Why Lying Face-Down Helps Relieve Coronavirus Symptoms
How ‘proning’ Covid-19 patients helps them breathe
Thousands of patients suffering from severe cases of Covid-19 are experiencing a simple treatment in hospitals throughout the world: They are being placed face-down on their hospital bed in a practice known as proning. This change in position is often enough to improve lung functionality and reduce the impact of respiratory distress caused by Covid-19.
The Lungs and Gravity
The lungs are remarkably complex in functionality. As the primary interface for gas exchange in the body, the lungs are a dynamic organ that responds to minute changes in the internal and external environments to maximize oxygen transfer and carbon dioxide removal.
When a person breathes in, air is pulled through the airways into a network of microscopic sacs called alveoli. Waiting on the other side of a thin barrier within millions of capillaries are red blood cells lined up ready to receive the incoming oxygen.
Based on the demand, position, and health of the lungs, this network of blood vessels dilate and constrict to maximize gas transfer — all under the orchestration of hormone and nerve signals. In one breath, the lungs saturate the blood in the pulmonary system with oxygen to be transferred throughout the body to meet metabolic demand.
For all their elegance and delicacy, the lungs are also subject to some crude forces.
The lungs are positioned within the thoracic cage, but are not technically attached to anything other than the airways and blood vessels that supply them. When you inspire (breathe in), muscles that expand the thoracic cavity — the diaphragm and accessory muscles surrounding the ribs — pull the chest wall away from the lungs.
Between the lung tissue itself and the inner wall of the chest is an enclosed space called the pleural cavity. When the chest wall draws away from the lungs, the pressure in the pleural cavity (intrapleural pressure) drops to the point where it is less than the pressure inside the alveoli (intra-alveolar pressure), which forces the lung tissue to expand as if being sucked toward the chest wall. As the lung tissue expands, the alveoli open and draw air into them.
For all their elegance and delicacy, the lungs are also subject to some crude forces. As an organ, the lungs are relatively heavy, weighed down mostly by the blood that circulates through them. In an upright person, gravity pulls the lungs downward, pressing the tissue against the diaphragm.
Blood within the pulmonary circulation also responds to the force of gravity, pooling in the lower vessels of the lung tissue. As a result, certain areas of the lungs are better perfused — meaning they have more adequate blood supply. Similarly, the fine alveoli that contain air are under greater compression forces in the lower lungs than the upper.
The same effects of gravity are in play when the body is lying down. If a person lays supine (face up), then blood will tend to pool toward the back of the thoracic cavity. Blood will similarly pool toward the front of the thoracic cavity when a person is lying face down (prone), though not quite to the same extent. In this position, another factor imparts unequal pressure on the lungs — the heart.
Resting slightly off-center in the middle of the thoracic cavity, the heart is a dense, blood-drenched muscle roughly the size of your fist. The heart is almost entirely surrounded by the lungs with the exception of the anterior-most area, and depending on the position, the heart may or may not rest itself on the lungs, further compressing the underlying tissue. This is particularly true in the supine position, where gravity pulls the heart toward the back of the chest wall where it weighs down lung tissue.
Acute Respiratory Distress Syndrome (ARDS)
ARDS is defined as any condition in which breathing and/or respiration is acutely limited or at risk. In severe Covid-19 cases, the vigorous immune response that follows a coronavirus infection causes swelling and damage to the lung tissue. Accumulating fluid and swollen tissue between air and blood make breathing a major task, which often requires that severely ill patients be placed on mechanically-assisted ventilation.
Ventilators come with their own set of risks for ill patients, ranging from secondary infection to further damage of lung tissue. Placing patients on ventilators is necessary to maintain oxygenation, but is considered a last-choice effort. ARDS is one of the most ominous outcomes of Covid-19 infection, and placing patients on mechanical ventilation signals a patient is at significant risk. As a result, some doctors are turning to proning patients to improve lung function and potentially keep them off ventilators.
Proning
Proning — or placing a patient face-down — minimizes the effects of gravity on the lungs. In the supine position (the position most hospital patients assume), lung tissue toward the back of the lungs becomes compressed under the weight of the lungs, blood, and the nearby heart.
For patients who spend weeks in this position, these regions can suffer chronically reduced lung capacity, thus exacerbating an already distressed respiratory system. Placing patients in the prone position relieves the effects of gravity and opens up new regions of lung tissue for air and gas exchange.
Proning — or placing a patient face down — minimizes the effects of gravity on the lungs.
In this position, the heart no longer weighs heavily on the lung tissue, but instead rests against the sternum. Lung tissue at the back of the thoracic cavity is relieved of the burden of gravity and is more capable of expansion and gas exchange. Some patients with ARDS have seen marked improvements in oxygen saturations from proning alone.
Granted, patients cannot spend all day in this position. Proning limits the ability of hospital staff to communicate with patients, perform physical exams, and administer medications. Likewise, it is simply not comfortable for patients to lay face-down all the time. So, hospitals practice proning in shifts, placing patients face-down for a period and returning them to the face-up position for the remainder of the day. Some guidelines suggest rotating patients through various positions to improve lung function.
ARDS is the most dangerous outcome of coronavirus infections, accounting for a large percentage of deaths. While the hunt for more effective treatments, hospital care, and vaccines continues, the simple practice of proning patients seems to offer improvements in lung functionality and better outcomes. This simple practice is useful in almost all Covid-19 patients, though some contraindications do exist. The practice relies simply on the anatomy of the human lungs (coupled with gravity) to optimize breathing during a coronavirus infection.
