Published on

Published in: Health & Medicine
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide


  2. 2. BREATHING Breathing: It is taking air in (inspiration) and out of your lungs (expiration). It can be consciously controlled (voluntary action) Breathing involves two stages — ventilation and gas exchange. Ventilation is the movement of air in and out of lungs and gas exchange is the absorption of oxygen from the lungs and release of carbon dioxide.
  3. 3. Respiration is a process where the body breaks down the oxygen, so that the cells in the body can use it . Therefore ,Breathing is a physical process and respiration is a chemical process
  4. 4. NORMAL MECHANICS OF SPONTANEOUS VENTILATION AND RESPIRATION Spontaneous breathing or spontaneous ventilation is simply the movement of air into and out of the lungs.The main purpose of ventilation is to bring in fresh air, for gas exchange into the lungs and to allow the exhalation of air that contains CO2.
  5. 5. RESPIRATION  It is defined as movement of gas molecules across a membrane. EXTERNAL RESPIRATION is movement of O2 from the lungs into bloodstream and of CO2 from bloodstream into alveoli. INTERNAL RESPIRATION is movement of CO2 from the cells into the blood and movement of O2 from the blood into cells.
  6. 6. Normal inspiration is accomplished by the expansion of thorax or chest cavity. It occurs when the muscles of inspiration contract. During contraction , the diaphragm descends and enlarges the vertical size of thoracic cavity. The external intercostal muscles contract and raise the ribs slightly, increasing the circumference of thorax. The activities of these muscles represent the “work” required to inspire.
  7. 7.  Normal exhalation is passive and does not require any work. During normal exhalation, the muscles relax, the diaphragm moves upward to its resting position, and the ribs return to their normal position. The volume of thoracic cavity decreases, and air is forced out of alveoli. INSPIRATION EXPIRATION
  8. 8. BASIC PHYSIOLOGY -  Negative pressure circuit - Gradient between mouth and pleural space is the driving pressure - need to overcome resistance - maintain alveolus open • overcome elastic recoil forces - Balance between elastic recoil of chest wall and the lung=FRC
  10. 10. VENTILATION  Ventilation is the process by which Oxygen and CO2 are transported to and from the lungs.  Pulmonary ventilation  Alveolar ventilation
  11. 11. GAS FLOW AND PRESSURE GRADIENTS DURING VENTILATION Basic concept of Air flow is that, for air to flow through a tube or airway, pressure at one end must be higher than the pressure at the other end. Air always flows from the high pressure point to the low pressure point (pressure gradient). The conductive airway begins at the mouth & nose, and ends at the small airways near the alveoli. Therefore, gas flows into the lungs, when the pressure in the alveoli is lower than the pressure at the mouth and nose.
  12. 12. Conversely, gas flows out of lungs, when the pressure in the alveoli is greater than the pressure at the mouth and nose.  When the pressure at the mouth and alveoli are same, as occurs at the end of inspiration or the end of expiration, then no gas flow occurs as there is no pressure gradient.
  13. 13. DEFINITION OF PRESSURES AND GRADIENTS IN THE LUNGS Airway opening pressure (Paw)/ Mouth pressure(PM) is often called airway pressure (Paw). Unless pressure is applied to mouth or nose, Paw is Zero (atmospheric). Body surface pressure (Pbs) is the pressure at body surface . This is equal to Zero unless the person is using a pressurized chamber or a negative pressure.
  14. 14. Ppl = Intrapleural pressure; pressure in the intrapleural space ; generally negative because the lungs are “naturally” smaller than the chest wall; the negative pressure helps to keep the airways open and helps the lungs from collapsing. Palv = Intra-alveolar pressure; pressure within the alveoli; positive on expiration, negative on inspiration, and zero (same as atmospheric) when there no air movement.
  15. 15. Four basic pressure gradients are used to describe normal ventilation: 1.Trans-Airway pressure (PTA): It is the pressure gradient between the air opening and the alveolus 2. Trans-Thoracic pressure(Pw or Pt): It is the pressure difference between the alveolar space(lung) and the Body surface. Pw = PA - Pbs (Pw represents the pressure needed to expand or contract the lungs and the chest wall at the same time.)
  16. 16. 3. 3.Trans-Pulmonary pressure (PL or PTP )/Trans-Alveolar pressure It is the pressure difference between the alveolus and the pleural space. PL = PA - Ppl 4. Trans - respiratiory pressure (PTR ): It is the pressure gradient between airway opening and the body surface PTR = Paw - Pbs
  17. 17. D During normal spontaneous inspiration, as the volume of thoracic space increases, the intrapleural pressure becomes more negative in relation to atmospheric pressure . This negative intrapleural pressure goes from -5cm H2O at end expiration to -10cm H2O at end inspiration. The negative intrapleural pressure is transmited to the alveolar space.
