Ventilation Management Health Article

Definition

Ventilation management involves providing optimal mechanical ventilation in order to promote the patient's recovery and to reestablish spontaneous breathing.

Purpose

Mechanical ventilation is used when a patient is unable to breathe adequately on their own. The purpose of ventilation management is to "breathe for them" until they are sufficiently recovered to initiate respiration. This process is usually a gradual one, and is referred to as weaning. During the ventilatory weaning process, the modes of mechanical ventilation are gradually changed to allow the patient to initiate more breaths while the ventilator provides less.

Precautions

Ventilatory weaning should not be attempted until the patient's respiratory status is stable and they are arousable and able to follow commands. If the patient is unstable or unarousable, attempting to wean may cause unnecessary physical stress and may delay recovery.

Description

The ventilatory weaning process is accomplished by decreasing the number of breaths supplied by the ventilator, as well as by changing the way in which those breaths are delivered to the patient. The process also depends on the reason why the patient requires mechanical ventilation. For example, post-operative cardiac bypass patients are generally weaned within a few hours after surgery. However, a patient with extensive lung disease may require days or weeks to wean.

There are three primary methods used to wean patients from the ventilator. These include T-piece, synchronized intermittent mandatory ventilation and pressure support ventilation. A short description of each of these is included here. The method chosen depends on the patient's respiratory status and on how long they have been on the ventilator.

T-piece trials consist of alternating intervals of time on the ventilator with intervals of spontaneous breathing. To facilitate spontaneous breathing, the patient is removed from the ventilator and a T-shaped tube is attached to the endotracheal tube or tracheostomy tube. One end of this tubing is attached to an oxygen flowmeter and the other end is open. The amount of oxygen to be used is ordered by the physician. The patient on a T-piece doesn't have the ventilator as back-up if they can't breathe, so they must be monitored closely. If they tire out or their respiratory status becomes unstable, they should be reconnected to the ventilator. The goal of this method of weaning is to gradually increase the amount of time spent off the ventilator.

Synchronized intermittent mandatory ventilation (SIMV) is a ventilator mode that delivers a preset number of breaths to the patient but coordinates them with the patient's spontaneous breaths. Thus, the ventilator may be set to deliver 12 breaths per minute but the patient's respiratory rate may be 16 (12 ventilator-initiated breaths plus four patient-initiated breaths.) The goal of SIMV weaning is to gradually decrease the number of breaths delivered by the ventilator, which allows the patient to take more breaths of their own. The ventilator rate is usually decreased by one to three breaths at a time and an arterial blood gas (ABG) is obtained 30 minutes after the change to assess the patient's respiratory status. The benefits of SIMV weaning are that the patient has the ventilator for back-up if they fail to take a breath and the ventilator alarms will sound if they are not tolerating weaning. However, the patient should still be closely monitored for signs of respiratory fatigue.

Pressure support ventilation (PSV) augments the patient's spontaneous inspiration with a positive pressure "boost." This decreases the resistance created from breathing through ventilator tubing and is used with the SIMV mode to decrease the work of breathing.

If the patient tolerates SIMV weaning, the ventilator mode may be changed to constant positive airway pressure (CPAP) as a final trial of spontaneous breathing prior to removing the endotracheal tube. In this mode, patients will breathe on their own but have the benefit of the ventilator alarms if they have difficulty. CPAP maintains constant positive pressure in the airways, which facilitates gas exchange in the alveoli. PSV is often used with the CPAP mode to further decrease the work of breathing. If the patient tolerates CPAP, the endotracheal tube is removed and a face mask with humidified oxygen is applied for a short time. If the patient remains stable, a nasal cannula may be used to deliver oxygen.

If the patient has a tracheostomy, the weaning process is the same as with a endotracheal tube, with the exception that after the ventilator is disconnected, a tracheostomy collar may be used to deliver humidified oxygen instead of a face mask or nasal cannula. This is simply a mask-like device that fits loosely over the tracheostomy and is held in place by an elastic band around the neck.