NON INVASIVE VENTILATION, Virinchi Hospitals, Hyderabad

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NONINVASIVE VENTILATION:

Dr. umamaheshwara rao Dept. of Anaesthesiology & Critical Care Medicine . NONINVASIVE VENTILATION

VENTILATION:

Ventilation is the movement of air in and out of the lungs. Movement of air is dependent on pressure differences between the atmosphere and the spaces in the lung ( alveolar lumen). Flow =   (P1 - P2)/R P1 = atmospheric pressure ( Patm ) P2 = intra-alveolar pressure ( Palv ) R = Resistance VENTILATION

VENTILATION:

When the air pressure inside the lungs ( Palv ) is less than the atmospheric pressure ( Patm ) air will flow into the lungs. Inhalation = Patm > Palv When the alveolar pressure exceeds the atmospheric pressure, the air will flow out of the lungs. Exhalation = Patm < Palv VENTILATION

VENTILATION:

Resistance (R) in the respiratory system is primarily a factor of the radius of the bronchial passages. As the radius decreases, the resistance increases and flow decreases. The radius of the bronchial system can be modified by the smooth muscle surrounding the passages or by mucous collecting inside the bronchioles. VENTILATION

VENTILATION:

The changes in pressure and drive of gas during the ventilation process is dependent on one of the gas laws - Boyle’s law. Boyle’s law states " when the temperature is constant and a chamber’s volume is increased, the pressure in the chamber decreases and vice versa " . Increased volume = decreased pressure Decreased volume = increased pressure VENTILATION

VENTILATION:

VENTILATION When the lungs are expanded during inhalation, Palv decreases below Patm and air flow into the lungs. When the lungs are compressed during exhalation, Palv is increased to greater than Patm and air flows out of the lungs.

Normal Respiration:

Normal Respiration

NONINVASIVE VENTILATION:

Noninvasive ventilation is the delivery of ventilatory support without the need for an invasive artificial airway (E.T.Tube,Tracheostomy). Traditionally ,noninvasive ventilation has been given with the use of devices that apply intermittent negative extra-thoracic pressure. NONINVASIVE VENTILATION

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The concept of mechanical ventilation first evolved with negative – pressure ventilation. 1876 – Woillez first developed a workable iron lung. 1889 – Alexander Graham Bell designed & built a prototype of iron lung. 1928 – Drinker introduced neg-pressure ventilation & popularized the iron lung. He maintained an 8 yr old girl with acute poliomyelitis on artificial respiration for 122 hrs. Tank & cuirass ventilators were the only non-invasive methods of assisting ventilation for large number of polio victims. History of Noninvasive ventilation

History of Noninvasive ventilation:

The epidemics of polio in the 1930,40, & 50’s led to development of pulmonary medicine as a specialty & iron lung as a workhorse . 1960 – use of invasive postive – pressure ventilation increased . 1980– use of noninvasive ventilation, fueled by the development of PPV delivered by close fitting nasal or face masks History of Noninvasive ventilation

History of Noninvasive ventilation:

History of Noninvasive ventilation

NONINVASIVE VENTILATION:

Techniques of application : 1. Negative –Pressure Ventilation(NIV). 2. NonInvasive Positive-Pressure Ventilation (NPPV). NONINVASIVE VENTILATION

NEGATIVE-PRESSURE VENTILATION :

Negative-pressure ventilators support ventilation by exposing the chest wall to subatmospheric pressure during inspiration, with expiration occurring as the pressure around the chest wall is allowed to re-turn to atmospheric levels . NEGATIVE-PRESSURE VENTILATION

NEGATIVE-PRESSURE VENTILATION:

Several devices are available that generate negative extrathoracic pressure and augment tidal volume . Devices -- 1.Body Ventilators 2. Iron lung Body ventilators apply negative pressure to the entire body below the neck . Iron lung weigh less than 45 kg (100 lb). Less bulky and more portable devices have been designed to apply negative pressure to the thorax and abdomen NEGATIVE-PRESSURE VENTILATION

NEGATIVE-PRESSURE VENTILATION:

Several uncontrolled studies reported benefits of intermittent negative-pressure ventilation in patients with chronic respiratory failure due to chest-wall deformities,neuromuscular , or central hypoventilation diseases. But in a large study done in stable COPD pts, found that 12weeks of negative-pressure ventilation had no benefit. The role of negative-pressure ventilation in the management of acute respiratory failure is unclear ( Shapiro SH, Ernst P, Gray-Donald K, et al . Effect of negative pressure ventilation in severe chronic obstructive pulmonary disease. Lancet 1992;340:1425-9.) NEGATIVE-PRESSURE VENTILATION

