ABSTRACT
BACKGROUND: It is not well known what is the main mechanism causing lung heterogeneity in healthy lungs under mechanical ventilation. We aimed to investigate the mechanisms causing heterogeneity of regional ventilation and parenchymal densities in healthy lungs under anesthesia and mechanical ventilation. METHODS: In a small animal model, synchrotron imaging was used to measure lung aeration and regional-specific ventilation (sVÌ). Heterogeneity of ventilation was calculated as the coefficient of variation in sVÌ (CVsVÌ ). The coefficient of variation in lung densities (CVD ) was calculated for all lung tissue, and within hyperinflated, normally and poorly aerated areas. Three conditions were studied: zero end-expiratory pressure (ZEEP) and FI O2 0.21; ZEEP and FI O2 1.0; PEEP 12 cmH2 O and FI O2 1.0 (Open Lung-PEEP = OLP). RESULTS: The mean tissue density at OLP was lower than ZEEP-1.0 and ZEEP-0.21. There were larger subregions with low sVÌ and poor aeration at ZEEP-0.21 than at OLP: 12.9 ± 9.0 vs. 0.6 ± 0.4% in the non-dependent level, and 17.5 ± 8.2 vs. 0.4 ± 0.1% in the dependent one (P = 0.041). The CVsVÌ of the total imaged lung at PEEP 12 cmH2 O was significantly lower than on ZEEP, regardless of FI O2 , indicating more heterogeneity of ventilation during ZEEP (0.23 ± 0.03 vs. 0.54 ± 0.37, P = 0.049). CVD changed over the different mechanical ventilation settings (P = 0.011); predominantly, CVD increased during ZEEP. The spatial distribution of the CVD calculated for the poorly aerated density category changed with the mechanical ventilation settings, increasing in the dependent level during ZEEP. CONCLUSION: ZEEP together with low FI O2 promoted heterogeneity of ventilation and lung tissue densities, fostering a greater amount of airway closure and ventilation inhomogeneities in poorly aerated regions.
Subject(s)
Oxygen , Positive-Pressure Respiration , Animals , Lung , Lung Compliance , Lung DiseasesABSTRACT
Changes in erythrocyte deformability (ED) parameters have been investigated in 36 patients suffering from different forms of headache (classic and common migraine; migraine with interval headache; chronic tension headache) and treated with flunarizine (10 mg/day at bedtime). Patients were carefully selected in order to avoid any possible interference with the parameters under study, and smoke and drug use in particular (symptomatics included) were considered as criteria for exclusion from the trial. Controls of ED parameters were planned before treatment and after 20 and 35 days. Baseline ED alterations were present only among patients with chronic tension headache, but flunarizine treatment was able to positively modify ED parameters in these patients, as well as in migraine cases that showed normal baseline ED values. No correlation was found between patients' characteristics and baseline ED values, nor between ED changes under treatment and therapeutic effects of flunarizine.
