Asthma

Asthma is a common chronic lung disease of children that causes repeated episodes of wheezing, breathlessness, chest tightness, and nighttime or early morning coughing. These symptoms can often be controlled by avoiding or reducing asthma triggers (allergens and irritants) and by following recommendations for appropriate medical care (initiating asthma control medications or adjusting the current treatment regimen when needed). Adherence in severe asthma is suboptimal as are the clinic measures to assess adherence. Uncontrolled asthma results in significant costs to families and society when asthma exacerbations result in medical encounters, lost school days, and reduced productivity. Recently it is also stated that Children who have asthma or wheezing in early childhood may be at a higher risk of developing obesity.

Numerous co-existing conditions have been associated with asthma exacerbations making it difficult to keep asthma under control [for instance, recurrent sinus infection and symptomatic gastrointestinal reflux (GERD). To give an example, wheeze in children with sickle cell disease is associated with airflow limitation and lung function decline.

Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. Airway resistance is traditionally measured by relating air flow and driving pressure using body plethysmography, thus deriving airway resistance (Raw), specific airway resistance (sRaw), and specific airway conductance (sGaw).

Other methods to measure airway resistance include

  • Forced oscillation technique (FOT), which allows calculation of respiratory system resistance (RRS) and reactance (XRS), and
  • Interrupter technique, which allows calculation of interrupter resistance (Rint).

An advantage of these other methods is that they may be easier to perform than spirometry, making them particularly suited to patients who cannot perform spirometry, such as young children, patients with neuromuscular disorders, or patients on mechanical ventilation.

In children, IOS/FOT was more useful than spirometry in identifying asthma and uncontrolled asthma and predicting loss of control and exacerbations. Oscillatory technique predicts young children at risk for loss of lung function with age and the potential for early intervention to prevent further sequelae.

Since spirometry also requires a deep inhalation, which can alter airway resistance, these alternative methods may provide more sensitive measures of airway resistance. Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique.