Background: We evaluated the effect on the respiratory gas exchange of the 30° head-down position and the complete covering of the face by sterile drapes. These are used to cannulate the internal jugular vein and position the pulmonary artery catheter in the cardiosurgical patient. During the two manoeuvres, 20 coronary patients and 10 patients with end-stage heart disease were supplied with oxygen (FiO2 =0.4) by a Venturi mask, while 20 coronary patients breathed room air. The arterial blood samples to measure oxygen (PaO2) and carbon dioxide (PaCO2) tension and oxygen saturation (SaO2) were analysed by a blood gas system.

      Results:
      The contemporary application of the head-down position and the
            drapes over the face significantly increased PaO2 and
            SaO2 in all the patientssupplied with oxygen. Without the head-down
            position, leaving the drapes over the face, did not significantly change the
            two parameters in the coronary patients supplied with oxygen, but induced a
            significant increase in PaO2 and SaO2 in the patients
            with end-stage heart disease. In the coronary patients that were breathing room
            air, PaO2 and SaO2 were stable throughout the study.


      Conclusions:
      We conclude that the 30° head-down position and the complete
            covering of the face by drapes does not interfere with respiratory gas exchange
            and can be safely performed in coronary patients supplied with oxygen or
            breathing room air and in patients with end-stage heart disease supplied with
            oxygen (FiO2 of 0.4).