Figure 2From: Melatonin therapy to improve nocturnal sleep in critically ill patients: encouraging results from a small randomised controlled trialSemi-logarithmic plot of mean melatonin plasma concentration (± standard deviation [± SD]) versus clock time after a 10-mg oral solution dose administered at 9 p.m. in critical care patients. *4 a.m. data point. Mean concentration value minus SD is a negative number and cannot be represented on a logarithmic scale.Back to article page