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Schumann S, Vimlati L, Kawati R, Guttmann J, Lichtwarck-Aschoff M. Cardiogenic oscillations to detect intratidal derecruitment and overdistension in a porcine model of healthy and atelectatic lungs. Br J Anaesth 2018; 121:928-935. [PMID: 30236255 DOI: 10.1016/j.bja.2018.02.068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 02/09/2018] [Accepted: 03/26/2018] [Indexed: 10/17/2022] Open
Abstract
BACKGROUND Low positive end-expiratory pressure (PEEP) can result in alveolar derecruitment, and high PEEP or high tidal volume (VT) in lung overdistension. We investigated cardiogenic oscillations (COS) in the airway pressure signal to investigate whether these oscillations can assess unfavourable intratidal events. COS induce short instantaneous compliance increases within the pressure-volume curve, and consequently in the compliance-volume curve. We hypothesised that increases in COS-induced compliance reflect non-linear intratidal respiratory system mechanics. METHODS In mechanically ventilated anaesthetised pigs with healthy (n=13) or atelectatic (n=12) lungs, pressure-volume relationships and the ECG were acquired at a PEEP of 0, 5, 10, and 15 cm H2O. During inspiration, the peak compliance of successive COS (CCOS) was compared with intratidal respiratory system compliance (CRS) within incremental volume steps up to the full VT of 12 ml kg-1. We analysed whether CCOS variation corresponded with systolic arterial pressure variation. RESULTS CCOS-volume curves showed characteristic intratidal patterns depending on the PEEP level and on atelectasis. Increasing CRS- or CCOS-volume patterns were associated with intratidal derecruitment with low PEEP, and decreasing patterns above 6 ml kg-1 and high PEEP showed overdistension. CCOS was not associated with systolic arterial pressure variations. CONCLUSIONS Heartbeat-induced oscillations within the course of the inspiratory pressure-volume curve reflect non-linear intratidal respiratory system mechanics. The analysis of these cardiogenic oscillations can be used to detect intratidal derecruitment and overdistension and, hence, to guide PEEP and VT settings that are optimal for respiratory system mechanics.
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Affiliation(s)
- S Schumann
- Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany.
| | - L Vimlati
- Department of Surgical Sciences, Anesthesiology and Intensive Care Medicine, Uppsala University, Uppsala, Sweden
| | - R Kawati
- Department of Surgical Sciences, Anesthesiology and Intensive Care Medicine, Uppsala University, Uppsala, Sweden
| | - J Guttmann
- Department of Anesthesiology and Critical Care, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - M Lichtwarck-Aschoff
- Department of Surgical Sciences, Anesthesiology and Intensive Care Medicine, Uppsala University, Uppsala, Sweden
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Guttmann J, Eberhard L, Fabry B, Zappe D, Bernhard H, Lichtwarck-Aschoff M, Adolph M, Wolff G. Determination of volume-dependent respiratory system mechanics in mechanically ventilated patients using the new SLICE method. Technol Health Care 2014; 2:175-91. [PMID: 25274082 DOI: 10.3233/thc-1994-2302] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In patients mechanically ventilated for severe respiratory failure, respiratory system mechanics are non-linear, i.e., volume-dependent. We present a new computer-based multipoint method for simultaneously determining volume-dependent dynamic compliance and resistance. Our method is based on continuously determined tracheal pressure (Ptrach). Tidal volume is subdivided into six volume slices of equal size. One compliance value (intrinsic PEEP considered) and one resistance value are determined for each volume slice by applying of the least-squares-fit (LSF) analysis based on the linear RC-model; we therefore call this the SLICE method. The method gives the course of dynamic compliance and resistance within the tidal volume. The method was evaluated using physical models of the respiratory system with linear and non-linear passive mechanical properties. The relative error of the method is smaller than ±5%. The method needs no special ventilatory pattern. Using data from 14 patients mechanically ventilated for adult respiratory distress syndrome (ARDS) we found a very good correspondence between the measured end-inspiratory airway pressure (Paw,Ie) and the end-inspiratory alveolar pressure (Palv,Ie) calculated from the dynamic compliance values determined with the SLICE method (Palv,Ie = 1.02 * Paw,Ie + 0.097; r2 = 0.977). The SLICE method allows continuous monitoring of non-linear pulmonary mechanics on a breath-by-breath basis at the bedside.
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Affiliation(s)
- J Guttmann
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
| | - L Eberhard
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
| | - B Fabry
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
| | - D Zappe
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
| | - H Bernhard
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
| | - M Lichtwarck-Aschoff
- Department of Anesthesia and Surgical Intensive Care Medicine, Central Hospital Augsburg, D-86156 Augsburg, Germany
| | - M Adolph
- Department of Anesthesia and Surgical Intensive Care Medicine, Central Hospital Augsburg, D-86156 Augsburg, Germany
| | - G Wolff
- Clinical Physiology, Clinic for Cardiac and Thoracic Surgery, Department of Surgery, University of Basel, CH-4031 Basel, Switzerland
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Buehler S, Schumann S, Lichtwarck-Aschoff M, Guttmann J. PEEP titration on the basis of intratidal resistance-volume profiles. Crit Care 2014. [PMCID: PMC4069377 DOI: 10.1186/cc13463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Schumann S, Goebel U, Haberstroh J, Vimlati L, Schneider M, Lichtwarck-Aschoff M, Guttmann J. Determination of respiratory system mechanics during inspiration and expiration by FLow-controlled EXpiration (FLEX): a pilot study in anesthetized pigs. Minerva Anestesiol 2014; 80:19-28. [PMID: 24193175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
BACKGROUND Differences between inspiratory and expiratory lung mechanics result in the hysteresis of the pressure volume-loop. While hysteresis area is a global parameter describing the difference between inspiration and expiration in mechanics under quasi-static conditions, a detailed analysis of this difference under the dynamic conditions of mechanical ventilation is feasible once inspiratory and expiratory compliance (Cin/Cex) are determined separately. This requires uncoupling of expiratory flow rate and volume (V). METHODS Five piglets were mechanically ventilated at positive end-expiratory pressure (PEEP) levels ranging from 0 to 15 cmH2O. Expiratory flow rate was linearized by a computer-controlled resistor (flow-controlled expiration). The volume-dependent Cin(V) and Cex(V) profiles were calculated from the tracheal pressure volume-loops. RESULTS The intratidal curve-progression of Cex(V) was altogether higher with a steeper slope compared to Cin(V). With increasing positive end-expiratory pressure (PEEP) dynamic hysteresis area decreased and Cex(V) tended to run more parallel to Cin(V). CONCLUSION The relation between inspiratory and expiratory compliance profiles is associated with the hysteresis area and behaves PEEP dependent. Analysing the Cin-Cex-relation might therefore potentially offer a new approach to titrate PEEP and tidal volume.
