Pathophysiologische Grundlagen der mechanischen Beatmung

Zusammenfassung

Eine Beatmung ist immer dann erforderlich, wenn die eigene Ventilation nicht mehr ausreicht. Dieses zeigt sich typischerweise in einer Hyperkapnie. Die Hypoxämie folgt hier meist nur sekundär aufgrund der Hypoventilation. Ursache ist in der Regel eine überlastete Atemmuskulatur (Atempumpe), meist durch eine akute oder chronische Erkrankung. Bei isolierter Hypoxämie ist eine Beatmung nur dann indiziert, wenn der Sauerstoffgehalt ( = Sauerstoffsättigung × Hb. × 1,39) unter eine kritische Schwelle sinkt oder infolge der fortschreitenden Grunderkrankung (z. B. Pneumonie) und zusätzlicher Überlastung die Erschöpfung der Atemmuskulatur droht. Neben dem positiven Effekt auf den Gasaustausch kann Beatmung an sich insbesondere durch zu hohe Drucke, Volumina oder Sauerstoffkonzentration zur Schädigung des Lungenparenchyms führen. Durch lungenprotektive Beatmungsstrategien lassen sich diese Schäden weitgehend vermeiden. Hierbei muss im Einzelfall geprüft werden, nach welchen Parametern beatmet werden soll. Ist der Leitparameter nicht wie üblich der Sauerstoffpartialdruck, sondern der Sauerstoffgehalt, kommt es in der Regel zu einer deutlich schonenderen Beatmung. Eine Ausnahme hiervon ist das kardial bedingte Lungenödem, da die Beatmung hier durch den Beatmungsdruck und den PEEP zur deutlichen Verbesserung der Diffusion, Senkung der Preload und eine Abnahme der Atemarbeit führt. Ein entscheidender Fortschritt in der Beatmung insbesondere von schweren Akutfällen wurde in den letzten Jahren durch Erweiterung der Beatmungszugänge, d. h. nicht-invasive Alternativen zum Beatmungstubus erreicht. Die Maskenbeatmung ist insbesondere bei exazerbierter COPD der invasiven Beatmung bezüglich des Outcome drastisch überlegen. Dies wird insbesondere durch einen Rückgang der ventilator-assoziierten Pneumonie verursacht, vermutlich weil die Patienten unter Maske noch abhusten können, was die Lungenreinigung deutlich verbessert. Eine optimale Entlastung der durch die Erkrankung überlasteten Atemmuskulatur wird durch eine kontrollierte Beatmung ermöglicht. Der kontrollierte Beatmungsmodus lässt sich aber im Akutfall in der Regel nur mit Sedation erreichen. Eine assistierte Beatmung bessert zwar den Gasaustausch, führt jedoch nur zu einer mäßigen Entlastung der Atemmuskulatur, was ihre Rekompensation verzögert. Eine dauerhafte kontrollierte Beatmung unter Sedation über einen längeren Zeitraum (Tage) benötigt zwischengeschaltete kurze Phasen mit assistierter- oder Spontanatmung, um eine Atrophie der Atemmuskulatur zu verhindern. In der Übersicht werden die Hintergründe zwischen Sauerstoffangebot und -verbrauch insbesondere unter Berücksichtigung der Atempumpeninsuffizienz und ihrer Beeinflussbarkeit durch verschiedene Beatmungsverfahren dargestellt.

Abstract

Mechanical ventilation is required if ventilatory insufficiency is present. This is typically indicated by hypercapnea. Hypoxemia occurs secondary to hypoventilation. Usually overload of the respiratory muscles (ventilatory pump) will be the underlying mechanism, for the most part caused by acute or chronic disease. In case of sole hypoxemia mechanical ventilation will only be indicated if the oxygen-content (equals oxygensaturation × haemoglobin × 1.39) drops below a critical threshold or if ventilatory pump failure is immanent on account of the underlying disease (eg. pneumonia). The background of our recommendations is to avoid potential damage caused by mechanical ventilation. Especially high inspiratory pressures and oxygen concentrations can be harmful to the lung. Therefore every case has to evaluated for individual target parameters of ventilation. The use of the oxygen-content instead of the arterial oxygen pressure as the target parameter will usually lead to a more careful ventilation. Cardiogenic pulmonary oedema is an exception to this rule since inspiratory positive pressure and PEEP will result in improved diffusion as well as reduction of preload and work of breathing. In recent years progress has been made on the field of ventilation access especially in severe and acute cases. Non-invasive ventilation is superior to invasive ventilation in patients with exacerbated COPD since it improves outcome effectively. This is being caused by a decline in ventilator associated pneumonias, most likely because non-invasive ventilation allows patients to clear their secretions by coughing, resulting in improved lung clearance. Controlled ventilation allows optimal unloading of the respiratory muscles which have been overloaded by the underlying disease. Application of a controlled ventilation mode in acute disease will usually require some kind of sedation. Assisted ventilation will result in improved gas exchange but only incomplete unloading of respiratory muscles and therefore delayed restitution. Permanent controlled ventilation under sedation for a prolonged period (days) requires intermittent periods of assisted- or spontaneous breathing in order to avoid atrophy of the respiratory muscles. This review summarizes background information on the nature of the derangement, the relation between oxygen supply and consumption under special consideration of respiratory muscle insufficiency and impact of different ventilation modes.

