Pulmonary Emphysema Regional Distribution and Extent Assessed by Chest Computed Tomography Is Associated With Pulmonary Function Impairment in Patients With COPD

Objective: This study aimed to evaluate how emphysema extent and its regional distribution quantified by chest CT are associated with clinical and functional severity in patients with chronic obstructive pulmonary disease (COPD). Methods/Design: Patients with a post-bronchodilator forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) < 0.70, without any other obstructive airway disease, who presented radiological evidence of emphysema on visual CT inspection were retrospectively enrolled. A Quantitative Lung Imaging (QUALI) system automatically quantified the volume of pulmonary emphysema and adjusted this volume to the measured (EmphCTLV) or predicted total lung volume (TLV) (EmphPLV) and assessed its regional distribution based on an artificial neural network (ANN) trained for this purpose. Additionally, the percentage of lung volume occupied by low-attenuation areas (LAA) was computed by dividing the total volume of regions with attenuation lower or equal to -950 Hounsfield units (HU) by the predicted [LAA (%PLV)] or measured CT lung volume [LAA (%CTLV)]. The LAA was then compared with the QUALI emphysema estimations. The association between emphysema extension and its regional distribution with pulmonary function impairment was then assessed. Results: In this study, 86 patients fulfilled the inclusion criteria. Both EmphCTLV and EmphPLV were significantly lower than the LAA indices independently of emphysema severity. CT-derived TLV significantly increased with emphysema severity (from 6,143 ± 1,295 up to 7,659 ± 1,264 ml from mild to very severe emphysema, p < 0.005) and thus, both EmphCTLV and LAA significantly underestimated emphysema extent when compared with those values adjusted to the predicted lung volume. All CT-derived emphysema indices presented moderate to strong correlations with residual volume (RV) (with correlations ranging from 0.61 to 0.66), total lung capacity (TLC) (from 0.51 to 0.59), and FEV1 (~0.6) and diffusing capacity for carbon monoxide DLCO (~0.6). The values of FEV1 and DLCO were significantly lower, and RV (p < 0.001) and TLC (p < 0.001) were significantly higher with the increasing emphysema extent and when emphysematous areas homogeneously affected the lungs. Conclusions: Emphysema volume must be referred to the predicted and not to the measured lung volume when assessing the CT-derived emphysema extension. Pulmonary function impairment was greater in patients with higher emphysema volumes and with a more homogeneous emphysema distribution. Further studies are still necessary to assess the significance of CTpLV in the clinical and research fields.This research was supported by the Brazilian Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico, Grants Nos. 302702/2017-2 and 302839/2017-8) and the Rio de Janeiro State Research Supporting Foundation (Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro, Grants Nos. E-26/211.867/2016, E-26/202.785/2017, E-26/203.001/2018), and by national funds through FCT, Cardiovascular R&D Center – UnIC (UIDB/00051/2020 and UIDP/00051/2020)

Co-occurrence of Point Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Aedes aegypti Populations in Myanmar

Background:Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar.Methodology/Principal Findings:We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study.Conclusions/Significance:Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti

Prone position to treat bronchopleural fistula in post-operative acute lung unjury.

OBJECTIVE: Prone position is used to treat patients with acute lung injury or acute respiratory distress syndrome because it improves gas exchange and respiratory mechanics. When broncho-pleural fistula occurring, the clinical impact of prone position is limited; however, its use could be tried when the fistula is small or other potential treatments are not possible. METHODS: A 45-year-old man with oesophageal cancer submitted to a total oesophagectomy with intrathoracic transposition of the stomach developed post-operatively respiratory failure and pneumothorax, which were worsened by unilateral pleural rupture and severe subcutaneous emphysema produced after an attempt to introduce through anterior chest wall a second drainage tube. RESULTS: Prone position associated with lung protective strategy was implemented during 16-18 h daily and after the change of position PaO2/FiO2 increased of 35% and PaCO2-PetCO2 decreased about 40%; at 4th day under treatment, the subcutaneous emphysema and pneumothorax could not be detected either clinically or radiologically. On the 6th day the lung lesion could not be observed under the CT-scan. CONCLUSIONS: In a patient that underwent a major thoracic surgery the addition of prone positioning to protective lung ventilation rendered possible not only the healing of the acute lung injury, but also the quick repair of a lung rupture owing to a thoracic drainage attempt

Sigh: tool to determine the respiratory viscoelastic properties.

