We have shown that several types of high frequency oscillator can be modified to produce non-sinusoidal flow patterns. We are convinced that the ability to adjust the wave form is a useful feature of a high frequency ventilator. As the required energy is related to (frequency) all the machines we have examined are large, heavy and noisy. Some problems could probably be overcome by engineering skill. For this reason we have not presented detailed power charts of our machines (built mostly by us). However, one has to admit that none of the devices is sophisticated enough to satisfy a physician who is not enthusiastic for high frequency ventilation. On the other hand, we have treated several patients suffering from bronchiectasis using a linear motor piston heavier than the patient. Asymmetric oscillations helped to clear the airways of purulent sputum. Despite all the noise and unsophisticated appearance of the machine, it was accepted well by the patients because they felt relief. This suggests that, regardless of all obstacles, research in HFV technology should be continued.