The relationship between metformin therapy and sleep quantity and quality in patients with Type 2 diabetes referred for potential sleep disorders.

AIMS: Given that sleep disorders are known to be related to insulin resistance, and metformin has favourable effects on insulin resistance and on ventilatory drive, we sought to determine whether metformin therapy was related to sleep variables in a group of patients with Type 2 diabetes. METHODS: We performed a retrospective, observational study of our centre's database for patients referred for potential sleep disorders and then compared metformin-treated patients with those not treated with the drug. All study patients had undergone the same standard polysomnographic procedure. A multivariate analysis was performed to establish whether or not there was an independent relationship between metformin use and sleep variables (after adjusting for age, gender, BMI, neck circumference, cumulated risk factors and insulin use). RESULTS: We studied 387 patients (mean ± sd age: 58.4 ± 10.8 years), of whom 314 had been treated with metformin. Total sleep time and sleep efficiency were higher in metformin-treated patients than in patients not treated with metformin [total sleep time: 6 h 39 min vs. 6 h 3 min, respectively (P = 0.002); sleep efficiency: 77.9 ± 12.3 vs. 71.5 ± 17.2%, respectively (P = 0.003)]. These differences persisted after adjustment for covariates and were observed even although metformin users had a higher BMI than did non-users (median 37.5 vs. 34.8 kg/m(2) ; P = 0.045). CONCLUSION: We showed that metformin therapy is associated with a longer sleep duration and better sleep efficiency. Randomized clinical trials are needed to confirm metformin's favourable effect on sleep quality and quantity.

[The role of endoscopy in exploration of the mediastinum, indications and results]. / Place de l'endoscopie dans l'exploration du médiastin, indications et résultats.

Since 2005, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has emerged as a standard pulmonological tool. The procedure is safe and well tolerated by patients, with minimal morbidity and almost no mortality. A previous review on the technique was published in 2012. However, over the last ten years, a number of new studies have been published on "benign" (sarcoidosis, tuberculosis…) as well as "malignant" diseases (lung cancer, metastases of extra-thoracic cancers, search for mutations and specific oncogenic markers…). These developments have led to expanded indications for EBUS-TBNA, with which it is indispensable to be familiar, in terms of "staging" as well as "diagnosis". In view of optimizing lymph node sampling, several publications have described and discussed EBUS exploration by means of newly available tools (biopsy forceps, larger needles…), and proposed interpretation of the images thereby produced. Given the ongoing evolution of linear EBUS, it seemed indispensable that information on this marvelous tool be updated. This review is aimed at summarizing the novel elements we have found the most important.

Correlation between the Epworth Sleepiness Scale and the Maintenance of Wakefulness Test in Obstructive Sleep Apnea Patients Treated with Positive Airway Pressure.

BACKGROUND: The Epworth sleepiness scale (ESS) is often used to evaluate the impact of treatment in patients with obstructive sleep apnea hypopnea syndrome (OSA). We aimed to evaluate the correlation between ESS and the Maintenance of Wakefulness Test (MWT) in a population of OSA patients treated with positive airway pressure (PAP). METHODS: We retrospectively included all patients during a 2-year period who were diagnosed with OSA in our sleep clinic and required PAP therapy. ESS was evaluated at baseline and after PAP therapy for all patients, and all had a concomitant MWT. Correlation between final ESS, change in ESS, and MWT were evaluated using Spearman's correlation. Given that MWT is considered as the gold standard, the diagnostic performance of ESS was evaluated against MWT. RESULTS: Hundred thirty-four OSA patients were included. At the time of MWT, 89.6% of the patients were compliant (PAP use ≥4hours/night), and only 9 (6.7%) had persistent sleepiness despite PAP treatment (mean sleep latency at MWT<19.4min). Moderate correlation was observed between final ESS and MWT (Spearman's correlation coefficient=-0.42), but no correlation was found between change in ESS and MWT. Diagnostic performance was as follows for final ESS: sensitivity=55.6%, specificity=84.8%, PPV=20.8%, and NPV=96.4%. CONCLUSIONS: ESS was moderately correlated with MWT in a population of OSA patients compliant with PAP therapy. In this population, ESS showed poor diagnostic performance in identifying patients with persistent excessive daytime sleepiness. CLINICALTRIALS. GOV IDENTIFIER: NCT03629834.

