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Asthma - Page 2

Ben was struggling to breathe when he reached the ER. He was immediately placed on oxygen. Ben presented with tachypnea, dyspnea, tachycardia, and expiratory wheezing on auscultation. He could not get enough air to speak in complete sentences.

Oxygen saturation, measured by pulse oximetry, was 92% on room air (Greater than 90%).

Oxygen saturation reflects the amount of hemoglobin that is saturated with oxygen. Hemoglobin is the oxygen-carrying molecule found in red blood cells. It has 4 oxygen binding sites. Most of the oxygen in the body combines with hemoglobin to be carried through the blood. This patient's oxygen levels are on the low end of normal because the patient is struggling to breathe.

Ben was asked to inhale as deeply as possible and then blow out as hard and as quickly as possible into a peak flow meter. Ben's peak flow measured 150 ml/L, about 25% of his personal best peak flow of 600 ml/L. A peak flow of less than 40% of normal is considered to be a severe asthma exacerbation.

A predicated peak flow value for the patient is determined when the patient is not experiencing asthma symptoms and is compared to the normal population based on the patient's age and height. Ben has previously established his personal best peak flow value which is helpful information for the ER physician and respiratory therapist. Ben's personal best may be different than his predicted value.

  • 12. What does a peak flow meter measure?
  • 13. Why should peak flow measurements be assessed regularly?
  • 14. What are the steps in using a peak flow meter?
  • 15. What is a "personal best" peak flow rate?
  • 16. What are the 3 zones commonly used to interpret peak flow rates?
    Explain their significance in managing asthma.

Because Ben was struggling to breathe, he was placed on 2 L of oxygen by nasal cannula. A respiratory therapist then administered three consecutive breathing treatments of albuterol sulfate with a small volume nebulizer. A nebulizer delivers medication by mist so that it can be inhaled and delivered deep into the lungs.

Albuterol sulfate is a short-acting beta-agonist (SABA). These medications work within minutes to relax the muscles surrounding the bronchi causing bronchospasm. They do not relieve swelling or inflammation of the bronchi.

This video below describes the administration of medications by a small volume nebulizer.

View Small Volume Nebulizer for Medication Delivery video

The breathing treatments took about an hour. Ben's peak flow was reassessed after this time. His peak flow measured 300 ml/L, about 50% of his personal best. Ben was started on an oral course of Medrol™ (methylprednisolone). This medication is a corticosteroid. It reduces inflammation in the lungs and also reduces mucus production in the bronchi.