Percutaneous transtracheal ventilation via a small catheter placed in the trachea and using intermittent jets of oxygen under high pressure has established itself as an important life-support technique. In this study, it was used in a series of 10 experiments performed on dogs at respiratory rates much higher than usually used in clinical practice; i.e., between 20 and 200/min. Tracheal tubes were not used. A 14-gauge Angiocath® was placed percutaneously between the first and second tracheal ring and connected to a fluidic logic-controlled oxygen jet ventilator.
At an FIO2 = 1, the partial pressure of oxygen and carbon dioxide in arterial blood was maintained at a range of 400–575 torr and 20–25 torr, respectively. Thus, satisfactory alveolar gas exchange up to respiratory rates of 200/min was maintained. The intratracheal pressures were low, not exceeding 8 torr during inspiration. At rates above 160, a slight PEEP effect of 2 torr could be achieved. The experiments were performed on paralyzed animals; but after the muscle relaxants were reversed, no interference with spontaneous ventilation was found. There was no hemodynamic impairment using high frequency ventilation, and cardiac index significantly increased at respiratory rates above 160/min. At high respiratory rates, each jet inflation increased the blood return to the left side of the heart as evidenced by the peaks in pulmonary wedge pressure wave form which reflects the left atrial pressure. However, the mean wedge pressure remained unaltered. At the same time, wave form variations occurred in pulmonary artery pressure showing the effects of pulmonary counterpulsation.
The results indicate that it is possible to maintain adequate gas exchange at respiratory rates of up to 200/min at low tidal volumes approaching the dead space volume. It cannot be explained as apneic oxygenation which was used as a control in additional series of experiments. This method led to carbon dioxide accumulation immediately reversible by high frequency jet ventilation.
This technique may offer an alternative to conventional artificial ventilation and/or another method of PEEP with less circulatory disturbance. It may allow patients to breathe spontaneously offering a new way of assisting ventilation. Synchronizing the jet ventilation with heart beat in patients during cardiopulmonary resuscitation may influence the cardiac output during resuscitation.
