Inspiratory Positive Airway Pressure Research Articles

Respiratory muscle activity and patient–ventilator asynchrony during different settings of noninvasive ventilation in stable hypercapnic COPD: does high inspiratory pressure lead to respiratory muscle unloading?

IntroductionHigh-intensity noninvasive ventilation (NIV) has been shown to improve outcomes in stable chronic obstructive pulmonary disease patients. However, there is insufficient knowledge about whether with this more controlled ventilatory mode optimal respiratory muscle unloading is provided without an increase in patient–ventilator asynchrony (PVA).Patients and methodsTen chronic obstructive pulmonary disease patients on home mechanical ventilation were included. Four different ventilatory settings were investigated in each patient in random order, each for 15 min, varying the inspiratory positive airway pressure and backup breathing frequency. With surface electromyography (EMG), activities of the intercostal muscles, diaphragm, and scalene muscles were determined. Furthermore, pressure tracings were derived simultaneously in order to assess PVA.ResultsCompared to spontaneous breathing, the most pronounced decrease in EMG activity was achieved with the high-pressure settings. Adding a high breathing frequency did reduce EMG activity per breath, while the decrease in EMG activity over 1 min was comparable with the high-pressure, low-frequency setting. With high backup breathing frequencies less breaths were pressure supported (25% vs 97%). PVAs occurred more frequently with the low-frequency settings (P=0.017).ConclusionHigh-intensity NIV might provide optimal unloading of respiratory muscles, without undue increases in PVA.

Effect of expiratory positive airway pressure on tidal volume during non-invasive ventilation.

During non-invasive ventilation (NIV), tidal volume ( Vt) will depend upon the difference between inspiratory and expiratory positive airway pressure (IPAP and EPAP, respectively), provided the respiratory muscles are relaxed and the lungs and chest wall therefore move along their passive pressure-volume curves. To test this hypothesis, we studied the effect of increasing EPAP during pressure-controlled modes of NIV in 30 long-term ventilator users (10 each with scoliosis, obesity hypoventilation or neuromuscular disorders). While maintaining the same IPAP, addition of 5 cmH2O of EPAP reduced mean Vt by 167 ml; 10 cmH2O reduced Vt by 367 ml. This pattern was seen in all three patient groups. EPAP has several potential advantages, for example maintaining upper airway patency, preventing basal atelectasis and facilitating triggering. EPAP does, however, appear to reduce Vt. Decreasing EPAP is an alternative to increasing IPAP if measurements of gas exchange during NIV indicate that ventilation is inadequate.

Sessions 1 - 11

Background We are interested in how to optimise care for people with motor neurone disease (MND) who are on non-invasive ventilation (NIV) and whether technology can contribute. We have previously developed a respiratory question set for telemonitoring to complement the monitoring of continuous overnight oximetry and patient ventilator interactions (PVI). Objectives We wished to examine whether proactive management was feasible, determine the work generated for the clinical team and the impact on the maintenance of ventilation. Methods Ten ventilated patients (male=6; mean age=61yrs; median illness duration=14 months; median NIV usage=11 months) were recruited and followed for 6 months. Participants used a telemonitoring device (Careportal®) to complete the respiratory questions; nocturnal pulse oximetry and PVI were also assessed weekly. Although monitored, patients were told to contact their general practitioner (GP) for emergencies. Revised ALS functional rating scale (ALSFRS-R) and Hospital Anxiety and Depression Scale (HADS) were completed three-monthly. Non-parametric tests were used to identify changes in oxygen saturation levels (SpO2), PVI, ALSFRS-R, and HADS over the trial period. Results In total, 118 telemonitoring question alerts led to 40 interventions in 8 patients (equipment provision=16, treatment adjustment=15, direct reviews=8, referral=1), these were needed despite 5 having had recent routine outpatient review. Twenty-four interventions were triggered by the answers to the respiratory questions, 8 were requested by patients through Careportal®, 5 had pressure adjustments to correct suboptimal nocturnal oximetry and 3 were follow-up interventions. Three patients made unscheduled GP contacts and one of them was hospitalised with pneumonia, despite being on antibiotics. Amongst PVI data, minute ventilation (MV) was maintained; baseline mean=6.32 l/min (SD=1.81) and endpoint mean=7.2 l/min (SD=2.64). Inspiratory positive airway pressure (IPAP) [7 patients had alterations] and NIV usage time changed significantly; baseline IPAP cmH2O mean=16.97 (SD=4.2) and end point mean=20.53 (SD=5.46;p=.004); baseline NIV usage mean=8.55hrs (SD=3.32) and endpoint mean=11.45hrs (SD=3.55;p=.006). ALSFRS-R scores deteriorated: baseline mean =22.9 (SD=10.9) and end point mean =18.8 (SD=10.19;p=.008). HADS scores for anxiety did not change from baseline (mean=4.5; SD=3.37) to end point (mean=3.9; SD=3.07) or for depression from baseline (mean=6.3; SD=3.47) to endpoint (mean=8.3; SD=4.85). Discussion and conclusions We found weekly telemonitoring to be feasible. Optimisation of SpO2 levels was enabled and ventilation was maintained. The bespoke questions triggered 60% of the interventions, highlighting the importance of symptom review in addition to physiological or PVI measurements. Maintained HADS suggest no adverse effect of telemonitoring, this and whether it is perceived as useful is being explored through qualitative work. This approach may replace some traditional reviews, linking the patient effectively to the care team. Further study should be conducted to examine its impact on the holistic management of this patient group including health economics and outcomes.

Can fiberoptic bronchoscopy be applied to critically ill patients treated with noninvasive ventilation for acute respiratory distress syndrome? Prospective observational study.

BackgroundNoninvasive ventilation (NIV) is a cornerstone for the treatment of acute respiratory failure of various etiologies. Using NIV is discussed in mild-to-moderate acute respiratory distress syndrome (ARDS) patients (PaO2/FiO2 > 150). These patients often have comorbidities that increase the risk for bronchoscopy related complications. The primary outcome of this prospective observational study was to evaluate the feasibility, safety and contribution in diagnosis and/or modification of the ongoing treatment of fiberoptic bronchoscopy (FOB) in patients with ARDS treated with NIV.MethodsARDS patients treated with NIV and who require FOB as the diagnostic or therapeutic procedure were included the study. Intensive care ventilators or other dedicated NIV ventilators were used. NIV was applied via simple oro-nasal mask or full-face mask. Pressure support or inspiratory positive airway pressure (IPAP), external positive end expiratory pressure (PEEP) or expiratory positive airway pressure (EPAP) levels were titrated to achieve an expiratory tidal volume of 8 to 10 ml/kg according to ideal body weight, SpO2 > 90 % and respiratory rate below 25/min.ResultsTwenty eight subjects (mean age 63.3 ± 15.9 years, 15 men, 13 women, PaO2/FiO2 rate 145 ± 50.1 at admission) were included the study. Overall the procedure was well tolerated with only 5 (17.9 %) patients showing minor complications. There was no impairment in arterial blood gas and cardiopulmonary parameters after FOB. PaO2/FiO2 rate increased from 132.2 ± 49.8 to 172.9 ± 63.2 (p = 0.001). No patient was intubated within 2 h after the bronchoscopy. 10.7, 32.1 and 39.3 % of the patients required invasive mechanical ventilation after 8 h, 24 h and 48 h, respectively. Bronchoscopy provided diagnosis in 27 (96.4 %) patients. Appropriate treatment was decided according to the results of the bronchoscopic sampling in 20 (71.4 %) patients.ConclusionFOB under NIV could be considered as a feasible tool for diagnosis and guide for treatment of patients with ARDS treated via NIV in intensive care units. However, FOB-correlated life-treathening complications in severe hypoxemia should not be forgotten. Furthermore, further controlled studies involving a larger series of homogeneous ARDS patients undergoing FOB under NIV are needed to confirm these preliminary findings.

Failure of noninvasive ventilation in adult patients with acute asthma exacerbation.

Failure of noninvasive ventilation in adult patients with acute asthma exacerbation.

Adaptive Servo-Ventilation for Central Sleep Apnea in Heart Failure.

To the Editor: Cowie et al. (Sept. 17 issue)1 report on the results of the Treatment of SleepDisordered Breathing with Predominant Central Sleep Apnea by Adaptive Servo Ventilation in Patients with Heart Failure (SERVE-HF) trial. They found increases in all-cause and cardiovascular mortality among patients with heart failure who received adaptive servo-ventilation therapy, and the adaptive servo-ventilation group had no improvement in quality-of-life measures. These results contradict those of our Study of the Effects of Adaptive Servo-ventilation Therapy on Cardiac Function and Remodeling in Patients with Chronic Heart Failure (SAVIOR-C).2 The majority of patients who received adaptive servoventilation in our study had improvements in quality of life, and the improvement from New York Heart Association (NYHA) functional class III heart failure to class II heart failure was significant. We found that the adaptive servo-ventilation settings differed between the two studies. Cowie et al. manually increased the expiratory and inspiratory positive airway pressures from the default levels to suppress sleep apnea.1 Because the effects of positive airway pressure on cardiac output depend on the baseline pulmonary-capillary wedge pressure,3 we were concerned that excessive increases in levels of airway pressure might diminish cardiac output and induce reflex sympathetic hyperactivity in some patients with mild pulmonary congestion. For this reason, the levels of airway pressure in patients in the SAVIOR-C were maintained at or below the default levels.2,4 It would be useful to know whether high-pressure adaptive servo-ventilation settings precipitated adverse events in their patients. Yasuki Kihara, M.D., Ph.D.

Operator dependent factors implicated in failure of non‐invasive positive pressure ventilation (NIPPV) for respiratory failure

Non-invasive Positive Pressure Ventilation (NIPPV) is employed for the management of acute respiratory failure and studies have shown that it can prevent the need for endotracheal intubation, mechanical ventilation and associated complications. Given limited studies evaluating the factors, other than those related patient or underlying disease severity, that may lead to NIPPV failure, we performed this study to gain insight into current practices in terms of utilization of NIPPV and operator dependent factors that may possibly contribute to failure of NIPPV. After institutional board review approval a retrospective chart review was performed of consecutive patients who were initiated on and failed NIPPV between January 2009 and December 2009. Data was recorded regarding baseline demographics, admission diagnosis, indications for NIPPV, presence of contraindications, type of NIPPV and initial settings, ABG analysis before and after initiation, whether a titration of the settings was performed or not, operator related factors that may have contributed to failure of NIPPV and clinical outcomes. Among 1095 patients screened, 111 failed NIPPV. The mean age was 60 years with 59% males. The most frequent indication for initiating NIPPV was COPD exacerbation (N = 27) followed by pneumonia (N = 26). CPAP was used in 5(6%) patients. Median inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) setting were 10 and 5 cm of H2 O respectively. Three most common reasons for failure were an inappropriate indication (33%), Progression of underlying disease (30%) and lack of titration (23%). Overall mortality was 22%. Mortality was higher when NIPPV failure was seen among patients with an inappropriate indication or an overlooked contraindication compared to those with an appropriate indication (27% vs 17%). Excluding progression of underlying disease, operator dependent factors linked to NIPPV failure are; inappropriate indication, lack of adequate titration and an overlooked contraindication. Inappropriate utilization of NIPPV in respiratory failure is associated with higher mortality.

Utility of Transcutaneous Capnography for Optimization of Non-Invasive Ventilation Pressures.

Nocturnal Non-invasive Positive Pressure Ventilation (NPPV) is the treatment of choice in patients with chronic hypercapnic respiratory failure due to hypoventilation. Continuous oxygen saturation measured with a pulse oximeter provides a surrogate measure of arterial oxygen saturation but does not completely reflect ventilation. Currently, Partial Pressure of Arterial (PaCO2) measured by arterial blood analysis is used for estimating the adequacy of ventilatory support and serves as the gold standard. To examine the safety, feasibility and utility of cutaneous capnography to re-titrate the non-invasive positive pressure ventilation settings in patients with chronic hypercapnic respiratory failure due to hypoventilation. Twelve patients with chronic hypercapnic respiratory failure prospectively underwent complete polysomnography and cutaneous capnography measurement on the ear lobe. Non-invasive ventilation pressures were adjusted with the aim of normalizing cutaneous carbon dioxide or at least reducing it by 10 to 15 mmHg. Sensor drift for cutaneous carbon dioxide of 0.7 mmHg per hour was integrated in the analysis. Mean baseline cutaneous carbon dioxide was 45.4 ± 6.5 mmHg and drift corrected awake value was 45.1 ± 8.3 mmHg. The correlation of baseline cutaneous carbon dioxide and the corrected awake cutaneous carbon dioxide with arterial blood gas values were 0.91 and 0.85 respectively. Inspiratory positive airway pressures were changed in nine patients (75%) and expiratory positive airway pressures in eight patients (66%). Epworth sleepiness score before and after the study showed no change in five patients, improvement in six patients and deterioration in one patient. Cutaneous capnography is feasible and permits the optimization of non-invasive ventilation pressure settings in patients with chronic hypercapnic respiratory failure due to hypoventilation. Continuous cutaneous capnography might serve as an important additional tool to complement diurnal arterial carbon dioxide tension values.

