ICU and mechanical ventilation Flashcards
Give some aims of ventilation
- provide O2 for the blood flowing through the lungs
- remove waste products of CO2 from the blood in the lungs
How is breathing controlled by the body?
Homeostasis - ventral and peripheral chemoreceptors
Respiratory control centre in the brainstem
Briefly describe Boyle’s Law
Inspiration = increased volume means decreased pressure, ribs move up and out, diaphragm flattens Expiration = decreased volume means increased pressure, ribs fall down, diaphragm raises
How does positive pressure ventilation work?
Positive-pressure ventilators work by increasing the patient’s airway pressure through an endotracheal or tracheostomy tube. It creates a gradient between the pts mouth and lungs.
Give the 2 ventilation classifications and briefly describe them
- Volume controlled
- machine aims to achieve a set volume and then cycles into expiration
- we can put a certain volume of air into the pt with each breath in mechanical ventilation
- minute ventilation fixed
- inspiratory pressure variable - Pressure controlled
- machine aims to achieve a set pressure and then cycles into expiration
- we can put air into the pt until the pressure reaches a certain value
- minute ventilation variable
- inspiratory pressure fixed
What is peak inspiratory pressure (PIP) for non-ventilated and ventilated pts?
What can increase PIP?
What is the maximum value of PIP?
Highest level of pressure applied to the lungs during inhalation.
When ventilated PIP is the highest amount of pressure in the chest and in the ventilator circuit when the lungs are filled with air.
PIP increase with airway resistance (secretions, bronchospasm, biting down on ventilator tubing)
Should never be above 40cmH2O unless pt has ARDS.
What are peak and plateau pressures and what causes them both?
Peak pressure = applies when there is airflow in the circuit, i.e. during inspiration. What determines the peak pressure is the airway resistance in the lungs. So it follows that if there is a problem with the airways the peak pressure will rise. A high peak pressure is an airway issue:
Bronchospasm
Retained secretions
Plateau pressure = applies when there is not airflow in the circuit. That is when inspiration is complete. This pressure is determined by the lung compliance. A high plateau pressure is a compliance issue: Pneumothorax Pulmonary oedema ARDS Pneumonia.
Describe the levels of invasive positive pressure ventilation
1. control pt conciousness = low pt sedation = high breaths triggered by the machine set RR, inspiratory:expiratory ration, TV of pressure and PEEP 2. back up pt conciousness = mid pt sedation = mid supports breath triggered by pt machine breaths triggered when pt doesnt trigger 3. support pt conciousness = high pt sedation = low breaths triggered by pt set pressure support and PEEP TV, I:E, RR controlled by pt
GIve some complications of mechanical ventilation
- ventilator associated pneumonia (VAP)
- cardiovascualr (CVS) changes
- retained secretions
What standard monitoring is done when ventilated?
Blood pressure Mean arterial pressure Blood oxygen saturation Heart rate Central venous pressure
How can you care for a pt with VAP?
- elevation of bed (30-45degrees) to prevent aspiration of gastric content
- daily sedation interruption
- use of subglottic secretion drainage
What is considered a weaning failure?
Failure to pass a spontaneous breathing trial or the need for reintubation within 48 hours of extubation.
Give the three names for weaning failures
Group 1 - short weaning
- first seperation attempt resulted in termination of the weaning process within 24 hours
Group 2 - difficult weaning
- weaning was terminated after more than 1 day but in less than 1 week after the first seperation attempt
Group 3 - prolonged weaning
- weaning was still not terminated 7 days after the first seperation attempt
