Program Information

1. Program Information

2. Basic Mecanical Ventilation #1 Alain Broccard, MD John Marini, MD University of Minnesota Regions Hospital St Paul, MN

3. Objectives To understand: Indications for Positive Pressure Ventilation Invasive Positive pressure ventilation Non-invasive Positive Pressure Ventilation How positive pressure ventilation helps Reduce the work of breathing Restore adequate gas exchange The basics of Invasive positive pressure ventilation (IPPV) Basic Vent Modes Noninvasive positive pressure ventilation (NIPPV)

4. Indications and Rationale for Initiating IPPV Decreased mental status (unable to protect airway) Hypercapnic respiratory failure Hypoxic respiratory failure Intubation to facilitate procedure Pulmonary toilet

5. Approach to MV Is MV indicated ? NO YES Conservative treatment and periodic reassessment NO Contraindication to NIPPV ? YES NIPPV YES Invasive MV Success ? NO

6. Important Pitfalls and Problems Associated with PPV Potential detrimental effects associated with PPV Heart Decreased pre-load Lungs Barotrauma Pneumothorax Gas exchange May increase dead space (compression of capillaries)

7. Important Hemodynamic Effects Associated with PPV Decreasedpreload Decreasedafterload Otherfactorseffectinghemodynamics: Aslungandchestwallcompliancedecreasesodoesvenousreturntotheheart Marini, Wheeler. Crit Care Med. The Essentials. 1997.

8. Common Modes of Ventilation Volume targeted ventilation (flow controlled, volume cycled) AC Pressure targeted ventilation PCV (pressure controlled, time cycled) PS Combination modes SIMV with PS and either volume or pressure-targeted mandatory cycles

9. Pressure and Volume Targeted Ventilation In pressure-targeted ventilation: an airway pressure target and inspiratory time are set, while flow and tidal volume become the dependent variables. In volume targeted ventilation (flow-controlled, volume cycled), a target volume and flow (or inspiratory time in certain ventilator) are preset and pressure and inspiratory time (or flow in the ventilator where inspiratory time is preset) become the dependent variables. The tidal volume is the integral of the flow during inspiration = area under the curve of the flow time curve during inspiration (see next slide).

10. Pressure and Volume Targeted Ventilation VT Marini, Wheeler. Crit Care Med. The Essentials. 1997.

11. Assist-control • Set variables • Volume, TI or flow rate, frequency, flow profile (constant or decel) • PEEP and FIO2 • Mandatory breaths • Ventilator delivers preset volume and preset flow rate at a set back-up rate • Spontaneous breaths • Additional cycles can be triggered by the patient but otherwise are identical to the mandatory breath.

12. Assist-control Advantages Increased ventilatory support / decreased work of breathing Disadvantages Hyperventilation Hemodynamic effects Vent-patient mismatch

13. SIMV Key set variables Targeted volume (or pressure target), flow rate (or inspiratory time, Ti), mandated frequency PEEP, FIO2, pressure support Mandatory breaths Ventilator delivers a fixed number of cycles with a preset volume at preset flow rate. Alternatively, a preset pressure is applied for a specified Ti Spontaneous breaths Unrestricted number, aided by the selected level of pressure support

14. SIMV Advantages Increased ventilatory support / decreased work of breathing Less risk of hyperventilation Disadvantages More work of breathing than assist-control

15. Pressure Support Pressure = set variable. Mandatory breaths: none. Spontaneous breaths Ventilator provides a preset pressure assist, which terminates when flow drops to a specified fraction (typically 25%) of its maximum. Patient effort determines size of breath and flow rate.

16. Pressure Support Advantages Increased patient comfort Flow, rate, and volume controlled by patient Improved vent-patient interface Decreased work of breathing Better recruitment of collapsed alveoli Disadvantages Patient may tire More work of breathing compared to other modes

17. Pressure in Volume Targeted Ventilation Mean Airway Pressure Pressure applied to the lung and chest wall, averaged across both phases of ventilation Peak Airway Pressure Total pressure needed to create the tidal volume Includes: resistive pressure of circuit, PEEP, and lung and chest wall Plateau Pressure Peak airway pressure – resistive component Transpulmonary Pressure Plateau pressure – pleural pressure

18. Airway Resistance and Respiratory System Compliance Airway resistance = (Peak airway pressure – Plateau pressure) divided by the flow Compliance = change in volume divided by the change in pressure High compliance = easily distended (emphysemia) Low compliance = stiff (ARDS, fibrosis, edema)

19. Noninvasive Ventilation Ventilatory assistance provided via mask without intubation Can be volume or pressure mode Patients must meet criteria to be candidates

20. Allows the patients to maintain normal functions Speech Eating Helps avoid the risks and complications related to: Intubation Sedation  Less ventilator-associated pneumonia Key Differences Between NIPPV and IPPV Disadvantages of NIPPV Advantages of NIPPV • Less airway pressure is tolerated • Does not protect against aspiration • No access to airway for suctioning • Not tolerated by some patients • Pressure sores Slide 20

21. Clinical Use of NIPPV in Intensive Care Decompensated COPD (Hypercapnic Respiratory Failure) Cardiogenic pulmonary edema Hypoxic respiratory failure Other possible indications Weaning (post-extubation) Obesity hypoventilation syndrome Post-surgery Asthma Adapted from: Am J Respir Crit Care Med. 2001;163:283-291.

22. Contraindications to NIPPV • Cardiac or respiratory arrest • Nonrespiratory organ failure • Severe encephalopathy (e.g., GCS < 10) • Severe upper gastrointestinal bleeding • Hemodynamic instability or unstable cardiac arrhythmia • Facial surgery, trauma, or deformity • Upper airway obstruction • Inability to cooperate/protect the airway • Inability to clear respiratory secretions • High risk for aspiration Adapted from: Am J Respir Crit Care Med. 2001;163:283-291.

23. Initiating NIPPV Initialsettings: Spontaneoustriggermodewithbackuprate Startwithlowpressures IPAP8-12cmH2O EPAP3-5cmH2O AdjustinspiredO2tokeepO2sat>90% IncreaseIPAPgraduallyupto20cmH2O(astolerated)to: alleviatedyspnea decreaserespiratoryrate increasetidalvolume establishpatient-ventilatorsynchrony

24. Success and Failure Criteria for NIPPV Improvements in pH and PCO2 occurring within 2 hours predict the eventual success of NPPV. If stabilization or improvement has not been achieved during this time period, the patient should be considered an NIPPV failure and intubation must be strongly considered. Other criteria for a failed NIPPV trial include: worsened encephalopathy or agitation, inability to clear secretions, inability to tolerate any available mask, hemodynamic instability, worsened oxygenation.

25. Case Study The following is a case study reflective of this lecture. You will have the opportunity to do a self assessment to test your knowledge. You will only be able to take this self assessment once. You will have another chance to take it again after you review the Mechanical Ventilation Part 2 module. Case Study Skip

26. MV Case

27. References Hubmayr RD, Abel MD, Rehder K. Physiologic approach to mechanical ventilation. Crit Care Med. 1990;18:103-13. Tobin MJ. Mechanical ventilation. N Engl J Med. 1994;330;1056-61. Marini JJ. Monitoring during mechanical ventilation. Clin Chest Med. 1988;9:73-100. Brochard L. Noninvasive ventilation for acute respiratory failure. JAMA. 2002;288:932-935. Calfee CS, Matthay MA. Recent advances in mechanical ventilation. Am J Med. 2005;118:584-91.