The effects of real-time waveform analysis software on patient ventilator synchronization during pressure support ventilation: a randomized crossover physiological study.

BACKGROUND: Patient-ventilator asynchrony commonly occurs during pressure support ventilation (PSV). IntelliSync + software (Hamilton Medical AG, Bonaduz, Switzerland) is a new ventilation technology that continuously analyzes ventilator waveforms to detect the beginning and end of patient inspiration in real time. This study aimed to evaluate the physiological effect of IntelliSync + software on inspiratory trigger delay time, delta airway (Paw) and esophageal (Pes) pressure drop during the trigger phase, airway occlusion pressure at 0.1 s (P0.1), and hemodynamic variables. METHODS: A randomized crossover physiologic study was conducted in 14 mechanically ventilated patients under PSV. Patients were randomly assigned to receive conventional flow trigger and cycling, inspiratory trigger synchronization (I-sync), cycle synchronization (C-sync), and inspiratory trigger and cycle synchronization (I/C-sync) for 15 min at each step. Other ventilator settings were kept constant. Paw, Pes, airflow, P0.1, respiratory rate, SpO2, and hemodynamic variables were recorded. The primary outcome was inspiratory trigger and cycle delay time between each intervention. Secondary outcomes were delta Paw and Pes drop during the trigger phase, P0.1, SpO2, and hemodynamic variables. RESULTS: The time to initiate the trigger was significantly shorter with I-sync compared to baseline (208.9±91.7 vs. 301.4±131.7 msec; P = 0.002) and I/C-sync compared to baseline (222.8±94.0 vs. 301.4±131.7 msec; P = 0.005). The I/C-sync group had significantly lower delta Paw and Pes drop during the trigger phase compared to C-sync group (-0.7±0.4 vs. -1.2±0.8 cmH2O; P = 0.028 and - 1.8±2.2 vs. -2.8±3.2 cmH2O; P = 0.011, respectively). No statistically significant differences were found in cycle delay time, P0.1 and other physiological variables between the groups. CONCLUSIONS: IntelliSync + software reduced inspiratory trigger delay time compared to the conventional flow trigger system during PSV mode. However, no significant improvements in cycle delay time and other physiological variables were observed with IntelliSync + software. TRIAL REGISTRATION: This study was registered in the Thai Clinical Trial Registry (TCTR20200528003; date of registration 28/05/2020).

Bronchodilator Efficacy of High-Flow Nasal Cannula in COPD: Vibrating Mesh Nebulizer Versus Jet Nebulizer.

BACKGROUND: Jet nebulizers are commonly used for bronchodilator therapy in COPD. High-flow nasal cannula with vibrating mesh nebulizer (HFNC-VMN) is a recently developed system; however, few studies have compared the efficacy of bronchodilator administration via HFNC-VMN to jet nebulizer in stable COPD. This study aimed to compare the effect of salbutamol administered via HFNC-VMN versus jet nebulizer on airway and lung function in subjects with stable COPD. METHODS: This randomized non-inferiority crossover physiologic study enrolled subjects with stable COPD. Salbutamol was nebulized via HFNC-VMN or jet nebulizer in random order with a 4-h washout period between crossover sequences. Spirometry, lung volume, and impulse oscillometry were performed at baseline and after each intervention. The primary outcome was change in FEV1 from baseline. Secondary outcomes included changes in other respiratory-related parameters and nebulization time compared between the 2 devices. RESULTS: Seventeen subjects were enrolled. HFNC-VMN and jet nebulizer both significantly improved FEV1 from baseline (P = .005 and P = .002, respectively). The difference between respiratory resistance at 5 Hz and 20 Hz significantly decreased after HFNC-VMN compared to baseline (P = .02), while no significant change was observed after jet nebulizer (P = .056). Area of reactance and resonant frequency of reactance were both significantly decreased (P = .035 and P = .03, respectively), and respiratory reactance at 5 Hz significantly increased (P = .02) in the HFNC-VMN group compared to baseline indicating improved lung mechanics, with no significant changes with the jet nebulizer. HFNC-VMN had a shorter nebulization time (6 [5-9] min vs 20 [16-22] min, respectively, P < .001). CONCLUSIONS: Bronchodilator therapy via HFNC-VMN was not inferior to jet nebulizer for subjects with stable COPD and can significantly improve airway oscillometry mechanics and decrease nebulization time compared to jet nebulizer.

Safety and efficacy of noninvasive ventilation for acute respiratory failure in general medical ward: a prospective cohort study.

Background: Noninvasive ventilation (NIV) is recommended for use in patients with acute respiratory failure of various etiologies. However, we do not know whether the use of NIV in general medical wards is safe and effective. This study aimed to evaluate the safety and efficacy of using NIV and factors associated with NIV failure in general medical wards. Methods: A prospective cohort study was conducted in general medical wards of the University Hospital. Adult patients with acute respiratory failure treated with NIV were enrolled. The subjects were managed by a multidisciplinary care team that was well trained in the NIV device. The primary outcome was the rate of NIV failure at 48 hours. Secondary outcomes included hospital mortality and factors associated with NIV failure. Results: A total of 86 patients were enrolled. The mean age was 70±17 years old. The Acute Physiology and Chronic Health Evaluation (APACHE) III and the Sequential Organ Failure Assessment (SOFA) scores were 56±17 and 4±3, respectively. The most common indication of NIV use was cardiogenic pulmonary edema (34.9%). The rate of NIV failure at 48 hours and hospital mortality were 20.9% and 12.8%, respectively. The SOFA score was associated with failure of NIV at 48 hours [odds ratio (OR) 1.48, 95% confidence interval (CI): 1.16-1.89; P=0.002]. Conclusions: NIV was safe and effective on general medical wards. Cardiogenic pulmonary edema was the most common indication for the application of NIV. The SOFA score was associated with the failure of NIV at 48 hours.

Number of attempts required by emergency physicians to achieve competency in diaphragmatic ultrasound imaging.

PURPOSE: This research aimed to determine the number of attempts that emergency physicians need to become proficient in undertaking diaphragmatic ultrasound imaging. METHODS: A prospective observational study was conducted at the emergency department (ED) of a tertiary-care university hospital. Sixteen emergency physicians were each required to obtain a set of images of the right hemidiaphragm of five dyspneic patients using both diaphragmatic excursion and thickness techniques. The images were subsequently reviewed by a specialist using American College of Emergency Physician guidelines. If the evaluations of a physician did not reach the expected standard, the physician was to be given feedback and requested to collect images from another five patients. The process was to be repeated until such time as the images obtained by the physician were deemed to be up to standard. RESULTS: Eighty patients, twelve emergency medicine residents, and four attending physicians were enrolled. Following a didactic session on diaphragmatic ultrasound imaging and its interpretation, practicing on five patients proved sufficient to achieve an adequate level of competency in conducting diaphragmatic ultrasound examinations. CONCLUSION: Practicing on five patients is sufficient for emergency physicians to achieve an adequate level of competency in conducting right-sided diaphragmatic ultrasound examinations.

Validation of rapid shallow breathing index displayed by the ventilator compared to the standard technique in patients with readiness for weaning.

BACKGROUND: Rapid shallow breathing index (RSBI) is the most commonly used parameter for predicting weaning outcome. Measurement of RSBI by Wright spirometer (RSBIstandard) is the standard method in routine clinical practice. Data specific to the accuracy and reliability of the RSBI value displayed by the ventilator (RSBIvent) are scarce. Accordingly, this study aimed to evaluate the association between the average value of RSBIvent at different time points and RSBIstandard, and to assess the accuracy and reliability of these two RSBI measurement techniques. METHODS: This prospective cohort study included mechanically ventilated patients who were ready to wean. At the beginning of spontaneous breathing trial using the flow-by method, RSBI was measured by two different techniques at the same time, including: (1) Wright spirometer (breathing frequency/average tidal volume in 1 min) (RSBIstandard), and (2) the values displayed on the ventilator at 0, 15, 30, 45, and 60 s (RSBIvent). RESULTS: Forty-seven patients were enrolled. The RSBIvent value was significantly higher than the RSBIstandard value for every comparison. According to Spearman's correlation coefficient (r) and intraclass correlation coefficient (ICC), the average value of RSBI from 5 time points (0, 15, 30, 45, and 60 s) showed the best correlation with the standard technique (r = 0.76 [P < 0.001], and ICC = 0.79 [95% CI 0.61-0.88], respectively). Bland-Altman plot also showed the best agreement between RSBIstandard and the RSBIvent value averaged among 5 time points (mean difference - 17.1 breaths/min/L). CONCLUSIONS: We found that the ventilator significantly overestimates the RSBI value compared to the standard technique by Wright spirometer. The average RSBIvent value among 5 time points (0, 15, 30, 45, and 60 s) was found to best correlate with RSBIstandard.

High-Flow Oxygen Therapy in Tracheostomized Subjects With Prolonged Mechanical Ventilation: A Randomized Crossover Physiologic Study.

BACKGROUND: High-flow oxygen therapy via tracheostomy (HFT) can be used in tracheostomized patients during ventilator disconnection. The physiologic effects of this technique are unknown. We hypothesized that HFT would reduce inspiratory effort and improve breathing pattern compared to conventional oxygen therapy via T-tube. This study aimed to evaluate the physiologic effects of HFT compared to conventional O2 in patients with prolonged mechanical ventilation. METHODS: A randomized crossover physiologic study was conducted in adult tracheostomized patients who experienced temporary periods of ventilator disconnection. Subjects were ventilated with pressure support ventilation (PSV) for 15 min and were then randomly assigned to HFT or conventional O2 via T-tube for 30 min. After a washout period, subjects were switched to the other system. Esophageal pressure (Pes), breathing frequency, blood pressure, heart rate, [Formula: see text], and transcutaneously measured pressure of carbon dioxide ([Formula: see text]) were recorded. The primary outcome was inspiratory effort as determined by the simplified esophageal pressure-time product (sPTPes). Secondary outcomes were Pes swing, breathing frequency, heart rate, mean arterial pressure, [Formula: see text], and [Formula: see text] between groups. RESULTS: Twenty-two subjects were enrolled: sPTPes per minute was significantly higher with HFT and conventional O2 compared to PSV (153.5 ± 97.9, 163.5 ± 111.3, and 86.8 ± 51.1 cm H2O × s/min, respectively, P = .001), but it was not different between HFT and conventional O2 (P = .72). Breathing frequency increased significantly after switching from PSV to HFT and conventional O2 (23 ± 4 vs 26 ± 6 and 23 ± 4 vs 27 ± 5 breaths/min, respectively, P = .001). [Formula: see text] was higher with conventional O2 compared to HFT (P = .02). No differences in [Formula: see text], mean arterial pressure, or heart rate were observed between HFT and conventional O2. CONCLUSIONS: Inspiratory effort and breathing frequency increased significantly during unassisted breathing compared to PSV in tracheostomized subjects, but HFT via tracheostomy provided no measurable additional physiologic benefit compared to O2 therapy via T-tube.

Duration of diaphragmatic inactivity after endotracheal intubation of critically ill patients.

BACKGROUND: In patients intubated for mechanical ventilation, prolonged diaphragm inactivity could lead to weakness and poor outcome. Time to resume a minimal diaphragm activity may be related to sedation practice and patient severity. METHODS: Prospective observational study in critically ill patients. Diaphragm electrical activity (EAdi) was continuously recorded after intubation looking for resumption of a minimal level of diaphragm activity (beginning of the first 24 h period with median EAdi > 7 µV, a threshold based on literature and correlations with diaphragm thickening fraction). Recordings were collected until full spontaneous breathing, extubation, death or 120 h. A 1 h waveform recording was collected daily to identify reverse triggering. RESULTS: Seventy-five patients were enrolled and 69 analyzed (mean age ± standard deviation 63 ± 16 years). Reasons for ventilation were respiratory (55%), hemodynamic (19%) and neurologic (20%). Eight catheter disconnections occurred. The median time for resumption of EAdi was 22 h (interquartile range 0-50 h); 35/69 (51%) of patients resumed activity within 24 h while 4 had no recovery after 5 days. Late recovery was associated with use of sedative agents, cumulative doses of propofol and fentanyl, controlled ventilation and age (older patients receiving less sedation). Severity of illness, oxygenation, renal and hepatic function, reason for intubation were not associated with EAdi resumption. At least 20% of patients initiated EAdi with reverse triggering. CONCLUSION: Low levels of diaphragm electrical activity are common in the early course of mechanical ventilation: 50% of patients do not recover diaphragmatic activity within one day. Sedatives are the main factors accounting for this delay independently from lung or general severity. Trial Registration ClinicalTrials.gov (NCT02434016). Registered on April 27, 2015. First patients enrolled June 2015.

The role for high flow nasal cannula as a respiratory support strategy in adults: a clinical practice guideline.

PURPOSE: High flow nasal cannula (HFNC) is a relatively recent respiratory support technique which delivers high flow, heated and humidified controlled concentration of oxygen via the nasal route. Recently, its use has increased for a variety of clinical indications. To guide clinical practice, we developed evidence-based recommendations regarding use of HFNC in various clinical settings. METHODS: We formed a guideline panel composed of clinicians, methodologists and experts in respiratory medicine. Using GRADE, the panel developed recommendations for four actionable questions. RESULTS: The guideline panel made a strong recommendation for HFNC in hypoxemic respiratory failure compared to conventional oxygen therapy (COT) (moderate certainty), a conditional recommendation for HFNC following extubation (moderate certainty), no recommendation regarding HFNC in the peri-intubation period (moderate certainty), and a conditional recommendation for postoperative HFNC in high risk and/or obese patients following cardiac or thoracic surgery (moderate certainty). CONCLUSIONS: This clinical practice guideline synthesizes current best-evidence into four recommendations for HFNC use in patients with hypoxemic respiratory failure, following extubation, in the peri-intubation period, and postoperatively for bedside clinicians.

Use of nasal high flow oxygen during acute respiratory failure.

Nasal high flow (NHF) has gained popularity among intensivists to manage patients with acute respiratory failure. An important literature has accompanied this evolution. In this review, an international panel of experts assessed potential benefits of NHF in different areas of acute respiratory failure management. Analyses of the physiological effects of NHF indicate flow-dependent improvement in various respiratory function parameters. These beneficial effects allow some patients with severe acute hypoxemic respiratory failure to avoid intubation and improve their outcome. They require close monitoring to not delay intubation. Such a delay may worsen outcome. The ROX index may help clinicians decide when to intubate. In immunocompromised patients, NHF reduces the need for intubation but does not impact mortality. Beneficial physiological effects of NHF have also been reported in patients with chronic respiratory failure, suggesting a possible indication in acute hypercapnic respiratory failure. When intubation is required, NHF can be used to pre-oxygenate patients either alone or in combination with non-invasive ventilation (NIV). Similarly, NHF reduces reintubation alone in low-risk patients and in combination with NIV in high-risk patients. NHF may be used in the emergency department in patients who would not be offered intubation and can be better tolerated than NIV.

Ultrasound Evaluation of Diaphragm Force Reserve in Patients with Chronic Obstructive Pulmonary Disease.

