10. What is the frequency of calm breathing in a normal person? What is bradypnea and tachypnea; what is the clinical significance?

Normal human respiratory rate is 16 to 18 times per minute. A respiratory rate of less than 12 breaths per minute is considered bradypnea, and a respiratory rate of more than 20 breaths per minute is considered tachypnea. Bradypnea is caused by overdose of sedatives or anesthetics, and increased intracranial pressure. Tachypnea is seen in fever, pain, anemia, hyperthyroidism, and heart failure.