Claudio Rabec

Proposal for a systematic analysis of polygraphy or polysomnography for identifying and scoring abnormal events occurring during non-invasive ventilation

Non-invasive ventilation (NIV) is recognised as an effective treatment for chronic hypercapnic respiratory failure. Monitoring NIV during sleep may be preferable to daytime assessment. This paper reports the findings of an international consensus group which systematically analysed nocturnal polygraphic or polysomnographic tracings recorded with either volume-cycled or pressure-cycled ventilators. A systematic description of nocturnal respiratory events which occur during NIV is proposed: leaks, obstruction at different levels of the upper airway (glottis and/or pharynx), with or without decrease of respiratory drive and asynchrony.

Evaluating noninvasive ventilation using a monitoring system coupled to a ventilator: a bench-to-bedside study

Empirically determined noninvasive ventilation (NIV) settings may not achieve optimal ventilatory support. Some ventilators include monitoring modules to assess ventilatory quality. We conducted a bench-to-bedside study to assess the ventilatory quality of the VPAPTMIII-ResLinkTM (ResMed, North Ryde, Australia). We tested the accuracy of minute ventilation (MV) and leak calculations given by VPAPTMIII-ResLinkTM compared to those measured by a bench model at varied leak levels and ventilator settings. We systematically assessed NIV efficacy using this system from 2003 to 2006. Ventilation was considered inadequate if leak (>24 L·min−1), continuous desaturation (>30% of the trace) or desaturation dips (>3%) were present. On the bench test, both methods were highly correlated (r = 0.947, p>0.0001 and r = 0.959, p<0.0001 for leak and MV, respectively). We performed 222 assessments in 169 patients (aged 66.42±16 yrs, 100 males). Abnormalities were detected on 147 (66%) out of 222 occasions. Leak was the most common abnormality (34.2%) followed by desaturation dips (23.8%). The most effective therapeutic solutions were a chin strap if leak was detected (61.2%) and expiratory positive airway pressure increase for desaturation dips (59.5%). In 15.7% of cases, when abnormalities persisted, a polygraphy was performed. The systematic use of this device enables NIV to be optimised, limiting the indication of sleep studies to complex cases.

Effectiveness of Adaptive Servo Ventilation in the treatment of hypocapnic central sleep apnea of various etiologies

BACKGROUND Central sleep apnea (CSA) occurs in clinical situations that induce hypocapnia and respiratory instability during sleep. This is true, not only in heart failure patients, but also in patients suffering from neurological diseases and idiopathic CSA. Adaptive Servo Ventilation (ASV) is frequently prescribed in France for the treatment of CSA, but only a few studies have evaluated ASV treatment with regards to long term effectiveness and compliance. METHODS Retrospective chart review in two French centers of the outcome of 74 CSA patients treated by ASV with a mean follow up on ASV of 36±18 months. RESULTS Thirty-three of the 74 patients suffered from CSA related to heart failure (HF), whereas the 41 others exhibited CSA mainly associated with neurological disorders or idiopathic CSA. Mean ASV compliance was 5.2±2.6 and 5.9±2.9h per night in cardiac failure and non-cardiac failure patients, respectively. All patients significantly improved their apnea+hypopnea index (from 47.4±19.8 to 6.9±9.3/h [p<0.001]) and mean nocturnal SaO(2) (from 92.1±2.6% to 93.6±3.2% [p<0.001]). The Epworth sleepiness scale score was reduced from 10.2±5.2 to 6.5±3.9 (p<0.01) in compliant patients but not in non-compliant patients (less than 3h per night). Moreover, compliant cardiac failure patients demonstrated a significant improvement in their NYHA score [p<0.05]. Lastly, ASV significantly reduced chronic hyperventilation as assessed by blood gases. CONCLUSION Our findings suggest that ASV is well tolerated and effective for most patients with hypocapnic central sleep apnea and chronic hyperventilation.

Usefulness of transcutaneous PCO2 to assess nocturnal hypoventilation in restrictive lung disorders.

