Dozens of organizations and hundreds of additive manufacturing companies are racing to help governments and healthcare institutions around the world address the shortage of life-saving respiration aids for intensive care COVID-19 patients who have difficulties breathing autonomously. 3D printing COVID-19 devices can be a viable option in some cases and 3dpbm has reported on many of these. However, in many cases, there is a limited flow of accurate information on the difference between the various types of machinery used according to the severity of each situation.
To address this general lack of clear information, 3dpbm was able to consult with intensive care specialists who provided an overview of the different assisted respiration options available in an intensive care unit for treating different types of respiratory failure. Please note that low-performance materials such as PLA and basic desktop 3D printers do not generally offer sufficient guarantees in terms of durability (as an AM industry media we sometimes take this for granted). You may need to refer to traditional healthcare device manufacturers or healthcare professionals in order to validate the efficiency and confirm the effective need for 3D printed parts.
Respiratory insufficiency and failure is a condition in which blood doesn’t have enough oxygen or has too much carbon dioxide. When you breathe, your lungs take in oxygen. The oxygen passes into your blood, which carries it to your organs. When you exhale the carbon dioxide is expelled. Organs need this oxygen-rich blood to work well, and having too much carbon dioxide in your blood can harm your organs. Several conditions that affect breathing can cause respiratory failure. COVID-19 causes respiratory failure by affecting the lungs directly.
When a patient suffers from respiratory failure there are two main types of treatment approaches, which depend on the gravity of the patient’s condition. They are mainly divided between non-invasive and invasive methods. Because of the particularly delicate nature of invasive ventilation – when patients who are unable to breathe by themselves are sedated and oxygen is pumped directly into their lungs through an intra-oral tracheal tube – most 3D printing-related activities should focus on non-invasive methods. These are also further divided into low-flow and high-flow devices for unassisted or assisted respiration.
Non-invasive respiration devices (NIMV)
Non-invasive methods can be split into three main categories: those that simply provide an increased concentration of oxygen to patients who are able to breathe independently; those that provide a positive pressure to help patients who have severe difficulties in breathing; and those that require assistance for patients who are suffering from acute or chronic respiratory failure.
Nasal cannulas (NC)
The nasal cannula (NC) is a device used to deliver supplemental oxygen or increased airflow to a patient or person in need of respiratory help. This device consists of a lightweight tube that on one end splits into two prongs. These are placed in the nostrils so that a mixture of air and oxygen flows through. The other end of the tube is connected to an oxygen supply such as a portable oxygen generator, or a wall connection in a hospital via a flowmeter. The cannula is generally attached to the patient by way of the tube hooking around the patient’s ears. The earliest and most widely used form of adult nasal cannula carries 1–3 liters of oxygen per minute maximum. These are generally not connected to a ventilator but rather directly to an oxygen tank or hospital oxygen distribution network.
How can 3D printing help? 3D printing may be used to produce custom adapters to a person’s nostrils, However, this product is not expected to experience dramatic shortages since they are open systems which are not recommended with highly infectious patients
Non-rebreather mask (NRB) – Mask with oxygen reservoir
A non-rebreather mask (NRB, non-rebreather, non-rebreather facemask) is a device used in medicine to assist in the delivery of oxygen therapy. An NRB requires that the patient can breathe unassisted but, unlike low-flow nasal cannulae, the NRB allows for the delivery of higher concentrations of oxygen. The non-rebreather mask covers both the nose and mouth of the patient and attaches with the use of an elastic cord around the patient’s head. The NRB has an attached reservoir bag, typically one liter, that connects to an external oxygen tank or bulk oxygen supply system. Before an NRB is placed on the patient, the reservoir bag is inflated to greater than two-thirds full of oxygen, at a rate greater of 10 liters per minute (lpm). Approximately ¹⁄₃ of the air from the reservoir is depleted as the patient inhales, and it is then replaced by the flow from the O2 supply. If the bag becomes completely deflated, the patient will no longer have a source of air to breathe.
How can 3D printing help? 3D printing may be used to produce custom adapters and valves to connect the mask to the reservoir or to the oxygen source..
