1) Asthma patients requiring mechanical ventilation (MV) have high airway resistance, dynamic hyperinflation, and high physiologic dead space. Non-invasive ventilation (NIV) may be tried in some patients but has a high failure rate. 2) Indications for intubation include respiratory arrest, decreased consciousness, and progressive fatigue. Rapid sequence intubation is preferred and may require high doses of sedatives due to severe airway obstruction. 3) Mortality rates for mechanically ventilated asthma range from 0-38% but most studies report average rates around 8%. Patients are at increased risk of fatal attacks in subsequent years.

1. Asthma On The
Machine
Waheed Shouman
Professorof ChestMedicine
Zagazig University

2. Leatherman. 201

3. Main physiologic abnormalities in ASA:
• High airway resistance
• Dynamic hyperinflation
• High physiologic dead space
• Auto-PEEP is usually 10 to 15 cm H2O but
may be higher

4. 23. Tuxen et al. 2000

6. Drug Treatment

9. Chan et al. Clinic Rev Allerg Immunol (2015) 48:45–53

10.  2% to 4% of patients who are hospitalized
for ASA will require MV
 MV for asthma is rare

11. NIV

12.  NIV in ASA is not well defined
 NIV in ARF due to ASA is level C evidence
 NIV may be limited to a minority of patients.
Pallin and Naughton. Journal of Critical Care 29 (2014) 586–593

13. NIV may be tried in absence of
contraindications
1. Altered consciousness,
2. Hemodynamic instability,
3. Excessive secretions,
4. Uncooperativeness
Leatherman . CHEST 2015; 147 ( 6 ): 1671 - 1680

14.  Despite the indications from most recent review that
NIV is safe, clinicians must remain cautious when
selecting candidates for NIV.
 Failure of NIV resulting in escalation to intubation and
mechanical ventilation can have serious effects on
the patient.
 It has previously been reported that the in-ICU
mortality rate for patients who required intubation due
to failed NIV was 36%.

15. NIV in ASA
Yes
No
Yes
No
Yes
No
Yes
No

16. IMV

17. Indications for intubation:
• Respiratory arrest
• Depressed level of consciousness
• Progressive fatigue
Hypercapnia itself is not an indication for
intubation as it may improve with medical
treatment or NIV

18. Kohn. Clin Allergy Immunol 1999;13:419-28

19. Intubation:
Rapid sequence intubation is preferred
If paralytics:
The most skilled operator is needed as:
Severe airway obstruction and high airway
resistance may cause Ambu bag ventilation
ineffective
Prolonged intubation may be Fatal

20. Intubation:
In the pregnant asthmatic may
be up to eight times more
difficult when compared to non-
pregnant women secondary to
soft tissue edema

21. Intubation:
 No consensus
 May be oral or nasal (less sedation , shorter
time, decreased aspiration , better comfort
post intubation, permit semi setting
position)
 Better Oral (wider tube avoid nasal
pathology, facilitate bronchoscopy if
needed)

22. Intubation drugs:
1- Ketamine (Ketalar)
No respiratory center depression
Decrease airway obstruction
No hypotension
Increase laryngeal reflexes that may cause laryngospasm
2- Propofol (Diprivan)
Decrease airway resistance
Hypotension (accentuated by decrease venous return due
to dynamic hyperinflation)
3- Etomidate (Amidate):
Less hypotension
4- thiopental (Intraval)
Hypotension
5- Dexmedetomidine (Precedex)

23.  Deep sedation is often necessary to prevent
patient ventilator dyssynchrony and
enforce controlled hypoventilation. A
combination of propofol (or a
benzodiazepine) and fentanyl is optimal,
and high doses may be required.
 Prolonged ventilatory support benefit from
daily awakening with physical therapy to
lessen the risk of ICU-acquired weakness
 NMBA is sometimes necessary
(cisatracurium besylate-NIMBEX)

24. Targets of MV in Asthma
Secondary1st choice
Permissive HyperCO2NormalCO2
Normal88-92%SaO2
More than 7.15More than 7.2pH
≤ 50 cm H2OTarget P Peak (Less)
≤ 30 cm H2O≤ 25 cm H2OTarget P Plateau (More)
Less than 5Target auto PEEP
Less than 10 L/minTarget Min Ventilation

25. Setting of MV in Asthma
Secondary1st choiceVolume Not Pressure
SIMVACMode
9-106-8VT
148Rate
80-12060-80Flow
SquareSine, Deceleratingwaveform
≤5 cm H2O0PEEP
A drugSaO2 ≥ 90%FiO2
1-1.2 Sec0.8-1 SecInspiratory time

26. Mayo AND Radeos. 1999

27. Peters et al. Respiratory Medicine (2012) 106, 344-348

28. Leatherman. 2013

29.  Reported mortality rates ranging from 6.5%
to 10.3%.
 Single center studies published between
1977 and 2003 reported an average
mortality of 8%, with a range of 0% to 38%.
 Two centers reported mortality rates of
2.5% and 0.6%
 Although mechanical ventilation for severe
asthma is associated with low immediate
mortality, patients are at increased risk for
recurrent fatal attacks over the subsequent
decade.
Marquette et al. . Am Rev Respir Dis . 1992 ; 146 ( 1 ): 76 - 81 .

30. Deaths from asthma were avoidable
in over 60 % of 195 cases of asthma
deaths:
 Nearly half died without seeking
medical advice
 One-quarter had been provided with a
personal asthma action plan
 Inappropriate prescribing of LABA
inhalers as the sole form of treatment

31. Weaning:
 is more rapidly achieved in
improving ASA patients
 It is mostly performed through
short time of PSV

32. Thank
You