Non Invasive Mechanical Ventilation

1. Non Invasive Mechanical Ventilation

2. Non invasive approaches to ventilatory support have been available for over 50 years. Non invasive ventilation refers to techniques that provide alveolar ventilation without an invasive artificial airway in place i.e. endotracheal or tracheostomy tube is not needed. This can be accomplished by either negative or positive pressure.

3. The use of negative pressure ventilation such as iron lung is dating since the earliest years of the 20th century. They were extensively used during polio epidemics, but fell out of favor with the increasing use of invasive positive pressure ventilation during the 1960s. The past decade has seen a striking resurgence in the use of non-invasive ventilation, fueled by the development of the nasal CPAP mask for treatment of obstructive sleep apnea.

4. The convenience, portability, and cost advantages of this form of ventilation have led to a proliferation of non-invasive devices for use by patients at home.

5. External Negative Pressure Ventilation(ENPV) ENPV was first described in 1928 when Drinker and McKhannsuccessfully ventilated an 8-year-girl with polio using an iron lung. Over the next few decades, large numbers of patients with respiratory failure due to polio were successfully treated during the acute phase of the illness. Approximately 10% of patients required a long-term ventilatory support at home.

6. ENPV is provided by a variety of devices applied externally to the chest wall and abdomen. These devices generate intermittent sub-atmospheric pressure and thus inspiratory airflow. Exhalation is usually passive, resulting from the inward elastic recoil of the lung and chest wall.

7. Devices of ENPV: • Tank ventilator “iron lung”: the most effective one. • Cuirass. • Jacket ventilator. • Hayek oscillator: the most recent variation of cuirass negative pressure ventilator

8. Iron-lung

9. Cuirrass

10. Implication of ENPV Recent studies suggest an effective role of ENPV as a non-invasive treatment for infants with chronic hypoventilation syndrome. ENPV has also been used in the management of acute episodes and relapses of COPD along with oxygen. It has been reported to be an effective therapy allowing for muscle rest and resulting in improvement of function and better survival.

11. Side effects of ENPV: 1- Accentuation or development of upper airway collapse preventing effective ventilation. The problem may be lessened by the use of: -Tracheostomy. -Patient-triggered pumps. -nasal CPAP. 2- Oesophageal dysfunction. usually respond to metoclopramide. 3- Adverse hemodynamic effects. 4- Problems with comfort and fitness especially tank ventilators in patients with severe deformity.

12. Non Invasive Positive Pressure Ventilation(NIPPV) NIPPV overcomes many of the disadvantages associated with negative pressure ventilation. Perhaps the major benefit is elimination of upper airway obstruction and oxygen desaturation associated with NPV.

13. Interface: NIPPV can be applied most commonly with either: - Nasal mask. - Full face mask.

14. Interface: NIPPV can be applied most commonly with either: - Nasal mask. - Full face mask.

15. Clinical implications: (A) Chronic Respiratory Failure (Nocturnal NIPPV) 1. Restrictive lung diseases: a) Neuromuscular diseases. b) Chest wall diseases. 2.Obstructive Sleep Apnea (OSA). 3.Chronic Obstructive Pulmonary Disease (COPD).

16. Clinical implications (cont.): B) Acute Respiratory failure. C) Facilitation of weaning. D) Asthma. E) Cystic Fibrosis: preoperative support before lung transplantation. F) ARDS. G) Cardiogenic pulmonary edema.

17. Modes of Ventilation Almost any ventilator mode that can be applied with an endotracheal tube in place can be administered non-invasively. Volume cycled ventilators have been used successfully utilizing:- control. - Assist-control. - Proportional assist control. Pressure cycled ventilators have been applied utilizing : - Pressure support ventilation (PSV). - BIPAP. - CPAP.

18. Patient Selection Criteria for selecting patients for NIPPV: 1. Alert & cooperative. 2. Hemodynamic stability. 3. No need for endotracheal intubation: to protect airways or to remove excessive secretions. 4. No acute facial trauma. 5. Properly fitted mask. 6. No multiorgan dysfunction.

19. Exclusion criteria: • Respiratory arrest. • Cardiovascular instability (hypo tension, arrhythmias, myocardial infarction). • Somnolence impaired mental status, uncooperative patient. • High aspiration risk; Viscous or copious secretions. • Recent facial or gastro-esophageal surgery. • Crainio-facial trauma, fixed naso-pharyngeal abnormalities. • Burns. • Extreme obesity (>200% of ideal body wt).

20. Criteria to discontinue NIPPV: • Inability to tolerate the mask. • Inability to improve gas exchange or dyspnea. • Need for endotracheal intubation to manage secretions or protect airways. • Hemodynamic instability. • ECG instability. • Failure to improve mental status within 30 minutes of initiating NIPPV in patients who are lethargic from CO2 retention or agitated from hypoxia.

21. Advantages of NIPPV: . Better tolerance. . No need for sedation. . Patient can talk, eat, …

22. Drawbacks of NIPPV: . Air leaks. . Facial skin necrosis . Gastric distension . Eye irritation. . Claustrophobia.

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