1. Mechanical Ventilation BY: Jonathan Phillips

2. Introduction Conventional mechanical ventilation refers to the delivery of full or partial ventilatory support by a volume –cycled mechanical ventilator or by pressure support. It can include the maintenance of positive airway pressure at the end of exhalation i.e.. PEEP. Conventional mechanical ventilation refers to the delivery of full or partial ventilatory support by a volume –cycled mechanical ventilator or by pressure support. It can include the maintenance of positive airway pressure at the end of exhalation i.e.. PEEP.

3. Indications The decision to initiate mechanical ventilation entails potentially serious complications. The decision to initiate mechanical ventilation entails potentially serious complications. The main indication for mechanical ventilation is ARF. The main indication for mechanical ventilation is ARF. The parameters needed include respiratory rate >35, inspiratory force 60%, PaCO2 >50mmHg, with pH 35, inspiratory force 60%, PaCO2 >50mmHg, with pH < 7.35. and an absent gag or cough reflex.

4. Common disorders for Mechanical ventilation Acute pulmonary parenchymal diseases, pneumonia, ARDS Acute pulmonary parenchymal diseases, pneumonia, ARDS Cardiogenic pulmonary edema Cardiogenic pulmonary edema Neuromuscular disorders: myasthenia gravis, Guillian Barre syndrome, poliomyelitis, and spinal cord trauma Neuromuscular disorders: myasthenia gravis, Guillian Barre syndrome, poliomyelitis, and spinal cord trauma Systemic illnesses include shock and sepsis Systemic illnesses include shock and sepsis

5. Volume cycled ventilation The controlled variables of tidal volume and inspiratory flow determine airway pressure and inspiratory time. Variations in airway resistance or lung compliance alter airway pressures but do not affect minute ventilation. The controlled variables of tidal volume and inspiratory flow determine airway pressure and inspiratory time. Variations in airway resistance or lung compliance alter airway pressures but do not affect minute ventilation. Controlled mechanical ventilation Controlled mechanical ventilation Assist-control Assist-control Intermittent mandatory ventilation Intermittent mandatory ventilation

6. Controlled mechanical ventilation Minute ventilation is completely dependent upon the rate and tidal volume set on the ventilator. Any respiratory efforts made by the patient do not contribute to minute ventilation. Minute ventilation is completely dependent upon the rate and tidal volume set on the ventilator. Any respiratory efforts made by the patient do not contribute to minute ventilation. CV is required in patients who are not making respiratory effort, spinal cord injury, OD or pharmacologic paralysis CV is required in patients who are not making respiratory effort, spinal cord injury, OD or pharmacologic paralysis

7. CMV Combined neuromuscular paralysis and controlled mechanical ventilation can also be used to avoid volutrauma in patients with ARDS and to avoid baratrauma in asthmatics who are difficult to ventilate. Combined neuromuscular paralysis and controlled mechanical ventilation can also be used to avoid volutrauma in patients with ARDS and to avoid baratrauma in asthmatics who are difficult to ventilate. In these settings hypercapnia is accepted provided that oxygenation is maintained. In these settings hypercapnia is accepted provided that oxygenation is maintained.

8. Assist control In A/C mode the ventilator senses an inspiratory effort by the patient and responds by delivering a preset tidal volume. In A/C mode the ventilator senses an inspiratory effort by the patient and responds by delivering a preset tidal volume. Every inspiratory effort that satisfies the ventilators demand valve trigger threshold, initiates delivery of the preset tidal volume. Every inspiratory effort that satisfies the ventilators demand valve trigger threshold, initiates delivery of the preset tidal volume. A control mode back up rate is set on the ventilator to prevent hypoventilation A control mode back up rate is set on the ventilator to prevent hypoventilation Patient work is required to trigger the ventilator, and continues during inspiration. In the presence of auto-peep the effective trigger threshold is increased by the amount of auto-peep present. Patient work is required to trigger the ventilator, and continues during inspiration. In the presence of auto-peep the effective trigger threshold is increased by the amount of auto-peep present. An ACCP consensus statement cautioned against the initial use of A/C in awake patients with obstructive airway disease, since this can lead to progressive hyperinflation. An ACCP consensus statement cautioned against the initial use of A/C in awake patients with obstructive airway disease, since this can lead to progressive hyperinflation.

9. Intermittent Mandatory ventilation IMV, the degree of ventilator support is determined by the select IMV rate. At regular intervals, the ventilator delivers a breath based upon a preset tidal volume and rate. IMV, the degree of ventilator support is determined by the select IMV rate. At regular intervals, the ventilator delivers a breath based upon a preset tidal volume and rate. The patient is allowed to breathe spontaneously through the ventilator circuit at a tidal volume and rate according to need and capacity. The patient is allowed to breathe spontaneously through the ventilator circuit at a tidal volume and rate according to need and capacity.

