K_Z
Verified Anesthetist
- Joined
- Nov 8, 2010
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Pretty quickly, once breathing has very weak effort, or there is complete respiratory arrest. But, being able to see this very late sign of hypoxia (low oxygen) is dependent on the skill and experience of the observer. People with very pale Caucasian complexions will appear dusky and cyanotic (bluish) more obviously and sooner than people with darker complexions. The lips are often a good indicator, even in people with dark complexions, when oxygen is low, the lips appear pale. Skin often takes on a waxy appearance when someone is very hypoxic.
A little off topic, but let me give an example. Anesthesia students learn that skin color changes are LATE signs of hypoxia in the OR. During induction of general anesthesia, we essentially induce a rapid drug overdose that quickly (within 30 seconds or so) produces a respiratory arrest. It's essential that we take over the process of oxygen delivery and positive pressure ventilation for patients immediately by mask ventilation, in preparation for oral endotracheal intubation. (Unless we're doing a rapid sequence intubation, but that's another discussion all together.) I spend a lot of time with first year students identifying and assessing signs that predict low oxygen in patients. There is nothing so useless as doing the same ineffective thing over and over. We teach rapid decision making. The most important thing is not to have Plan A- B- and C-- but knowing exactly when to bail out of Plan A to Plan B or C, before a catastrophe is created. Hope that makes sense.
I'm not sure what they were talking about on the TV show, with regard to skin color and hypoxia. Was it in reference to the paramedics arriving at the scene of BK's cardiac arrest? If so, cyanosis would not be unexpected. Room air is 21% oxygen, and is far less when that room air is used in mouth-to-mouth ventilation, coupled with the effects of cardiac arrest and chest compressions. I'd expect a patient to be pretty hypoxic in that situation. Paramedics can deliver much higher oxygen concentrations using a bag-valve-mask system attached to a portable oxygen cylinder.
Hope this helps explain.