Expiratory and Inspiratory Positive Airway Pressures in Obstructive Sleep Apnea: How Much Pressure is Necessary? A Different Point of View

The preferred treatment for obstructive sleep apnea (OSA) is continuous positive airway pressure (CPAP) therapy. Although the evidence for CPAP benefits for OSA patients is compelling, acceptance and adherence remain a challenge for patients and healthcare providers [1,2]. CPAP therapy is generally thought to be safe and rarely associated with complications. Breathing difficulty against a high pressure is a major complaint for some patients [2,3]. For patients who cannot tolerate CPAP, Bi level positive airway pressure (BiPAP) was thought to provide an alternative to help reduce the pressure during exhalation and perhaps improve patient comfort and compliance [4]. However, there is conflicting evidence about the benefits of BiPAP over CPAP in OSA therapy [1]. The increase in intrathoracic pressure during CPAP or BiPAP has the potential to produce unwanted physiological effects such as decrease in venous return, left ventricle dysfunction, increase in pulmonary vascular resistance, or decrease in lung compliance and therefore the least amount of pressure should always be used for OSA therapy. Our goal is to discuss potential changes in pharyngeal and intrathoracic pressure and in lung volume during CPAP and BiPAP treatments and how such changes may impact upper airway collapse. We will also explore the potential role of expiratory resistance devices in the treatment of OSA.

Effect of oxygen tubing connection site, changes of the inspiratory positive airway pressure and tidal volume on inspired oxygen concentration during noninvasive positive pressure ventilation

We evaluated the effects of administering oxygen through nasal catheter inside the mask or through the mask on inspired oxygen concentration in order to find better ways of administering oxygen to improve the inspired oxygen concentration in non-invasive positive pressure ventilation (NPPV). A human face model was used to simulate the human face, and the model of the double lumen endotracheal tube was used to simulate the bilateral nasal cavity and trachea, and then a model was constructed to allow simulated NPPV. The changes of FIO₂were measured in different pressure (constant tidal volume) and different tidal volume (constant pressure) conditions under the way of administering oxygen through nasal catheter inside the mask or through the mask. The effects on FIO₂were measured in different pressure (constant tidal volume) and different tidal volume (constant pressure) conditions under same way of administering oxygen. The FIO₂was (35.4 ± 1.7)% when oxygen was administered through the mask, but a higher FIO₂was achieved with the oxygen injected into the mask [(52.4 ± 2.1)%, and oxygen flow of 5 L/min, P<0.05]. The oxygen concentration declined with the increase of inspiratory positive airway pressure (IPAP) on the condition of administering oxygen through the mask on constant tidal volume. The FIO₂at IPAP 16 cmH₂O (1 cmH₂O=0.098 kPa) was higher than that at IPAP 8 cmH₂O, and the FIO₂at IPAP 20 cmH₂O was higher than those at IPAP 8 cmH₂O and 12 cmH₂O, P<0.05. The oxygen concentration increased with the tidal volume increase on the condition of administering oxygen through the mask on constant IPAP. The changes of tidal volume and IPAP had no effects on FIO₂on the condition of administering oxygen through nasal catheter inside the mask. Administering oxygen through nasal catheter inside the mask during NPPV can increase FIO₂and conserve oxygen. This study provides theoretical basis for the development of newer masks.

Influence of effective noninvasive positive pressure ventilation on inflammatory and cardiovascular biomarkers in stable hypercapnic COPD patients

BackgroundNoninvasive positive pressure ventilation (NPPV) using effective pressure levels to reduce chronic hypercapnia improves survival in stable hypercapnic COPD. However, the underlying mechanisms remain unclear. This study investigated the influence of effective NPPV on a panel of cytokines and established cardiovascular biomarkers. MethodsPeripheral blood samples were drawn before and three months after the initiation of NPPV and analyzed by flow cytometric bead array and ELISA. ResultsTwenty COPD patients (forced expiratory volume in 1 s 31 ± 17% predicted) were included. NPPV (inspiratory positive airway pressure 23 ± 4 mbar; breathing frequency 17 ± 2/min) significantly improved arterial carbon dioxide pressure (PaCO2), both during daytime spontaneous breathing (p = 0.005) and nighttime ventilation (p < 0.001). Serum interleukin (IL)-10 levels were slightly reduced (p = 0.016), whereas IL-1 (p = 0.073) and IL-12 (p = 0.089) showed only a tendency towards change over time. Pro-brain natriuretic peptide (proBNP) significantly decreased by a mean of 578 ± 1332 ng/L after three months' NPPV (p = 0.017 vs baseline). No other significant changes in cardiovascular biomarkers occurred. The decrease in PaCO2 during daytime spontaneous breathing was positively correlated with the reduction in proBNP (correlation coefficient 0.613; p = 0.0197). ConclusionEffective NPPV impacts on systemic inflammation in COPD patients. Furthermore, reductions in PaCO2 during NPPV were associated with decreases in proBNP levels. Future studies are needed to clarify these findings in a larger cohort of COPD patients. Clinical trial registrationDRKS00007644 (German Clinical Trials Register; https://drks-neu.uniklinik-freiburg.de/drks_web/navigate.do?navigationId=resultsExt).

Pre-hospital non-invasive ventilation for acute respiratory failure: a systematic review and cost-effectiveness evaluation.

Non-invasive ventilation (NIV), in the form of continuous positive airway pressure (CPAP) or bilevel inspiratory positive airway pressure (BiPAP), is used in hospital to treat patients with acute respiratory failure. Pre-hospital NIV may be more effective than in-hospital NIV but requires additional ambulance service resources. We aimed to determine the clinical effectiveness and cost-effectiveness of pre-hospital NIV compared with usual care for adults presenting to the emergency services with acute respiratory failure and to identify priorities for future research. Fourteen electronic databases and research registers (including MEDLINE In-Process & Other Non-Indexed Citations, MEDLINE, EMBASE, and Cumulative Index to Nursing and Allied Health Literature) were searched from inception to August 2013, supplemented by hand-searching reference lists and contacting experts in the field. We included all randomised or quasi-randomised controlled trials of pre-hospital NIV in patients with acute respiratory failure. Methodological quality was assessed according to established criteria. An aggregate data network meta-analysis (NMA) of mortality and intubation was used to jointly estimate intervention effects relative to usual care. A NMA, using individual patient-level data (IPD) and aggregate data where IPD were not available, was carried out to assess whether or not covariates were treatment effect modifiers. A de novo economic model was developed to explore the costs and health outcomes when pre-hospital NIV (specifically CPAP provided by paramedics) and standard care (in-hospital NIV) were applied to a hypothetical cohort of patients with acute respiratory failure. The literature searches identified 2284 citations. Of the 10 studies that met the inclusion criteria, eight were randomised controlled trials and two were quasi-randomised trials (six CPAP; four BiPAP; sample sizes 23-207 participants). IPD were available from seven trials (650 patients). The aggregate data NMA suggested that CPAP was the most effective treatment in terms of mortality (probability = 0.989) and intubation rate (probability = 0.639), and reduced both mortality [odds ratio (OR) 0.41, 95% credible interval (CrI) 0.20 to 0.77] and intubation rate (OR 0.32, 95% CrI 0.17 to 0.62) compared with standard care. The effect of BiPAP on mortality (OR 1.94, 95% CrI 0.65 to 6.14) and intubation rate (OR 0.40, 95% CrI 0.14 to 1.16) compared with standard care was uncertain. The combined IPD and aggregate data NMA suggested that sex was a statistically significant treatment effect modifier for mortality. The economic analysis showed that pre-hospital CPAP was more effective and more expensive than standard care, with an incremental cost-effectiveness ratio of £20,514 per quality-adjusted life-year (QALY) and a 49.5% probability of being cost-effective at the £20,000-per-QALY threshold. Variation in the incidence of eligible patients had a marked impact on cost-effectiveness and the expected value of sample information for a future randomised trial. The meta-analysis lacked power to detect potentially important differences in outcome (particularly for BiPAP), the intervention was not always compared with the best alternative care (in-hospital NIV) in the primary studies and findings may not be generalisable. Pre-hospital CPAP can reduce mortality and intubation rates, but cost-effectiveness is uncertain and the value of further randomised evaluation depends on the incidence of suitable patients. A feasibility study is required to determine if a large pragmatic trial of clinical effectiveness and cost-effectiveness is appropriate. The study is registered as PROSPERO CRD42012002933. The National Institute for Health Research Health Technology Assessment programme.

Exhaled Air Dispersion During Noninvasive Ventilation via Helmets and a Total Facemask

BACKGROUNDNoninvasive ventilation (NIV) via helmet or total facemask is an option for managing patients with respiratory infections in respiratory failure. However, the risk of nosocomial infection is unknown.METHODSWe examined exhaled air dispersion during NIV using a human patient simulator reclined at 45° in a negative pressure room with 12 air changes/h by two different helmets via a ventilator and a total facemask via a bilevel positive airway pressure device. Exhaled air was marked by intrapulmonary smoke particles, illuminated by laser light sheet, and captured by a video camera for data analysis. Significant exposure was defined as where there was ≥ 20% of normalized smoke concentration.RESULTSDuring NIV via a helmet with the simulator programmed in mild lung injury, exhaled air leaked through the neck-helmet interface with a radial distance of 150 to 230 mm when inspiratory positive airway pressure was increased from 12 to 20 cm H2O, respectively, while keeping the expiratory pressure at 10 cm H2O. During NIV via a helmet with air cushion around the neck, there was negligible air leakage. During NIV via a total facemask for mild lung injury, air leaked through the exhalation port to 618 and 812 mm when inspiratory pressure was increased from 10 to 18 cm H2O, respectively, with the expiratory pressure at 5 cm H2O.CONCLUSIONSA helmet with a good seal around the neck is needed to prevent nosocomial infection during NIV for patients with respiratory infections.

