Last week, I went in to my local student health center because the virus I had been working on the week prior finally had me hacking up bloody stuff. Before, it was more of the low-grade fever, feel like shit variety of virus.
The emergency care nurse stuck a pulse Oximeter on my finger, declared that I was at 98% saturation, and therefore did not have pneumonia and could go home.
Question 1: Exactly how accurate would a pulseox be at diagnosing pneumonia? By my thinking, I would have to have pretty severe pneumonia before I’m not saturating my hemoglobin significantly. But maybe there is some aspect of physiology that I’m forgetting.
Question 2: What does walking pneumonia feel like?
The pulse oximeter has little to nothing to do with diagnosing pneumonia. The pulse-ox works by red and infrared light through your skin. Hemoglobin (Hb) is made up of 2 dimers. When oxygen is bound to Hb, the 2 dimers shift relative to each other. This causes them to reflect light differently, which is what the pulse-ox measures. The downsides to pulse oximetry is that it can’t tell you what the Hb is actually bound to (Hb has a much higher affinity for CO that O2), and it can be difficult to get accurate readings in people with poor circulation or cold extremities.
The docs will be able to say better than me how to diagnose pneumonia, I’d be looking at lung sounds, temperature, and other symptoms. I think a diagnosis typically involves a chest x-ray, but I could be wrong about that.
Low blood oxygen saturation would be a sign of pneumonia, but it is more likely that the nurse/doctor/whoever was basing their diagnosis based on several general observations and not the results of just the pulse oximetry. Just listening to your breathing can be a great indicator of pheumonia.
See, I figured that they would rely on other diagnostics.
The doctor did listen to my chest and correlated that with me overall feeling better and being afebrile to decide that I wasn’t having a secondary bacterial infection, and that makes sense. So I got no beef there.
It was the triage nurse who put the pulse ox on me and declared that I was pneumonia free before I saw the doc. Weirdo.
Anyone know how severely my lungs would need to be compromised before the hemoglobin saturation would shift? I don’t think I would have casually strolled into the waiting room if my pulseox was below 90%.
Assuming the nurse was competent, what you got was a shorthand way of saying that you did not have an infectious condition serious enough to require extensive evaluation or inpatient treatment.
Making this inference based solely on a pulse oximeter reading is mostly reasonable but of course there is still a margin for error. While it is popular to divide respiratory infections into those which affect the larger airway tubes (“bronchitis” e.g., or “upper respiratory infections” e.g.) and those which affect the substance of the air-exchanging sacs themselves (“pneumonia” e.g., or “lower respiratory infections”), from a clinical standpoint there are other ways to divvy up respiratory infections which are more useful.
Froma purely practical standpoint the typical issues are whether or not there is a therapy which will help (antibiotics; bronchodilators…) and whether or not you are sick enough to warrant hospitalization for more intensive monitoring and care. Other considerations might include your potential for sudden deterioration, your underlying robustness of physiology and capacity to fight illness, and whether or not other conditions (pulmonary embolus, lung abscess, tuberculosis and its pals…) should be considered in addition to ordinary illnesses.
In general, a severe pneumonia of any etiology would lower a room-air pulse ox below 98%. On the other hand, a number of non-emergent conditions can lower the pulse ox quite a bit (associated bronchospasm, for instance). Low pulse ox’s get further workup; normal pulse ox’s are only one of many indicators that everything is OK. If other signs and symptoms are out of bounds, a normal pulse ox does not rule out serious respiratory or cardiovascular illness.
Although I have treated many inpatients and outpatients who have pneumonia, I have no idea what “walking pneumonia” is. I assume it’s some sort of term used (inconsistently) to describe patients who have a lower respiratory infection but who are less ill than some other group. It is not a clinically useful term.
As an aside, bloody sputum is not typically ascribed to viral respiratory illness.
Anecdote Note: kids and adults are *very *different when it comes to these things, so take this with a grain of salt the size of Cleveland: when my 3 year old daughter gets bronchiolitis (with every cold), her stats will get down into the high 80’s and she’s more or less fine, just prone to resting between play more often than normal and working a bit harder to breathe. Last time she was down to 82, and she was very tired and there were lots of worried looks in the pediatricians office and murmurs of ER admissions and oxygen tents, but a couple rounds of Albuterol brought her numbers back up into the mid-90’s and they let me take her home. So for HER personally and perhaps no one else in the world, the big dip happens below 88 or so.
On a brighter note, she’s now so used to the PulseOx that she clips it on her own finger when we get into the office! :rolleyes: