BACKGROUND:Inspiratory muscle training (IMT) is used in a broad range of populations to improve the strength and endurance of the respiratory muscles, to improve both athletic performance and clinical outcomes. However, the optimal approach to IMT remains uncertain, and IMT is frequently declined in the clinical setting. This study aimed to measure oxygen consumption (VO2) and perceived difficulty and unpleasantness during commonly cited IMT loads. METHODS:Thirty participants performed IMT at 4cmH2O and 30%, 50% and 80% of their maximal inspiratory strength (PImax). VO2 was measured using indirect calorimetry. After each load, a visual analogue scale was used to rate breathing difficulty (VAS-D) and unpleasantness (VAS-U) RESULTS: Median (IQR) VO2 was 4.42 (3.36-4.82) mL/min/kg at baseline, increasing to 4.90 (4.11-5.03) mL/min/kg, 4.38 (3.69-5.23) mL/min/kg, 4.64 (4.09-5.28) mL/min/kg and (4.82-6.51) mL/min/kg after IMT at 4cmH2O and 30, 50 and 80% PImax respectively (Friedman's ANOVA p < 0.001). VO2 increased by 0.013 mL/kg/min for every 1% of PImax increase in IMT load. Perceived difficulty and unpleasantness increased with IMT load. PImax significantly influenced the load-perception relationship: slope (95% CI) of load versus VAS-D in the combined model 0.37 (0.09-0.65)mm/%PImax, p = 0.01), additional influence of baseline PImax 0.003 (0.001-0.005) mm/%PImax/cmH2O, p = 0.009. CONCLUSIONS:IMT causes a load-dependent increase in VO2, with marked increases in breathing difficulty and unpleasantness at higher loads. The additional impact of the absolute magnitude of load provides insight into the perception of respiratory effort. These data help understand the factors that influence IMT prescription, in terms of exercise response and acceptability.

Background Physical rehabilitation is advocated to improve muscle strength and function after critical illness, yet interventional studies have reported inconsistent benefits. A greater insight into patients’ physiological response to exercise may provide an option to prescribe individualised, targeted rehabilitation, yet there is limited data measuring oxygen consumption (VO2) during physical rehabilitation. We aimed to test the feasibility of measuring VO2 during seated and standing exercise using the Beacon Caresystem and quantify within- and between-patient variability of VO2 percentage change.Methods We conducted a prospective observational study on patients mechanically ventilated for ≥72 hours and able to participate in physical rehabilitation in critical care. Oxygen consumption was measured continuously using indirect calorimetry. A total of 29 measurements were taken from ten participants performing active sitting and standing exercise.Results Median (IQR) first session baseline VO2 was 3.54 (2.9–3.9) mL/kg/min, increasing significantly to 4.37 (3.96–5.14) mL/kg/min during exercise (p=0.005). The median (IQR) coefficient of variation of VO2 percentage change in participants (n=7) who completed more than one rehabilitation session (range 2–7 sessions) was 43 (34–61)% in 26 measurements. The median (IQR) coefficient of variation of VO2 percentage change was 46 (26–63)% in participants performing >1 sitting exercise session (six participants, 19 sessions).Conclusions VO2 increases significantly with exercise but is highly variable between participants, and in the same participant on separate occasions, performing the same functional activity. These data suggest that simplified measures of function do not necessarily relate to oxygen consumption.Trial registration number NCT05101850.

In biological fluids the charge is dominated by strong ions with pH-independent complete dissociation. The requirement of electroneutrality in combination with the principle of mass conservation and rules of dissociation as understood from physical chemistry including auto-dissociation of water allows definite specification of charge in any water-based fluid with known composition. Herein, two important publications are revisited using charge-balance modeling. In the first case it is shown that knowing a fixed pH difference between two types of fibroblasts and knowing also the pH-dependent buffer-capacities in the two cells allows quantitative assessment of buffer concentrations and strong ion differences. In the second example it is shown that the difficult problem of finding by calculation or titration the titratable acidity in urine modeled as a phosphate solution with high ionic strength can be solved with just measuring urine SID and total phosphate concentration without knowing either the correct dissociation constant or pH in urine. It is suggested that charge-balance modeling based on basic physical chemistry may reveal non-trivial ontological details of the system under study.