Rationale: Diaphragm function is a key determinant of dyspnea in chronic obstructive pulmonary disease (COPD); however, it is rarely assessed in clinical practice. Lung hyperinflation can also impair diaphragm function. Ultrasound can assess the activity, function, and force reserve of the diaphragm.Objectives: To compare diaphragm activity, function, and force reserve among patients with COPD and healthy control subjects.Methods: Patients with stable COPD (n = 80) and healthy control subjects (n = 20) were enrolled (97% of them were men). Ultrasound was used to measure the thickening fraction of the diaphragm during tidal breathing and maximum volitional effort. Outcome measures were as follows: 1) the difference in diaphragm force reserve, activity, and function between patients with COPD and control subjects; 2) the correlation between lung volumes and diaphragm force reserve, activity, and function; and 3) the relationship between diaphragm force reserve and the rate of moderate to severe exacerbation of COPD.Results: The tidal thickening fraction of the diaphragm during resting breathing (TFdi-tidal) was higher in patients with COPD than in control subjects (P = 0.002); it was approximately twice as high in patients with severe COPD than in control subjects. Patients with COPD had poorer diaphragm function than control subjects as assessed by the maximal thickening fraction of the diaphragm during Muller maneuver (P < 0.01). Diaphragm force reserve ratio assessed by 1-(tidal thickening fraction of the diagphragm during resting breathing/maximal thickening fraction of the diaphragm) was lower in patients with COPD than in control subjects, and it fell with increasing Global Initiative for Chronic Obstructive Lung Disease stages (P < 0.001); it correlated with inspiratory capacity (r = 0.46) and the body mass index, airflow obstruction, dyspnea, exercise capacity (BODE) index, a multidimensional scoring system (r = -0.49). Patients who developed exacerbation during the following 2 years had less force reserve than patients without exacerbation (P = 0.024).Conclusions: Male patients with COPD have increased diaphragm workload, impaired diaphragm function, and reduced force reserve compared with healthy subjects. Ultrasound assessment of the diaphragm in COPD provides important functional information.Clinical trial registered with the Thai Clinical Trials Registry (TCTR20160411001). Registered 31 April 5, 2016.

Association of Low Baseline Diaphragm Muscle Mass With Prolonged Mechanical Ventilation and Mortality Among Critically Ill Adults.

Importance: Low diaphragm muscle mass at the outset of mechanical ventilation may predispose critically ill patients to poor clinical outcomes. Objective: To determine whether lower baseline diaphragm thickness (Tdi) is associated with delayed liberation from mechanical ventilation and complications of acute respiratory failure (reintubation, tracheostomy, prolonged ventilation >14 days, or death in the hospital). Design, Setting, and Participants: Secondary analysis (July 2018 to June 2019) of a prospective cohort study (data collected May 2013 to January 2016). Participants were 193 critically ill adult patients receiving invasive mechanical ventilation at 3 intensive care units in Toronto, Ontario, Canada. Exposures: Diaphragm thickness was measured by ultrasonography within 36 hours of intubation and then daily. Patients were classified as having low or high diaphragm muscle mass according to the median baseline Tdi. Main Outcomes and Measures: The primary outcome was time to liberation from ventilation accounting for the competing risk of death and adjusting for age, body mass index, severity of illness, sepsis, change in Tdi during ventilation, baseline comorbidity, and study center. Secondary outcomes included in-hospital death and complications of acute respiratory failure. Results: A total of 193 patients were available for analysis; the mean (SD) age was 60 (15) years, 73 (38%) were female, and the median (interquartile range) Sequential Organ Failure Assessment score was 10 (8-13). Median (interquartile range) baseline Tdi was 2.3 (2.0-2.7) mm. In the primary prespecified analysis, baseline Tdi of 2.3 mm or less was associated with delayed liberation from mechanical ventilation (adjusted hazard ratio for liberation, 0.51; 95% CI, 0.36-0.74). Lower baseline Tdi was associated a higher risk of complications of acute respiratory failure (adjusted odds ratio, 1.77; 95% CI, 1.20-2.61 per 0.5-mm decrement) and prolonged weaning (adjusted odds ratio, 2.30; 95% CI, 1.42-3.74). Lower baseline Tdi was also associated with a higher risk of in-hospital death (adjusted odds ratio, 1.47; 95% CI, 1.00-2.16 per 0.5-mm decrement), particularly after discharge from the intensive care unit (adjusted odds ratio, 2.68; 95% CI, 1.35-5.32 per 0.5-mm decrement). Conclusions and Relevance: In this study, low baseline diaphragm muscle mass in critically ill patients was associated with prolonged mechanical ventilation, complications of acute respiratory failure, and an increased risk of death in the hospital.

