The key difference between CMV and SIMV is that CMV is a type of mechanical ventilation in which each breath is either assisted or controlled by the ventilator, while SIMV is a type of mechanical ventilation that guarantees a certain number of breaths controlled by the ventilator, with the remaining breaths initiated and partially controlled by the patient.
Mechanical ventilation is also known as assisted ventilation or intermittent mandatory ventilation. It involves using a machine known as a ventilator to fully or partially provide artificial ventilation to critical patients. Mechanical ventilation can be mainly divided into two modes: volume mode (CMV and SIMV) and pressure mode (PCV, PSV, PCIRV, and APRV). CMV and SIMV are two different types of volume-controlled mechanical ventilation.
CONTENTS
1. Overview and Key Difference
2. What is CMV
3. What is SIMV
4. Similarities – CMV and SIMV
5. CMV vs. SIMV in Tabular Form
6. Summary – CMV vs. SIMV
What is CMV?
Continuous mandatory ventilation (CMV) is also known as assist control ventilation (ACV). It is a type of mechanical ventilation where each breath is either an assisted or controlled breath by the ventilator. But these breaths are all of the same volume. Further, CMV does not eliminate the work of breathing entirely, as the diaphragm may remain active during this procedure. The use of larger breath volumes in CMV necessitates more expiratory time. Additionally, there is a risk of developing progressive hyperinflation with this type of mechanical ventilation.
CMV is particularly undesirable for patients who breathe rapidly. This is because they may induce both hyperinflation and respiratory alkalosis after CMV. Anyhow, patients who suffer from respiratory muscle weakness or left ventricular dysfunction should be switched to CMV mode of mechanical ventilation.
What is SIMV?
Synchronized intermittent mandatory ventilation (SIMV) is a type of mechanical ventilation that guarantees a certain number of breaths by the ventilator, and other breaths are partially by patients on their own. This reduces the risk of hyperinflation or respiratory alkalosis.
Mandatory breaths are synchronized to coincide with spontaneous breaths in this procedure. However, there are certain disadvantages in this procedure, such as increased breathing and the likelihood of reducing cardiac output. The addition of pressure support on top of spontaneous breaths can reduce the increased work of breathing. Moreover, SIMV may prolong ventilator dependency in patients as well. Furthermore, patients who breathe rapidly should switch to the SIMV mode of mechanical ventilation.
What are the Similarities Between CMV and SIMV?
- CMV and SIMV are two different types of volume-controlled mechanical ventilation.
- Both types of mechanical ventilations help critical patients to survive.
- They operate in hospital setups.
- Both types of mechanical ventilations have their own advantages and disadvantages.
What is the Difference Between CMV and SIMV?
CMV does not eliminate the work of breathing entirely, as the diaphragm may remain active during this procedure. The use of larger breath volumes in CMV necessitates more expiratory time. Additionally, there is a risk of developing progressive hyperinflation with this type of mechanical ventilation. Thus, this is the key difference between CMV and SIMV. Furthermore, patients who have respiratory muscle weakness or left ventricular dysfunction should be switched to CMV, while patients who breathe rapidly should be switched to SIMV.
The infographic below presents the differences between CMV and SIMV in tabular form for side-by-side comparison.
Summary – CMV vs. SIMV
Mechanical ventilation is a form of life support and therapy. It helps people breathe when they cannot breathe on their own. Mechanical ventilation can be used during surgery or when people are very sick. Mechanical ventilation can be in volume-controlled mode or pressure-controlled mode. CMV and SIMV are two different types of volume-controlled mechanical ventilation. In CMV, each breath is either assisted or controlled by the ventilator, whereas in SIMV, the ventilator guarantees a certain number of breaths, and the patient partially initiates and controls the remaining breaths. So, this summarizes the difference between CMV and SIMV.
Reference:
1. “Continuous Mandatory Ventilation – An Overview.” Science Direct.
2. “Synchronized Intermittent Mandatory Ventilation.” Statpearls – NCBI.
Image Courtesy:
1. “Pressure regulated volume control graphic” By Eduardo Mireles-Cabodevila, MD – The Cleveland Clinic Foundation (CC BY-SA 3.0) via Commons Wikimedia
2. “Clinicians in Intensive Care Unit” By Calleamanecer – Own work (CC BY-SA 3.0) via Commons Wikimedia