Working characteristics of a new ventilator with automatic secretion clearance function

Secretions in the airways of ventilated patients must be cleared efficiently and timely. A novel ventilator (SC ventilator) is proposed with an automatic secretion clearance function in order to provide a new approach. A mathematical model of a ventilation system with the SC ventilator is set up to optimize the SC ventilator. Based on the research, conclusion can be reached as follows. First, the experimental results and the mathematical model are proved to be authentic and reliable. Second, the secretion clearance efficiency of the SC ventilator may be higher than that of IL-IE device. Finally, increasing the inspiratory positive airway pressure or decreasing the expiatory positive airway pressure of the SC ventilator can improve the efficiency of the secretion clearance. This paper lays a foundation for the secretion clearance improvement of the SC ventilator.

Noninvasive positive pressure ventilation after extubation: features and outcomes in clinical practice.

ObjectiveTo describe postextubation noninvasive positive pressure ventilation use in intensive care unit clinical practice and to identify factors associated with noninvasive positive pressure ventilation failure.MethodsThis prospective cohort study included patients aged ≥ 18 years consecutively admitted to the intensive care unit who required noninvasive positive pressure ventilation within 48 hours of extubation. The primary outcome was noninvasive positive pressure ventilation failure.ResultsWe included 174 patients in the study. The overall noninvasive positive pressure ventilation use rate was 15%. Among the patients who used noninvasive positive pressure ventilation, 44% used it after extubation. The failure rate of noninvasive positive pressure ventilation was 34%. The overall mean ± SD age was 56 ± 18 years, and 55% of participants were male. Demographics; baseline pH, PaCO2 and HCO3; and type of equipment used were similar between groups. All of the noninvasive positive pressure ventilation final parameters were higher in the noninvasive positive pressure ventilation failure group [inspiratory positive airway pressure: 15.0 versus 13.7cmH2O (p = 0.015), expiratory positive airway pressure: 10.0 versus 8.9cmH2O (p = 0.027), and FiO2: 41 versus 33% (p = 0.014)]. The mean intensive care unit length of stay was longer (24 versus 13 days), p < 0.001, and the intensive care unit mortality rate was higher (55 versus 10%), p < 0.001 in the noninvasive positive pressure ventilation failure group. After fitting, the logistic regression model allowed us to state that patients with inspiratory positive airway pressure ≥ 13.5cmH2O on the last day of noninvasive positive pressure ventilation support are three times more likely to experience noninvasive positive pressure ventilation failure compared with individuals with inspiratory positive airway pressure < 13.5 (OR = 3.02, 95%CI = 1.01 - 10.52, p value = 0.040).ConclusionThe noninvasive positive pressure ventilation failure group had a longer intensive care unit length of stay and a higher mortality rate. Logistic regression analysis identified that patients with inspiratory positive airway pressure ≥ 13.5cmH2O on the last day of noninvasive positive pressure ventilation support are three times more likely to experience noninvasive positive pressure ventilation failure.

Iterative Learning Control: An Example for Mechanical Ventilated Patients

Positive pressure ventilation is a method of artificial ventilation. If patients can not breath normally due to respiratory insufficiency, they are connected to a mechanical ventilator. The ventilator generates a positive end-expiration pressure (PEEP) during the expiration phase and an inspiratory positive airway pressure (IPAP) during the inspiration phase. These different pressure levels lead to inflation and deflation of the lung and the patient is ventilated. To achieve the desired pressure levels a closed-loop pressure control has to be designed and developed. Linear PI(D)-controller for example can not follow predefined reference trajectories exactly, because of different and varying patient states and lung parameters. An adaption from patient to patient or from breathing cycle to breathing cycle is usually not possible. Due to further development in microcontroller technology, more complex control algorithms can be used. For cyclically recurring processes iterative learning control (ILC) algorithms provide the possibility to react on variable environment conditions. In ventilation the ILC algorithm can learn the required signal from breathing cycle to breathing cycle to track the reference trajectory.

