A. Hazenberg

Validation of a Transcutaneous CO2 Monitor in Adult Patients with Chronic Respiratory Failure

Background: Home mechanical ventilation is usually started in hospital as arterial blood gas sampling is deemed necessary to monitor CO2 and O2 adequately during institution of ventilatory support. A non-invasive device to reliably measure CO2 transcutaneously would alleviate the need for high care settings for measurement and open the possibility for home registration. Objectives: In this study we investigated whether the TOSCA® transcutaneous CO2 (PtcCO2) measurements, performed continuously during the night, reliably reflect arterial CO2 (PaCO2) measurements in adults with chronic respiratory failure. Methods: Paired measurements were taken in 15 patients hospitalised to evaluate their blood gas exchange. Outcomes were compared 30 min, 2, 4, 6 and 8 h after attaching the sensor to the earlobe. A maximum difference of 1.0 kPa and 95% limits of agreement (LOA) of 1 kPa between CO2 pressure measurements, following the analysis by Bland and Altman, were determined as acceptable. Results: Mean PtcCO2 was 0.4 kPa higher (LOA –0.48 to 1.27 kPa) than mean PaCO2 after 30 min. These figures were 0.6 kPa higher (LOA –0.60 to 1.80 kPa) after 4 h, with a maximum of 0.72 kPa (LOA 0.35 to 1.79 kPa) after 8 h. The corresponding values for changes in PtcCO2 versus PaCO2 were not significant (ANOVA). Conclusions: PtcCO2 measurement, using TOSCA, is a valid method showing an acceptable agreement with PaCO2 during 8 h of continuous measurement. Therefore, this device can be used to monitor CO2 adequately during chronic ventilatory support.

Mechanisms involved in symptomatic myocardial bridging

Background.In patients with extensive myocardial bridging, evaluation of its clinical significance remains a challenge.Hypothesis.Sequential invasive testing is feasible and gives more insight into the pathophysiological mechanism of bridging-related angina.Methods.Twelve patients with chest pain, proven ischaemia and extensive myocardial bridging were assessed. Myocardial bridging was evaluated at rest, during intracoronary acetylcholine infusion, through coronary flow velocity and flow reserve measurements, and during dobutamine stress.Results.The mean length of the bridging segment was 24.9 mm (QCA; range 8.4-48.0 mm). Acetylcholine infusion caused severe vasospasm in two patients. In these two patients anginal symptoms were related to vasospasm and sequential testing was discontinued. In the remaining ten patients sequential testing was continued. Coronary flow reserve was normal in all patients: 3.3±0.6. In six patients reliable quantitative measurements could be performed during dobutamine stress. The mean systolic diameter of the bridging segment was 1.6±0.4 at baseline and 1.3±0.3 during dobutamine stress (mean of differences 0.38 (95% CI 0.1-0.7)). The difference between the diastolic and systolic diameter in the bridging segment increased from 0.3±0.2 mm at baseline to 1.0±0.5 mm during dobutamine infusion (mean of differences 0.6 (95% CI 0.3 to 0.9)).Conclusion.Sequential testing for bridging is feasible and may disclose endothelial dysfunction or spasm as an underlying mechanism in a minority of patients. Coronary flow reserve was preserved. Dobutamine stress unmasked further lumen reduction and may give further insight into the clinical significance of myocardial bridging in individual patients. (Neth Heart J 2008;16:10-5.)

Is chronic ventilatory support really effective in patients with amyotrophic lateral sclerosis

Most patients with amyotrophic lateral sclerosis (ALS) develop respiratory insufficiency in the advanced stage of their disease. Non-invasive ventilation (NIV) is commonly regarded to be a treatment that is effective in reducing these complaints. To assess whether the effect of NIV on gas exchange and quality of life (QOL) is different in patients with ALS versus without ALS. A post hoc analysis was done with data from a previously published trial, in which all patients were instituted on NIV. Arterial blood gasses were assessed next to QOL by generic as well as disease-specific questionnaires. 77 patients started NIV: 30 with ALS and 47 without. Both groups showed significant improvements in blood gasses after 2 and 6 months. Compared to the non-ALS group, the ALS group had significantly worse scores after 6 months in MRF-28, SRI, HADS and SF-36 than the non-ALS group. This study shows that NIV improves gas exchange, both in patients with and without ALS. QOL improves markedly more in patients without ALS than in those with ALS, in whom only some domains improve. Our observation of little or no effect in ALS patients warrants a large study limited to ALS patients only.

Facioscapulohumeral muscular dystrophy and respiratory failure; what about the diaphragm?

Introduction We present a case of facioscapulohumeral muscular dystrophy (FSHD) with a diaphragm paralysis as the primary cause of ventilatory failure. FSHD is an autosomal dominant inherited disorder with a restricted pattern of weakness. Although respiratory weakness is a relatively unknown in FSHD, it is not uncommon. Methods We report on the clinical findings of a 68-year old male who presented with severe dyspnea while supine. Results Supplementing our clinical findings with laboratory, electrophysiological and radiological performances led to the diagnosis of diaphragm paralysis. Arterial blood gas in sitting position without supplemental oxygen showed a mild hypercapnia. His sleep improved after starting non-invasive ventilation and his daytime sleepiness disappeared. Discussion We conclude that in patients with FSHD who have symptoms of nocturnal hypoventilation, an adequate assessment of the diaphragm is recommended. This is of great importance as we know that nocturnal hypoventilation can be treated effectively by non-invasive ventilation.

Vital capacity in lying position: important in Duchenne patients

To the Editors: It was with great interest that we read the paper of Lo Mauro et al . 1 entitled “Abdominal volume contribution to tidal volume as an early indicator of respiratory impairment in Duchenne muscular dystrophy’’ in a recent issue of the European Respiratory Journal . This paper very elegantly explained the contribution of the abdominal volume to tidal volume if patients with Duchenne disease are getting older and change …

Vital capacity in lying position

We thank P. Wijkstra and co-workers for their interest and comments regarding our paper, ‘‘Abdominal volume contribution to tidal volume as an early indicator of respiratory impairment in Duchenne muscular dystrophy’’ [1]. They wonder if our findings of progressive drop of abdominal contribution to tidal volume in Duchenne muscular dystrophy (DMD) are somewhat related to: 1) differences in forced vital capacity (FVC) between sitting and supine position; and 2) nocturnal hypercapnia. These questions are of great interest and they deal with three key aspects regarding the prognosis and the management of patients with DMD and other primary neuromuscular diseases, namely the noninvasive assessment of diaphragm function, the evaluation of sleep disordered breathing and the choice of the correct timing for the introduction of nocturnal noninvasive mechanical ventilation.