Working alongside so many medical professionals of varying qualification and experience has given me a profound respect for that which I do not know. It is not a rare occurrence that I am confronted with a patient who suffers from a condition that I have never heard of, or with which I am only lightly familiar. These circumstances are particularly frustrating for me, because instead of drawing from my own experience and knowledge, I am forced to rely entirely on what I am told by the nurse or doctor on scene. Many times I feel I am not getting enough information, and other times I feel like the information may be incorrect. Still, my personal lack of education on the subject limits my ability to question, and hampers my greater understanding of this patient who will soon be under my care.
We were called last week to a small clinic for a patient who we were told had shortness of breath. The patient had undergone a procedure during which he was sedated with Propofol and placed on his left side while maintaining his own airway. When the procedure was over and the sedative discontinued, the patient complained of “a little sore throat” and some nasal congestion. At that point in time the measured oxygen saturation (SPO2) dropped from a baseline of 97% to 92% for a few minutes (then returning back to baseline). Concerned, the clinic performed a chest x-ray and thought they saw some infiltrates in the lower lobe of the left lung. They wanted this patient brought to the emergency room for evaluation and, as they put it, twenty-four hour monitoring of the oxygen saturation. They were apparently worried that the patient had aspirated during the procedure and was on the verge of some sort of pulmonary emergency. The patient, now completely without complaint having never noticed any shortness of breath with an oxygen saturation of 99% on room air, looked confused and frightened.
I admit I don’t know much about the risks involved with laterally positioned patients under Propofol sedation. I don’t know how to read a chest x-ray and I only understand a little about what a lung infiltrate is. I have a good familiarity with pulse oximetry and clinical assessment though, and this case raised a few flags with me. I was skeptical, but the doctor told me this story with such earnest interest and concern that I couldn’t help but be impressed. He had the paperwork all ready and asked us if we were capable of monitoring the pulse oximetry while transporting this patient with the lights and sirens on. He said that he had spoken with the physician in the receiving ER and they would be anxiously awaiting our arrival. Barring what I was told and what I saw with the patient, everything about this call seemed to suggest something serious was going on. Still, there the patient sat with a weak story, no complaint, and no sign of any trouble.
I wanted to raise my eyebrows and ask a few tough questions. Are you sure the pulse ox was reading correctly? Didn’t you listen to lung sounds? Didn’t you listen to your patient? How likely is it that the shadow you saw on the chest x-ray is a physiologic change and no emergency at all? Are you sure this patient really needs to go to the EMERGENCY room? Is there something I’m missing here?
…But I couldn’t. The truth is, I don’t really know enough about any of this to be questioning a physician’s impression so directly. I am anecdotally familiar with pulse oximetry and the tendency for the sensor to slip and read low. I know that even healthy patients sometimes read low on the pulse-ox for benign reasons, but I am not sure of the exact mechanisms and science behind pathologic reductions in those same readings. Surely this physician was much more familiar, and I feel I must have some (if even blind) respect for the decisions that come from such experience and training. He must know something that I don’t. The same goes for the x-ray. Surely the radiologist understands the difference between pathologic and physiologic changes on a plain film. Who am I to question him, even if the story just doesn’t seem right?
And so we transported the patient as we were told. I sat in the back and plugged in the pulse-ox, talked with the patient and did my regular assessment. I didn’t find anything wrong with him, and the pulse ox sat at 99% for the duration of the trip. When we got to the emergency room the triage nurse rolled her eyes. She sent the lady to the waiting room.
I know a lot of medics who would have argued with the doctor. Some of them have no problem asking those pointed questions and wearing their distain for a questionable call on their sleeves. Relaying this story to an experienced medic I know, I was chastised and told to rely on my own assessment. “Did the patient look sick to you,” I was asked. When I replied that he didn’t, the answer was “Then he probably wasn’t.”
He’s right, the patient probably wasn’t sick. It was probably a bunch of trumped up nonsense arising from a cautious physician worried about iatrogenic disease and the resulting repercussions. I saw that within my first minute with these people on scene. …But I had no way of being sure. I trust my assessment and I trust my experience. I am proud of my abilities and I think I am a capable provider. Still, I know that there are sharp lines that divide what I know for sure and what I do not, and there is much more of the latter than there is of the former. If a doctor tells me his patient is sick and I don’t think he really is, would it really be prudent to follow my instincts over his? I’m not so sure.
Research after the Fact:
A pulmonary infiltrate is the filling of airspaces within the lungs with fluid, inflammatory exudates, or cells that increase the visual impression of soft tissue density on a chest x-ray. Sometimes this can be a pathologic finding, but there a is also a potential that the condition may be physiologic, where normal airspace folding and collapse creates the same visual impressions (“Atelectasis”). The left lower lobe is the most frequent location of benign atelectaisis in ICU patients. (source)
In a recent study on critical care monitoring, pulse oximetry accounted for almost half of 2525 false alarms (1). In another study looking at patients recovering from anesthesia (2), 77% of low pulse-ox alarms were false in nature. A recent survey (3) found that highly trained medical professionals may have little understanding of pulse oximetry and it's clinical application. In that survey, 30% of physicians and 93% of nurses thought that the pulse-ox measured PaO2. (It actually uses a measure of hemoglobin oxygen saturation to esimate arterial saturation, SpO2).