No abstract

Prophylactic antibiotics appear to have no benefit in revision, clean head and neck surgery. Further studies in larger populations and other settings are needed. (ClinicalTrials.gov number NCT01980082, clinicaltrials.gov/ct2/show/NCT01980082).

Concomitant continuous measurements of the steady-state gas composition of the middle ear and of the venous blood were recorded by mass spectrometry in four guinea pigs. The following mean values were obtained for the partial pressures of middle ear gases; nitrogen + argon, 606.4 mm Hg; oxygen, 46.2 mm Hg; and carbon dioxide, 60.2 mm Hg. The corresponding values for the venous blood were as follows: Nitrogen + argon, 563.4 mm Hg; oxygen, 38.0 mm Hg; and carbon dioxide, 61.4 mm Hg. The similarity of the steady-state gas composition of the middle ear to that of the venous blood suggests that the partial pressures of the gases in the middle ear are controlled by interchange with gases present in the blood.