Non Invasive Ventilation

NIV is application of positive pressure ventilation without the use of a definitive airway such as endotracheal (ET) tube or Tracheostomy which preserves the patient’s ability to speak, eat, maintains cough reflex, reduces the need for sedation, avoids potential airway trauma and reduces the risk of nosocomial pneumonia

Mechanism of beneficial effects

      • Reduced work of breathing and avoidance of fatigue
      • Rest for the respiratory musculature
      • Improved alveolar ventilation
      • Auto-PEEP (positive end expiratory pressure ) that occurs in COPD (Chronic obstructive lung disease) is offset
      • Improvement in expired tidal volume
      • Reversal of microatelectasis leading to improved respiratory system compliance
      • Reduction in ventilation-perfusion mismatch as in pulmonary edema
      • Reduced mortality due to,
        • Decreased hospital-acquired infections
        • Decreased trauma from intubation
        • Less complications of sedation

Advantages of NIV

      • Noninvasiveness
        • Application to patient (as compared with endotracheal intubation)
          • Easy to implement
          • Easy to remove, allows intermittent application
        • Improves patient comfort
        • Reduces the need for sedation
        • Oral patency (preserves speech, swallowing, and cough, reduces the need for nasoenteric tubes)
      • Avoid the resistive work imposed by the endotracheal tube
      • Avoids the complications of endotracheal intubation
        • Early (local trauma, aspiration)
        • Late (injury to the hypopharynx, larynx, and trachea, nosocomial infections)

Disadvantages of NIV, compared to endotracheal intubation

  • System
    • Slower correction of gas exchange abnormalities
    • Increased initial time commitment
    • Gastric distension (occurs in <2% patients)
  • Mask
    • Air leakage
    • Transient hypoxemia from accidental removal
    • Eye irritation
    • Facial skin necrosis –most common complication.
  • Lack of airway access and protection
    • Suctioning of secretions
    • aspiration
Figure 1: Normal airway vs Narrowed airway due to secretions

Figure 1: Normal airway vs Narrowed airway due to secretions

  • Management of Acute Respiratory failure
  • Exacerbation of COPD
  • Post operative
  • Respiratory failure in patients with obstructive sleep apnoea (OSA)
  • Hypoxemic respiratory failure
  • Acute cardiogenic pulmonary edema


2) Management of acute severe asthma

3) To facilitate extubation in

  • COPD
  • Difficult to wean patients
  • Immunocompromised patients to prevent pneumonia


4) “Do-Not-Intubate” Patients

Many applications of NIV have been tried in the critical care setting, but as of yet, only four indications are supported by multiple randomized controlled trials and meta-analyses.

  • COPD exacerbations
  • Acute cardiogenic pulmonary edema
  • Facilitating Extubation in COPD Patients
  • Immunocompromised Patients

Individual clinical conditions:


  • Unloading of the respiratory muscles
  • Improving alveolar ventilation and reducing PaCO2
  • NIV reduces the rate of ETI, length of stay and mortality*
  • Up to 20% of patients with a COPD exacerbation are candidates for NIV
  • The mortality from a COPD admission is approximately 25-30%, and most of them are from complications of ETI and mechanical ventilation**
  • Up to 20% of the mechanically ventilated COPD patients are difficult to wean
* Kramer N. Am J Respir Crit Care Med 1995; 151: 1799–1806

** Bott J. Lancet 1993; 341:1555–1557



  • NIV results in rapid pH correction at 1 hour, correction of respiratory rate (RR) at 4 hours, and a trend for pCO2 improvement at 4 hours *
  • Breathlessness also gets relieved faster with NIV
  • Decrease in the intubation rates (from 74% to 25%) and mortality (25% to 9%) with the use of NIV **
  • NIV also resulted in a reduction in complications and length of stay

NIV should be tried first and promptly, unless there is an obvious indication for immediate ETI and mechanical ventilation

* Plant PK. Lancet 2000; 355:1931–1935

** Celikel T. Chest 1998; 114:1636–642

Extubation in COPD patients

  • Candidates who are unable to pass a T-piece trial even though they have improved sufficiently can be given a trial of NIV.
  • Studies observed that NIV-treated patients had shorter durations of intubation and ICU and hospital stays, decreased incidence of nosocomial pneumonia, and improved ICU and 90-day survivals. *

* Ferrer M. Am J Respir Crit Care Med 2003; 168:70–76

2) Congestive heart failure and Acute pulmonary edema

  • Strong evidence supports the use of NIPPV to treat acute cardiogenic pulmonary edema. *
  • The need for ETI was reduced from 35% to 0% by the use of CPAP (Continuous positive airway pressure)
  • A study comparing the use of Bilevel positive airway pressure (BiPAP), CPAP, and a historical controls in pulmonary edema showed a higher rate of AMI in the BiPAP group (71%, 31%, and 38%, respectively)**
  • Until more evidence arises showing the safety of BiPAP in acute pulmonary edema, CPAP should be the preferred mode of NIV for this group.