Airway Occlusion Pressure As an Estimate of Respiratory Drive and Inspiratory Effort during Assisted Ventilation.

Rationale: Monitoring and controlling respiratory drive and effort may help to minimize lung and diaphragm injury. Airway occlusion pressure (P0.1) is a noninvasive measure of respiratory drive.Objectives: To determine 1) the validity of "ventilator" P0.1 (P0.1vent) displayed on the screen as a measure of drive, 2) the ability of P0.1 to detect potentially injurious levels of effort, and 3) how P0.1vent displayed by different ventilators compares to a "reference" P0.1 (P0.1ref) measured from airway pressure recording during an occlusion.Methods: Analysis of three studies in patients, one in healthy subjects, under assisted ventilation, and a bench study with six ventilators. P0.1vent was validated against measures of drive (electrical activity of the diaphragm and muscular pressure over time) and P0.1ref. Performance of P0.1ref and P0.1vent to detect predefined potentially injurious effort was tested using derivation and validation datasets using esophageal pressure-time product as the reference standard.Measurements and Main Results: P0.1vent correlated well with measures of drive and with the esophageal pressure-time product (within-subjects R2 = 0.8). P0.1ref >3.5 cm H2O was 80% sensitive and 77% specific for detecting high effort (≥200 cm H2O ⋅ s ⋅ min-1); P0.1ref ≤1.0 cm H2O was 100% sensitive and 92% specific for low effort (≤50 cm H2O ⋅ s ⋅ min-1). The area under the receiver operating characteristics curve for P0.1vent to detect potentially high and low effort were 0.81 and 0.92, respectively. Bench experiments showed a low mean bias for P0.1vent compared with P0.1ref for most ventilators but precision varied; in patients, precision was lower. Ventilators estimating P0.1vent without occlusions could underestimate P0.1ref.Conclusions: P0.1 is a reliable bedside tool to assess respiratory drive and detect potentially injurious inspiratory effort.

Comparison of immunogenicity between intradermal and intramuscular injections of repeated annual identical influenza virus strains post-pandemic (2011-2012) in COPD patients.

We compared the antibody responses and persistence of the reduced-dose, 9 µg hemagglutinin (HA)/strain intradermal (ID) injection via the Mantoux technique and the 15 µg HA/strain intramuscular (IM) injection of the repeated annual identical trivalent, inactivated, split-virion vaccine 2011-2012 in chronic obstructive pulmonary disease (COPD) patients. Eighty patients were randomized to ID (n = 41) and IM (n = 39) groups. Four weeks post-vaccination, the antibody responses of the two groups were similar; those for influenza A(H1N1)pdm09 and influenza A(H3N2)-but not influenza B-met the criteria of the Committee for Proprietary Medicinal Products (CPMP). The antibody responses for influenza A(H1N1)pdm09 rapidly declined in both groups, especially with the ID injection, whereas those for influenza A(H3N2) maintained above the CPMP criteria throughout 12 months post-vaccination. The geometric mean titres for influenza A(H1N1)pdm09 persisted above the protective threshold (≥ 40) until 6 months post-vaccination in both the ID and IM groups. The seroprotection rates of the ID and IM groups were above 60% until 3 months and 6 months post-vaccination, respectively. In conclusion, the 9 µg HA/strain ID injection of vaccine 2011-2012 elicited antibody responses similar to the standard dose of 15 µg of the HA/strain IM injection at 4 weeks post-vaccination. However, the antibody responses for influenza A(H1N1)pdm09 rapidly declined, especially in the case of the ID injection, whereas they were comparable for influenza A(H3N2). Additional strategies for increasing vaccine durability should be considered, especially for new pandemic strains affecting elderly COPD patients.

