In asthma there are three basic
pathophysiologic changes:
1. Airway inflammation.
2. Airway obstruction.
3. Airway hyperresponsiveness
In case of asthma, DLCO (carbon monoxide diffusing capacity)
usually remains normal because although there is bronchoconstriction there is
no alveolar disease. On the other hand, it may be increased if there is
significant bronchospasm of air trapping
Increase in FEV by 12% or more after bronchodilator is indicates of
asthma
In asthma, peak flow <200 L/minute or 50% decrease
from baseline indicates severe obstruction
Aspergillus presented as a new onset of shortness of breath, wheeze,
nocturnal cough, feeling generally unwell with a headache and fever in
previously well controlled asthmatic patient
Think of Churg-Strauss Syndrome when you find a combination of
asthma, eosinophilia and nerve lesion
About 80% of hard to control asthmatics improve with antireflux
therapy
Bronchodilators used in the treatment of asthma may exacerbate
GERD because it leads to a decrease in the lower esophageal sphincter (LES)
resting pressure
Wheezing is not specific for asthma because asthma, chronic
obstructive pulmonary disease (COPD), congestive heart failure (CHF), and upper
airway cough syndrome (UACS) can all cause wheezing.
A normal PCO2 in acute asthma is a warning sign of impending
respiratory failure
Early in an asthma attack, the ABGs reveal respiratory alkalosis and
mild hypoxia.
Normal Pco2 or development of respiratory acidosis indicates impending respiratory
failure
Marked hypoxemia is infrequent during uncomplicated asthma
attacks. If there is marked hypoxemia (arterial partial pressure of oxygen
[PaO2] <60 mmHg, oxygen saturation [SaO2] <90 percent), it suggests
life-threatening asthma and possible complicating conditions, such as pneumonia
or atelectasis due to mucus plugging.
In mechanically ventilated patients with acute, severe asthma, minimizing
minute ventilation, (even to the point of allowing the development of
hypercapnia)
is the best strategy to reduce dynamic hyperinflation and the
subsequent risk of hemodynamic compromise and barotrauma
In severe asthma oxygen is needed to raise oxygen saturation to above
90% and above 95% in
pregnancy
Arterial blood gas measurements in acute asthma are indicated only
in sever cases which not respond to bronchodilators
In asthmatic patients, the overall disease severity does not
vary significantly within a given patient over the course of the disease.
Individuals who have mild asthma typically continue to have mild asthma,
whereas those with sever disease usually presents with sever disease
In status asthmaticus, physical examination shows:
Tachycardia
Tachypnea
Cyanosis
Use of accessory muscles
Intercostal retractions
Pulsus paradoxus, and
Absence of wheezing (silent chest).
Avoid morphine in patients with asthma exacerbation because it may
cause histamine release and make the symptoms worse
Bronchial asthma can cause SIADH by unknown mechanisms.
Other pulmonary diseases causing SIADH include pneumonia,
atelectasis, acute respiratory failure and pneumothorax.
Think of avascular necrosis of the femoral head in asthmatic
patient with history of chronic steroid treatment
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