* Park M. Crit Care Med 2004; 32:2407–2415

** Nava S. Am J Respir Crit Care Med 2003; 168:1432–1437

3) Immunocompromised Patients

  • The use of NIV is also well supported for immunocompromised patients who are at high risk for infectious complications from ETI, such as those with hematologic malignancies, AIDS, or following solid-organ or bone marrow transplant (BMT)
  • In a randomized trial of patients with hypoxemic respiratory failure following solid-organ transplantation, NIV use decreased intubation rate (20% vs 70%, p<0.002) and ICU mortality (20% vs 50%, p = 0.05) compared with conventional therapy with oxygen.*

* Antonelli M. JAMA 2000; 283:2239–2240

  • Clinical Criteria for initation of NIV
  • pH < 7.35 with PaCO2 > 45 mmHg
  • PaO2/ FiO2 < 300 or SpO2 < 92% with FiO25
  • Respiratory Rate > 25 bpm
  • Respiratory Distress with
    • Moderate to severe dyspnea
    • Use of accessory muscles
    • Abdominal paradox


  • Intact protective reflexes
  • Conscious patient
  • Patient cooperation – proper counselling is required
  • Low/no risk of aspiration
  • Appropriate type and size of NIV mask



Who should not be considered for NPPV? – When patient is too sick or can’t protect Airway

  • Cardiac or respiratory arrest
  • Non-respiratory organ failure
  • Hemodynamic instability
  • Severe encephalopathy
  • Facial or neurosurgery, trauma
  • Upper airway obstruction
  • Inability to protect airway
  • High risk for aspiration e.g. Excessive secretions, Severe UGI bleed
  • Un co-operative or agitated patients
  • Poor mask fit
  • Untreated Pneumothorax

Location of NIV

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

Who can administer NIV?

  • Trained anesthesiologists, emergency physicians, intensivists, 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.


Pressure Support (PS), BiPAP, CPAP, PAV (Proportional Assist Ventilation) are various modes used for NIV. Change the ventilator settings to Non Invasive mode if available.

  • CPAP (continuous positive airway pressure ventilation)

– Improve oxygenation by recruiting collapsed alveoli.

  • BiPAP (bilevel positive airway pressure ventilation)

– A boost of pressure during inspiration

– Pressure support (IPAP – EPAP)

IPAP assists in improving TV

EPAP helps recruit more alveoli

  • Differential in pressure between inspiration and expiration allows for better patient-ventilator synchrony and thus more comfort

Figure 2: Waveforms – Spontaneous, CPAP, BiPAP

  • PAV (Proportional Assist Ventilation)

This is a newer mode of ventilation, wherein the ventilator has the capacity to respond rapidly to the patients’ ventilatory efforts. By adjusting the gain on the flow and volume signals, the clinician sets the percentage of work of breathing to be provided by the ventilator. A positive feedback loop (requires calculation of resistance and elastance) is used to accomplish this. The theoretical advantage of PAV is increased synchrony compared to PSV (which provides the same amount of support regardless of how much effort the patient makes)

NIV   masks / Interfaces


Figure 3: Full Face Mask


Figure 4: Full face NIV Mask attached on patient


Figure 5: Helmet


Figure 6: Total Face Mask


Figure 7: Nasal Mask


Figure 8: Nasal Mask on patient


Figure 9: Nasal Pillows


Nasal Mask

  • More air leaks
  • Requires a co-operative patient who can keep a closed mouth
  • More comfortable for Claustrophobic patients
  • Correct size can be picked up via a template (Fig 10)

Figure 10: Template for correct sizing

Full Face Mask (Fig 3, 4)

  • Delivers higher ventilation pressures without leaks
  • Allows for mouth breathing, requires less patient co-operation
  • Less comfortable, impedes speech, and limits oral intake


