As the coronavirus that causes COVID-19 spreads across the United States, concerns are rising that hospital intensive care units could face a shortage of ventilation machines — also known as ventilators — that help the most seriously ill patients breathe.

Health officials say that like many respiratory viruses, coronavirus can cause inflammation in the lungs meaning that the membranes that transfer oxygen from the air into the blood can become blocked. Basic operation of a bedside ventilator used to treat patients with respiratory illnesses such as COVID-19. Patients then often require a bedside ventilator to help them breathe. The machines supply higher levels of oxygen and also help push air into the lungs to open them up.

Life-critical system

In more technical terms, medical ventilators are mechanical apparatuses that forcibly respire a patient whose lung function is compromised.

These machines are considered a "life-critical system" because patients rely on the device to complete the biological exchange of oxygen and carbon dioxide, which would otherwise result in organ tissue damage and death.

An average-sized hospital with 150 beds might have 20 ventilators. One study suggested that there might be roughly 63,000 full-feature ventilators owned by U.S.-based acute care hospitals.

In Britain, officials are asking manufacturers including Ford, Honda and Rolls Royce to help make health equipment including ventilators. Germany and Italy also are reported to be working to acquire more ventilators as manufacturers warned in mid-March that hospitals everywhere likely faced a lack of equipment needed to treat coronavirus patients.

Ventilator basics

Medical ventilators are designed to respire a patient's lungs via a breathing tube. This tube is supplied with ambient air or an air/oxygen mixture through a compressor or turbine. When the lungs reach capacity, the natural elasticity of the tissue forces the air out through an exhaust known as a patient manifold.

A series of interfaces and displays allow parameters such as pressure, volume, flow, air leakage, operating efficiency, backup systems and gas supply to be measured by healthcare professionals, such as respiratory therapists.

Several fail-safes are built into medical ventilators so power or suspension outages do not affect ventilator performance.

Types

Ventilator types are broken into two primary categories: noninvasive ventilators and invasive ventilators.

Noninvasive ventilators provide breathing support through an external interface, such as a mask or nasal prongs. These are positive airway pressure ventilators that use positive pressure to force gas or air into a patient’s lungs. Breathing can be triggered by either the patient or the machine. There are six types of positive pressure ventilators. (Click here to learn more about these ventilators.)

Invasive ventilators deliver air through an endotracheal tube inserted into the patient’s nose or mouth, or through a tracheostomy, a surgical incision in the neck to access the trachea. Air is delivered on a timed cycle through the tube and ensures that the patient takes a minimum number of breaths per minute. These ventilators can be adjusted to respond to the patient’s own efforts to breathe or to override these efforts.

(Click here to learn more about potential concerns with invasive ventilators.)

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