Sputum induction

Abstract

The aim of sputum induction is to collect an adequate sample of secretions from lower airways in subjects who do not produce sputum spontaneously in order to study the features of airway inflammation in asthma and other respiratory disorders. Inhalation of isotonic or hypertonic solutions administered by nebulisation has been demonstrated to induce a small amount of airway secretion that can be expectorated and analysed. The mechanisms by which this occurs are not known, but both direct and indirect mechanisms are likely to be involved. It is believed that the increased osmolarity of the airway lining fluid increases vascular permeability in the bronchial mucosa and induces production of mucus by submucosal glands. Animal studies have shown that hypertonic saline increases vascular permeability in the airways, and this effect can be modulated by capsaicin [1]. However, in vivo instillation of hypertonic solution into the airways of animals and humans induces an increase in the levels of several mediators but no rise in levels of albumin or other markers of increased vascular permeability [2,3]. Therefore, this hypothesis has not been confirmed, and only preliminary measurements of sputum osmolarity after induction have been reported with conflicting results [4]. Conversely, previous reports have demonstrated increased clearance of secretions from the airways in humans after administration of hypertonic saline aerosol [5], perhaps by facilitating the collection of small amounts of pre-existing airway secretions.Although sputum induction has been used extensively since the 1990s, few methodological studies have examined the influence of various technical factors on the feasibility and repeatability of sputum induction and collection. As with other techniques, the lack of a "gold standard" makes it hard to evaluate the influence of these technical factors on the adequacy and accuracy of sputum induction.The technique of sputum induction consists of inhaling an aerosol of saline (either normal or hypertonic) over different time-periods. Volunteers/ patients are instructed to expectorate into a container. Various issues must be considered with regard to this procedure: 1) facilities, equipment and personnel; 2) bronchodilator pretreatment; 3) pulmonary function monitoring; 4) concentration of saline solution and nebuliser output; 5) duration of inhalation; 6) expectoration technique; 7) spontaneous versus induced sputum; and 8) frequency of sputum induction. The influence of these factors on the feasibility of the technique must be evaluated in terms of the success rate, repeatability and accuracy of the results obtained.

Breathomics for Assessing the Effects of Treatment and Withdrawal With Inhaled Beclomethasone/Formoterol in Patients With COPD

“…Sputum induction, processing and analysis were performed according to the European Respiratory Society (ERS) guidelines (Djukanovic et al, 2002; Efthimiadis et al, 2002; Paggiaro et al, 2002). …”

“…Subjects were pre-treated with inhaled salbutamol (400 μg), and, after 10 min, a spirometry was repeated (Paggiaro et al, 2002). Subjects were asked to inhale hypertonic saline (3%) for 5 min and then, to rinse their mouths and try to expectorate into a sterilized box (Paggiaro et al, 2002). Five-minute inhalation sessions were repeated four times for a total of 20 min (Paggiaro et al, 2002).…”

“…Subjects were asked to inhale hypertonic saline (3%) for 5 min and then, to rinse their mouths and try to expectorate into a sterilized box (Paggiaro et al, 2002). Five-minute inhalation sessions were repeated four times for a total of 20 min (Paggiaro et al, 2002). A spirometry was performed after each inhalation session to detect significant fall of FEV 1 .…”

Omalizumab Attenuates Airway Inflammation and Interleukin-5 Production by Mononuclear Cells in Patients with Severe Allergic Asthma

“…Sputum was induced as described previously [24,25]. In brief, salbutamol was delivered using a metered-dose inhaler prior to sputum induction.…”

Carcinoembryonic antigen, neuron‐specific enolase and cytokeratin fragment 19 (CYFRA 21‐1) levels in induced sputum of lung cancer patients

“…Induced sputum has been used extensively, with the aim of improving our understanding of the pathogenesis of obstructive lung diseases, mainly asthma [13,14]. The main advantage of induced sputum is that it is minimally invasive and obtained readily.…”