Respiratory Mechanics In Patients Research Articles

Respiratory Oscillometry in Patients With Acute Hypoxemic Respiratory Failure: A Feasibility Study.

Assessing respiratory mechanics in patients with acute hypoxemic respiratory failure who are not intubated could provide useful information about illness trajectory. Oscillometry is a respiratory function test used to measure total respiratory impedance during tidal breathing, which reveals resistive and elastic properties of the lung. This study assessed the feasibility of oscillometry in patients with acute hypoxemic respiratory failure and described their respiratory mechanics. Adult participants with acute hypoxemic respiratory failure who were receiving noninvasive respiratory support with [Formula: see text] ≥0.4 and flow ≥6 L/min underwent oscillometry at baseline and after resolution of acute hypoxemic respiratory failure. The primary end point was the number of participants who completed the baseline measurement. The feasibility criterion was in obtaining baseline oscillometry measurements in ≥80% of enrolled participants. Of 183 patients screened between July 2022 and August 2023, 29% were unable to cooperate due to altered mental state, 20% with extreme hypoxemia were excluded because of clinical instability, and 12% declined participation. Of the 10 participants (5.4%) recruited, all tolerated oscillometry measurements. At baseline, the median (minimum, maximum) [Formula: see text] was 0.8 (0.4, 0.8), median oxygen saturation of 94% dropped to a nadir of 82% at the end of oscillometry and recovered within 2 min. Lung reactance was increased, with a reactance area of 25 (15-32) cm H2O/L. Hypoxemia resolved in 9 participants. After resolution of acute hypoxemic respiratory failure in 8 (6-16) d, the median reactance area dropped to 15 (14-19) cm H2O/L. Respiratory mechanics in the participants with acute hypoxemic respiratory failure who were not intubated could be assessed by oscillometry in carefully selected cases.

How to Prevent Ventilator-Induced Lung Injury in Intraoperative Mechanical Ventilation? A Randomized Prospective Study.

Intraoperative mechanical ventilation practices can lead to ventilator-induced lung injury (VILI) and postoperative pulmonary complications in healthy lungs. Mechanical power (MP) has been developed as a new concept in reducing the risk of postoperative pulmonary complications as it considers all respiratory mechanics that cause VILI. The most commonly used intraoperative modes are volume control ventilation (VCV) and pressure control ventilation (PCV). In this study, VCV and PCV modes were compared in terms of respiratory mechanics in patients operated in the supine and prone positions. The patients were divided into 4 groups (80 patients), volume control supine and prone, pressure control supine and prone with 20 patients each. MP, respiratory rate, positive end-expiratory pressure, tidal volume, peak pressure, plato pressure, driving pressure, inspiratory time, height, age, gender, body mass index, and predictive body weight data of the patients included in the groups have been obtained from "electronic data pool" with Structured Query Language queries. The supine and prone MP values of the VCV group were statistically significantly lower than the PCV group (P values were 0.010 and 0.001, respectively). Supine and prone MP values of the VCV group were calculated significantly lower than the PCV group. Intraoperative PCV may be considered disadvantageous regarding the risk of VILI in the supine and prone positions.

Pronation Reveals a Heterogeneous Response of Global and Regional Respiratory Mechanics in Patients With Acute Hypoxemic Respiratory Failure.

Experimental models suggest that prone position and positive end-expiratory pressure (PEEP) homogenize ventral-dorsal ventilation distribution and regional respiratory compliance. However, this response still needs confirmation on humans. Therefore, this study aimed to assess the changes in global and regional respiratory mechanics in supine and prone positions over a range of PEEP levels in acute respiratory distress syndrome (ARDS) patients. A prospective cohort study. Twenty-two intubated patients with ARDS caused by COVID-19 pneumonia. Electrical impedance tomography and esophageal manometry were applied during PEEP titrations from 20 cm H2O to 6 cm H2O in supine and prone positions. Global respiratory system compliance (Crs), chest wall compliance, regional lung compliance, ventilation distribution in supine and prone positions. Compared with supine position, the maximum level of Crs changed after prone position in 59% of ARDS patients (n = 13), of which the Crs decreased in 32% (n = 7) and increased in 27% (n = 6). To reach maximum Crs after pronation, PEEP was changed in 45% of the patients by at least 4 cm H2O. After pronation, the ventilation and compliance of the dorsal region did not consistently change in the entire sample of patients, increasing specifically in a subgroup of patients who showed a positive change in Crs when transitioning from supine to prone position. These combined changes in ventilation and compliance suggest dorsal recruitment postpronation. In addition, the subgroup with increased Crs postpronation demonstrated the most pronounced difference between dorsal and ventral ventilation distribution from supine to prone position (p = 0.01), indicating heterogeneous ventilation distribution in prone position. Prone position modifies global respiratory compliance in most patients with ARDS. Only a subgroup of patients with a positive change in Crs postpronation presented a consistent improvement in dorsal ventilation and compliance. These data suggest that the response to pronation on global and regional mechanics can vary among ARDS patients, with some patients presenting more dorsal lung recruitment than others.