  18. 18. VENTILATION PARAMETERS A. Lung Volumes 1. Basic volumes: a. Tidal Volume (VT, TV): volume of gas exchanged each breath; can change as ventilation pattern changes .(500 ml) b. Inspiratory Reserve Volume (IRV): maximum volume that can be inspired, starting from the end inspiratory position (potential volume increase at the end of inspiration).(3000ml) c. Expiratory Reserve Volume (ERV): maximum volume that can be expired, starting from the end expiratory position (potential volume decrease at the end of expiration)(1200ml) d. Residual Volume (RV): volume remaining in the lungs and airways following a maximum expiratory effort (1300 ml)
  19. 19. 2. Capacities:combined volumes a. Vital Capacity (VC): maximum volume of gas that can be exchanged in a single breath VC = TV + IRV + ERV (4700 ml) b. Total Lung Capacity (TLC): maximum volume of gas that the lungs(and airways) can contain TLC = VC + RV = TV + IRV + ERV + RV (6000 ml) c. Functional Residual Capacity (FRC): volume of gas remaining in the lungs (and airways) at the end expiratory position FRC = RV + ERV (2500 ml) d. Inspiratory capacity (IC): maximum volume of gas that can be inspired from the end expiratory position . IC = TV + IRV (3500 ml)
  20. 20. 3. Measurement of volumes: Spirometery
  21. 21. Ventilation 1. Frequency /Respiration rate (f or RR): breaths per unit time. At rest: 12/min 2. Ventilation rate: total volume inspired or expired per unit time ; sometimes called Minute Volume (MV) when measured per minute; to avoid ambiguity, usually measured as volume expired, VE’ MV or VE’ = f × TV , At rest= 12/min × 0.5L = 6 L/min
  22. 22. A a. Peak velocity (e.g. peak expired flow rate) normal value 400-600 liters/minute b. Timed vital capacity: volume of gas that can be expired from the lungs with maximum effort in a given time . 1) Usually expressed as a fraction of the total volume expired in a maximum effort, the Forced Vital Capacity (FVC) 2) Normal value of FEV1 / FVC ≥ 80%
  23. 23. DEFINITION Mechanical ventilation is a positive or negative pressure artificial breathing device that can maintain ventilation and oxygen delivery for prolonged periods. (It is indicated when the patient is unable to maintain safe levels of oxygen or CO2 by spontaneous breathing even with the assistance of other oxygen delivery devices)
  24. 24. HISTORY OF MECHANICAL VENTILATION • The Roman physician Galen may have been the first to describe mechanical ventilation. • In 1908 George Poe demonstrated his mechanical respirator by asphyxiating dogs and seemingly bringing them back to life.
  25. 25. ORIGINS OF MECHANICAL VENTILATION Negative-pressure ventilators (“iron lungs”) •Non-invasive ventilation first used in Boston Children’s Hospital in 1928 •Used extensively during polio outbreaks in 1940s – 1950s •Positive-pressure ventilators •Invasive ventilation first used at Mass achusetts General Hospital in 1955 •Now the modern standard of mechanical ventilation Iron lung polio ward at Rancho Los Amigos Hospital in 1953.
  26. 26. MECHANICAL VENTILATION • Ventilator delivers gas to lungs using positive pressure at certain rate. • The amount of gas delivered can be limited by time, pressure , volume. • The duration can be cycled by time , pressure and flow.
  28. 28. 1.Pressure controller: The ventilator maintains the same pressure waveform, at the mouth regardless of changes in lung characteristics. 2. Flow controller: Ventilator volume delivery and volume waveform remain constant and are not affected by changes in lung characteristics. Flow is measured 3. Volume controller: Ventilator volume delivery and volume waveform remain constant and are not affected by changes in lung characteristics. Volume is measured 4.Time controller: Pressure, volume, and flow curves can change as lung characteristics change. Time remains constant.
  30. 30. 1.INITATION OF INSPIRATION TRIGGERING This is how inspiration is initiated in association with patients breath. It can be by changes in time, flow or pressure TIME TRIGGERING : The rate of breathing is controlled by the ventilator. The breath is controlled or mandatory. The patient cannot obtain air from the machine. PATIENT– TRIGGERING When pressure is the trigger , a decrease in the pressure within the inspiratory circuit is sensesd and inspiration begins. The sensitivity setting reflects the amount of pressure drop baseline pressure that the patient must develop in the ventilator circuit , on inspiration , to initate the flow of gas.
