Proning is one of the only evidence-based techniques to affect the mortality of ARDS patients. I've been wanting to do an episode on proning for a while. Serendipitously, Joseph Tonna recently published a piece on the topic in the ACEP Critical Care Section Newsletter. Dr. Tonna is a fellow in Anesthesia Critical Care at the University of Washington. He recently did a rotation on a refractory ARDs unit (read about all of his experiences below) and learned the way they prone. We discuss it on the podcast today.
Article on the Physiology of Proning
Meta-Analysis of RCTs on Proning
Crit Care Med 2014;42(5):1252
LITFL's CCC Entry on Proning
Video on Proning from the Guerin Study
Here is the Dr. Tonna's Original Piece:
Prone Positioning: An experience of actually doing it
by Joseph E. Tonna, MD, Associate Newsletter Editor. This piece was originally published in the ACEP Critical Care Section Newsletter
Most intensivists have read Guérin’s 2013 NEJM study on the mortality benefit of prone positioning. Previous studies [1,2] have established that dorsal consolidations improve when the patient is placed prone. Taken together, the practice of prone positioning in select patients makes sense. Despite this, I haven’t found that it is done as often as one might infer from the robustness of its benefit in this study or others. In my experience, while we are likely to notice the profound dorsal pulmonary consolidations on our patient’s CT scans, we don’t take the next step and actually prone the patient until we have already progressed further down the path towards worsening hypoxemia—often only when the pO2/FiO2 ratio is well below 150 on upwards of 70% FiO2. At this stage, we begin to consider the patient “refractory” and allow ourselves to begin the intellectual path of discussing the evidence for and risk/benefit or cost/benefit of therapies like inhaled nitric oxide (iNO), epoprostenol, prone positioning, high frequency ventilation, paralysis or extracorporeal membrane oxygenation (ECMO). The evidence for many of these therapies is thin at best, and given how infrequently we reach these states of worsening refractory hypoxemia, and gain personal experience with implementing them, many newly trained intensivists will finish training having managed no more than a handful of patients on these therapies. As we all know, increased volume leads to increased comfort and competence; so as part of my fellowship training, I wanted to know what it looked like to routinely implement these therapies. Did they work? What did this process actually look like?
I had the opportunity recently to train at Legacy Emanuel Medical Center in Portland, OR at the Randall & Emanuel Severe Cardiopulmonary Failure and ECMO (RESCUE) Center under two talented surgical intensivists, Drs. Andrew Michaels and Sandra Wanek. Patients brought to this unit have already failed conventional therapies for hypoxemic respiratory failure, and often already have a P/F of <100 on 80-100% FiO2. These patients have not only failed excellent critical care, but most have failed alternative therapies such as airway pressure release ventilation (APRV), iNO, or paralysis. Among the therapies implemented the RESCUE center for this subset of patients, prone positioning is routine.
Who to Prone?
Given the practical risks of proning, I wanted to find out exactly when, why, and how it was done. I watched the process, participated in it and talked extensively with one of its champions at Legacy Emmanuel, Christine Lasich, RN. Proning was done in a very simple and sensical way. It was initiated if the patient had hypoxemia with a P/F of roughly <150 and the thoracic CT scan showed significant dorsal consolidation. Without dorsal predominant consolidation, even with refractory hypoxemia, the prone position was not felt to be beneficial.
How to Prone
The way in which the patient was proned was also simple yet effective. All proning at the RESCUE center was done manually. The patient would have telemetry leads disconnected and have stacked pillows placed on their chest, lower pelvis and shins in a way to elevate the head, allow the abdomen to hang free and protect the knees and feet. The patient was then covered in a top sheet above the pillows and bundled tightly. The flip would involve 3 people per side, with highly experienced people at the chest and pelvis. Two respiratory therapists would be at the head, one managing the head, airway and pillow, and another managing the tubing and providing backup. One nurse would manage the IV lines if they absolutely couldn’t be disconnected, though they most often were after appropriate medication doses (By disconnecting the central lines, the proning movements could be more brisk and complete without the risk of traumatic removal.) The arterial lines were almost always unhooked. Most patients were also on ECMO and would have a dedicated nurse at each cannula. The specialist at the foot of the bed would oversee the whole process and monitor the bypass circuit. The pulse oximeter would be left until the last minute to monitor saturation and heart rate. The process was announced overhead prior to flipping so that assistants could begin to free themselves. One RT would ensure the ETT was taped and secured without hard plastic holders or bite blocks to avoid oral trauma while the bedside nurse would disconnect the leads, bolus analgesia, sedation and often paralytics, and ready the patient so that the assistants could step in, participate in the “time out” and then help flip. As such, additional help was only needed for no more than 5 minutes but during this time, the room had no fewer than 8-9 people plus anyone needed for the ECMO circuitry. It felt very safe and controlled.