10. IMV Most present day ventilators synchronize the intermittent mandatory ventilation breaths with inspirtatory effort by the patient, a modality termed synchronized IMV or SIMV. Most present day ventilators synchronize the intermittent mandatory ventilation breaths with inspirtatory effort by the patient, a modality termed synchronized IMV or SIMV. This modification requires a trigger modality, either a demand valve or flow-by, both of which need patient effort to trigger and therefore increase the work of breathing. This modification requires a trigger modality, either a demand valve or flow-by, both of which need patient effort to trigger and therefore increase the work of breathing.

11. Pressure Support Ventilation PSV is flow-cycled in that, once triggered by a demand valve, the preset pressure is sustained until the inspiratory flow tapers, usually to 25% of its maximal value. PSV is flow-cycled in that, once triggered by a demand valve, the preset pressure is sustained until the inspiratory flow tapers, usually to 25% of its maximal value. PSV tends to be a comfortable ventilatory modality because the patients has greater control over ventilator cycling and flow rates. PSV tends to be a comfortable ventilatory modality because the patients has greater control over ventilator cycling and flow rates. Close monitoring is required whenever PSV is used alone because neither tidal volume or minute ventilation is guaranteed. Close monitoring is required whenever PSV is used alone because neither tidal volume or minute ventilation is guaranteed. PSV is more appropriate during weaning from mechanical ventilation. PSV is more appropriate during weaning from mechanical ventilation.

12. Vent management FIO2-hypoxia is more dangerous than is brief exposure high levels of O2. FIO2-hypoxia is more dangerous than is brief exposure high levels of O2. The initial FIO2 should be 100% The initial FIO2 should be 100% FiO2 can be made to achieve a PaO2 greater than 60mmHg or SaO2 >90%. FiO2 can be made to achieve a PaO2 greater than 60mmHg or SaO2 >90%. Attempts should be made to utilize the lowest possible fraction of FIO2 that maintains the arterial oxygen saturation >90% or PO2 >60% Attempts should be made to utilize the lowest possible fraction of FIO2 that maintains the arterial oxygen saturation >90% or PO2 >60% An FIO2 below 0.5 is preferable to minimize oxygen toxicity. An FIO2 below 0.5 is preferable to minimize oxygen toxicity.

13. Vent Management Respiratory rate of 10-15 breaths per minute to begin. Respiratory rate of 10-15 breaths per minute to begin. In COPD patients, minute ventilation should be adjusted to achieve baseline PaCO2 and not necessarily a normal PaCO2. In COPD patients, minute ventilation should be adjusted to achieve baseline PaCO2 and not necessarily a normal PaCO2. Hyperventilation with resultant metabolic alkalosis in these patients may be associated with serious electrolytes shifts and arrhythmias. Initial tidal volumes usually can be set at 10-12 ml/kg Patients with decreased ling compliance (ARDS) Often need smaller lung volumes 6-8 to minimize peak airway pressures.

14. Vent management PEEP Positive end-expiratory pressure is defined as the maintenance of positive airway pressure at the end of expiration. Positive end-expiratory pressure is defined as the maintenance of positive airway pressure at the end of expiration. It can be applied in both CPAP and continuous positive pressure pressure ventilation. It can be applied in both CPAP and continuous positive pressure pressure ventilation. PEEP increases lung compliance and oxygenation while decreasing the shunt fraction and the work of breathing. PEEP increases lung compliance and oxygenation while decreasing the shunt fraction and the work of breathing.

15. Vent Management PEEP The main goal of PEEP is to achieve a PaO2 greater than 55-60 mm HG with a FIO2 less than or equal to 60%. The main goal of PEEP is to achieve a PaO2 greater than 55-60 mm HG with a FIO2 less than or equal to 60%. PEEP is applied in 3-5 cm H2O increments. PEEP is applied in 3-5 cm H2O increments. PEEP >10 should not have their PEEP removed abruptly, because removal can result in collapse of distal lung units, worsening of shunt, and potentially life threatening hypoxemia. PEEP >10 should not have their PEEP removed abruptly, because removal can result in collapse of distal lung units, worsening of shunt, and potentially life threatening hypoxemia.

16. Vent management Inspiratory flow rate Low flow rates can be associated with prolonged inspiratory times that can lead to the development of auto-PEEP. Low flow rates can be associated with prolonged inspiratory times that can lead to the development of auto-PEEP. The resultant hyperinflation can affect patient hemodynamics adversely by impairing venous return to the heart. The resultant hyperinflation can affect patient hemodynamics adversely by impairing venous return to the heart.