  31. 31. FLOW TRIGGERING: The ventilator delivers a constant background flow (flow by). Any change caused by patient effort is sensed by the flow sensor. A breath is delivered to the patient. This requires less work of breathing when compared to pressure triggering. 2. INSPIRATORY PHASE (Inspiration is timed from the beginning of inspiratory flow to the beginning of expiratory flow) A limit variable is the maximum value that a variable(pressure, volume, flow, or time) can attain. This limits the variable during inspiration but does not end the inspiratory phase.
  32. 32. 3.CHANGE OVER FROM INSPIRATION TO EXPIRATION (cycling) Of the four variables the ventilator can control to cycle out of inspiration ( i.e.pressure, time, volume, or flow), only one can operate at a given time. VOLUME-CYCLED VENTILATION The inspiratory phase of a volume-cycled breath is terminated when the set volume has been delivered. In most cases the volume remains constant even when lung characteristics change.  However, the pressures required to deliver the volume and gas flow vary, as compliance and resistance change.
  33. 33. TIME – CYCLED VENTILATION In this , the inspiration ends and expiration begins after a pre-determined time interval is reached. Cycling may be controlled by a simple timing mechanism or by setting the rate and adjusting the I:E ratio, or percentage of inspiratory time With time-cycled pressure ventilation, both volume and flow vary. Ex- IPPB FLOW-CYCLED VENTILATION With flow-cycled ventilation, the ventilator cycles into the expiratory phase once the flow has decreased to a predetermined value during inspiration. Volume,pressure,and time vary according to changes in lung characteristics. Flow cycling is the most common cycling mechanism in the pressure-support mode.Ex-PSV
  34. 34. PRESSURE-CYCLED VENTTIILLATTIION When a preset pressure threshold (limit) is reached at the mouth or upper airway, a ventilator set to pressure cycle ends inspiration. The exhalation valve opens, and expiratory flow begins. The volume delivered to the patient depends on the flow delivered, the duration of inspiration, lung characteristics, and the set pressure.
  35. 35. EXPIRATION The variable controlled during the expiratory time on the ventilator is known as the baseline variable. In all commonly used ventilator , pressure is the variable controlled during expiration. Exhalation occurs passively because of the elastic recoil of the lung, but patient passively exhales to a controlled baseline pressure . The end expiratory pressure when in equilibrium with atmospheric pressure ,is zero. A baseline pressure above atmospheric pressure is known as Positive end- expiratory pressure (PEEP)
  36. 36. INDICATIONS  Acute lung injury (including ARDS, trauma)  Apnea with respiratory arrest, including cases from intoxication  Chronic obstructive pulmonary diseas(COPD)  Acute respiratory acidosis with partial pressure of carbon dioxide (pCO2) > 50 mmHg and pH < 7.25, which may be due to paralysis of the diaphragm due to Guillain-Barré syndrome, Myasthenia Gravis, spinal cord injury, or the effect of anaesthetic and muscle relaxant drugs  Increased work of breathing as evidenced by significant tachypnea, and other physical signs of respiratory distress
  37. 37.  Hypotension including sepsis, shock, congestive heart failure  Neurological diseases such as Muscular Dystrophy and Amyotrophic Lateral Sclerosis.  Inefficiency of thoracic cage in generating pressure gradient necessary for ventilation (chest injury, thoracic malformation) Cardiac insufficiency (elimination WOB, reduce oxygen consumption)  Ventilatory failure or oxygenation failure due to 1. Increased airway resistance 2. Changes in lung compliance 3. Hypoventilation 4. V/Q mismatch 5. Intrapulmonary shunting 6. diffusion defect
  38. 38. Disorders of Pulmonary Gas Exchange 1. Acute respiratory failure 2. Chronic respiratory failure 3. Hypoxemia( not responding to supplemental oxygen and fluid resuscitation) 4. Acute hypercapnia ( with worsening acidosis) 5. Pulmonary disease resulting in diffusion abnormality 6. Pulmonary diseases resulting in ventilation-perfusion mismatch
  39. 39. UNDERLYING PHYSIOLOGICAL PRINCIPLES GUIDING MECHANICAL VENTILATION o Control of CO2 elimination o Improved impaired oxygenation o Assist respiratory muscles FACTORS AFFECTING VENTILATION 1.Compilance 2. Resistance 3. Time constants for lung elasticity 4. Work of breathing
  40. 40. LUNG COMPLIANCE  It is the change in volume per unit change in pressure  Types: • Static compliance= Exhaled tidal volume Plateau pressure-PEEP • Dynamic compliance = Exhaled tidal volume Peak inspiratory pressure-PEEP
  41. 41. STATIC COMPLIANCE- is measured when there is no air flow. • Reflects the elastic properties of the lung and the chest wall. DYNAMIC COMPLIANCE -is measured when air flow is present. • Reflects the airway resistance (non elastic resistance) and elastic properties of lung and chest wall  Low lung compliance increases the work of breathing.  High compliance – exhalation is often incomplete due to lack of elastic recoil by the lungs.
