Definition.. Noninvasive ventilation is the delivery of ventilatory support without the need for an invasive artificial airway The use of NIV in acute hospital settings and at home has been steadily increasing

INTRODUCTION Negative pressure ventilators (Tank and Cuirass ventilators) were the only non-invasive methods of assisting ventilation for many years mainly for ventilating large number of victims of Polio during their acute illness. In 1980s it was recognized that delivery of continuous positive airway pressure by close fitting nasal masks for treatment of obstructive sleep apnea could also be used to deliver an intermittent positive pressure. This was followed by improvements in the interface and establishment of role of NIMV in patients of COPD. The use of NIMV has increased in last decade in various conditions to avoid complications of intubation.

Negative-Pressure Ventilation Late 1880s – iron lungs first used Early 1900s – iron lungs used for polio epidemics This continued throughout the 20th century until 1960s when invasive ventilation became available

Types of NIV Negative pressure ventilation (iron or tank-chest cuirass) Abdominal Displacement(Pneumobelt-Rocking bed) Positive pressure ventilation(pressure BIPAP- CPAP)

Function of Negative Pressure Ventilators Negative pressure is applied intermittently to the thoracic area resulting in a pressure drop around the thorax This negative pressure is transmitted to the pleural space and alveoli creating a pressure gradient between the inside of the lungs and the mouth As a result gas flows into the lungs

Noninvasive positive pressure ventilation (NPPV) Noninvasive positive pressure ventilation (NPPV) is the delivery of mechanically assisted or generated breaths without placement of artificial airway Both CPAP and BiPAP are considered NPPV

Location of NIV NIV can be administered in the emergency department, intermediate care unit, or general respiratory ward

Mechanism of benefit Improved alveolar ventilation Reduced work of breathing Rest of the respiratory musculature Increased intrathoracic pressure, decreases preload and afterload Why does it decrease mortality? Decreased hospital-acquired infections Decreased trauma from intubation Less complications of sedation

Permits normal eating, drinking and communication with your patient Benefits of Using NPPV NPPV provides greater flexibility in initiating and removing mechanical ventilation Permits normal eating, drinking and communication with your patient Preserves airway defense, speech, and swallowing mechanisms

Disadvantages of NIV 1.System 2.Mask Slower correction of gas exchange abnormalities Increased initial time commitment Gastric distension (occurs in <2% patients) 2.Mask Air leakage Transient hypoxemia from accidental removal Eye irritation Facial skin necrosis –most common complication.

Potential indicators of success in NPPV use Younger age Lower acuity of illness (APACHE score) Able to cooperate, better neurologic score Less air leaking Moderate hypercarbia (PaCO2 >45 mmHG, <92 mmHG) Moderate acidemia (pH <7.35, >7.10) Improvements in gas exchange and heart respiratory rates within first 2 hours

Nasal Masks Dual density foam bridge forehead support 360 swivel standard elbow Dual density foam bridge forehead support Thin flexible & bridge material Dual flap cushion Respironics Contour Deluxe™ Mask

Full Face Masks Most often successful in the critically ill patient Entrainment valve Adjustable Forehead Support Ball and Socket Clip Double-foam cushion Pressure pick-off port Respironics PerformaTrak® Full Face Mask

Less effectiveness with nasal obstruction Advantages of Nasal Masks Disadvantages of Nasal Masks Less risk of aspiration Enhanced secretion clearance Less claustrophobia Easier speech Less dead space Mouth leak Less effectiveness with nasal obstruction Nasal irritation and rhinorrhea Mouth dryness

Suitable for patients with Claustrophobia Skin sensitivities Nasal Pillows or Nasal Cushions (continued) Suitable for patients with Claustrophobia Skin sensitivities Need for visibility Respironics Comfort Lite Nasal Mask

Indications for CPAP Cardiogenic Pulmonary Oedema Obstructive Sleep Apnoea Chest Wall Trauma if hypoxic on adequate analgesia Pneumonia

Indications for BiPAP Exacerbation of COPD with Respiratory acidosis Type II respiratory failure with chest wall deformity or neuromuscular disease Failure of CPAP Pneumonia with respiratory acidosis Therapeutic trial with a view to intubation if it fails Others (ARDS, post-op respiratory failure, to buy time prior to intubation)

CPAP Nasal or face mask Continuous positive pressure applied to the airways Usually well-tolerated Similar to use of PEEP Reduces work of breathing Improve ventilation to collapsed areas of lung

BiPAP Bi-Level pressure support Inspiratory Positive Airway Pressure (IPAP) & Expiratory PAP (EPAP) IPAP is the pressure support machine gives to help patients own inspiration Helps to reduce WOB and increase alveolar ventilation EPAP is essentially PEEP and help to prevent alveolar collapse

Indications for CPAP Cardiogenic Pulmonary Oedema Obstructive Sleep Apnoea Chest Wall Trauma if hypoxic on adequate analgesia Pneumonia

Indications for BiPAP Exacerbation of COPD with Respiratory acidosis Type II respiratory failure with chest wall deformity or neuromuscular disease Failure of CPAP Pneumonia with respiratory acidosis Therapeutic trial with a view to intubation if it fails Others (ARDS, post-op respiratory failure, to buy time prior to intubation)

Contraindications Uncooperative patient Altered mental status Risk of aspiration Hemodynamic instability/Severe sepsis Acute myocardial infarction or ischemia Facial/neck trauma or surgery Excess secretions or upper GI bleed

Patient Selection Sick but not moribund Able to protect airway Conscious and co-operative Haemodynamically stable No excessive secretions Few co-morbidities Improvement on ABG with NIV

Patient Rejection Respiratory arrest Haemodynamically unstable Uncooperative Unable to protect airway (swallowing and cough impaired or vomiting) Facial, oesophageal, or gastric surgery Craniofacial trauma or burns Airway obstruction Undrained Pneumothorax

Position of exhalation port and mask design affect CO2 rebreathing during NIV Crit Care Med. 2003 Aug;31 facial mask with exhalation port within the mask compared with port in the ventilator circuit smallest mask volume less rebreathed CO2 inspiratory load

Humidification during NIV No humidification: drying of nasal mucosa; increased airway resistance; decreased compliance. HME lessens the efficacy of NIV Only pass-over humidifiers should be used Intensive Care Med. 2002;28

Aerosol bronchodilator delivery during NIV optimum nebulizer position: between the leak port and patient connection Optimum ventilator settings: high inspiratory pressure and low expiratory pressure. Optimum RR 20/mt. Rather than 10/mt. 25% of salbutamol dose may be delivered Crit Care Med. 2002 Nov;30

Monitoring Response Physiological a) Continuous oximetry b) Exhaled tidal volume c) ABG should be obtained with 1 hour and, as necessary, at 2 to 6 hour intervals. Objective a) Respiratory rate b) blood pressure c) pulse rate Subjective a) dyspnea b) comfort c) mental alertness

Monitoring….. Mask Fit, Comfort, Air leak, Secretions, Skin necrosis Respiratory muscle unloading Accessory muscle activity, paradoxical abdominal motion Abdomen Gastric distension

Criteria to discontinue NIV Inability to tolerate the mask because of discomfort or pain Inability to improve gas exchange or dyspnea Need for endotracheal intubation to manage secretions or protect airway Hemodynamic instability ECG – ischemia/arrhythmia Failure to improve mental status in those with CO2 narcosis.

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