Noninvasive Positive Pressure Ventilation Introduction n Noninvasive Positive

Noninvasive Positive Pressure Ventilation

Introduction n Noninvasive Positive Pressure Ventilation is the delivery of assisted breaths without placement of an artificial airway Over the past decade, noninvasive positive pressure ventilation has seen increasing use to treat acute respiratory failure This increase has been mostly driven by the desire to avoid complications of invasive mechanical ventilation, such as tracheal injury, VAP, and heavy sedation that may interfere with the weaning process

Methods of Delivery Currently available Methods of Delivery include: n Interfaces I Nasal masks or pillows n Facial masks n Both attached by means of headgear n

Interfaces II Must be used properly n To avoid air leaks, ( nasal masks carry greater risk) n Nose abrasion n Eye irritation n Poor overall clinical tolerance

Interface III Full facemask seems preferable in acute setting at least during the early phase of NIV n Seems more effective in increasing tidal volume and reducing PCO 2 n Nasal masks are usually used for: n home ventilation n Less distressed patients n Naveilesi P. , Fanfulla et al. Crit. Care Med. 2000

Methods of Delivery Many different Modalities can be delivered via NIV Ventilator Modes: n Volume-Cycle Ventilation Similar to Standard mechanical ventilation n Alveolar ventilation is maintained by adjusting tidal volume and respiratory rate n

Pressure-Support Ventilation Constant positive pressure is applied during patient’s spontaneous inspiration n Tidal volume controlled by adjusting pressuresupport level n Tolerant of small leaks n

Methods of Delivery n Ventilator Modes II n Bi-level Positive Airway Pressure n Overall most widely used in ICU n Different levels of positive pressure during inspiration and expiration n IPAP / EPAP 10 -20/5 -10 cm. H 2 O

n Greater patient tolerance, but increased incidence of aerophagia and air leakage n flow rate or fractional inspired oxygen concentration (FIO 2) adjusted to maintain oxygen saturation at ≥ 90%. n BIPAP is often used

Ventilator Modes III n Face mask continuous positive airway pressure (CPAP) n Simplest form of NIV n Commonly used for OSA n Generally not indicated for ARF n Controversial in acute lung injury n Can be useful in cardiogenic pulmonary edema and postoperative respiratory complications

Protocol for Initiation of Noninvasive Positive Pressure Ventilation 1. 2. 3. 4. 5. 6. 7. Appropriately monitored location, oximetry, vital signs as clinically indicated Patient in bed or chair at >30º angle Select and fit interface Select ventilator Apply headgear; avoid excessive strap tension (one or two fingers under strap) Connect interface to ventilator tubing and turn on ventilator Start with low pressure in spontaneously triggered mode with backup rate; pressure limited: 8 to 12 cm H 2 O inspiratory pressure; 3 to 5 cm H 2 O expiratory pressure

Protocol for Initiation of Noninvasive Positive Pressure Ventilation 8. 9. 10. 11. 12. 13. 14. Gradually increase inspiratory pressure (10 to 20 cm H 2 O) as tolerated to achieve alleviation of dyspnea, decreased respiratory rate, increased tidal volume (if being monitored), and good patientventilator synchrony Provide 02 supplementation to as needed to keep 02 sat >90% Check for air leaks, readjust straps as needed Add humidifier as indicated Consider mild sedation (e. g. intravenously administered lorazepam 0. 5 mg) in agitated patients Encouragement, reassurance, and frequent checks and adjustments as needed Monitor occasional blood gases (within 1 to 2 hours) and then as needed Reproduced from International Consensus in Intensive Care Medicine: Noninvasive positive pressure ventilation in acute respiratory failure. Am. J. Respir Crit. Care Med. 2001, 163. 288

Patient Selection NPPV has been applied in a wide variety of clinical Settings: n n n n Acute exacerbation of COPD Acute cardiogenic pulmonary edema Hypoxemic respiratory failure Postoperative respiratory failure Immunocomprised patients Terminal patients with “do not intubate” orders Adjunct to weaning from invasive mechanical ventilation

CONTRAINDICATIONS TO NPPV n n n n n Cardiac or respiratory arrest Nonrespiratory organ failure Severe encephalopathy (e. g. , GCS , 10) Severe upper gastrointestinal bleeding Hemodynamic instability or unstable cardiac arrhythmia Facial surgery, trauma, or deformity Upper airway obstruction Inability to cooperate/protect the airway Inability to clear respiratory secretions High risk for aspiration AM J Respir Crit Care Med , vol 163 , 2001

Potential Benefits Metaanalyses of randomized trials of NPPV in patients with acute respiratory failure have concluded that NPPV reduces: n n Mortality Need for intubation and associated risks Length of hospital stay and mechanical ventilation These improvements in outcome appear to be greatest for patients with chronic obstructive pulmonary disease and acute pulmonary edema. Liesching, T. et al. Chest 2003

Mechanism of Benefit n Improved Alveolar Ventilation n Reduced work of breathing n Resting of the respiratory musculature n Decreased auto-PEEP and facilitation of ventilator triggering

Goals of NPPV The goals differ depending upon the clinical content n COPD or asthma n Reduce CO 2 by unloading the respiratory muscles and augmenting alveolar ventilation n Stabilizing arterial p. H n n Hypoxemic ARF n Ensure an Adequate Pa. O 2

Goals of NPPV n Cardiogenic Pulmonary Edema n Improve oxygenation n Reduce work of breathing n Increase Cardiac output n Chronic Ventilatory failure n Provide sufficient oxygenation and/or CO 2 to sustain life n Reversing atelectasis n Resting of respiratory muscles elimination