Effect of intravenous vs. inhaled penehyclidine on respiratory mechanics in patients during one-lung ventilation for thoracoscopic surgery: a prospective, double-blind, randomised controlled trial

BackgroundMinimising postoperative pulmonary complications (PPCs) after thoracic surgery is of utmost importance. A major factor contributing to PPCs is the driving pressure, which is determined by the ratio of tidal volume to lung compliance. Inhalation and intravenous administration of penehyclidine can improve lung compliance during intraoperative mechanical ventilation. Therefore, our study aimed to compare the efficacy of inhaled vs. intravenous penehyclidine during one-lung ventilation (OLV) in mitigating driving pressure and mechanical power among patients undergoing thoracic surgery.MethodsA double-blind, prospective, randomised study involving 176 patients scheduled for elective thoracic surgery was conducted. These patients were randomly divided into two groups, namely the penehyclidine inhalation group and the intravenous group before their surgery. Driving pressure was assessed at T1 (5 min after OLV), T2 (15 min after OLV), T3 (30 min after OLV), and T4 (45 min after OLV) in both groups. The primary outcome of this study was the composite measure of driving pressure during OLV. The area under the curve (AUC) of driving pressure from T1 to T4 was computed. Additionally, the secondary outcomes included mechanical power, lung compliance and the incidence of PPCs.ResultsAll 167 participants, 83 from the intravenous group and 84 from the inhalation group, completed the trial. The AUC of driving pressure for the intravenous group was 39.50 ± 9.42, while the inhalation group showed a value of 41.50 ± 8.03 (P = 0.138). The incidence of PPCs within 7 days after surgery was 27.7% in the intravenous group and 23.8% in the inhalation group (P = 0.564). No significant differences were observed in any of the other secondary outcomes between the two groups (all P > 0.05).ConclusionsOur study found that among patients undergoing thoracoscopic surgery, no significant differences were observed in the driving pressure and mechanical power during OLV between those who received an intravenous injection of penehyclidine and those who inhaled it. Moreover, no significant difference was observed in the incidence of PPCs between the two groups.

Relationship of Extravascular Lung Water and Pulmonary Vascular Permeability to Respiratory Mechanics in Patients with COVID-19-Induced ARDS

During acute respiratory distress syndrome (ARDS), the increase in pulmonary vascular permeability and lung water induced by pulmonary inflammation may be related to altered lung compliance. A better understanding of the interactions between respiratory mechanics variables and lung water or capillary permeability would allow a more personalized monitoring and adaptation of therapies for patients with ARDS. Therefore, our main objective was to investigate the relationship between extravascular lung water (EVLW) and/or pulmonary vascular permeability index (PVPI) and respiratory mechanic variables in patients with COVID-19-induced ARDS. This is a retrospective observational study from prospectively collected data in a cohort of 107 critically ill patients with COVID-19-induced ARDS from March 2020 to May 2021. We analyzed relationships between variables using repeated measurements correlations. We found no clinically relevant correlations between EVLW and the respiratory mechanics variables (driving pressure (correlation coefficient [CI 95%]: 0.017 [-0.064; 0.098]), plateau pressure (0.123 [0.043; 0.202]), respiratory system compliance (-0.003 [-0.084; 0.079]) or positive end-expiratory pressure (0.203 [0.126; 0.278])). Similarly, there were no relevant correlations between PVPI and these same respiratory mechanics variables (0.051 [-0.131; 0.035], 0.059 [-0.022; 0.140], 0.072 [-0.090; 0.153] and 0.22 [0.141; 0.293], respectively). In a cohort of patients with COVID-19-induced ARDS, EVLW and PVPI values are independent from respiratory system compliance and driving pressure. Optimal monitoring of these patients should combine both respiratory and TPTD variables.

Effect of endotracheal tube size on airway resistance and dynamic lung compliance.

There are different results on the effect of endotracheal tube (ETT) size on respiratory mechanics in patients undergoing mechanical ventilation, and there are few reports in adult laparoscopic surgery. The aim of this study was to investigate the effect of ETT size on airway resistance (RAW) and dynamic lung compliance (COMPL) in patients undergoing laparoscopic colorectal surgery. Seventy-two patients undergoing laparoscopic radical surgery for colorectal cancer under general anesthesia with endotracheal intubation were selected and divided into 3 groups (n = 24) using the random number table method Group A (ETT ID 7.0), Group B (ETT ID 7.5), and Group C (ETT ID 8.0). After mechanical ventilation, intraoperative RAW and COMPL were monitored in each of the 3 groups. In the non-pneumoperitoneal state, RAW in group ID7.0 is significantly higher than this in group ID7.5 and group ID8.0 (P < .05); the RAW between the 2 groups with ID7.5 and ID8.0 was not statistically significant (P > .05). The difference of COMPL between the 3 groups was statistically significant (P < .05); the COMPL of Group ID7.0 is lower than Group ID7.5, and Group ID7.5 is lower than Group ID8.0. In the pneumoperitoneal state, the RAW between ID7.0 group and ID8.0 group was statistically significant, the RAW difference between ID7.0 group and ID7.5 group, ID7.5 group and ID8.0 group not statistically significant (P > .05);the COMPL between the 3 groups was not statistically significant (P > .05). In the non-pneumoperitoneal state, the smaller the ETT internal diameter within a certain range, the higher RAW and the lower COMPL; in the pneumoperitoneal state, the RAW with the ID7.0 ETT was higher than that with the ID8.0 ETT, and the ETT size within a certain range had no effect on COMPL.

Inspiratory Effort and Respiratory Mechanics in Patients with Acute Exacerbation of Idiopathic Pulmonary fibrosis: A Preliminary Matched Control Study

BackgroundPatients with acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) may experience severe acute respiratory failure, even requiring ventilatory assistance. Physiological data on lung mechanics during these events are lacking. MethodsPatients with AE-IPF admitted to Respiratory Intensive Care Unit to receive non-invasive ventilation (NIV) were retrospectively analyzed. Esophageal pressure swing (ΔPes) and respiratory mechanics before and after 2 hours of NIV were collected as primary outcome. The correlation between positive end-expiratory pressure (PEEP) levels and changes of in dynamic compliance (dynCRS) and PaO2/FiO2 ratio was assessed. Further, an exploratory comparison with a historical cohort of ARDS patients matched 1:1 by age, sequential organ failure assessment score, body mass index and PaO2/FiO2 level was performed. ResultsAt baseline, AE-IPF patients presented a high respiratory drive activation with ΔPes = 27 (21–34) cmH2O, respiratory rate (RR) = 34 (30–39) bpm and minute ventilation (VE) = 21 (20–26) L/min. Two hours after NIV application, ΔPes, RR and VE values showed a significant reduction (16 [14–24] cmH2O, p<0.0001, 27 [25–30] bpm, p=0.001, and 18 [17–20] L/min, p=0.003, respectively) while no significant change was found in dynamic transpulmonary pressure, expiratory tidal volume (Vte), dynCRS and dynamic mechanical power. PEEP levels negatively correlated with PaO2/FiO2 ratio and dynCRS (r=–0.67, p=0.03 and r=–0.27, p=0.4, respectively). When compared to AE-IPF, ARDS patients presented lower baseline ΔPes, RR, VE and dynamic mechanical power. Differently from AE-IPF, in ARDS both Vte and dynCRS increased significantly following NIV (p=0.01 and p=0.004 respectively) with PEEP levels directly associated with PaO2/FiO2 ratio and dynCRS (r=0.24, p=0.5 and r=0.65, p=0.04, respectively). ConclusionsIn this study, patients with AE-IPF showed a high inspiratory effort, whose intensity was reduced by NIV application without a significant improvement in respiratory mechanics. In an exploratory analysis, AE-IPF patients showed a different mechanical behavior under spontaneous unassisted and assisted breathing compared with ARDS patients of similar severity.

Partition of respiratory mechanics in patients with acute respiratory distress syndrome and association with outcome: a multicentre clinical study.

PurposeIn acute respiratory distress syndrome (ARDS), physiological parameters associated with outcome may help defining targets for mechanical ventilation. This study aimed to address whether transpulmonary pressures (PL), including transpulmonary driving pressure (DPL), elastance-derived plateau PL, and directly-measured end-expiratory PL, are better associated with 60-day outcome than airway driving pressure (DPaw). We also tested the combination of oxygenation and stretch index [PaO2/(FiO2*DPaw)].MethodsProspective, observational, multicentre registry of ARDS patients. Respiratory mechanics were measured early after intubation at 6 kg/ml tidal volume. We compared the predictive power of the parameters for mortality at day-60 through receiver operating characteristic (ROC) and assessed their association with 60-day mortality through unadjusted and adjusted Cox regressions. Finally, each parameter was dichotomized, and Kaplan–Meier survival curves were compared.Results385 patients were enrolled 2 [1–4] days from intubation (esophageal pressure and arterial blood gases in 302 and 318 patients). As continuous variables, DPaw, DPL, and oxygenation stretch index were associated with 60-day mortality after adjustment for age and Sequential Organ Failure Assessment, whereas elastance-derived plateau PL was not. DPaw and DPL performed equally in ROC analysis (P = 0.0835). DPaw had the best-fit Cox regression model. When dichotomizing the variables, DPaw ≥ 15, DPL ≥ 12, plateau PL ≥ 24, and oxygenation stretch index < 10 exhibited lower 60-day survival probability. Directly measured end-expiratory PL ≥ 0 was associated with better outcome in obese patients.ConclusionDPL was equivalent predictor of outcome than DPaw. Our study supports the soundness of limiting lung and airway driving pressure and maintaining positive end-expiratory PL in obese patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00134-022-06724-y.