17. Vent Management Trigger sensitivity Pressure triggering to initiate either a machine assisted breath or to permit spontaneous breathing between IMV breaths, or during trials of CPAP. Pressure triggering to initiate either a machine assisted breath or to permit spontaneous breathing between IMV breaths, or during trials of CPAP. The patient must generate a decrease in the airway circuit pressure equal to the selected pressure sensitivity. The patient must generate a decrease in the airway circuit pressure equal to the selected pressure sensitivity. The smallest trigger sensitivity should be selected, allowing the patient to initiate mechanical or spontaneous breaths without causing the ventilator to autocycle. The smallest trigger sensitivity should be selected, allowing the patient to initiate mechanical or spontaneous breaths without causing the ventilator to autocycle.

18. Vent Management Flow-by Refers to triggering of the ventilator by changes in airflow as opposed to changes in airway pressure. Refers to triggering of the ventilator by changes in airflow as opposed to changes in airway pressure. ▪ Flow sensitivity, the rate of inhaled flow that triggers the ventilator to switch from base flow to either a machine delivered or a spontaneous breath. ▪Flow by triggering requires less work of breathing when used with patients receiving CPAP. ▪However it offers no advantage over demand valve triggering when using pressure support ventilation.

20. Weaning Strategies The level of support ventilation is decreased gradually, and the patient assumes more of the work of ventilation. The level of support ventilation is decreased gradually, and the patient assumes more of the work of ventilation. IMV –allows a change from mechanical ventilation to spontaneous breathing by decreasing the ventilator rate gradually. IMV –allows a change from mechanical ventilation to spontaneous breathing by decreasing the ventilator rate gradually.

21. Weaning strategies T-Tube intersperses periods of unassisted spontaneous breathing through a T-Tube with periods of ventilator support. T-Tube intersperses periods of unassisted spontaneous breathing through a T-Tube with periods of ventilator support. Short daytime periods 5-15 minutes 2-6 times a day with increasing periods. Short daytime periods 5-15 minutes 2-6 times a day with increasing periods. Extubation may be appropriate when the patient can tolerate more than 30-90 minutes of T-tube ventilation Extubation may be appropriate when the patient can tolerate more than 30-90 minutes of T-tube ventilation

22. Weaning strategies PSV is used when respiratory muscle weakness appears to be compromising weaning success. PSV is used when respiratory muscle weakness appears to be compromising weaning success. A decrease in respiratory rate with achieved tidal volumes of 10-12 ml/kg signals that the optimal PSV level has been reached. At this point PSV can be reduced. A decrease in respiratory rate with achieved tidal volumes of 10-12 ml/kg signals that the optimal PSV level has been reached. At this point PSV can be reduced. Once PSV level 5-8 cm H2O is reached the patient can be extubated. Once PSV level 5-8 cm H2O is reached the patient can be extubated.

23. Extubation Should be performed early in day Should be performed early in day Patient should be told to cough Patient should be told to cough Elevate head to 30-45 degrees Elevate head to 30-45 degrees Oropharynx should be suctioned Oropharynx should be suctioned Cuff deflated Cuff deflated Patient extubated and face mask placed Patient extubated and face mask placed Patient encouraged to deep breath and cough with HHN to follow Patient encouraged to deep breath and cough with HHN to follow

24. Competency Exam

25. Questions 1. Which is the main indication for vent management? 1. Which is the main indication for vent management? A. Acute respiratory failure A. Acute respiratory failure B. Severe COPD B. Severe COPD C. CO2 retention C. CO2 retention D. Severe pneumonia D. Severe pneumonia

26. Questions 1. Which is the main indication for vent management? 1. Which is the main indication for vent management? A. Acute respiratory failure A. Acute respiratory failure B. Severe COPD B. Severe COPD C. CO2 retention C. CO2 retention D. Severe pneumonia D. Severe pneumonia

27. Questions 2. Which is not a guideline for withdraw of mechanical ventilation? 2. Which is not a guideline for withdraw of mechanical ventilation? A. PaO2 >60 A. PaO2 >60 B. FIO2<50% B. FIO2<50% C.PEEP >10 C.PEEP >10 D.Vital capacity >10 D.Vital capacity >10

28. Questions 2. Which is not a guideline for withdraw of mechanical ventilation? 2. Which is not a guideline for withdraw of mechanical ventilation? A. PaO2 >60 A. PaO2 >60 B. FIO2<50% B. FIO2<50% C.PEEP >10 C.PEEP >10 D.Vital capacity >10 D.Vital capacity >10

29. Questions 3. An FIO2 below this value is preferable to minimize oxygen toxicity? 3. An FIO2 below this value is preferable to minimize oxygen toxicity? A.80% A.80% B.70% B.70% C.60% C.60% D.50% D.50%

30. Questions 3. An FIO2 below this value is preferable to minimize oxygen toxicity? 3. An FIO2 below this value is preferable to minimize oxygen toxicity? A.80% A.80% B.70% B.70% C.60% C.60% D.50% D.50%

31. End of Lecture