  42. 42. AIRWAY RESISTANCE I It is defined as airflow obstruction in the airways. Normal airway resistance is between 0.6 and 2.4 cm H2o/l/sec at a flow rate of 30 l/min.  Airway resistance varies directly with the length & inversely with diameter of ET Calculated by Raw= pressure change/flow Increase in airway resistance is equal to increase in work of breathing.
  43. 43. TIME CONSTANTS I It is product of compilance and resistance. The time constant is the time required, in seconds , to inflate a lung region to 60% of its filling, if the filling pressure was to remain constants. Areas of the lung that have either increased resistance or decreased compilance will have a longer time constants.
  44. 44. WORK OF BREATHING The total work of breathing (WOB) is the sum of physiologic work plus the work imposed by the breathing appratus . The work that the respiratory muscles must perform to expand the lung is that which will overcome elastic and non elastic forces : compilance & resistance respectively. When compilance decreases/ resistance increases a greater force is required to move volume in the lung . That is WOB increases.
  45. 45. VENTILATOR CONTROLS/PARAMETERS: 1. Fraction of Inspired Oxygen (FiO2): Amount of oxygen delivered to the patient. Adjusted to maintain O2 sat of > 90%. Concern with oxygen toxicity with FiO2 > 60% required for 12-24 hours. 2. Respiratory Rate: Number of breaths/min. ventilator is to deliver 3. Tidal Volume: Amount of air delivered with each ventilator breath, usually set at 6-8 ml/kg. 4. Sigh: Ventilator breath with greater volume than preset tidal volume, used to prevent atelectasis,however not always used.
  46. 46. 5. Pressure limit: Limits highest pressure allowed by ventilator. 6. Positive End Expiratory Pressure (PEEP): Pressure maintained in lungs at end of expiration used to improve oxygenation by opening collapsed alveoli, improving ventilation/perfusion, increasing oxygenation; can be used to reduce FiO2. 7. Adjuncts to Mechanical Ventilation PEEP, CPAP, PSV 8. Alarms ventilator alarms must never be ignored or disarmed!!!!
  47. 47. 9. Peak Inspiratory Pressure: Peak pressure registered on the airway pressure gauge during normal ventilation; PIP value used to set high and low pressure alarms; increased PIP may indicate decreased lung compliance or increased lung resistance. 10. Minute Volume or Minute Ventilation (Ve): Respiratory rate times the tidal volume. RR x vt = Ve Normal minute volume for adults is 5-10 liters 11. Ventilatory Mode CMV, IMV, SIMV, A/C, PCV
  48. 48. Power Electrical failure alarms are a must for all ventilators 12. Frequency Alarms if RR goes above or below set levels 13. Volume Volumes go above or below preset levels (i.e. VT/ minute volume) 14. Pressure Change in inspiratory or peak airway pressure above or below preset limits
  49. 49. Mechanical ventilation BREATHS TYPES DESCRIPTION MACHINE -CYCLED MANDATORY A breath that is triggered , limited & BREATH cycled by ventilator . Ventilator performs all of the work of breathing throught the the phases of ventilation ASSISTED A breath that is triggered by the patient , BREATH then limited & cycled by the ventilator
  50. 50. PATIENT – CYCLED SUPPORTED A breath that is triggered by the patient, BREATH limited by the ventilator and cycled by patient. A spontaneous breath with an inspiratory pressure greater than baseline. SPONTANEOUS A breath that is triggered , limited and BREATH cycled by the patient . The patient performs all of the work of ventilation
  51. 51. FULL VERSES PARTIAL VENTILATOR SUPPORT Ventilatory support can be classified according to two general approches: 1. FULL VENTILATORY SUPPORT (FVS)  It constitutes mechanical ventilation in which the ventilator performs all of the WOB without any contribution from the patient.  The ventilator alone provides the minute volume of gases required to satisfy the patient’s respiratory needs. 2. PARTIAL VENTILATORY SUPPORT(PVS)  PVS occurs when both the ventilation and the patient contribute toward the WOB and meeting the minute volume of gases required to satisfy respiratory needs.  The advantages of PVS include allowing the patient to respond to increase in CO2 by increasing VE and promiting use of the respiratory muscles , thereby preventing disuse atrophy.