Literatur

• 1 Esteban A, Anzueto A, Frutos F. et al . Mechanical Ventilation International Study Group. Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study.  JAMA. 2002;  16 (287) 345-355
• 2 Tobin M J. Advances in mechanical ventilation.  N Engl J Med. 2001;  344 1986-1996
• 3 Tobin M J. Mechanical ventilation.  N Engl J Med. 1994;  330 1056-1061
• 4 No authors listed . Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network.  N Engl J Med. 2000;  342 1301-1308
• 5 Denis D, Fayon M J, Berger P. et al . Prolonged moderate hyperoxia induces hyperresponsiveness and airway inflammation in newborn rats.  Pediatr Res. 2001;  50 515-519
• 6 Ferrara T B, Fox R B. Effects of oxygen toxicity on cuprolinic blue-stained proteoglycans in alveolar basement membranes.  Am J Respir Cell Mol Biol. 1992;  6 219-224
• 7 Pagano A, Barazzone-Argiroffo C. Alveolar cell death in hyperoxia-induced lung injury.  Ann N Y Acad Sci. 2003;  1010 405-416
• 8 Mencke T, Echternach M, Kleinschmidt S. et al . Laryngeal morbidity and quality of tracheal intubation: a randomized controlled trial.  Anesthesiology. 2003;  98 1049-1056
• 9 Sue R D, Susanto I. Long-term complications of artificial airways.  Clin Chest Med. 2003;  24 457-471
• 10 Keller C, Brimacombe J. Bronchial mucus transport velocity in paralyzed anesthetized patients: a comparison of the laryngeal mask airway and cuffed tracheal tube.  Anesth Analg. 1998;  86 1280-1282
• 11 Konrad F, Schreiber T, Brecht-Kraus D. et al . Mucociliary transport in ICU patients.  Chest. 1994;  105 237-241
• 12 Sanada Y, Kojima Y, Fonkalsrud E W. Injury of cilia induced by tracheal tube cuffs.  Surg Gynecol Obstet. 1982;  154 648-652
• 13 Fellahi J L, Valtier B, Beauchet A. et al . Does positive end-expiratory pressure ventilation improve left ventricular function? A comparative study by transesophageal echocardiography in cardiac and noncardiac patients.  Chest. 1998;  114 556-562
• 14 Meurice J C, Mergy J, Rostykus C. et al . A trial arrhythmia as a complication of nasal CPAP.  Chest. 1992;  102 640-642
• 15 Tuxen D V. Detrimental effects of positive end-expiratory pressure during controlled mechanical ventilation of patients with severe airflow obstruction.  Am Rev Respir Dis. 1989;  140 5-9
• 16 Hussain S N, Roussos C. Distribution of respiratory muscle and organ blood flow during endotoxic shock in dogs.  J Appl Physiol. 1985;  59 1802-1808
• 17 Viires N, Sillye G, Aubier M. et al . Regional blood flow distribution in dog during induced hypotension and low cardiac output. Spontaneous breathing versus artificial ventilation.  J Clin Invest. 1983;  72 935-947
• 18 Agusti A G, Rodriguez-Roisin R, Roca J. et al . Oxyhemoglobin affinity in patients with chronic obstructive pulmonary disease and acute respiratory failure: role of mechanical ventilation.  Crit Care Med. 1986;  14 610-613
• 19 Thorens J B, Jolliet P, Ritz M. et al . Effects of rapid permissive hypercapnia on hemodynamics, gas exchange, and oxygen transport and consumption during mechanical ventilation for the acute respiratory distress syndrome.  Intensive Care Med. 1996;  22 182-191
• 20 Butterick C J, Williams D A, Boxer L A. et al . Changes in energy metabolism, structure and function in alveolar macrophages under anaerobic conditions.  Br J Haematol. 1981;  48 523-532
• 21 Simon L M, Robin E D, Phillips J R. et al . Enzymatic basis for bioenergetic differences of alveolar versus peritoneal macrophages and enzyme regulation by molecular O₂.  J Clin Invest. 1977;  59 443-448
• 22 Terrados N, Jansson E, Sylven C. et al . Is hypoxia a stimulus for synthesis of oxidative enzymes and myoglobin?.  J Appl Physiol. 1990;  68 2369-2372
• 23 Cartee G D, Douen A G, Ramlal T. et al . Stimulation of glucose transport in skeletal muscle by hypoxia.  J Appl Physiol. 1991;  70 1593-1600
• 24 Dery M A, Michaud M D, Richard D E. Hypoxia-inducible factor 1: regulation by hypoxic and non-hypoxic activators.  Int J Biochem Cell Biol. 2005;  37 535-540
• 25 Xia Y, Warshaw J B, Haddad G G. Effect of chronic hypoxia on glucose transporters in heart and skeletal muscle of immature and adult rats.  Am J Physiol. 1997;  273 R1734-1741
• 26 Gattinoni L, Tognoni G, Pesenti A. et al . Effect of prone positioning on the survival of patients with acute respiratory failure.  N Engl J Med. 2001;  345 568-573
• 27 British Thoracic Society Standards of Care Committee . Non-invasive ventilation in acute respiratory failure.  Thorax. 2002;  57 192-211
• 28 Begin P, Grassino A. Inspiratory muscle dysfunction and chronic hypercapnia in chronic obstructive pulmonary disease.  Am Rev Respir Dis. 1991;  143 905-912
• 29 Begin P, Mathieu J, Almirall J. et al . Relationship between chronic hypercapnia and inspiratory-muscle weakness in myotonic dystrophy.  Am J Respir Crit Care Med. 1997;  156 133-139
• 30 Gorini M, Misuri G, Corrado A. et al . Breathing pattern and carbon dioxide retention in severe chronic obstructive pulmonary disease.  Thorax. 1996;  51 677-683
• 31 Köhler D, Schönhofer B. Apnoe-hypopnoe. Eine oder zwei Entitäten?.  Pneumologie. 1998;  52 311-318
• 32 Leach R M, Treacher D F. The pulmonary physician in critical care * 2: oxygen delivery and consumption in the critically ill.  Thorax. 2002;  57 170-177
• 33 Hayes M A, Timmins A C, Yau E H. et al . Elevation of systemic oxygen delivery in the treatment of critically ill patients.  N Engl J Med. 1994;  330 1717-1722
• 34 Weg J G. Oxygen transport in adult respiratory distress syndrome and other acute circulatory problems: relationship of oxygen delivery and oxygen consumption.  Crit Care Med. 1991;  19 650-657
• 35 Hayes M A, Yau E H, Timmins A C. et al . Response of critically ill patients to treatment aimed at achieving supranormal oxygen delivery and consumption. Relationship to outcome.  Chest. 1993;  103 886-895
• 36 Hebert P C, Linden P van der, Biro G. et al . Physiologic aspects of anemia.  Crit Care Clin. 2004;  20 187-212
• 37 Schonhofer B, Wenzel M, Geibel M. et al . Blood transfusion and lung function in chronically anemic patients with severe chronic obstructive pulmonary disease.  Crit Care Med. 1998;  26 1824-1828
• 38 Schonhofer B, Bohrer H, Kohler D. Blood transfusion facilitating difficult weaning from the ventilator.  Anaesthesia. 1998;  53 181-184
• 39 Greif R, Akca O, Horn E P. et al . Supplemental perioperative oxygen to reduce the incidence of surgical-wound infection. Outcomes Research Group.  N Engl J Med. 2000;  342 161-167
• 40 Bernstein D, Teitel D F. Myocardial and systemic oxygenation during severe hypoxemia in ventilated lambs.  Am J Physiol. 1990;  258 H1856-1864
• 41 Borgia J F, Horvath S M. Effects of acute prolonged hypoxia on cardiovascular dynamics in dogs.  J Appl Physiol. 1977;  43 784-789
• 42 Mazer C D, Stanley W C, Hickey R F. et al . Myocardial metabolism during hypoxia: maintained lactate oxidation during increased glycolysis.  Metabolism. 1990;  39 913-918
• 43 Taylor P M. Effects of hypoxia on endocrine and metabolic responses to anaesthesia in ponies.  Res Vet Sci. 1999;  66 39-44
• 44 Todd M M, Wu B, Maktabi M. et al . Cerebral blood flow and oxygen delivery during hypoxemia and hemodilution: role of arterial oxygen content.  Am J Physiol. 1994;  267 H2025-2031
• 45 Grubbstrom J, Berglund B, Kaijser L. Myocardial oxygen supply and lactate metabolism during marked arterial hypoxaemia.  Acta Physiol Scand. 1993;  149 303-310
• 46 Kaijser L, Grubbstrom J, Berglund B. Myocardial lactate release during prolonged exercise under hypoxaemia.  Acta Physiol Scand. 1993;  149 427-433
• 47 Gupta G D, Jain S K, Dasgupta S R. Haemodynamic changes with blood transfusion in chronic severe anaemia.  Acta Cardiol. 1977;  32 25-39
• 48 Roach R C, Koskolou M D, Calbet J A. et al . Arterial O₂ content and tension in regulation of cardiac output and leg blood flow during exercise in humans.  Am J Physiol. 1999;  276 H438-445
• 49 Sutton J R, Reeves J T, Wagner P D. et al . Operation Everest II: oxygen transport during exercise at extreme simulated altitude.  J Appl Physiol. 1988 Apr;  64 (4) 1309-1321
• 50 West J B, Boyer S J, Graber D J. et al . Maximal exercise at extreme altitudes on Mount Everest.  J Appl Physiol. 1983;  55 688-698
• 51 Gayan-Ramirez G, Decramer M. Effects of mechanical ventilation on diaphragm function and biology.  Eur Respir J. 2002;  20 1579-1586
• 52 Enright S, Chatham K, Ionescu A A. et al . Inspiratory muscle training improves lung function and exercise capacity in adults with cystic fibrosis.  Chest. 2004;  126 405-411
• 53 Newell S Z, McKenzie D K, Gandevia S C. Inspiratory and skeletal muscle strength and endurance and diaphragmatic activation in patients with chronic airflow limitation.  Thorax. 1989;  44 903-912
• 54 de Bruin P F, Ueki J, Watson A. et al . Size and strength of the respiratory and quadriceps muscles in patients with chronic asthma.  Eur Respir J. 1997;  10 59-64
• 55 Connett R J, Honig C R, Gayeski T E. et al . Defining hypoxia: a systems view of VO₂, glycolysis, energetics, and intracellular PO₂.  J Appl Physiol. 1990;  68 833-842
• 56 Ferguson G T, Irvin C G, Cherniack R M. Relationship of diaphragm glycogen, lactate, and function to respiratory failure.  Am Rev Respir Dis. 1990;  141 926-932
• 57 Lockhat D, Roussos C, Ianuzzo C D. Metabolite changes in the loaded hypoperfused and failing diaphragm.  J Appl Physiol. 1988;  65 1563-1571
• 58 Marczak M, Pokorski M. Oxygen breathing and ventilation.  J Physiol Pharmacol. 2004;  55 127-134
• 59 Benditt Jr J, Make B J. Transtracheal oxygen decreases inspired minute ventilation.  Am Rev Respir Dis. 1989;  139 627-631
• 60 Benditt J, Pollock M, Roa J. et al . Transtracheal delivery of gas decreases the oxygen cost of breathing.  Am Rev Respir Dis. 1993;  147 1207-1210
• 61 Shanely R A, Gammeren D van, Deruisseau K C. et al . Mechanical ventilation depresses protein synthesis in the rat diaphragm.  Am J Respir Crit Care Med. 2004;  170 994-999
• 62 Agostoni P, Cattadori G, Bianchi M. et al . Exercise-induced pulmonary edema in heart failure.  Circulation. 2003;  108 2666-2671
• 63 Nava S, Larovere M T, Fanfulla F. et al . Orthopnea and inspiratory effort in chronic heart failure patients.  Respir Med. 2003;  97 647-653
• 64 Beydon L, Cinotti L, Rekik N. et al . Changes in the distribution of ventilation and perfusion associated with separation from mechanical ventilation in patients with obstructive pulmonary disease.  Anesthesiology. 1991;  75 730-738
• 65 Ambrosino N, Rossi A. Proportional assist ventilation (PAV): a significant advance or a futile struggle between logic and practice?.  Thorax. 2002;  57 272-276
