Resp Care
-
Over the past 50 years, a variety of techniques have been developed that have in common the insufflation of gas into the central airway to facilitate carbon dioxide (CO2) clearance. These include continuous insufflation of oxygen, transtracheal jet ventilation, high frequency jet ventilation, transtracheal oxygen administration, intratracheal pulmonary ventilation, and tracheal gas insufflation (TGI). Continuous insufflation of oxygen is a technique used to enhance CO2 removal in the presence of apnea. ⋯ However, other techniques, such as TGI, are used as an adjunct to positive pressure ventilation. Intratracheal pulmonary ventilation provides positive pressure ventilation while bypassing the upper airway. Although some of these techniques are promising adjuncts to mechanical ventilation and may help reduce ventilator-associated lung injury, much remains to be learned about their role in the care of patients with acute lung injury.
-
Numerous reports of patient, lung model, and animal use of tracheal gas insufflation (TGI) have appeared in the literature over the past 10 years. However, no commercial TGI system is available. As a result, extreme care must be exercised if attempts are made to provide TGI. ⋯ However, this requires that the TGI system be integrated with the mechanical ventilator. In addition, appropriate system monitoring should be available, including measurement of total positive end-expiratory pressure, peak inspiratory pressure, and tidal volume, and there should be a method of identifying increased carinal pressure and deactivating the TGI system if an obstruction occurs proximal to the point of TGI injection. As a result of the potential complications of TGI, this technique cannot be recommended for routine use until commercial systems are available.
-
As an adjunct to mechanical ventilation, tracheal gas insufflation (TGI) injects gas flow into the trachea to flush carbon dioxide (CO2) from the anatomical and mechanical dead space, but the addition of TGI flow from a catheter may cause problems related to increased flow velocity at the catheter tip. Forward momentum and turbulence beyond the tip oppose expiratory flow and may cause or increase intrinsic positive end-expiratory pressure. If the catheter is placed within the endotracheal tube (ETT), the catheter itself acts as a resistive element to exhalation. ⋯ A recently developed bidirectional catheter allows the option of delivering TGI flow cephalad, towards the lungs or in both directions. Unfortunately, to be convenient, the use of specially designed catheters or ETTs requires the anticipation of TGI use. A complete system for the safe and convenient use of TGI in ventilated patients is not as yet available, but concerns about the safety and convenience of TGI delivery have been addressed with recent advances in catheter/tube design.
-
Tracheal gas insufflation (TGI) is an adjunct to mechanical ventilation that allows ventilation with small tidal volumes while carbon dioxide (CO2) is satisfactorily cleared. Pioneering studies in healthy animals and in humans suffering respiratory failure showed that the expiratory flushing of proximal dead space decreased minute ventilation with no change in arterial partial pressure of carbon dioxide (PaCO2). ⋯ Clinical use of TGI requires careful monitoring of delivered volumes and pressures to ensure safe clinical application and to evaluate the effect on lung function. Finally, routine use of TGI in intensive care warrants further investigation to solve some technical problems and randomized clinical trials to confirm the beneficial effects in the absence of complications.
-
Traditional ventilator management of acute respiratory distress syndrome (ARDS), emphasizing normalization of blood gases, promoted high rates of conventional barotrauma. Research revealed a broader range of ventilator-induced lung injury, physiologically and histopathologically indistinguishable from ARDS itself. It is now known that overdistention and cyclic inflation of injured lung can exacerbate lung injury and probably promote systemic inflammation, effects minimized by low tidal volumes/plateau pressures and by application of positive end-expiratory pressure. ⋯ There may thus be disparate goals in ARDS management: rapid institution of a restrictive ventilatory strategy, and avoidance of significant acidosis. We review data pertaining to ARDS physiology, ventilator-induced lung injury, lung-protective ventilatory strategies, and the physiology of respiratory acidosis. Tracheal gas insufflation is considered as a means to reconcile the clinical goals of ventilatory reduction and control of acidosis.