Non Invasive Ventilation

1. Dr. umamaheshwara rao
Dept. of Anaesthesiology
&
Critical Care Medicine.

2. 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

3. 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

4. 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.

5. 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

6. 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.

8. 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.

9. 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

10. 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

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

13. 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 .

14. 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

15. 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.)

16. 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

17. 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.)

18. 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

19. 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.

20. 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
ο ↓ PaCO2
ο ↑ PaO2
ο ↓ work of breathing and fatigue

21. 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
↑ PaO2
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

22. 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

23.  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.

24. 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

25. 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

26. (A) 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

27. 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

28. (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

29. (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 .

30. 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:
1.Respiratory arrest
2.Unstable cardiorespiratory
status
3.Uncooperative patients
4.Unable to protect airway-
impaired swallowing and
cough
5.Facial Oesophageal or
gastric surgery
6.Craniofacial trauma/burn
7.Anatomic lesions of upper
airway

31. 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 (PaCO2 >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

32. 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

33.  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
(Intensive Care Med. 2003;29 Crit Care Med. 2002;30 Chest. 2004;126)

34. 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)

35. 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.

36. 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%).

37. 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

38. 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.)

39. 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
(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.)

40. 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.

43. THAnK You