Comparison of the Effects of Normocapnia and Mild Hypercapnia on the Optic Nerve Sheath Diameter and Regional Cerebral Oxygen Saturation in Patients Undergoing Gynecological Laparoscopy with Total Intravenous Anesthesia.

Cerebral hemodynamics may be altered by hypercapnia during a lung-protective ventilation (LPV), CO2 pneumoperitoneum, and Trendelenburg position during general anesthesia. The purpose of this study was to compare the effects of normocapnia and mild hypercapnia on the optic nerve sheath diameter (ONSD), regional cerebral oxygen saturation (rSO2), and intraoperative respiratory mechanics in patients undergoing gynecological laparoscopy under total intravenous anesthesia (TIVA). Sixty patients (aged between 19 and 65 years) scheduled for laparoscopic gynecological surgery in the Trendelenburg position. Patients under propofol/remifentanil total intravenous anesthesia were randomly assigned to either the normocapnia group (target PaCO2 = 35 mmHg, n = 30) or the hypercapnia group (target PaCO2 = 50 mmHg, n = 30). The ONSD, rSO2, and respiratory and hemodynamic parameters were measured at 5 min after anesthetic induction (Tind) in the supine position, and at 10 min and 40 min after pneumoperitoneum (Tpp10 and Tpp40, respectively) in the Trendelenburg position. There was no significant intergroup difference in change over time in the ONSD (p = 0.318). The ONSD increased significantly at Tpp40 when compared to Tind in both normocapnia and hypercapnia groups (p = 0.02 and 0.002, respectively). There was a significant intergroup difference in changes over time in the rSO2 (p < 0.001). The rSO2 decreased significantly in the normocapnia group (p = 0.01), whereas it increased significantly in the hypercapnia group at Tpp40 compared with Tind (p = 0.002). Alveolar dead space was significantly higher in the normocapnia group than in the hypercapnia group at Tpp40 (p = 0.001). In conclusion, mild hypercapnia during the LPV might not aggravate the increase in the ONSD during CO2 pneumoperitoneum in the Trendelenburg position and could improve rSO2 compared to normocapnia in patients undergoing gynecological laparoscopy with TIVA.

An assessment of esophageal balloon use for the titration of airway pressure release ventilation and controlled mechanical ventilation in a patient with extrapulmonary acute respiratory distress syndrome: a case report

BackgroundEsophageal pressure measurement is a minimally invasive monitoring process that assesses respiratory mechanics in patients with acute respiratory distress syndrome. Airway pressure release ventilation is a relatively new positive pressure ventilation modality, characterized by a series of advantages in patients with acute respiratory distress syndrome.Case presentationWe report a case of a 55-year-old chilean female, with preexisting hypertension and recurrent renal colic who entered the cardiosurgical intensive care unit with signs and symptoms of urinary sepsis secondary to a right-sided obstructive urolithiasis. At the time of admission, the patient showed signs of urinary sepsis, a poor overall condition, hemodynamic instability, tachycardia, hypotension, and needed vasoactive drugs. Initially the patient was treated with volume control ventilation. Then, ventilation was with conventional ventilation parameters described by the Acute Respiratory Distress Syndrome Network. However, hemodynamic complications led to reduced airway pressure. Later she presented intraabdominal hypertension that compromised the oxygen supply and her ventilation management. Considering these records, an esophageal manometry was used to measure distending lung pressure, that is, transpulmonary pressure, to protect lungs. Initial use of the esophageal balloon was in a volume-controlled modality (deep sedation), which allowed the medical team to perform inspiratory and expiratory pause maneuvers to monitor transpulmonary plateau pressure as a substitute for pulmonary distension and expiratory pause and determine transpulmonary positive end-expiratory pressure. On the third day of mechanical respiration, the modality was switched to airway pressure release ventilation. The use of airway pressure release ventilation was associated with reduced hemodynamic complications and kept transpulmonary pressure between 0 and 20 cmH2O despite a sustained high positive end-expiratory pressure of 20 cmH2O.ConclusionThe application of this technique is shown in airway pressure release ventilation with spontaneous ventilation, which is then compared with a controlled modality that requires a lesser number of sedative doses and vasoactive drugs, without altering the criteria for lung protection as guided by esophageal manometry.

