Aerosol therapy in obese subjects with or without COPD: Evaluation of pulmonary deposition pattern and determination of predictive factors.
Key Words: Respiratory Therapy; Obesity; Aerosol Therapy
Abstract
Introduction: Obesity is responsible for triggering several systemic alterations, increasing the severity and morbidity of existing pathologies. Obese individuals with respiratory diseases, such as chronic obstructive pulmonary disease (COPD), have higher rates of dyspnea, worse overall health, higher consumption of medications and a lower effectiveness of inhaled medications compared to patients with normal weight. To date, there is no data in the literature that defines what would be the factors responsible for the low effectiveness in the use of this type of medication in the obese population. In addition, the possibility of implementing aerosol therapy via a high-flow nasal cannula to improve the deposition pattern in this population has not yet been described.
Objectives:
1- To analyze the association between anatomic variables of the upper airways of healthy obese individuals and the percentage of pulmonary deposition of inhaled radiopharmaceuticals. Find predictors for this deposition.
2 - To analyze inhaled aerosol pulmonary deposition via High Flow Nasal Cannula (CNAF) in patients with COPD (obese and non-obese).
Method: The study was performed in two parts: the first part (study 1) was a non-randomized controlled clinical trial with obese and non-obese individuals. The following were evaluated: upper airway anatomical and anatomical characteristics (Computed Tomography and modified Mallampati score). All volunteers inhaled radiopharmaceutical (99mTc-DTPA; 1mci), with bronchodilator Fenoterol hydrobromide and ipratropium bromide using membrane inhaler (MESH) during quiet breathing (tidal volume). Deposition comparisons were performed between obese group and the non-obese groups. The second part of the study was a crossover trial where patients with COPD inhaled radiopharmaceutical (99mTc-DTPA; 1mci), with bronchodilator Fenoterol hydrobromide and ipratropium bromide on two different days (at least two days apart). One day, inhalation occurred simply using membrane inhaler (MESH), while in the other day the inhalation occurred via the CNAF. The sequence of the intervention was previously randomized.
Study results 1: Participated in the study 17 non-obese individuals and 12 obese individuals. The volunteers of the obese group had 30% lower pulmonary deposition than non-obese patients (p = 0.01, 95% CI 0.51 to 4.91). Anatomical variables related to airway shape differed between groups. The anteroposterior diameter of the obese retroglossal region was 29% higher (p <0.01, 95% CI -5.44 to -1.1), while the lateral diameter was 42% lower (p = 0.03, 95% CI % 0.58 to 11.48), compared to non-obese individuals. The cross-sectional area of the retropalatar region and its relationship with the cross-sectional area in the retroglossal region were also lower in obese (p <0.05). None of these variables correlated with pulmonary deposition of the inhaled aerosol. Meanwhile, BMI was responsible for 32% of the variance of pulmonary deposition (p <0.001; β -0.28; 95% CI -0.43 to -0.11). When analyzed under the subdivision of modified Mallampati grades, obese class 4 subjects had 44% less pulmonary deposition of inhaled radiopharmaceuticals than non-obese subjects in the same classification.
Conclusion of study 1: The anatomical alterations of upper airways, due to obesity, seem to not interfere in pulmonary deposition more than BMI alone. However, obesity associated with modified Mallampati class 4 was responsible for an exacerbation of the difference in pulmonary deposition between obese and non-obese individuals, which may be a detrimental factor to the offer of inhaled medication in the obese population.
Results of study 2: Eleven volunteers with COPD (5 obese) participated in this crossover study. They have comprised the following groups: Simple Inhalation (n = 11) and Inhalation via High Flow Nasal Cannula HFNC (n = 11). On average, the participants had FEV1 of 43%; FVC of 58%; FEV1 / FVC 70% and PEF 30% (based on predicted values). The mean inhalation group, mean lung deposition percentage of 2.8% (IQR3) of the total count, meanwhile, used a 3.0% HFNC (IQR 1.3, p> 0.05; Wilcoxon's test The analysis stratified by BMI (eg, obese and non-obese) were submitted to HFNC and Simple Inhalation (4.1%), and 3.1%, respectively), but not significant (2,8% IQR 2 and 2,7% IQR 4, respectively).
The conclusion of the study 2: The option of high flow inhalation with a nasal cannula favored a pulmonary aerosol deposition, similar to a simple inhalation in patients with COPD, without further benefits to the obese patients.