Types of Ventilators and Settings
Once an airway is established with either an ETT or tracheostomy tube, the patient can be managed on mechanical ventilation. The mechanical ventilator is used to improve gas exchange and to assist or provide effective breathing for the patient. In most cases, the patient has either an acute or chronic disease that is causing the ineffective breathing and impaired gas exchange, so the goal is to use mechanical ventilation until the lungs improve and can provide effective breathing and better gas exchange on their own. In some patients with significant damage or progressive disease, weaning off of the mechanical ventilator may not be possible (Ignatavicius et al., 2018).
There are many types of ventilators available for patients; the provider will choose one based on the individual patient’s needs, how long the ventilator will be needed, and how severe the condition is. Most of the ventilators being used today are positive-pressure ventilators: upon inhalation, the ventilator forces air into the patient’s lungs to expand the chest. There are three types of positive-pressure ventilators: pressure-cycled, time-cycled, or volume cycled (Ignatavicius et al., 2018).
A pressure-cycled ventilator has a preset airway pressure. The ventilator will conduct air into the lungs until that preset pressure is obtained. These ventilators are indicated for short-term use, such as in a postoperative patient, or when respiratory therapy needs to conduct some intervention. A more recent variation of the pressure-cycled ventilator is the bi-level positive airway pressure (Bi-PAP) that provides a preset inspiratory pressure but also integrates expiratory pressure as well. A time-cycled ventilator works in the same manner, but instead of a preset pressure, it is based on a preset time for forcing air into the lungs. A volume-cycled ventilator is preset to force air into the lungs until a preset volume is achieved. In the first two types of ventilators, the tidal volume varies, but in this type of ventilator, the tidal volume is preset. There are also microprocessor ventilators that are controlled by a built-in computer that allows for more flexibility with settings. This type of ventilator is indicated for a patient that has severe lung disease, or is ready to attempt the weaning process, but a long weaning process is anticipated (Ignatavicius et al., 2018; Wilkinson et al., 2016).
When working with ventilators, there are a variety of modes that the nurse will need to be familiar with. The most common modes include assist-control, synchronized intermittent mandatory ventilation (SIMV), and Bi-PAP. In assist control, both the tidal volume and the rate are preset for the patient. This mode allows the patient to take breaths on their own, but if the patient does not take a breath independently, the ventilator will trigger and provide a breath. Additionally, if the patient makes an effort to inhale, the ventilator provides assistance to the preset tidal volume. It is important to monitor the patient’s respiratory rate and effort when on assist control; if the patient increases their rate on their own, and the ventilator is also delivering breaths, the patient can develop respiratory alkalosis related to hyperventilation. The nurse would want to assess why the patient is increasing their rate, which could be related to fever, pain, and other etiologies (Ignatavicius et al., 2018; Wilkinson et al., 2016).
SIMV is a mode that can be used for patients who are dependent on the ventilator, or who are trying to wean from the ventilator. Similar to assist-control above, the tidal volume and rate are preset in SIMV. This mode will allow the patient to take breaths on their own but does not assist with completing a patient-triggered breath. If the patient does not initiate their own breath, the ventilator will establish a pattern, or the ventilator can be adjusted for the weaning process. This allows for coordination of ventilator breaths and patient breaths (Ignatavicius et al., 2018).
Bi-PAP is noninvasive and done externally. Instead of the patient needing an ETT or tracheostomy tube, the patient is supported with a face mask or a smaller mask for the nose. The most common reason this mode is a patient with sleep apnea or who is exhibiting signs of potential respiratory failure. It allows for temporary noninvasive treatment while the patient recovers, sleeps, or awaits transition to an invasive type of ventilation (Ignatavicius et al., 2018).
Nursing, in collaboration with respiratory therapy and the provider, will monitor the ventilator settings. There are many different components that need to be monitored, and the nurse should understand what the settings indicate. Most patients today needing mechanical ventilation will likely be maintained on a volume-cycled ventilator with universal controls and settings. The nurse will monitor each of the following settings: tidal volume, respiratory rate, fraction of inspired air (FiO2), peak airway inspiratory pressure, continuous positive airway pressure, positive end-expiratory pressure (PEEP), flow rate, and others as determined by respiratory therapy and the exact type of ventilator being utilized (Ignatavicius et al., 2018; Wilkinson et al., 2016).
- The tidal volume can be measured on either inhalation or exhalation and is the total volume of air with each breath. This volume should be in the range of 6-8 ml per kilogram of body weight.
- The rate is the number of breaths that have been set for the ventilator to deliver per minute, with an average of 10-14 breaths per minute.
- The FiO2 is the amount of oxygen the patient is receiving via the ventilator. This is typically based on the patient’s overall condition and their arterial blood gases. The oxygen must be warmed, and humidity must be added to preserve the mucosal lining of the respiratory tract.
- The peak airway inspiratory pressure (PIP) is the amount of pressure that is required to deliver the tidal volume. The PIP is impacted by the compliance of the lung tissue and is therefore subject to change as the patient’s condition improves or declines. It is essential for nurses to watch this level as it indicates resistance in the airway or ventilator. The patient’s tubing may be occluded, and if the pressure gets too high, the high-pressure alarm will sound on the ventilator. A high-pressure alarm must be responded to and corrected quickly.
- The continuous positive airway pressure (CPAP) is a setting that is used for patients that have their own respiratory effort. This setting allows the ventilator to deliver positive airway pressure during the respiratory cycle to attempt to keep the alveoli open and prevent collapse. This is an important tool for the patient who has started the weaning process.
- The PEEP is an essential setting in the prevention of atelectasis and is used to help treat hypoxemia that has not responded to other methods. The PEEP applies pressure (5-15 cm of water) during the exhale cycle to keep the lungs inflated to prevent collapse.
- Flow rate indicates how quickly the breath is being delivered. An average flow rate is approximately 40 L/min (Ignatavicius et al., 2018; Wilkinson et al., 2016).
Any patient on a ventilator will require ventilator checks to maintain critical settings. Each facility will establish the procedure for ventilator checks and how often they should be performed. Initially, the ventilator checks could be as frequently as every 15 minutes to one hour and then every two hours. The ventilator checks may also be assigned to respiratory therapy. The frequency of ventilator checks is set by provider order and facility policy. Ventilator checks involve checking the mode of operation, temperature, humidity, as well as the components listed above. The nurse should remove any condensation from the tubing during the check. When checking the ventilator, the nurse should check the airway for patency and proper position and ask the patient how they are feeling. Oral cares should be done either at every ventilator check or as indicated by facility policy, as this is essential to decrease the risk of ventilator-acquired pneumonia. All staff should be aware of the alarm system on the ventilators and should respond immediately when a ventilator alarm sounds. Alarms on the ventilator should never be turned off and must be in working condition (Ignatavicius et al., 2018; Wilkinson et al., 2016).