  53. 53. POSITIVE PRESSURE VENTILATORS Volume-cycled • terminate inspiration after delivering a preset volume of gas • delivered regardless of required pressure to do so • volume remains the same unless high peak pressures reached Pressure-cycled • terminate inspiration when a preset pressure is reached • varying degrees of resistance will interfere with gas flow • best used with drug overdose patients • not good for post- operative or severe respiratory infections
  55. 55. NEGATIVE PRESSURE VENTILATORS They exert a negative pressure on the external chest wall. This causes decreasing the intrathoracic pressure during inspiration which allows air to flow into the lungs, filling its volume. Physiologically this type of assisted ventilation is similar to spontaneous breathing. USES 1. It is used mainly in chronic respiratory failure associated with neuromuscular conditions such as poliomyelitis, muscular dystrophy, amyotrophic lateral sclerosis and myasthenia gravis. 2. Not used for serious patients 3. Simple to use 4. Do not require intubation 5. Adaptable for home use EXAMPLES Iron lung, body wrap and chest cuirass
  56. 56. COMPLICATIONS WITH NEGATIVE PRESSURE VENTILATION Limited access for patient care. Inability to properly monitor pulmonary mechanics. Patient discomfort.
  57. 57. IRON LUNG • Encloses patients body except for the head and neck in a tank and the air in it is evacuated to produce a negative pressure around the chest. • This negative pressure surrounding the chest & underlying alveoli results in chest wall and alveolar expansion. • The tidal volume delivered to the patient is directly related to the negative presssure gradient.
  58. 58. IRON LUNG CIRCA 1950’s
  60. 60. CHEST CUIRASS • It is a form of negative pressure ventilation that was intended to alleviate the problems of patient acess & TANK SHOCK associated with iron lungs. • It covers only the patient’s chest and leaves the arms and lower body exposed. • To overcome the problem of air leakage, individually designed cuirass minimise air leaks, & they have been used successfully to ventilate patients with chest wall diseases such as scoliosis
  62. 62. POSITIVE PRESSURE VENTILATORS Positive pressure ventilators inflate the lungs by exerting positive pressure on the airway, forcing the alveoli to expand during inspiration. Exhalation is passive. Endotracheal intubation or tracheotomy is necessary in most cases. There are three types of positive pressure ventilators, which are classified by the method of ending the inspiratory phase of respiration: 1. Pressure cycled Ventilators 2. Time Cycled ventilators 3. Volume Cycled Ventilators 4. Non-invasive positive pressure ventilator
  63. 63. NONINVASIVE POSITIVE -PRESSURE VENTILATION Positive pressure ventilation can be given via face mask that covers the nose and the mouth, nasal masks or other nasal devices. Ventilation can be delivered by volume ventilator, pressure controlled ventilator, continuous positive pressure device or bi- level positive pressure ventilator. The most comfortable mode for the patient is pressure controlled ventilation with pressure support. This eases the work of breathing and enhances the gas Exchange.
  64. 64. Indications for NIPPV 1. Acute or chronic respiratory failure 2. Acute pulmonary edema 3. COPD 4. Chronic congestive heart failure with a sleep rated breathing disorder 5. Obstructed sleep apnea Contraindications 1. Hemodyanamically unstable 2.Respiratory arrest 3. Inability to protect airway 4. Excessive secrections 5. Unco-operative patients 6. Patients with facial odema , trauma, burns.
  65. 65. Operating modes • Spontaneous • Positive end expiratory pressure (PEEP) • Continuous positive airway pressure (CPAP) • Bilevel positive airway pressure (BiPAP) • Controlled mandatory ventilation (CMV) • Assist control (AC) • Intermittent mandatory ventilation (IMV) • Synchronized intermittent mandatory ventilation (SIMV) • Mandatory minute ventilation (MMV)
  66. 66. • Pressure support ventilation (PSV) • Adaptive support ventilation (ASV) • Proportional assist ventilation (PAV) • Volume assured pressure support (VAPS) • Pressure regulated volume control (PRVC) • Volume ventilation plus (VV+) • Pressure control ventilation (PCV) • Airway pressure release ventilation • Inverse ratio ventilation (IRV) • Automatic tube compensation (ATC)
  67. 67. Spontaneous ventilation A ir w a y p r e s s u r e • Is not an actual mode on the ventilator since the rate and tidal volume are determined by the patient • It provides inspiratory flow to the patient in a timely manner • Used with adjunctive modes like PEEP
  68. 68. Positive End Expiratory Pressure (PEEP) • PEEP is positive pressure that is applied by the ventilator at the end of expiration. • This mode does not deliver breaths, but is used as an adjunct to CV, A/C, and SIMV to improve oxygenation by opening collapsed alveoli at the end of expiration.
