TYPES OF BREATHS/MODES:
2 (TYPES) –
(1) VOLUME CONTROLLED (VC) BREATH.
The tidal volume is preset and constant, but the pressure varies. The vent will push set volume of gas into the lungs and will use whatever pressure it takes to deliver it, as long as the pressure required does not exceed the alarm limit.
Advantages: guaranteed volume of breath delivery; Disadvantages: high pressures causing leak around uncuffed trach.
(2) PRESSURE CONTROLLED (PC) BREATH
The pressure is preset and constant, but now the volume varies. The vent pushes gas into the lungs until a preset pressure is reached. It then holds and maintains that pressure until the "Inspiratory Time" is reached, then the Pt. passively exhales.
Advantages: compensation for leaks & controlled airway pressures; Disadvantages: variable tidal volume delivery.
TERMS TO KNOW:
Tidal Volume (Vt): Volume of inspired gas in mL per breath.
Exhaled Vt (Vte): Vt delivered is close to what is being exhaled. If Vte is significantly less than Vt, may indicate a leak in the circuit or around the trach.
Breath Rate (Set Rate or Backup Rate): Minimum # of vent-controlled breaths delivered per minute.
Respiratory Rate (RR): Total respiratory rate—both backup and Pt. triggered breaths
Inspiratory Time (measured in seconds):
If vent in volume control mode
– speed of gas going into Pt. (how fast Vt delivered);
If vent in pressure controlled mode – length of time breath stays in the lungs before exhalation.
Minute Volume (MinVent): Amount of gas moved in & out of lungs (measured in Liters) per minute (Total RR x Vt).
Peak Inspiratory Pressure (PIP): The pressure required to push the breath into the Pt. High airway pressures can damage lungs or may indicate obstruction (see alarms).
Positive End Expiratory Pressure (PEEP): The setting that holds pressure in the lungs after exhalation. This helps keep the lungs open, prevent collapse, and oxygenate the blood. Higher the PEEP, the more pressure/ inflation held in lungs after exhalation.
Leak: Amount of gas flow lost from circuit. Some is allowed.
A disconnect can cause a disconnect alarm, a low pressure alarm, a low tidal volume alarm, a low minute volume alarm, low circuit leak.
All vents must have an alarm that signals if there is too much pressure in the circuit, too little pressure in the circuit, or too little tidal volume or minute volume being delivered to the Pt., so the caregiver knows if there is something blocking or impeding gas flow (high pressure) or if there is a leak or disconnect (low pressure and/or low volume).
POSSIBLE CAUSE & SOLUTION
Low Exhaled Tidal Volume [Low Vte] and Low Exhaled Minute Volume
(Alarms when pt. breathes less/ slower) (If in PC Mode and Vt decreases).
Same as Low Pressure Limit alarm.
airflow obstruction - SOLUTION: If mucus obstruction –
Low Inspiratory Pressure
(In PC-SIMV mode, the low pressure limit is set at 5cm H2O below the mandatory breath). Pressure should build as a breath is delivered. If there’s a leak or disconnect and pressure drops below preset alarm limit, the vent will sound the alarm.
Leak around the trach - SOLUTION: Reposition head. May need eval for bigger trach.
Disconnected from the vent - SOLUTION: Find disconnect & reconnect the circuit.
Hole in the circuit or cracked water chamber - SOLUTION: Replace.
Loose connection - SOLUTION: Find and tighten the loose connection. Look at all circuit components (temp probe ports, connection to the water chamber and vent outlet port, flex tube, artificial nose, O2 ring, swivel adapter, flow sensor or exhalation lines).
Alarm limit inadvertently changed - SOLUTION: Verify proper setting and adjust.
High Pressure Limit
(In PC-SIMV mode, the high pressure limit is set at 5 cmH20 above pressure setting). Vent will stop delivering breath to prevent further pressure build.
Mucus in the airway (volume breaths only) - SOLUTION: Suction.
Bronchospasm (volume breaths only) - SOLUTION: Breathing Tx /Bronchodilator per orders.
Coughing - SOLUTION: N/A
Alarm limit accidently changed - SOLUTION: Verify setting (not adjustable on Trilogy).
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