Mechanical ventlation
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The document outlines the principles, goals, and indications for mechanical ventilation, including methods of invasive and non-invasive ventilation. It details various ventilator settings, modes of operation, and complications associated with mechanical ventilation. Additionally, the document provides information on weaning criteria and procedures for patients requiring respiratory support.
Mechanical ventlation
- 1. Mechanical Ventilation Dr. Abhijit Diwate (Associate Professor) Cardio-Vascular & Respiratory PT DVVPF College of Physiotherapy, Ahmednagar 414111
- 2. Objectives Indications Goals Physiology of breathing Principles of mechanical ventilation modes of ventilators Settings of ventilators Ventilator complications Weaning criteria
- 3. Indications Acute Respiratory Failure Hypoxemia Neuromuscular Disorders Pulmonary edema Over Sedation reduce ICP stabilize the chest wall Aspiration ARDS Pulmonary embolism
- 4. Goals Increase efficiency of breathing Increase oxygenation Improve ventilation/perfusion relationships Decrease work of breathing
- 5. PHYSIOLOGY OF NORMAL BREATHING V/S MECHANICAL VENTILATION Normal breathing 1. Breathing by muscles is governed by requirement of body. 2. Initiation and termination of breathing depend on levels of PO2, PCO2, PH and lung inflation. 3. Air gets sucked in because of negative intra pleural pressure created by the respiratory muscles 4. Increase in pulmonary pressures are in the range of 3to 5cms. Of water. 5. Venous return increases during respiration 6. Expiration is passive.
- 6. Mechanical ventilation 1 work of the respiratory muscles is done by ventilator 2 Initiation, termination may be machine determined (mandatory breath) or patient determined (spontaneous breath). 3 Air is pushed in by positive pressure given by the ventilator. 4 Pressures generated are in the range of 15 to 40cms of water 5 Venous return decreases during respiration 6 Expiration is passive
- 7. PRINCIPLES OF MECHANICAL VENTILATION A ventilator is a machine that generates the pressure necessary to cause a flow of gas that increases the volume of the lungs. The three variables involved are - Pressure - Volume - Flow - One can be fixed or pre determined and the other two will depend on the compliance of the lungs and the chest wall and the resistance offered by the airways.
- 8. Mechanical Ventilation Non Invasive: Ventilatory support that is given without establishing endo- tracheal intubation or tracheostomy is called Non invasive mechanical ventilation Invasive: Ventilatory support that is given through endo-tracheal intubation or tracheostomy is called as Invasive mechanical ventilation Non Invasive Invasive
- 9. NON INVASIVE Negative pressure Producing Neg. pressure intermittently in the pleural space/ around the thoracic cage Positive pressure Delivering air/gas with positive pressure to the airway
- 10. Invasive Positive Pressure Pressure cycle Volume cycle Time cycle
- 11. Positive Pressure Ventilators Pressure Cycled A pre determined and preset pressure terminates inspiration. Pressure is constant and volume is variable. Small, portable, inexpensive Ventilation volume can vary with changes in airway resistance, pulmonary compliance Used for short-term support of patients with no pre- existing thoracic or pulmonary problems
- 12. Positive Pressure Ventilators Volume cycled Most widely used system A pre determined and preset volume -on completion of its delivery , terminates the inspiration. Pressure is variable and volume is constant Delivers volume at whatever pressure is required up to specified peak pressure May produce dangerously high intrathoracic pressures
- 13. Positive Pressure Ventilators Time cycled Delivers air/gas over a set time (Insp. Time) after which the inspiration ends. Volume determined by Length of inspiratory time Pressure limit set Patient airway resistance Patient lung compliance Common in neonatal units
- 17. Controlled Mechanical Ventilation Patient does not participate in ventilations Machine initiates inspiration, does work of breathing, controls tidal volume and rate Useful in apneic or heavily sedated patients Useful when inspiratory effort contraindicated (flail chest) Patient must be incapable of initiating breaths Rarely used
- 18. Assist/Control (A/C) Patient triggers machine to deliver breaths but machine has preset backup rate Patient initiates breath--machine delivers tidal volume If patient does not breathe fast enough, machine takes over at preset rate Tachypneic patients may hyperventilate dangerously