NonInvasive Positive-Pressure Ventilation (NPPV) :

NPPV is delivered by a nasal or face mask, therefore eliminating the need for intubation or tracheostomy . NPPV can be given by : 1. Volume ventilator 2. Pressure-controlled ventilator 3. Bilevel positive airway pressure (BIPAP ) 4. Continuous positive airway pressure (CPAP) device NonInvasive Positive-Pressure Ventilation (NPPV)

NonInvasive Positive-Pressure Ventilation (NPPV) :

Volume ventilators : Volume-cycled noninvasive ventilation , in which the ventilator delivers a set volume for each breath, can improve outcomes in acute respiratory failure & has been used to manage chronic respiratory failure. Patient’s tolerance of this therapy is often poor because the inspiratory pressure may be elevated, which can be uncomfortable and cause leak. ( Soo Hoo GW, Santiago S, Williams AJ. Crit Care Med 1994;22:1253- 61.) NonInvasive Positive-Pressure Ventilation (NPPV)

NonInvasive Positive-Pressure Ventilation :

Pressure Ventilation Positive-pressure noninvasive ventilation , in which the ventilator delivers a set pressure for each breath, is commonly given with bilevel PAP ventilators or with standard ventilators that use pressure support(PSV). PSV mode has unique ability to vary inspiratory time breath by breath, permitting close matching with the patient's spontaneous breathing pattern. Ventilation by noninvasively through a nasal or face mask and a standard ventilator allows the physician to set the inspired oxygen concentration, prevent the rebreathing of exhaled gas, and use the ventilator monitors and alarms NonInvasive Positive-Pressure Ventilation

NonInvasive Positive-Pressure Ventilation:

Bilevel PAP ventilators : They provide continuous high-flow PAP that cycles between a high positive pressure and a lower positive pressure. In the spontaneous mode, bilevel PAP responds to the patient’s own flow rates and cycles between higher pressure (inhalation) and lower pressure (exhalation). When inspiration is detected, the higher pressure is delivered for a fixed time or until the flow rate falls below a threshold level. The spontaneous mode of bilevel PAP is similar in concept to Pressure-Support ventilation. NonInvasive Positive-Pressure Ventilation

NonInvasive Positive-Pressure Ventilation:

BIPAP=IPAP + EPAP EPAP = PEEP; IPAP= PEEP + PS ie) a Bilevel PAP setting of 12 cm of water for inspiratory pressure and 5 cm of water for expiratory pressure is equivalent to a standard ventilator setting of 7 cm of water for pressure support and 5 cm of water for PEEP. Inspiratory pressure increases tidal volume  PaCO 2  PaO 2  work of breathing and fatigue NonInvasive Positive-Pressure Ventilation

NonInvasive Positive-Pressure Ventilation:

Continuous positive airway pressure (CPAP ) : It is not a true ventilator mode as it does not actively assist inspiration. CPAP by nasal mask requires --- High flow oxygen + PEEP Raises FRC away from residual volume Splints alveoli open:  work of breathing  PaO 2 Re-expand atelectasis (opens collapsed alveoli) Helps resolution of pulmonary oedema (Reduces left ventricular transmural pressure therefore increases cardiac output). Pressures are usually limited to 5-12 cm of H2O, since higher pressure tends to result in gastric distension requiring continual aspiration through nasogastric tube NonInvasive Positive-Pressure Ventilation

NonInvasive Positive-Pressure Ventilation:

MODES OF NONINVASIVE POSITIVE PRESSURE VENTILATION 1. Volume mechanical ventilation Usually breaths of 250–500 ml (4–8 ml/kg).Pressures vary 2. Pressure mechanical ventilation Usually pressure support or pressure control at 8–20 cm of water End-expiratory pressure of 0–6 cm of water. Volumes vary 3. Bilevel positive airway pressure (bilevel PAP) Usually inspiratory pressure of 6–14 cm of water and expiratory pressure of 3-5cm of water . Volumes vary 4. Continuous positive airway pressure (CPAP) Usually 5–12 cm of water Constant pressure. Volumes vary NonInvasive Positive-Pressure Ventilation