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Affiliation(s)
- S Schumann
- Department of Anesthesiology and Critical Care Medicine, University Medical Centre Freiburg, Freiburg, Germany -
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Deetjen P, Lichtwarck-Aschoff M. [Author's reply]. Anaesthesist 2013; 62:570. [PMID: 24024246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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Buehler S, Schumann S, Lichtwarck-Aschoff M, Lozano S, Guttmann J. The shape of intratidal resistance-volume and compliance-volume curves in mechanical ventilation – an animal study. BIOMED ENG-BIOMED TE 2013; 58 Suppl 1:/j/bmte.2013.58.issue-s1-D/bmt-2013-4118/bmt-2013-4118.xml. [DOI: 10.1515/bmt-2013-4118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Buehler S, Schumann S, Lichtwarck-Aschoff M, Lozano S, Guttmann J. Dynamic Hysteresis Behaviour of Respiratory System Mechanics. BIOMED ENG-BIOMED TE 2013; 58 Suppl 1:/j/bmte.2013.58.issue-s1-D/bmt-2013-4119/bmt-2013-4119.xml. [DOI: 10.1515/bmt-2013-4119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Vimlati L, Larsson A, Hedenstierna G, Lichtwarck-Aschoff M. Oxygenation correlates with lung aeration during unsupported spontaneous breathing in porcine lung collapse model. Crit Care 2012. [PMCID: PMC3363539 DOI: 10.1186/cc10728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Vimlati L, Larsson A, Hedenstierna G, Lichtwarck-Aschoff M. During spontaneous breathing cardiac output lacks major effect on pulmonary shunting in porcine lungs with partial collapse. Crit Care 2012. [PMCID: PMC3363538 DOI: 10.1186/cc10727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
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Schumann S, Messmer F, Lichtwarck-Aschoff M, Haberthuer C, Guttmann J. Cardiogenic oscillations in spontaneous breathing airway signal reflect respiratory system mechanics. Acta Anaesthesiol Scand 2011; 55:980-6. [PMID: 21770903 DOI: 10.1111/j.1399-6576.2011.02488.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Heartbeat-related pressure oscillations appear at the airway opening. We investigated whether these cardiogenic oscillations (COS) - extracted from spontaneous breathing signals - reflect the compliance of the respiratory system. METHODS Fifteen volunteers breathed spontaneously at normal or reduced chest wall compliance, i.e. with and without thorax strapping, and at normal or reduced lung compliance, induced by positive end-expiratory pressure (PEEP). COS-related signals were extracted by averaging the flow and pressure curve sections, temporally aligned to the electrocardiogram signal. RESULTS COS-related airway pressure and flow curves correlated closely for each subject (r(2) =0.97 ± 0.02, P<0.0001). At the unstrapped thorax, the oscillation's amplitudes were 0.07 ± 0.03 cm H(2) O (pressure) and 22 ± 10 ml/s (flow). COS-related pressure amplitudes correlated closely with the ratio of tidal volume divided by pressure amplitude (r(2) =0.88, P<0.001) and furthermore increased with either thorax strapping (P<0.001) or with increasing PEEP (P=0.049). CONCLUSION We conclude that COS extracted from the pressure and flow signal reflect the compliance of the respiratory system and could potentially allow estimating respiratory system mechanics during spontaneous breathing.
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Affiliation(s)
- S Schumann
- Division for Experimental Anaesthesiology, University Medical Centre, Freiburg, Germany.
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Lichtwarck-Aschoff M, Pippi A, Dietrich B. [Supplement to continuing medical education article "Dysnatremia in intensive care patients"]. Anaesthesist 2011; 60:377-80. [PMID: 21424311 DOI: 10.1007/s00101-011-1862-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Schumann S, Goebel U, Haberstroh J, Schneider M, Priebe HJ, Lichtwarck-Aschoff M, Guttmann J. Flow-balanced expiration reduces oedema formation in a porcine oleic acid lung injury model. Crit Care 2011. [PMCID: PMC3066870 DOI: 10.1186/cc9616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Schumann S, Vimlati L, Moeller K, Wahl A, Kawati R, Guttmann J, Lichtwarck-Aschoff M. Atelectasis and overdistension are detected by heartbeat-induced disturbances in the pressure-volume loop. Crit Care 2010. [PMCID: PMC2934141 DOI: 10.1186/cc8409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Schumann S, Burcza B, Haberthuer C, Lichtwarck-Aschoff M, Guttmann J. Estimating the intratidal compliance profile with the new gliding-SLICE method. Crit Care 2010. [PMCID: PMC2934162 DOI: 10.1186/cc8408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Jaschinski U, Lichtwarck-Aschoff M. [Acute perioperative disturbances of renal function. Strategies for prevention and therapy]. Anaesthesist 2009; 58:829-47; quiz 848-9. [PMID: 19669104 DOI: 10.1007/s00101-009-1592-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The increasing life expectancy in industrial nations leads to an increase in the number of elderly and aged persons treated in hospital. Increasingly more complex operations are being carried out on this group of patients. Renal dysfunction in the preoperative situation increases morbidity and mortality. Acute kidney injury (AKI) is nearly always part of a multi-organ dysfunction syndrome in critically ill patients. The treatment strategy of the AKI should be oriented to the degree of organ dysfunction. However, the stage of organ dysfunction is mostly unknown so that the therapeutically exploitable interval is often missed. The same therapy is practically always used for all patients: administration of fluids and diuretics often under the premise of "the kidneys must be rinsed". A unified classification of the continuation of kidney function disorders using the RIFLE criteria (risk, injury, failure, loss, endstage kidney disease) can assist recognition of early stages of kidney failure in order to react correspondingly with therapeutic measures and to critically question or optimize the use of conservative treatment strategies.
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Affiliation(s)
- U Jaschinski
- Klinik für Anästhesiologie und Operative Intensivmedizin, Klinikum Augsburg, Augsburg.
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Schumann S, Messmer F, Lichtwarck-Aschoff M, Haberthuer C, Moeller K, Guttmann J. Cardiogenic oscillations extracted from spontaneous breathing airway pressure and flow signal are related to chest wall motility and continuous positive airway pressure. Crit Care 2009. [PMCID: PMC4083893 DOI: 10.1186/cc7171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Lichtwarck-Aschoff M, Deetjen P. [Beyond the boundaries. Or: the glycocalyx on its way from physiological model to the clinical setting]. Anaesthesist 2008; 57:957-8. [PMID: 18941824 DOI: 10.1007/s00101-008-1448-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- M Lichtwarck-Aschoff
- Klinik für Anästhesiologie und Operative Intensivmedizin, Klinikum Augsburg, Stenglinstr. 2, 86156 Augsburg, Deutschland.