- 19. Assist Mode Intermittent Mandatory Ventilation (IMV) Patient breathes on own Machine delivers breaths at preset intervals Patient determines tidal volume of spontaneous breaths Used to “wean” patients from ventilators Patients with weak respiratory muscles may tire from breathing against machine’s resistance
- 20. Assist Mode Synchronized Intermittent Mandatory Ventilation (SIMV) Similar to IMV Machine timed to delay ventilations until end of spontaneous patient breaths Avoids over-distension of lungs Decreases barotrauma risk
- 21. Positive End Expiratory Pressure (PEEP) Positive pressure in airway throughout expiration Holds alveoli open Improves ventilation/perfusion match Decreases FiO2 needed to correct hypoxemia Useful in maintaining pulmonary function in non- cardiogenic pulmonary edema, especially ARDS
- 22. Positive End Expiratory Pressure (PEEP) High intrathoracic pressures can cause decreased venous return and decreased cardiac output May produce pulmonary barotrauma May worsen air-trapping in obstructive pulmonary disease DANGERS
- 23. Continuous Positive Airway Pressure (CPAP) PEEP without preset ventilator rate or volume Physiologically similar to PEEP May be applied with or without use of a ventilator or artificial airway Requires patient to be breathing spontaneously Does not require a ventilator but can be performed with some ventilators
- 24. Noninvasive pressure support ventilation Bi-level positive airway pressure ventilation Set level of inspiratory positive airway pressure and expiratory positive airway pressure Flow triggered system Applied through nasal mask Tidal vol., flow rate, insp. Time vary with pt. effort, set pressure and changes in compliance and resistant
- 25. Pressure control Pressure control with inverse inspiratory to expiratory ratio ventilation
- 26. High Frequency Ventilation (HFV) Small volumes, high rates Allows gas exchange at low peak pressures
- 27. High Frequency Ventilation (HFV) Useful in managing: Tracheobronchial or bronchopleural fistulas Severe obstructive airway disease Patients who develop barotrauma or decreased cardiac output with more conventional methods Patients with head trauma who develop increased ICP with conventional methods Patients under general anesthesia in whom ventilator movement would be undesirable
- 28. Ventilator Settings Tidal volume--10 to 15ml/kg (std = 12 ml/kg) Respiratory rate--initially 10 to 16/minute FiO2--0.21 to 1.0 depending on disease process 100% causes oxygen toxicity and atelectasis in less than 24 hours 40% is safe indefinitely PEEP can be added to stay below 40% Goal is to achieve a PaO2 >60 I:E Ratio--1:2 is good starting point Obstructive disease requires longer expirations Restrictive disease requires longer inspirations
- 29. Ventilator Settings Ancillary adjustments Inspiratory flow time Temperature adjustments Humidity Trigger sensitivity Peak airway pressure limits Sighs
- 30. Ventilator Complications Mechanical malfunction Keep all alarms activated at all times If malfunction occurs, disconnect ventilator and ventilate manually
- 31. Ventilator Complications Airway malfunction Suction patient as needed Keep condensation build-up out of connecting tubes Auscultate chest frequently End tidal CO2 monitoring Maintain desired end-tidal CO2 Assess tube placement
- 32. Ventilator Complications Pulmonary barotrauma Avoid high-pressure settings for high-risk patients (COPD) Monitor for pneumothorax Anticipate need to decompress tension pneumothorax
- 33. Ventilator Complications Hemodynamic alterations Decreased cardiac output, decreased venous return Observe for: Decreased BP Restlessness, decreased LOC Decreased urine output Decreased peripheral pulses Slow capillary refill Pallor Increasing Tachycardia
- 34. Ventilator Complications Renal malfunction Gastric hemorrhage Pulmonary atelectasis Infection Oxygen toxicity Loss of respiratory muscle tone
- 35. Weaning Is the cause of respiratory failure gone or getting better ? Is the patient well oxygenated and ventilated ? Can the heart tolerate the increased work of breathing ?
- 36. Weaning Criteria Clinical assessment Investigation Mode and parameter change CPAP Venturi
- 37. Physiological parameters Ventilatory pump TV > 5ml/kg body wt. RR </= 30 Driving force Pressure inspiratory = -20 to -30 mm of Hg Compliance <25 ml/ cm H2O Breathing pattern – synchronous stable WOB – near to normal Oxygen status PaO2 > 60 mm of Hg Carbondioxide PaCO2 < 50 mm Hg
- 38. WEANING PROCEDURE T- tube trials SIMV Pressure support
- 39. Summary Indications Goals Physiology of breathing Principles of mechanical ventilation modes of ventilators Settings of ventilators Ventilator complications Weaning criteria
- 40. QUESTIONS 1. WRITE THE INDICATIONS AND GOALS OF MECHANICAL VENTILATION. 5MARKS 2. WRITE THE PRINCIPLES OF MECHANICAL VENTILATIONS. 3 MERKS