Mechanism of Action of NPPV:

Improvement in pulmonary mechanics and oxygenation : NPPV augments alveolar ventilation and allows oxygenation without raising PaCO2  . It reduces respiratory muscles work and diaphragmatic electromyographic activity . Tidal volume, RR and MV . PEEP decreases the work of breathing by partially overcoming the auto-PEEP . Resetting of respiratory centre ventilatory responses to PaCO2 : By maintaining lower nocturnal PaCO2 during sleep by giving NPPV, it is possible to reset the respiratory control centre to become more responsive to an increased PaCO2 by increasing the neural output to diaphragm and other respiratory muscles. Mechanism of Action of NPPV

Advantages of NPPV:

Preservation of airway defense mechanism Early ventilatory support: an option Intermittent ventilation possible Patient can eat, drink and communicate Ease of application and removal Patient can cooperate with physiotherapy Improved patient comfort Reduced need for sedation Avoidance of complications of endotracheal intubation: upper airway trauma, sinusitis, otitis , nosocomial pneumonia Ventilation outside hospital possible Correction of hypoxaemia without worsening hypercarbia Ease to teach paramedics and nurses Advantages of NPPV

Disadvantages of nppv:

Mask uncomfortable/claustrophobia Facial pressure sores (skin necrosis) Airway not protected No direct access to bronchial tree for suction if secretions are excessive Gastric distension Drying of Eyes Gas leaks Ventilator-patient asynchrony Disadvantages of nppv

Indications of NPPV ::

Acute respiratory failure 1.Hypercapnic acute respiratory failure Acute exacerbation of COPD Post extubation Weaning difficulties Post surgical respiratory failure Thoracic wall deformities Cystic fibrosis Status asthmaticus Acute respiratory failure in Obesity hypoventilation Indications of NPPV :

Indications of NPPV:

2.Hypoxaemic acute respiratory failure Cardiogenic pulmonary oedema Community acquired pneumonia Post traumatic respiratory failure ARDS Weaning difficulties (B) Chronic Respiratory Failure (C) Immunocompromised Patients (D) Do Not Intubate Patients Indications of NPPV

Selection Criteria:

(A) Acute Respiratory Failure At least two of the following criteria should be present: Respiratory distress with dyspnoea Use of accessory muscles of respiration Abdominal paradox Respiratory rate >25/min ABG shows pH <7.35 or PaCO2 >45mmHg or PaO2/FiO2 <200 Selection Criteria

Selection Criteria:

(B)Chronic Respiratory Failure (Obstructive lung disease) Fatigue, hypersomnolence , dyspnoea ABG shows pH <7.35, PaCO2 >55 mmHg, PaCO2 50-54 mmHg Oxygen saturation <88% for >10% of monitoring time despite O2 supplementation (C) Thoracic Restrictive/ Cerebral Hypoventilation Diseases Fatigue, morning headache, hypersomnolance , nightmares, enuresis, dyspnoea ABG shows PaCO2 >45mmHg Nocturnal SaO2 <90% for more than 5 minutes sustained . Selection Criteria

Contraindications: :

Contraindications : Relative Contraindications Extreme anxiety Massive obesity Copious secretions Failure of previous attempts of NPPV Life threatening arrhythmias Life threatenting refractory hypoxemia(PaO2<60mm Hg with FiO2- 1.0%) Absolute : Respiratory arrest Unstable cardiorespiratory status Uncooperative patients Unable to protect airway- impaired swallowing and cough Facial Oesophageal or gastric surgery Craniofacial trauma/burn Anatomic lesions of upper airway

Factors predictive of success :

Younger age Lower acuity of illness (ie, acute physiology and chronic health evaluation [APACHE] score) Patient able to cooperate Ability to coordinate breathing with ventilator Moderate hypercapnia (PaCO 2 >45 mm Hg but <92 mm Hg) Moderate acidemia (pH >7.10 but <7.35) Improvement in gas exchange and heart and respiratory rates within first 2 hours Factors predictive of success

Interfaces: Devices that connect ventilator tubing to the face allowing the entry of pressurized gas to the upper airway:

Interfaces : Devices that connect ventilator tubing to the face allowing the entry of pressurized gas to the upper airway Types -Face masks,nasal masks,Helmet,nasal pillows, Mouth pieces. Nasal masks less dead space less claustrophobia allow for expectoration vomiting and oral intake Used more often in Chronic respiratory failure Facial mask (enclose mouth & nose) dyspnoeic patients are usually mouth breathers More dead space

