INTRODUCTION :
Asthma is defined as a chronic inflammatory disease of the airway that is manifested by hyper responsiveness of airway to a wide variety of stimuli. It tends to be an episodic disease with exacerbations of reversible airway narrowing that are characterized clinically by coughing, wheezing and shortness of breath.
Asthma is probably the most common and potentially life threatening disorder to occur in pregnancy. The worldwide incidence is about 1 to 4%. It complicates in 0.5 to 1.5% of pregnancies and status asthmaticus complicates in 0.2%. In 20% the condition improves, in 30% cases it deteriorates and in 50% cases it remains unchanged.
In pregnancy, bronchodialator action is due to progesterone and cortisol and bronchoconstrictor action is due to reduced residual volume and increased PGF2 α.
There is no evidence that pregnancy has predictable effect on underlying asthma. 1/3rd of asthmatic women can expect worsening of disease at sometime during pregnancy. There is 18% increase in exacerbation of asthma following caesarian delivery compared with vaginal delivery.
EFFECTS OF ASTHMA ON PREGNANCY :
When severe asthma can affect pregnancy outcome . It may lead to abortions preterm labour, LBW, neonatal hypoxia etc.
There is a significant correlation between maternal pulmonary function and foetal birth weight.
Uncontrolled asthma has maternal risks and maternal deaths may be associated with status asthmaticus.
It may lead to life threatening complications like- pnuemothorax, pneumomediastenum, acute cor pulmonale, cardiac arrhythmias and muscle fatigue with respiratory arrest.
PATHOPHYSIOLOGY :
Allergens, respiratory infections, environmental pollutants, occupational exposure, cold air, emotional stress, strenuous exercise, aspirin and β blockers can precipitate asthma.
and secondary mediators like PGs,
thromboxanes and leukotrienes.
Mucus hypersecretion and mucosal edema
CLINICAL COURSE :
Clinically,
It may range from
|
DEATH
Functionally
Ventilation perfusion mismatching and airway narrowing
| Stage | PO2 | PCO2 | pH | FEV1 |
| Mild respiratory alkalosis | Normal | | | 65 – 80 |
| Respiratory alkalosis | | | | 50 – 64 |
| Danger zone | | normal | Normal | 35 – 49 |
| Respiratory acidosis | | | | <35 |
FEV – forced expiratory volume in 1 second
FOETAL EFFECTS :
Maternal alkalosis leads to fetal hypoxaemia well before maternal oxygenation is compromised.
Thus the fetus may be seriously compromised before maternal distress is severe.
This underscores the need for aggressive management of all pregnant women with acute asthma.
Therefore fetal response in effect becomes an indicator of maternal compromise .CLINICAL EVALUATION :
Signs :-
1) 1 Labored breathing
2) 2 Tachycardia
3) 3 Pulsus paradoxus
4) 4 Prolonged expiration and use of accessory muscles of respiration
Fatal signs:-
1) 1 Central cyanosis
2) 2 Altered consciousness
Investigations:-
1) 1 ABG analysis
2) 2 PEFR < 60% of baseline
3) 3 FEV1 < 20% suggestive of severe distress
4) 4 PO2 < 70 mm of Hg at sea level
5) 5 PCO2 > 35 mm of Hg at sea level
6) 6 PCO2 > 40 mm of Hg in pregnancy is suggestive of respiratory failure.
7) 7 pH < 7.35 (indication of hyperventilation and CO2 retention)
P
Preconceptional –
P
p possibility of child becoming asthmatic is 4%
If If 1 parent is asthmatic, the possibility is 8 to 10%
If both parents are asthmatic, the possibility is 30%