  69. 69. ADVANTAGES •Improves oxygenation by increasing FRC •Decreases physiological shunting •Improved oxygenation will allow the Fio2 to be lowered •Increased lung compliance DISADVANTAGES •Increased incidence of pulmonary brotrauma •Potential decrease in venous return •Increased work of breathing •Increased intracranial pressure Complications from the increased pressure can include decreased cardiac output, pneumothorax, and increased intracranial pressure.
  70. 70. BIPAP This offers independent control of inspiratory and expiratory pressures while providing pressure support ventilation. Can be used as a Cpap device by setting IPAP and EPAP at the same level ADVANTAGES It is provided via a nasal or oral mask, nasal pillow, or mouthpiece with a tight seal with a portable ventilator. INDICATION It is most often used for patients who require ventilator assistance at night, such as patients with severe COPD or sleep apnea.
  71. 71. CONTINUOUS POSITIVE AIRWAY PRESSURE (CPAP) It is simply a spontaneous breath mode, with the baseline pressure elevated above zero. Advantages Improves oxygenation by increasing FRC Decreases physiological shunting Improved oxygenation will allow the Fio2 to be lowered Increased lung compliance Disadvantages Increased incidence of pulmonary brotrauma Potential decrease in venous return Increased work of breathing Increased intracranial pressure
  72. 72. Air leaks Pressure lesion on the skin Irritation of eyes Gastric distention Facial pain INDICATION •Where FRC is increased (ARDS, Pneumonia, lung collapse) •Improved V/Q mismatch •In post operative patients & In ARDS premature infants (to treat HYPOXIA) • If patient breath spontaneously helps to maintain airway patency CONTRAINDICATION -Surgical emphysema -Bullae -Undrained pneumothorax - Excessive secrections
  73. 73. CONTROLLED MANDATORY VENTILATION (CMV) • Patient has no control over ventilation • Breaths are delivered at a rate and volume that are deterimned by adjusting ventilator , regardless of patient’s attempts to breath(i.e. controls both the tidal volume and respiratory rate of the patient). • Should only be used with a combination of sedatives, respiratory depressants and neuromuscular blockers. INDICATION • Patients fighting or bucking the ventilator ,means the patient is severely distressed and vigrously struggling to breathe. • Teatnus or seizure activites • Complete rest for the patient for 24 hrs
  74. 74. • Crushed chest injury patients (in whom paradoxical chest wall movement produced due to spontaneous inspiratory efforts) • Where complete control is mandatory (i.e. undergoing surgery) • Patient who are unable to breath at all (GBS, Anaesthetic patient)
  75. 75. ADVANTAGES • Rests muscles of respiration DISADVANTAGES • Heavy sedation is required • More haemodynamic depression • Risk of intrinsic PEEP is significant • Patient does not like to be controlled (uncomfortable) COMPLICATIONS • Disconnection or ventilator fails to operate is a primary hazard- in a sedated or apneic patient is the potential for apnea and hypoxia.
