More than 75’000 patients die in the USA on ventilators due to acute lung injury
Over 30% of patients on mechanical ventilation are ventilated for more than 12 hours (Esteban et al 2002; Esteban et al. 2008). Forty percent of these patients will die during their hospital stay (Rubenfeld 2005) which is 75’000 patient per year – more than the annual deaths due to breast cancer. About 24% of those patients with previously healthy lungs will develop Acute Lung Injury (ALI) or ARDS within the first 5 days of artificial ventilation (Gajic et al. 2004). Despite ongoing efforts to protect the lungs, the incidence of barotrauma in patients with ARDS still approaches 6-10%. Inadequate ventilator settings are clearly related to barotrauma (Boussarsar M et al, 2002). Barotrauma does not cause death directly, but the presence of barotrauma doubles the risk of dying (Anzueto et al. 2004).
Mechanical Ventilation is a life-saving intervention for patients with acute respiratory failure and used is in more than 30% of patients entering the intensive care unit. Mechanical Ventilation, however, holds also the risk of ventilator induced lung injury (VILI), pneumothorax, or cardiovascular side effects. Lung protective ventilation strategies are applied by clinicians who have to adjust ventilator settings meticulously. Meeting the ventilation demands of critically ill patients and at the same time protecting the fragile lung tissue is a challenging task.
To date, clinicians base their clinical decision making on conventional physiologic parameters such as tidal volumes, airway pressures, blood gases and pressure-volume curves, all of which poorly reflecting the complex lung condition. After a few hours of mechanical ventilation the dependent parts of the lung suffer compression due to gravity and abdominal distension such that they progressively collapse. This phenomenon is aggravated by high concentrations of inspired oxygen and infections. The lungs become heterogeneous with their non-dependent parts being forced to receive most of the tidal volume and associated over-distention. All these mechanisms cause lung inflammation and fibrosis, which is hardly recognized by physicians because current bedside lung monitoring is inadequate.
EIT holds the potential to reduce mortality and length of stay
Swisstom’s BB2 technology was created with the goal to provide a bedside tool for optimizing mechanical ventilation. Its purpose is to enhance the diagnostic capabilities of clinicians in order to empower them to take better decisions at the bedside. By providing images of the individual lung condition and associated diagnostic information, Swisstom helps individualize lung protection.
It takes less than 10 minutes for clinicians to verify the potential for lung recruitment and select PEEP levels in order to minimize lung collapse and over-distension. As useful as a GPS on a foggy day, clinicians will finally say: Now I can see what is happening within my patient’s lung.
A body of literature suggests that protective mechanical ventilation strategies can decrease mortality (Amato et al. 2015 and 1998 ; ARDSnetwork 2000) in patients with ARDS, decrease length of stay (Mercat et al. 2008), and decrease the use of rescue therapies (Meade et al. 2008). A large international study on 18302 patients reported a mortality of patients on a ventilator for longer than 12 hours to be around 30% in spite of the significant attempts to improve treatment (Esteban et.al. 2013). Physiological evidence suggests that substantial reduction in mortality may be expected by an individualization of ventilator settings, especially in patients with severe heterogeneous lung disease (Terragni et al. 2007). However, without proper lung monitors at the bedside (Gattinoni et al. 2006), clinicians remain blind as to the effects of their therapy. Standard cook-book-like protocols for lung protection have been used in recent years but are clearly limited and possibly cause harm to many patients (ARDSnetwork 2000, Grasso et al. 2007; Bassler et al. 2010).
All of the statements above can be supported by literature (see below). However, there is one particular and compelling study to show that EIT improves outcome, by a group from Boston. This randomized controlled study on the prospective use of EIT to guide mechanical ventilation was performed in animals because it was considered unethical to do this kind of study in humans. Two groups of animals were made to acquire Acute Lung Injury. One group was treated with the ARDSnet protocols, the other group was treated with the help of EIT. Here is what the authors conclude (Wolf 2013):
“Electrical impedance tomography-guided ventilation resulted in improved respiratory mechanics, improved gas exchange, and reduced histologic evidence of ventilator-induced lung injury in an animal model.”
Esteban et.al. Mechanical Ventilation International Study Group. Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study. JAMA. 2002 Jan 16;287(3):345-55.
Esteban et.al. VENTILA Group. Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med. 2008 Jan 15;177(2):170-7.
Rubenfeld et.al. Incidence and outcomes of acute lung injury. N Engl J Med. 2005 Oct 20;353(16):1685-93.
Gajic et.al. Ventilator-associated lung injury in patients without acute lung injury at the onset of mechanical ventilation. Crit Care Med. 2004 Sep;32(9):1817-24.
Boussarsar et.al. Relationship between ventilatory settings and barotrauma in the acute respiratory distress syndrome. Intensive Care Med. 2002 Apr;28(4):406-13. Epub 2002 Jan 15. Review.
Anzueto et.al. Incidence, risk factors and outcome of barotrauma in mechanically ventilated patients. Intensive Care Med. 2004 Apr;30(4):612-9. Epub 2004 Feb 28.
Amato et.al. Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome. N Engl J Med. 1998 Feb 5;338(6):347-54.
Amato M.B.P. et al.: Driving pressure and survival in the acute respiratory distress syndrom. NEJM. 2015 Feb 19; 372(8): 747-755.
The Acute Respiratory Distress Syndrome Network: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342:1301–1308.
Mercat et.al. Expiratory Pressure (Express) Study Group. Positive end-expiratory pressure setting in adults with acute lung injury and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2008 Feb 13;299(6):646-55
Esteban et.al. Evolution of mortality over time in patients receiving mechanical ventilation. Am J Respir Crit Care Med. 2013 Jul 15;188(2):220-30.
Terragni et.al. Tidal hyperinflation during low tidal volume ventilation in acute respiratory distress syndrome. Am J Respir Crit Care Med. 2007 Jan 15;175(2):160-6.
Meade et.al. Lung Open Ventilation Study Investigators. Ventilation strategy using low tidal volumes, recruitment maneuvers, and high positive end-expiratory pressure for acute lung injury and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2008 Feb 13;299(6):637-45.
Gattinoni et.al. The role of CT-scan studies for the diagnosis and therapy of acute respiratory distress syndrome. Clin Chest Med. 2006 Dec;27(4):559-70;
Grasso et.al. ARDSnet ventilator protocol and alveolar hyperinflation: role of positive end-expiratory pressure. Am J Respir Crit Care Med. 2007 Oct 15;176(8):761-7.
Bassler et.al. Stopping randomized trials early for benefit and estimation of treatment effects: systematic review and meta-regression analysis. JAMA. 2010 Mar 24;303(12):1180-7.
Wolf et al Mechanical ventilation guided by electrical impedance tomography in experimental acute lung injury. Crit Care Med. 2013 May;41(5):1296-304