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Biomedical subjects

W De Backer

Publications and source records attributed to W De Backer.

At least 19 recordsLinked to original sources
PubMed2006

Correlation between severity of sleep apnea and upper airway morphology based on advanced anatomical and functional imaging.

Determination of the apnea hypopnea index (AHI) as a measure of the severity of obstructive sleep apnea/hypopnea syndrome (OSAHS) is a widely accepted methodology. However, the outcome of such a determination depends on the method used, is time consuming and insufficient for prediction of the effect of all treatment modalities. For these reasons more methods for evaluating the severity of OSAHS, based on different imaging modalities, have been looked into and recent studies have shown that anatomical properties determined from three-dimensional (3D) computed tomography (CT) images are good markers for the severity of the OSAHS. Therefore, we correlated anatomical measurements of a 3D reconstruction of the upper airway together with flow simulation results with the severity of OSAHS in order to find a combination of variables to indicate the severity of OSAHS in patients. The AHI of 20 non-selected, consecutive patients has been determined during a polysomnography. All patients also underwent a CT scan from which a 3D model of the upper airway geometry was reconstructed. This 3D model was used to evaluate the anatomical properties of the upper airway in OSAHS patients as well as to perform computational fluid dynamics (CFD) computations to evaluate the airflow and resistance of this upper airway. It has been shown that a combination of the smallest cross-sectional area and the resistance together with the body mass index (BMI) form a set of markers that predict very well the severity of OSAHS in patients within this study. We believe that these markers can be used to evaluate the outcome of an OSAHS treatment.

Computer Simulation↗
PubMed2005

Assessment of progression of COPD: report of a workshop held in Leuven, 11-12 March 2004.

Recently performed long term trials have enhanced the insight into the assessment of progression of COPD. The present review focuses on the initial assessment of COPD in general practice and the assessment of disease progression. Several variables may be used to assess this progression, all of which are associated with significant methodological problems. Finding the appropriate mix of outcome measures to capture all aspects of disease progression is a significant challenge.

Belgium↗
PubMed2005

Quality control of spirometry: a lesson from the BRONCUS trial.

This report describes the quality control programme used within the Bronchitis Randomized on N-acetylcysteine (NAC) Cost-Utility Study, a trial designed to assess the decline in lung function, exacerbation rate, health status, and cost-effectiveness with NAC or a placebo in 523 patients with chronic obstructive pulmonary disease over a 3-yr period. Spirometry was scored from 0 (worst quality) to 6 (best quality). The mean score of 314 spirometries from 243 patients evaluated during the trial was 5.63+/-0.83. Linear regression analysis of the scores of 47 participating centres plotted against the time at which spirometries were performed yielded an intercept of 5.7+/-0.5 and a slope of -0.0001+/-0.001, which suggests that the initial high quality was maintained over time. Retrospective examination of a further 345 postbronchodilator spirometries from 208 patients with a forced expiratory volume at one second exceeding the mean individual value recorded over the study in excess of 20% revealed a slightly lower quality of the start-of-test manoeuvre compared with the 314 spirometries. In conclusion, these findings would suggest that the quality control programme is likely to have helped achieve and maintain long-term spirometry performance in the Bronchitis Randomized on N-acetylcysteine (NAC) Cost-Utility Study trial. Special care should be paid to the spirometries whose forced expiratory volume in one second values exceed the mean value.

Acetylcysteine↗
PubMed2003

Aortic root diameter and nasal intermittent positive airway pressure treatment in Marfan's syndrome.

We report on a patient with Marfan's syndrome, with coexistent obstructive sleep hypopnea (OSH) and restrictive lung disease, complicated by respiratory insufficiency, who was successfully treated with nasal intermittent positive airway pressure (NIPPV) and oxygen. NIPPV therapy turned out to be effective on arterial gas exchange and well tolerated. Moreover, progressive dilatation of the aortic root was attenuated during NIPPV, but could, however, not be reversed. We hypothetized that (at least partially) a decrease of nocturnal intrathoracic pressures could explain this.

