mv lab

• Mechanical ventilator


  A device that is used to provide positive pressure ventilation (PPV) in order to help normalize a patient's arterial blood gas levels to maintain adequate acid-base balance
• Iron lung


  • Uses negative pressure
  • Patient goes inside, and the machine creates negative pressure which expands the lungs
  • Used in older days
  • Negative pressure ventilation mimics normal breathing, generates negative pressure for air to enter and at the end of inspiration pressures are equalized, then pressure is removed for exhalation
  • Disadvantage: minimal access to patient for taking vital signs because the whole body is inside the machine and only the head is accessible
  • At inspiration, the pressure decreases to enter air
• Chest cuirass


  • Covers chest part only
  • Not allowed to use when lying, only allowed to use in elevated position
  • Advantage: It is easy access to patient in taking vital signs
• Two modes of delivering positive pressure ventilation (PPV)

  • Non-Invasive
  • Invasive
• Non-Invasive ventilation


  • BiPAP
  • CPAP
  • These 2 are most common non-invasive delivery ventilation (PPV)
  • CPAP can be used on intubated patients when weaning, but it will be considered as INVASIVE
• Non-invasive ventilation masks


  • 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
  • Most common
  • Difference from nasal mask is it covers the mouth as well
  • Disadvantage: remove while eating
  • Most expensive (₱5,000, single use only)
  • Application: should have no leak
  • Sizes: neonates, pediatrics, small, medium
• 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
  • It is basically a nasal cannula but with larger fittings that fit snugly in the nostrils
• 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 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 in certain countries
  • Developed to improve tolerability and reduce complications in patients with acute respiratory failure on non-invasive ventilation
  • Not commonly used in patients with acute hypercapnic respiratory failure because it can lead to CO2 accumulation
• Three ways to deliver 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, so should be used with caution
  • Most common positive pressure ventilation delivery
  • Two types of laryngoscope for intubation: Miller (infants, pediatrics) and Macintosh (pediatrics and adults ranging from 2-70 years old)
• Nasopharyngeal intubation


  • Involves inserting a thin, clear, flexible tube into a patient's nostril
  • Purpose is 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
  • Not common
• Tracheostomy


  • A small surgical opening made through the front of the neck into the windpipe or trachea
  • A curved plastic tube, known as a tracheostomy tube, is placed through the hole allowing air to flow in and out of the windpipe
  • Done when nasal access is not available, when there is upper airway obstruction, or for long-term use
  • Usually done when the upper airway is swollen or the patient is prone to extubation or self-extubation, and the endotracheal tube size keeps getting smaller with each subsequent intubation
• Endotracheal tube (ETT) level

  • Male: 21-23 cm
  • Female: <21 cm
  • Anatomically, ETT is longer in males compared to females
  • ETT is inserted 2-5 cm above the carina, which can be confirmed by chest X-ray and bilateral equal lung sounds
• How a mechanical ventilator works

  1. Ventilator generates airflow into the patient

  2. Air passes through a humidifier to prevent drying of the airway

  3. Air flows through the inhalation limb tubing to the patient

  4. After inspiration, exhalation occurs passively through the exhalation limb tubing back to the ventilator

  
• Two types of mechanical ventilator circuits

  • Closed circuit
  • Open circuit

  
• Closed circuit ventilator


  • Exhalation limb tube directs exhaled air back to the ventilator
  • Has a built-in exhalation valve
  • Includes a proximal line to measure pressure
  • Allows the ventilator to monitor and control the pressure and volume

  
• Open circuit ventilator


  • Has an exhalation valve at the end of the tubing
  • Has a proximal line back to the ventilator to measure pressure
  • Typically has an analog interface and manometer
  • Does not have a built-in PEEP, so a PEEP valve is added to the exhalation port

  
• Filters


  • Ideally 2 filters are used, one on the inhalation and one on the exhalation limb
  • If only one filter is used, it is typically placed on the exhalation limb to filter the air returning to the ventilator
  • The ventilator in the pulmonary lab has a heated filter built-in
• Inhalation and exhalation cannot occur simultaneously on a mechanical ventilator
• Heat Moisture Exchanger (HME)


  • Serves the role of a humidifier
  • Can be used instead of a humidifier
• Backfill


  • Added before the tubing to prevent contamination of the air returning to the ventilator
  • Can also be added to the exhalation limb