The medical term “ventilator” is a generic description for a device that provides respiratory support to patients suffering from varying degrees of respiratory distress. General purpose ventilators are capable of various different modes of ventilation that provide the required level of support/treatment to the patient. CPAP (Continuous Positive Airway Pressure) is a specific supportive mode that allows the awake and spontaneously breathing patient to receive non invasive respiratory support. The NVP CPAP devices are a simple ventilator that provides only a specific respiratory support modality.
Full-function medical ventilators are complex devices that provide a range of invasive and non-invasive respiratory support modalities to a patient ( of which CPAP is typically one of the modes). These devices are usually expensive to procure, more complex to use, and require specialist medical staff and facilities. The NVP CPAP devices are very simple and inexpensive because they only provide a single non-invasive Continuous Positive Airway Pressure (CPAP) ventilation mode.
The COVID virus, and the response of the body’s own immune system, cause the air sacs (alveoli) in the lungs to become less efficient at transferring oxygen to the bloodstream, resulting in respiratory distress and hypoxia. The alveoli become filled with a sticky fluid, reducing the lung’s ability to inhale air, and the walls of the alveoli become less able to transfer oxygen to the blood. To counter these effects, CPAP provides respiratory gas to the patient that has an elevated oxygen concentration to mitigate the loss in oxygen transfer efficiency, and at a slightly elevated pressure to assist the inflation of the alveoli and prevent their complete collapse at the end of expiration. The oxygen concentration and gas flow and pressure are adjusted to the needs of the patient. The CPAP therapy is non-invasive, requiring the patient to be awake and breathing spontaneously.
The NVP has gone into production with two different devices, but a number of other device concepts were explored and prototypes built and tested in the early phase of the project. The two production devices were the CSIR L.I.F.E. ambient air entrainment system and the SAVE-P CPAP 100 medical air/oxygen blender system.
The production of both devices has been licenced by the South African Health Products Regulatory Authority (SAHPRA) under Section 21 provisions for use during the duration of the COVID pandemic. Permanent licencing is being investigated currently.
The oxygen consumption of any respiratory support modality depends on the severity of respiratory distress presented by the patient. The patients’ severity of illness and following response to therapy determine the ultimate demand. Total gas flow ( Oxygen plus air mix) is always determined by the patient- those breathing harder will require more flow and this is then accommodated by increasing the flow generated by the device. Since FiO2 and flow are set independently, once the desired FiO2 has been set, flow can be increased or decreased according to the patients demand and comfort level.

Patients who respond well to CPAP therapy need an oxygen flow anywhere in the region of about 10-25 litres per minute (LPM). Those requiring very high total flow rates and oxygen concentrations without evidence of definitive early improvement will probably need to have the type of respiratory support escalated to a more advanced mechanical ventilator, and in all likelihood will require invasive ventilation.

Even an oxygen flow of 10 LPM will drain a large oxygen cylinder within 9 hours, and smaller cylinders will be depleted on proportionately shorter timescales. This implies that a hospital ward oxygen supply is needed for normal CPAP therapy that might last a few days. Cylinders can be used in an emergency, or while a patient is being transferred.
The suppliers of oxygen to public and private hospitals have been able to keep up with the demand for bulk liquid oxygen as used at larger hospitals with VIEs (vacuum insulated evaporators). The suppliers have diverted production of industrial oxygen to the production of medical oxygen to ensure adequate capacity. There have, however, been challenges caused by inadequate oxygen reticulation infrastructures at these hospitals. Shortages of gas cylinders have been a problem for hospitals that rely on oxygen gas cylinders for their reticulation systems.
Yes. At this time there are about 9,000 devices available. The devices are re-useable, but the associated patient circuits are for single use only. The NVP has a stockpile of patient circuits, and they can also be sourced via standard hospital procurement procedures.
All hospitals in South Africa (public and private) can apply for the devices.
The device, together with three patient circuits, are supplied free of charge, including delivery. The Solidarity Fund has covered all costs.
Private Hospitals need to arrange shipping for SAVEP devices (shipping to public hospitals will be arranged by NVP). CSIR devices shipping to all hospitals will be arranged by NVP.
The CSIR L.I.F.E. CPAP device uses a high-velocity jet of oxygen, derived from a 400 kPa pressurised medical oxygen supply, to entrain ambient air to provide the required oxygen concentration, and hence air/oxygen ratio. The oxygen concentration (FiO2) and gas flow are controlled independently by two knobs on the device.

The SAVE-P CPAP 100 device blends 400 kPa pressurised medical air and oxygen in correct ratio, using a proportional mixing valve, to achieve the desired oxygen concentration. Independent knobs control the FiO2 and gas flows.

Both devices provide the same functionality, and feed the oxygen-enriched gas into identical patient circuits. FiO2 and gas flow are adjusted at the blender to meet the needs of the individual patient.

Patient circuits are the single-use disposable components of the CPAP system that supply the oxygen-enriched gas from the blender to the patient in a safe and effective way. The main components of the patient circuit are a flexible tube, a mask, pressure valves and filters.
The flexible tube transfers the oxygen-enriched air from the blender to the mask, which must cover the patient’s nose and mouth to prevent leakage. Leakage would reduce the support being supplied to the patient, and also allow the escape of virus-laden exhaled air. The pressure of the gas in the system is controlled by a PEEP (positive end expiratory pressure) valve, ensuring that the patient’s lungs remain inflated throughout the entire breathing cycle. The PEEP valve is adjustable, allowing the PEEP to be customised to the patient’s needs and comfort level. A secondary safety pressure valve ensures that the supplied pressure never exceeds unsafe levels that might lead to barotrauma, and an anti-asphyxia valve ensures that the patient can always breathe safely, even if the gas supply fails. An HME (heat/moisture exchange) filter keeps the supplied gas at a comfortable humidity level, and also blocks viruses in the exhaled air from contaminating the ward.
Humidifiers are not required or desirable for CPAP therapy where a filter is being used for viral filtration as the active humidification will cause the filter to become wet and increase work of breathing for the patient. The SAVE-P devices are supplied with a humidifier for use with configuration as HFNO therapy.
The videos contained in this link provide information on the deployment and use of the NVP CPAP devices.

CSIR Device Training Videos

  1. Formal training video – http://bit.ly/CSIRTrainingVideo
  2. Training by Dr Oliver Smith – http://bit.ly/droliversmith

NDOH Training Video that also Includes SAVEP Device

  1. https://drive.google.com/file/d/1WUUoKzNn_EOXHoYyOErb9xMUukf6u3ci/view
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