I recently cared for a patient with severe ARDS. She was deteriorating rapidly and was placed on a rotoprone bed (prone rotation therapy). High PEEP and/ or APRV were not suitable for her as she already had a large amount of subcutaneous emphysema and was at extremely high risk for a tension pneumothorax. The patient had to be frequently bagged and once proned we could not flip her back supine or she would code.
Over the course of about 36 hours the patients O2 sats dropped steadily even with the prone therapy. She favored laying on her right side (good lung down) for her best sat in the 60s. She quickly desatted to the 20s when flat prone and came up to the 40s when laying on her left side.
Now slowly her levels dropped lower and although proning was futile the family was not ready to let go, she was young and it was very sad. Ultimately I ended up seeing her O2 sat drop as low as 3% while rotating prone. There were 3 stars of accuracy the whole time, a great waveform, pulse correlated exactly with the HR and her extremities were warm and pink. The MD told me an O2 sat is not linear at this low of a level but I'm not sure what he meant. Yes, the oxyhemoglobin dissociation curve is not linear but does that mean her sat was not accurate? It would happen time and time again to the single digits, teens and 20s for lengthy periods of time until she ultimately went into the inevitable PEA. (She was a DNR at that point.)
I've never seen anything like it and would love some insight! Thanks.