Predictive factors for the participation of general practitioners in lung cancer screening by low-dose CT scan in the Somme department in northern France.

INTRODUCTION: A study on lung cancer screening using low-dose computed tomography (DEP KP80) was conducted in the Somme department in northern France between May 2016 and December 2018. We conducted a cross-sectional survey of family physicians in that department to identify potential predictive factors for their participation in this pilot study. METHODS: A survey questionnaire was sent to the 545 general practitioners (GPs) of the Somme department. This survey rendered it possible to identify the investigators who were active in the DEP KP80 study. The questionnaire's content was focused on the socio-demographic conditions of GPs, their professional practices, and their medical practice situations. RESULTS: The response rate was 38% (206 completed questionnaires). Active investigators in DEP KP80 accounted for 55% (n=113) of the GPs surveyed, and non-investigators for 45% (n=93). Age, gender, or medical practice situation were not related to the active GPs' participation in DEP KP80. A multivariate analysis revealed that two factors were correlated with active participation in organized screening: (1) prescription of nicotine replacement therapy; (2) smoking history of the GP. CONCLUSIONS: Securing the active involvement of family physicians and of the French regional cancer screening coordination centers seems essential for the future organization of lung cancer screening on a regional or national level. Our results demonstrate that incorporating smoking cessation support structures into the program would maximize the mechanism's potential.

Mycobacterium xenopi pulmonary infections: a multicentric retrospective study of 136 cases in north-east France.

BACKGROUND: Owing to its low incidence, the management of Mycobacterium xenopi pulmonary infections is not clearly defined. A multicentre retrospective study was performed to describe the features of the disease and to evaluate its prognosis. METHODS: All patients with M xenopi satisfying the 1997 ATS/IDSA criteria from 13 hospitals in north-east France (1983-2003) were included in the study. Clinical, radiological and bacteriological characteristics and data on the management and outcome were collected. RESULTS: 136 patients were included in the analysis, only 12 of whom presented with no co-morbidity. Three types of the disease were identified: (1) a classical cavitary form in patients with pre-existing pulmonary disease (n = 39, 31%); (2) a solitary nodular form in immunocompetent patients (n = 41, 33%) and (3) an acute infiltrate form in immunosuppressed patients (n = 45, 36%). 56 patients did not receive any treatment; the other 80 patients received first-line treatment containing rifamycin (87.5%), ethambutol (75%), isoniazid (66.2%), clarithromycin (30%) or fluoroquinolones (21%). After a follow-up of 36 months, 80 patients (69.1%) had died; the median survival was 16 months (range 10-22). Two independent prognostic factors were found: the acute infiltrate form was associated with a bad prognosis (hazard ratio 2.6, p = 0.001) and rifamycin-containing regimens provided protection (hazard ratio 0.325, p = 0.006). Clarithromycin-containing regimens did not improve the prognosis. CONCLUSIONS: In contrast to recent guidelines, this study showed three different types of the disease (cavitary, nodular or diffuse infiltrate forms) with a different prognosis. In order to improve survival, all patients with M xenopi infection should be treated with a rifamycin-containing regimen. The usefulness of clarithromycin remains to be evaluated.

[Endobronchial ultrasound with transbronchial needle aspiration: Evaluation of clinical practice]. / Échobronchoscopie avec ponction transbronchique à l'aiguille : évaluation des pratiques.

INTRODUCTION: Endobronchial ultrasound with transbronchial needle aspiration (EBUS-TBNA) has undergone a large increase in France since 2007. The aim is to study the evolution of the indications for EBUS-TBNA in our region during the period 2008-2013. MATERIAL AND METHODS: We conducted a retrospective observational study including all the patients who underwent an EBUS-TBNA procedure in Picardie from 2008 to 2013. The respective proportion for each indication was noted. RESULTS: During the study period, 1036 EBUS-TBNA procedures were performed with a continuous increase in number (86 in 2008 versus 275 in 2013). We observed an increase in the proportion of procedures performed for a suspected diagnosis of sarcoidosis (OR=1.31; IC 95% [1.09-1.58]; P=0.005) and for the simultaneous diagnosis and staging of lung cancer (OR=1.12; IC 95% [1.02-1.24]; P=0.022). For the diagnosis of sarcoidosis, we observed an improvement in the diagnostic yield between the periods [2008-2010] and [2011-2013] (42.9% versus 72.5%). CONCLUSION: A continuous increase in the number of EBUS-TBNA procedures was observed during the period 2008-2013. It was associated with a modification in practice with an increased proportion of procedures performed for the diagnosis of sarcoidosis.

[Risks associated with the use of non-steroidal anti-inflammatory drugs during pneumonia]. / Risques associés à la prise d'anti-inflammatoires non stéroïdiens au cours de la pneumonie.

INTRODUCTION: Outpatient treatment of community-acquired pneumonia (CAP) patients with non-steroidal anti-inflammatory drugs (NSAIDs) is frequent, although this is not based on clinical recommendations and there is no scientific evidence supporting better symptom relief in comparison to acetaminophen. STATE OF THE ART: Experimental data suggest that NSAIDs alter the intrinsic functions of neutrophils, limit their locoregional recruitment, alter bacterial clearance and delay the resolution of inflammatory processes during acute bacterial pulmonary challenge. In hospitalized children and adults with CAP, observational data suggest a strong and independent association between the outpatient exposure to NSAIDs and the occurrence of pleuropulmonary complications (pleural empyema, excavation, and abscess). In the only study taking into account possible protopathic bias, the association still persists. Other markers of morbidity have been described, including delay in hospital management, prolonged antibiotic therapy, and higher transfer rate to an intensive care unit. PERSPECTIVES: Data describing the role of self-medication and the biological mechanisms involved are needed. CONCLUSIONS: Intake of NSAIDs during outpatient treatment of CAP is probably the second modifiable factor of morbidity after inadequate antibiotic therapy. In light of existing data in children and adults, health authorities should urgently reassess the risk-benefit ratio of NSAIDS in CAP.

Noninvasive ventilation using a mouthpiece in patients with chronic obstructive pulmonary disease and acute respiratory failure.

BACKGROUND: Noninvasive positive pressure ventilation (NPPV) delivered via a mouthpiece (mNPPV) has been successfully used in stable chronic restrictive respiratory insufficiency, but not in patients with chronic obstructive pulmonary disease (COPD) and acute respiratory failure (ARF). OBJECTIVES: The purpose of this matched case-control study was to compare the usefulness of mNPPV to noninvasive ventilation using a nasal or oronasal mask (nNPPV) or standard medical treatment (SMT) in COPD patients with ARF. METHODS: Twenty-nine patients receiving mNPPV were matched with 29 patients receiving nNPPV and 29 patients receiving SMT regarding age, SAPSII, admission PaCO(2) and pH. RESULTS: In the mNPPV group, admission PaCO(2) and pH were 78.6 +/- 12 mm Hg and 7.30 +/- 0.04, respectively. mNPPV and nNPPV avoided the need for endotracheal intubation in 27 and 25 patients, respectively (nonsignificant) whereas SMT resulted in a higher mechanical ventilation rate (13 patients). At the end of the treatment protocol, PaCO(2) was lower in the mNPPV group (62.2 +/- 9.6 mm Hg) than in the SMT group (72.4 +/- 20.4 mm Hg, p < 0.018) leading to a significantly higher pH. No significant differences were observed between the mNPPV and nNPPV groups. CONCLUSIONS: In case of moderate respiratory acidosis, noninvasive ventilation using a mouthpiece significantly reduces the endotracheal intubation rate in comparison with SMT and therefore appears to be a second-line alternative to noninvasive ventilation delivered via a mask, especially when poorly tolerated.

[Pneumothorax following recreational inhalation of nitrous oxide]. / Pneumothorax et inhalation volontaire de protoxyde d'azote.

CASE REPORT: A 21 year old man was admitted to hospital as an emergency complaining of left sided chest pain. Chest radiograph revealed a complete non compressive left-sided pneumothorax which resolved following thoracic drainage. A more detailed history revealed repeated and regular use of nitrous oxide by inhalation, for its consciousness-altering effect during rave parties. DISCUSSION: The principal side effects occurring as a consequence of repeated exposures to nitrous oxide are haematological, neuropsychiatric and teratogenic. Rare cases of pneumothorax have been described associated with the use of nitrous oxide occurring as complications of anaesthesia or during laparoscopy where gas diffuses from the abdominal to the pleural cavity. Illicit use of nitrous oxide is rare and usually occurs in medical workers. Its spreading to the public may lead to accidents and unanticipated side effects. CONCLUSION: Inhaled nitrous oxide can reveal asymptomatic pneumothorax by worsening it. The consequences can be dramatic in case of illicit use because of ignorance of side effects.

["Deep purple": a case of hemoptysis during breath-hold diving]. / "Deep-Purple": un cas d'hémoptysie lors d'une plongée en apnée.

INTRODUCTION: Breath-hold diving has been practised since the dawn of humanity but is open to many risks. The consequences mainly involve the respiratory system. The pathophysiological mechanisms are complex because of the multiple forces applied to the body during breath-hold diving. OBSERVATION: The case reported here describes the development of haemoptysis during a single breath-hold dive to a depth of 26 m, associated with acute alveolar haemorrhage. Recovery was spontaneous. CONCLUSION: This event is rarely described and, although often associated with the more frequently reported pulmonary oedema of immersion, the mechanisms remain uncertain, but definitely multifactorial (barotrauma, thoracic blood transfer) and probably enhanced by deconditioning. All this emphasizes the extraordinary stresses that the alveolo-capillary membrane is subject to under these circumstances.

[Mediastinitis after endobronchial ultrasound-guided transbronchial needle aspiration]. / Médiastinite secondaire à une ponction transbronchique échoguidée à l'aiguille : étiologie et prise en charge.

INTRODUCTION: Endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive procedure used for the diagnosis of mediastinal and hilar lymphadenopathy. OBSERVATION: We describe a case of mediastinitis appearing 15 days after an EBUS-TBNA procedure in a 79 years old male patient. The mediastinitis was treated surgically by thoracotomy with a wide excision of infected tissue requiring transplantation of a serratus anterior muscle flap pedicled on a branch of the thoracodorsal artery. It was coupled with broad spectrum antibiotics. This medico-surgical management led to a favorable outcome. Microbiological analysis of the mediastinal collections revealed two pathogens: Streptococcus constellatus (a germ present in the normal flora of the oral cavity) and Mycobacterium tuberculosis. A standard first line quadruple antituberculous drug regimen was subsequently given to the patient. CONCLUSION: This episode of Streptococcus constellatus mediastinitis was a complication of the EBUS-TBNA procedure. The operating channel of the bronchoscope had probably been contaminated when aspirating the oral cavity secretions with subsequent needle contamination and a direct bacterial inoculation during the transbronchial mediastinal puncture. The severity of such a complication justifies a medical consultation in cases of fever or chest pain following an EBUS-TBNA procedure.

[Lung cancer screening with low-dose thoracic CT-scan in the Somme area]. / Dépistage des cancers bronchopulmonaires par tomodensitométrie thoracique à faible dose dans la Somme.

RATIONALE: This feasibility trial proposes to set up in the department of the Somme an annual screening for lung cancer with low-dose thoracic CT. It responds to the first objective of the third cancer plan and follows the publication of the results of the National Lung Screening Trial in 2011. METHODS: The method of this study is to use the existing networks among and between healthcare professionals and the departmental cancer screening structure. The inclusion criteria will be those of the National Lung Screening Trial. Screening will be proposed by treating physicians and chest physicians. The CT-scan will be performed in radiological centers that adhere to the good practice charter for low radiation scanning. A copy of CT results will be sent to the departmental structure of cancer screening (ADEMA80) which will ensure traceability and will perform statistical analysis. The study received funding from the Agence régionale de santé de la Picardie and la ligue contre le cancer. EXPECTED RESULTS: The primary endpoints of this screening will be the number of cancers diagnosed and the survival of the patients. The follow-up of positive examinations, delays in management and the level of participation will also be assessed.

