MV LAB

• Mechanical ventilator


  A device that is 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
• 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 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
• 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, the 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
• Tracheostomy


  Also known as a tracheotomy, is a small surgical opening that is 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, the tube does not extend into the lungs
• 4 basic functions of ventilators


  • Input power
  • Power transmission and conversion
  • 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 ventilator


  Uses voltage from an electrical line outlet
• Pneumatically powered ventilator


  Uses compressed gas as its power source
• Power transmission and conversion system


  • Consists of a drive mechanism and output control mechanisms
• Drive mechanism


  Generates the actual force needed to deliver gas under pressure, can be either a direct application of compressed gas via a pressure-reducing valve or an indirect application via an electrical motor or compressor
• Output control mechanisms


  Regulates the flow of gas to the patient, may be a simple on/off exhalation valve or can shape the output waveform, commonly used output control valves include the pneumatic diaphragm, electromagnetic poppet/plunger valve, and proportional valve
• 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
  • Target variable
  • Cycle variable
• Trigger variable


  The variable that initiates inspiration, can be time triggering, pressure triggering, or flow triggering
• 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
• Cycle variable


  The variable that is measured and used to end inspiration, can be pressure, volume, flow, or time
• Baseline variable


  The parameter controlled during expiration, pressure control is the most practical and is implemented by all modern ventilators
• To understand ventilator-patient interaction, output waveforms must be examined, the output waveforms of interest during ventilatory support are pressure, volume, and flow