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Wahl A, Lichtwarck-Aschoff M, Möller K, Schumann S, Guttmann J. Determination of expiratory lung mechanics using cardiogenic oscillations during decelerated expiration. Crit Care 2008. [PMCID: PMC4088681 DOI: 10.1186/cc6531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Wahl A, Lichtwarck-Aschoff M, Möller K, Schumann S, Guttmann J. Cardiogenic oscillations reflect nonlinear lung mechanics. Crit Care 2008. [PMCID: PMC4088682 DOI: 10.1186/cc6532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Halbeck E, Jaschinski U, Scherer A, Aulmann A, Lichtwarck-Aschoff M, Forst H. Implementation of glycemic control – problems and solutions. Crit Care 2007. [PMCID: PMC4095190 DOI: 10.1186/cc5296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Knorpp H, Stahl C, Schumann S, Lichtwarck-Aschoff M, Guttmann J. Nonlinearity of intratidal airway resistance. Crit Care 2007. [PMCID: PMC4095247 DOI: 10.1186/cc5353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Hedenstierna G, Lichtwarck-Aschoff M. Interfacing spontaneous breathing and mechanical ventilation. New insights. Minerva Anestesiol 2006; 72:183-98. [PMID: 16570030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Mechanical ventilation (MV) with positive pressure insufflations of gas into the lung may be required to ensure sufficient oxygenation of blood and elimination of carbon dioxide in acute respiratory failure. Interfacing spontaneous breathing and mechanical ventilation has been used to improve gas exchange and may offer other advantages regarding integrity of lung tissue. Airway pressure release ventilation (APRV), or bilevel positive airway pressure (BiPAP), is a mechanical ventilatory mode with a low respiratory rate upon which spontaneous breaths can be superimposed during any time of the respiratory cycle. The mechanical pressure variations cause inflation and deflation of the lungs and the spontaneous breaths are added according to the demand of the respiratory center and neuromuscular function. This technique improves oxygenation of blood compared to MV alone. This seems to be caused by recruitment of collapsed lung tissue and increased aeration of the lung. Moreover, ventilation is distributed more to the dependent (dorsal in supine position) regions than with mechanical ventilation alone. Since blood flow goes preferentially to the dependent regions, the altered ventilation distribution results in improved matching of ventilation and perfusion, further enhancing or facilitating gas exchange. Moreover, there is less cyclic collapse, i.e. less re-collapse during expiration and reopening during inspiration than with MV alone. Further development of the interfacing technique can be expected, with synchronization and also dosing of the mechanical support and with triggering of the ventilator that is based on neural recordings rather than mechanical signals as pressure and flow.
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Affiliation(s)
- G Hedenstierna
- Department of Medical Sciences, Clinical Physiology, University Hospital, Uppsala, Sweden.
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Knorpp H, Lichtwarck-aschoff M, Stahl C, Schumann S, Möller K, Guttmann J. Crit Care 2006; 10:P14. [DOI: 10.1186/cc4361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Lichtwarck-Aschoff M. Notes on the Physiology and Pathophysiology of Cardiac Output. Anasthesiol Intensivmed Notfallmed Schmerzther 2005; 40:612-5. [PMID: 16252227 DOI: 10.1055/s-2005-870470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Surgical Sciences, Universitätsklinik Uppsala, Schweden und Klinik für Anästhesiologie und Operative Intensivmedizin, Klinikum Augsburg.
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Ried M, Stöcklein R, Lichtwarck-Aschoff M, Forst H. Therapie einer schweren Gerinnungsstörung nach traumatischer Plazentalösung mit rekombinantem Faktor VIIa. Geburtshilfe Frauenheilkd 2004. [DOI: 10.1055/s-2004-815842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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Lichtwarck-Aschoff M, Helmer A, Kawati R, Lattuada M, Sjöstrand UH, Zügel N, Guttmann J, Hedenstierna G. Good short-term agreement between measured and calculated tracheal pressure. Br J Anaesth 2003; 91:239-48. [PMID: 12878624 DOI: 10.1093/bja/aeg169] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Tracheal pressure (P(tr)) is required to measure the resistance of the tracheal tube and the breathing circuit. P(tr) can either be measured with a catheter or, alternatively, calculated from the pressure-flow data available from the ventilator. METHODS Calculated P(tr) was compared with measured P(tr) during controlled ventilation and assisted spontaneous breathing in 18 healthy and surfactant-depleted piglets. Their lungs were ventilated using different flow patterns, tidal volumes (V(T)) and levels of positive end-expiratory pressure. RESULTS In terms of the root mean square error (RMS), indicating the average deviation of calculated from measured P(tr), the difference between calculated and measured P(tr) was 0.6 cm H(2)O (95%CI 0.58-0.65) for volume-controlled ventilation; 0.73 cm H(2)O (0.72-0.75) for pressure support ventilation; and 0.78 cm H(2)O (0.75-0.80) for bi-level positive airway pressure ventilation. CONCLUSION The good agreement between calculated and measured P(tr) during varying conditions, suggests that calculating P(tr) could help setting the ventilator and choosing the appropriate level of support.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Surgical Sciences, Section of Anaesthesiology and Intensive Care Medicine, Uppsala University, Sweden.
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Guttmann J, Haberthür C, Mols G, Lichtwarck-Aschoff M. Automatic tube compensation (ATC). Minerva Anestesiol 2002; 68:369-77. [PMID: 12029248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Automatic tube compensation (ATC) is a new option to compensate for the non-linearly flow-dependent pressure drop across an endotracheal or tracheostomy tube (ETT) during inspiration and expiration. ATC is based on a closed-loop working principle. ATC is not a true ventilatory mode but rather a new option which can be combined with all conventional ventilatory modes. ATC compensates for the tube-related additional work of breathing. As of yet, ATC has been associated with certain benefits for the tracheally intubated spontaneously breathing patient. Among these, reduced work of breathing, preservation of the natural "noisy" breathing pattern, enhanced synchronization between the patient and the ventilator, and improvement of respiratory comfort seem to be most important. Moreover, sufficient spontaneous breathing with ATC alone, i.e. without any additional ventilatory assist, might help to predict more accurately readiness for extubation in the last phase of weaning from mechanical ventilation. Furthermore, it has been shown in patients with acute lung injury that ATC unloaded the inspiratory muscles and increased alveolar ventilation without adversely affecting cardiorespiratory function. It is the purpose of this article to describe the working principle of ATC and to give a review of the actual scientific discussion concerning ATC.
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Affiliation(s)
- J Guttmann
- Section for Experimental Anesthesiology, Department of Anesthesiology and Critical Care Medicine, University of Freiburg, Germany.
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Markström A, Hedlund A, Sjöstrand U, Nordgren A, Lichtwarck-Aschoff M. Effects of sustained pressure application on compliance and blood gases in healthy porcine lungs. Acta Anaesthesiol Scand 2001; 45:1235-40. [PMID: 11736676 DOI: 10.1034/j.1399-6576.2001.451011.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Short periods of sustained increase in airway pressures (Press(up)) are believed to re-open lung areas that collapsed upon induction of anaesthesia. Recruitment of alveolar surface is usually assessed in terms of changes in the pressure-volume (PV) curve. The purpose of this study was to analyse PV-curves before and after a Press(up) and to ascertain whether such changes are compatible with the concept of recruitment of lung volume. METHODS During ketamine anaesthesia, 12 healthy piglets were subjected to a Press(up) with end-expiratory pressure (PEEP) of 12 cmH2O and end-inspiratory pressure of 40 cmH2O. Before and after Press(up), PV-curves were obtained from a slow insufflation of 630 ml at zero PEEP (ZEEP). RESULTS Compliance was non-linear both before and after Press(up) increasing up to 300 ml and sharply decreasing thereafter. After Press(up), the entire compliance curve was shifted to a higher absolute level. Up to 100 ml and a pressure level corresponding to the lower inflection point on the PV-curve (LIP), compliance was higher before Press(up). No effects on blood gases could be observed. CONCLUSION If the similar shape of the compliance curve corresponds to a similar chain of re-opening and overdistension events, this would imply that all volume gained by Press(up) is lost within 10 min, without explaining the higher absolute compliance following Press(up). We speculate that a) re-opening of rapidly collapsing small airways determines the initial compliance increase; b) the lower compliance after Press(up) until LIP indicates reduced intratidal re-opening of lung regions; and c) changes in bronchomotor tone induced by Press(up) raise the absolute compliance, with a similar scenario of alveolar and small airway recruitment now taking place but at different degrees of airway stiffness.
