By Paul A. Byrne, M.D. (used with permission)
May 11, 2020
Ventilators are in the public eye with the COVID-19 pandemic. Basic information about breathing is needed to understand what the ventilator can and cannot do to protect and preserve life.
The official name for the virus causing the pandemic is Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and for the disease is COVID-19. Naming the coronavirus disease (COVID-19) and the virus that causes it (Accessed 5-1-20)
How We Breathe
Breathing is to inhale and exhale. To inhale is movement of air with oxygen into the lungs. To exhale is movement of air with carbon dioxide, a waste product, out.
Normally, the stimulus to breathe begins in the brain, which sends nerve impulses that cause the muscles of the diaphragm and chest wall to contract. This change in the chest results in negative pressure between the atmosphere and the inside of the lungs, which allows air to flow into the lungs to expand them. In contrast, modern ventilators use positive pressure and flow to expand the lungs.
Elastic recoil of the chest and lung tissues moves air out of the lungs, i.e. exhalation. For exhalation, the chest and lungs must first expand to store energy for this elastic recoil to move air out of the lungs. This expansion of the chest is necessary in normal breathing and in a patient on a ventilator. To emphasize: The ventilator moves air into the lungs, butbut the ventilator itself does not move air out of the lungs. Stored energy from expansion of the chest the ventilator itself does not move air out of the lungs. Stored energy from expansion of the chest is is needed for exhalation to occur.
Oxygen in the air goes into the lungs with normal breathing or with help of a machine. In the lungs the oxygen goes into the blood. The blood has special components (hemoglobin) that carry and unload oxygen to the tissues.
Circulation is necessary to transport oxygen in the blood to the tissues. Carbon dioxide is a waste product that is produced in the tissues and goes into the blood for transport to the lungs to go out of the body. The actual gas exchange (oxygen in; carbon dioxide out) is termed “respiration.”
Ventilators Do Not Do Respiration – Gas Exchange
Ventilators can move air to help expand the lungs. They can provide more oxygen than is in the air, if needed. In these ways they support the functioning of other organs. VenVentilators cannot and do not do “respiration” i.e., gas exchange in the lungs or in tissues throughout the body, nor do they make the heart beat or circulate blood.tilators cannot and do not do “respiration” i.e., gas exchange in the lungs or in tissues throughout the body, nor do they make the heart beat or circulate blood. There are other machines that can take the place of the lungs and exchange gases in and out of the blood but resrespiration at the level of the tissues is done only in a living personpiration at the level of the tissues is done only in a living person. Sometimes people refer to the ventilator, (or even personal protective equipment), as “respirators.” This is common speech but does not accurately name the function of the ventilator.
A patient with COVID-19 in severe distress is a candidate for ventilatory support. Often they are older, have coexisting conditions (comorbidities) and live in a nursing home. In addition to ventilatory support, treatment for comorbidities and possibly additional medications to counteract the inflammation or coagulation problems associated with COVID-19, may be needed.
Breathing Support–CPAP, BiPAP, Ventilator
The question of additional ventilatory support must be considered. What treatments can be done? Perhaps, give oxygen; use other breathing support devices such as continuous positive airway pressure (CPAP), bilevel positive airway pressure (BiPAP), or a ventilator.
CPAP and BiPAP do not require placement of a breathing tube (endotracheal tube) into the windpipe (trachea). The nasal and tracheal tissues continue to function with the flow of air. CPAP and BiPAP provide pressure that aids in expanding the lungs during inhalation and keeping the lungs from completely deflating during exhalation so the lung air sacs don’t collapse.
More About What a Ventilator Can and Cannot Do
The ventilator provides airflow through a plastic breathing tube (endotracheal tube) to expand the lungs. For the ventilator to be effective, the lungs, heart, circulation, and tissues must be able to function sufficiently to do respiration. The ventilator is most effective in conditions where the patient is unable to take a breath, for example, with head injury, drug overdose, or perhaps under anesthesia.
The ventilator may not fully expand parts of the lungs that are obstructed by fluid or swelling. The ventilator does not directly treat the underlying condition or infectious source, whether bacterial or viral. The ventilator can supply oxygen, but it cannot provide the functioning hemoglobin that carries oxygen in the blood. Oxygen is needed for the heart to pump, but the beating of the heart is intrinsic to the heart, which circulates the blood. The ventilator cannot circulate the blood.
Symptoms may include cough, fever, chills, sore throat, muscle pain, and shortness of breath. Doctors may observe low oxygen in the blood (hypoxemia), large amounts of inflammation, and blood clots.
All information about the patient needs to be gathered; then the doctor makes the judgment as to the treatments most beneficial to the patient.
Ventilatory support is one possible treatment to move air with oxygen into the lungs. Ventilator use requires a breathing tube in the windpipe.
Increased oxygen may be provided without a breathing tube in ways other than the ventilator, such as: oxygen masks, nasal cannula, high flow nasal cannula that provides continuous positive airway pressure, CPAP or BiPAP.
Doctors may provide treatments to decrease inflammation in the body including the lungs. These may include steroids (methylprednisolone), hydroxychloroquine, azithromycin (Z-Pak), vitamin C, vitamin D, zinc, and thiamine. Treatments may be provided to inhibit any increased tendency to form blood clots. A new antiviral medication is Remdesivir. Convalescent plasma with antibodies from patients who have recovered from COVID-19 is being studied.
Continuation of treatments of comorbidities is essential. Doctors must be aware and alert to new treatment strategies, which may include use of older therapies. https://covid19criticalcare.com/treatment-protocol/
This treatise is designed to explain the use of the ventilator, especially to the general public who may wonder why the ventilator is used or not used, and why some patients may do well on a ventilator but others do not. There have been issues raised that COVID-19 patients on ventilators do not respond like other patients with lung infections and may do worse when put on the ventilator. Most patients will recover from COVID-19; however, some may have a prolonged course; some sadly may die.
© Paul A. Byrne, M.D. Used with Permission.
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