Adult↗
PubMed2003

Non-invasive exclusion and diagnosis of pulmonary embolism by sequential use of the rapid ELISA D-dimer assay, clinical score and spiral CT.

Pulmonary angiography is the gold standard for segmental pulmonary embolism (PE) but no longer for its subsegmental PE, because the inter-observer agreement for angiographically documented subsegmental PE is only 60%. Two non-invasive tools exclude PE with a negative predictive value of > 99%: a normal perfusion lung scan and a normal rapid ELISA VIDAS D-dimer test. The positive predictive value of a high probability ventilation-perfusion lung scan (VP-scan) is only 85% to 87%. The combination of a low clinical score and a non-diagnostic VP-scan safely exclude PE without the need of angiography. The prevalence of PE and that of an alternative diagnosis in symptomatic patients with a non-diagnostic VP-scan are 10% to 20% and 30% to 45%, respectively. Helical spiral computed tomography (CT) detects all clinically relevant PE and a large number of alternative diagnoses in symptomatic patients with a non-diagnostic or high probability VP-scan. The positive predictive value of the spiral CT is > 95%. Single-slice helical CT as the primary diagnostic test in patients with suspected PE in retrospective outcome studies and in prospective multicenter management studies indicate that the negative predictive value of a negative spiral CT preceded or followed by a negative compression ultrasonography (CUS) is > 99%. Therefore, a helical spiral CT can replace both the VP-scan and pulmonary angiography to safely rule in and out PE. A negative rapid ELISA VIDAS D-dimer test result will reduce the need for helical spiral CT by 25% to 35%.

Aged↗
PubMed2002

Remediastinoscopy after neoadjuvant therapy for non-small cell lung cancer.

Despite technical difficulties due to mediastinal fibrosis, remediastinoscopy can be a valuable tool in the restaging of non-small cell lung cancer after neoadjuvant therapy. The aim of our study was to evaluate the feasibility, sensitivity and accuracy of remediastinoscopy. From November 1994 to July 2001 we performed a remediastinoscopy in 27 patients after neoadjuvant therapy. Their age ranged from 35 to 80 years (mean 61.9+/-11.9). In all 27 patients it was possible to perform a remediastinoscopy without major technical difficulties and take biopsies of the lymph nodes that were initially invaded by tumour. Remediastinoscopy was positive in 11 patients (40.7%) and negative in 16 (59.3%). In the 11 patients with a positive remediastinoscopy a complete resection was not judged possible and therefore, an unnecessary thoracotomy was avoided. In four patients, remediastinoscopy turned out to be false negative. So, in our series, sensitivity was 73%, specificity 100% and accuracy 85%. The positive and negative predictive values were 100 and 75%, respectively. Previous mediastinoscopy is no contra-indication for a repeat one after neoadjuvant therapy. Although sensitivity and accuracy are lower than that of a first mediastinoscopy, remediastinoscopy is useful to select patients for surgical resection after induction therapy.

Adult↗
PubMed2002

Intermittent positive airway pressure by nasal mask as a treatment for respiratory insufficiency in a patient with syringomyelia.

We report a case of a 73-year-old woman with chronic respiratory failure in association with syringohydromyelia and sleep apnea. She was initially intubated and mechanically ventilated. Weaning from the ventilator was only successful after nasal intermittent positive airway pressure therapy was started. A normalization of arterial blood gas exchange could be achieved.

Aged↗
PubMed2002

Short-term CPAP does not influence the increased CO2 drive in idiopathic central sleep apnea.

