Water-vapor-independent inlet system for a respiratory mass spectrometer: application to experiments with a human...

When using a two-stage inlet system in mass spectrometric analysis of permanent gases, changes of water-vapor partial pressure from inspiration to expiration considerably impede the measurements. With this type of gas inlet system, use of a mass spectrometer for measurements on a human centrifuge is rather limited. Introduction of a water-vapor - independent three-stage inlet system permits quantitative analysis of gas mixtures even if the water vapor pressure varies quickly with time. The expiratory oxygen and carbon dioxide partial pressure curves should exemplify that even under extreme acceleration conditions the three-stage system permits simultaneous and continuous mass spectrometric analysis of respiratory gases, with satisfactory response time and a simple experimental arrangement. The method described thus opens up new experimental possibilities for the investigation or respiratory gas exchange phenomena under acceleration conditions.