Chapter 49: Asthma and Pulmonary Function Testing

Patient Story

A 7-year-old boy with a history of atopic dermatitis as an infant, presents with an episode of continued cough and wheezing 2 weeks following a recent cold. The cough is keeping the family up at night. This is his third episode this winter and has gone on longer than the others. He has otherwise been quite healthy. He appears comfortable but is coughing intermittently. His examination is significant for mild inspiratory and expiratory wheezing but no crackles. His mother mentions that she had asthma as a child and is worried that this might be asthma. The pediatrician prescribes an inhaled bronchodilator and refers the child for spirometry before and after an inhaled bronchodilator.

The spirometry results in Table 49-1 show a mild to moderate baseline defect with marked improvement post bronchodilator. The flow volume loops provide graphical demonstration of the same data (Figure 49-1). This confirms the diagnosis of asthma and an asthma treatment plan is developed.

Interpretation: mild to moderate baseline defect with marked improvement post bronchodilator.

Introduction

Asthma is a chronic inflammatory airway disorder with variable airflow obstruction and bronchial hyperresponsiveness that is at least partially reversible, spontaneously or with treatment (e.g., beta-2 agonist treatment). Patients with asthma have recurrent episodes of wheezing, breathlessness, chest tightness, and cough (particularly at night or in the early morning).

Epidemiology

• About one in 12 people (25 million or 8% of the population) had asthma in 2009, including about one in 10 children.¹ Rates of asthma are increasing; the greatest rise in rates is among black children, an almost 50 percent increase between 2001 and 2009.¹

• The number of deaths linked to asthma in 2007 was 3,447.¹ Using the 2006 to 2008 Nationwide Emergency Department (ED) Sample database, the estimated overall annual number of in-hospital asthma-related deaths was 1,144 (0.06%).² Most patients died as inpatients (N = 1043) but 101 died in the ED. There were 37 asthma-related deaths per year among children.

• Asthma was the first-listed diagnosis for 479,000 hospital discharges in 2009 with an average length of stay of 4.3 days.¹

• Asthma-associated medical expenses increased from $48.6 billion in 2002 to $50.1 billion in 2007.¹ Many uninsured people with asthma (about 40%) and about 1 in 9 insured people could not afford their prescription drugs.¹ In one retrospective study based on insurance claims for children with asthma who initiated asthma control therapy between 1997 and 2007 (N = 8834), the mean annual out-of-pocket asthma medication cost ...