Continuous positive airway pressure (CPAP) improves idiopathic central sleep apnea (ICSA), but the mechanisms are not completely understood. It has been demonstrated that some ICSA patients have an increased CO2 drive, expressed by the hypercapnic ventilatory response (HCVR). The aim of our study was to evaluate whether CPAP can decrease the HCVR in successfully treated ICSA patients. Also the central apnea mean duration (CMD) was studied. Nine patients were evaluated. Their apnea-hypopnea index at baseline was high, but decreased from 50 +/- 5 to 8 +/- 3, during 5 +/- 1 cm H2O CPAP. After one month CPAP high values were still found for HCVR (2.69 +/- 0.23 L.min-1.mmHg-1 at baseline, 2.71 +/- 0.33 L.min-1.mmHg-1 after CPAP). Sleep quality was only improved by a decrease in the arousal index (from 29 +/- 12 to 6 +/- 1 a night) (p = 0.04). Daytime arterial O2 partial pressure (PaO2) increased from 73 +/- 4 mmHg to 85 +/- 3 mmHg (p = 0.02), whereas daytime arterial CO2 partial pressure (PaCO2) remained unchanged (from 41 +/- 1 mmHg to 40 +/- 1 mmHg). CMD was 21 +/- 6 s before and 13 +/- 1 s after CPAP (p = 0.05). The presence of hypersomnolence decreased from in 89% to in 33% of the patients. It is concluded that CPAP treatment can induce a subjective and objective improvement in ICSA patients, with improved sleep-related respiratory indices, daytime PaO2, but without a change in CO2 drive. High chemical drives seem to be the cause and not the consequence of sleep disordered breathing and persist after treatment.

Analysis of Variance↗
PubMed2001

Therapeutic electrical stimulation of the hypoglossal nerve in obstructive sleep apnea.

BACKGROUND: Hypoglossal nerve stimulation has been demonstrated to relieve upper airway obstruction acutely, but its effect on obstructive sleep apnea is not known. OBJECTIVE: To determine the response in obstructive sleep apnea to electrical stimulation of the hypoglossal nerve. METHODS: Eight patients with obstructive sleep apnea were implanted with a device that stimulated the hypoglossal nerve unilaterally during inspiration. Sleep and breathing patterns were examined at baseline before implantation and after implantation at 1, 3, and 6 months and last follow-up. RESULTS: Unilateral hypoglossal nerve stimulation decreased the severity of obstructive sleep apnea throughout the entire study period. Specifically, stimulation significantly reduced the mean apnea-hypopnea indices in non-rapid eye movement (mean +/- SD episodes per hour, 52.0 +/- 20.4 for baseline nights and 22.6 +/- 12.1 for stimulation nights; P<.001) and rapid eye movement (48.2 +/- 30.5 and 16.6 +/- 17.1, respectively; P<.001) sleep and reduced the severity of oxyhemoglobin desaturations. With improvement in sleep apnea, a trend toward deeper stages of non-rapid eye movement sleep was observed. Moreover, all patients tolerated long-term stimulation at night and did not experience any adverse effects from stimulation. Even after completing the study protocol, the 3 patients who remained free from stimulator malfunction continued to use this device as primary treatment. CONCLUSION: The findings demonstrate the feasibility and therapeutic potential for hypoglossal nerve stimulation in obstructive sleep apnea.

Adult↗
PubMed2001

Evaluation for sleep apnea in patients with Ehlers-Danlos syndrome and Marfan: a questionnaire study.

Sleep complaints are frequently reported by patients with Marfan and Ehlers-Danlos syndrome (EDS). We examined the exact nature of sleep complaints in these patients. A representative sample of Marfan and EDS patients responded to a general sleep questionnaire, including the Epworth Sleepiness Scale (ESS) and the Medical Outcomes Study Short-Form 36 (SF-36) health-related quality of life (QOL) questionnaire. Fifteen Marfan patients and 9 EDS patients were evaluated and compared to 24 healthy controls, matched for age, sex and body mass index. Maintaining sleep was frequently disturbed in Marfan (40%, p < 0.04) as well as in EDS patients (56%, p < 0.01). Sleep apnea was exclusively reported by Marfan patients (27%, p = 0.03). Periodic limb movements were much more reported in EDS (67%, p = 0.02) than in Marfan (27%, p = 0.25) compared to controls (8%). Pain and back complaints were highly presented in both groups, but most pronounced in EDS patients (47% in Marfan versus 77% in EDS). No differences for the scores in the ESS were found. For all SF-36 questionnaire items, scores were much lower in patient groups, except for emotional problems. We found that sleep complaints were not rare in Marfan and EDS patients and correlated well with different QOL items. Our study calls for greater attention to the presence of apnea, pain and periodic limb movements in these patients.

