The Mechanical Ventilator works according to the patient’s degree of awareness and ability to breathe, and this difference is called ventilator modes, and there are many of them, but they all fall under the positive pressure ventilator. There are many types of mechanical ventilator and modes divided into:

  • Volume Cycled: In this type, the ventilator will cause lung inflation at a constant rate until the entire required volume of air gets into the lung because the VT, or amount of air that will enter the lung with each breath, will be determined. In other words, even if there is a blockage in the airways that increases airway resistance, the amount of air specified for entering the lung will enter with increased pressure, and the ventilator will therefore work at the highest pressure possible in order to be able to enter the air into the lung. As a result, the high pressure may cause an increase in pressure inside the lung and to the alveoli causing lung damage. This type includes two modes for the ventilator which are:
  1. ACV  : Assistant – Control Ventilation
  2. SIMV : Synchronized Intermittent Mandatory Ventilation
  • Pressure Cycled: In this type, the PIP is determined, which is the amount of pressure required for air to enter the lung, and therefore the ventilator will not cause pressure inside the lung like the other type. Rather, this type changes the amount of air according to the patient’s needs at a constant pressure rate. This type includes six modes for the mechanical ventilator which are:
  1. PCV: Pressure Control Ventilation
  2. PSV: Pressure Support Ventilation
  3. CPAP: Continues Positive Airway Pressure
  4. BIPAP: Bi Phasic/Level Positive Airway Pressure
  5. HFOV: High Frequency Ventilation
  6. APRV: Airway Pressure Release Ventilation

Volume Cycled Modes

  • ACV Mode: Assistant – Control Ventilation

To understand this mood, it can be divided into two classification which is assistant and control.

  1. Assistant ! The patient takes a breath but cannot complete it to the end because he has weakness in the respiratory muscles. The patient may take the breathe slowly or rapidly. The ventilator helps him to complete the breath to the end (inhale) and withdrawal air from the lung to complete the process (exhale). The condition named as patient triggered breath because the patient who starts the breath not the device.
  2. Control ! The patient cannot take a breathe at all. The ventilator here begins the intervention completely as it gives the breath (inhale) to the end and begins to take it again (exhale). This condition named as controlled or time trigger because the ventilator starts the breath.


The ventilator can take the breath to the end if the patient cannot do it and if the patient can’t take a breath at all, the MV can do it also instead of him.


If the patient took a short breath continuously and rapidly, the ventilator won’t understand that, all the ventilator do is to complete the breath if the patient didn’t, so the ventilator will continue to complete the breath to the end of every one rapidly and this will lead to tachypnea and hyperventilation will be the result.

The Treatment

The best treatment is by giving sedation or by changing ventilator mode to SIMV mode.

  • SIMV Mode: Synchronized Intermittent Mandatory Ventilation

This mode consists of two parts which are spontaneous breath and ventilator breath.

  1. Spontaneous Breath ! The patient takes the breath automatically, whether he takes a full breath or even half of it, whether slowly or quickly.  The ventilator will not interfere at all except in the event of a complete cessation of breath.
  2. Ventilator Breath ! The patient can’t take a breath at all. The ventilator will work and gives him a full breath.


The patient can take a breath automatically without any interfere from the device whether the patient takes the breath short or long, rapidly or slowly.


The ventilator will only intervene in case of  complete cessation of breathing by the patient and won’t complete the patient breath if the patient wants.

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