  76. 76. Assist/Control Mode •Control Mode • Pt receives a set number of breaths and cannot breathe between ventilator breaths • Similar to Pressure Control •Assist Mode • Pt initiates all breaths, but ventilator cycles in at initiation to give a preset tidal volume • Pt controls rate but always receives a full machine breath •Assist/Control Mode • Assist mode unless pt’s respiratory rate falls below preset value • Ventilator then switches to control mode • Rapidly breathing pts can overventilate and induce severe respiratory alkalosis and hyperinflation (auto-PEEP) Ventilator delivers a fixed volume
  77. 77. ADVANTAGES Small WOB Guarantee minute ventilation allows control over RR DISADVANTAGES In a trachypneic patient > lead to over ventilaton and severe respiratory alkalosis>> Hyperinflation . INDICATION Heavy sedation Paralysis
  78. 78. INTERMITENT MANDATORY VENTILATION (IMV) •Allows patient to breathe spontaneously through ventilator circuitry. • In between the mandated breaths, the patient is free to breath at his desired respiratory rate. ADVANTAGE 1. Between the mandatory breaths the patient is free to choose his own respiratory rate, tidal volume and flow rate. 2. The mandatory breath is delivered in synchrony with patient effort, making for comfortable breathing. 3. The patients’ respiratory muscles are active and so disuse atrophy is less common. 4.Facilitates weaning
  79. 79. DISADVANTAGES 1. Hypoventilation is possible if the mandatory breath rate is not set high enough. 2. Work of breathing may be high, if trigger-sensitivity and flow rate are inappropriate to patients needs. 3. Excessive work of breathing may occur during the spontaneous breaths unless an adequate level of pressure support is added. INDICATION •Normal respiratory drive but respiratory muscles unable to perform all WOB •In maintaining normal PaCO2 •Weaning from mechanical ventilation
  80. 80. SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION(SIMV)  The ventilator attempts to synchronize the set number mandatory breaths with the patients respiratory efforts  The ventilator waits for a patient effort during a sensitive peroid before every breath. INDICATION: -In weaning - Initially after full ventilatory support to partial ventilatory support - Heavy sedation & paralysis CONTRAINDICATION- Respiratory muscles fatigue
  81. 81. ADVANTAGES • Prevention of respiratory muscles atrophy • Decreased requirement of sedation • Lower mean airway pressure DISADVANTAGES • Respiratory muscles fatigue • Increased risk of CO2 rentation • Increased WOB
  82. 82. MANDATORY MINUTE VENTILATION (MMV) •It is a mode where the patient breathe spontaneously, yet a constant minute ventilation (VE) is guaranteed. •If the patient’s spontaneous ventilation does not match the target VE , the ventilator provides whatever part of the VE the patient does not achieve. INDICATION To prevent hypercapnia To prevent hypoventilation & respiratory acidosis Apneic patient
  83. 83. ADVANTAGES Better patient – ventilator interaction Less hemodynamic effects DISADVANTAGES Higher work of breathing than CMV, AC Risk of lung injury due to high peak airway pressures
  84. 84. PRESSURE SUPPORT VENTILATION The pressure support ventilation is patient-triggered, flow cycled, pressure supported mode where each inspiratory effort of the patient is augmented by the ventilator at a preset level of inspiratory pressure. Pressure support may be used independently as a ventilator mode or used in conjunction with CPAP or SIMV. Advantages 1. Maximizing patient control of respiration, thereby enhancing patient comfort on the ventilator. 2. Increase the patient’s spontaneous tidal volume 3. Decrease the patient’s spontaneous respiratory rate 4. Decrease work of breathing 5. Providing alternative mode of weaning from mechanical ventilation
  85. 85. Disadvantages 1. PSV is not used as a sole ventilator support during acute respiratory failure because of the risk of hypoventilation. 2. Not suitable for the management of patient with central apnea. 3. Developed of atelactasis due to smaller tidal volume in patients with brief inspiratory times and high respiratory impedance. 4.Requires spontaneous respiratory effort 5.Delivered volumes affected by changes incompliance Indication Patient who don’t have sufficient capacity (i.e. SIMV mode) To faciliatate weaning Contraindication If patient needs mandatory breaths
  86. 86. PRESSURE CONTROL VENTILATION(PCV) Pressure - controlled breaths are time triggered , pressure limited, time cycled Advantages Can minimize the peak inspiratory pressure while still maintaining adequate PaO2 & PaCO2. Decreased mean airway pressure Control frequency Disadvantages Requires sedation or paralysis Ventilation does not change in response to clinical changing needs Indication- Sedation
  87. 87. ADAPTIVE SUPPORT VENTILATION(ASV) A mode of ventilation that changes the number of mandatory breaths and pressure support level according to the patient’s breathing pattern Indication •Designed to reduce episodes of central apnea in CHF: Improvement in sleep quality, decreased daytime sleepiness •Can be used for patients who are at risk for central apnea like those with Brain damage.
  88. 88. PROPORTIONAL ASSIST VENTILATION (PAV) PAV , there is no target flow, volume, or pressure during mechanical ventilation Advantages •The pressure used to provide the pressure support is variable and is in proportion to the patient’s pulmonary Characterstics and demand. •Has the ability to track changes in breathing effort over time. Disadvantages Where the elastance / airflow resistance shows sudden improvement , the pressure PAV may be too high . This may lead to overdistension , increased air trapping , and barotrauma.
  89. 89. All clinical situations characterized by high ventilatory output uncoupled with ventilatory requirements (i.e. respiratory alkalosis) may be potentially worsened by PAV Indication ARDS Hypercapnic respiratory failure in COPD Adaptability of ventilator to changing patients ventilatory demands Increases sleep efficiency Non- invasive use of PAV in COPD &Kyphoscoliotic patients:delivered through nasal mask; improves dyspnea score.