Objective:Analysis delay and gas contamination can affect the accuracy of blood measurements. This study uses a mathematical model of blood acid-base chemistry and gas in the sample tubes to calculate values of pH, partial pressures of carbon dioxide (pCO2), partial pressure of oxygen (pO2), oxygen saturation in whole blood (SO2), glucose, and lactate at sample time from measurements with delayed analysis and gas contamination. Methods:Data were analyzed from two published studies. Study 1: Samples were obtained from 30 critically ill patients in standard blood gas syringes and analyzed after 0, 36, 54, 72, 90, 108, 126, 144, 162, and 180 min. Study 2: Samples were taken from 20 healthy participants in standard blood gas syringes and vacuum tubes (2 mL and 4 mL) and analyzed after 0, 20, and 90 min. Calculated values from the mathematical model were compared to measured values at sample time. Results:For delays of up to 90 min, the accuracy (mean) and precision (standard deviation (SD)) values calculated at the sample time using syringes and 4-mL vacuum tubes remained within clinically acceptable limits when compared to measured values, with the exception of SO₂ in vacuum tubes. Values represent the mean difference ± standard deviation between calculated and measured values. For syringes, the results were as follows: pH = -0.004 ± 0.011, pCO₂ = 0.08 ± 0.18 kPa, pO₂ = 0.05 ± 0.34 kPa, SO₂ = 0.39 ± 2.21%, glucose = 0.07 ± 0.35 mmol/L, and lactate = 0.13 ± 0.22 mmol/L. For 4-mL vacuum tubes, the results were as follows: pH = 0.006 ± 0.007, pCO₂ = -0.07 ± 0.11 kPa, pO₂ = -0.37 ± 0.34 kPa, SO₂ = -7.79 ± 4.95%, glucose = 0.01 ± 0.11 mmol/L, and lactate = -0.00 ± 0.20 mmol/L. In addition, 2-mL vacuum tubes had poorer accuracy and precision values than syringes and 4-mL vacuum tubes in a subset of cases. Conclusion:This study has shown that a mathematical model can accurately and precisely calculate blood values at sample time, even following delayed analysis, using both standard blood gas syringes and selected vacuum tubes. This method may have clinical applications in improving the logistics of blood sampling and analysis.

Measurement of blood acid-base status is usually performed using standard blood gas syringes. This contrasts with venous blood for other purposes which are usually sampled in vacuum tubes which include a quantity of air. This study reports changes in blood sampled from normal participants over 90 min in standard blood gas syringes, and in vacuum tubes designed for blood gas sampling. It proposes a mathematical model based on physio-chemical processes to simulate changes occurring in the vacuum tubes due to contamination with air. Venous blood samples were taken from 20 normal participants, into standard blood gas syringes and analysed at baseline and 90 min; and 2 ml and 4 ml vacuum tubes analysed after 20 and 90 min. A mathematical model was proposed describing diffusion of O2 and CO2 between blood and gas phases of the vacuum tubes, and used to simulate corresponding measured values of plasma pH, pCO2, pO2, glucose, and lactate. Simulated and measured values were compared with Bland-Altman and correlation analysis. Differences between measured and model simulated values were (bias ± SD): pH -0.01 ± 0.01, pCO2 0.03 ± 0.17 kPa, pO2 0.88 ± 1.73 kPa, glucose -0.01 ± 0.11 mmol/l and lactate 0.06 ± 0.18 mmol/l. All linear correlations between measured and simulated values had R2 > 0.90. This paper illustrates that the effects of sampling in vacuum tubes can be accurately simulated with a mathematical model of physio-chemistry. While further evaluation is necessary, this may indicate a role for this model in the use of vacuum tubes for routine acid-base and oxygenation analysis.