Oxygen consumption and PEEPe in ventilated COPD patients.

The intrinsic positive-end-expiratory pressure (PEEPi) increases the inspiratory load, the cost of breathing and thus oxygen consumption (V(O2)). It has been shown that applying an extrinsic positive-end-expiratory pressure (PEEPe) reduces the inspiratory threshold load but the optimal PEEPe level is still in debate. We hypothesize that the best level of PEEPe could induce a decrease in V(O2) by reducing the V(O2) demands from PEEPi. Nine mechanically ventilated COPD patients were included. The level of PEEPe was determined in accordance with the static PEEPi. V(O2) was measured using an automatic gas analyser during synchronized intermittent mandatory ventilation (SIMV): without PEEPe, with a PEEPe equal to 50% of static PEEPi and with a PEEPe equal to 100% of static PEEPi. Static PEEPi appeared to be significantly correlated with the degree of airflow obstruction (FEV1) (P<0.05). Applying a PEEPe equal to static PEEPi resulted in a significant decrease in V(O2) (P<0.05) whereas the change in V(O2) proved to be unpredictable for a PEEPe level of 50% of static PEEPi. In conclusion, V(O2) decreases progressively when increasing PEEPe up to a level equal to 100% of static PEEPi. Thus, in mechanically ventilated COPD patients with a FEV1 < or = 1000 ml, applying a PEEPe of 5 cmH2O should be recommended.

Community-acquired bacteraemic pneumococcal pneumonia in adults: effect of diminished penicillin susceptibility on clinical outcome.

Pneumococcal pneumonia remains a common disease with a high mortality rate. Between 1995 and 2000, we prospectively analyzed 95 consecutive adult cases of community-acquired bacteraemic pneumococcal pneumonia treated in a single centre. The incidence of pneumococcal resistance to penicillin increased from 19 to 50% during the study period. Multivariate analysis showed that only age and recent hospitalization were independently associated with fatal outcome. The proportion of penicillin-resistant strains was slightly but not significantly higher among patients who died before the fourth hospital day than among those who died later. Patients who died before D4 were more likely to have a recent history of hospitalization, cancer and/or chemotherapy. It thus appears that infection by a resistant pneumococcal strain is not in itself a gravity factor in this setting, but that their acquisition is associated with pejorative clinical features.

[Evaluation of combined chemotherapy with vinorelbine, ifosfamide and cisplatin in the treatment of metastatic non-small cell bronchial carcinoma]. / Evaluation de la chimiothérapie associant vinorelbine-ifosfamide-cisplatine dans le traitement des cancers bronchiques non à petites cellules métastatiques.

INTRODUCTION: In France, cancer of the bronchus is responsible for 25,000 deaths per year. Non small cell lung cancer (NSCLC) represents 80% of bronchial carcinoma of which 40-50% are mefastatic at the time of diagnosis. At present, although the therapeutic benefits are modest, it is now recognised that combination chemotherapy including platinum salts improves the survival of these patients. METHODS: We analysed retrospectively a cohort of 57 patients suffering from stage IV NSCLC treated with chemotherapy combining cisplatin (80 mg/rn2 on day 1), vinorelbine (25 mg/rn2 on days 1 and 8) and ifosfamide (3000 mg/in 2 on day 1), (NIP), repeated every 21 days. RESULTS: The population studied comprised 6 women and 51 men, of average age 59.8 +/- 9.1 years. A history tobacco use (smokers and ex-smokers) was identified in 93%. The WHO performance index was equal to or greater than 2 in 22.8%. All patients were studied in terms of toxicity and overall survival but only 40 (70%) were able to be evaluated in terms of response to treatment (on account of having received more than three cycles of NIP chemotherapy). For the group considered as a whole, the median survival was 6.7 months with a one year survival of 24.5%. Median survival without progression was 4.4 months. The most frequent toxicities were haematological and digestive. They were most common among patients over the age of 70 but had no effect on median survival. For the 40 patients for whom chemotherapy was evaluable, the objective response rate was 20%. This objective response was the only factor that was signiticantly correlated with one year survival: 62.5% in responders, 28.1% in non-responders (p < 0.05). CONCLUSION: Treatment of stage IV NSCLC with NIP chemotherapy is effective and improves the survival of these patients independently of other prognostic factors such as age, the presence of cerebral metastases, performance status, histological type, the number of metastatic sites or the serum LOH level.

