Few cases of acute severe Asthma may need mechanical ventilation. Understanding finer adjustments makes a difference in outcome.

1. Bronchial Asthma:
Ventilation
LOKESH TIWARI
ASSISTANT PROF OF PEDIATRICS
ALL INDIA INSTITUTE OF MEDICAL SCIENCES, PATNA

2. Pathophysiology status asthmaticus
 Pathologic changes in the airway  airflow obstruction  premature
airway closure on expiration  dynamic hyperinflation  hypercarbia
 Dynamic hyperinflation or “air-trapping” also leads to ventilation /
perfusion (V/Q) mismatching causing hypoxemia

3. Mechanical Ventilation
Indications
 Poor response to initial therapy
 Severe hypoxia
 Rapid deterioration in mental state
 Rising PCO2
 Cardiopulmonary arrest

4. Bronchial Asthma
Non-invasive Ventilation
 Positive-pressure by nasal mask (BiPAP)
 Potential benefits:
 airway stenting
 improve V/Q match
 CPAP improves hypoxemia in asthmatic children

5. Intubation Tips
 Preoxygenate with 100% oxygen
 Anticipate hypotension
 Cuffed ET tube with the largest appropriate diameter
 Avoid histamine-producing agents like morphine or atracurium
 Ketamine: preferred induction agent due to its bronchodilatory action.
 Use atropine, Benzodiazepam and a rapid-acting muscle relaxant
(vecuronium).

6. High peak Pressure: Airway Resistance
PressureTime (sec)

7. Prolonged Expiration
Time (sec)
Flow

8. Prolonged Expiration: I/E Ratio
Time (sec)
Flow

9. Auto PEEP
Time (sec)
Flow

10. Auto PEEP: I/E Ratio and Rate
Time (sec)
Flow

11. Auto PEEP

12. Ventilation Principles
 Maintain adequate oxygenation,
 Avoid air trapping
 Slow ventilator rates
 Prolonged expiratory phase, short inspiratory time
 Minimal PEEP (debatable)
 Permissive hypercarbia (Controlled Hypoventilation) with art pH of >7.2
 Adjust minute ventilation
Stewart TE, Slutsky AS. Crit Care Med. 1996;24:379–80
 Attempt extubation as soon as possible.

13. Typical Ventilator Setting
 VT of 5–6 mL/kg,
 RR approximately half of the normal for age,
 I: E ratio of 1:3
 PEEP of 2–3 cm of H2O.
 In infants, pressure controlled ventilation: adjust PIP to achieve adequate
ventilation;

14. Complications
 Hypotension
 Oxygen desaturation
 Pneumothorax/ subcutaneous emphysema,
 Cardiac arrest
 Suspect tension pneumothorax and treat promptly

15. Thanks