Anyway, I was completely freaking out, so I checked his resp rate about a dozen times overnight. But I don't know what the normal resp rate is for an 18-month-old. (Obviously, if he was at 50-60 breaths per minute, I would have rushed him to the ER.) So I sent an email to the other asthma moms....and they didn't exactly know either.
So, in typical "Angry Asthma Mama" fashion, I hit the search engines. Here's what I found, per my email to the moms:
"Tachypnea was defined as a respiratory rate >60 breaths/minute in children 2 >50 breaths/minute in children 2 to 12 months of age, and >40 breaths/minute in children =" border=0>1 year of age."
According to this article, presence of fever raised the rate by 10 breaths per minute. The article's actually pretty interesting if anyone wants to read the whole thing -- it's about using resp. rate to diagnose pneumonia. Here's a link: Tachypnea is a useful predictor of pneumonia in children with acute respiratory infection.
That article led me to this one, which has a fuller age range:
"The World Health Organization's age-specific criteria for tachypnea are the most widely used: a respiratory rate of more than 50 breaths per minute in infants two to 12 months of age; more than 40 breaths per minute in children one to five years of age; and more than 30 breaths per minute in children older than five years. (14)"
And yes, the context was diagnosing pneumonia.
Hope someone else finds this useful!