  90. 90. VOLUME – ASSURED PESSURE SUPPORT ( VAPS) A mode of ventilation that assures a stable tidal volume by incorporating inspiratory PSV with conventional volume- assistd cycles (VAV) ADVANTAGE o VAPS incorporates pressure support ventilation with conventional volume- assisted cycles to provide stable tidal volume in patient with irregular breathing patterns DISADVANTAGE o VAPS may prolong the inspiratory time. o Patients with airflow obstruction should be monitored closely in order to prevent air trapping.
  91. 91. Pressure – Regulated Volume control ( PRVC) It provides volume support with the lowest pressure possible by changing the flow and inspiratory time Advantage Decelerating inspiratory flow pattern Pressure automatically adjusted for changes in compliance and resistance within a set range – Tidal volume guaranteed – Prevents hypoventilation Disadvantage Pressure delivered is dependent on tidal volume achieved on last breath – Intermittent patient effort → variable tidal Volumes Asynchrony with variable patient effort
  92. 92. VOLUME VENTILATION PLUS ( VV+) An option that combines volume control plus and volume support Volume control Plus (VC+) •It is used to deliver mandatory breaths during AC and SIMV modes of ventilation •VC+ is intented to provide a higher level of synchrony than standarad volume control ventilation •In VC + , the clinician sets the target tidal volume inspiratory time. Volume Support ( VS) •It is intended to provide a control tidal volume and increased patient comfort Indicated in – weaning from anesthesia
  93. 93. AIRWAY PRESSURE RELEASE VENTILATION( APRV) APRV- A mode of ventilation in which the spontaneous breaths are at an elevated basline(i.e.CPAP).This elevated baseline is periodically “ released” to facilitate expiration. ADVANTAGE •Preservation of spontaneous breathing and comfort with most spontaneous breathing occurring at high CPAP •↓WOB •↓Barotrauma •↓Circulatory compromise •Better V/Q matching
  94. 94. Disadvantage of APRV •Volumes change with alteration in lung compliance and resistance •Limited access to technology capable of delivering APRV •An adequately designed and powered study to demonstrate reduction in mortality or ventilator days compared with optimal lung protective conventional ventilation •May be less comfortable than the PSV and SIMV modes , and synchonization with mechanical breaths may also be a problem Indication In patient with ARDS ( decreased lung compilance)
  95. 95. Inverse Ratio Ventilation (IRV) Advantage IRV Improves Oxygenation by- 1)Decrease intrapulmonary shunting 2)Increasing V/Q matching 3) Decrease dead space ventilation Disadvantages • Exacerbation of hemodynamic instability •Barotrauma •Requires deep sedation and paralysis •Changes in lung compliance result in changes in delivered
  96. 96. INDICATION 1.I:E ratio is greater than 1, in which inspiration is longer than expiration 2. Used in patients with acute severe hypoxemic respiratory failure. 3. Used with heavily sedated patients 4. Used in ARDS and acute lung injury
  97. 97. AUTOMATIC TUBE COMPENSATION(ATC) A mode of ventilation that offsets and compensates for he air - flow resistance imposed by the arificial airway. It allows the patient to have a breathing pattern as if breathing Spontaneously without an artificial airway. With ATC, the pressure delivered by the ventilator to compensate for the airflow resistance is acitve during inspiration and expiration. It is dependent on the airflow characteristics and the flow demand of the patient.
  98. 98. WEANING
  99. 99. Unnecessary delays in this discontinuation process can increase the complication rate the ventilation(pneumonia , airway trauma) as well as cost. Prematuration discontinuation carries its own set of problem, including difficulty in reestabilishing airtificial airways and compromised gas exchange.
  100. 100. ESSENTIAL TO BEGIN WEANING Patient parameters Awake, alter & co-operative Haemodianamically stable RR> 30/min. No effect of sedation / neuromuscular blockade Minimal secrection Nutritional status good Ventilator parameters Spontaneous TV > 5-8 ml/Kg VC > 10- 15 ml/kg PEEP requriment <5mm of H2O Static complaince > 30 ml/mm of H2O MV < 10 L
  101. 101. Oxygenation crieteria PaCO2 < 50 mm of Hg with normal PH PaO2 > 60 @ FiO2 0.4 / less SaO2 > 90% @ FiO2 0.4 / less PaO2 / FiO2 > 200
  103. 103. References: 1. Clinical application of mechanical ventilation by David W. Chang 2. Management of the mechanically ventilated patient by Lynelle N. B. Pierce 3. Internet refrences