Ambu – Bag Valve Mask (BVM)
A bag valve mask (BVM), sometimes known by the proprietary name Ambu bag or generically as a manual resuscitator or “self-inflating bag”, is a hand-held device commonly used to provide positive pressure ventilation to patients who are not breathing or not breathing adequately. The device is a required part of resuscitation kits for trained professionals in out-of-hospital settings (such as ambulance crews) and is also frequently used in hospitals as part of standard equipment found on a crash cart, in emergency rooms or other critical care settings. These manual resuscitators are also used within the hospital for temporary ventilation of patients dependent on mechanical ventilators when the mechanical ventilator needs to be examined for possible malfunction or when ventilator-dependent patients are transported within the hospital. Two principal types of manual resuscitators exist: one version is self-filling with air, although additional oxygen (O2) can be added but is not necessary for the device to function. The other principal type of manual resuscitator (flow-inflation) is heavily used in non-emergency applications in the operating room to ventilate patients during anesthesia induction and recovery.
How can 3D printing help? 3D printing may be used to produce custom adapters and valves to connect the Ambu bag to the face mask and/or to a ventilator.
Venturi Mask (Ventimask)
The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. The mask was invented by Moran Campbell at McMaster University Medical School as a replacement for intermittent oxygen treatment. Venturi masks are considered high-flow oxygen therapy devices. This is because venturi masks are able to provide total inspiratory flow at a specified FiO2 (the concentration of oxygen) to patients therapy. The kits usually include multiple jets (venturi valves), which are typically color-coded in order to set the desired FiO2.
Some brands of masks have a rotating attachment that controls the air entrainment window, affecting the concentration of oxygen. This system is often used with air-entrainment nebulizers to provide humidification and oxygen therapy. The mechanism of action is usually incorrectly quoted as depending on the venturi effect. Despite there being no evidence for this, many textbooks and journal articles cite this as the mechanism. However, a fixed performance oxygen delivery system, despite often being called a venturi mask, works on the principle of jet mixing.
How can 3D printing help? 3D printing has been used to produce venturi valves to address supply chain issues in an emergency.
Mask or helmet for positive pressure ventilation (CPAP), BiPAP and Positive end-expiratory pressure (PEEP)
Continuous positive airway pressure (CPAP) is a form of positive airway pressure ventilator, which applies mild air pressure on a continuous basis. It connects to a flowmeter system to create the positive pressure necessary to keep the airways continuously open in people who are able to breathe spontaneously on their own but need help keeping their airway unobstructed. It is an alternative to positive end-expiratory pressure (PEEP). Both modalities use positive pressure to stent the lungs’ alveoli open and thus recruit more of the lungs’ surface area for ventilation. While PEEP refers to devices that impose positive pressure only at the end of the exhalation, CPAP devices apply continuous positive airway pressure throughout the breathing cycle. Thus, the ventilator itself does not cycle during CPAP, no additional pressure above the level of CPAP is provided, and patients must initiate all of their breaths. The snorkeling mask that has been used by Isinnova, through a custom 3D printed adapter is an example of CPAP system.
BiPap is another type of positive pressure ventilation device. While using BiPap you receive higher air pressure when you breathe in than when you breathe out. This setting is different from continuous positive airway pressure (CPAP), which delivers the same amount of pressure as you breathe in and out.
How can 3D printing help? 3D printing may be used to produce custom adapters and valves to connect the CPAP mask or helmet to a ventilator or other oxygen source. Alternatively, 3D printing can be used to reverse engineer and prototype new connectors and valves in a disrupted supply chain. 3D printing could also be used to produce the clips and attachments for the lacing system that holds the mask pressed onto a patient’s face.
Semi-invasive and invasive ventilation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic tube into the trachea (windpipe) to maintain an open airway or to serve as a conduit through which to administer certain drugs. It is frequently performed in critically injured, ill, or anesthetized patients to facilitate ventilation of the lungs, including mechanical ventilation, and to prevent the possibility of asphyxiation or airway obstruction.
Laryngeal Mask Airway (LMA)
A laryngeal mask airway (LMA) — also known as laryngeal mask — is a medical device that keeps a patient’s airway open during anesthesia or unconsciousness. It is composed of an airway tube that connects to an elliptical mask with a cuff that is inserted through the patient’s mouth, down the windpipe. Once deployed, it forms an airtight seal on top the glottis (unlike tracheal tubes which pass through the glottis) allowing a secure airway to be managed by a health care provider.
