Doctors call for mechanical ventilation at lower tidal volumes
A New York City hospital intensive care doctor’s plea to review mechanical ventilator protocols in COVID-SARDS cases has gone viral. Originally posted on Twitter, it has been picked up by news media around the world.
Some physicians are questioning ventilator protocols in patients with COVID-19.
Alicia Gallegos, Medscape April 5, 2020 COVID-19 Daily: Ventilator Protocols Questioned, Physician Rights
Italian intensive care doctors have warned about mortality linked to mechanical ventilation Excerpt; ‘A possible explanation for severe hypoxemia occurring in compliant lungs is the loss of lung perfusion regulation and hypoxic vasoconstriction.’ ‘Patients treated with Continuous Positive Airway Pressure or Non-Invasive Ventilation, presenting with clinical signs of excessive inspiratory efforts, intubation should be prioritized to avoid excessive intrathoracic negative pressures and self-inflicted lung injury.’
‘After considering that, all we can do ventilating these patients is “buying time” with minimum additional damage: the lowest possible PEEP and gentle ventilation. We need to be patient.’
AJRCCM Articles in Press. Published March 30, 2020 as 10.1164/rccm.202003-0817LE Copyright © 2020 by the American Thoracic Society High PEEP in a poorly recruitable lung tends to result in severe hemodynamic impairment and fluid retention.
Mechanical ventilation at lower tidal volumes and relevance to SARS-CoV-2
The risks of increased morbidity and mortality from mechanical ventilation are documented in published medical literature from the early 1990s. A trial in 2000 was stopped after the group treated with lower tidal volumes recovered more rapidly than the group treated with traditional tidal volumes.
Considering reports that mechanical ventilation is still a contributory factor in morbidity and mortality in recent SARS-CoV-2 cases suggest this research has not been widely disseminated or implemented. If you or a loved one find yourself requiring emergency care for complications to COVD-19 you might want to share this essential information with your carers.
- Bower RG et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000 May 4;342(18):1301-8. https://www.ncbi.nlm.nih.gov/pubmed/10793162
Excerpt: ‘The trial was stopped after the enrolment of 861 patients because mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes (31.0 percent vs. 39.8 percent, P=0.007), and the number of days without ventilator use during the first 28 days after randomization was greater in this group (mean [±SD], 12±11 vs. 10±11;P=0.007).’
- Lin MS, et al. Improved Survival for an Integrated System of Reduced Intensive Respiratory Care for Patients Requiring Prolonged Mechanical Ventilation Respiratory Care 2013 58 (3) https://www.ncbi.nlm.nih.gov/pubmed/22906762
Excerpt: ‘In conclusion, we have demonstrated that the integrated system of reduced intensive respiratory care, or a well-coordinated, gradually reduced intensive respiratory care regimen, was associated with a slight but significant improvement in the survival rate of prolonged mechanical ventilation subjects.
- Needham D. et al. Lung Protective mechanical ventilation and two year survival in patients with acute lung injury: prospective cohort study. Reducing Breath Size and Pressure From ICU Ventilator Increases Long-Term Survival in People with Acute Lung Injury BMJ 2012
Johns Hopkins Medicine media release March 27, 2012
Excerpt: ‘Adjusting the ventilator to keep the breath size and lung pressures lower can have a dramatic effect on whether or not a patient dies from their lung injury, even long after they leave the ICU.’
- Aufderheide TP et al, Hyperventilation-Induced Hypotension During Cardiopulmonary Resuscitation Circulation Volume 109, Issue 16, 27 April 2004, Pages 1960-1965
Conclusions: Professional rescuers were observed to excessively ventilate patients during out of hospital CPR. Subsequent animal studies demonstrated that similar excessive ventilation rates resulted in significantly increased intrathoracic pressure and markedly decreased coronary perfusion pressures and survival rates.
- Berthiaume Y, Lesur O, Dagenais A. Treatment of adult respiratory distress syndrome: plea for rescue therapy of the alveolar epithelium Thorax 1999; 54 https://thorax.bmj.com/content/54/2/150
Excerpt: ‘Treatment of ARDS at the moment remains mainly supportive since none of the therapies evaluated has been shown to reduce morbidity or mortality….. There is an increasing amount of evidence that mechanical ventilation of the injured lung not only causes further injury but also induces a systemic inflammatory response that could be important for the development of non-pulmonary organ dysfunction.’
- Dreyfuss D, Saumon G. Ventilator Induced Lung Injury Lessons from Experimental Studies Am J Respir Crit Care Med Vol 157. pp 294–323, 1998
Excerpt: ‘There have been many reports on the effect of reducing VT. A reduction from 14 to 11 ml/kg BW was found to improve oxygen delivery in ARDS patients ventilated with a 15 cm H2O PEEP because of better hemodynamics and increased lung compliance. An even greater reduction in VT (from 11 to 8 ml/kg BW, and from 12 to 6 ml/kg BW proved to be safe in these patients: this was associated with little or no change in arterial PaO2 and with increased oxygen delivery. A marked reduction of inspiratory airway pressure is needed in order to decrease lung stretch during mechanical ventilation.’
- Martin C, et al. Pulmonary fibrosis correlates with outcome in adult respiratory distress syndrome. A study in mechanically ventilated patients. Chest. 1995; 107:196–200. [PubMed: 7813276
Excerpt; The development of fibrosis seems to be an important determinant of mortality attributable to mechanical ventilation regardless of the cause of ARDS.
- Nuria, E et al. Mechanical Ventilation- Associated Lung Fibrosis in Acute Respiratory Distress Syndrome A Significant Contributor to Poor Outcome Anesthesiology. 2014 July ; 121(1): 189–198
Conclusions: Mechanical ventilation, particularly where significant overstretch occurs, may drive the pathogenesis of fibrosis in patients with ARDS. The application of mechanical ventilation in animal models of acute lung injury or the application of mechanical stress in vitro in lung epithelial cells can induce the development of lung fibrosis through fibroproliferation and epithelial–mesenchymal transition (EMT).
About this Post
The New Zealand Government and front-line workers in our hospitals are doing an exemplary job in containing the spread of this virus.
Please note neither this post/blog nor any linked articles claim that nasal breathing or humming prevent or cure COVID-19. However, now more than ever it makes sense both for physical and psychological reasons to take any steps that may improve our health. Like the advice to wash our hands frequently, the advice to nasal breathe also gives us a sense that there is something we can do, a sense of control and anything that makes us feel less stressed is also good for our immune system.
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