2333
Normocapnic ( PACO2 = 40 mm Hg ) ventilatory drive increased significantly ( p less than 0 . 05 ) in six subjects ( Type 1 response ) and decreased substantially in the others ( Type 2 response ) ; with hypercapnia , the changes in drive were attenuated in both groups .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 None