Noninvasive Positive Pressure Ventilation (NIV) Dr. SamirSahu, Intensivist, Kalinga Hospital, Bhubaneswar.
Aim of Ventilation • To support the overloaded ventilatory pump • To improve arterial blood gases & pH • To relieve dyspnea & unload the respiratory muscles • To buy time for the patient until the causes of exacerbation are resolved by medical therapy
NIV Noninvasive Ventilation means augmenting Alveolar Ventilation without endotracheal tube or tracheostomy tube. It consists of a Nasal or a Facial Mask It can be used in the Casualty, ICU, Ward for Acute RF or at Home for Chronic RF. Avoids intubation & VAP
Indication for Noninvasive Ventilatory Support Depends on • Severity of Exacerbation • Severity of Respiratory Acidosis • Timing of Intervention • Patient Characteristics • Skill of the Team • Available monitoring facilities
Indications of NIV Hypercapnic Acute Respiratory Failure • Acute exacerbation of COPD • Thoracic Wall Deformities • Neuromuscular Diseases • Weaning Hypoxaemic Acute Respiratory Failure • Cardiogenic Pulmonary Oedema Chronic Respiratory Failure • Polio,TB,NMD,KS,COPD,Bronchiectasis.
NIV in AE of COPD A meta-analysis of 15 trials found that adding NPPV to standard care reduced rates of endotracheal intubation, length of hospital stay & in-hospital mortality rates in patients with severe exacerbations. (Worsening dyspnoea, increase in sputum purulence, increase in sputum volume) Keenan et al;Ann Intern Med. 2003
COPD • Acute exacerbation (pH<7.35, PaCO2>45 • Mild exacerbations (pH>7.35) may not benefit Keenan et al, 2003 • Can be used in ICU/HDU/Wards, Patients with severe exacerbations (pH<7.3) are better managed in the ICU
COPD • Recent studies demonstrate that outcomes of severe COPD exacerbations are no worse if treated with NIV than with endotracheal intubation, indicating that an initial trial with NIV is not deleterious, even in severely ill COPD patients. Scala R et al, Chest 2005 Conti G et al, Intensive Care Med 2002
COPD – Practice points • All AE-COPD should have ABG on presentation besides clinical examination • NIV preferably started in ICU • Patients closely monitored during first 1-2 hours • ABG should be repeated at end of 1-4 hrs • NIV should be given almost continuously in first 24 hours except during feeding. Later on duration can be reduced depending on clinical condition & physiological parameter(SpO2,ABG)
Neuromuscular Disease/Chest wall Deformity • NIV is recommended when they present in Acute-on chronic respiratory failure
Acute Asthma • Not recommended for routine use in Asthma exacerbation • NIV may be tried in ICU in patients of Acute Severe Asthma who fail to respond quickly to medical treatment & have no contraindication • Patients should be monitored closely and intubated promptly if there is no improvement in the first hour or two, because these patients can deteriorate rapidly.
Obstructive Sleep Apnea • CPAP/NIV is recommended for Obstructive Sleep Apnea presenting as acute respiratory failure • NIV is recommended for patients of Obesity Hypoventilation Syndrome with acute respiratory failure
Interstitial Lung Diseases • NIV is not recommended for Interstitial Lung Disease with acute or chronic respiratory failure
Cardiogenic Pulmonary Edema • CPAP/NIV are recommended in addition to standard medical treatment in cardiogenic pulmonary edema • CPAP/NIV are equally effective in cardiogenic pulmonary edema • NIV is preferable in patients associated with hypercapnic respiratory failure
Cardiogenic Pulmonary Edema • The main physiologic benefit from NIV or CPAP in these patients is likely due to an increase in functional residual capacity that reopens collapsed alveoli and improves oxygenation. This also increases lung compliance and reduces work of breathing. The increased intrathoracic pressure also can improve cardiac performance by decreasing ventricular preload and afterload.
Immunosupressed Patients • NIV is recommended early in the course of hypoxic respiratory failure in immunocompromised patients, particularly in those with hematological malignancies • NIV as the preferred initial ventilatory modality for these patients (solid organ & bone marrow transplants, HIV) to avoid intubation and its associated risks.
Lung Resection/Abdominal Surgery • NIV may be used in patients who develop respiratory failure after lung resection or abdominal surgery
Severe Community Acquired Pneumonia • NIV may be used in the ICU with caution in selected patients with community acquired pneumonia particularly in those associated with COPD • A cautious trial of NIV may be considered in patients with pneumonia deemed to be excellent candidates, but they need careful monitoring, because the risk of failure is high.
ARDS • NIV may be used with great caution in cases of Acute Lung Injury & that too only in ICU. • Reserved for hemodynamically stable patient who can be closely monitored in an ICU where facilities for invasive ventilation are present
ARDS • Independent risk factors for NIV failure include severe hypoxemia, shock, and metabolic acidosis. • Those with > 2 organ failures, hemodynamic instability, or encephalopathy were excluded • Predictors of NIV failure were Simplified Acute Physiology Score II > 34 and Pao2/Fio2 ≤ 175 after the first hour of therapy. • NIV cannot be recommended as routine therapy for ALI/ARDS, a cautious trial in highly selected patients with a Simplified Acute Physiology Score II ≤ 34 and readiness to promptly intubate if oxygenation fails to improve sufficiently within the first hour. Rana S. Crit Care 2006, Antonelli M. Crit Care Med 2007
Trauma • CPAP/NIV can be recommended for hemodynamically stable patients of chest trauma with flail chest
Palliative Care & Do not Intubate Patients • NIV offers an effective, comfortable & dignified method of supporting patients with end stage disease & acute respiratory failure • If the patient and/or family desire prolonged survival, then use should be reserved primarily for COPD and congestive heart failure patients. • On the other hand, if the goal is to palliate, to relieve dyspnea, or to delay death so that affairs can be settled, then NIV can be used for these as well as other diagnoses. • However, it should be reassessed frequently and stopped if the goal of palliation is not being met.
Hypoxemic Respiratory Failure Practice Points • Preferably Full-face mask during acute phase • Preferably ICU Ventilator as a high FiO2 can be administered • Pressure support with PEEP with fast rise time high inspiratory flow to compensate for air leaks • NIV should be discontinued if no improvement in gas exchange & dyspnea, significant mouth leak, severe mask intolerance, no improvement in mental status in 30 min in a agitated hypoxemic patient
Postextubation Respiratory Failure • Support the use of NIV in patients at high risk of extubation failure, particularly if they have COPD, congestive heart failure, and/or hypercapnia. However, early indiscriminate use in all patients with risk factors is discouraged. Patients with extubation failure treated with NIV should be monitored closely and delays in needed intubation avoided
Facilitating Extubation in COPD • Patients intubated for hypercapnic respiratory failure due to COPD who fail spontaneous breathing trials should be considered for a trial of extubation to NIV. This approach should be reserved for patients who are good candidates for NIV in other respects and who are able to tolerate levels of pressure support easily administered via mask (i.e., ≤ 15 cm H2O). In addition, they should not have been a difficult intubation.
Ventilation in COPD • Non Invasive Ventilation • Invasive Ventilation as rescue intervention • Invasive Ventilation as first choice • NIV to speed up liberation from ventilation
Weaning – Practice Points • SBT after at least 48hrs of stabilization with invasive ventilation • If SBT successful – extubate • If SBT fails then stabilize patient with full support on MV for 1 hr • After stabilization extubate & start NIV • Initially apply NIV continuously(22-24hrs) with discontinuation for feeding, expectoration • Gradually reduce time on NIV as per patients improvement
Preoxygenation Before Intubation • Critically ill patients with hypoxic respiratory failure are at high risk of oxygen desaturations during intubation. A recent RCT of such patients showed that preoxygenation with NIV before intubation resulted in improved oxygen saturation during and after intubation and decreased the incidence of oxygen desaturations below 80% during intubation. This approach is promising but should be further studied before routine use can be recommended. Baillard C. Am J RespirCrit Care Med 2006
Selection Criteria for NPPV Acute Respiratory Failure • Respiratory Distress (moderate to severe dyspnoea, use of accessory muscles, abdominal paradox) • Respiratory Rate (>25/min hypercapnic, >30 hypoxemic) • pH <7.35 & PaCO2 >45mm Hg Any 2 of the above • PaO2 <60mm Hg (SpO2 <90%), P/F <200
Exclusion Criteria for NIV • Cardiac or Respiratory Arrest • Haemodynamic Instability - Hypotension • Cannot protect airways - Coma, secretions • Craniofacial Trauma (unable to fit mask) • Life threatening hypoxia • Copious secretions • Severe GI symptoms (vomiting, obstruction, recent upper GI & airway surgery)) • More than 2 organ failure • Extreme Obesity • Agitated or Uncooperative
NIV - Apparatus • Bilevel Pressure Support Ventilator (portable)/ ICU Ventilator • Silicon Bubble cushion Nasal mask • Silicon Full Face mask (better in acute RF) • Interface is crucial to success of NIV • Head gear • Oxygen supplementation
Equipment • Pressure preset is now the predominant mode used in NIV • EPAP – flushes dead space CO2, helps alveolar recruitment, stabilizes upper airway during sleep • Trigger – flow trigger is better • Cycling – Inspiratory time 1-0.8sec
Initiation of NIV • Appropriately monitored location(SpO2, Vitals) • Patient > 30o angle • Select Interface (mask), Select Ventilator • Apply Headgear ,Connect interface to ventilator tubing & turn on ventilator • Start IPAP 8-12 & EPAP 3-5 cm H2O • Gradually increase IPAP(10-20) to alleviate dyspnea, decrease RR (IPAP-EPAP>4) • Obese or OSA patients require higher EPAP • Provide O2 supplementation to keep O2 >90% • Check for air leaks, readjust straps as needed
Continuation of NIV • ABG at initiation & after 2hrs • If PCO2 decreases, pH increases & SpO2 is maintained continue treatment • Consider reduction in duration of NPPV • Light diet to avoid nausea & vomiting • Continue other medication The first few hours are Labour intensive Motivation, training,& dedication leads to success
Predictors of success of NPPV • Younger age • Lower acuity of illness (APACHE score) • Able to cooperate; better neurologic score • Able to coordinate breathing with ventilator • Less air leak; intact dentition • Less severe Hypercarbia (PCO2>45,<92) • Less severe Acidemia (pH<7.35,>7.10) • Improvements in gas exchange,HR,RR within 1-4 hours
Predictors of Failure - COPD • Air leaking • Apache II >29 • Asynchrony • Copious secretions • GCS <11 • Lack of compliance & tolerance • pH < 7.25 • Respiratory rate >35/min
Predictors of Failure – Hypoxemic Respiratory Failure • ALI/ARDS • SAPS >35 • Metabolic Acidosis • P/F <146 (<175 in ARDS) after 1 hr NIV • Pneumonia • Severe hypoxemia • Shock
Failure • Early Failure – 1-3 hrs • Late Failure – subsequent failure during hospital stay (>48hrs) • 20% of COPD AE experience a new episode of Res. Failure. Mortality is 91% with continued NIV compared to 52.6% in those who are intubated & ventilated • Mechanical Ventilation allow the patient to improve sufficiently to take advantage of NIV which was ineffective earlier
Predictors of NIV FAILURE • At admission – GCS <11 Apache II >29 RR >35/min pH <7.25 >50% if any 3 & 82% if all 4 • 2hr after NIV – 75% any 3 & 99% if all 4
What the Literature says • Early Failure – (1-3hrs) • Late Failure – (>48hrs) – 10-20% • Failure Rate – 5-40% • Second episode of ARF(same admn) – 20% (more severe disease) • Readmission after 1 year – 80% Life threatening – 63% Death – 49%
Monitoring of NIV • Subjective - Mask comfort - Tolerance of ventilator settings - Respiratory distress • Physical findings – Respiratory rate – Other vital signs – Accessory muscle use – Abdominal paradox • Ventilator parameters – Air leaking – Adequacy of Pressure support – Adequacy of PEEP – Tidal volume 5-7 ml/kg – Patient-ventilator synchrony
NIV Monitoring • Gas Exchange – Continuous oximetry until stable – ABGs baseline & 1-2 hrs, then as indicated • Location – Usually ICU to start – General Ward if stable – Depends on monitoring needs of patient & monitoring capabilities
Complications of NIV • Air Leaks • Nasal/Oral dryness • Mask discomfort • Gastric distention • Failure to Ventilate
Selection Criteria for NPPV Chronic Respiratory Failure - COPD • Failure of standard medical therapy (bronchodilators & LTOT) • Fatigue, Dyspnea, morning headache,etc (Symptomatic Diurnal Respiratory Failure) • PaCO2 > 55 mm Hg • PaCO2 50-55 mm Hg with Nocturnal desaturation