• 66 Maggiore S M, Richard J C, Brochard L. What has been learnt from P/V curves in patients with acute lung injury/acute respiratory distress syndrome.  Eur Respir J Suppl. 2003;  42 22s-26s
• 67 Papo M C, Paczan P R, Fuhrman B P. et al . Perfluorocarbon-associated gas exchange improves oxygenation, lung mechanics, and survival in a model of adult respiratory distress syndrome.  Crit Care Med. 1996;  24 466-474
• 68 Frank J A, Matthay M A. Science review: mechanisms of ventilator-induced injury.  Crit Care. 2003Jun;  7 233-241
• 69 Gattinoni L, Caironi P, Carlesso E. How to ventilate patients with acute lung injury and acute respiratory distress syndrome.  Curr Opin Crit Care. 2005;  11 69-76
• 70 Lionetti V, Recchia F A, Ranieri V M. Overview of ventilator-induced lung injury mechanisms.  Curr Opin Crit Care. 2005;  11 82-86
• 71 Ricard J D, Dreyfuss D, Saumon G. Ventilator-induced lung injury.  Curr Opin Crit Care. 2002;  8 12-20
• 72 Cinnella G, Conti G, Lofaso F. et al . Effects of assisted ventilation on the work of breathing: volume-controlled versus pressure-controlled ventilation.  Am J Respir Crit Care Med. 1996;  153 1025-1033
• 73 Hubmayr R D, Loosbrock L M, Gillespie D J. et al . Oxygen uptake during weaning from mechanical ventilation.  Chest. 1988;  94 1148-1155
• 74 Manthous C A, Hall J B, Kushner R. et al . The effect of mechanical ventilation on oxygen consumption in critically ill patients.  Am J Respir Crit Care Med. 1995;  151 210-214
• 75 Rice A J, Nakayama H C, Haverkamp H C. et al . Controlled versus assisted mechanical ventilation effects on respiratory motor output in sleeping humans.  Am J Respir Crit Care Med. 2003;  168 92-101
• 76 Murphy G S, Vender J S. Neuromuscular-blocking drugs. Use and misuse in the intensive care unit.  Crit Care Clin. 2001;  17 925-942
• 77 Vernon D D, Witte M K. Effect of neuromuscular blockade on oxygen consumption and energy expenditure in sedated, mechanically ventilated children.  Crit Care Med. 2000;  28 1569-1571
• 78 Freebairn R C, Derrick J, Gomersall C D. et al . Oxygen delivery, oxygen consumption, and gastric intramucosal pH are not improved by a computer-controlled, closed-loop, vecuronium infusion in severe sepsis and septic shock.  Crit Care Med. 1997;  25 72-77
• 79 Schönhofer B, Köhler D. Ventilatorische Insuffizienz und hyperkapnische Kompensation infolge chronisch belasteter Atempumpe.  Dtsch Med Wochenschr. 1994 Sep 9;  119 (36) 1209-1214
• 80 Kallet R H, Campbell A R, Alonso J A. et al . The effects of pressure control versus volume control assisted ventilation on patient work of breathing in acute lung injury and acute respiratory distress syndrome.  Respir Care. 2000;  45 1085-1096
• 81 Leung P, Jubran A, Tobin M J. Comparison of assisted ventilator modes on triggering, patient effort, and dyspnea.  Am J Respir Crit Care Med. 1997;  155 1940-1948
• 82 Swinamer D L, Fedoruk L M, Jones R L. et al . Energy expenditure associated with CPAP and T-piece spontaneous ventilatory trials. Changes following prolonged mechanical ventilation.  Chest. 1989;  96 867-872
• 83 Rasche K, Laier-Groeneveld G, Weyland W. et al . Sauerstoffverbrauch der Atemmuskulatur unter kontrollierter bzw. assistierter Beatmung bei Patienten mit chronischer Ateminsuffizienz.  Med Klin. 1994;  89 43-46
• 84 Kress J P, Pohlman A S, O'Connor M F. et al . Daily interruption of sedative infusions in critically ill patients undergoing mechanical ventilation.  N Engl J Med. 2000;  342 1471-1477