Adult↗
PubMed2000

Influence of longterm CPAP therapy on CO(2) drive in patients with obstructive sleep apnea.

According to recent publications, the values of the hypercapnic ventilatory responses (HCVR) in normocapnic obstructive sleep apnea (OSA) patients are highly variable, but they are usually within the normal range. In our study, CPAP therapy during 1 month did not seem to influence the HCVR [Verbraecken, J., De Backer, W., Willemen, M., De Cock, W., Wittesaele, W., Van de Heyning, P., 1995. Respir. Physiol. 101, 279-287]. It is, however, not well studied whether long term (1 year) CPAP therapy can influence HCVR in normocapnic patients. Therefore, we evaluated the effect of 1 year CPAP therapy on CO(2) drive in 20 OSA patients. The slope of HCVR (SHCVR) changed from 2.35+/-0.21 L min(-1) mmHg(-1) (control) to 1.66+/-0.16 L min(-1) mm Hg(-1) (P=0.04), but the mean within subject coefficient of variation in repeated measurements of SHCVR in treated and untreated OSA patients was not statistically different. Pa(O(2)) increased from 72+/-2 mm Hg to 80+/-2 (1 year) mm Hg. We conclude that CPAP therapy improves daytime gas exchange in normocapnic OSA and may possibly decrease CO(2) drive (slope) after a treatment period of 1 year.

Blood Gas Analysis↗
PubMed1999

Oxidatively modified proteins in bronchoalveolar lavage fluid of patients with ARDS and patients at-risk for ARDS.

Oxidative stress in acute respiratory distress syndrome (ARDS) is considered as an important pathophysiological mechanism in acute impairment of lung function. The present study investigated whether a pulmonary oxidant-antioxidant imbalance is indicated by substantial oxidative modification of proteins in bronchoalveolar lavage (BAL) fluid. Oxidatively modified proteins in BAL fluid, as measured by the reduction of protein carbonyl groups with tritiated borohydride, were studied in control subjects, patients with clinically established ARDS, and patients considered at-risk for ARDS because they had had coronary bypass surgery. Subsets of these at-risk patients were pretreated either with methylprednisolone or N-acetylcysteine. The carbonyl content of BAL fluid proteins was greatly increased in ARDS patients (5.0+/-13 nmol carbonyl x mL(-1) BAL fluid; mean+/-SEM; p=0.0004; n=10) and moderately increased in the untreated patients at-risk for ARDS (1.3+/-0.2 nmol x mL(-1); p=0.027; n=19) compared with controls (0.8+/-0.2 nmol x mL(-1); n=12). The two other at-risk groups pretreated either with methylprednisolone or N-acetylcysteine showed carbonyl values that were statistically not different from the controls (1.2+/-0.2 nmol x mL(-1); p=0.13; n=13, and 1.1+/-0.3 nmol x mL(-1); p=0.40; n=8, respectively). These results show that oxidatively modified proteins clearly accumulated in bronchoalveolar lavage fluid of acute respiratory distress syndrome patients, and to a minor extent in untreated at-risk patients. These data suggest a severe oxidant-antioxidant imbalance in acute respiratory distress syndrome.

Acetylcysteine↗
PubMed1998

Central sleep apnea after interrupting longterm acetazolamide therapy.

One month administration of acetazolamide (ACET) (at sea level) improves periodic breathing and decreases the number of central apneas (CA) (De Backer et al., 1995 Am. J. Respir. Crit. Care Med. 151, 87-91) in nonhypercapnic central apnea syndrome. It remains unclear whether cessation of therapy would provoke recurrence of symptoms. In the present study we evaluated the number of CA after 1 and 6 months interruption of ACET therapy. Eight patients with central sleep apnea were included [central apnea index (CAI) > 5 or apnea and hypopnea index (AHI) > 10 and obstructive apnea index (OAI) < 5]. Polysomnography was repeated once after 1 month treatment (N2), after 1 month off treatment (N3) and after 6 months off treatment. CAI (25 +/- 10 at N1) decreased during N2 (4 +/- 2) and N3 (5 +/- 3) and remained low after N4 (3 +/- 1). However an increase in the number of obstructive apneas and central hypopneas could be observed together with a shift from central apnea to hypopnea after N4. Maybe ACET induces a long lasting resetting of the CO2 threshold which is still present after interruption of the therapy.

