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Mechanical Ventilation Management

Mechanical Ventilation Management. October 27, 2009 Prepared by Dr. Trey Woods D.O. Presented by Dr. Nick Cardinal D.O. Which one of following are primary goals of Mechanical Ventilation?. Improve pulmonary gas exchange Decrease oxygen cost of breathing Reverse respiratory muscle fatigue

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Mechanical Ventilation Management

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  1. Mechanical Ventilation Management October 27, 2009 Prepared by Dr. Trey Woods D.O. Presented by Dr. Nick Cardinal D.O.

  2. Which one of following are primary goals of Mechanical Ventilation? • Improve pulmonary gas exchange • Decrease oxygen cost of breathing • Reverse respiratory muscle fatigue • Prevent or reverse atelectasis • All of the above

  3. Respiratory Failure • A functional disorder caused by a conditon that impairs the respiratory system’s ability to remove carbon dioxide CO2 or delivery oxygen O2 to the capillary bed.

  4. Treatment of respiratory failure The critical period before the patient needs to be intubated • Prevention • Incentive spirometry • Mobilization • Humidified air • Pain control • Turn, cough, deep breathe • Treatment • Medications • Albuterol • Theophylline • Steroids • CPAP, BiPAP, IPPB • Intubation

  5. Indications for intubation How the values trend should significantly impact clinical decisions • Criteria • Clinical deterioration • Tachypnea: RR >35 • Hypoxia: pO2<60mm Hg • Hypercarbia: pCO2 > 55mm Hg • Minute ventilation<10 L/min • Tidal volume <5-10 ml/kg • Negative inspiratory force < 25cm H2O (how strong the pt can suck in) • Initial vent settings • FiO2 = 50% • PEEP = 5cm H2O • RR = 12 – 15 breaths/min • VT = 10 – 12 ml/kg • COPD = 10 ml/kg (prevent overinflation) • ARDS = 8 ml/kg (prevent volutrauma) • Permissive hypercapnea • Pressure Support = 10cm H2O

  6. Goals • Patient comfort and rest • Reversal of Hypoxemia • Reversal of acute respiratory acidosis • Reversal of respiratory muscle fatigue • Prevention/Reversal of atelectasis • Decrease myocardial VO2 • Allowance of neuromuscular blockade • Improve lung compliance

  7. Ventilation The goal of ventilation is to facilitate CO2 release and maintain normal PaCO2 • Minute ventilation (VE) • Total amount of gas exhaled/min. • VE = (RR) x (TV) • VE comprised of 2 factors • VA = alveolar ventilation • VD = dead space ventilation • VD/VT = 0.33 • VE regulated by brain stem, responding to pH and PaCO2 • Ventilation in context of ED • Increased CO2 production • fever, sepsis, injury, overfeeding • Increased VD • atelectasis,lung injury, ARDS, pulmonary embolism • Adjustments: RR and TV V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation).

  8. Oxygenation The primary goal of oxygenation is to maximize O2 delivery to blood (PaO2) • Alveolar-arterial O2 gradient (PAO2 – PaO2) • Equilibrium between oxygen in blood and oxygen in alveoli • A-a gradient measures efficiency of oxygenation • PaO2 partially depends on ventilation but more on V/Q matching • Oxygenation in context of ICU • V/Q mismatching • Patient position (supine) • Airway pressure, pulmonary parenchymal disease, small-airway disease • Adjustments: FiO2 and PEEP V/Q Matching. Zone 1 demonstrates dead-space ventilation (ventilation without perfusion). Zone 2 demonstrates normal perfusion. Zone 3 demonstrates shunting (perfusion without ventilation).

  9. Pressure ventilation vs. volume ventilation Pressure-cycled modes deliver a fixed pressure at variable volume (neonates) Volume-cycled modes deliver a fixed volume at variable pressure (adults) • Pressure-cycled modes • Pressure Support Ventilation (PSV) • Pressure Control Ventilation (PCV) • CPAP • BiPAP • Volume-cycled modes • Control • Assist • Assist/Control • Intermittent Mandatory Ventilation (IMV) • Synchronous Intermittent Mandatory Ventilation (SIMV) Volume-cycled modes have the inherent risk of volutrauma.