OBJECTIVES:Measurements of acid-base status are performed quickly after blood sampling avoiding errors. This necessitates rapid sample transport which can be problematic. This study measures blood sampled in critically ill patients over 180 min and proposes a mathematical physio-chemical model to simulate changes. METHODS:Eleven blood samples were taken from 30 critically ill patients and measured at baseline (2 samples) and 36, 54, 72, 90, 108, 126, 144, 162, and 180 min. A mathematical model was proposed including red blood cell metabolism, carbon dioxide diffusion, electrolyte distribution and water transport. This model was used to simulate values of plasma pH, pCO2, pO2, SO2, glucose, lactate, Na+ and Cl- during analysis delay. Simulated and measured values were compared using Bland-Altman and correlation analysis, and goodness of model fits evaluated with chi-squared. RESULTS:The mathematical model provided a good fit to data in 29 of 30 patients with no significant differences (p>0.1) between simulated and measured plasma values. Differences were (bias±SD): pH 0.000 ± 0.012, pCO2 0.00 ± 0.24 kPa, lactate -0.10 ± 0.23 mmol/L, glucose 0.00 ± 0.34 mmol/L, Cl- -0.2 ± 1.21 mmol/L, Na+ 0.0 ± 1.0 mmol/L, pO2 0.0 ± 0.44 kPa, SO2 -0.6 ± 5.5 %, with these values close to manufacturers' measurement errors. All linear correlations had R2>0.86. Simulations of pH, PCO2, glucose and lactate could be performed from baseline values without patient specific parameters. CONCLUSIONS:This paper illustrates that analysis delay can be accurately simulated with a mathematical model of physio-chemistry. While further evaluation is necessary, this may indicate a role for this model in clinical practice to simulate analysis delay.

This study investigated the clinical and physiological response to use of the BEACON Caresystem, a bedside open-loop decision support system providing advice to guide clinicians when weaning patients from invasive mechanical ventilation. Multicenter prospective study conducted in five adult intensive care units in the UK. Following screening and assent, intubated patients mechanically ventilated for > 24 h were randomized to intervention or usual care. Intervention consisted of application of the BEACON Caresystem’s advice on tidal volume/inspiratory pressure, inspired oxygen, respiratory rate and PEEP. Usual care was defined as local clinical practice. The primary outcome was duration of mechanical ventilation. Secondary outcomes quantified prolonged intubation and survival; adverse events; ventilator settings and physiological state; time spent in ventilator modes; links to other therapy; the frequency of advice utilization and time spent outside normal physiological limits. The study was terminated early with a total of 112 patients included. Fifty-four were randomised to the intervention arm and fifty-eight to usual care. The study was underpowered and no significant differences were seen in duration of mechanical ventilation (p = 0.773), prolonged intubation or survival. Intervention arm patients had lower rates of adverse events (p = 0.016), including fewer hypoxaemic events (p = 0.008) and lower values of PEEP (p = 0.030) and tidal volume (p = 0.042). Values of peak inspiratory pressure and pressure support were reduced but at the boarder of statistical significance (p = 0.104, p = 0.093, respectively). No differences were seen for time in ventilator mode or other therapy. Advice presented by the decision support system was applied at the beside an average of 88