[Results of endobronchial ultrasound-guided transbronchial needle aspiration in lung cancer: importance of the lymph node involvement prevalence]. / Résultats des ponctions ganglionnaires transbronchiques sous contrôle d'une écho-endoscopie bronchique: importance de la prévalence.

OBJECTIVE: We studied the non-surgical invasive staging by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) and we detailed the differences of our series, in order to understand the criteria allowing to achieve a better performance. METHODS: Retrospective observational study conducted between 2007 and 2011, including all patients with proven NSCLC who underwent EBUS-TBNA. RESULTS: For the 92 EBUS-TBNA performed, we found a sensitivity of 78%, a specificity of 93%, a positive predictive value (PPV) of 98%, a negative predictive value (NPV) of 45%, an accuracy of 80% and a prevalence of lymph node involvement at 84%. A learning curve has been demonstrated and a significant difference was found based on the number of punctures by procedure (P=0.02) or on histological type (P=0.02). By analyzing the data of the literature, we have been able to demonstrate that the accuracy and the negative predictive value are correlated with the prevalence. If we take into account this correlation, we can consider the results of our study close to those of the literature. CONCLUSION: We highlighted a number of criteria that will influence the diagnostic yield of EBUS-TBNA. While some have already been described, other criteria such as histological type or patient selection criteria are less discussed. The key point is the correlation between the prevalence and EBUS-TBNA results. Results of the assessment of lymph node involvement techniques should be interpreted according to the prevalence of lymph node involvement.

Synchronized intermittent mandatory ventilation with and without pressure support ventilation in weaning patients with COPD from mechanical ventilation.

This prospective study compared two weaning modalities in COPD patients requiring mechanical ventilation (MV) for acute respiratory failure. Nineteen patients with COPD were studied when their precipitating illness was controlled. Although they satisfied the conventional bedside weaning criteria, they could not tolerate any reduction in the respirator rate below 10 cycles/min. At this time, patients were randomized into two groups receiving either synchronized intermittent mandatory ventilation (SIMV) with pressure support ventilation (PSV) (group 1) or SIMV alone (group 2). The volumetric support of ventilation (SIMV rate) was progressively decreased in both groups according to the patient's tolerance with a concurrent decrease in the barometric support of ventilation (PSV levels from 15 cm H2O to 6 cm H2O). At each step of SIMV rate, we found no difference between group 1 and group 2 in arterial blood gases, blood pressure, heart rate, airway occlusion pressure, maximal inspiratory pressure, and oxygen cost of breathing (OCB). At each step, however, group 1 patients showed significantly higher spontaneous tidal volume and lower spontaneous breathing frequency than did group 2 patients. We found a slight but not significant tendency to a shorter weaning period with than without PSV, but no difference in the weaning success. We concluded that (1) conventional weaning criteria might be inaccurate in COPD patients, (2) SIMV appeared very useful in weaning COPD patients from MV, (3) PSV marginally reduced the weaning period when added to SIMV, and (4) the OCB was not significantly improved with PSV.

The SaO2/t diagram as a useful means to express nocturnal hypoxemia.

The computerization of SaO2 recording during polysomnographic monitoring allows the construction of a diagram expressing the percentage of TIB spent at different steps in saturation. We studied the value of this diagram in three groups of male patients: (1) nine healthy subjects (all volunteers); (2) 25 patients with COPD who had a mean daily SaO2 of 92.3 +/- 1.3 percent; and (3) 25 patients with SAS who had a mean daily SaO2 of 92.1 +/- 1.4 percent. The results show the existence of a discriminating quality in the diagram's morphology, the existence of strong correlations (p less than 0.01) between the percentage of TIB spent at SaO2 less than 85 percent, and the total duration of the desaturation dips.

