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NON INVASIVE VENTILATION. Definition: NIV is the delivery of mechanical ventilation to the lungs using techniques that do not require an endotracheal airway. Types: negative pressure NIV Main means of NIV during the 1 st half of the 20 th century positive pressure NIV
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Definition: NIV is the delivery of mechanical ventilation to the lungs using techniques that do not require an endotracheal airway
Types: • negative pressure NIV Main means of NIV during the 1st half of the 20th century • positive pressure NIV resurgence in the early 1980s due to the development of nasal CPAP
Why the interest in NIV The desire to avoid complications of invasive ventilation • Complications related to the process of intubation and mechanical ventilation • Aspiration • Trauma • Arrythmias and hypotension • barotrauma • Complications caused by loss of airway defense mechanisms • Direct conduit to lower airway chronic bacterial colonization
Complication that occur after removal of ETT • Hoarseness, sore throat, cough • Sputum production • Upper airway obstruction • hemoptysis • From the patient’s point of view • Discomfort • Decreased ability to eat and communicate
Advantages of NIV • Leaves upper airway intact • Preserve airway defense mechanisms • Allows patient to eat, drink, verbalize and expectorate • Enhance comfort, convenience and portability • Less cost
Interfaces Devices that connect the ventilator‘s tubing to the face allowing pressurized gas to enter into upper airway
Nasal • Cone shaped clear plastic device with soft cuff • Multiple sizes and shapes • Chronic application • Better tolerated by patients with claustrophobia • Exert pressure over the bridge of the nose
Avoided by • Fore head spacer • Nasal mask with gel seal • Mini-masks • Custom-molded individualized masks • Thin plastic flap • Nasal pillows (pledgets directed to the nostrils)
Oronasal ( full face mask) • Preferred • in acute settings • for patients with copious air leaking through the mouth • For edentulous patients • Interferes with speech, eating and expectoration • Increase risk of aspiration, rebreathing • Increase likelihood of claustrophobic reaction • Total face mask (hockey goalie‘s mask)
Mouth pieces • Provides NIPPV to patients with chronic respiratory failure • Simple inexpensive • Nasal air leaking decrease its efficacy • Managed by increasing ventilator‘s tidal volume • Occluding nostrils with cotton pledgets or nose clips
Ventilators for NIPPV • CPAP • Delivers constant pressure during both inspiration and expiration • Increase functional residual capacity • Improve lung compliance • Open collapsed alveoli • Improve oxygenation • Decrease work of breathing • Decrease left ventricular transmural pressure, ↓ afterload and ↑COP • Simple, small and cheap portable units are available
Pressure limited ventilators • PCV • Delivers time- cycled preset inspiratory and expiratory pressures with adjustable I/E ratio • Permits patient triggering with a back up rate • PSV • Assist spontaneous breathing • Peak inspiratory and expiratory pressures are selected • Close matching with patient‘s spontaneous breathing • Allow patient to control rate and inspiratory duration • Portable devices (bilevel devices)
Volume limited ventilators • Vt is usually set higher (10→ 15ml/kg ) • Usually set in the A/C mode, RR set slightly below the patient’s rate • Portable devices are more convenient, cheap, have more sophisticated alarm system, generate high pressure
Proportional assisted ventilation (PAV) • Targets and respond rapidly patient‘s effort ( inspiratory flow and volume) • Able to select the proportion of breathing work that is to be assisted
Negative pressure ventilation • Intermittently apply a sub atmospheric pressure to the chest wall and upper abdomen • Efficiency depends on chest wall and abdomen compliance and surface area over which negative pressure is applied
E.g. • Tank ventilator • Cuirass • Wrap • Shell • Iron lung • Rocking belt and pneumobelt (work by displacing abdominal viscera)
Goals of NIV Short term (acute) • Relieve symptoms • Reduce work of breathing • Improve or stabilize gas exchange • Good patient-ventilator synchrony • Optimize patient comfort • Avoid intubation • Minimize risk Long term (chronic) • Improve sleep duration and quality • Enhance functional status • Prolong survival • Maximize quality of life
PROTOCOL FOR INITIATION OF NIV • Appropriately monitored location • Patient in bed or chair sitting at > 30-degree angle • Select and fit interface • Select ventilator • Apply headgear; avoid excessive strap tension • encourage patient to hold mask • Connect interface to ventilator tubing and turn on ventilator
Start with low pressures/volumes in spontaneously triggered mode with backup rate; pressure-limited: 8 to 12 cm H2O inspiratory; 3 to 5 cm H2O expiratory, volume-limited: 10 ml/kg Gradually increase inspiratory pressure (10 to 20 cm H2O) or tidal volume (10 to 15 ml/kg) as tolerated to achieve alleviation of dyspnea, decreased respiratory rate, increased tidal volume , and good patient-ventilator synchrony Provide O2 supplementation as needed to keep O2 sat > 90%
PROTOCOL FOR INITIATION OF NIV • Check for air leaks, readjust straps as needed • Add humidifier as indicated • Consider mild sedation (i.e., intravenously administered lorazepam 0.5 g) in agitated patients • Encouragement, reassurance, and frequent checks and adjustments as needed • Monitor occasional blood gases (within 1 to 2 h and then as needed)
Monitoring • Subjective responses • Bed side observation • Ask about discomfort related to the mask or airflow • Physiologic response • ↓ RR, ↓ HR • Patient breath in synchrony with the ventilator • ↓ accessory muscle activity and abdominal paradox • Monitor air leaks and Vt • Gas exchange • Continuous oximetry • Occasional ABG
Uses of NIV • Respiratory failure • Hypercapnic respiratory failure • Obstructive diseases • Restrictive diseases • Hypoxic respiratory failure • Acute pulmonary edema • Acute pneumonia • ARDS • Trauma
Imunocomprimized patients • Avoid ETT→ ↓infectious and hemorrhagic complications • Morbidly obese patients • used in obstructive sleep apnea • Do not intubate patients • ETT is contraindicated or postpond • Refuse intubation • Post operative patients • Avoid reintubation if RF develops • Improve gas exchange and pulmonary function • Weaning and extubation • Before meeting extubation criteria
Adverse effects and complications of NIV • Mask related • Nasal pain • Nasal bridge erythema and ulceration • Ventilator air flow or pressure complications • Conjunctival irritation • Sinus or ear pain • Nasal or oral dryness • Nasal congestion or discharge • Gastric insufflation
Failure of NIV • Mask intolerance • Failure to improve ventilation • Claustrophobia • Sensation of excessive air pressure • Patient-ventilator asynchrony • MI • Specially with BIPAP