Deep inspiration-induced changes in lung volume decrease with severity of asthma

Abstract

We have previously reported that the magnitude of deep inspiration (DI)-induced bronchodilation is only slightly reduced in mild asthmatics, compared to healthy subjects. The aim of this study was to evaluate whether increased severity of asthma is associated with impairment in the ability of DI to induce changes in lung volume. Thirty-six consecutive asthmatics recruited from the Pulmonary and the Allergy Outpatient Clinics of the Institute of Respiratory Diseases of the University of Palermo were divided into 3 groups: Intermittent (I), Mild Persistent (MP) and Moderate-Severe (MS), based on GINA guidelines. Single dose methacholine (Mch) bronchoprovocations were performed in the absence of DI, to induce at least 15% reduction in inspiratory vital capacity (IVC) from baseline. The post-Mch IVC was followed by 4 consecutive DI and by another IVC, to determine the bronchodilatory effect of DI. The bronchodilatory effect of DI was found to significantly decrease with increasing severity of asthma (I: 68+/-5.4%, MP: 45+/-7.2%, MS: 4+/-15.6%; ANOVA: P<0.0001). Bronchodilation by DI, but not FEV(1) or FEV(1)/FVC, was also inversely correlated to symptom scores (r=-0.42, P=0.01) and to weekly salbutamol usage (r=-0.47, P=0.004). These observations provide support to the hypothesis that the attenuation of the bronchodilatory effect of DI contributes to the severity of the clinical manifestations of asthma.

Asthmatics with high levels of serum surfactant protein D have more severe disease

“…Indeed, SP-D promotes the clearance of pathogens, enhances the phagocytosis of apoptotic cells and inhibits pro-inflammatory cytokine release by effector cells [11][12][13]. We favour the hypothesis that altered surfactant would be the underlying cause of the impairment in the bronchodilatory effect of deep inspirations that has been observed in asthma [14]. This is because the effectiveness of the beneficial effects of lung inflations on airways is dependent on the interdependence between the parenchyma and the airway walls.…”

Stress-Induced Respiratory Pattern Changes in Asthma

“…However, variability also seemed elevated throughout the stress protocol, suggesting that this may be a more stable aspect of the breathing pattern in asthma. Given the bronchodilating effect of deep breaths in healthy and mild to moderate persistent asthma (37,38), intermittent deep breaths have been considered as a mechanism that can keep the airway passages open. However, prior research within a stressinduction context had remained inconclusive, most likely because of considerable variation in scoring methods.…”

Enhanced airway dilation by positive-pressure inflation of the lungs compared with active deep inspiration in patients with asthma

“…In patients with mild asthma, however, dilation of constricted airways by deep inspiration is impaired (16,38,44). The impairment of this bronchodilatory effect is related to asthma severity and disease status (28,40). Restoring this physiological mechanism that reverses airways obstruction in patients with asthma might reduce the need of current asthma treatment.…”