BASIC VENTILATION

1. BASIC VENTILATION Dr David Maritz

2. Mechanical ventilation. Emergency Med Clin N Am. 26 (2008) 849 - 862

3. Introduction • Emergency room-vs-ICU-vs-operating room • Trouble shooting in ICU • Terminology! • Specific scenarios

4. Introduction • Why is the patient on the ventilator? • Is the patient breathing spontaneously? • Who is doing the greater work of breathing? • Volume or pressure targeted strategy? • Dual controlled mode? • What is the set respiratory rate? • What is the total respiratory rate? • What is the set extrinsic / applied PEEP? • Is there intrinsic / auto PEEP? • What is the I:E ratio, flow rate, trigger mode? • What do the respiratory graphics indicate?

5. Introduction • Volume targeted ( volume cycled , volume assist / control) • Pressure targeted • Dual

6. Introduction • RR x Vt = MV • Intubated for airway protection • Septic / severe acidosis • ALI / ARDS • Other scanarios

7. Introduction • Adjust FiO2 • Extrinsic PEEP – offset loss of FRC • Caution in: • Elevated ICP • Unilateral lung process • Hypotension • Hypovolaemia • Pulmonary embolism

9. Introduction • Flow waveform – decelerate • Optimise recruitment • Trigger mode – detects pressure or flow gradient • Patient triggers ventilator • Too high – increased work • Too low – auto trigger • 1 – 3 cmH2O

10. Spontaneous breathing • Supported by pressure support ventilation (PSV) • Clinician sets FiO2 / PEEP • Patient sets RR / flow rate • VT dictated by PS / patient effort / lung compliance • Back up apnea rate

11. Volume targeted mode • Ventilator will generate necessary driving pressure to reach the targeted volume • Beware auto / intrinsic PEEP ( breath stacking) • Therefore progressive air trapping

14. Pressure targeted mode • Ventilator generates preset inspiratory pressure • Vt function of respiratory mechanics • Better pressure distribution • Any change in system compliance / resistance will affect Vt

17. Asthma / COPD • Volume depleted • Hyperinflation (auto-PEEP) • 8-10 breaths per minute • Decrease inspiratory time / increase expiratory time • Vt 6-7 ml/kg • Increase flow rate (80-100l/min) • Square wave form • Permissive hypercapnia • Sedation / paralyze • Sudden hypotension: • Disconnect fom ventilator • Tension pneumo

22. Acute lung injury / ARDS • ARDS: • PaO2/FiO2 < 200 • Bilat pulmonary infiltrates • Wedge presssure < 18mmHg • ALI: • PaO2 / FiO2 < 300 • Lung protection ventilation: • Vt 4-6ml/kg • Higher resp rates • Plateau pressures < 30cmH2O • Permissive hypercapnia • Volume targeted • Sedation / temp paralysis

24. Troubleshooting • Respiratory distress in ventilated patients: • Anxiety • Pain • Inadequate ventilator settings • ETT malfunction • Pulmonary parenchymal process • Extrapulmonary process • Tension pneumotghorax • Severe auto-PEEP • Stable – vs - unstable

25. Hemodynamically stable • Systematic approach • Focused history / exam • Check ventilator / circuit • Respiratory mechanics ( Peak and Plateau pressures) • CXR • Bedside ultrasound

26. Problem with airflow

28. Decreased lung compliance

30. Hemodynamically unstable • Remove from ventilator / hand ventilated 100% O2 (beware if high PEEP) • Severe auto-PEEP: • Do not hyperventilate • Disconnect from ventilator / compress chest • Tension pneumothorax: • Both sides! • Check settings / circuit / ETT etc • Reintubation – DIFFICULT AIRWAY

31. Noninvasive positive pressure ventilation

32. Noninvasive positive pressure ventilation in the emergency department. Emerg Med Clin N Am. 26 (2008) 835 - 847

33. Terminology!!

34. Definition • CPAP a separate entity! • Continuous positive pressure • Tight fitting facemask • Spontaneous breathing • NPPV / NIPPV / Bilevel pressure • Inspiratory pressure (IPAP / inspiratory positive airway pressure) • End expiratory positive pressure (EPAP / expiratory positive airway pressure) • Breaths triggered by patient (back up rate)

35. Rationale • Avoid complications of invasive ventilation • Avoid ICU admissions • Reduce costs • Improve mortality

36. Advantages of NIV  Preservation of airway defence mechanism  Early ventilatory support  Intermittent ventilation  Patient can eat, drink and communicate  Ease of application and removal  Patient can cooperate with physiotherapy  Improved patient comfort  Reduced sedation requirements Avoidance of complications of intubation Ventilation outside hospital setting possible Disadvantages  Mask is uncomfortable/claustrophobic  Time consuming for medical and nursing staff  Airway is not protected  No direct access to bronchial tree for suction

37. Pathophysiology • CPAP – increases alveolar recruitement • = extrinsic PEEP and EPAP • Negates intrinsic PEEP ( auto PEEP / dynamic hyperinflation) • Increases intrathoracic pressure • NPPV / bilevel • IPAP = pressure support • Rest during inspiration

38. Indications • Acute exacerbations COPD • Asthma • Acute pulmonary oedema • Hypoxemic respiratory failure • Immunosuppressed patients • Do not intubate patients • Facilitation of weaning and extubation

39. Exacerbation COPD • Initiate early • Alongside with medical therapy

40. Asthma • Extrinsic PEEP offsets intrinsic PEEP

41. Acute cardiogenic pulmonary edema • CPAP and NPPV improve symptoms • Neither improves mortality • May decrease intubation rates

42. Hypoxic respiratory failure • Mixed data • Further studies needed

43. Feasibility • Very little data on safety • Failure of NPPV associated with: • GCS < 13 • RR > 20 after 1 hour • pH < 7.35 after hour

44. Initiation • No standard approach • High-low approach: • High IPAP (20-25cmH2O) • Low-high approach: • Low IPAP (8-10cmH2O) • EPAP 3-4cmH2O • Significant autopeep / PEEPi - EPAP 4-8cmH2O • Titrate FiO2 • Adjust EPAP

46. Summary • Reversible conditions • Bridging therapy • Close monitoring / follow up