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Affiliation(s)
- A Markström
- Department of Surgical Sciences/Section of Anaesthesiology and Intensive Care, University Hospital, Uppsala, Sweden.
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Abstract
The endotracheal tube (ETT) is a considerably flow-dependent and, therefore, variable mechanical load. Conventional modes of respiratory support cannot adequately compensate for the tube resistance in inspiratorion and not at all in expiration. Automatic tube compensation (ATC) compensates for the flow-dependent pressure drop across the tracheal tube by a positive pressure support in inspiration and by a negative pressure support in expiration. The pressure support closely follows the nonlinear pressure-flow curve of the ETT. Automatic tube compensation has an indirect closed-loop working principle since the target tracheal pressure is not directly measured but rather calculated from continuously measured airway pressure and flow rate. It is not an own ventilatory mode but rather a component of flow-proportional pressure support which can be combined with all conventional ventilatory modes, and provides a rational basis for subdividing the pressure support to overcome the mechanical load of the tubing and to overcome that of the respiratory system. Partial tube obstructions, which could decrease the effectivity of ATC, could be detected automatically by analysing the expiratory flow signal using a software, which could be easily implemented into the ventilator. The effectivity of ATC during long-term application can be maintained by intermittent short-term measurement of the tracheal pressure. Up to now there is no commercially available ventilator which allows complete expiratory ATC. Studies in volunteers and in mechanically ventilated patients have convincingly shown that ATC reduces work of breathing and increases respiratory comfort. In addition, successful extubation could be better predicted with this mode in difficult-to-wean patients compared to other modes. There are no special rules in the clinical application of ATC. However, to prevent overassist the support level of the ventilatory mode which is combined with ATC should be reduced.
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Affiliation(s)
- J Guttmann
- Anaesthesiologische Universitätsklinik, Sektion Experimentelle Anaesthesiologie, Klinikum der Albert-Ludwigs-Universität Freiburg.
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Mols G, Kessler V, Benzing A, Lichtwarck-Aschoff M, Geiger K, Guttmann J. Is pulmonary resistance constant, within the range of tidal volume ventilation, in patients with ARDS? Br J Anaesth 2001; 86:176-82. [PMID: 11573656 PMCID: PMC8543332 DOI: 10.1093/bja/86.2.176] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
When managing patients with acute respiratory distress syndrome (ARDS), respiratory system compliance is usually considered first and changes in resistance, although recognized, are neglected. Resistance can change considerably between minimum and maximum lung volume, but is generally assumed to be constant in the tidal volume range (V(T)). We measured resistance during tidal ventilation in 16 patients with ARDS or acute lung injury by the slice method and multiple linear regression analysis. Resistance was constant within V(T) in only six of 16 patients. In the remaining patients, resistance decreased, increased or showed complex changes. We conclude that resistance within V(T) varies considerably from patient to patient and that constant resistance within V(T) is not always likely.
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Affiliation(s)
- G Mols
- Department of Anaesthesiology and Critical Care Medicine, University of Freiburg, Germany
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Mols G, Hermle G, Schubert J, Miekisch W, Benzing A, Lichtwarck-Aschoff M, Geiger K, Walmrath D, Guttmann J. Volume-dependent compliance and ventilation-perfusion mismatch in surfactant-depleted isolated rabbit lungs. Crit Care Med 2001; 29:144-51. [PMID: 11176175 DOI: 10.1097/00003246-200101000-00029] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Volume-dependent alterations of lung compliance are usually studied over a very large volume range. However, the course of compliance within the comparably small tidal volume (intratidal compliance-volume curve) may also provide relevant information about the impact of mechanical ventilation on pulmonary gas exchange. Consequently, we determined the association of the distribution of ventilation and perfusion with the intratidal compliance-volume curve after modification of positive end-expiratory pressure (PEEP). DESIGN Repeated measurements in randomized order. SETTING An animal laboratory. SUBJECTS Isolated perfused rabbit lungs (n = 14). INTERVENTIONS Surfactant was removed by bronchoalveolar lavage. The lungs were ventilated thereafter with a constant tidal volume (10 mL/kg body weight). Five levels of PEEP (0-4 cm H2O) were applied in random order for 20 mins each. MEASUREMENTS AND MAIN RESULTS The intratidal compliance-volume curve was determined with the slice method for each PEEP level. Concurrently, pulmonary gas exchange was assessed by the multiple inert gas elimination technique. At a PEEP of 0-1 cm H2O, the intratidal compliance-volume curve was formed a bow with downward concavity. At a PEEP of 2 cm H2O, concavity was minimal or compliance was almost constant, whereas higher PEEP levels (3-4 cm H2O) resulted in a decrease of compliance within tidal inflation. Pulmonary gas exchange did not differ between PEEP levels of of 0, 1, and 2 cm H2O. Pulmonary shunt was lowest and perfusion of alveoli with a normal ventilation-perfusion was highest at a PEEP of 3-4 cm H2O. Deadspace ventilation did not change significantly but tended to increase with PEEP. CONCLUSIONS An increase of compliance at the very beginning of tidal inflation was associated with impaired pulmonary gas exchange, indicating insufficient alveolar recruitment by the PEEP level. Consequently, the lowest PEEP level preventing alveolar atelectasis could be detected by analyzing the course of compliance within tidal volume without the need for total lung inflation.
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Affiliation(s)
- G Mols
- Department of Anesthesiology and Critical Care Medicine, University of Freiburg, Germany
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Lichtwarck-Aschoff M, Mols G, Hedlund AJ, Kessler V, Markström AM, Guttmann J, Hedenstierna G, Sjöstrand UH. Compliance is nonlinear over tidal volume irrespective of positive end-expiratory pressure level in surfactant-depleted piglets. Am J Respir Crit Care Med 2000; 162:2125-33. [PMID: 11112126 DOI: 10.1164/ajrccm.162.6.9910018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Between the lower and the upper inflection point of a quasistatic pressure-volume (PV) curve, a segment usually appears in which the PV relationship is steep and linear (i.e., compliance is high, with maximal volume change per pressure change, and is constant). Traditionally it is assumed that when positive end-expiratory pressure (PEEP) and tidal volume (V T) are titrated such that the end-inspiratory volume is positioned at this linear segment of the PV curve, compliance is constant over VT during ongoing ventilation. The validity of this assumption was addressed in this study. In 14 surfactant-deficient piglets, PEEP was increased from 3 cm H(2)O to 24 cm H(2)O, and the compliance associated with 10 consecutive volume increments up to full VT was determined with a modified multiple-occlusion method at the different PEEP levels. With PEEP at approximately the lower inflection point, compliance was minimal in most lungs and decreased markedly over VT, indicating overdistension. Compliance both increased and decreased within the same breath at intermediate PEEP levels. It is concluded that a PEEP that results in constant compliance over the full VT range is difficult to find, and cannot be derived from conventional respiratory-mechanical analyses; nor does this PEEP level coincide with maximal gas exchange.