Comparison of the effects between low-level assisted ventilation and T-piece method on respiratory mechanics during weaning of mechanically ventilated patients

To compare the difference of low-level assisted ventilation and T-piece method on respiratory mechanics of patients with invasive mechanical ventilation during spontaneous breathing trial (SBT) within 3 days before extubation. A retrospective observational study was conducted. Twenty-five patients with difficulty in weaning or delayed weaning from invasive mechanical ventilation who were admitted to department of critical care medicine of the First Affiliated Hospital of Guangzhou Medical University from December 2018 to June 2020, and were in stable condition and entered the weaning stage after more than 72 hours of invasive mechanical ventilation were studied. A total of 119 cases of respiratory mechanical indexes were collected, which were divided into the low-level assisted ventilation group and the T-piece group according to the ventilator method and parameters used during the data collection. The different ventilation modes related respiratory mechanics indexes such as the esophageal pressure (Pes), the gastric pressure (Pga), the transdiaphragmatic pressure (Pdi), the maximum Pdi (Pdimax), Pdi/Pdimax ratio, the esophageal pressure-time product (PTPes), the gastric pressure-time product (PTPga), the transdiaphragmatic pressure-time product (PTPdi), the diaphragmatic electromyography (EMGdi), the maximum diaphragmatic electromyography (EMGdimax), PTPdi/PTPes ratio, Pes/Pdi ratio, the inspiratory time (Ti), the expiratory time (Te) and the total time respiratory cycle (Ttot) at the end of monitoring were recorded and compared between the two groups. Compared with the T-piece group, Pes, PTPes, PTPdi/PTPes ratio, Pes/Pdi ratio and Te were higher in low-level assisted ventilation group [Pes (cmH2O, 1 cmH2O = 0.098 kPa): 2.84 (-1.80, 5.83) vs. -0.94 (-8.50, 2.06), PTPes (cmH2O×s×min-1): 1.87 (-2.50, 5.93) vs. -0.95 (-9.71, 2.56), PTPdi/PTPes ratio: 0.07 (-1.74, 1.65) vs. -1.82 (-4.15, -1.25), Pes/Pdi ratio: 0.17 (-0.43, 0.64) vs. -0.47 (-0.65, -0.11), Te (s): 1.65 (1.36, 2.18) vs. 1.33 (1.05, 1.75), all P < 0.05], there were no significant differences in Pga, Pdi, Pdimax, Pdi/Pdimax ratio, PTPga, PTPdi, EMGdi, EMGdimax, Ti and Ttot between the T-piece group and the low-level assisted pressure ventilation group [Pga (cmH2O): 6.96 (3.54,7.60) vs. 7.74 (4.37, 11.30), Pdi (cmH2O): 9.24 (4.58, 17.31) vs. 6.18 (2.98, 11.96), Pdimax (cmH2O): 47.20 (20.60, 52.30) vs. 29.95 (21.50, 47.20), Pdi/Pdimax ratio: 0.25 (0.01, 0.34) vs. 0.25 (0.12, 0.41), PTPga (cmH2O×s×min-1): 7.20 (2.54, 9.97) vs. 7.97 (5.74, 13.07), PTPdi (cmH2O×s×min-1): 12.15 (2.95, 19.86) vs. 6.87 (2.50, 12.63), EMGdi (μV): 0.05 (0.03, 0.07) vs. 0.04 (0.02, 0.06), EMGdimax (μV): 0.07 (0.05, 0.09) vs. 0.07 (0.04, 0.09), Ti (s): 1.20 (0.95, 1.33) vs. 1.07 (0.95, 1.33), Ttot (s): 2.59 (2.22, 3.09) vs. 2.77 (2.35, 3.24), all P > 0.05]. When mechanically ventilated patients undergo SBT, the use of T-piece method increases the work of breathing compared with low-level assisted ventilation method. Therefore, long-term use of T-piece should be avoided during SBT.

Continuous positive airway pressure improves respiratory mechanics and efficiency of neural drive in stable COPD: an exploratory study.

BackgroundContinuous positive airway pressure (CPAP) is a major treatment strategy for severe chronic obstructive pulmonary disease (COPD), especially with respiratory failure. However, it remains inconclusive whether CPAP affects respiratory mechanics and neural drive in stable COPD patients without respiratory failure.MethodsTwenty-two COPD patients without respiratory failure received CPAP starting from 4 to 10 cmH2O in 1 cmH2O increments. Respiratory pattern, end expiatory lung volume (EELV), dynamic PEEPi (PEEPidyn), airway resistance (Raw), pressure-time product of diaphragmatic pressure (PTPdi) and esophageal pressure (PTPeso), root mean square (RMS) of diaphragm electromyogram (EMGdi) and ratio of ventilation (Ve) to EMGdi (i.e., Ve/RMS) were measured before and at each level of continue positive airway pressure (CPAP). A subgroup analysis was performed between patients with and without inspiratory muscle weakness.ResultsNineteen patients completed the treatment. The respiratory pattern improved significantly after CPAP. Raw, PTPdi, and Pdi decreased significantly. ΔEELV decreased at 4 cmH2O (P<0.05), but increased significantly at >8 cmH2O. PEEPidyn decreased from 2.18±0.98 to 1.37±0.55 cmH2O. RMS increased while Ve/RMS improved significantly after CPAP (P<0.05). Besides, CPAP could significantly improve respiratory mechanics in patients with inspiratory muscle weakness.ConclusionsCPAP improves respiratory pattern, PEEPi, Raw, work of breathing and efficiency of neural drive in COPD patients without respiratory failure, but easily increases dynamic pulmonary hyperinflation. These effects on respiratory mechanics are significant in patients with inspiratory muscle weakness.