Helmet (Fig 5)

  • Complications of Face Mask like skin necrosis, gastric distention and eye irritation were fewer
  • Allows prolonged continuous application of NIV


Nasal Pillows (Fig 9)

  • Lightweight, unobtrusive and designed to keep the field of vision clear
  • Fits snugly over the nostrils
  • Appropriate for home therapy eg. sleep apnea


  • Appropriate environment for NIV – Ward vs Critical Care Unit
    • Readiness for Intubation with equipment should be present if NIV fails
  • Non Invasive Ventilator with tubings
  • Range of full face and Nasal masks with sizing devices
  • Exhalation valve/ port
  • Heat and Moisture exchanger with Microbiological filter
  • Head gear
  • Skin necrosis patches (Fig 11)

NIV12Figure 11: Skin protection foam and gel sheet


  • Sterile wipes to disinfect masks before use
  • Key points
    • Ventilator entrains air
    • Oxygen needs to be entrained into circuit.
    • Advanced ventilators may provide variable oxygen and need to be connected to wall oxygen source
    • Put together circuit and attach to ventilator
    • Check for position/function of exhalation port

Application to patient:

  • Patient sitting in upright position
  • Explain to patient what will happen
  • Apply face mask without straps at first
  • Allow patient to get used to machine and then apply straps
  • Assess mask fit and leak by using hand to feel for air escaping around mask.
  • Observe that each patient effort is synchronised to ventilator breaths
  • Recognise ventilation cycle by sound from exhalation port or by observing pressure gauge/waveform.
  • Poor synchronisation usually due to incorrect mask fit with excessive leak.
  • If inspiratory time pre-set ensure that it matches patient efforts


Initiating NIV

  • Once a decision has been made to initiate NIV, the mode of ventilation should be selected
  • Use the CPAP if the main problem is hypoxemia
  • Favor BiPAP if the main problem is hypercarbia
  • Hold the mask in place without securing it at first
  • Once synchrony is achieved, secure the mask with straps, avoiding a tight fit
  • Initiation of Therapy
  • The initial NIV parameters should provide a pressure support of 5 cmH2O for CPAP
  • Start BiPAP with an IPAP of 8-10 cmH2O

EPAP of 3-5 cmH2O

settings on ventilator

Figure 12: Settings on the Ventilator

  • Increase these parameters gradually, usually by 2 cmH2O at a time, until an exhaled tidal volume of 5-10 mL/Kg is achieved and respiratory rate falls below 25/min
  • At Initiation of therapy
    • Adequate monitoring of patients includes closely following the vital signs, cardiac monitoring, and pulse oximeter
    • Perform serial clinical examinations that include patient comfort with device, mental status, work of breathing, and handling of secretions
    • The ABG measurements are useful tool to assess the adequacy of treatment

First hour……..

  • Titrate settings and FiO2
  • Aim to reduce work of breathing /RR
  • Assist patient comfort and tolerate mask
  • Minimal sedation may be used – Dexmedetomidine, Fentanyl, Morphine
  • Monitor mental status
  • Intubate if worsening
  • Keep patient NPO!
  • Check ABGs in 1-2 hours
  • Check ABG after one hour
    • If pH and PaCO2 improving, continue with current settings
    • Increase IPAP if pH and PaCO2 not improving
    • Titrate oxygen for SaO2 to 88% -92%
    • EPAP can also be increased to improve SaO2
    • Usually those patients who respond to NIV will have significant improvement in ABG in first 1-2 hours.
    • ABG recommendations are at 1h, 2h, 4h and 12 h.
    • Continuous pulse oximetry, ECG,HR,BP, sensorium

Initial assessment

  • Patients who benefit from NIV have improvements of the dyspnea and of the signs of respiratory distress.
  • These changes can be seen as early as one hour after the initiation of NIV
  • A rapid decrease in the respiratory rate is a very good indicator of successful treatment
  • Level of consciousness, oxygen saturation, and the ABGs
  • Predictors of NIV success
    • Younger age / good dentition
    • Lower acuity of illness / normal mental status
    • Able to cooperate
    • Less air leaking
    • Moderate hypercarbia (46-91 mm Hg)
    • Moderate academia (pH 7.11-7.34)
    • Improvements of gas exchange and vitals within 2 hours
    • Coma has been considered a contraindication to NIV in the past, but a study, observed a high success rate of NIV in patients with hypercapnic coma.*