Complications n NIPPV has several potential risks. Most common: n Pressure necrosis of facial skin Cushioning the forehead and the bridge of the nose prior to mask attachment will decrease the likelihood of these problems n Mild gastric distention and aspiration of gastric contents Rarely significant at routinely applied levels of inspiratory pressure support n Decreased sputum clearance n Eye irritation

Complications n Sinus pain or congestion n Modest air leaks at the face seal n Transient hypoxemia and hypercapnia n Delay in intubation Adequate patient monitoring, including pulse oximetry is therefore crucial n Barotrauma is uncommon n Adverse hemodynamic effects are unusual

Advantages of NPPV Avoids Complications of Intubation n Nosocomial pneumonia, the natural glottic barrier is preserved n Reduces need for sedation n Preserves speech n Preserves ability to eat n Improves comfort n

Who Should Administer NPPV and in What Location? n The optimal location for patients receiving NPPV depends on: Capacity for adequate monitoring n Staff skill and experience n Availability of resources n Knowledge of the equipment used n Awareness of potential complications n Etiology of ARF n

Acute exacerbation of chronic obstructive pulmonary disease is a frequent reason for hospital and ICU admission In selected COPD patients with hypercapnic respiratory failure, NPPV has shown: 28% reduction in rate of intubation when compared to patients receiving conventional care (15 -40%)

Reduction in hospital LOS by 4. 43 days: 2. 4 vs. 6. 83 days n Reduction in subsequent admission following discharge: n Reduction in mortality rate, 10% n Subgroup analysis showed that this beneficial effect occurred more in patients with severe exacerbations n Keenan, S. P. and Sinuff, T. Annals of Int. Med. 2003

n Brochard, L. ; Mancebo et al. conducted a prospective randomized study comparing NIPPV delivered through a facemask with standard treatment in patients admitted to five intensive care units over a 15 month period in France, Italy, and Spain n 275 patients with COPD admitted to ICU n 85 recruited n 42 randomly assigned to standard therapy n 43 to noninvasive ventilation

n Similar characteristics on admission: n 11 of 43 (26%) in NIV group were intubated n 31 of 42 (74%) in the standard group p < 0. 001 n Frequency of complications n 16% vs. 48%; P = 0. 001 n Hospital Stay: n n 23 ± 17 days vs. 35 ± 33 days p = 0. 005 In hospital mortality rate n 4 of 43 patients or 9% vs. 12 of 42 patients or 29% p=0. 02 New Eng. J. Med. Volume 333 (13). 1995

“In conclusion we recommend that NPPV be added to standard medical therapy for patients with severe acute exacerbations of COPD. Monitoring such patients closely in a high-dependency unit is necessary to evaluate treatment responsiveness and to facilitate endotracheal intubation if NPPV fails” Keenan S. P. , Sinuff T. , Annals of Int. Med. 138 (11): 861 -70, June 2003

Acute Cardiogenic Pulmonary Edema n n Several NIV modalities have been shown to prevent the need for endotracheal intubation Randomized trials comparing either CPAP or PSV and PEEP with standard medical therapy found similar results in improvements: n Arterial blood gases Respiratory rates Reduced rates of endotracheal mechanical ventilation

Noninvasive continuous positive airway pressure is effective in patients with Cardiogenic Pulmonary Edema n Noninvasive CPAP: n n n Raises intrathoracic pressure Decreases shunting Decreases venous return and preload Decreases afterload However pts with cardiogenic pulmonary edema are vulnerable, particularly those with ischemic heart disease; appropriate drug therapy and close monitoring are needed when using any form of NIV

n Until recently, most successes with NIV were obtained in patients with acute ventilatory failure and respiratory acidosis in whom hypoxemia was not the predominant feature of their respiratory failure

n Patients with hypoxemic respiratory failure due to pneumonia should also be considered for NPPV, provided contraindications do not exist n In particular: n Ability to handle secretions n Continued need for pulmonary toilette

I n In the postoperative setting, CPAP or NPPV is a reasonable option: n improvement in pulmonary function in obese patients after gastroplasty n reduction in intubation rates related to hypoxemia post abdominal surgery n Reduced need for invasive mechanical ventilation and reduced mortality post lung resection (21% vs 50%) and (12. 5% vs. 37. 5%) respectively, compared with oxygen therapy. Critical Care Med, Vol. 33(11), Nov. 2005

NPPV has also been evaluated in immunocompromised hosts with respiratory failure AIDS with PCP pneumonia n Cancer Patients with neutropenia and bil. infiltrates n Solid organ transplant recipients n Elderly Patients n

The use of NPPV in patients who have decided to forego intubation (DNR-DNI) has aroused controversy §Some have suggested that NPPV should be used in these patients or at least be offered to them §Others feel that the use of NPPV in this population of patients would be inappropriate

n NPPV is effective in: n Lessening dyspnea n Alleviate respiratory distress n Allowing autonomy n Allowing continuous verbal communication

n “NPPV offers a dignified and comfortable ventilatory approach and should be considered in the management of terminally ill patients who appear to have reversible causes of acute respiratory failure. ” Crit. Care Med. 2004

What is the Role of NPPV in facilitating Weaning from Mechanical Ventilation? NPPV has effectively been shown in different studies to facilitate weaning in COPD patients and prevent reintubation, especially if applied early.

n NIV permits earlier removal of the ET tube than with conventional PSV and reduces the duration of daily ventilatory support, without increasing the risk of weaning failures.

Conclusion n There is strong evidence supporting the use of noninvasive positive pressure ventilation in several clinical settings. n The success of NPPV is critically dependent on careful patient selection.