Potential for Lung Recruitment Estimated by the Recruitment-to-Inflation Ratio in Acute Respiratory Distress Syndrome. A Clinical Trial.

Rationale: Response to positive end-expiratory pressure (PEEP) in acute respiratory distress syndrome depends on recruitability. We propose a bedside approach to estimate recruitability accounting for the presence of complete airway closure.Objectives: To validate a single-breath method for measuring recruited volume and test whether it differentiates patients with different responses to PEEP.Methods: Patients with acute respiratory distress syndrome were ventilated at 15 and 5 cm H2O of PEEP. Multiple pressure-volume curves were compared with a single-breath technique. Abruptly releasing PEEP (from 15 to 5 cm H2O) increases expired volume: the difference between this volume and the volume predicted by compliance at low PEEP (or above airway opening pressure) estimated the recruited volume by PEEP. This recruited volume divided by the effective pressure change gave the compliance of the recruited lung; the ratio of this compliance to the compliance at low PEEP gave the recruitment-to-inflation ratio. Response to PEEP was compared between high and low recruiters based on this ratio.Measurements and Main Results: Forty-five patients were enrolled. Four patients had airway closure higher than high PEEP, and thus recruitment could not be assessed. In others, recruited volume measured by the experimental and the reference methods were strongly correlated (R2 = 0.798; P < 0.0001) with small bias (-21 ml). The recruitment-to-inflation ratio (median, 0.5; range, 0-2.0) correlated with both oxygenation at low PEEP and the oxygenation response; at PEEP 15, high recruiters had better oxygenation (P = 0.004), whereas low recruiters experienced lower systolic arterial pressure (P = 0.008).Conclusions: A single-breath method quantifies recruited volume. The recruitment-to-inflation ratio might help to characterize lung recruitability at the bedside.Clinical trial registered with www.clinicaltrials.gov (NCT02457741).

Effects of high-flow nasal cannula and non-invasive ventilation on inspiratory effort in hypercapnic patients with chronic obstructive pulmonary disease: a preliminary study.

BACKGROUND: Non-invasive ventilation (NIV) is preferred as the initial ventilatory support to treat acute hypercapnic respiratory failure in patients with chronic obstructive pulmonary disease (COPD). High-flow nasal cannula (HFNC) may be an alternative method; however, the effects of HFNC in hypercapnic COPD are not well known. This preliminary study aimed at assessing the physiologic effects of HFNC at different flow rates in hypercapnic COPD and to compare it with NIV. METHODS: A prospective physiologic study enrolled 12 hypercapnic COPD patients who had initially required NIV, and were ventilated with HFNC at flow rates increasing from 10 to 50 L/min for 15 min in each step. The primary outcome was the effort to breathe estimated by a simplified esophageal pressure-time product (sPTPes). The other studied variables were respiratory rate, oxygen saturation (SpO2), and transcutaneous CO2 pressure (PtcCO2). RESULTS: Before NIV initiation, the median [interquartile range] pH was 7.36 [7.28-7.37] with a PaCO2 of 51 [42-60] mmHg. sPTPes per minute was significantly lower with HFNC at 30 L/min than 10 and 20 L/min (p < 0.001), and did not significantly differ with NIV (median inspiratory/expiratory positive airway pressure of 11 [10-12] and [5-5] cmH2O, respectively). At 50 L/min, sPTPes per minute increased compared to 30 L/min half of the patients. Respiratory rate was lower (p = 0.003) and SpO2 was higher (p = 0.028) with higher flows (30-50 L/min) compared to flow rate of 10 L/min and not different than with NIV. No significant differences in PtcCO2 between NIV and HFNC at different flow rates were observed (p = 0.335). CONCLUSIONS: Applying HFNC at 30 L/min for a short duration reduces inspiratory effort in comparison to 10 and 20 L/min, and resulted in similar effect than NIV delivered at modest levels of pressure support in hypercapnic COPD with mild to moderate exacerbation. Higher flow rates reduce respiratory rate but sometimes increase the effort to breathe. Using HFNC at 30 L/min in hypercapnic COPD patients should be further evaluated. Trial registration Thai Clinical Trials Registry, TCTR20160902001. Registered 31 August 2016, http://www.clinicaltrials.in.th/index.php?tp=regtrials&menu=trialsearch&smenu=fulltext&task=search&task2=view1&id=2008 .