      Factors associated with success

  • Synchronous breathing with ventilator
  • Less air leaking
  • Fewer secretions
  • Good tolerance
  • RR < 30/ min
  • Lower APACHE score < 29
  • pH > 7.30
  • Glasgow Coma score 15
  • PaO2 / FiO2 > 146 after 1st hour if hypoxemic respiratory failure COPD
  • Best predictor of success is a good response to NIV within 1 – 2 hrs:
    • Reduction in RR
    • Improvement in pH
    • Improvement in oxygenation
    • Reduction in PaCO2
  • Indicators of NIV failure
    • patient intolerance for NIV
    • failure to improve after 1-2 hours in NIV
    • progressive confusion or sedation
    • inability to handle secretions
    • chest pain
    • arrhythmia
    • apnea
  • Complications of NIV
    • Dys-synchrony between patient and the ventilator
    • Pressure necrosis over the skin at the mask interface
    • Gastric distension
    • Claustrophobia
    • Barotrauma
    • Aerophagia
    • Airway dryness
    • Discomfort

Problems are minimized and managed by

  • Careful patient selection
  • Proper mask fit
  • Patient counselling and reassurance
  • Humidification and hydration
  • Anti emetics
  • Proper ventilators settings: pressure limit, I:E ratio, PEEP etc
  • Gastric drainage
  • Dermatological consultation
  • Change over to invasive ventilation


Examples of Cases

Patient 1

65 year old smoker and known case of COPD, presented with acute onset of breathlessness. His vitals on presentation were stable, except BP of 160/110 mm of Hg and RR of 35. Blood gases wereàpH 7.29, pCaO2 à 89, pO2 à 74 . O/E, he had tachycardia and rhonchi bilaterally.

Patient recovered with non invasive ventilation. BiPAP settings: PS = 14, Rate = 14/ min, Insp time = 1.2 sec, FiO2 = 40%. Supportive management with Nebulization was started; NIV was required for 3 days and patient improved.

Patient 2

45 year old male, admitted with high grade fever with chills and rigors. Cough and yellowish expectoration. High counts and X-rays showing lobar pneumonia. O/E, tachypnea (RR = 35), tachycardia, diaphoretic but BP is normal. ABG showing ph 7.45, PaCO2 à 22, PaO2à 57.

Patient initiated on appropriate antibiotics and non invasive ventilation. Settings PS = 15, PEEP = 7, Rate = 18/ min, FiO2 = 50%, Insp time = 1.5 sec. Further settings adjusted to keep SpO2 ≥ 94%.

Patient 3

22 year old female, 9 months amenorrhoea, pedal edema, BPà 210/100 mm of Hg, Xray showing congestion and echo showing normal systolic functions functions and grade II diastolic dysfunction. ABG showed respiratory alkalosis. Diuretics and non invasive ventilation with preload and after load reduction with appropriate drugs (Nifedipine, ACE Inhibitor).

Patient 4

40 year old with P falciparum malaria, fluid overloaded. Developed breathlessness on 3rd day of treatment. Xray showing fluffy shadows and ABG s/o ARDS. With ph of 7.32, Paco2 of 66 and Pao2 of 60, stable hemodynamics he was initiated on non invasive ventilation. Recovered along with fluid restriction and non invasive ventilation.

Patient 5

67 year old with chronic bronchitis, admnitted for surgery of the tibial fracture. Intubated and was not extubated post surgery due to hypoxia. In ICU, when GCS improved, patient was extubated and given a trial of non invasive ventilation for purpose of avoiding ventilatory dependency and early weaning.

Patient 6

Male 65 year old patient, Diabetic since 20 years and with diabetic nephropathy. Echo s/o ischemic cardiomyopathy. Comes with acute breathlessness. o/e patient is oedematous and auscultation reveals bilateral rales. ABG shows alkalosis respiratory with hypoxia. BP 90 mm of Hg. Patient was treated with dobutamine infusion and non invasive ventilation. Diuretics were avoided.

Patient 7

Male patient, aged 30 years, underwent a road traffic accident diagnosed to have Rt sided multiple # ribs with underlying lung contusion. ABG showed only hypoxia not getting corrected by o2 via nasal prongs. Patient unable to perform incentive spirometry due to pain. Patient put on non invasive ventilation and epidural analgesic for pain relief.

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