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Lichtwarck-Aschoff M, Kessler V, Sjöstrand UH, Hedlund A, Mols G, Rubertsson S, Markström AM, Guttmann J. Static versus dynamic respiratory mechanics for setting the ventilator. Br J Anaesth 2000; 85:577-86. [PMID: 11064617 DOI: 10.1093/bja/85.4.577] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The lower inflection point (LIP) of the inspiratory limb of a static pressure-volume (PV) loop is assumed to indicate the pressure at which most lung units are recruited. The LIP is determined by a static manoeuvre with a PV-history that is different from the PV-history of the actual ventilation. In nine surfactant-deficient piglets, information to allow setting PEEP and VT was obtained, both from the PV-curve and also during ongoing ventilation from the dynamic compliance relationship. According to LIP, PEEP was set at 20 (95% confidence interval 17-22) cm H2O. Volume-dependent dynamic compliance suggested a PEEP reduction (to 15 (13-18) cm H2O). Pulmonary gas exchange remained satisfactory and this change resulted in reduced mechanical stress on the respiratory system, indirectly indicated by volume-dependent compliance being consistently great during the entire inspiration.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden
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Guttmann J, Kessler V, Mols G, Lichtwarck-Aschoff M, Haberthür C. INERTANCE DES RESPIRATORISCHEN SYSTEMS BEIM AKUTEN ATEMNOTSYNDROM (ARDS). BIOMED ENG-BIOMED TE 2000. [DOI: 10.1515/bmte.2000.45.s1.381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
Ventilation with decelerating inspiratory flow is known to reduce the dead space fraction and to decrease PaCO2. Constant inspiratory flow with an end-inspiratory pause (EIP) is also known to increase the removal of CO2. The aim of the study was to elucidate the effect of the pause/no-flow period while both the pattern and rate of inspiratory flow was unchanged, and when the lung was ventilated with sufficient PEEP to prevent end-expiratory collapse. Surfactant depleted piglets were assigned to decelerating or constant inspiratory flow with 24 breaths per minute (bpm) or 12 bpm, or to constant flow, without and with an end-inspiratory pause of 25%. By adding an EIP the total time without active inspiratory flow of the respiratory cycle was kept unchanged. Gas exchange, airway pressures, functional residual capacity (using sulfurhexafluoride) and haemodynamics (thermo-dye indicator dilution technique) were measured. Irrespective of ventilatory frequency, PaCO2 was lower and serial dead space reduced with decelerating flow, compared with constant inspiratory flow. With an end-inspiratory pause added to constant inspiratory flow, serial dead space was reduced but did not decrease PaCO2. The results of this study corroborate the assumption that total time without active inspiratory flow is important for arterial CO2-tension.
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Affiliation(s)
- A Markström
- Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden
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Lichtwarck-Aschoff M, Hedlund AJ, Nordgren KA, Wegenius GA, Markström AM, Guttmann J, Sjöstrand UH. Variables used to set PEEP in the lung lavage model are poorly related. Br J Anaesth 1999; 83:890-7. [PMID: 10700789 DOI: 10.1093/bja/83.6.890] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Setting an appropriate positive end-expiratory pressure (PEEP) value is determined by respiratory mechanics, gas exchange and oxygen transport. As these variables may be optimal at different PEEP values, a unique PEEP value may not exist which satisfies both the demands of minimizing mechanical stress and optimizing oxygen transport. In 15 surfactant-deficient piglets, PEEP was increased progressively. Arterial oxygenation and functional residual capacity (FRC) increased, while specific compliance of the respiratory system decreased. Static compliance increased up to a threshold value of PEEP of 8 cm H2O, after which it decreased. This threshold PEEP did not coincide with the lower inflection point of the inspiratory limb of the pressure-volume (PV) loop. Oxygen transport did not correlate with respiratory mechanics or FRC. In the lavage model, the lower inflection point of the PV curve may reflect opening pressure rather than the pressure required to keep the recruited lung open. Recruitment takes place together with a change in the elastic properties of the already open parts of the lung. No single PEEP level is optimal for both oxygen transport and reduction of mechanical stress.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anaesthesiology and Intensive Care, Uppsala University Hospital, Sweden
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Goedje O, Hoeke K, Lichtwarck-Aschoff M, Faltchauser A, Lamm P, Reichart B. Continuous cardiac output by femoral arterial thermodilution calibrated pulse contour analysis: comparison with pulmonary arterial thermodilution. Crit Care Med 1999; 27:2407-12. [PMID: 10579256 DOI: 10.1097/00003246-199911000-00014] [Citation(s) in RCA: 261] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To compare two thermodilution methods for the determination of cardiac output (CO)-thermodilution in the pulmonary artery (COpa) and thermodilution in the femoral artery (COa)-with each other and with CO determined by continuous pulse contour analysis (COpc) in terms of reproducibility, bias, and correlation among the different methods. Good agreement between the methods would indicate the potential of pulse contour analysis to monitor CO continuously and at reduced invasiveness. DESIGN Prospective criterion standard study. SETTING Cardiac surgical intensive care unit in a university hospital. PATIENTS Twenty-four postoperative cardiac surgery patients. INTERVENTIONS Without interfering with standard hospital cardiac recovery procedures, changes in CO as a result of the postsurgical course, administration of vasoactive substances, and/or fluid administration were recorded. CO was first recorded after a 1-hr stabilization period in the intensive care unit and hourly thereafter for 6 hrs, and by subsequent determinations at 9, 12, and 24 hrs. MEASUREMENTS AND MAIN RESULTS There were 216 simultaneous determinations of COpa, COa, and COpc. COpc was initially calibrated using COa, and no further recalibration of COpc was performed. COpa ranged from 3.0 to 11.8 L/min, and systemic vascular resistance ranged from 252 to 2434 dyne x sec/cm5. The mean difference (bias) +/-2 SD of differences (limits of agreement) was -0.29+/-1.31 L/min for COpa vs. COa, 0.07+/-1.4 L/min for COpc vs. COpa, and -0.22+/-1.58 L/min for COpc vs. COa. In all but four patients COpc correlated with COa after the initial calibration. Correlation and precision of COpc vs. COa was stable for 24 hrs. CONCLUSIONS Femoral artery pulse contour CO correlates well with both COpa and COa even during substantial variations in vascular tone and hemodynamics. Additionally, CO determined by arterial thermodilution correlates well with COpa. Thus, COa can be used to calibrate COpc.
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Affiliation(s)
- O Goedje
- Department of Cardiac Surgery, Ludwig-Maximillians-University of Munich, Germany.
