Intraocular pressure changes during ventilator weaning: a prospective observational study highlighting PaCO₂-related physiological monitoring signals in ICU patients.

Purpose This study aimed to evaluate intraocular pressure (IOP) as a time-dependent physiological monitoring parameter during ventilator weaning and to explore its association with PaCO₂-related respiratory changes. Methods In this prospective observational study, adult ICU patients receiving mechanical ventilation and undergoing weaning were enrolled. Patients with glaucoma, prior ocular surgery, or inability to tolerate weaning were excluded. IOP was measured in both eyes before weaning (T0), during spontaneous breathing (T1), and after completion of weaning (T2). Ventilator mode, positive end-expiratory pressure (PEEP), sedative agents, and spontaneous breathing trial (SBT) method (pressure support ventilation [PSV] or T-piece) were recorded. A protocol-defined IOP increase was defined as an elevation of ≥ 1.0 mmHg in at least one eye between T0 and T2. Associations between clinical variables and IOP changes were analyzed using repeated-measures analysis and multivariable logistic regression. All measurements were performed under standardized bedside ICU conditions; T1 was obtained 30 min after initiation of spontaneous breathing and T2 30 min after completion of weaning. Results Sixty-four patients were assessed, and 45 were included in the final analysis. Mean IOP values showed minimal change over time. In exploratory multivariable logistic regression, an increase in arterial carbon dioxide tension during weaning (ΔPaCO₂) was associated with the protocol-defined IOP increase (odds ratio [OR] = 1.66; 95% confidence interval [CI], 1.13-2.45; p = 0.010). No significant associations were observed with other ventilator-related or clinical variables. Conclusion The transition from mechanical ventilation to spontaneous breathing in ICU patients was not associated with a significant increase in mean IOP. However, small individual-level IOP increases were observed, and these were associated with increases in PaCO₂ during weaning. These findings should be interpreted as exploratory physiological observations. Further studies are required to determine whether these observations have clinical relevance.