Effectiveness of controlled and spontaneous modes in nasal two-level positive pressure ventilation in awake and asleep normal subjects.

STUDY OBJECTIVES: The purpose of the present study was to compare in awake and asleep healthy subjects, under nasal intermittent positive pressure ventilation (nIPPV) with a two-level intermittent positive pressure device (two-level nIPPV), the efficacy of the controlled and spontaneous modes, and of different ventilator settings in increasing effective minute ventilation (VE). PARTICIPANTS: Eight healthy subjects were studied. SETTING: In the controlled mode, inspiratory positive airway pressure (IPAP) was kept at 15 cm H2O, expiratory positive airway pressure (EPAP) at 4 cm H2O, and the inspiratory/expiratory (I/E) time ratio at 1. The respirator frequencies were 17 and 25/min. In the spontaneous mode experiment, IPAP was started at 10 cm H2O and progressively increased to 15 and 20 cm H2O; EPAP was kept at 4 cm H2O. MEASUREMENTS AND RESULTS: We measured breath by breath the effective tidal volume (VT with respiratory inductive plethysmography), actual respiratory frequency (f), and effective VE. Using the controlled mode, effective VE was significantly higher on nIPPV than during spontaneous unassisted breathing, except in stage 2 nonrapid eye movement sleep at 17/min of frequency; increases in f from 17 to 25/min led to a significant decrease in VT reaching the lungs, during wakefulness and sleep; effective VE was higher at 25 than at 17/min of frequency only during sleep; periodic breathing was scarce and apneas were never observed. Using the spontaneous mode, with respect to awake spontaneous unassisted breathing, two-level nIPPV at 10 and 15 cm H2O of IPAP did not result in any significant increase in effective VE either in wakefulness or in sleep; only IPAP levels of 20 cm H2O resulted in a significant increase in effective VE; during sleep, effective VE was significantly lower than during wakefulness; respiratory rhythm instability (ie, periodic breathing and central apneas) were exceedingly common, and in some subjects extremely frequent, leading to surprisingly large falls in arterial oxygen saturation. CONCLUSIONS: It appears that two-level nIPPV should be used in the controlled mode rather than in the spontaneous mode, since it seems easier to increase effective VE with a lower IPAP at a high frequency than at a high pressure using the spontaneous mode. We suggest that the initial respirator settings in the controlled mode should be an f around 20/min, an I/E ratio of 1, 15 cm H2O of IPAP, and EPAP as low as possible.

Effects of nasal positive-pressure hyperventilation on the glottis in normal awake subjects.

We have recently observed obstructive apneas during nasal intermittent positive-pressure ventilation (nIPPV) and suggested that they were due to hypocapnia-induced glottic closure. To confirm this hypothesis, we studied seven healthy subjects and submitted them to nIPPV while their glottis was continuously monitored through a fiber-optic bronchoscope. During wakefulness, we measured breath by breath the widest inspiratory angle formed by the vocal cords at the anterior commissure along with several other indexes. Mechanical ventilation was progressively increased up to 30 l/min. In the absence of diaphragmatic activity, increases in delivered minute ventilation resulted in progressive narrowing of the vocal cords, with an increase in inspiratory resistance and a progressive reduction in the percentage of the delivered tidal volume effectively reaching the lungs. Adding CO2 to the inspired gas led to partial widening of the glottis in two of three subjects. Moreover, activation of the diaphragmatic muscle was always associated with a significant inspiratory abduction of the vocal cords. Sporadically, complete adduction of the vocal cords was directly responsible for obstructive laryngeal apneas and cyclic changes in the glottic aperture resulted in waxing and waning of tidal volume. We conclude that in awake humans passive ventilation with nIPPV results in vocal cord adduction that depends partly on hypocapnia, but our results suggest that other factors may also influence glottic width.