Physiologic effects of transtracheal open ventilation in postextubation patients with high upper airway resistance.

OBJECTIVE

To investigate whether transtracheal open ventilation (TOV), pressure control ventilation (PCV) through a minitracheotomy tube (internal diameter 4 mm), is an effective method of inspiratory assistance under high upper airway resistance in postextubation patients; to compare, in a lung model study, TOV with other methods.

DESIGN

Clinical study: A prospective, controlled, crossover study. Lung model study: A prospective laboratory trial.

SETTING

Clinical study: A six-bed general intensive care unit in a teaching hospital. Lung model study: Animal research laboratory.

PATIENTS

Clinical study: Eleven postextubation patients, who had undergone minitracheotomy for sputum retention between January 1997 and December 1997.

SUBJECT

Lung model study: Two-bellows-in-a-box lung model, which included ordinary and high levels of upper airway resistance.

INTERVENTIONS

Clinical study: Ventilatory settings were: assist/control (A/C) mode, 2 breaths/min of A/C back-up rate, 35-40 cm H2O of PCV, 0.6-0.8 secs of inspiratory time, and 0 cm H2O of positive end-expiratory pressure. The ventilatory parameters of TOV were compared with those of spontaneous breathing (SB). Lung model study: Effect of TOV on inspiratory assistance was compared with those of SB, open minitracheotomy, 5 L/min of transtracheal gas insufflation, and 5 and 10 cm H2O of pressure support ventilation (PSV), which simulated noninvasive positive ventilation. TOV ventilatory settings were: A/C mode; 30, 40, and 50 cm H2O of PCV, 0.9 secs of inspiratory time, and 0 cm H2O of positive end-expiratory pressure. At each ventilatory setting, we adjusted the inspiratory effort of the model to give a tidal volume of 0.5 L.

MEASUREMENTS AND MAIN RESULTS

Clinical study: TOV was performed for 76.6 +/- 38.6 hrs (mean +/- sd) over 5.6 +/- 2.6 days without major complication. Peak tracheal pressure, which was measured distal to the minitracheotomy tube in six patients by a catheter pressure transducer, was 4.33 +/- 0.59 cm H2O. Inspiratory tidal volume delivered by the ventilator was 0.51 +/- 0.06 L. Respiratory rate during TOV was lower than during SB. According to esophageal pressure and respiratory inductive plethysmography, TOV reduced the patient's inspiratory work and improved the breathing pattern. Lung model study: Mean tracheal pressure during TOV and 10 cm H2O of PSV were positive values and they had larger inspiratory assistance according to the pressure-time product of pleural pressure. Although high upper airway resistance reduced the inspiratory assistance of PSV, it did not change the effects of TOV.

CONCLUSIONS

TOV effectively reduced patient's inspiratory work and was more useful than open minitracheotomy and transtracheal gas insufflation. TOV also improved the breathing pattern. TOV may be useful for resolving some postextubation respiratory problems and avoiding the need for reintubation.