Effects of ventilatory strategy on arterial oxygenation and respiratory mechanics in overweight and obese patients undergoing posterior spine surgery

Prolonged inspiratory to expiratory (I:E) ratio ventilation may improve arterial oxygenation or gas exchange and respiratory mechanics in patients with obesity. We performed a randomised study to compare the effects of the conventional ratio ventilation (CRV) of 1:2 and the equal ratio ventilation (ERV) of 1:1 on arterial oxygenation and respiratory mechanics during spine surgery in overweight and obese patients. Fifty adult patients with a body mass index of ≥25 kg/m2 were randomly allocated to receive an I:E ratio either l:2 (CRV; n = 25) or 1:1 (ERV; n = 25). Arterial oxygenation and respiratory mechanics were recorded in the supine position, and at 30 minutes and 90 minutes after placement in the prone position. The changes in partial arterial oxygen pressure (PaO2) over time did not differ between the groups. The changes in partial arterial carbon dioxide pressure over time were significantly different between the two groups (P = 0.040). The changes in mean airway pressure (Pmean) over time were significantly different between the two groups (P = 0.044). Although ERV provided a significantly higher Pmean than CRV during surgery, the changes in PaO2 did not differ between the two groups.

P4509The cardiopulmonary vicious cycle in patients with heart failure, a mechanism for accelerated decompensation

Abstract Background Hemodynamic congestion appears days prior to the development of clinical congestion. Lung congestion is associated with increased respiratory effort and dyspnoea. The effects of increased respiratory effort on pulmonary circulation were not well-defined. Purpose The study investigates the cardiopulmonary interactions and the role of the respiratory effort in the development of decompensation. It is well-accepted that lung congestion affects the lung mechanics and increases the respiratory effort. On the other hand, changes in the intrathoracic and alveolar pressures, due to the increase in the respiratory effort, may have detrimental effects on the pulmonary circulation and the workloads of the heart. Methods We have simultaneously measured the hemodynamic indices and the respiratory mechanics in patients undergoing right heart catheterization (n=56) for the diagnosis of dyspnoea. The patients were classified either as heart failure (HF) or lung disease, according to their clinical history, symptoms and signs. The pulmonary capillary wedge pressure (PCWP) was decomposed into cardiac and respiratory waves. The respiratory effort (Presp) was defined as the respiratory wave amplitude that modulates the PCWP. Lung compliance was calculated as the ratio of the tidal volume to Presp. Results and discussion The HF patients (n=35) exhibited huge Presp of 9.6±3.7 mmHg [2.6–16.7], ∼4 fold the normal Presp, of about 2–3 mmHg (figure below). Their lung compliance decreased with increasing PCWP (2.0±0.4%/mmHg of PCWP). Both PCWP and pulmonary artery pressure (PAP) rose with Presp, by 0.92±0.36 mmHg and 1.68±0.47 mmHg, for 1 mmHg of Presp, respectively (Figure below). Interestingly, PCWP always exceeded Presp, leading to the stipulation of a novel fundamental constraint/law: the continuous pulmonary flow throughout the respiratory cycle requires that PCWP &gt; Presp (above the identity line in figure A), otherwise the capillary pressure will decrease below the surrounding alveolar pressure and the pulmonary circulation will collapse, especially during inspiration. This constraint imposes a positive feedback of Presp on the pulmonary circulatory pressures. It is also supported by the increase in PWCP with Presp in the patients with lung diseases (Figure A). The bigger rise in PAP than in PWCP is attributed to the increase in the pulmonary vascular resistance (PVR) with Presp (0.3±0.06 wood units for 1mmHg Presp). The latter constructs additional positive feedback of Presp on the cardiac workload. A decrease in the intrathoracic pressure that surrounds the heart increases the LV apparent afterload. The increase in PAP and PVR elevates the right ventricle afterload. PCWP (A) and PAP (B) vs. Presp Conclusions The respiratory effort is not just a hallmark of HF but plays a pivotal role in the cardiopulmonary vicious cycle. An increase in the respiratory effort increases the PWCP, PAP, PVR, and the afterloads of both ventricles, and thereby may accelerate cardiac decompensation.

Respiratory resistance and reactance in adults with sickle cell anemia: Part 2-Fractional-order modeling and a clinical decision support system for the diagnosis of respiratory disorders.