BackgroundAcute respiratory distress syndrome (ARDS) is highly heterogeneous, both in its clinical presentation and in the patient’s physiological responses to changes in mechanical ventilator settings, such as PEEP. This study investigates the clinical efficacy of a physiological model-based ventilatory decision support system (DSS) to personalize ventilator therapy in ARDS patients.MethodsThis international, multicenter, randomized, open-label study enrolled patients with ARDS during the COVID-19 pandemic. Patients were randomized to either receive active advice from the DSS (intervention) or standard care without DSS advice (control). The primary outcome was to detect a reduction in average driving pressure between groups. Secondary outcomes included several clinically relevant measures of respiratory physiology, ventilator-free days, time from control mode to support mode, number of changes in ventilator settings per day, percentage of time in control and support mode ventilation, ventilation- and device-related adverse events, and the number of times the advice was followed.ResultsA total of 95 patients were randomized in this study. The DSS showed no significant effect on average driving pressure between groups. However, patients in the intervention arm had a statistically improved oxygenation index when in support mode ventilation (−1.41, 95% CI: −2.76, −0.08; p = 0.0370). Additionally, the ventilatory ratio significantly improved in the intervention arm for patients in control mode ventilation (−0.63, 95% CI: −1.08, −0.17, p = 0.0068). The application of the DSS led to a significantly increased number of ventilator changes for pressure settings and respiratory frequency.ConclusionThe use of a physiological model-based decision support system for providing advice on mechanical ventilation in patients with COVID-19 and non-COVID-19 ARDS showed no significant difference in driving pressure as a primary outcome measure. However, the application of approximately 60% of the DSS advice led to improvements in the patient’s physiological state.Clinical trial registrationclinicaltrials.gov, NCT04115709.

BackgroundSeveral methods exist to reduce the number of arterial blood gases (ABGs). One method, Roche v-TAC, has been evaluated in different patient groups. This paper aggregates data from these studies, in different patient categories using common analysis criteria.Research design and methodsWe included studies evaluating v-TAC based on paired arterial and peripheral venous blood samples. Bland-Altman analysis compared measured and calculated arterial values of pH, PCO2, and PO2. Subgroup analyses were performed for normal, chronic hypercapnia and chronic base excess, acute hyper- and hypocapnia, and acute and chronic base deficits.Results811 samples from 12 studies were included. Bias and limits of agreement for measured and calculated values: pH 0.001 (-0.029 to 0.031), PCO2 -0.08 (-0.65 to 0.49) kPa, and PO2 0.04 (-1.71 to 1.78) kPa, with similar values for all sub-group analyses.ConclusionThese data suggest that v-TAC analysis may have a role in replacing ABGs, avoiding arterial puncture. Substantial data exist in patients with chronic hypercapnia and chronic base excess, acute hyper- and hypocapnia, and in patients with relatively normal acid-base status, with similar bias and precision across groups and across study data. Limited data exist for patients with acute and chronic base deficits.

Invasive mechanical ventilation is a key supportive therapy for patients on intensive care. There is increasing emphasis on personalised ventilation strategies. Clinical decision support systems (CDSS) have been developed to support this. We conducted a narrative review to assess evidence that could inform device implementation.A search was conducted in MEDLINE (Ovid) and EMBASE. Twenty-nine studies met the inclusion criteria. Role allocation is well described, with interprofessional collaboration dependent on culture, nurse:patient ratio, the use of protocols, and perception of responsibility. There were no descriptions of process measures, quality metrics, or clinical workflow. Nurse-led weaning is well-described, with factors grouped by patient, nurse, and system. Physician-led weaning is heterogenous, guided by subjective and objective information, and ‘gestalt’. No studies explored decision-making with CDSS. Several explored facilitators and barriers to implementation, grouped by clinician (facilitators: confidence using CDSS, retaining decision-making ownership; barriers: undermining clinician's role, ambiguity moving off protocol), intervention (facilitators: user-friendly interface, ease of workflow integration, minimal training requirement; barriers: increased documentation time), and organisation (facilitators: system-level mandate; barriers: poor communication, inconsistent training, lack of technical support). One study described factors that support CDSS implementation.There are gaps in our understanding of ventilation practice. A coordinated approach grounded in implementation science is required to support CDSS implementation. Future research should describe factors that guide clinical decision-making throughout mechanical ventilation, with and without CDSS, map clinical workflow, and devise implementation toolkits. Novel research design analogous to a learning organisation, that considers the commercial aspects of device design, is required.