Nocturnal hypoventilation is now an accepted indication for the initiation of non‐invasive ventilation. Nocturnal hypoventilation may be an under diagnosed condition in chronic respiratory failure. The most appropriate strategy to identify sleep hypoventilation is not yet clearly defined. In clinical practice, it is indirectly assessed using nocturnal pulse oximetry (NPO) and morning arterial blood gases (mABG). Even though continuous transcutaneous carbon dioxide partial pressure (TcPCO2) monitoring is theoretically superior to NPO plus mABG, it is not routinely used. We aimed to prospectively compare NPO plus mABG with nocturnal TcPCO2 for the detection of alveolar hypoventilation in a cohort of patients with chronic restrictive respiratory dysfunction.

New modes in non-invasive ventilation.

Non-invasive ventilation is useful to treat some forms of respiratory failure. Hence, the number of patients receiving this treatment is steadily increasing. Considerable conceptual and technical progress has been made in the last years by manufacturers concerning this technique. This includes new features committed to improve its effectiveness as well as patient-ventilator interactions. The goal of this review is to deal with latest advances in ventilatory modes and features available for non-invasive ventilation. We present a comprehensive analysis of new modes of ventilator assistance committed to treat respiratory failure (hybrid modes) and central and complex sleep apnea (adaptive servo ventilation), and of new modes of triggering and cycling (neurally adjusted ventilatory assist). Technical aspects, modes of operation and settings of these new features as well as an exhaustive review of published data, their benefits and limits, and the potential place of these devices in clinical practice, are discussed.

Monitoring Noninvasive Ventilation in Patients with Obesity Hypoventilation Syndrome: Comparison between Ventilator Built-in Software and Respiratory Polygraphy

Background: Polygraphy (PG) remains the standard method of assessing noninvasive ventilation (NIV) effectiveness. Built-in software (BIS) of recent NIV equipment provides estimates of some ventilator parameters, but their usefulness is unclear. Objectives: To assess the reliability of BIS compared with PG in a cohort of obesity hypoventilation syndrome (OHS) patients on NIV. Methods: Thirty stable OHS patients on NIV were evaluated in an outpatient setting with simultaneous PG and BIS recordings. The automated apnea-hypopnea event index (EIAUT) provided by Rescan and manual scoring based on available traces obtained from the software (EIBIS) were compared with manual PG scoring (EIPG). Each manual scoring was separately performed by 2 trained operators. Agreement between the 2 operators was assessed using the kappa coefficient. Pearson correlation and Bland-Altman plots were used to evaluate agreement between EIAUT, EIBIS, and EIPG. Results: Twenty-six cases were valid for analysis (age ±61 years, 17 men). All patients were ventilated in the spontaneous/timed mode (mean inspiratory positive airway pressure 17 ± 3 cm H2O, mean expiratory positive airway pressure 10 ± 3 cm H2O). Cohens kappa agreement between the operators was 0.7 for EIBIS and 0.84 for EIPG. EIBIS showed good correlation with EIPG (r2 = 0.79 p < 0.001), better than scoring provided by the automated analysis (r2 = 0.71, p < 0.006 for EIAUT vs. EIPG). Conclusions: In stable OHS patients on NIV, unattended home-based monitoring using Rescan is reproducible and reliable to assess quality of ventilation when compared with PG. In addition, manual scoring of events using data obtained with this device is more consistent than software-based automated analysis.

Ventilatory modes. What's in a name?

We have read with great interest the paper published by Chatburn et al in Respiratory Care.[1][1] reporting on how familiar healthcare leaders coming from different professions are with some general technical and physiological aspects related to mechanical ventilation. Even if the survey shows a

Mise en route d’une ventilation non invasive au domicile : propositions du groupe de travail Casavni

INTRODUCTION In France, there are no good practice guidelines or a regulatory framework for the initiation of long term non-invasive ventilation (NIV). METHODS The ANTADIR federation set up a working party to examine the feasibility of new methods of initiation of NIV and to consider the possibility of initiation in the home. Two problems were considered: (1) logistical and technical requirements, (2) the responsibilities of the professions involved and the regulatory framework. RESULTS Clinical effectiveness, improvement in quality of life and adherence to treatment are similar whether NIV is initiated in hospital or at home. Domiciliary management is possible only when the patient is clinically stable. It should be undertaken by a competent physician or, on medical prescription, by a physiotherapist. A nurse or trained technician may check the apparatus but should not initiate NIV alone. Installation of domiciliary NIV should be considered under the following conditions: patients with spontaneous ventilation, availability of urgent assistance and appropriate family support. Close surveillance of the quality of ventilation is necessary, whether in hospital or at home. For the initiation of domiciliary NIV each professional involved needs a clear understanding of his/her role. CONCLUSION Academic societies should propose good practice guidelines for the initiation of NIV. Domiciliary initiation is possible under certain conditions and the results are as good as those obtained in hospital.

