mv lab

• Mechanical Ventilator


  A device used to provide positive pressure ventilation in order to help normalize a patient's arterial blood gas levels to maintain an adequate acid-base balance
• Examples of Mechanical Ventilators

  • Iron Lung
  • Chest Cuirass
• Iron Lung


  • Mimics the breathing cycle of the patient
  • Negative pressure
• Chest Cuirass


  • Works with the same principle as the iron lung but only need to be around the chest of the patient
• What happens during breathing

  1. Negative pressure is needed for air to enter the lungs during inspiration

  2. There is a pause at the end of inspiration, the pressure difference will be zero

  3. At the start of expiration, the lung will generate positive pressure to squeeze out the air in the lungs
• Two ways to deliver positive pressure ventilation

  • Non-invasive Ventilation
  • Invasive Ventilation

  
• Modalities used in Non-invasive Ventilation

  • Nasal Mask
  • Oro-nasal Mask
  • Nasal Pillow
  • Oral Mask
  • Total Face Mask
  • Helmet
• Nasal Mask


  Covers the nose only and rests on the upper lip, the sides of the nose, and the nasal bridge
• Oro-nasal Mask


  Covers the nose and mouth and rests on the chin, the sides of the nose and mouth, and the nasal bridge
• Nasal Pillow


  Fits on the rim of the nostrils, usually recommended for individuals who find nasal or oro-nasal masks uncomfortable or experience skin breakdown on the nasal bridge, used mainly in stable patients with sleep-disordered breathing
• Oral Mask


  Fits inside the mouth between the teeth and lips and has a tongue guide to prevent the tongue from obstructing the airway passage, not common in practice
• Total Face Mask


  Covers the whole face and is used mainly in patients with ARF (acute respiratory failure)
• Helmet


  A transparent hood that covers the entire head and face of the patient and has a rubber collar neck seal, used as an alternative to the oro-nasal mask in patients with acute hypoxemic respiratory failure or acute cardiogenic pulmonary edema, not commonly used in patients with acute hypercapnic respiratory failure
• Modalities used in Invasive Ventilation

  • Oropharyngeal Intubation
  • Nasopharyngeal Intubation
  • Tracheostomy
• Oropharyngeal Intubation


  Insertion of a tubular device into a canal, hollow organ, or cavity, can cause gagging and the potential for vomiting and aspiration in conscious patients and so should be used with caution
• Nasopharyngeal Intubation


  Involves inserting a thin, clear, flexible tube into a patient's nostril to bypass upper airway obstruction at the level of the nose, nasopharynx, or base of the tongue, and prevent the tongue from falling backward on the pharyngeal wall to prevent obstruction
• Tracheostomy


  A small surgical opening that is made through the front of the neck into the windpipe, or trachea, with a curved plastic tube, known as a tracheostomy tube, placed through the hole allowing air to flow in and out of the windpipe
• Ideal position of distal tip of ETT within the trachea - 2.5 cm above the carina
• Length of inserting the ETT: Male (21-23 cm) and Female (21 cm)
• How a Mechanical Ventilator Works

  Ventilator generates airflow going to the heated pass humidifier to the inhalation limb to the patient, after inspiration, expiration of airflow to the exhalation limb going back to the ventilator

  
• Types of Ventilator Circuits

  • Closed-type Ventilator
  • Open-type Ventilator

  
• Closed-type Ventilator


  The airflow goes back directly to the ventilator

  
• Open-type Ventilator


  Has exhalation valve at the end of the expiratory limb and a proximal line that goes back to ventilator that can measure the pressure or the Pplat by kinking it when the mechanical ventilator delivers a breath

  
• Types of Mechanical Ventilators

  • Turbine
  • Compressor

  
• Bacterial Filter


  Located at the exhalation valve
• HME


  Located at the inhalation valve, alternative to humidifier
• Four Basic Functions of Ventilator

  • Input Power
  • Power Transmission
  • Control System
  • Output (Pressure, Volume, and Flow Waveforms)

  
• Input Power


  The power source for a ventilator is either electrical energy or compressed gas

  
• Electrically powered ventilators are typically used in the hospital directly to the power outlet, won't operate unless there is backup batteries, and are being used as transport ventilators with life span for about 4-6 hours
• Pneumatically powered ventilators such as specialized ventilators in the specialized units or ICU use compressed gas like O2

  
• Parameters in Ventilators


  • Mode
  • Tidal Volume/PIP
  • RR/Back Up Rate/Frequency
  • Flow Rate (40-60 lpm and can reach 200 lpm in special cases)
  • FiO2
  • I time
  • Sensitivity

  
• Power Transmission and Conversion

  The power transmission and conversion system consists of a drive mechanism that generates the actual force needed to deliver gas under pressure, and output control mechanisms that regulate the flow of gas to the patient
• Control System


  • Control Circuit
  • Control Variables
  • Phase Variables
  • Baseline Variable
• Control Circuit


  A system of components that measures and directs the output of the ventilator to replace or assist the breathing efforts of the patient, may include mechanical, pneumatic, electrical, electronic, or fluidic components

  
• Control Variables


  • Pressure
  • Volume
  • Flow
• Phase Variables


  • Trigger Variable (Time Triggering, Pressure Triggering, Flow Triggering)
  • Target Variable
  • Cycle Variable
• Baseline Variable


  The parameter controlled during expiration, typically pressure control

  
• Pressure Triggering


  Inspiration is initiated by the patient's effort to breathe
• Flow Triggering


  Inspiration is initiated when the patient's inspiratory flow reaches a preset level
• Target Variable


  A variable that can reach and maintain a preset level before inspiration ends but does not terminate inspiration. Pressure, flow, or volume can serve as a target variable.