OBJECTIVE: In mechanically ventilated patients a high fraction of the pressure can be dissipated to overcome the viscoelastic components of the respiratory system. Recently it was demonstrated that sigh improved oxygenation in mechanically ventilated ARDS patients. We evaluated if, in acute lung injury (ALI) patients, the sigh can be used to measure the respiratory viscoelastic properties. METHODS: Ten consecutive normal subjects undergoing general anaesthesia for minor abdominal surgery and ten ALI patients admitted to the ICU, were studied. Three sighs were administered every minute during the measurement period. The viscoelastic constants (E2, R2 and tau2) were determined by (i) a series of end-inflation airway occlusions (multiple breath method, MBM) and (ii) fitting the time course of the slow decay in pressure during end inspiratory pause of the sigh (sigh method, SM). The results were compared by means of the limits of agreement as modified for small sample sizes. RESULTS: Viscoelastic parameters were similar to those obtained in other studies. In normal subjects the mean differences (+/- SEM) of tau2, R2, and E2 given by the SM and the MBM were 0 +/- 0.04 s, 0.37 +/- 0.20 cmH2O L(-1) s, and 0.21 +/- 0.26 cmH2O L(-1), respectively. The mean differences (+/- SEM) of tau2, R2, and E2 in ALI patients were 0.02 +/- 0.02 s, 0.45 +/- 0.31 cmH2O L(-1) s, 0.34 +/- 0.36 cmH2O L(-1), respectively. No lack of agreement could be detected between the two methods in all variables in normal subjects and ALI patients. CONCLUSIONS: The long inflation time characteristic of the sigh allowed the determination of the viscoelastic constants by means of a simpler and faster method. Moreover it does not require very small tidal volumes, which can increase reabsorption atelectasis in ALI patients and can improve alveolar recruitment and oxygenation in these patients

Gas distribution in a two-compartment model during volume or pressure ventilation: role of elastic elements

The results of the studies on pulmonary gas distribution during constant-flow controlled-volume inflation (VCV) and inspiratory constant pressure inflation (PCV) in experimental studies are conflicting. In a mathematical model, with the characteristics of two lung compartments including tissue viscoelastic properties, pulmonary gas distribution was tested by simulating PCV and VCV at same inflation volumes. The compartmental distributions of the tidal volume were compared during CMV and PCV in different configurations obtained by changing the elastic and viscoelastic properties in each compartment, but maintaining the same total values of respiratory mechanics measured in patients. In all instances PCV resulted in a slightly higher air-trapping than in VCV mode. Heterogeneous elastic properties diverted most of the tidal volume towards the less compromised compartment. However, both ventilatory modes provided similar compartmental gas distribution, but during VCV compartmental peak pressures were higher in the sicker compartment respect to PCV. The use of PCV could grant a less remarkable pressure variability able to reduce the potential ventilator-associated lung injury. Moreover, the parameters measured during an end-inspiratory pause could not pinpoint unique characteristics for each configuration

Effect of positive expiratory pressure and type of tracheal cuff onthe incidence of aspiration in mechanically ventilated patients inan intensive care unit

Objective: To test the effects of positive expiratory pressure onthe leakage of fluid around cuffs of different tracheal tubes, inmechanically ventilated patients and in a benchtop model.Design: Randomized clinical trial and experimental in vitrostudy.Setting: Intensive care unit of a university hospital.Patients: Forty patients recovering in the intensive care unitwere ventilated in volume-controlled mode. Twenty patients wererandomly intubated with Hi-Lo tubes (HL group), whereas theremaining 20 subjects were intubated with SealGuard tubes (SGgroup).Interventions: Immediately after intubation and cuff inflationwith 30 cm H2O, Evans blue was applied onto the cephalic surfaceof the tracheal tube cuff. A 5-cm H2O positive expiratory pressurewas used during the first 5 hrs of stay, and thereafter it wasremoved. Bronchoscopy verified whether the dye leaked aroundthe cuff. The experiment lasted 12 hrs. Leakage was also testedin vitro with the same tracheal tubes with incremental level ofpositive expiratory pressure.Measurements and Main Results: At 1 hr, 5 hrs, and thereafterhourly until 12 hrs, bronchoscopy was used to test the presenceof dye on the trachea caudal to the cuff. At the fifth hour, twopatients of the HL group failed the test. One hour after positiveexpiratory pressure removal, all subjects in group HL exhibited adyed lower trachea. On the other hand, one patient in group SGpresented a leak at the eighth hour, and at the 12th hour three ofthem were still sealed. In vitro, the same level of positive expiratorypressure delayed the passage of dye around the cuff; after30 mins positive expiratory pressure was removed, and in 10 minsall dye leaked only in the Hi-Lo tube.Conclusions: We found that 5 cm H2O positive expiratorypressure was effective in delaying the passage of fluid around thecuffs of tracheal tubes both in vivo and in vitro. The SealGuardtube proved to be more resistant to leakage than Hi-L