Uncommon complication of bilevel positive airway pressure.

Sir, A 60-year-old lady was admitted in the intensive care unit with shortness of breath. She was having coarse bilateral crepitations with saturation of 85% on pulse oximetry. She was diagnosed as a case of dilated cardiomyopathy with severe left ventricular dysfunction. Adrenaline infusion was started to optimize blood pressure. Frusemide was given as decongestive therapy. Bilevel positive airway pressure (BiPAP) with orofacial interface was applied with setting of inspiratory positive airway pressure 14 and expiratory positive airway pressure 7. After 1 h of therapy, saturation started improving; however patient started complaining of right ear pain. Otoscopic examination revealed bulging right tympanic membrane. High positive airway pressure by BiPAP might have caused raised middle ear pressure leading to pain. BiPAP was applied after inserting well lubricated nasal airway size 7 mm in right nasal passage. Patient's ear pain gradually subsided and patient was much comfortable. Noninvasive positive pressure ventilation is commonly used in the treatment of patients with acute respiratory failure.[1] Noninvasive ventilation can avoid morbidity associated with invasive ventilation.[2] The inspiratory positive airway pressure in BiPAP decrease the work of breathing and the expiratory positive airway pressure increase the functional residual capacity of the lung by recruiting collapsed alveoli. Common complication of BiPAP such as mask related minor injury to the skin of the face (laceration, ulcer) occurs in approximately 13% of patients.[3] Other complications include irritation to the eyes from the mask ventilation, irritation to the nasal mucosa, or drying of the upper airway passages, gastric distention (incidence rate, 2%).[4] Positive airway pressure delivered by BiPAP can cause rise in middle ear pressure through eustachian tube as in the present case. It can predispose patient to otitis media and trauma to middle ear structures. In the present case, such complications were avoided by using nasal airway which protected the eustachian tube from transmitting the airway pressure. We do not propose to insert nasal airway in every patient on BiPAP but can be considered in patients complaining of ear pain and history of repeated ear infections. One could also reduce the airway pressure setting to reduce the pressure in the middle ear.

Comparison of HFNC, bubble CPAP and SiPAP on aerosol delivery in neonates: An in-vitro study.

Aerosol drug delivery via high flow nasal cannula (HFNC), bubble continuous positive airway pressure (CPAP), and synchronized inspiratory positive airway pressure (SiPAP) has not been quantified in spontaneously breathing premature infants. The purpose of this study was to compare aerosol delivery via HFNC, bubble CPAP, and SiPAP in a model of a simulated spontaneously breathing preterm infant. The types of CPAP systems and nebulizer positions used during aerosol therapy will impact aerosol deposition in simulated spontaneously breathing infants. Quantitative, comparative, in-vitro study. A breath simulator was set to preterm infant settings (VT : 9 ml, RR: 50 bpm and Ti: 0.5 sec) and connected to the trachea of an anatomical upper airway model of a preterm infant via collecting filter distal to the trachea. The HFNC (Optiflow; Fisher & Paykel), Bubble CPAP (Fisher & Paykel), and SiPAP (Carefusion) were attached to the nares of the model via each device's proprietary nasal cannula and set to deliver a baseline of 5 cm H2 O pressure. Albuterol sulfate (2.5 mg/0.5 ml) was aerosolized with a mesh nebulizer (Aeroneb Solo) positioned(1) proximal to the patient and(2) prior to the humidifier (n = 5). The drug was eluted from the filter with 0.1 N HCl and analyzed via spectrophotometry (276 nm). Data were analyzed using descriptive statistics, t-tests, and one-way analysis of variance (ANOVA), with P < 0.05 significant. At position 1, the trend of lower deposition (mean ± SD%) across devices was not significant (0.90 ± 0.26, 0.70 ± 0.16 and 0.59 ± 0.19, respectively; P = 0.098); however, in position 2, drug delivery with SiPAP (0.79 ± 0.11) was lower compared to both HFNC (1.30 ± 0.17; P = 0.003) and bubble CPAP (1.24 ± 0.24; p = 0.008). Placement of the nebulizer prior to the humidifier increased deposition with all devices (P < 0.05). Aerosol can be delivered via all three devices used in this study. Device selection and nebulizer position impacted aerosol delivery in this simulated model of a spontaneously breathing preterm infant.

Is non-invasive ventilation safe in acute severe asthma?

