Understanding Ventilation Strategies for ECMO Patients at a Community Hospital

Understanding Ventilation Strategies for ECMO Patients at a Community Hospital Kenneth Miller, Matthew McCambridge MD, Neophytos Zambas Background: Extracorporeal Membrane Oxygenation (commonly abbreviated to ECMO) is a modified form of cardiopulmonary bypass utilized in patients with severe yet reversible respiratory and/or cardiac failure (1). The extracorporeal circuit is used to directly oxygenate and remove carbon dioxide from the patient’s blood (2). This type of therapy is used as temporary support for heart and lung function leading to organ recovery or replacement. By maintaining adequate gas exchange and circulating the patients’ blood, the medical intensivist is able to keep the patient alive while the cardiopulmonary system recovers. Blood is withdrawn from the patient’s venous system into an extracorporeal circuit by a mechanical pump before entering an oxygenator. Within the oxygenator, blood passes along one side of a membrane, which provides a blood–gas interface for diffusion of gases. The oxygenated extracorporeal blood may then be warmed or cooled as needed and is returned to a central vein. This specific technique is termed “venovenous” ECMO, because blood is both withdrawn from and returned to the venous system (2). In venoarterial ECMO (VA ECMO) a similar concept is utilized, except the blood is withdrawn from the venous system (femoral vein) and returned into the arterial system (aorta). ECMO has been shown to positively influence patient’s outcomes with compromised cardiopulmonary systems. The most common reasons patients are placed on ECMO are lung compromising and include diseases such as Acute Respiratory Distress Syndrome (ARDS), Pneumonia, Sepsis, and many others. In order to maintain the patient’s lung mechanics and inflation during extracorporeal membrane oxygenation it is necessary to incorporate one of the various forms of mechanical ventilation strategies. Airway Pressure Release Ventilation (APRV), Pressure Control Mandatory Ventilation (PCMV), Pressure Support Ventilation (PSV) for the spontaneously breathing patient, and High Frequency Percussive Ventilation (HFPV) are all ventilatory strategies that can be used in conjunction with ECMO to help maintain the patients lung function, the most common being pressure control mandatory ventilation (PCMV). HFPV is a nonconventional form of ventilation which is utilized when PCMV and ECMO parameters are maximized and gas exchange remains inadequate, the patient has maintained secretions after frequent bronchoscopies, and the patients lung hypo inflation is marked be a compliance of less than or equal to 12cm H2O. HFPV has been shown to work as both an effective ventilator and a powerful mucokinetic. By keeping the patients lungs operational during ECMO management, the patient is more quickly weaned off of ECMO due to maintained lung compliance, elasticity, and ventilation. To further understand the effectiveness and uses of HFPV employed by the VDR ventilator, the data of 40 patients who were placed on ECMO in combination with either high frequency percussive ventilation or pressure control mandatory ventilation was analyzed. Methods: 42 patients were cannulated with ECMO at Lehigh Valley Health Network (LVHN) since January of 2013. All patients’ data was analyzed and a comprehensive ECMO database was created. All of these patients were also placed on mechanical ventilation during their treatment with ECMO. 21 of these 42 patients were treated with high frequency percussive ventilation (HFPV) and various aspects of their data were analyzed to better understand the efficacy of the VDR ventilator. Patient age, etiology, reason for use of HFPV ventilation strategy, RESP score (pulmonary score developed by The Australian and New Zealand Intensive Care Research Centre), and current status of patient were all taken into consideration. By comparing these various pieces of data the effectiveness of the HFPV strategy was determined. Results: The average survival rate recorded in the ELSO database (Extracorporeal Life Support Organization) is 57%. Since the initiation of the ECMO program at the Lehigh Valley Health Network (LVHN) 42 patients have undergone ECMO management and 28 of the 42 patients survived (68.3% survival). One of the patients is currently undergoing ECMO management and therefore this patient’s status was not factored into the survival rate. Of the various ventilation strategies used in combination with ECMO management, HFPV administered by VDR was used on 21 patients at some point during their management, prior to cannulation, during ECMO management, or both. Of the 21 total HFPV administered by VDR patients, 20 of them have been decannulated (taken off of ECMO) and 14 of them survived, giving these patients a survival rate of 70%. The average age of these HFPV administered by VDR patients was recorded at 48.04 years and included 11 female patients and 10 male patients. The most common etiologies of these HFPV administered by VDR ECMO patients included H1N1 (7), Pneumonia (4), and Aspiration (6). Patient ID Numbers Etiology Primary Reason For Being Put On VDR Age Of Patient Total Respiratory Score Status 1884990 H1N1/ARDS Gas Exchange 47 1 alive 1135678 Staph Pneumonia Gas Exchange 32 -3 expired 1952461 H1N1 Gas Exchange 51 4 alive 1416314 Aspiration Gas Exchange 31 4 alive Pre-ECMO VDR Patients: Table 1 Of the 4 ECMO patients who were placed on a VDR prior to ECMO cannulation, 3 of them survived giving