  10. Pressure Support Ventilation (PSV) Patient determines RR, VE, inspiratory time – a purely spontaneous mode • Parameters • Triggered by pt’s own breath • Limited by pressure • Affects inspiration only • Uses • Complement volume-cycled modes (i.e., SIMV) • Does not augment TV but overcomes resistance created by ventilator tubing • PSV alone • Used alone for recovering intubated pts who are not quite ready for extubation • Augments inflation volumes during spontaneous breaths • BiPAP (CPAP plus PS) PSV is most often used together with other volume-cycled modes. PSV provides sufficient pressure to overcome the resistance of the ventilator tubing, and acts during inspiration only.

  11. Pressure Control Ventilation (PCV) Ventilator determines inspiratory time – no patient participation • Parameters • Triggered by time • Limited by pressure • Affects inspiration only • Disadvantages • Requires frequent adjustments to maintain adequate VE • Pt with noncompliant lungs may require alterations in inspiratory times to achieve adequate TV

  12. Assist/Control Mode Ventilator delivers a fixed volume • 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)

  13. IMV and SIMV Volume-cycled modes typically augmented with Pressure Support • IMV • Pt receives a set number of ventilator breaths • Different from Control: pt can initiate own (spontaneous) breaths • Different from Assist: spontaneous breaths are not supported by machine with fixed TV • Ventilator always delivers breath, even if pt exhaling • SIMV • Most commonly used mode • Spontaneous breaths and mandatory breaths • If pt has respiratory drive, the mandatory breaths are synchronized with the pt’s inspiratory effort

  14. Vent settings to improve <oxygenation> PEEP and FiO2 are adjusted in tandem • FIO2 • Simplest maneuver to quickly increase PaO2 • Long-term toxicity at >60% • Free radical damage • Inadequate oxygenation despite 100% FiO2 usually due to pulmonary shunting • Collapse – Atelectasis • Pus-filled alveoli – Pneumonia • Water/Protein – ARDS • Water – CHF • Blood - Hemorrhage

  15. Vent settings to improve <oxygenation> PEEP and FiO2 are adjusted in tandem • PEEP • Increases FRC • Prevents progressive atelectasis and intrapulmonary shunting • Prevents repetitive opening/closing (injury) • Recruits collapsed alveoli and improves V/Q matching • Resolves intrapulmonary shunting • Improves compliance • Enables maintenance of adequate PaO2 at a safe FiO2 level • Disadvantages • Increases intrathoracic pressure (may require pulmonary a. catheter) • May lead to ARDS • Rupture: PTX, pulmonary edema Oxygen delivery (DO2), not PaO2, should be used to assess optimal PEEP.

  16. Vent settings to improve <ventilation> RR and TV are adjusted to maintain VE and PaCO2 • Respiratory rate • Max RR at 35 breaths/min • Efficiency of ventilation decreases with increasing RR • Decreased time for alveolar emptying • TV • Goal of 10 ml/kg • Risk of volutrauma • Other means to decrease PaCO2 • Reduce muscular activity/seizures • Minimizing exogenous carb load • Controlling hypermetabolic states • Permissive hypercapnea • Preferable to dangerously high RR and TV, as long as pH > 7.15 • I:E ratio (IRV) • Increasing inspiration time will increase TV, but may lead to auto-PEEP • PIP • Elevated PIP suggests need for switch from volume-cycled to pressure-cycled mode • Maintained at <45cm H2O to minimize barotrauma • Plateau pressures • Pressure measured at the end of inspiratory phase • Maintained at <30-35cm H2O to minimize barotrauma

  17. Variables for Initial Settings Fraction of Inspired O2Tidal VolumeRespiratory RateFlow RateFlow Profile Mode PEEP -FIO2-TV-RR(f)-Vi(L/m)-(square, Decelerating)-(A/C, SIMV, PS)=(cm of H2O)

  18. Initial Settings • Select mode suitable for pts clinical state most of the times-A/C • Set FiO2 to 100% initially and reduce gradually to less than 60% keeping SaO2 more than 89-92% • Choose Minute ventilation appropriate for pts condition, target pH and not pCO2 most commonly rate –10-12/m

  19. Initial Settings • Choose Tidal volume 5-8ml/PBW in kg • ARDS – 5-6ml/ IBW in kg • Neuromuscular failure – 8-10ml/PBW in kg Calculate predicted body weight • Male: 50+2.3[height(inches)-60] • Females: 45.5+ 2.3[height(inches)-60] • Low level of PEEP –3-5cm of H2O • ARDS- might need to titrate –15 to decrease FiO2 to 60% • COPD- PEEP less than Auto PEEP to Decrease WOB, • Flows – 60-80L/m for pts comfort and to avoid dys - synchrony and keep I:E =/> 1:3

