Basic modes of mv
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This document discusses different modes of mechanical ventilation. It begins by introducing mechanical ventilation and its purpose of providing respiratory support. It then describes the basic components of a ventilator and ventilator circuit. The document outlines several modes of mechanical ventilation including controlled mechanical ventilation, assist-control ventilation, intermittent mandatory ventilation, and synchronized intermittent mandatory ventilation. It provides details on the characteristics, advantages, and disadvantages of each mode.
Basic modes of mv
- 1. Basic Modes of Mechanical Ventilation Moderator : Dr. Vishal PRESENTED BY : Dr. Kumar Abhinav Dr. Anjali Sharma
- 2. INTRODUCTION Ventilators: are machines that generates a controlled flow of gas into a patient’s airways, Function: they provide Supportive role to buy time to the patient.
- 3. •Mechanical ventilation forms a mainstay of critical care in patients with respiratory insufficiency. •Ventilator must generate inspiratory flow to deliver tidal volume. •Transairway pressure (PTA) = PAO – PALV •PTA = 0, at the end of expiration and beginning of inspiration. •Mechanical ventilator produce either negative or positive pressure gradient.
- 4. Negative pressure ventilation •PTA gradient is created by decreasing PALV to below PAO, e.g.-Iron lungs •Disadvantages- poor patient access, bulky size, cost, dec. cardiac output (Tank shockshell OR Iron lungs).
- 5. Positive pressure ventilation •Achieved by applying positive pressure at airway opening which produces PTA gradient that generates inspiratory flow. •Inspiratory flow results in the delivery of tidal volume.
- 6. Parts of a Ventilator 1. Compressor 2. Control panel 3. Humidifier i. Simple humidifier ii. Servo-controlled humidifier with heated wire in the tubings 4. Breathing circuit
- 9. Ventilatory Phases • Inspiration: Inspiratory valve opens and expiratory valve is closed • Inspiratory pause: inspiratory valve and expiratory valve closed • Expiration: Inspiratory valve closed and expiratory valve open • Expiratory pause: Inspiratory valve and expiratory (or PEEP) valve closed at end of expiration
- 10. INDICATIONS OF MECHANICAL VENTILATION Indications are mainly clinical although objective lab parameters such as ABG can also be used to decide it:- Common indications include: 1. Respiratory Failure a. Apnea/Respiratory Arrest b. Inadequate ventilation c. Inadequate oxygenation d. Chronic respiratory insufficiency with failure to thrive.
- 11. 2. Cardiac Insufficiency/Shock a. Eliminate work of breathing b. Reduce oxygen consumption. 3. Neurologic dysfunction a. Central hypoventilation/frequent apnea b. Patient comatose, GCS (Glasgow Coma Score) < 8 c. Inability to protect airway.
- 12. Basic Ventilator Parameters •Tidal volume •FiO2 • Frequency • PIP • PEEP • Inspiratory Time • Expiratory time • I:E Ratio •Mode
- 13. Tidal volume:- tidal volume of 6 to 8 ml/kg can be set, or a particular flow rate and minute ventilation can be set to get a particular tidal volume. If the difference between inspired and expired TV >15% then circuit leak is suspected. FiO2:- Oxygenation can be improved either by increasing the inspired oxygen concentration (FiO2) or by different ventilator settings. 1. Increasing peak inspiratory pressure (PIP) 2. Increasing inspiratory/expiratory ratio 3. Applying a positive pressure before the end of expiration (PEEP).
- 14. Frequency:- Respiratory rate, together with tidal volume, determines the minute ventilation. High ventilator rates employ a lower tidal volume and therefore lower inspiratory pressures (PIP) are used to prevent barotrauma. PIP:- major factor in determining tidal volume . It is adjusted to produce adequate chest expansion and breath sounds. Can improve both oxygenation and ventilation.
- 15. Factors evaluated in determining PIP:- are the I. infant’s weight, II. gestational age (the degree of maturity), III. the type and severity of the disease and IV. lung mechanics - such as lung compliance and airway resistance.