Ventilation non invasive : efficacité d’un nouveau mode ventilatoire chez les patients atteints du syndrome obésité-hypoventilation

Noninvasive ventilation is recommended to correct the nocturnal hypoventilation and relieve the symptoms of patients with the obesity-hypoventilation syndrome (OHS). The benefits of fixed pressure ventilation (S/T technology) are recognized but limited on account of the variability of nocturnal ventilatory requirements. The new technique AVAPS-AE (automatic EPAP) allows adjustment of the pressure according to the volume currently targeted. Its efficacy has not yet been evaluated. Our objectives are to evaluate firstly, whether AVAPS-AE optimizes the benefits of S/T technology on sleep architecture and quality, secondly, whether these benefits are associated with an improvement in gas exchange, symptoms, exercise tolerance, level of physical activity and quality of life of patients with OHS. In this multicenter trial, 60 newly diagnosed patients with OHS will be randomized to the control (S/T) and trial (AVAPS-AE) groups. A standardized titration procedure will be followed for the calibration of the ventilators. Functional evaluations (polysomnography, blood gases, impedance measurements and walking tests), questionnaires (physical activity, quality of life, quality of sleep and daytime somnolence) visual scales (fatigue, headaches) and a recording of activity will be undertaken after two months of ventilation.

Noninvasive ventilation inefficacy due to technically incompatible ventilator settings.

Dear Editor, A taskforce on noninvasive ventilation (NIV) monitoring (SomnoNIV group) recently published a review series suggesting a systematic approach for identifying and scoring abnormal events occurring during sleep studies performed under NIV [1–3]. During the data collection phase, an unusual cause of ventilator malfunction was found for three different patients, and surprisingly, the same event was recently described under NIV in amyotrophic lateral sclerosis (ALS) patients [4]. Atkeson et al. [4] described for the first time this unexpected cause of ventilation failure where ‘‘setting a backup respiratory rate with the NIV system, as is usually done, does not reliably result in effective pressure support to patients with ALS during central breathing pauses.’’ We report herein the description of three events in different patients and propose a likely explanation. Three patients ventilated for chronic hypoventilation were monitored by polygraphy. Diagnoses were diaphragmatic dysfunction due to ALS, diaphragmatic dysfunction due to spinal cord injury, and restrictive respiratory insufficiency due to tuberculosis sequelae. All three patients were ventilated noninvasively with devices from the same manufacturer (Resmed, Sydney, Australia) in spontaneous/timed mode (assisted pressure support mode but with a controlled backup respiratory rate), and single-branch tubing. Ventilation settings are summarized in Table 1. In all three patients, we observed upper airway obstruction with reduction of ventilatory drive [1] but with premature cycling resulting in ineffective pressure support (Fig. 1a). This was unexpected, because, as the patients were ventilated in barometric mode, the device was presumed to guarantee the preset inspiratory pressure. The explanation most probably resides in the settings chosen for the minimal inspiratory time (Timin). To ensure a ‘‘physiological inspiratory window,’’ the manufacturer of these ventilators allows the clinician to define a minimal (Timin) and maximal inspiratory time (Timax) instead of a fixed Ti. Unfortunately, here, the standard default setting for Timin is 0.1 s: if this setting is not corrected for each patient (patients 1 and 2) and if the rise time of inspiratory pressure is more than 0.1 s, or if Timin is shorter than the rise time (patient 3), the ventilator will be allowed to cycle without reaching the preset inspiratory pressure level. This situation arises in case of recurrent increases in inspiratory resistance. We confirmed this hypothesis by reproducing and correcting this event (Fig. 1b). Interestingly, the same ventilator was used in the study of Atkeson et al. [4]. In conclusion, patients can receive insufficient pressure support due to simple technical mistakes, as shown by these three cases. Technical knowledge of respirators and circuits is necessary to understand and analyze polygraphy tracings under NIV [3]. In this specific scenario, this problem could be avoided if software of commercialized home ventilators were configured to refuse a Ti shorter than the rise time.