. 50, No. 5Liquid VentilationAssessment of the development of choked flow during total liquid ventilationCritical Care Medicine, Vol. 32, No. 1Effect of ventilatory variables on gas exchange and hemodynamics during total liquid ventilation in a rat modelCritical Care Medicine, Vol. 31, No. 7Perfluorocarbon Enhanced Gas ExchangeAmerican Journal of Respiratory and Critical Care Medicine, Vol. 164, No. 1Development and application of a double-piston configured, total-liquid ventilatory support deviceCritical Care Medicine, Vol. 28, No. 5Liquid-assisted ventilation: An alternative respiratory modalityPediatric Pulmonology, Vol. 26, No. 1Physiologic, Biochemical, and Histologic Correlates Associated with Tidal Liquid VentilationPediatric Research, Vol. 43, No. 1Comparison of perfluorochemical fluids used for liquid ventilation: Effect of endotracheal tube flow resistancePediatric Pulmonology, Vol. 23, No. 6Shunt and ventilation-perfusion distribution during partial liquid ventilation in healthy pigletsElisabeth A. Mates, Jacob Hildebrandt, J. Craig Jackson, Peter Tarczy-Hornoch, and Michael P. Hlastala1 March 1997 | Journal of Applied Physiology, Vol. 82, No. 3Gas Exchange during Gas and Liquid Ventilation1 November 1996 | Journal of Intensive Care Medicine, Vol. 11, No. 6Liquid ventilation: An alternative ventilation strategy for management of neonatal respiratory distressEuropean Journal of Pediatrics, Vol. 155, No. S2Improvement of Gas Exchange, Pulmonary Function, and Lung Injury With Partial Liquid VentilationChest, Vol. 108, No. 2Diving physiology and pathophysiologyClinical Physiology, Vol. 14, No. 6Liquid ventilationPediatric Pulmonology, Vol. 14, No. 2Pathophysiology of CoughClinics in Chest Medicine, Vol. 8, No. 2Man in the Ocean Environment: Physiological Factors More from this issue > Volume 35Issue 1July 1973Pages 117-21 https://doi.org/10.1152/jappl.1973.35.1.117PubMed4716145History Published online 1 July 1973 Published in print 1 July 1973 Metrics