Acetazolamide↗
PubMed1998

Relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea.

Previously we showed that CO2 drive is increased in patients with obstructive sleep apnea (OSA). In the present study we would like to evaluate a possible relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea (CSA). We compared the hypercapnic ventilatory response (HCVR) between patients with OSA and CSA. HCVR was correlated with total event time and mean event duration in both groups. 17 normocapnic patients in each group and 14 controls were studied. The apnea patients were matched for apnea-hypopnea index, age, sex, and BMI. SHCVR (slope) tended to be higher in apnea patients than in controls without statistical significancy: controls 1.65 (0.16), CSA 2.17 (0.22), OSA 2.55 (0.35) (l/min per mmHg) (P = 0.13). A significant correlation was found between HCVR and event time in CSA (0.52, P = 0.04) and between HCVR and apnea mean duration in OSA (r = 0.52, P = 0.04). We conclude that while CO2 drive was not statistically increased in both apnea types, small changes can contribute to breathing instability and may increase the total event time (in CSA) but may also shorten the apnea duration (in OSA).

Adult↗
PubMed1998

Repeat mediastinoscopy in the staging of lung cancer.

OBJECTIVE: Despite technical difficulties due to mediastinal fibrosis, repeat mediastinoscopy can be a valuable tool in the restaging of lung cancer. It provides essential pathological information on mediastinal invasion when selecting patients for surgical resection after induction chemotherapy in stage IIIa disease. The aim of our study was to evaluate the feasibility, sensitivity and accuracy of repeat mediastinoscopy. METHODS: From 1994 to 1997 we performed a repeat mediastinoscopy in 15 patients (13 men, two women) with bronchogenic carcinoma. Their age ranged from 49 to 75 years. (mean 64.7). Seven patients had induction chemotherapy for a non-small cell bronchogenic carcinoma with positive N2 nodes on mediastinoscopy. Four patients had a second primary contralateral lung cancer, one had a locoregional recurrence of bronchogenic carcinoma. The other three had a first mediastinoscopy for other reasons than lung cancer, repeat mediastinoscopy being performed for staging of malignant disease. RESULTS: In all 15 patients it was possible to perform a complete repeat mediastinoscopy. In one patient repeat mediastinoscopy turned out to be false negative, so, in our series, sensitivity was 87.5%, specificity 100% and accuracy 93.7%. CONCLUSION: Previous mediastinoscopy is no contraindication for a repeat one. Repeat mediastinoscopy offers valuable pathological information in restaging of lung cancer.

Aged↗
PubMed1998

[Nasal CPAP in sleep-related respiration disorders: patient profile, therapy compliance and influence of gas exchange and lung function pattern].

A survey performed in 100 CPAP users indicated that irritation of the face, a painful nose and nasal obstruction were among the most frequently mentioned complaints in chronic CPAP users. In 132 normocapnic SAS patients a significant improvement of PaO2 was shown, with a decrease of the alveolo-arterial oxygen difference. This improved gas exchange was parallelled by a significant increase in the FRC and TLC. Maybe a modulation in force of the respiratory muscles may be involved. These data were more pronounced in obstructive sleep apnea than in central sleep apnea. In 50 chronic CPAP users we could show a lower AHI immediately after CPAP withdrawal after a previous prolonged treatment. These findings may support the insufflation theory as a mechanism of action of CPAP. Traditionally, mechanical splinting of the upper airway has been considered as the dominant mechanism of action. Other mechanisms like changes in regulation of breathing and decrease of the pharyngeal edema may be involved as well.

Blood Gas Analysis↗