Question

Your patient has asthma, newly diagnosed. His symptoms are shortness of breath, oxygen saturation of 60% on 3 liters of oxygen, anxiety, and loud breathing. He had a respiratory treatment earlier but has awoken with some severe symptoms.

Question: Explain the full progression of blood gas abnormalities in a severe asthma attack. You will need to defend your answer using specific facts, data, and other information.

Answer 1

Question: Explain the full progression of blood gas abnormalities in a severe asthma attack. You will need to defend your answer using specific facts, data, and other information.

Answer

Arterial Blood Gas progressions in asthma

ASTHMA is a chronic inflammatory airway disease in which the patient have severe dyspnoea and audible wheezing and sputum production

there are so many test to identify and treat asthma and one of the most important test is ABG .Most of the ABG of an Asthamatic patient will show a decreased PO2 and increased PCO2.

This test may reveal dangerous levels of hypoxemia or hypercarbia due to hyper or hypoventilation and then it can lead to respiratory acidosis (where PH falls below 7.35 and CO2 level increase more than 40 mmHg.

Hypercarbia is of concern in that it reflect inadequate ventilation and may indicate the need for mechanical ventilation due to respiratory failure ,if the PCO2 is elevated then the decision is to proceed with endotracheal intubation and mechanical ventilation .

NORMAL ABG VALUES

PH -7.35 to 7.45

PO2- above 92 upto 100 mmhg

PCO2 - 35 - 45 mmHg

HCO3-18- 25 mmmol/L

* In an  Asthamatic patient oxygen saturation ie, PCO2 will decrease as the patient is having severe bronchospasm due to inflammatory response in the airway.

* Though there is both hyperventilation (rapid breathing ) hypoventilation in which hypoventilation causes hypoxia and also hypercarbia . Hypercarbia is due to the airway narrowing and the hypoventilation the CO2 which needed to be flushed out of the lungs through expiration will get tapped inside the lung and even hyperventilation in patients will prevent the completet exhalation of CO2 so, PCO2 increases in asthma

* Increased PCO2 will alter the blood PH as the CO2 in blood get converted to Carbonic acid thus the PH turns to acidic and though it is due to respiratory reason its known as Respiratory Acidosis .

* These inturn can lead to Respiratory failure and can drag the patient to ICu ,intubation or ventilatory supports

Thus ABG can be useful to help gauge the severity of an asthma exacerbation in moderate to severe exacerbations.
Initial findings can be hypoxia and hypocarbia due to hyperventilation. However, as the symptoms progress and air-trapping gets worse, an ABG may show respiratory acidosis with hypercarbia.

But the careful monitoring and management with a proper ABG can prevent medical emergencies