Sleep and Pathological Wakefulness at the Time of Liberation from Mechanical Ventilation (SLEEWE). A Prospective Multicenter Physiological Study.

Rationale: Abnormal patterns of sleep and wakefulness exist in mechanically ventilated patients. Objectives: In this study (SLEEWE [Effect of Sleep Disruption on the Outcome of Weaning from Mechanical Ventilation]), we aimed to investigate polysomnographic indexes as well as a continuous index for evaluating sleep depth, the odds ratio product (ORP), to determine whether abnormal sleep or wakefulness is associated with the outcome of spontaneous breathing trials (SBTs). Methods: Mechanically ventilated patients from three sites were enrolled if an SBT was planned the following day. EEG was recorded using a portable sleep diagnostic device 15 hours before the SBT. The ORP was calculated from the power of four EEG frequency bands relative to each other, ranging from full wakefulness (2.5) to deep sleep (0). The correlation between the right and left hemispheres' ORP (R/L ORP) was calculated. Measurements and Main Results: Among 44 patients enrolled, 37 had technically adequate signals: 11 (30%) passed the SBT and were extubated, 8 (21%) passed the SBT but were not deemed to be clinically ready for extubation, and 18 (49%) failed the SBT. Pathological wakefulness or atypical sleep were highly prevalent, but the distribution of classical sleep stages was similar between groups. The mean ORP and the proportion of time in which the ORP was >2.2 were higher in extubated patients compared with the other groups (P < 0.05). R/L ORP was significantly lower in patients who failed the SBT, and the area under the receiver operating characteristic curve of R/L ORP to predict failure was 0.91 (95% confidence interval, 0.75-0.98). Conclusions: Patients who pass an SBT and are extubated reach higher levels of wakefulness as indicated by the ORP, suggesting abnormal wakefulness in others. The hemispheric ORP correlation is much poorer in patients who fail an SBT.

The evolution of diaphragm activity and function determined by ultrasound during spontaneous breathing trials.

PURPOSE: Rapid shallow breathing index (RSBI) is a commonly used index for predicting the outcome of spontaneous breathing trial (SBT). Ultrasound is a non-invasive technique for assessing diaphragm activity and function. This study aimed to investigate changes in diaphragm activity during SBT, and to compare diaphragm function between patients with and without SBT success. MATERIALS AND METHODS: Forty-five patients undergoing SBT were enrolled. Thickening fraction of the diaphragm was assessed during tidal breathing (TFditidal), and RSBI was measured during 30 min of SBT. Diaphragm function measured by maximum TFdi (TFdimax) and diaphragmatic excursion (DEmax) was also evaluated. RESULTS: TFditidal and RSBI significantly increased during SBT (TFditidal0vs. TFditidal30 = 29.8 ±â€¯13.8 vs. 37.4 ±â€¯13.0%; p < .001, and RSBI0vs. RSBI30 = 64.8 ±â€¯25.9 vs.70.8 ±â€¯29.1 breaths/min/L; p = .034). In SBT failure (n = 13), there was no significant difference in TFditidal compared to SBT success, except at the beginning of the trial (p = .043); however, RSBI significantly increased throughout SBT. No differences in TFdimax or DEmax were observed between groups. CONCLUSIONS: Patient inspiratory efforts significantly increased during SBT. TFditidal measured by diaphragm ultrasound could not distinguish between patients with SBT success and failure. RSBI was significantly higher during SBT in patients with SBT failure.