A 46-year-old asthmatic man complains of wheezing for 2 days despite regular use of his inhaled albuterol, ipratropium, fluticasone, and salmeterol. Yesterday he took 40 mg of prednisone on his family physician's phone advice. He now:
Needs a chest x-ray and arterial blood gas prior to hospitalization, as he has failed outpatient therapy.
+Should receive three more treatments of nebulized beta-agonist therapy, then be admitted if still not improving.
+Should be admitted to the hospital if, despite further therapy, his PEFR is 280 L/min.
+Is considered to have a “mild” asthma exacerbation with arterial blood gases: Pao2 78, Paco2 38, pH 7.38.
+Requires arterial blood gas testing to determine degree of hypoxemia, especially if he appears clinically ill (i.e., deteriorating mental status, use of accessory muscles, and pulsus paradoxus).
Physicians must determine the severity of an asthma attack and the response to treatment. Clinicians often underestimate the severity of obstruction. Mental status, respiratory rate, use of accessory muscles, and pulsus paradoxus are important signs. Objective measurements of obstruction of the airway are the forced expiratory volume in 1 second (FEV1) and the peak expiratory flow rate (PEFR). Although absolute PFT measurements can be used, percentages of predicted performance values are preferable because they account for individual factors such as age, sex, and height. The ideal use of PFTs is when compared to the patient's established personal best to take response to therapy. A PEFR of 50–80% predicted or the patient's best effort is consistent with a moderate exacerbation. A PEFR value <50% of predicted or personal best is a severe exacerbation. Measurements of arterial blood gases (ABG) are used primarily to determine the Paco2 and should be limited to the subset of patients with PFTs <30% of predicted. Hypoxemia with normocarbia or hypercarbia and a pH of <7.35 indicates severe asthma and impending respiratory failure.