2. “… an opening must be attempted in the trunk of the trachea, into which a tube of reed or cane should be put; you will then blow into this, so that the lung may rise again… and the heart becomes strong…” Andreas Vesalius (1555)

3.  Outline: ◦ Indications. ◦ Modes. ◦ Liberation.

4.  Indications: ◦ Airway control (non respiratory reasons)  Surgery.  Level of consciousness.

5.  Indications: ◦ Airway control. ◦ Ventilatory Support.  Decreased Drive.  Overwhelmed Drive. (Supply & Demand)

6.  Indications: ◦ Airway control. ◦ Support of Ventilation. ◦ Support of Oxygenation.  Supply & Demand.

7.  Modes of Ventilation: ◦ Negative pressure ventilation.  Normal Breathing.  NP tank ventilators(Iron Lung) in 1955.

8.  Modes of Ventilation: ◦ Negative pressure ventilation. ◦ Positive Pressure Ventilation.  PSV: Pressure Support Ventilation.  A/C : Assist-Control.  IMV : Intermittent Mandatory Ventilation.

9.  Modes of Ventilation: ◦ Negative pressure ventilation. ◦ Positive Pressure Ventilation.  PSV: Pressure Support Ventilation.  A/C : Assist-Control  SIMV : Synchronized Intermittent Mandatory Ventilation.

10.  Modes of Ventilation: ◦ Negative pressure ventilation. ◦ Positive Pressure Ventilation.  PSV: Pressure Support Ventilation.  A/C : Assist-Control  SIMV / (PS) : Synchronized Intermittent Mandatory Ventilation (with Pressure-support)  PRVC: Pressure Regulated Volume Control Ventilation.  PCV: Pressure Control Ventilation.

11.  PS: Pressure Support. ◦ Set a pressure to deliver a Vt of 8 to 10 ml/Kg. ◦ patients often more comfortable since they have full control over their ventilatory pattern and minute ventilation. ◦ Should not be used in heavily sedated, paralyzed, or comatose patients. ◦ Respiratory muscle fatigue can develop if the pressure support is set too low.

12.  A/C : Assist-Control Ventilation. ◦ Parameters set:  VT  RR  FiO2  PEEP ◦ The ventilator delivers VT for all mandatory and spontaneous breaths. It assumes most/all of the work of breathing. Some patients may tend to hyperventilate on this mode.

13.  SIMV / (PS): ◦ Parameters set:  VT  RR  FiO2  PEEP  PSV ◦ The ventilator will set up a window of opportunity for the patient to trigger a breath spontaneously and if they don’t or the time window elapses a mandatory breath will be delivered. Spontaneous breaths are supported with pressure support to decrease the work of breathing.

14.  PCV: Pressure control Ventilation ◦ Parameters set:  PC (Inspiratory pressure above PEEP)  RR & (I:E) Ratio & Ti  FIO2  PEEP ◦ The breath is pressure limited, not volume. ◦ Used more for ARDS patients. ◦ No guaranteed minute ventilation. ◦ Patients need to be sedated.

15.  Liberation & Weaning ◦ More than half of all critically ill patients can be liberated successfully from mechanical ventilation after a brief trial of spontaneous breathing on the first day that reversal of precipitating factors is recognized. ◦ Gradual reduction of mechanical support, termed weaning, frequently is unnecessary and can prolong the duration of mechanical ventilation.

16.  To wean or NOT to wean? ◦ Does the patient  Need the airway, the ventilator, or both.  Need oxygenation, ventilation, or both.

17.  To wean or NOT to wean? ◦ A trial of spontaneous breathing.*  A 30 min T-piece trial.  A 30 min PS of 6 trial. ◦ Failure of an SBT is a clinical diagnosis.  Rapid-shallow breathing,  Tachycardia (>110 beats per minute).  Hypertension (increment of more than 20 mm Hg).  Mental status changes.  Subjective distress. * Esteban A, Alia I, Tobin MJ, et al: Effect of spontaneous breathing trial duration on outcome of attempts to discontinue mechanical ventilation. Spanish Lung Failure Collaborative Group. Am J Respir Crit Care Med 159:512, 1999.

18.  Analyzing Failure ◦ Airway assessment:  Mechanisms of airway maintenance (e.g., cough, gag, and swallow) are sufficient to protect the airway from secretions. ◦ For short term airway, Wait. ◦ For long term airway, Tracheostomy.

19.  Analyzing Failure ◦ Acute hypercapnia is due to imbalance of supply & demand.  Demand: Fever, Sepsis, Overfeeding.  Supply: Weakness, Increased resistance or decreased compliance. ◦ Rapid-shallow breathing is a sign of impending respiratory failure. ◦ Measure lung mechanics.

20.  Analyzing Failure ◦ Measure lung mechanics.  The RT do these measurements on A/C mode, Square flow waveform and 60 LPM flow.  The patient must not be triggering the ventilator.  Some patients may require sedation/paralysis for these measurements to be accurate. ◦ RAW(airway resistance)= (PIP-Plat)/Flow ◦ Normal across the tube 6-8 ◦ Normal airway resistance 5

21.  Analyzing Failure ◦ Compliance is a change in volume for a change in pressure. (Vt/(Plat-PEEP)) ◦ Normal is 50ml/CmH2O ◦ Chest wall noncompliance.  Abdominal distention, obesity, and kyphoscoliosis.  Usually readily apparent by clinical examination. ◦ Lung noncompliance.  Lung infiltrates, large pleural effusions, or dynamic hyperinflation.