Recent advances in theoretical models of respiratory mechanics

As an important branch of biomedical engineering, respiratory mechanics helps to understand the physiology of the respiratory system and provides fundamental data for developing such clinical technologies as ventilators. To solve different clinical problems, researchers have developed numerous models at various scales that describe biological and mechanical properties of the respiratory system. During the past decade, benefiting from the continuous accumulation of clinical data and the dramatic progress of biomedical technologies （e.g. biomedical imaging）, the theoretical modeling of respiratory mechanics has made remarkable progress regarding the macroscopic properties of the respiratory process, complexities of the respiratory system, gas exchange within the lungs, and the coupling interaction between lung and heart. The present paper reviews the advances in the above fields and proposes potential future projects.

Respiratory mechanics,ventilator-associated pneumonia and outcomes in intensive care unit

AIM To evaluate the predictive capability of respiratory mechanics for the development of ventilator-associated pneumonia (VAP) and mortality in the intensive care unit(ICU) of a hospital in southern Brazil. METHODS A cohort study was conducted between, involving a sample of 120 individuals. Static measurements of compliance and resistance of the respiratory system in pressure-controlled ventilation (PCV) and volumecontrolled ventilation(VCV) modes in the 1 st and 5 th days of hospitalization were performed to monitor respiratory mechanics. The severity of the patients' illness was quantified by the Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ). The diagnosis of VAP was made based on clinical, radiological and laboratory parameters.RESULTS The significant associations found for the development of VAP were APACHE Ⅱ scores above the average(P = 0.016), duration of MV (P = 0.001) and ICU length of stay above the average(P = 0.003), male gender(P = 0.004), and worsening of respiratory resistance in PCV mode(P = 0.010). Age above the average(P < 0.001), low level of oxygenation on day 1(P = 0.003) and day 5 (P = 0.004) and low lung compliance during VCV on day 1 (P = 0.032) were associated with death as the outcome.CONCLUSION The worsening of airway resistance in PCV mode indicated the possibility of early diagnosis of VAP. Low lung compliance during VCV and low oxygenation index were death-related prognostic indicators.

Model-based Analysis of Ventilation Inhomogeneity in Respiratory Mechanics

Individualized models of respiratory mechanics help to reduce potential harmful effects of mechanical ventilation by supporting the evaluation of patient-specific lung protective ventilation strategies. Assessing ventilation inhomogeneities might be an important aspect in optimizing ventilator settings. The aim of this studyis to capture and analyze ventilation inhomogeneity by a mathematical model using clinical data. The results show that the lung physiology of mechanically ventilated patients without lung condition can be described by an inhomogeneity model revealing two alveolar compartments with median time constants of 0.4 and 3.9 s. Thus, the IHM in combination with specific ventilation maneuver might be suitable to capture lung physiology for model-based optimization of ventilator settings but requires additional image-based investigations to further support the validity of the model.

Effects of Breath Training Pattern “End-Inspir atory Pause” on Respiratory Mechanics and Arterial Blood Gas of Pa tients with COPD

Objective: In order to explore the mechanism of C hinese traditional breath training, the effects of end-inspiratory pause br eathing (EIPB) on the respiratory mechanics and arterial blood gas were studied in patients with chronic obstructive pulmo nary disease (COPD).Methods: Ten patients in steady stage participating in the stud y had a breath training of regulating the respiration rhythm as to having a pause betw een the deep and slow inspiration and the slow expiration.Effect of the training was observed by visual feedback from the screen of the re spiratory inductive plethysmograph. The dynamic change of partial pressure of oxygen saturation in blood (SpO 2) was recorded with sphygmo-oximeter, the pulmonary mechanics and EIPB were determined with spirometer, and the data o f arterial blood gases in tranquilized breathing and EIPB were analysed.Results: After EIPB training, SpO 2 increased progressively, PaO 2 increased and PaCO 2 decreased, and the PaO 2 increment was greater than the PaCO 2 decrement. Furthermore, the tidal volume increased and the frequency of respira tion decreased significantly, both inspiration time and expiration time were prolonged. There was no significant change in both mean inspiration flow rate (VT/Ti) and expir ation flow rate (VT/Te). The baselines in spirogram during EIPB training had no raise. Conclusion: EIPB could decrease the ratio of the dead space and ti dal volume (VD/VT), cause increase of PaO 2 more than the decrease of PaCO 2, suggesting that this training could impro ve both the function of ventilation and gaseous exchange in the lung. EIPB training might be a breath ing training pattern for rehabilitation of patients with COPD.

Is COVID-19 different from other causes of acute respiratory distresssyndrome?

Coronavirus disease 2019(COVID-19)pneumonia can lead to acute hypoxemic respiratory failure.When mechanical ventilation is needed,almost all patients with COVID-19 pneumonia meet the criteria for acute respiratorydistress syndrome(ARDS).The question of the specificities of COVID-19-associated ARDS compared to othercauses of ARDS is of utmost importance,as it may justify changes in ventilatory strategies.This review aims todescribe the pathophysiology of COVID-19-associated ARDS and discusses whether specific ventilatory strategiesare required in these patients.

Effects of nursing team communication and collaboration on treatment outcomes in intensive care unit patients with severe pneumonia

BACKGROUND Severe pneumonia is a common severe respiratory infection worldwide,and its treatment is challenging,especially for patients in the intensive care unit(ICU).AIM To explore the effect of communication and collaboration between nursing teams on the treatment outcomes of patients with severe pneumonia in ICU.METHODS We retrospectively analyzed 60 patients with severe pneumonia who were treated at the ICU of the hospital between January 1,2021 and December 31,2023.We compared and analyzed the respiratory mechanical indexes[airway resistance(Raw),mean airway pressure(mPaw),peak pressure(PIP)],blood gas analysis indexes(arterial oxygen saturation,arterial oxygen partial pressure,and oxygenation index),and serum inflammatory factor levels[C-reactive protein(CRP),procalcitonin(PCT),cortisol(COR),and high mobility group protein B1(HMGB1)]of all patients before and after treatment.RESULTS Before treatment,there was no significant difference in respiratory mechanics index and blood gas analysis index between 2 groups(P>0.05).However,after treatment,the respiratory mechanical indexes of patients in both groups were significantly improved,and the improvement of Raw,mPaw,plateau pressure,PIP and other indexes in the combined group after communication and collaboration with the nursing team was significantly better than that in the single care group(P<0.05).The serum CRP and PCT levels of patients were significantly decreased,and the difference was statistically significant compared with that of nursing group alone(P<0.05).The levels of serum COR and HMGB1 before and after treatment were also significantly decreased between the two groups.CONCLUSION The communication and collaboration of the nursing team have a significant positive impact on respiratory mechanics indicators,blood gas analysis indicators and serum inflammatory factor levels in the treatment of severe pneumonia patients in ICU.