Table 2

The effects of morphine on breathing during sleep

Placebo mean (SD)Morphine mean (SD)Adjusted delta
mean (95% CI)
Treatment effect
(P)
T90, min4.0 (9.6)6.2 (17.8)2.1 (−2.2 to 6.4)0.33
T90, %TST 1.2 (3.1)1.6 (4.6)0.4 (−0.7 to 1.6)0.46
T95, min92.1 (89.0)133.4 (119.1)41.2 (16.2 to 66.3)** 0.002
SpO2 nadir, %87.2 (5.7)86 (5.7)−1.3 (−2.6 to −0.1)* 0.036
Mean PtcCO2, mmHg43.7 (4.1)45.9 (4.1)2.1 (1.1 to 3.1)*** <0.001
Mean SpO2, %95.4 (1.3)94.9 (1.5)−0.5 (−0.7 to −0.2)*** <0.001
ODI, /hour14.3 (16)15.6 (15.6)1.4 (−1.6 to 4.3)0.36
AHI, /hour19.1 (17.7)20.7 (19.1)1.6 (1.9 to 5)0.36
OAI, /hour4.7 (7.2)7.1 (11.3)2.4 (0.3 to 4.5)* 0.026
HI, /hour12.7 (11.9)10.9 (9.4)−1.7 (3.9 to 0.4)0.12
CAI, /hour0.8 (1.3)1.2 (2.0)0.4 (0.03 to 0.9)0.068
MAI, /hour1.0 (2.3)1.5 (2.9)0.4 (0.1 to 1.0)0.096
ArI, events/hour25.5 (13.9)27.1 (14.8)1.7 (1.9 to 5.2)0.35
Hypopnoea to apnoea ratio 0.71 (0.2)0.64 (0.24)−0.07 (0.12 to −0.01)* 0.015
Mean apnoea length, s20.3 (5.8)20.6 (6.9)−0.2 (2.2 to 1.7)0.17
Supine proportion, %32.3 (28.6)40.9 (30.4)8.6 (3.0 to 14.2)** 0.003
  • Bold texts indicate p<0.05.

  • n=60. Hypopnoea to apnoea ratio = percentage of AHI made up of hypopnoeas, where 1 = 100% hypopnoeas and 0 = 100% apnoeas. Morphine effect tested by mixed model of repeated measures controlling for treatment order, age, BMI if appropriate. For T90 min and T90 %TST, difference between morphine and placebo, with 95% confidence limits, and P-value were adjusted for age, BMI, baseline T90, baseline SpO2 and proportion of sleep time spent in supine position. Supine proportion = percentage of TST spent supine.

  • AHI , apnoea–hypopnoea index; ArI, arousal index; BMI, body mass index; CAI, central apnoea index; HI, hypopnoea index; MAI, mixed apnoea index; OAI, obstructive apnoea index; ODI, oxygen desaturation index; PtcCO2, pressure of transcutaneous carbon dioxide; SpO2 nadir, oxygen saturation nadir; T90 min, sleep time spent below 90% oxygen saturation; %TST, percentage of total sleep time; T95, sleep time spent below 95% oxygen saturation.