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Mols G, Brandes I, Kessler V, Lichtwarck-Aschoff M, Loop T, Geiger K, Guttmann J. Volume-dependent compliance in ARDS: proposal of a new diagnostic concept. Intensive Care Med 1999; 25:1084-91. [PMID: 10551963 DOI: 10.1007/s001340051016] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Adaptation of ventilator settings to the individual's respiratory system mechanics requires information about the pressure-volume relationship and the change of compliance which is dependent on inflated volume. Unfortunately, established methods of obtaining this information are invasive and time-consuming, and, therefore, not well suited for clinical routine. We propose a new standardized diagnostic concept based on the recently developed slice method. This multiple linear regression method (MLR) determines volume-dependent respiratory system compliance (C(SLICE)) within the tidal volume (V(T)) during ongoing mechanical ventilation. The impact of a ventilator strategy, recommended by a consensus conference, on the course of compliance within V(T) was investigated in patients with the acute respiratory distress syndrome (ARDS) or acute lung injury (ALI). DESIGN Prospective observational study. SETTING Intensive care unit of a university hospital. PATIENTS 14 ARDS patients, 2 patients with ALI. INTERVENTIONS None. MEASUREMENTS AND RESULTS After measurement of flow and airway pressure and calculation of tracheal pressure, C(SLICE) was determined. The resulting course of C(SLICE) within V(T) was estimated using a mathematical algorithm. C(SLICE) data were compared to those obtained by standard MLR. We found decreasing C(SLICE) mainly in the upper part of V(T) in all patients. In 7 patients, we found an additional increasing C(SLICE) mainly in the lower part of V(T). CONCLUSIONS C(SLICE) was not constant in patients with ARDS/ALI whose lungs were ventilated according to consensus conference recommendations. The proposed diagnostic concept may serve as a new tool to obtain a standardized estimation of respiratory system compliance within V(T) non-invasively without interfering with ongoing mechanical ventilation.
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Affiliation(s)
- G Mols
- Department of Anesthesiology and Critical Care Medicine, University of Freiburg, Hugstetterstrasse 55, 79106 Freiburg, Germany.
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Guttmann J, Eberhard L, Haberthür C, Mols G, Kessler V, Lichtwarck-Aschoff M, Geiger K. Detection of endotracheal tube obstruction by analysis of the expiratory flow signal. Intensive Care Med 1998; 24:1163-72. [PMID: 9876979 DOI: 10.1007/s001340050740] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
OBJECTIVE Acute obstruction of endotracheal tubes (ETT) increases airway pressure, decreases tidal volume, increases the risk of dynamic hyperinflation by prolonging the duration of passive expiration, and prevents reliable calculation of tracheal pressure. We propose a computer-assisted method for detecting ETT obstruction during controlled mechanical ventilation. The method only requires measurement of the expiratory flow. DESIGN Computer simulation; prospective study in two cases; retrospective study in one case and in seven patients with the adult respiratory distress syndrome (ARDS). SETTING Laboratory of the Section of Experimental Anaesthesiology (University of Freiburg); surgical adult intensive care units in a university hospital (University of Basel) and in a university affiliated hospital (Zentralklinikum Augsburg). PATIENTS 3 patients with partial ETT or bronchial obstructions and 7 ARDS patients. MEASUREMENTS AND RESULTS Expiratory flow was measured using a pneumotachograph and integrated to obtain expiratory volume. The time-constant of passive expiration (tauE) as a function of expired volume [tauE(V(E)) function] was calculated from the expiratory volume/flow curve. We investigated the tauE(V(E)) function of data obtained from: (1) computer simulation of mechanically ventilated homogeneous and inhomogeneous lungs intubated with ETTs of different sizes; (2) one patient with an artificial ETT obstruction of 7.5 and 25% of the cross-sectional area of the ETT (case 1); (3) one patient with ETT obstruction due to secretions (case 2); (4) one patient with acute bronchial constriction (case 3); (5) seven ARDS patients who showed an increase in airway resistance of more than 2 cm H2O x s/l. It was found that an ETT obstruction caused an increase in tauE in early expiration (at high flow), whereas tauE in late expiration was virtually unchanged. The reason for this is the flow dependency of the increase in ETT resistance produced by ETT obstruction. Unlike ETT obstruction, an increase in pure airway resistance produced an increase in tauE throughout expiration. CONCLUSIONS An ETT obstruction can be reliably distinguished from an increase in pure airway resistance by a characteristic pattern change in the tauE(V(E)) function, which can be detected easily even by an automated pattern recognition system.
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Affiliation(s)
- J Guttmann
- Section of Experimental Anaesthesiology, Clinic of Anaesthesiology, Germany.
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Lichtwarck-Aschoff M, Zimmermann GJ, Erhardt W. Reduced CO2-elimination during combined high-frequency ventilation compared to conventional pressure-controlled ventilation in surfactant-deficient piglets. Acta Anaesthesiol Scand 1998; 42:335-42. [PMID: 9542562 DOI: 10.1111/j.1399-6576.1998.tb04926.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Combined high-frequency ventilation (CHFV) combines a conventional low-frequency component with super-imposed high-frequency jet pulses. The intention is to overcome the limited CO2-elimination of high-frequency ventilation, and to decrease airway pressures and enhance hemodynamic performance by reducing the conventional component. The present study was performed to compare the effects of conventional continuous positive-pressure ventilation (CPPV) on gas exchange, airway pressures and cardiac output to those of CHFV at matched minute volume (MV) and mean airway pressure (MPAW). METHODS Sixteen anaesthetised piglets with lavage-induced surfactant deficiency were ventilated with CPPV, with positive end-expiratory pressure (PEEP) set to obliterate the lower inflection point of the inspiratory pressure-volume loop. This setting was compared to CHFV during which 50% of the total MV was applied as superimposed jet pulses of 20 Hz at otherwise unchanged settings, and to CPPV at a PEEP level which was reduced (CPPVred) until MPAW matched MPAW during CHFV. Gas exchange, airway pressures and hemodynamics were measured after the ventilatory setting had been applied for 20 min. RESULTS MPAW decreased from (median) 2.7 kPa with CPPV to 2.4 kPa with CHFV (P < or = 0.05). Peak inspiratory pressure was 3.6 kPa with CPPV, 3.2 kPa with CHFV, and 3.2 kPa with CPPVred (P < or = 0.05 for differences to CPPV), respectively. PaCO2 was comparable during CPPV (5.9 kPa), CPPVred and CHFVCO2, while it increased during CHFV (6.8 kPa, (P < or = 0.05)). Cardiac output did not differ significantly between the settings. CONCLUSION In the porcine lavage model, CO2-elimination is reduced during CHFV compared to CPPV at matched minute volume. At matched mean airway pressure, CHFV fails to reduce peak inspiratory airway pressure and to improve hemodynamic performance compared to CPPV.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anesthesiology and Surgical Intensive Care, Central Hospital Augsburg, FRG
