Summary of Experimental and Clinical Features of High‐Frequency Positive‐Pressure Ventilation—HFPPV

In order to eliminate the respiration‐synchronous variations in blood pressure and heart rate a new method of artificial positive‐pressure ventilation was developed—high‐frequency positive‐pressure ventilation (HFPPV). Since 1967 this technique has been applied in various forms and under greatly differing technical and physiological conditions. The ventilatory pattern in intermittent positive‐pressure ventilation (IPPV) is the result of the combined conditions created by the ventilator and the pulmonary systems and an obvious controversy between physics and physiology arises in the designing of ventilators to match the breathing patterns and pulmonary and cardiovascular physiology of patients with seriously impaired vital functions. A summary is given of the different types of techniques and the physiological parameters, morphology and functions studied in HFPPV. In order to overcome the increased VD/VT ratio and to provide satisfactory alveolar ventilation in HFPPV, certain basic technical and functional characteristics must be inherent in the ventilator system used. For example in the patient circuit of ventilator systems for HFPPV of an “open” character and for volume‐controlled ventilation there is a negligible compression volume. In a ventilator system for volume‐controlled ventilation, which has a negligible compression volume, inspiration has a decelerating character and the roles of volume as a primary parameter and pressure as a secondary parameter should theoretically function in a desired manner. The major characteristics of the ventilatory pattern of HFPPV are (a) a ventilatory frequency about three times as high as in conventional IPPV, (b) smaller tidal volumes and lower airway pressures than in conventional IPPV, (c) inspiratory flow (usually of a decelerating character) without an end‐inspiratory plateau, (d) positive intratracheal and negative intrapleural pressures throughout the ventilatory cycle (presumably with even and efficient pulmonary gas distribution), (e) less circulatory interference than in conventional IPPV and (f) reflex suppression of spontaneous respiratory rhythmicity at normoventilation. These functional characteristics of artificial ventilation would seem to be of decisive importance for the pulmonary and cardiovascular physiology of patients with seriously impaired vital functions.