The effect of non-invasive ventilation (NIV) in acute severe asthma is unclear and there are concerns regarding its safety. We undertook a 5-year case-control review of mortality and morbidity associated with NIV use in acute severe asthma and compared this with asthma requiring invasive mechanical ventilation (IMV) and a control group with less severe asthma without ventilatory support. Eight hundred seventy-three patients had acute severe asthma of whom 30 were treated with NIV, 17 with IMV and 90 served as controls. The mean duration of NIV was 9.5 ± 7.3 h with inspiratory positive airway pressure and expiratory positive airway pressure of 11.9 ± 1.4 and 5.8 ± 1.2 cmH2 O respectively. Mortality was zero in the NIV and control groups, compared with 41% in the IMV group. None of the NIV or control groups required escalation to invasive ventilation. There were no instances of haemodynamic compromise in the NIV or control groups. Length of hospital stay was 121 ± 96 h in the NIV group and similar to the severe IMV group (136 ± 99 h, P > 0.05) and significantly longer than the control group (42 ± 40 h, P < 0.05). NIV can be safely used in acute severe asthma although further work is needed to delineate the precise patient selection process.

Efficacy of auto-trilevel positive airway ventilation in hypercapnic patients with overlap syndrome

To observe the efficacy of auto-trilevel positive airway pressure (Auto-trilevel PAP) ventilation in overlap syndrome (OS) patients with hypercapnia. From October 2012 to May 2014, 21 OS patients with a PaCO2> 45 mmHg (1 mmHg = 0.133 kPa) and coexisting stable chronic obstructive pulmonary diseases (COPD) and moderate-to-severe OSAS were recruited. Three different positive airway pressure (PAP) modes of ventilators (SOMNOvent auto-S, Weinmann Inc, Germany) were employed for 8 hours per night with each mode at each night and two nights' interval without any treatment among different modes. Under mode one, the expiratory positive airway pressure (EPAP) issued by bilevel positive airway pressure (BiPAP) was titrated as the minimal positive pressure for a disappearance of snoring. The same inspiratory positive airway pressure (IPAP) titrated by end tidal CO2 levels under mode 1 was used under modes 2 and 3 as well. However, the EPAP issued by BiPAP under mode 2 was 3 cmH2O (1 cmH2O = 0.098 kPa) higher than that under mode 1. Under mode 3 with autotrilevel PAP, the beginning of EPAP was set the same as that under mode 1 while the end of EPAP (EEPAP) was automatically adjusted based on upper airway patency condition. Comparisons were made for parameters before and after treatment as well as among different ventilation modes. The following parameters were compared such as nocturnal apnea hypopnea index (AHI), minimal SpO2 (miniSpO2), arousal index, sleep efficiency, morning PaCO2 and Epworth sleepiness score (ESS). Compared with the parameters pre-therapy, modes 1-3 showed a significant decrease in nocturnal AHI (6.3 ± 1.3), (3.1 ± 1.0), (3.6 ± 0.6) vs (38.6 ± 11.3) events/h), arousal index ((7.0 ± 1.1), (5.1 ± 0.9), (4.2 ± 1.7) vs (27.5 ± 5.4) events/h), morning PaCO2 (42.4 ± 3.8), (47.9 ± 2.6) and (43.2 ± 3.3) vs (57.3 ± 4.3) mmHg and daytime ESS (7.2 ± 1.3, 7.4 ± 1.3 and 5.3 ± 1.5 vs 11.4 ± 2.7), but a significant increase in nocturnal miniSpO2 (82.3 ± 5.4), (89.6 ± 3.9) and (90.3 ± 3.2) vs (62.4 ± 11.3) mmHg and sleep efficiency caused (71.3 ± 5.2)%, (79.4 ± 4.3)% and (83.2 ± 4.4)% vs (59.8 ± 6.3)% (all P < 0.01). Comparison of 3 modes demonstrated that, with the same IPAP, mode 3 resulted in the lowest arousal index, daytime ESS and the highest sleep efficiency. Comparison of modes 1 and 2 revealed a statistically lower AHI but higher miniSpO2 and morning PaCO2 under mode 2 (all P < 0.01). Compared with mode 1, mode 3 showed a lower AHI, higher miniSpO2 (all P < 0.01), but there was no significant difference in PaCO2 at the end of therapy. Compared with mode 2, mode 3 showed a significant lower PaCO2 (P < 0.01), but there was no significant difference in AHI and miniSpO2. Auto-trilevel PAP ventilation is superior to fixed BiPAP ventilation in the treatment of hypercapnic OS since this novel PAP mode can achieve a higher efficacy in simultaneous removal of residual apnea hypopnea events and correction of hypercapnia and yield a higher sleep quality and lower daytime sleepiness.