How to Change From SIMV to CPAP Mode

As opposed to CPAP used at home to treat sleep apnea, CPAP and SIMV modes are used in mechanical ventilators as an aid in weaning a patient from the ventilator. The narrow diameter of an endotracheal tube increases air resistance; both SIMV and CPAP, especially used in conjunction with pressure support ventilation, decrease the patient’s work of breathing. In many states, only respiratory therapists (RTs) are certified to perform such procedures; in areas where RTs are few in number, nurses and doctors may perform ventilator maintenance and changes in parameters. Only licensed professionals should make any adjustments to a ventilator.

Things You'll Need

• Ventilator with patient tubing
• Pulse oximeter
• EKG

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Instructions

Changing from SIMV to CPAP mode

• 1

  Assess the patient to determine if she can tolerate weaning. The patient should ideally be awake and alert, though that is not a requirement especially if long-term coma is present and the respiratory status is stable.

• 2

  If one is not already in use, attach the patient to a pulse oximeter and electrocardiogram (EKG) to help assess how well she will tolerate weaning. Ventilator alarms will monitor the patient’s respiratory rate and volume. Adjust these to appropriate settings.

• 3

  Many newer ventilators have separate buttons to distinguish between SIMV and CPAP modes. Press the CPAP button followed by “Enter.” If the ventilator does not automatically set a CPAP pressure, dial in the pressure ordered by the physician in charge, as well as pressure-support ventilation (PSV) if ordered and available on the ventilator.

• 4

  Several older models of ventilator share both functions in one setting. In SIMV mode, the ventilator will deliver a preset volume of air at a preset rate and the patient can draw spontaneous breaths between those delivered by the ventilator. To change to CPAP mode, simply dial the respiratory rate to zero and adjust the CPAP pressure as ordered by the attending physician.

• 5

  Pressure support ventilation (PSV) is usually used in conjunction with both SIMV and CPAP modes while weaning from a newer ventilator; PSV is not available in older ventilators, increasing the patient’s work of breathing (WOB) during weaning. Monitor the patient’s heart rate (HR), oximeter readings (SpO2), respiratory rate (RR) and WOB closely. If the HR, RR and/or WOB increase incrementally—even if the SpO2 remains consistent—the patient may be tiring. Inform the physician immediately. If the patient is in distress, discontinue CPAP and revert to SIMV mode.