General guidelines for selecting individual ventilator settings are initially determined by the attending physician or a respiratory therapist if ventilator protocols are in place. These parameters are determined by a person’s height and weight, level of health and diagnosis. A ventilator is a device that breathes for you when you are unable to breathe on your own. Ventilator alarms are set to notify your health care provider that the parameters that were set have either not been met, or have been exceeded.
Setting the respiratory rate is determined in combination with the tidal volume in order to provide adequate oxygenation and ventilation to the patient’s lungs. An adult’s normal respiratory rate is 12 to 15 breaths per minute, while a child’s normal respiratory rate is 15 to 22 breaths per minute. Respiratory rate ventilator alarms are normally set to 10 to 15 above the set rate. An apnea alarm is also set to 20 seconds. Apnea is the absence of breathing, so when a patient has not taken a breath, or if the ventilator has not given a breath after 20 seconds, the alarm will sound.
Another standard ventilator setting is tidal volume. The tidal volume is the amount of air or air oxygen mix that the ventilator delivers to keep the lungs expanded. A normal tidal volume is 5 to 15 cc per kg of body weight. The level of volume is also set according to the patients’ lung compliance, resistance and disease state. Compliance and resistance is the elasticity of the lungs and the lungs' ability to return to the resting state.
Another ventilator setting is the fraction of inspired oxygen, or FI02. The amount of oxygen supplied by the ventilator is dictated by the patient’s condition. Oxygen is a drug with severe side effects if not closely monitored, particularly in premature infants. Efforts should always be made to keep the FI02 below 60 percent to prevent oxygen toxicity.
Positive End-Expiratory Pressure, or PEEP, is produced by closing the expiratory valve prematurely and trapping a specific volume of expired gas within the lungs. This volume is determined by the patient's lung compliance as well as the ventilator’s pressure setting. This is another setting that should be carefully monitored to prevent lung injury.
Mechanical ventilators are equipped with alarms that are set to notify the health care provider of ventilation problems, either with the ventilator or with the patient. The high and low pressure limits are set to alarm when the patient's inspiratory pressure exceeds safe pressure limits, or when too little pressure is given. The low exhaled volume alarm will sound when the patient has not exhaled the air that was given during the inspiratory phase of ventilation.