- 16. Positive End Expiratory Pressure (PEEP) •It increases the end expiratory or baseline airway pressure greater than atmospheric pressure. •Used to treat refractory hypoxemia caused by intrapulmonary shunting. •It can be used in conjugation with other modes.
- 17. Physiology of PEEP PEEP Increases alveolar distending pressure Increases FRC by alveolar recruitment Improves ventilation Increases V/Q Improves oxygenation and Decreases work of breathing
- 18. Indications- •Refractory hypoxemia d/t intrapulmonary shunting. •Decreased FRC and lung compliance
- 19. Complications •Dec. venous return and cardiac output. Barotrauma •Increase ICP d/t impedance of venous return from head. •Alteration of renal function & water imbalance.
- 20. Ratio of Inspiratory Time to Expiratory time (I:E Ratio):- 1. Reversed I:E ratios, as high as 4:1 have been shown to result in improvement in oxygenation and decreases the incidence of BPD. 2. Extreme reversed I:E ratio with a short expiratory time will lead to air trapping and alveolar distention.
- 21. 3. In a case of lower airways obstruction (asthma, bronchiolitis) short IT and a longer expiratory time is used to avoid gas trapping and increased risk of air leaks.
- 22. Mode It is the interplay b/w patient and the ventilator. To describe a particular mode three things to be remembered. 1) Type of breath 2) Control variables 3) Phase variables
- 24. Phase variables • Trigger : ventilator (time)- triggered or patient (pressure or flow) triggered • Limit: flow-limited or pressure-limited • Cycling: volume, time, flow or pressure cycled
- 26. Phase variables: Trigger •What causes the breath to begin (signal to open the inspiratory valve) i. Machine (controlled): -the ventilator will trigger regular breaths at a frequency which will depend on the set respiratory rate, ie, they will be ventilator time triggered. ii. Patient (assisted):- If the patient does make an effort to breathe and the ventilator can sense it (by either sensing a negative inspiratory pressure or an inspiratory flow) and deliver a breath, it will be called a patient triggered breath.
- 27. Phase variables: Limit Factor which controls the inspiration inflow Flow Limited: a fixed flow rate and pattern is set and maintained throughout inspiration. i. An adequate tidal volume (Ti dependent) ii. Pressure will be variable (compliance and resistance dependent) Pressure limited: the pressure is not allowed to go above a preset limit. i. The tidal volume will be variable (compliance and resistance dependent)
- 28. Phase variables: Cycling Signal that stops the inspiration and starts the expiration. Volume Time Flow Pressure:- back-up form of cycling when the airway pressure reaches the set high-pressure alarm level.
- 29. Control variables Pressure: Pressure signal is the feedback signal (Pressure Preset) Volume: Volume signal is the feedback signal. Usually measure the flow and turn it into volume signal electronically. (volume preset) Time Flow
- 31. Advantage 1) less risk of barotrauma 2) decelerating flow pattern more effective in treating atelectatic lungs. Disadvantages 1) variable tidal volume delivery 2)risk of volutrauma
- 33. Advantage 1) less risk of volutrauma 2) More effective in no lung diseases states. Disadvantages 1) More risk of barotrauma
- 34. Basic Modes of Ventilation Controlled Mechanical Ventilation Assist Control Ventilation Intermittent Mandatory Ventilation Synchronized Intermittent Mandatory Ventilation Pressure Support
- 35. Controlled Mechanical Ventilation: Volume control •The ventilator delivers a preset TV at a specific R/R and inspiratory flow rate. •It is irrespective of patients’ respiratory efforts. •In between the ventilator delivered breaths the inspiratory valve is closed so patient doesn’t take additional breaths. •PIP developed depends on lung compliance and respiratory passage resistance.
