The effect of simulated obstructive apnoea on intraocular pressure and pulsatile ocular blood flow in healthy young adults.

AIM To investigate the effect of negative inspiratory effort, as generated by the Mueller manoeuvre, on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in healthy young adults. METHODS Seven volunteers with no history of systemic or ocular disease were recruited (mean age 30.7 years, range 25-40 years, M/F: 4/3). After initial instruction and practice of the Mueller manoeuvre, baseline measurements of IOP and POBF were obtained for both eyes after 10 and 15 minutes of rest, respectively, in the supine position. Thereafter, the Mueller manoeuvre was performed creating a mouthpiece pressure of -20 cm H(2)O, for at least 15 seconds followed by a 5 minute rest. The manoeuvre was repeated with a mouthpiece pressure of -40 cm H(2)O. IOP and POBF were measured 5-15 seconds into the manoeuvre for both -20 cm H(2)O (M2A) and -40 cm H(2)O (M4A) and directly upon recovery (after two respiratory cycles) from each manoeuvre (M2B, M4B). Baseline measurements were compared using paired t test, whereas manoeuvre induced changes in IOP and POBF were analysed individually using repeated measures ANOVA with Student-Newman Keuls post hoc analyses. Linear regression analysis was used to investigate a dose-response effect. RESULTS No significant differences were found between baseline measurements so they were subsequently pooled. There was a significant decrease in IOP for M2B (-9.2%, p<0.05), M4A (-13.8%, p<0.05), and M4B (-15.6%, p<0.05), relative to baseline. A dose-response relation was found for the effect of mouthpiece pressure on measurements 5-10 seconds into the manoeuvre (M2A and M4A, r = 0.54, p = 0.045). There was a trend of increased POBF relative to baseline for all measurements; however, significance was reached for M4B only (p = 0.039). CONCLUSION It was shown that forced inspiratory efforts as generated by the Mueller manoeuvre are associated with a dose dependent decrease in IOP and a concomitant increase in pulsatile ocular blood flow.