  20. Ventilator management algorithim Modified from Sena et al, ACS Surgery: Principles and Practice (2005). • Initial intubation • FiO2 = 50% • PEEP = 5 • RR = 12 – 15 • VT = 8 – 10 ml/kg SaO2 < 90% SaO2 > 90% • SaO2 < 90% • Increase FiO2 (keep SaO2>90%) • Increase PEEP to max 20 • Identify possible acute lung injury • Identify respiratory failure causes • SaO2 > 90% • Adjust RR to maintain PaCO2 = 40 • Reduce FiO2 < 50% as tolerated • Reduce PEEP < 8 as tolerated • Assess criteria for SBT daily No injury Pass SBT Extubate Airway stable Acute lung injury Fail SBT Airway stable • Persistently fail SBT • Consider tracheostomy • Resume daily SBTs with CPAP or tracheostomy collar • Acute lung injury • Low TV (lung-protective) settings • Reduce TV to 6 ml/kg • Increase RR up to 35 to keep pH > 7.2, PaCO2 < 50 • Adjust PEEP to keep FiO2 < 60% Pass SBT Intubated > 2 wks SaO2 < 90% SaO2 > 90% Prolonged ventilator dependence • SaO2 < 90% • Dx/Tx associated conditions (PTX, hemothorax, hydrothorax) • Consider adjunct measures (prone positioning, HFOV, IRV) • SaO2 > 90% • Continue lung-protective ventilation until: • PaO2/FiO2 > 300 • Criteria met for SBT • Consider PSV wean (gradual reduction of pressure support) • Consider gradual increases in SBT duration until endurance improves Pass SBT

  21. Requirements for Noninvasive Mechanical Ventilation • Experienced support staff -- RT, nursing and physician education • Variety of facemask sizes and types to assure comfort and air seal • A cooperative patient who is willing to participate in their care

  22. NIPPV • Can be described as application of preset volume/pressure of inspiratory air through a face mask or nasal mask. • Inspiratory muscle fatigue is the final phase of ventilatory failure in patients with Severe reactive airway disease, COPD, and end-state pulmonary edema/pneumonia.

  23. CPAP • Improves pulm funct by reducing the work of breathing, maintaining inflation of atelectatic alveoli, and improving pulm compliance • Also improves hemodynamics by reducing pre&after load, therefor improving CO in LV Failure. • Early ED studies showed CPAP up to 10 to 12.5cm showed a significant improvement in PaO2, stroke volume index, lower rate-pressure product, intrapulmonary shunt fraction, alveolar-arterial oxygen gradient, and more importantly lower rate of tracheal intubation.

  24. BiPAP • NIPPV where pos airway press assist the pat’s spontaneous ventilation at a bilevel. Pos press incr during inspir and post exp press provides the Positive end-expiratory pressure PEEP. • BiPAP responds to pts resp cycle by alternating between a higher flow rate during inhalation phase, and lower flow rate during exhalation. • Use of BiPAP in COPD exacerbation has shown to decr intubation 76% • Has been shown to reduce resp rate, dyspnea, and allow more rapid improvement in oxygenation and ventilation. Increase the likelihood of survival to discharge, decr nosocomial infection, Decr LOS • Peds-- appears to improve resp rate, hrt rate,PaCO2 and O2 sat.

  25. CPAP and BiPAP CPAP is essentially constant PEEP; BiPAP is CPAP plus PS • Parameters • CPAP – PEEP set at 5-10 cm H2O • BiPAP – CPAP with Pressure Support (5-20 cm H2O) • Shown to reduce need for intubation and mortality in COPD pts • Indications • When medical therapy fails (tachypnea, hypoxemia, respiratory acidosis) • Use in conjunction with bronchodilators, steroids, oral/parenteral steroids, antibiotics to prevent/delay intubation • Weaning protocols • Obstructive Sleep Apnea

  26. BiPAP • Respiratory failure from ventilation problems responds better to BiPAP than oxygenation problems. (exception is CHF) • BiPAP is good fro COPD, CHF, Acute Pulmonary Edema, OSA • Better for Hypercapneic than Hypoxemic states

  27. BiBAP (NIV Results) • Best results with COPD and CHF • Decreased intubations, ICU LOS, and Mortality. • Best mask style not known • Adult more than Peds • Patient selection criteria not established • Increasing DNR role (use instead of intubation to bring back when DNR is in question)

  28. BiPAP in CHF will shift Frank-Starling Curve to the Left by decreasing LV EDV and Increasing CO (15-20%)

  29. BiPAP Bilevel Positive Airway Pressure • Delivers inspiratory pressure support, coupled with continuous positive airway pressure. Permits a differential support of inspiratory and expiratory efforts with one machine. • Inspiratory, pressure support component increases tidal volume, and positively effects work of breathing. • Inspiratory component requires patient effort for activation (can’t use if they’re apneic)

  30. BiPAP Spontaneous Mode • Trigger--patient effort • Limit--airway pressure • Cycle--patient effort dictated

  31. BiPAP Spontaneous Mode • Patient dependent variables • Respiratory rate • Tidal volume • Inspiratory/expiratory times • Provides inspiratory BOOST. Equal to pressure support and PEEP

  32. BiPAP Spontaneous Mode • Settings • IPAP inspiratory pressure • EPAP expiratory pressure • Rise time • Backup respiratory rate (S/T mode only) • ** (S/T spontaneuos timed)

  33. BiPAP Spontaneous Timed Mode • Trigger--patient effort or time interval • Limit--airway pressure • Cycle--patient effort or time interval dictated

  34. Settings for Noninvasive CPAP Mechanical Ventilation • Start with low pressures @ 5cm H2O • Increase in increments of 2cm H2O Settings for Noninvasive BiPAP Mechanical Ventilation • Inspiratory positive airway pressure setting IPAP (4-24 cm H2O) • Expiratory positvie airway pressure setting EPAP (0-20cm H2O)

  35. Settings for Noninvasive BiPAP Mechanical Ventilation • Inspiratory pressure must be maintained at higher than the expiratory pressure stettings at all times. • Flow is synchronized with patient inspiratory efforts • Increases in inspiratory pressures IPAP will predominantly effect PCO2 • IPAP is equivalent to pressure support • Increases in expiratory pressures EPAP will predominantly effect PaO2 • Expiratory phase is constant back pressure, PEEP/EPAP distending the airways augmenting tethering • Typical initial setting for BiPAP--- IPAP/EPAP levels of 8/3 to 10/5.

  36. CPAP Continuous Positive Airway Pressure • Delivery of a static-positive airway pressure that is maintained throughout the inspiratory and expiratory cycle. • Does not provide inspiratory boost.

  37. CPAP Continuous Positive Airway Pressure • Increases FRC • Reduces venous return • May positively or negatively effect cardiac output depending on the pathological state. • Recruits alveoli to gas exchange and improves pulmonary compliance = PEEP • Reduce inspiratory threshold pressure- the force needed to establish airflow

  38. Getting Started with NIPPV • Start with the lowest levels possible • Have the patient hold the mask themselves and help choose • Time spent coaching is time well spent.

  39. Contraindication to Noninvasive Mechanical Ventilation • Rapid deterioration • Decreased mental status/ psychosis • Aspiration risk/ aerophagia • Facial instability/ pressure necrosis • Need for a definitive airway/ ventilation • Excess secretions • Coronary ischemia

  40. Predictors of Failure in Noninvasive Mechanical Ventilation • Trial of 354 patients • Higher severity of illness score • Older age • ARDS • Pneumonia • Failure to improve in one hour

  41. UpcomingBiPAP Auto with Bi-Flex • Can sense sleep states (if snore or apnea is detected, automatic augmentation of EPAP occurs) Hypopnea trigger IPAP increase. • Bi-Flex softens the airway pressure changes • Rounded corners no the abrupt rectangular tracing • Event reporting • Humidified air • May be ideal for ED sleepers with OSA

  42. Pearls for NPPV • Start with low pressures 8/3 or only CPAP • Have patients hold the mask and apply • Constant reassurance • Tread lightly with sedation • Pediatric patients-consider it • Correct hypoxia with appropriate oxygen- less concern over Oxygen toxicity acutely • Consider intubation if not improved in 1 hour.

  43. References • Lieberman, MD; Ho, MD Surgery ICU Service Stanford University Medical Center, September 25, 2006. Principles of Mechanical Ventilation, The Basics. • DIGVIJAY SINGH, MD., FCCP. Mechanical Ventilation. • Ventilator Management. Clinician’s Pocket Referecne, CH 20 Critical Care. AccessMedicine. 10/11/09. • UpToDate. • USC Essentials 2007 BiPAP, Mechanical Ventilation, Non-invasive Ventilation. • Sena, MJ et al. Mechanical Ventilation. ACS Surgery: Principles and Practice 2005; pg. 1-16. • Marino, PL. The ICU Book. 2nd edition. 1998. • Byrd, RP. Mechanical ventilation. Emedicine, 6/6/06.

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