- 37. Volume controlled CMV Indications- • Tetanus or other seizure activity • Crushed chest injury Disadvantages- • Asynchrony • Barotrauma d/t high PAW & dec. lung compliance • Haemodynamic disturbances • V/Q mismatch • Total dependence on ventilator
- 38. Pressure Controlled CMV •Ventilator gives pressure limited, time cycled breaths thus preset inspiratory pressure is maintained. •Decelerating flow pattern. •Peak airway/alveolar pressure is controlled but TV, minute volume & alveolar volume depends on lung compliance, airway resistance, R/R & I:E ratio.
- 39. PC- CMV
- 40. PC-CMV Advantages- •thus chances of barotrauma and hemodynamic disturbances are less. •Even distribution of gases in alveoli •In case of leakage, compensation for loss of ventilation is better as gaseous flow increases to maintain preset pressure.
- 41. Disadvantages- •Asynchrony •TV dec. if there is dec. lung compliance or inc. airway resistance, •thus causes hypoventilation and alveolar collapse. •V/Q mismatch
- 42. ASSIST-CONTROL MODE Ventilation (A-C Mode) •Ventilator assists patient’s initiated breath, but if not triggered, it will deliver preset TV at a preset respiratory rate (control). •Mandatory mechanical breaths may be either patient triggered (assist) or time triggered (control) •If R/R > preset rate, ventilator will assist, otherwise it will control the ventilation.
- 44. Advantages- •Dec. patients work of breathing. •Better patient ventilator synchrony. •Less V/Q mismatch. •Prevents disuse atrophy of diaphragmatic muscle. Disadvantages- •Alveolar hyperventilation •Development of high intrinsic PEEP in obstructed pts. •Increase mean airway pressure causes hemodynamic disturbances.
- 45. Intermittent Mandatory Ventilation (IMV) Ventilator delivers preset number of time cycled mandatory breaths & allows patient to breath spontaneously at any tidal volume in between. Advantages- •Lesser V/Q mismatch •Lesser hemodynamic disturbances
- 46. Disadvantage- •Breath stacking- lung volume and pressure could increase significantly, causing barotrauma. •More sedation needed.
- 47. Synchronized Intermittent Mandatory Ventilation (SIMV) •Ventilator delivers either assisted breaths to the patient at the beginning of a spontaneous breath or time triggered mandatory breaths. •Synchronization window- time interval just prior to time triggering. •Breath stacking is avoided as mandatory breaths are synchronized with spontaneous breaths. •In between mandatory breaths patient is allowed to take spontaneous breath at any TV.
- 49. SIMV It provides partial ventilatory support Advantages- •Maintain respiratory muscle strength and avoid atrophy. •Reduce V/Q mismatch d/t spontaneous ventilation. •Decreases mean airway pressure d/t lower PIP & inspiratory time •Facilitates weaning.
- 50. Disadvantages- •Desire to wean too rapidly results in high work of spontaneous breathing & muscle fatigue & thus weaning failure.
- 51. •Commonly applied to SIMV mode during spontaneous ventilation to facilitate weaning With SIMV, PS- •Increase patient’s spontaneous tidal volume. •Dec. spontaneous respiratory rate. •Decreases work of breathing. •Addition of extrinsic PEEP to PS increases its efficacy.
- 52. SIMV (VC) -PS
- 53. Pressure Support Ventilation (PSV) •Supports spontaneous breathing of the patients. •Each inspiratory effort is augmented by ventilator at a preset level of inspiratory pressure. •Patient triggered, flow cycled and pressure controlled mode. •Decelerating flow pattern. •Applies pressure plateau to patient airway during spontaneus br. •Can be used in conjugation with spontaneous breathing in any ventilator mode.
- 54. Disadvantages- •Not suitable for patients with central apnea. (hypoventilation) •Development of high airway pressure. (hemodynamic distubances) •Hypoventilation, if inspiratory time is short.
- 55. Continuous Positive Airway Pressure (CPAP) •PEEP applied to airway of patient breathing spontaneously •Indications are similar to PEEP, to ensure patient must have adequate lung functions that can sustain eucapnic ventilation.
- 56. THANK YOU