Dr Satya Dev Gupta
In this period of Coronavirus (COVID19) pandemic throughout the world, many people are acquiring the disease due to contact. The dreadful complication is the environment of the lungs. In response to the infection, the defense mechanism of the body produces several antibodies and other defensive products. While doing so there is a thickening of the inner lining of air sacs and airways. Moreover, these get flooded with the secretions resulting in the decrease in the caliber of bigger airways and blockage of smaller ones leads to an increase in airways resistance. The air sacs are swollen and unable to expand while breathing. The exchange of gases i.e. Oxygen and Carbon dioxide are hampered resulting decrease in Oxygen and an increase in Carbon dioxide in the blood; if not corrected results into vital and then multi-organ failure. Here comes the role of Oxygen supply and Ventilation therapy which is administered by Oxygen masks, bronchodilators, lungs toileting, CPAP (Continuous positive airway pressure), BIPAP Bibhasic Intermittent Positive Pressure) ventilation and Ventilators. The following paragraphs will describe the scope of ventilators from their advent to the advancement.
Road leading to Intensive Care and Ventilators
In 1952, Copenhagen was struck by a severe epidemic of poliomyelitis that included a large number of cases of bulbar polio (involvement of medulla oblongata and upper spinal cord) resulting in respiratory paralysis. During the period from August to December, about 3,000 patients with polio were admitted, mainly to one infectious disease hospital, the Blegdam Hospital, and of these, about 1,250 had some type of paralysis. As 345 patients had bulbar polio affecting the respiratory and swallowing muscles. For several weeks, 30-50 patients with bulbar symptoms were admitted daily and 6-12 of these were desperately ill. During the first 3 week of the epidemic 27 of 31 patients with bulbar polio died, 19 of them within 3 days of admission, clearly a catastrophe was in the making. Indeed, Henry Cai Alexander Lassen (1900-1974), chief physician at the hospital stated: “Although we thought we knew something about the management of bulbar and respiratory poliomyelitis it soon became clear that only very little of what we did know at the beginning of the epidemic was worth knowing”. The epidemic resulted in two enormous challenges in applied physiology. The hospital lacked ventilators. The stunningly innovative solution was to use manual positive pressure ventilation administered by a roster of 200 medical students who repeatedly squeezed a rubber bag attached to a tracheostomy tube around the clock. The second challenge was understanding the life-threatening abnormalities of pulmonary gas exchange and acid-base status. At the start of the epidemic, the only laboratory test available was the total carbon dioxide concentration of the blood and the high values bicarbonate
The introduction of manual bag ventilation early in the epidemic was due to the anesthesiologist Bjørn Ibsen (born: 1915) who had spent a period in the Department of Anesthesia at the Massachusetts General Hospital (1904-1976). Earlier in 1952, Ibsen had been involved in the treatment of a child with tetanus who was paralyzed to be ventilated manually through a tracheostomy (a self-made hole in the upper windpipe).
His ideas and practices during this time also started the development of the intensive care unit towards what it is today; and, together with the collaborative enthusiasm of the introduction laboratory chief Poul Astrup, fostered the introduction of regular blood-gas and acid-base analyses into the daily management of the intensive care patient the novel approach at Copenhagen. Before Ibsen introduced his methods, infectious disease departments often treated respiratory failure in polio patients with either a cabinet “respirator” or a body cuirass respirator, both providing negative pressure ventilation. It is emphasized and to be understood that our normal breathing is dependent upon the negative pressure dynamics.
The ventilation method was a known anesthetic technique used in the operating theatre and the same anesthetic system could be applied to critically ill patients. To supply the labor for M-IPPV (mechanical intermittent positive pressure) in the months ahead, Lassen, as described earlier organized shifts of approximately 1500 volunteer medical students, (later joined by dental students), 600trained nurses and hundreds of auxiliary personnel, student nurses and semi-retired nurses. They were supervised by anesthetists and assisted by each patient’s’ special’ nurse. With these teams, “despite the unabating severity of the fresh cases”, the mortality among ventilated patients had decreased from 87% recorded before the introduction of the new system, to 26%.
Fighting with Corona with modern concept
Taking a leaf from the book of the above-mentioned efforts by the medical team, we can do a lot for the critical and desperately sick patients. For that, it is mandatory to understand the respiratory physiology and mechanics of the ventilators. Unlike polio, the Coronavirus disease doesn’t paralyze the respiratory muscles of the patients. In fact, they have spontaneous breathing that may not be sufficient to breathe in Oxygen and exhale Carbon dioxide. Since 1950 there is an impetus of advancement in understanding the respiratory and ventilator’s functional analysis the mortality rate has decreased. For simple understanding, the respiratory system involvement in Corona viral disease, the treatment is based on the application of the methods from simple to advanced. In usual cases, it can be started by administering the drugs, physiotherapy, and Oxygen with the encouragement of clearing the airways of secretions and mucous. In the course of treatment, the vital signs monitoring (pulse, blood pressure, Ecg, hemoglobin Oxygen saturation, levels Carbon dioxide in expired air i.e. Etco2, etc.) are measured. Advanced investigations i.e. arterial blood gas levels and many others as required are done. If a patient doesn’t show any improvement CPAP and BIPAP are applied. These are airways positive pressure generating methods that act as a stent to recruit and open the air sacs which are usually closed, for improvement of oxygenation and ventilation. If it works, the patient shows improvement; if not then we have to switch on the ventilators. There are two types of non-invasive and invasive. The non-invasive ventilators allow the patients to be awake and alert, while in invasive ventilators an endotracheal or tracheostomy tube put to connect the windpipe with the ventilator. The patient in this situation is sedated or made unconscious. There are different parameters in ventilators i.e. respiratory rate, minute volume, tidal volume (per breath volume), time for the cycle of inspiration and expiration; supply mode of ventilator flow and pressure to the patient’s airway and changes in aerodynamics are monitored from time to time.
The ventilators are very complex machines and must be supervised by the experts i.e. critical care and intensive care specialists. A group of resident doctors, paramedical staff, physiotherapists, lab technicians, etc. are needed. ICU is a multimodal and multidisciplinary ward where no stone can be left unturned in the treatment of the patient.
So, to fight against the pandemic of COVID19 (Coronavirus) every possible effort has to be put to defeat this dreadful disease and its complications. Some new and innovative technologies can be applied as and when required.
(The author is ICU Specialist and Ex-Head of Department of Anesthesia and Intensive Care Unit Government Medical College Jammu)
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