Once prone, meticulous care was given positioning the patient’s face, eyes and endotracheal tube such that pressure points were protected, oral trauma to the lips and gums was avoided, and the eyes were lubricated and closed. Frequent assessments and adjustments were made of all these parts to avoid pressure wounds. Given the aforementioned internal jugular ECMO cannulas, patients were positioned face down in the bed rather than “head to side,” and so these frequent assessments were of utmost importance. The RT or nurse would ensure that at any given time s/he could pass the endotracheal suction catheter without resistance. It was common in this face down position to have significant facial and lingual edema, and on speaking with experienced providers and nurses, in most patients without such cervical limitations, there are distinct advantages to a “head to side” position, including easier oral care and less edema. Feeding was continued while prone as long as the patient’s feeding tube was post pyloric. If not, feeds were held but the total daily goals were achieved by doubling the feeding rate while supine. I found this ensured the patients continued to receive adequate nutrition.
How Much Proning?
Proning was carried out in units of between 4 and 16 hours, with ABGs obtained prior to, 30 minutes after, and then at 4 hour intervals along the way to assess for trending improvement or zenith. ABGs were then repeated 30 minutes or so after supination and with these data points, trends could be drawn to see each patient’s optimal duration of prone position. Some patients with dorsal consolidation didn’t show any improvement in their PaO2 after proning. I had been used to the 16h prone/8h supine approach, without adjustment for changes in PaO2 during the day, and I was surprised to see that while some patients achieved peak PaO2 late while prone, or peaked early and maintained elevated PaO2 while prone, others peaked and started to fall by 4 to 6 hours, only to then have a rise in their PaO2 upon supination.
Patients at the RESCUE Center also had initiation of proning whenever or continued as long as the patient demonstrated the ‘inclusion’ criteria already mentioned, sometimes two weeks into their disease course. While many might critique this tailored approach to dynamic PaO2 changes as akin to the “better PaO2, but higher mortality” of the control arm of the ARDSNet study, it also harkens to a policy of “intervention, assessment, repeat” that defines not only good critical care but good medicine. While the Guérin study showed that 16h of prone positioning early in the course was beneficial, it is not known if intermittent prone positioning (IPP, as it is known) is better or worse. In the face of empiric data suggesting a benefit and no data to suggest harm, the providers at the RESCUE center argue that this is simply practical and attentive critical care . While individual interventions are difficult to isolate among bundled care, the incredible outcomes support them.
Over my month I was able to participate in the care of multiple patients transferred for refractory hypoxemia, who through aggressive yet thoughtful interventions were able to be rescued from critical condition to a neurologically intact survival. Utilization of prone positioning aggressively and often was a key component of this care. It made physiologic sense, and had been practiced so often that the process was regimented and efficient among the staff. The number of staff required for the actual flip was far more than I had otherwise seen, but the process was also more regimented and, I thought, safer. I saw daily the benefit of prone positioning and came to ask myself why it wasn’t done earlier and more often, before patients reached “refractory” states of hypoxemia. While many would argue that without refractory hypoxemia, the risks of prone positioning, especially among unfamiliar providers exceeds any benefit. It’s hard to dispute that it may not be safe to have unpracticed providers proning patients, I think it’s also easy to believe that alveolar recruitment with improved oxygenation and ventilation leads to lower FiO2s, lower ventilatory pressures, and less atelectrauma, and fewer invocation of less proven, higher risk therapies. Like all new or unfamiliar practices, there are risks, yet the marked improvement in oxygenation and ventilation I saw with routine early prone positioning suggested to me that this was a skill worth learning so that I too could implement it safely and effectively to the benefit of my patients.
1. Gattinoni L, Pelosi P, Vitale G, et al. Body position changes redistribute lung computed-tomographic density in patients with acute respiratory failure. Anesthesiology. 1991;74(1):15–23.
2. Protti A, Chiumello D, Cressoni M, et al. Relationship between gas exchange response to prone position and lung recruitability during acute respiratory failure. Intensive Care Med. 2009;35(6):1011–7.
3. Michaels AJ, Wanek SM, Dreifuss BA, et al. A protocolized approach to pulmonary failure and the role of intermittent prone positioning. J Trauma Acute Care Surg. 2002;52(6):1037–47.