BackgroundA better understanding of sickle cell anemia (SCA) and improvements in drug therapy and health policy have contributed to the emergence of a large population of adults living with this disease. The mechanisms by which SCA produces adverse effects on the respiratory system of these patients are largely unknown. Fractional-order (FrOr) models have a high potential to improve pulmonary clinical science and could be useful for diagnostic purposes, offering accurate models with an improved ability to mimic nature. Part 2 of this two-part study examines the changes in respiratory mechanics in patients with SCA using the new perspective of the FrOr models. These results are compared with those obtained in traditional forced oscillation (FOT) parameters, investigated in Part 1 of the present study, complementing this first analysis.Methodology/Principal findingsThe data consisted of three categories of subjects: controls (n = 23), patients with a normal spirometric exam (n = 21) and those presenting restriction (n = 24). The diagnostic accuracy was evaluated by investigating the area under the receiver operating characteristic curve (AUC). Initially, it was observed that biomechanical changes in SCA included increased values of fractional inertance, as well as damping and hysteresivity (p<0.001). The correlation analysis showed that FrOr parameters are associated with functional exercise capacity (R = -0.57), pulmonary diffusion (R = -0.71), respiratory muscle performance (R = 0.50), pulmonary flows (R = -0.62) and airway obstruction (R = 0.60). Fractional-order modeling showed high diagnostic accuracy in the detection of early respiratory abnormalities (AUC = 0.93), outperforming spirometry (p<0.03) and standard FOT analysis (p<0.01) used in Part 1 of this study. A combination of machine learning methods with fractional-order modeling further improved diagnostic accuracy (AUC = 0.97).ConclusionsFrOr modeling improved our knowledge about the biomechanical abnormalities in adults with SCA. Changes in FrOr parameters are associated with functional exercise capacity decline, abnormal pulmonary mechanics and diffusion. FrOr modeling outperformed spirometric and traditional forced oscillation analyses, showing a high diagnostic accuracy in the diagnosis of early respiratory abnormalities that was further improved by an automatic clinical decision support system. This finding suggested the potential utility of this combination to help identify early respiratory changes in patients with SCA.

Impulse оscillometry in the diagnosis of moderate airway obstruction

Background: Impulse oscillometry (IOS) is a non-invasive method for determining respiratory impedance and its parameters. IOS has certain advantages over traditional spirometry.&#x0D; Aim: To assess the potential of IOS in the diagnosis of moderately severe airway obstruction.&#x0D; Methods: We examined 53 patients divided in two groups. The first group consisted of 29 patients (26 males and 3 females aged 42 to 89 years) with moderately severe obstructive abnormalities; the second group included 24 patients (17 males and 7 females aged from 18 to 68 years) without ventilatory defects.&#x0D; Results: Obstructive abnormalities were detected by IOS in 93% of patients in group 1, and the severity of obstruction was more pronounced compared to the results of spirometry in 37% of patients. In group 2, the IOS parameters were normal. There were significant differences in the lung function and IOS parameters between the first and second groups. There were significant correlations between airway resistance and IOS parameters in patients with moderately severe obstructive abnormalities.&#x0D; Conclusion: Thus impulse oscillometry can be used in the clinical practice to diagnose disorders of respiratory mechanics in patients with moderately severe airway obstruction.

Respiratory mechanics in patients with acute respiratory distress syndrome.

Despite the recognition of its iatrogenic potential, mechanical ventilation remains the mainstay of respiratory support for patients with acute respiratory distress syndrome (ARDS). The low volume ventilation has been recognized as the only method to reduce mortality of ARDS patients and plateau pressure as the lighthouse for delivering safe ventilation. Recent investigations suggest that a ventilation based on lung mechanics (tidal ventilation tailored to the available lung volume able to receive it, i.e., driving pressure) is a successful approach to improve outcome. However, currently available bedside mechanical variables do not consider regional mechanical properties of ARDS affected lungs, which include the role of local stress risers at the boundaries of areas with different aeration. A unifying approach considers lung-related causes and ventilation-related causes of lung injury. These last may be incorporated in the mechanical power (i.e., amount of mechanical energy transferred per unit of time). Ventilation-induced lung injury (which includes the self-inflicted lung injury of a spontaneously breathing patient) can therefore be prevented by the adoption of measures promoting an increase of ventilable lung and its homogeneity and by delivering lower levels of mechanical power. Prone position promotes lung homogeneity without increasing the delivered mechanical power. This review describes the recent developments on respiratory mechanics in ARDS patients, providing both bedside and research insights from the most updated evidence.

Evaluation of Inhaled Procaterol for Potential Assist Use in Patients with Stable Chronic Obstructive Pulmonary Disease

Objectives: International guidelines recommend the use of long-acting bronchodilators for the treatment of chronic obstructive pulmonary disease (COPD), but the usefulness of short-acting bronchodilator assist use for stable COPD remains uncertain. The purpose of the present study was to objectively demonstrate the effects of assist use of procaterol, a short-acting β₂-agonist, on the respiratory mechanics of stable COPD patients treated with a long-acting bronchodilator using forced oscillation technique (FOT) and conventional spirometry. We also confirmed the length of time for which procaterol assist could significantly improve the pulmonary function. Methods: We enrolled 28 outpatients with mild to severe COPD (Global Initiative for Obstructive Lung Disease stages I–III), who had used the same long-acting bronchodilator for longer than 3 months and who were in stable condition. All measures were performed using both FOT and spirometry sequentially from 15 min to 2 h after inhalation. Results: Compared to baseline, inhaled procaterol assist use modestly but significantly improved spirometric and FOT measurements within 2 h after inhalation. These significant effects continued for at least 2 h. ­Significant correlations were found between parameters ­measured by spirometry and those measured by FOT. Conclusions: Procaterol assist use modestly but significantly improved pulmonary function determined by spirometry and respiratory mechanics in patients with stable COPD treated with long-acting bronchodilators. Thus, inhaled procaterol has the potential for assist use for COPD.

