This patient has had a successful spontaneous breathing trial (SBT) and is ready for discontinuation of mechanical ventilation and extubation. The purpose of a SBT is to assess the likelihood that mechanical ventilation can be discontinued successfully. A SBT is performed by placing the patient on a T-piece through which no positive pressure is delivered (only supplemental oxygen) or by adjusting the ventilator so that it applies only enough pressure to overcome the resistance of the endotracheal tube. Criteria that have been suggested for a successful SBT include the ability to tolerate a weaning trial for 30 minutes; maintain a respiration rate of less than 35/min; and maintain an oxygen saturation of at least 90% without arrhythmias, sudden increases in heart rate and blood pressure, or development of respiratory distress, diaphoresis, or anxiety. Because this patient successfully completed a SBT, an attempt at discontinuation of mechanical ventilation and extubation is appropriate.
Arterial blood gas studies are performed when there are concerns about acute or worsening chronic carbon dioxide retention or when exact arterial oxygenation measurement is needed. Even if the carbon dioxide level is elevated, it would not necessarily indicate that the patient is not an appropriate candidate for extubation, especially if the patient is able to perform a SBT and has an otherwise unremarkable examination, as in this patient.
It is unnecessary to continue mechanical ventilation and observe for an additional 24 hours with an endotracheal tube in place. Patients who meet the parameters of success during a SBT can be disconnected from mechanical ventilation and extubated. Continuing mechanical ventilation beyond the time when successful weaning parameters are met adds additional risks to the patient, including ventilator-associated infections or other potential complications of mechanical ventilation.
Direct extubation to noninvasive positive pressure ventilation is effective at weaning patients with obstructive lung disease with ventilatory respiratory failure from mechanical ventilation. However, it is not necessary for patients with primarily hypoxemic respiratory failure such as this patient with pneumonia.