Nabil El-Baz

One-Lung High-Frequency Ventilation for Tracheoplasty and Bronchoplasty: A New Technique

Major airway surgery requires the maintenance of adequate ventilation and oxygenation during the period of resection and reconstruction, as well as an unobstructed surgical field and optimal access to the airways circumference. High-frequency positive-pressure ventilation (HFPPV) at a frequency of 1 Hz (60 breaths/min) or more, along with a small tidal volume (50 to 250 cc), provides adequate ventilation and oxygenation with minimal impairment of pulmonic and systemic circulatory functions. We have used HFPPV of one lung through a 2 mm internal diameter catheter in six patients (three undergoing right sleeve pneumonectomies, two having carinal tumor resections, and one having tracheal resection). High-frequency positive-pressure ventilation of the left lung provided continuous and adequate ventilation and oxygenation during the period of resection and reconstruction of the airways, while the small catheter permitted unimpaired visualization and adequate access to the operative site.

One-Lung High-Frequency Positive Pressure Ventilation for Sleeve Pneumonectomy: An Alternative Technique

High-frequency positive pressure ventilation (HFPPV) was originally used in experimental animal studies in 1971 by Jonzon et a1 (I),. and the technique was introduced into clinical anesthesia by Heijman et a1 (2) the following year. HFPPV incorporates the use of a small tidal volume approaching the volume of dead space at a frequency of 1 Hz or more. HFPPV provides adequate ventilation and oxygenation mainly by the generation of eddy flow in the airways, leading to an improvement in the intrapulmonary gas mixture and distribution as well as facilitating gas diffusion. The airway pressure during HFPPV is continuously positive, with low mean and peak pressures, whereas the intrapleural pressure is continuously subatmospheric with minimal effect on the pulmonary and systemic circulation (3).

High-frequency positive-pressure ventilation for tracheal reconstruction supported by tracheal T-tube.

High-frequency positive-pressure ventilation (HFPPV) was first described by Oberg and Sjostrand (I), who demonstrated in animals that ventilation and oxygenation could be adequately maintained with much lower tidal volumes and higher respiratory rates than conventionally used. This method of ventilation was studied in humans by Jonzon et a1 (2) and was first reported during clinical anesthesia and surgery by Heijman et a1 in 1972 (3). HFPPV is one of two types of high-frequency ventilation; the other is high-frequency oscillation. They differ in the tidal volumes and respiratory rates used. In HFPPV, tidal volumes that approach the anatomic dead space (50 to 250 ml) are delivered at rates of 1 to 10 Hz (60 to 600 breaths/min); alveolar ventilation with this technique is thought to be accomplished by a combination of convection and improved gas diffusion. In high-frequency oscillation, lower tidal volumes (5 to 50 ml) are delivered at rates of 10 to 100 Hz (600 to 6000 breaths/min); alveolar ventilation during high-frequency oscillation is thought to be accomplished by acceleration of gas diffusion and collateral intra-alveolar ventilation (4-7). The high velocity of the small tidal volumes deliv-

Intratracheal insufflation combined with intermittent positive pressure ventilation for treatment of terminal respiratory failure in a child: a new technique.

I NTERMITTENT positive-pressure ventilation (IPPV) mimics spontaneous breathing in providing a large tidal volume at a slow respiratory rate.’ This method of convection flow ventilation has been a valuable technique for respiratory support during anesthesia and for treatment of respiratory failure. The addition of positive end-expiratory pressure (PEEP) to IPPV has been shown to improve gas exchange in patients with moderate and severe respiratory failure, despite alterations of cardiovascular and renal function.2-4 In 1971, Jonzon et al demonstrated that the use of a small tidal volume at a high respiratory rate can provide adequate gas exchange by a combination of convective flow and facilitation of gas diffusion.’ This technique of high-frequency ventilation (HFV) was also shown to improve gas exchange in patients with respiratory failure and has been valuable in patients with a bronchopleural fistula.637 Therapy with IPPV-PEEP and HFV in a child with severe respiratory failure was associated with complications, and death was imminent as a result of progressive hypoxemia. Therefore, a new technique for respiratory support was developed. A combination of continuous intratracheal insufflation (TI) and IPPV was used to provide convective-diffusion ventilation. This clinical report shows the gas exchange achieved with the use of TI-IPPV for a period of 14 days in a child with severe respiratory failure.

High-Frequency Ventilation with an Uncuffed Endobronchial Tube. A New Technique for One-Lung Anesthesia

Conventional one-lung intermittent positive-pressure ventilation (OL-IPPV) has been a valuable technique during anesthesia for intrathoracic operations. OL-IPPV has been associated with a high incidence of hypoxemia, as a result of the associated intrapulmonary shunt of 21% to 65% of cardiac output. The administration of OL-IPPV requires the use of a large cuffed endobronchial double-lumen tube. These tubes can be difficult to position properly and have been associated with malfunction, trauma, and tracheobronchial rupture. In an effort to avoid the problems associated with conventional OL-IPPV, we have developed a new technique of modified one-lung high-frequency ventilation (MOL-HFV). MOL-HFV is based on the administration of high-frequency ventilation (HFV) through a small uncuffed endobronchial tube. MOL-HFV was studied in 26 patients during a variety of intrathoracic surgical procedures, and it was compared to one-lung high-frequency ventilation (OL-HFV) and OL-IPPV in each patient. After the chest was opened, each patient received a sequence of OL-IPPV, OL-HFV, and MOL-HFV. Arterial PO2 was measured and intrapulmonary shunting was calculated after 30 minutes of each type of ventilation. This study showed that arterial PO2 was significantly higher during MOL-HFV (mean 379 mm Hg) than during OL-HFV (mean 235 mm HG) or OL-IPPV (mean 141 mm Hg). This was the result of a significantly lower intrapulmonary shunt during MOL-HFV (19%). We conclude that MOL-HFV through a small uncuffed endobronchial tube provides better oxygenation, optimal surgical access, and avoids the problems associated with the use of double-lumen tubes.