RESPIRATION AND THE AIRWAY Frequency dependence of lung volume changes during superimposed high-frequency jet ventilation and high-frequency jet ventilation

Editor’s key points † Superimposed high-frequency jet ventilation (SHFJV) involves simultaneous normal frequency (12–20 min) and high-frequency jet ventilation (HFJV) (.500 min). † SHFJV may improve ventilation and gas exchange compared with HFJValone, but the optimum frequencies for SHFJV are unknown. † In this animal model, end-expiratory and tidal volumes determined by opto-electronic plethysmography were greater, and gas exchange was improved with SHFJV. † Ventilation was reasonably consistent with SHFJV up to a frequencyof 1000 min, whereas it became ineffective using HFJV at frequencies .300 min. Background. Superimposed high-frequency jet ventilation (SHFJV) has proved to be safe and effective in clinical practice. However, it is unclear which frequency range optimizes ventilation and gas exchange. The aim of this study was to systematically compare high-frequency jet ventilation (HFJV) with HFJV by assessing chest wall volume variations (DEEVCW) and gas exchange in relation to variable high frequency. Methods. SHFJV or HFJV were used alternatively to ventilate the lungs of 10 anaesthetized pigs (21–25 kg). The low-frequency component was kept at 16 min in SHFJV. In both modes, high frequencies ranging from 100 to 1000 min were applied in random order and ventilation was maintained for 5 min in all modalities. Chest wall volume variations were obtained using opto-electronic plethysmography. Airway pressures and arterial blood gases were measured repeatedly.