Table 1.

Individual effects of placebo and fentanyl on HCVR slopes measured before and 10–20 min after inection

	HCVR Slope (ΔV̇e/ΔPetCO2)
Subject	Preplacebo	Postplacebo	% Change	Prefentanyl	Postfentanyl	% Change
1	2.59	2.44	−6	1.75	1.64	−6
2	1.78	1.71	−4	1.71	1.72	+1
3	2.17	1.91	−12	1.60	1.52	−5
4	1.32	1.70	+29	1.93	2.02	+5
5	3.71	3.91	+6	5.28	4.79	−9
Mean ± SE*	2.31 ± 0.41	2.33 ± 0.42		2.45 ± 0.71	2.35 ± 0.62
6	4.43	4.70	+6	4.53	2.73	−40
7	2.76	2.73	−1	2.71	1.81	−33

HCVR, hypercapnic ventilatory response; V̇e, minute ventilation; Pet_CO2, end-tidal Pco₂.

^*P = 0.87 for preplacebo vs. postplacebo and P = 0.32 for prefentanyl vs. postfentanyl.