BACKGROUND:Postoperative pulmonary complications can increase hospital length of stay, postoperative morbidity, and mortality. Although many factors can increase the risk of postoperative pulmonary complications, it is not known whether intraoperative ventilation/perfusion (V/Q) mismatch can be associated with an increased risk of postoperative pulmonary complications after major noncardiac surgery. METHODS:This study enrolled patients undergoing general anesthesia for noncardiac surgery and evaluated intraoperative V/Q distribution using the automatic lung parameter estimator technique. The assessment was done after anesthesia induction, after 1 h from surgery start, and at the end of surgery. Demographic and procedural information were collected, and intraoperative ventilatory and hemodynamic parameters were measured at each timepoint. Patients were followed up for 7 days after surgery and assessed daily for postoperative pulmonary complication occurrence. RESULTS:The study enrolled 101 patients with a median age of 71 [62 to 77] years, a body mass index of 25 [22.4 to 27.9] kg/m2, and a preoperative Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) score of 41 [34 to 47]. Of these patients, 29 (29%) developed postoperative pulmonary complications, mainly acute respiratory failure (23%) and pleural effusion (11%). Patients with and without postoperative pulmonary complications did not differ in levels of shunt at T1 (postoperative pulmonary complications: 22.4% [10.4 to 35.9%] vs. no postoperative pulmonary complications:19.3% [9.4 to 24.1%]; P = 0.18) or during the protocol, whereas significantly different levels of high V/Q ratio were found during surgery (postoperative pulmonary complications: 13 [11 to 15] mmHg vs. no postoperative pulmonary complications: 10 [8 to 13.5] mmHg; P = 0.007) and before extubation (postoperative pulmonary complications: 13 [11 to 14] mmHg vs. no postoperative pulmonary complications: 10 [8 to 12] mmHg; P = 0.006). After adjusting for age, ARISCAT, body mass index, smoking, fluid balance, anesthesia type, laparoscopic procedure and surgery duration, high V/Q ratio before extubation was independently associated with the development of postoperative pulmonary complications (odds ratio, 1.147; 95% CI, 1.021 to 1.289; P = 0.02). The sensitivity analysis showed an E-value of 1.35 (CI, 1.11). CONCLUSIONS:In patients with intermediate or high risk of postoperative pulmonary complications undergoing major noncardiac surgery, intraoperative V/Q mismatch is associated with the development of postoperative pulmonary complications. Increased high V/Q ratio before extubation is independently associated with the occurrence of postoperative pulmonary complications in the first 7 days after surgery. EDITOR’S PERSPECTIVE:

BACKGROUND: Endotracheal suctioning causes discomfort, is associated with adverse effects, and is resource-demanding. An artificial secretion removal method, known as an automated cough, has been developed, which applies rapid, automated deflation, and inflation of the endotracheal tube cuff during the inspiratory phase of mechanical ventilation. This method has been evaluated in the hands of researchers but not when used by attending nurses. The aim of this study was to explore the efficacy of the method over the course of patient management as part of routine care. METHODS: This prospective, longitudinal, interventional study recruited 28 subjects who were intubated and mechanically ventilated. For a maximum of 7 d and on clinical need for endotracheal suctioning, the automatic cough procedure was applied. The subjects were placed in a pressure-regulated ventilation mode with elevated inspiratory pressure, and automated cuff deflation and inflation were performed 3 times, with this repeated if deemed necessary. Success was determined by resolution of the clinical need for suctioning as determined by the attending nurse. Adverse effects were recorded. RESULTS: A total of 84 procedures were performed. In 54% of the subjects, the artificial cough procedure was successful on > 70% of occasions, with 56% of all procedures considered successful. Ninety percent of all the procedures were performed in subjects who were spontaneously breathing and on pressure-support ventilation with peak inspiratory pressures of 20 cm H2O. Rates of adverse events were similar to those seen in the application of endotracheal suctioning. CONCLUSIONS: This study solely evaluated the efficacy of an automated artificial cough procedure, which illustrated the potential for reducing the need for endotracheal suctioning when applied by attending nurses in routine care.

It has been acknowledged for years that compounds containing sulfur (S) are an important source of endogenous acid production. In the metabolism, S is oxidized to sulfate, and therefore the mEq sulfate excreted in the urine is counted as acid retained in the body. In this study we show that pH in fluids with constant [Na] and [HEPES] declines as sulfate ions are added, and we show that titratable acidity increases exactly with the equivalents of sulfate. Therefore, sulfate excretion in urine is also acid excretion per se. This is in accordance with the down-regulation of proximal sulfate reabsorption under acidosis and the observation that children with distal renal tubular acidosis may be sulfate depleted. These results are well explained using charge-balance modeling, which is based only on the three fundamental principles of electroneutrality, conservation of mass, and rules of dissociation as devised from physical chemistry. In contrast, the findings are in contrast to expectations from conventional narratives. These are unable to understand the decreasing pH as sulfate is added since no conventional acid is present. The results may undermine the traditional notion of endogenous acid production since in the case of sulfur balance, S oxidation and its excretion as sulfate exactly balance each other. Possible clinical correlates with these findings are discussed.

Increased ventilatory work beyond working capacity of the respiratory muscles can induce fatigue, resulting in limited respiratory muscle endurance (T-lim). Previous resistive breathing investigations all applied square wave inspiratory pressure as fatigue-inducing pattern. Spontaneous breathing pressure pattern more closely approximate a triangle waveform. This study aimed at comparing T-lim, maximal inspiratory pressure (PImax), and metabolism between square and triangle wave breathing. Eight healthy subjects (Wei = 76 +/- 10 kg, H = 181 +/- 7.9 cm, age = 33.5 +/- 4.8 years, sex [F/M] = 1/7) completed the study, comprising two randomized matched load resistive breathing trials with square and triangle wave inspiratory pressure waveform. T-lim decreased with a mean difference of 8 +/- 7.2 min (p = 0.01) between square and triangle wave breathing. PImax was reduced following square wave (p = 0.04) but not for triangle wave breathing (p = 0.88). Higher VO2 was observed in the beginning and end for the triangle wave breathing compared with the square wave breathing (p = 0.036 and p = 0.048). Despite higher metabolism, T-lim was significantly longer in triangle wave breathing compared with square wave breathing, showing that the pressure waveform has an impact on the function and endurance of the respiratory muscles.

BACKGROUND: COVID-19–related ARDS is characterized by severe hypoxemia with initially preserved lung compliance and impaired ventilation/perfusion (V̇/Q̇) matching. PEEP can increase end-expiratory lung volume, but its effect on V̇/Q̇ mismatch in COVID-19–related ARDS is not clear. METHODS: We enrolled intubated and mechanically ventilated subjects with COVID-19 ARDS and used the automatic lung parameter estimator (ALPE) to measure V̇/Q̇. Respiratory mechanics measurements, shunt, and V̇/Q̇ mismatch (low V̇/Q̇ and high V̇/Q̇) were collected at 3 PEEP levels (clinical PEEP = intermediate PEEP, low PEEP [clinical − 50%], and high PEEP [clinical + 50%]). A mixed-effect model was used to evaluate the impact of PEEP on V̇/Q̇. We also investigated if PEEP might have a different effect on V̇/Q̇ mismatch in 2 different respiratory mechanics phenotypes, that is, high elastance/low compliance (phenotype H) and low elastance/high compliance (phenotype L). RESULTS: Seventeen subjects with COVID-related ARDS age 66 [60–71] y with a PaO2/FIO2 of 141 ± 74 mm Hg were studied at low PEEP = 5.6 ± 2.2 cm H2O, intermediate PEEP = 10.6 ± 3.8 cm H2O, and high PEEP = 15 ± 5 cm H2O. Shunt, low V̇/Q̇, high V̇/Q̇, and alveolar dead space were not significantly influenced, on average, by PEEP. Respiratory system compliance decreased significantly when increasing PEEP without significant variation of PaO2/FIO2 (P = .26). In the 2 phenotypes, PEEP had opposite effects on shunt, with a decrease in the phenotype L and an increase in phenotype H (P = .048). CONCLUSIONS: In subjects with COVID-related ARDS placed on invasive mechanical ventilation for > 48 h, PEEP had a heterogeneous effect on V̇/Q̇ mismatch and, on average, higher levels were not able to reduce shunt. The subject's compliance could influence the effect of PEEP on V̇/Q̇ mismatch since an increased shunt was observed in subjects with lower compliance, whereas the opposite occurred in those with higher compliance.

