How Does a Ventilator Work?
Both the patient and caregiver should know about how the home care ventilator works.
The mechanical ventilator assists the patient’s breathing, depending on the needs of the patient. For patients who need the greatest amount of assistance, the ventilator fully controls the volume and duration of breath throughout the respiration cycle.
Terms to understand:
Mechanical ventilation helps a patient breathe or takes over breathing function completely, and is set to produce the right volume of gas/air and adhere to the appropriate rate of breathing
Standard positive pressure ventilators deliver gas/air to the patient through a noninvasive (via a mask or nasal prongs) or invasive means (via tube insertion into the throat)
This ensures that the ventilator delivers the correct respiratory pattern
This provides visual tracking of the volume of the patient’s breath and indicates that the patient is properly connected to the ventilator
Designed to adapt the breathing patterns of patients who require a normal range of ventilation. They can completely support the patient, allow all spontaneous breaths, or a combination of both
Invasive ventilation therapy entails the use of tracheostomy tubes, which come in cuffed or non-cuffed designs
What is ventilation? How does a mechanical ventilator work?
Mechanical ventilators help with breathing.
In breathing, air is inhaled through the mouth and/or nose, pharynx, larynx, trachea and bronchial tree into tiny alveoli sacs in the lungs, where air mixes with the carbon dioxide-rich gas from the blood. The air is then exhaled.
Normally this cycle repeats at a breathing rate, or frequency, for adults of about 12 breaths per minute. Babies and children breathe at a faster rate.
Gas exchange in the lungs supplies oxygen to the blood and removes carbon dioxide collected from the cells.
Ventilation is the “tidal” volume of gas entering or leaving the lungs in a given amount of time, and determines if the gas exchange is sufficient.
For mechanical ventilator to work, it must produce the right tidal volume and breathing rate for the body.
Conventional ventilators produce the normal breathing patterns of children and adults, about 12-25 breaths per minute.
Two forces expand the lungs and chest wall during breathing: the contraction of the muscles (including the diaphragm) and the contrasting pressure at the airway opening (mouth and nose) and on the outer surface of the chest wall.
Normally, the respiratory muscles expand the chest wall. This decreases the pressure on the outside of the lungs, so they expand. This enlarges the air space in the lungs and draws air into the lungs.
When respiratory muscles are unable to do the work for breathing, either one or both of these forces can be manipulated with a mechanical ventilator.
A positive pressure ventilator delivers gas to the patient through a set of flexible tubes, called a patient circuit. Depending on the ventilator design, this circuit can have one or two main tubes.
The circuit connects the ventilator to an endotracheal tube, tracheostomy tube for invasive ventilation or a noninvasive mask/prong.
For invasive ventilation, an endotracheal tube is inserted through the patient’s mouth or nose, or a tracheostomy tube is inserted through an opening made by incision in the neck.
In noninvasive ventilation, the patient circuit connects to a mask covering the mouth and/or nose or nasal prongs.
The tube used for invasive ventilation may have a balloon cuff to provide a seal. The noninvasive mask has a seal around the mouth and nose to prevent the loss of gas/air, ensuring the patient receives appropriate ventilation.
Mechanical ventilation may be used at night, during limited daytime hours, or around the clock, depending on the patient's needs.
Some patients require mechanical ventilation for a short period, such as during recovery from traumatic injury. Others require ventilation long-term, and over time the needs could increase or decrease, depending on the patient’s medical status.
Ventilator control system
A control system ensures that the ventilator produces the correct breathing pattern.
This requires setting basic controls, including:
- Size of the breath
- How fast and often the breath is brought in and let out
- How much effort, if any, the patient needs to exert to start a breath
A spontaneous breath occurs when the patient can control the timing and size of the breath. Otherwise, the effort involves a mandatory breath. A particular pattern of spontaneous and mandatory breaths is referred to as a ventilation mode.
Numerous ventilation modes allow ventilators to produce various breathing patterns, to suit the individual needs of the patient. These modes coordinate with ventilator functions.
Most positive pressure ventilators have an airway pressure monitor to assess the pressure in the circuit. They have a volume measure to assess the volume of the patient’s breaths. These also monitor if the patient is properly connected to the ventilator.
Many positive pressure ventilators have sophisticated pressure, volume and flow sensors. These sensors control the ventilator's output and monitor the interaction between the patient and the ventilator. These monitors allow the caregiver to follow the patient's condition.
These ventilators follow normal breathing patterns and requirements. They can completely support the patient, allow all spontaneous breaths or a combination of both. This ventilator is suited for patients from infants to adults, and for use in the ICU, patient transport, home care and the operating room.
Ventilators and tracheostomy tubes
Invasive ventilation therapy uses a cuffed or cuffless tracheostomy tube. A cuffed tube includes an inflatable cuff that holds the tube in place to help prevent air leaks. Trachesotomy tubes are made of PVC plastic or silicone, as well as metal, such as silver or stainless steel.
Cuffed and cuffless tracheostomy tubes are available with or without inner tubes (cannulas) to draw off fluid or supply medication. Inner cannulas can be reusable or disposable, and can be removed for cleaning. Cannulas can be cleared of secretions while the artificial airway is in place.