Influence of ventilatory strategies on outcomes and length of hospital stay: assist control and synchronized intermitten
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IM - COMMENTARY
Influence of ventilatory strategies on outcomes and length of hospital stay: assist control and synchronized intermittent mandatory ventilation modes Diego Casali1 Received: 26 September 2020 / Accepted: 30 September 2020 © Società Italiana di Medicina Interna (SIMI) 2020
I read with interest the article published by Thais Bruno de Godoi and colleagues in the current issue of “Internal and Emergency Medicine” [1]. This single-center, observational, and retrospective study performed on 345 adult ICU patients shows that the mortality, duration of mechanical ventilation, length of hospital stay, failed extubation, and need for tracheostomy are statistically similar between the synchronized intermittent mandatory ventilation with pressure support ventilation (SIMV + PSV) mode and the assist-control (A/C) mode. This study compares outcomes of patients ventilated with A/C mode or intermittent mandatory ventilation (IMV) mode under nonweaning conditions, and it confirms the clinical observation that no mode of mechanical ventilation results in better outcomes and that any mode can be successfully used by a knowledgeable and skillful intensivist. The concept of allowing the patient to breathe spontaneously between machine-cycled or mandatory breaths originated in 1955 with an unnamed ventilator designed by Engstrom [2, 3]. In 1971, Kirby and colleagues [4, 5] introduced IMV as a means of ventilator support of infants with respiratory distress syndrome. In 1973, Downs and colleagues [6] proposed IMV as a method to facilitate liberation from mechanical ventilation in adults by allowing the patient to take unhindered breaths while still receiving a background of controlled breaths. Proposed advantages include decreased sedative requirements, decreased mean intrathoracic pressure with less barotrauma, and less adverse hemodynamic consequences, improved intrapulmonary gas distribution, continued use of respiratory muscles, and faster liberation from mechanical ventilation.
* Diego Casali [email protected] 1
Cardiac Surgery Intensive Care Unit, Smidt Heart Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA
The SIMV mode is very similar to the A/C mode. In fact, when the patient is apneic or breathes at or below the set mandatory respiratory rate, the two modes are indistinguishable. Like A/C, SIMV provides the patient with an intensivist-selected mandatory breath rate, and during every calculated breath interval it delivers a single mandatory breath, which can be either time or patient triggered. The difference between the two modes only appears when the patient triggers additional spontaneous breaths. In the A/C mode, spontaneous and mandatory breaths are the same, whereas in the SIMV mode, different breath types are always used. Similarly to A/C, mandatory breaths in the SIMV mode can be volume control, pressure control, or pressure-regulated volume control breaths. Spontaneous breaths, however, are always pressure support breaths. As shown in the article pu
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