A 45 year old man with head injury was admitted in the critical care unit. He was on mechanical ventilation. His consciousness slowly returned to normal and weaning off mechanical ventilation was planned. 

Q. He is currently on Assist Control Ventilation. Which of the following modes of ventilation would help in the weaning process?
  1. Pressure Support Ventilation
  2. Positive End Expiratory Pressure
  3. Intermittent mandatory ventilation
  4. Inverse ratio ventilation

Answer: The answer is (c). Intermittent mandatory ventilation allows a progressive change from mechanical ventilation to spontaneous breathing by decreasing the ventilator rate gradually. The other modes of ventilation mentioned above do not contribute to the weaning process. 

 

 

Q. His mode of ventilation is changed and the weaning process is proceeding successfully. The next step to completely take him off the ventilator would be
  1. T-tube Technique
  2. Extubation
  3. Tracheostomy
  4. Pressure support ventilation

Answer: The answer is (a). T-tube technique intersperses periods of unassisted spontaneous breathing through continuous flow circuit with periods of ventilatory support. Five to 15 minutes 2 to 4 times daily are used initially and progressively later. During the interspersed periods of ventilation continuous positive airway pressure (CPAP) is given.

 

 

Q. On the second day of his weaning the respiratory therapist added pressure support to the interspersed periods of mechanical ventilation. The reason for this is
  1. Respiratory fatigue
  2. Respiratory alkalosis
  3. Hypoxia
  4. Hypercarbia

Answer: The answer is (a). Pressure support is preferred when respiratory muscle fatigue compromises the success of weaning. Pressure support can reduce the patient's work of breathing. Hypoxia and hypercarbia would warrant more drastic measure as they indicate failure of weaning.