Implementing a bedside assessment of respiratory mechanics in patients with acute respiratory distress syndrome

BackgroundDespite their potential interest for clinical management, measurements of respiratory mechanics in patients with acute respiratory distress syndrome (ARDS) are seldom performed in routine practice. We introduced a systematic assessment of respiratory mechanics in our clinical practice. After the first year of clinical use, we retrospectively assessed whether these measurements had any influence on clinical management and physiological parameters associated with clinical outcomes by comparing their value before and after performing the test.MethodsThe respiratory mechanics assessment constituted a set of bedside measurements to determine passive lung and chest wall mechanics, response to positive end-expiratory pressure, and alveolar derecruitment. It was obtained early after ARDS diagnosis. The results were provided to the clinical team to be used at their own discretion. We compared ventilator settings and physiological variables before and after the test. The physiological endpoints were oxygenation index, dead space, and plateau and driving pressures.ResultsSixty-one consecutive patients with ARDS were enrolled. Esophageal pressure was measured in 53 patients (86.9%). In 41 patients (67.2%), ventilator settings were changed after the measurements, often by reducing positive end-expiratory pressure or by switching pressure-targeted mode to volume-targeted mode. Following changes, the oxygenation index, airway plateau, and driving pressures were significantly improved, whereas the dead-space fraction remained unchanged. The oxygenation index continued to improve in the next 48 h.ConclusionsImplementing a systematic respiratory mechanics test leads to frequent individual adaptations of ventilator settings and allows improvement in oxygenation indexes and reduction of the risk of overdistention at the same time.Trial registrationThe present study involves data from our ongoing registry for respiratory mechanics (ClinicalTrials.gov identifier: NCT02623192. Registered 30 July 2015).

Clinical study of the value in bronchoalveolar lavage in patients with severe lung infection by bed side painless fiberoptic bronchoscopy under chest CT guidance and mechanical ventilation

Objective To explore the effects of bed side painless fiberoptic bronchoscopy for bronchoalveolar lavage (BAL) under chest computed tomography (CT) guidance and mechanical ventilation in the patients with severe pulmonary infection (SPI) . Methods A total of 131 cases of SPI under mechanical ventilation support were randomly (random number) divided into CT group (C group) , chest X-ray examination group (X group) and without radiological examination group (N group) . The bronchoalveolar lavage (BAL) by using painless fiberoptic bronchoscopy with invasive mechanical ventilation was carried out in patients of these three groups. Vital signs and variables of respiratory mechanics of patients were monitored before and 1 h, 2 h, and 4 h after BAL and the time consumed for BAL was simultaneous recorded. Meanwhile, infection related biomarkers on the 3rdd and 5th d after BAL, positive detection rate of pathogenic bacteria, the time of invasive mechanical ventilation used during BAL and total duration of mechanical ventilation support were measured. Results During BAL and at 10 min after BAL, heart rate and respiratory rate of C group and X group were lower than those of N group (P 0.05) . One and two hours after BAL, peak inspiratory pressure (PIP) , work of breathing ventilation (WOBvent) and airway resistance (RAW) in C group and X group were lower than those in N group, therefore, dynamic compliance (Cdyn) in C and X groups was better than that in N group (P 0.05) . BAL time (BAL-t) in C group (16.81±2.62) min was shorter than that in X group (20.12±3.81) min and N group (23.69± 2.76) min, (P <0.05) . Three and five days after BAL, core body temperature, WBC and procalcitonin (PCT) in C and X group were lower than those in N group (P <0.05) , and those in C group was lower than those in X group (P <0.05) . Pathogenic micro-organism detection rate in C group (80.55%, 29/36) was higher than that in X group (72.09%, 31/43) and N group (59.65%, 34/57) (P <0.05) . Total mechanical ventilation time (MV-t) in C group (114.36±38.39) h was shorter than that in X group (132.07±42.51) h and N group (165.28±67.28) h (P<0.05) . Conclusions BAL by using painless fiberoptic bronchoscopy under chest CT guidance can effectively reduce the stress on patients with severe pulmonary infection supported with mechanical ventilation, decrease airway hyper-reactivity, shorten the BAL time, ICU stay and duration of mechanical ventilation, facilitate drainage of lung infection exudates and pathogen detection rate and improve efficacy of comprehensive treatment. Key words: CT chest; X-ray; Fiberoptic bronchoscopy; Bronchial lavage; Painless; Mechanical ventilation; Pulmonary infection; Intensive care unit