Advances in Pulmonology and Lung Surgery

“We’ve known for some time that it is certainly feasible to pursue early mobilization in patients with critical illness,” says Darryl Abrams, MD, Associate Medical Director and Director of Research of the Medical ECMO Program in the Center for Acute Respiratory Failure at NewYork-Presbyterian/Columbia University Irving Medical Center. “Active rehabilitation of patients in the ICU can lead to better outcomes, shorter ICU length of stay, potentially shorter time on the ventilator, less delirium, and better physical conditioning when they leave the hospital. However, the question for a long time has been whether mobilization is feasible and safe to do in ECMO patients. Do they have equally favorable outcomes or is it too risky with no benefit.”

Dr. Darryl Abrams

According to Dr. Abrams, there have been small case series and cohort studies examining the feasibility of early mobilization of ECMO patients. However, he notes the importance of distinguishing between patients receiving the support as a bridge to transplantation from those with severe acute respiratory distress syndrome (ARDS) receiving ECMO as a bridge to recovery. “When a patient is on ECMO for respiratory failure, there are two paths,” says Dr. Abrams, who is also Associate Professor of Medicine at Columbia. “The patient either gets better or gets transplanted. Patients with ARDS and acute illnesses are usually not transplant candidates and so their only option is to recover, although the more recent experience with COVID-19-associated ARDS has begun to challenge that paradigm.”

Active physical therapy is increasingly recognized as beneficial for those individuals receiving ECMO as a bridge to transplantation to maintain transplant candidacy. “A major point of emphasis in the transplant population is keeping them physically fit and well enough to survive the transplant itself and then do well afterwards,” says Dr. Abrams. “We emphasize active physical therapy and early mobilization to maintain, if not improve, their physical conditioning as they wait for transplant.”

“In placing cannulas into blood vessels to support patients with ECMO, some configurations are potentially more unstable than others,” continues Dr. Abrams. “The traditional mode of support for respiratory failure, in the absence of cardiac failure, is venovenous ECMO, where one cannula withdraws blood from a central vein and the other allows the blood to be pumped back into a vein after going through a gas exchange device. The cannulas are secured and sutured in place, and it is generally felt to be a safer mode for mobilizing. Patients with concomitant cardiac involvement – usually right heart failure and pulmonary hypertension in this population – require arterial support. One cannula is in a vein, the other cannula is in an artery, and that is felt to be a potentially riskier configuration from a mobilization perspective. If there were a decannulation from the venous system, bleeding is relatively slow compared to decannulation from the arterial system, in which bleeding is brisker and can be catastrophic.”

Another important consideration in mobilization, notes Dr. Abrams, is which vessels are identified for cannula placement. A cannula in the internal jugular vein can be easily observed and is secure. “But one of the common places is the femoral artery in the groin,” he says. “During rehabilitation, the patient may be bending at the hip or walking and there’s more of a concern that there could be complications be it kinking of the tubing or even decannulation.”

While there is general agreement on the importance of maintaining strength and conditioning in patients awaiting transplantation, there is little data on the impact of early mobilization among patients receiving ECMO as a bridge to recovery from acute illness. To that end, Dr. Abrams and colleagues in Columbia’s Division of Pulmonary, Allergy and Critical Care recently led a large single center study to determine whether there are factors associated with achieving out-of-bed versus in-bed physical therapy in ECMO-supported patients and whether mobilization with femoral cannulation is safe and feasible. Also participating in the investigation were representatives from the Department of Surgery, Department of Medicine, Division of Cardiac, Vascular and Thoracic Surgery, Clinical Perfusion and Anesthesia Support Services, Department of Rehabilitation Medicine, and Nursing.

“There’s a great impetus to get a patient out of bed and walking to demonstrate to the transplant team that this patient is fit and strong enough to continue to be considered for transplantation, thereby justifying taking a greater risk.” — Dr. Darryl Abrams

The study included 511 patients who were supported with ECMO in the Medical Intensive Care Unit at NewYork-Presbyterian/Columbia between April 1, 2009, and January 31, 2020. Results of the study, which were published in the January 2022 issue of the Annals of the American Thoracic Society, included:

• Of the 511 patients, 141 patients received ECMO as a bridge to lung transplantation and 370 patients as a bridge to recovery
• 177 of the 511 patients (35 percent) underwent active physical therapy and were included in the analysis
• 124 of the 141 patients (88 percent) receiving ECMO as a bridge to lung transplantation and 53 of 370 patients (14 percent) undergoing ECMO as a bridge to recovery underwent active physical therapy
• 177 patients accounted for 2,706 active physical therapy sessions, with 138 patients (78 percent) achieving out-of-bed activity
• In total, 108 patients (61 percent) ambulated (1,284 sessions), 34 of whom had femoral cannulae (accounting for 250 ambulatory sessions)
• Bridge-to-transplant as the indication for ECMO, venovenous ECMO, later cannulation year, and higher Charlson comorbidity index were associated with increased odds of achieving out-of-bed versus in-bed physical therapy, whereas invasive mechanical ventilation and femoral cannulation were associated with decreased odds of performing out-of-bed activities
• Adverse events occurred in 2 percent of sessions

“As expected, bridge-to-transplant patients are more likely to be out of bed versus in bed for activity because the whole point is to keep these people physically fit,” says Dr. Abrams. “There’s a great impetus to get them out of bed and walking to demonstrate to the transplant team that this patient is fit and strong enough to continue to be considered for transplantation, thereby justifying taking a greater risk. Those patients who were receiving venovenous ECMO were also more likely to be able to achieve out-of-bed versus in-bed therapy.”

The Columbia investigators found that among the factors that made it less likely for a patient to get out of bed for activity was the ongoing need for invasive mechanical ventilation. “One of our strategies, if possible and especially for bridge-to-transplant patients, is to eliminate the ventilator. Both ECMO and the ventilator bring risks and can limit activity leading to adverse events. ECMO is often providing more effective respiratory support than the ventilator and the patient would likely feel better not having a tube in their throat, and it would be best to avoid the risk of developing ventilator-associated complications.”

“The sheer volume of patients that we mobilize includes a high percentage who were out of bed and walking, and a high percentage of those had a femoral cannula in place,” says Dr. Abrams. “We demonstrated that it is not a hindrance to be able to perform physical therapy with these patients. But within that population, there are certain factors that may contribute to the decision on who to try to mobilize or how to cannulate a patient if anticipating mobilization. The number of patients eligible for this are much fewer and further between. Some patients are deeply sedated. They might be paralyzed. They’re still very marginal with their gas exchange even with ECMO, such that it's not worth the risk of trying to lift them up and get them out of bed.”

Adds Dr. Abrams, “It’s important for ECMO centers to recognize there is a lot of selection bias and confounding here. But if you’re thinking of starting a mobilization program, or you want to try to mobilize a particular patient, successful mobilization, especially out-of-bed, may depend on whether the patient is supported as a bridge to recovery or bridge to transplant, whether the ECMO configuration is venovenous or venoarterial, and where you place the cannulas, if you have a choice. Success is based on a combination of all these factors, and, above all, the involvement of an interprofessional, multidisciplinary team.”