Prevention of ventilatory disturbance while in the face-down position after macular hole surgery

The aim of the present study was to assess the effects of the face-down position on ventilatory function after macular hole surgery. The transcutaneous carbon dioxide tensions (tcPCO2) were measured in five patients who had undergone intraocular tamponade and in 17 normal subjects. The tcPCO2 measurements were done in patients following vitrectomy in the sitting position and in the prone position with their faces down over the semi-closed spaces of the conventional mats. In normal subjects, minute ventilatory volumes (V.E) were measured simultaneously with tcPCO2 in the sitting position and prone position. The newly introduced face-down mats (new mats) for the prone position were also tested in the normal subjects. In normal subjects, VE in the prone position with the conventional mats was significantly lower than that found in the sitting position (5.06 +/- 1.55 vs 6.06 +/- 1.64 L/min; P < 0.002). The tcPCO2 in the prone position was significantly higher than that in the sitting position (41.7 +/- 2.1 vs 38.0 +/- 1.9 mmHg; P < 0.0001). In post-vitrectomy patients, tcPCO2 in the prone position with the conventional mats was significantly higher than that in the sitting position (41.4 +/- 1.7 vs 38.6 +/- 2.2 mmHg; P < 0.02). The tcPCO2 in the prone position in normal subjects was significantly lower using new mats than that when using conventional mats. The use of conventional mats during a prone position, increased the tcPCO2 values when compared to the tcPCO2 values obtained during the sitting position in patients following vitrectomy. This could be due to either a decrease of the VE caused by limited thoracic movement or rebreathing of the exhaled gas over the semi-closed space, or both. The new mats might be useful in alleviating the increase of tcPCO2 by eliminating the rebreathing of the exhaled gas.