Helmet vs facial mask:

Complications (skin necrosis, gastric distension, and eye irritation) were fewer with helmet Allowed prolonged continuous application of NIV Length of stay in ICU, intubation rates, mortality similar Helmet vs facial mask (Intensive Care Med. 2003;29 Crit Care Med. 2002;30 Chest. 2004;126)

Controlled trial of oronasal vs nasal mask in the treatment of acuterespiratory failure :

35 pts oronasal (ON) vs 35 pts nasal (N) Most patients had COPD or CHF Mask intolerance: 34 % (N) vs 11 % (ON) Major reason: mouth leak (ventilator asynchrony) Trend towards lower success in (N) group Equally successful in normalizing physiology (Kwok H et al Crit Care Med 2003;31:468-473) Controlled trial of oronasal vs nasal mask in the treatment of acuterespiratory failure

Who can administer NIV?:

Physicians, nurses, or respiratory care therapists, Depends on staff experience and availability of resources for monitoring, and managing complications For the first few hours, one-to-one monitoring by a skilled and experienced nurse, respiratory therapist, or physician is mandatory. Immediate access to staff skilled in invasive airway management. Who can administer NIV?

Clinical trials supporting the use of NPPV :

A. Patients with COPD exacerbation : 1 A large randomized trial ( Brochard , 1995) NPPV vs Standard ICU approach, Use of NPPV was shown to reduce complications, the duration of ICU stay, and mortality. Patients in whom NPPV failed had a similar Mortality rate compared to the intubated group (25% vs 30%). 2 . Plant and colleagues recently published the largest prospective randomized study NPPV vs Standard treatment Treatment failed in significantly more patients compared to the control group (27% vs 15%); In-hospital mortality rates were significantly reduced from the use of NPPV (20% to 10%). Clinical trials supporting the use of NPPV

Clinical trials supporting the use of NPPV :

3. Cochrane Systematic Review : efficacy of NPPV in the management of patients with respiratory failure due to an acute exacerbation of COPD. Fourteen studies were included in the review. RESULTS : Decreased mortality (relative risk [RR] 0.52), Decreased need for intubation (RR 0.41), Reduction in treatment failure (RR 0.48) . Complications associated with treatment (RR 0.38) and length of hospital stay (mean, 3.24 d) was also reduced in the NPPV group Clinical trials supporting the use of NPPV

Clinical trials supporting the use of NPPV :

B. Acute pulmonary edema : In a controlled study,( Nasal bilevel PAP vs Nasal CPAP ) Nasal bilevel PAP (inspiratory and expiratory pressures of 15 and 5 cm of water, respectively) improved the partial pressure of arterial carbon dioxide, pH, respiratory rate, and dyspnea more rapidly than nasal CPAP (10 cm of water) in patients with acute pulmonary edema. However , Bilevel-PAP group had a more rapid fall in blood pressure and a higher rate of myocardial infarction (71 percent vs 31 percent), causing concern about the use of this (BiPAP)therapy for acute pulmonary edema . ( Mehta S, Jay GD, Woolard RH, et al. Randomized, prospective trial of bilevel versus continuous positive airway pressure in acute pulmonary edema. Crit Care Med 1997;25:620-8.) Clinical trials supporting the use of NPPV

Clinical trials supporting the use of NPPV :

Concusion : Nocturnal noninvasive CPAP therapy in patients with chronic congestive heart failure and sleep-related breathing disturbances reduces the frequency of apnea, improves nocturnal oxygenation, improves symptoms of heart failure, improves the left ventricular ejection fraction and decreases sympathetic nervous activity Clinical trials supporting the use of NPPV ( Mehta S, Jay GD, Woolard RH, et al. Randomized, prospective trial of bilevel versus continuous positive airway pressure in acute pulmonary edema. Crit Care Med 1997;25:620-8.)

Future of NPPV:

Reducing the incidence of infection ICU & Hospital length of stay Reduction in Cost & Mortality rate Latest mode of ventilation : (Proportional Assist Ventilation) In this mode ,ventilator has capacity of responding rapidly to the patients' ventilatory efforts. By adjusting the gain on the flow and volume signals, one can select the proportion of breathing work that is to be assisted. Future of NPPV

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