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Lichtwarck-Aschoff M, Guttmann J, Eberhard L, Fabry B, Birle J, Adolph M. Delayed derecruitment after removal of PEEP in patients with acute lung injury. Acta Anaesthesiol Scand 1997; 41:675-84. [PMID: 9241325 DOI: 10.1111/j.1399-6576.1997.tb04766.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND A step decrease in positive end-expiratory airway pressure (PEEP) is not followed by an instantaneous loss of the PEEP-induced increase in end-expiratory lung volume (EELV). Rather, the reduction of EELV is delayed, while adverse PEEP effects on hemodynamics are immediately attenuated upon the drop in airway pressure. Step PEEP increments were applied to the lungs of patients with acute lung injury. It was investigated retrospectively whether enlargement of end-expiratory lung volume and changes in lung mechanics persist 45 min after removal of the PEEP increment. METHODS In 14 patients with acute lung injury (LIS score 2.7) EELV and volume-dependent dynamic compliance of the respiratory system (Cdyn,rs) were determined 45 min after removal of an additional PEEP increment (0.64 kPa added to baseline PEEP of 1.0 kPa). RESULTS Nine patients kept an EELV gain of 13% (SD 7) and showed improved Cdyn,rs. In 5 patients, EELV was reduced (by 9% (SD 6)) and Cdyn,rs unchanged after removal of the PEEP increment compared to baseline. CONCLUSION A subgroup of patients with acute lung injury, the characteristics of which remain to be defined, benefit from prolonged recruitment effects up to 45 min after removal of a PEEP increment, while sequelae of continuously increased airway pressures are minimised.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anesthesiology and Surgical Intensive Care, Central Hospital Augsburg, Federal Republic of Germany
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Lichtwarck-Aschoff M, Beale R, Pfeiffer UJ. Central venous pressure, pulmonary artery occlusion pressure, intrathoracic blood volume, and right ventricular end-diastolic volume as indicators of cardiac preload. J Crit Care 1996; 11:180-8. [PMID: 8977994 DOI: 10.1016/s0883-9441(96)90029-5] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE Central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP) and right ventricular end-diastolic volume (RVEDV) are often regarded as indicators of both circulating blood volume and cardiac preload. to evaluate these relationships, the response of each variable to induced volume shifts was tested. The relationships between these variables and cardiac index (CI) and stroke volume index (SVI) was also recorded to assess the utility of each variable as an indicator of cardiac preload. The responses of the new variable intrathoracic blood volume (ITBV) to the same maneuvers was also tested. To examine the effects of changes in cardiac output alone on ITBV, the effects of infusing dobutamine were studied. MATERIALS AND METHODS Ten anesthetized piglets were studied during conditions of normovolemia, hypovolemia, and hypervolemia. The effects of an infusion of dobutamine were examined under normovolemia and hypovolemia. Cardiac output was measured by thermo-dilution, and ITBV was measured by double-indicator dilution. RESULTS CI was correlated to CVP with r2 = .42 (P < or = .01), to PAOP with r2 = .43 (P < or = .01), to RVEDV index with r2 = .21 (P < or = .01), and to ITBV with r2 = .78 (P < or = .01) (pooled absolute values). Bias (mean difference of the percent changes with normovolemia = 100%) +/- 1 SD; for SVI - ITBV index was 1 +/- 22%, for SVI - CVP it was -128 +/- 214%; for SVI - PAOP it was -36 +/- 46%; and for SVI - RVEDV index it was 1 +/- 29%. Dobutamine infusion increased heart rate (to about 190 x min-1 and CI by 30% in normovolemia and hypovolemia, while ITBV remained basically unchanged. CONCLUSIONS Under the experimental conditions chosen neither CVP, PAOP, nor RVEDV reliably indicated changes in circulating blood volume, nor were they linearly and tightly correlated to the resulting changes in SVI. ITBV reflected both changes in volume status and the resulting alteration in cardiac output. The possibility that ITBV might be cardiac output-dependent was not supported. ITBV, therefore, shows potential as a clinically useful indicator of overall cardiac preload.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anaesthesiology and Surgical Intensive Care Medicine, Zentralklinikum Augsburg, Germany
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Markström AM, Lichtwarck-Aschoff M, Svensson BA, Nordgren KA, Sjöstrand UH. Ventilation with constant versus decelerating inspiratory flow in experimentally induced acute respiratory failure. Anesthesiology 1996; 84:882-9. [PMID: 8638843 DOI: 10.1097/00000542-199604000-00016] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Recognition of the potential for ventilator-associated lung injury has renewed the debate on the importance of the inspiratory flow pattern. The aim of this study was to determine whether a ventilatory pattern with decelerating inspiratory flow, with the major part of the tidal volume delivered early, would increase functional residual capacity at unchanged (or even reduced) inspiratory airway pressures and improve gas exchange at different positive end-expiratory pressure levels. METHODS Surfactant depletion was induced by repeated bronchoalveolar lavage in 13 anesthetized piglets. Decelerating and constant inspiratory flow ventilation was applied at positive end-expiratory pressure levels of 22, 17, 13, 9, and 4 cm H(2)O. Tidal volume, inspiration-to-expiration ratio, and ventilatory frequency were kept constant. Airway pressures, gas exchange, functional residual capacity (using a wash-in/washout method with sulfurhexafluoride), central hemodynamics, and extravascular lung water (using the thermo-dye-indicator dilution technique) were measured. RESULTS Decelerating inspiratory flow yielded a lower arterial carbon dioxide tension compared to constant flow, that is, it improved alveolar ventilation. There were no differences between the flow patterns regarding end-inspiratory occlusion airway pressure, end-inspiratory lung volume, static compliance, or arterial oxygen tension. No differences were seen in hemodynamics and oxygen delivery. CONCLUSIONS The decelerating inspiratory flow pattern increased carbon dioxide elimination, without any reduction of inspiratory airway pressure or apparent improvement in arterial oxygen tension. It remains to be established whether these differences are sufficiently pronounced to justify therapeutic consideration.
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Affiliation(s)
- A M Markström
- Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden
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Lichtwarck-Aschoff M, Markström AM, Hedlund AJ, Nielsen JB, Nordgren KA, Sjöstrand UH. Oxygenation remains unaffected by increased inspiration-to-expiration ratio but impairs hemodynamics in surfactant-depleted piglets. Intensive Care Med 1996; 22:329-35. [PMID: 8708171 DOI: 10.1007/bf01700455] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVES Prolongation of inspiratory time is used to reduce lung injury in mechanical ventilation. The aim of this study was to isolate the effects of inspiratory time on airway pressure, gas exchange, and hemodynamics, while ventilatory frequency, tidal volume, and mean airway pressure were kept constant. DESIGN Randomized experimental trial. SETTING Experimental laboratory of a University Department of Anesthesiology and Intensive Care. ANIMALS Twelve anesthetised piglets. INTERVENTIONS After lavage the reference setting was pressure-controlled ventilation with a decelerating flow; I:E was 1:1, and PEEP was set to 75% of the inflection point pressure level. The I:E ratios of 1.5:1, 2.3:1, and 4:1 were applied randomly. Under open lung conditions, mean airway pressure was kept constant by reduction of external PEEP. MEASUREMENTS AND RESULTS Gas exchange, airway pressures, hemodynamics, functional residual capacity (SF6 tracer), and intrathoracic fluid volumes (double indicator dilution) were measured. Compared to the I:E of 1:1, PaCO2 was 8% lower, with I:E 2.3:1 and 4:1 (p < or = 0.01) while PaO2 remained unchanged. The decrease in inspiratory airway pressure with increased inspiratory time was due to the response of the pressure-regulated volume-controlled mode to an increased I:E ratio. Stroke index and right ventricular ejection fraction were depressed at higher I:E ratios (SI by 18% at 2.3:1, 20% at 4:1; RVEF by 10% at 2.3:1, 13% at 4:1; p < or = 0.05). CONCLUSION Under open lung conditions with an increased I:E ratio, oxygenation remained unaffected while hemodynamics were impaired.