BACKGROUND:Laparoscopic surgery and Trendelenburg position may affect the respiratory function and alter the gas exchange. Further the reduction of the lung volumes may contribute to the development of expiratory flow limitation (EFL). The latter is associated with an increased risk of postoperative pulmonary complications. Our aim was to investigate the incidence of EFL and to evaluate its effect on pulmonary function and intraoperative V/Q mismatch.METHODS:This is a prospective study on patients undergoing elective laparoscopic gynecological surgery. We evaluated respiratory mechanics, V/Q mismatch and presence of EFL after anesthesia induction, during pneumoperitoneum and Trendelenburg position and at the end of surgery. Intraoperative gas exchange and hemodynamic were also recorded. Clinical data were collected until seven days after surgery to evaluate the onset of pulmonary postoperative complications (PPCs).RESULTS:Among the 66 patients enrolled, 25/66 (38%) exhibited EFL during surgery, of whom 10/66 (15%) after anesthesia induction, and the remaining 15 patients after pneumoperitoneum and Trendelenburg position. Median PEEP able to reverse flow limitation was 7 [7-10] cmH2O after anesthesia induction and 9 [8-15] cmH2O after pneumoperitoneum and Trendelenburg position. Patients with EFL had significantly higher shunt (17 [2-25] vs. 9 [1-19]; P=0.05), low V̇/Q̇ (27 [20-70] vs. 15 [10-22]; P=0.05) and high V̇/Q̇ (10 [7-14] vs. 6 [4-7]; P=0.024). At the end of surgery, only high V/Q was significantly higher in EFL patients. Further, they exhibited higher incidence of postoperative pulmonary complication (48% (12/25) vs. 15% (6/41), P=0.005), hypoxemia and hypercapnia (80% [20/25] vs. 32% [13/41]; P<0.001).CONCLUSIONS:Expiratory flow limitation is a common phenomenon during gynecological laparoscopic surgery associated with worsen gas exchange, increased V/Q mismatch and altered lung mechanics. Our study showed that patients experiencing EFL during surgery showed a higher risk for PPCs.

COPYRIGHT © 2023 Spadaro, Rees and Roca. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Editorial: New developments in mechanical ventilation

BACKGROUND:Endotracheal suctioning is resource demanding, causes patient discomfort, and is associated with adverse effects. A new artificial cough method has been developed for automated secretion removal by using rapid deflation and inflation of the endotracheal tube cuff during the inspiratory phase of mechanical ventilation. This method has been evaluated in a bench model and in animals but not in human subjects. The aim of this study was to investigate whether this method can remove the need for endotracheal suctioning in subjects and whether this is dependent on ventilator settings. METHODS:This prospective, non-controlled study recruited 20 subjects on invasive mechanical ventilation. On the clinical need for endotracheal suctioning, the automatic cough procedure was applied 3 times over 30 s, with this repeated at higher ventilatory pressure and lower respiratory frequency if considered unsuccessful. Success was determined by removal of the clinical need for suctioning. Subject safety and comfort was measured by using the Critical-Care Pain Observation Tool before and after the procedure, and negative effects were recorded. To assess intra-subject variability, the procedure was performed on 3 different occasions for each subject. RESULTS:The procedure was successful in 18 of 20 subjects (90%), with mean subject success rates of 53% at low settings (peak inspiratory pressure 21.8 ± 3.8 cm H2O) and 83% at high settings (peak inspiratory pressure 25.6 ± 3.6 cm H2O). The Critical-Care Pain Observation Tool category remained unchanged in 30 procedures (77%), improved in 7 (18%), and deteriorated in 2 (5%). CONCLUSIONS:This study illustrated the potential for significant reduction in the clinical need for endotracheal suctioning after the use of an automated artificial cough procedure at both low and high peak inspiratory pressures, and that was well tolerated.