a survival rate of 75%. The average age of these 4 patients was found to be 40.25 years. Conclusions should not be drawn from these samples due to the low patient population. It can be concluded however, that HFPV administered by VDR is an appropriate ventilatory strategy than can have positive results. During ECMO VDR Patients: Table 2 Patient ID Number Etiology Primary Reason For Being Put On VDR Age Of Patient Total Respiratory Score Status 792610 Pulmonary Embolism Secretions (Used As Mucokinetic) 46 4 alive 1823618 Aspiration Secretions (Used As Mucokinetic) 51 4 alive 1920871 H1N1 Air Leak/Pneumonia 25 4 alive 1786205 MRSA Pneumonia Secretions (Used As Mucokinetic) 59 4 alive 1951444 Unknown Secretions (Used As Mucokinetic) 39 1 alive 1955049 H1N1 Secretions (Used As Mucokinetic) 44 7 alive 1954753 H1N1 Secretions (Used As Mucokinetic) 47 4 alive 1955399 H1N1 Gas Exchange 62 1 expired 58012 Pneumonia Secretions (Used As Mucokinetic) 66 -1 withdrawal 363686 Aspiration Secretions (Used As Mucokinetic) 32 5 alive 948061 Pneumonia Secretions (Used As Mucokinetic) 45 1 expired 473436 Pneumothorax Lung Recruitment 33 -4 N/A 1544181 Aspiration Pneumonitis Secretions (Used As Mucokinetic) 53 2 alive Of the 13 ECMO patients who were placed on a VDR while undergoing ECMO management, 9 of them survived giving us a survival rate of 75% (one of the patients is currently undergoing ECMO management so their status is not included in the survival rate). The average age of these 13 patients was found to be 46.3 years. Conclusions should not be drawn from this data due to the small sample size. It is clear however that HFPV is a viable ventilatory strategy. Prior to and During ECMO VDR Patients: Table 3 Patient ID Number Etiology Age Of Patient Total Respiratory Score Status 1213954 DKA, Aspirated, Pulmonary Embolism 28 3 alive 1949522 H1N1 61 -1 alive 1259060 Aspiration Pneumonitis 74 1 expired 264715 Aspiration 83 3 expired Of the 4 ECMO patients who were placed on a VDR prior to ECMO cannulation as well as while undergoing ECMO management, 2 survived giving us a survival rate of 50%. The average age of these patients was 61.5 years. Conclusions should not be drawn from this data due to the small sample size. All ECMO VDR Patients: Table 4 Number Of Patients Average Age Average Respiratory Score Survival Rate Pre-ECMO 4 40.25 1.5 75% During ECMO 13 46.3 2.23 75% Both Pre & During 4 61.5 1.5 50% Of the 21 ECMO patients with whom HFPV administered by VDR was utilized, 4 were placed on a VDR prior to ECMO cannulation, 13 were placed on a VDR while undergoing ECMO management, and 4 were placed on a VDR prior to ECMO cannulation and during ECMO management. These 3 sets of patients had survival rates of 75%, 75%, and 50% respectively. Conclusions should not be drawn from this data due to the small sample size. It is clear that HFPV administered by a VDR is a viable and successful ventilatory strategy. VDR ECMO Patients vs. PCMV ECMO Patients: Table 5 Number Of Patients Average Age Average Respiratory Score Survival Rate VDR 21 48.04 1.95 70% No VDR 21 53.26 1.48 66.7% When comparing the VDR and non VDR ECMO patient survival rates at LVHN (70% and 66.7% respectively), with the national average recorded in the ELSO database (57%), it is evident that both strategies produce positive results. Due to the new nature of the ECMO program at LVHN, the sample size is relatively small and therefore concrete conclusions cannot be drawn. Discussion: Since January of 2013 Lehigh Valley Health network has utilized ECMO management on a total of 42 patients with Acute Respiratory Distress Syndrome (ARDS). Lehigh Valley Health network has maintained a survival rate of over 68.3%, which markedly higher than the national average recorded by the ELSO database of 57%. By utilizing various ventilatory strategies (VDR), patients who were not being oxygenated properly using PCMV or were otherwise unstable were more successfully managed. By studying the success rate of High Frequency Percussive Ventilation and the VDR ventilator we hoped to show that not only is this mode of ventilation capable of maintaining lung mechanics during ECMO management, but that it could have improved patient outcomes for patients with whom PCMV is not sufficient. Of the 42 ECMO patients, HFPV with VDR was utilized on a total of 21 patients. These patients were ventilated using HFPV with VDR for various reasons including gas exchange, air leaks, lung recruitment, and sustained secretions. The ECMO patients with whom HFPV was utilized ended up with a survival rate of over 70%. The patients who were ventilated using conventional ventilation (PCMV) had a slightly lower survival rate of 66.7% resulting with an overall survival rate of 68.3%. Looking at this data it is clear that HFPV is not only a legitimate ventilation strategy, but can have extremely positive outcomes on patients who were not responding well to conventional ventilation or were put on HFPV due to other factors (see tables 1-3). We believe that among other factors, LVHN’s utilization of HFPV and the VDR ventilator contribute greatly to the much higher than average survival rates of our ECMO patients. References: Mannino, F., Anas, N., & Cleary, M. (n.d.). Extracorporeal Membrane Oxygenation (ECMO) for the. . Retrieved July 15, 2014, from http://www.calthoracic.org/sites/default/files/ecmopp.pdf Columbia University College of Physicians and Surgeons. (2011). Extracorporeal Membrane Oxygenation for ARDS in adults. The New England Journal of Medicine, 365, 1905-1914