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Affiliation(s)
- M Lichtwarck-Aschoff
- Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden
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Markström AM, Lichtwarck-Aschoff M, Hedlund AJ, Nordgren KA, Sjöstrand UH. Under open lung conditions inverse ratio ventilation causes intrinsic PEEP and hemodynamic impairment. Ups J Med Sci 1996; 101:257-71. [PMID: 9055390 DOI: 10.3109/03009739609178925] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Inverse ratio ventilation (IRV) is commonly used in clinical practice. Several studies have used IRV in order to recruit collapsed alveoli. In a randomised trial in twelve surfactant depleted piglets, the lungs were ventilated with sufficient positive end-expiratory pressure (PEEP) to prevent end-expiratory collapse, and the effects of increased inspiration-to-expiration (I:E ratio) were evaluated. Pressure regulated ventilation (with I:E of 1:1, constant tidal volume and decelerating inspiratory flow) was used at 30 breaths per minute (bpm). I:E ratios of 1.5:1, 2.3:1 and 4:1 were applied sequentially. When the I:E ratio was increased, external PEEP had to be reduced in order to keep total PEEP constant. Functional residual capacity, airway pressures, gas exchange, extrathermal volume and hemodynamics were measured. With I:E ratios above 2:1 intrinsic PEEP was generated and with concomitant decrease in cardiac index. PaO2 was not affected, but oxygen delivery was reduced. It is concluded that I:E ratios of 2:1, or above, generate increased intrinsic PEEP with compromised hemodynamics.
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Affiliation(s)
- A M Markström
- Department of Anesthesiology, University Hospital, Uppsala, Sweden
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Kisch H, Leucht S, Lichtwarck-Aschoff M, Pfeiffer UJ. Accuracy and reproducibility of the measurement of actively circulating blood volume with an integrated fiberoptic monitoring system. Crit Care Med 1995; 23:885-93. [PMID: 7736747 DOI: 10.1097/00003246-199505000-00017] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE Bedside monitoring of circulating blood volume has become possible with the introduction of an integrated fiberoptic monitoring system that calculates blood volume from the changes in blood concentration of indocyanine green dye 4 mins after injection. The aim of this investigation was to compare the blood volume estimate of the integrated fiberoptic monitoring system (group 1) with the standard methods of blood volume measurement using Evans blue (group 2), and indocyanine green measured photometrically (group 3). DESIGN Prospective laboratory study. SETTING Animal laboratory of a University's institute for experimental surgery. SUBJECTS Eleven anesthetized, paralyzed, and mechanically ventilated piglets. INTERVENTIONS A central venous catheter was used for the injection of the indicator dyes (Evans blue and indocyanine green). A fiberoptic thermistor catheter was advanced into the thoracic aorta. The fiberoptic catheter detects indocyanine green by reflection densitometry for the estimation of blood volume of the integrated fiberoptic monitoring system. Samples for the determination of Evans blue and indocyanine green concentrations were drawn from an arterial catheter in the femoral artery over a period of 17 mins after injection. MEASUREMENTS AND MAIN RESULTS Measurements were performed during normovolemia, hypovolemia (blood withdrawal of < or = 30 mL/kg), and hypervolemia (retransfusion of the withdrawn blood plus an infusion of 10% hydroxyethyl starch [45 mL/kg]). Linear regression, correlation, and bias were calculated for the comparison of the blood volume estimates by the fiberoptic monitoring system (group 1) vs. the total blood volume estimates using Evans blue (group 2) and indocyanine green (group 3): group 1 = 0.82.group 2-26 mL; r2 = 82.71%; r = .91; n = 40; group 1-group 2 +/- 1 SD = -435 +/- 368 mL; group 1 = 0.79.group 3 + 50 mL; r2 = 74.81%; r = .87; n = 28; group 1-group 3 +/- 1 SD = -506 +/- 374 mL. CONCLUSIONS The results demonstrate that the blood volume estimate of the fiberoptic monitoring system (group 1) correlates closely with the total blood volume measurement using Evans blue (group 2) and indocyanine green (group 3). Trapped indicator in the packed red cell column after centrifugation of the blood samples may account for an overestimation of group 2 and group 3 of approximately 10% to 14%, but there still remains a proportional difference of 10% between group 1 vs. group 2 and vs. group 3. This difference is due to the longer mixing times of group 3 (16 mins) and group 2 (17 mins), during which they are distributed in slowly exchanging blood pools. It seems that the blood volume estimate of the fiberoptic monitoring system (group 1) represents the actively circulating blood volume and may be useful for bedside monitoring.
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Affiliation(s)
- H Kisch
- Department of Anaesthesiology and Surgical Intensive Care Medicine, Zentralklinikum Augsburg, FRG
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50
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Sjöstrand UH, Lichtwarck-Aschoff M, Nielsen JB, Markström A, Larsson A, Svensson BA, Wegenius GA, Nordgren KA. Different ventilatory approaches to keep the lung open. Intensive Care Med 1995; 21:310-8. [PMID: 7650253 DOI: 10.1007/bf01705409] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVES To study the ability of different ventilatory approaches to keep the lung open. DESIGN Different ventilatory patterns were applied in surfactant deficient lungs with PEEP set to achieve pre-lavage PaO2. SETTING Experimental laboratory of a University Department of Anaesthesiology and Intensive Care. ANIMALS 15 anaesthetised piglets. INTERVENTIONS One volume-controlled mode (L-IPPV201:1.5) and two pressure-controlled modes at 20 breaths per minute (bpm) and I:E ratios of 2:1 and 1.5:1 (L-PRVC202:1 and L-PRVC201.5:1), and two pressure-controlled modes at 60 bpm and I:E of 1:1 and 1:1.5 (L-PRVC601:1 and L-PRVC601:1.5) were investigated. The pressure-controlled modes were applied using "Pressure-Regulated Volume-Controlled Ventilation" (PRVC). MEASUREMENTS AND RESULTS Gas exchange, airway pressures, hemodynamics, FRC and intrathoracic fluid volumes were measured. Gas exchange was the same for all modes. FRC was 30% higher with all post-lavage settings. By reducing inspiratory time MPAW decreased from 25 cmH2O by 3 cmH2O with L-PRVC201.5:1 and L-PRVC601:1.5. End-inspiratory airway pressure was 29 cmH2O with L-PRVC201.5:1 and 40 cmH2O with L-IPPV201:1.5, while the other modes displayed intermediate values. End-inspiratory lung volume was 65 ml/kg with L-IPPV201:1.5, but it was reduced to 50 and 49 ml/kg with L-PRVC601:1 and L-PRVC601:1.5. Compliance was 16 and 18 ml/cmH2O with L-PRVC202:1 and L-PRVC201.5:1, while it was lower with L-IPPV201:1.5, L-PRVC601:1 and L-PRVC601:1.5. Oxygen delivery was maintained at pre-lavage level with L-PRVC201.5:1 (657 ml/min.m2), the other modes displayed reduced oxygen delivery compared with pre-lavage. CONCLUSION Neither the rapid frequency modes nor the low frequency volume-controlled mode kept the surfactant deficient lungs open. Pressure-controlled inverse ratio ventilation (20 bpm) kept the lungs open at reduced end-inspiratory airway pressures and hence reduced risk of barotrauma. Reducing I:E ratio in this latter modality from 2:1 to 1.5:1 further improved oxygen delivery.
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Affiliation(s)
- U H Sjöstrand
- Department of Anesthesiology and Intensive Care, University Hospital, Uppsala, Sweden
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