LMAs are most commonly used to channel oxygen gas to a patient’s lungs in the pre-hospital setting (for instance by paramedics and emergency medical technicians) for unconscious patients.
How can 3D printing help? 3D printing may be used to produce custom adapters and valves to connect the LMA to an oxygen source or an expiration tube. If the need arose, 3D printing could also be used by the standard manufacturer or a distributor experiencing supply chain issues to produce a mold in order to manufacture the silicon mask via an indirect 3D printing process.
A tracheal tube is a catheter that is inserted into the trachea for the primary purpose of establishing and maintaining a patent (open and unobstructed) airway. Tracheal tubes are frequently used for airway management in the settings of general anesthesia, critical care, mechanical ventilation and emergency medicine. Many different types of tracheal tubes are available, each suited for different specific applications. An endotracheal tube is a specific type of tracheal tube that is nearly always inserted through the mouth (orotracheal) or nose (nasotracheal). It is a breathing conduit designed to be placed into the airway of critically injured, ill or anesthetized patients in order to perform mechanical positive pressure ventilation of the lungs and to prevent the possibility of aspiration or airway obstruction. The endotracheal tube has a fitting designed to be connected to a source of pressurized gas such as oxygen. At the other end is an orifice through which such gases are directed into the lungs and may also include a balloon (referred to as a cuff). The tip of the endotracheal tube is positioned above the carina (before the trachea divides to each lung) and sealed within the trachea so that the lungs can be ventilated equally. A tracheostomy tube is another type of tracheal tube.
How can 3D printing help? 3D printing may be used to produce custom adapters and valves to connect the LMA to a regulated oxygen flow source (from ventilator to patient) or an expiration tube (from patient to ventilator).
Intensive care ventilators
Although mechanical ventilators are generally classified as negative and positive pressure ventilators, negative pressure ventilators are rarely used today. The first positive pressure ventilators appeared in the 1940s. However, they began to become widespread after the reduction of mortality in mechanically ventilated patients in the polio epidemics of the 1950s. The developments in engineering enabled the switch from the devices that initially only guaranteed the set tidal volume at a certain respiratory rate to the devices used today, which monitor the patient’s condition and respiratory dynamics and adjust the respiratory parameters to the patient’s needs.
These devices, which were initially only volume-controlled and could not detect the triggered breaths of the patients, did not have a monitor or alarm. In the second-generation devices, the trigger of the patients was possible, and some parameters such as respiratory rate could be monitored. Shortly after, intermittent positive pressure ventilation (IMV) began to be used, and pressure-controlled and pressure-assisted ventilation was used in clinical practice over time. Third generation devices using microprocessors were produced with further technological developments. Flow triggering was introduced in these devices, as well as gas delivery and monitoring, synchronized intermittent mechanical ventilation (SIMV) and pressure assistance. Today’s complex and versatile devices are known as fourth-generation devices, and the most important feature of these devices is that a wide variety of modes have been brought into use by several companies.
More information on these very complex machines is available here.
Companies that make ventilators include GE Healthcare in the US, Medtronic in Ireland, Acutronic and Hamilton Medical in Switzerland, Smiths Group in the UK, Drägerwerk and Siemens in Germany, Philips in the Netherlands, Getinge in Sweden, Air Liquide in France, Dima in Italy, Avarasala in India, Aeonmed in China and Triton in Russia. Full list of manufacturers available here.
How can 3D printing help? 3D printing could only help with intensive care ventilator production by entering the traditional supply chain in order to provide an alternative for temporarily unavailable parts to be assembled by the traditional manufacturers. However, one way 3D printing could provide immediate help is through the rapid development and production of custom splitters that would enable multiple patients to be connected to a single ventilator.
While 3D printing could only help with intensive care ventilator production by entering the traditional supply chain, a number of open-source and low-cost projects have emerged that aim to produce emergency intensive care mechanical ventilators by adapting an Ambu bag into a mechanically activated device. These include projects presented by MIT and Leitat, as well as a number of fully open-source, collective initiatives. While these devices may effectively help to save lives in an emergency, they can be considered to be “stone age” products in medical technology terms. If no other solution exists – and that may very well be the case in some situations that could arise in the near future – they could mean the difference between life and death. However, they should be considered a last resort option.