mechvent modes

Controlled mandatory ventilation (CMV)

The ventilator delivers the preset tidal volume at a set time interval (time-triggered frequency)

Indications for CMV

Only be used on patient that is properly medicated with a combination of sedatives, respiratory depressants, and neuromuscular blockers

Complications of CMV

Potential for apnea and hypoxia

Rapid this use atrophy of ram fibers

Prolong use of mechanical ventilation leads to

Diaphragmatic oxidative injury, elevated proteolysis, reduced function of the diaphragm.

Most important alarm in CMV (2)

Low exhaled volume alarm

Low inspiratory pressure alarm

Assist control mode is often used to provide

Full ventilatory support

AC modeis used for px who have a stable

Respiratory Drive a stable spontaneous frequency of at least 10 to 12 breaths per minute

In AC mode, ——— control frequency is generally considered as a safety net to provide adequate ventilation in the event that the patient stops triggering the ventilator at an acceptable frequency

Time triggering

Generally accepted minimum frequency in the AC mode is

2-4/ min less than the patient’s assist frequency

The generally accepted minimum control frequency in AC mode is 2-4/min. Less than the patient’s assist frequency or a minimum control frequency of

8 - 10/min

Advantages of AC mode two primary advantages

First, the patient’s work of

breathing requirement in the AC is very small when the triggering sensitivity (pres-

sure or flow) is set appropriately and the ventilator supplies an inspiratory flow that

meets or exceeds the patient’s inspiratory flow demand.

The second advantage of

AC is that, if the patient has an appropriate ventilatory drive, this mode allows the

patient to control the frequency and therefore the minute volume required to nor-

malize the patient’s PaCO2 (Kirby et al., 1988).

Potential hazard associated with AC mode

Alveolar hyperventilation(respiratory alkalosis)

Since IMV BREATHS ARE DELIVERED AT A FREQUENCY, INDEPENDENT OF THE PATIENT SPONTANEOUS FREQUENCY———— may occur

Breath stacking

synchronized intermittent

mandatory ventilation (SIMV):

SIMV

is a mode in which the

ventilator delivers control (manda-

tory) breaths to the patient at or

near the time of a spontaneous

breath. The mandatory breaths are

synchronized with the patient’s

spontaneous breathing efforts so as

to avoid breath stacking.