Evaluation of a transcutaneous carbon dioxide monitor in severe obesity
ABSTRACT To determine the reliability of estimating arterial CO(2) pressure (PaCO(2)) using a recently introduced transcutaneous CO(2) pressure (PtcCO(2)) monitor in severe obese patients.
Observational and interventional study.
District hospital with respiratory ward and bariatric surgery unit.
PtcCO(2) was measured in 35 obese patients with varied pathology, including chronic obstructive pulmonary disease, obstructive sleep apnea syndrome and hypoventilation syndrome. Ten minutes after the probe had been attached to an earlobe, PtcCO(2) was recorded immediately before arterial blood sampling. The PtcCO(2) and PaCO(2) values obtained with two methods were compared by Bland-Altman analysis. In a subgroup of 18 obese patients with chronic obstructive pulmonary disease and/or obstructive sleep apnea syndrome with moderate to severe hypercapnia both PtcCO(2) and PaCO(2) were re-evaluated during continuous positive airways pressure (CPAP) or bi-level positive airway pressure (Bi-PAP) treatment.
The mean difference between PaCO(2) and PtcCO(2) was -1.4 mmHg, and the standard deviation of the difference was 1.3 mmHg. Bland-Altman analysis showed generally good agreement between the two methods with a 95% limit of agreement of -4 to 1.1. The agreement between methods did not significantly change before and during cPAP or Bi-PAP treatment in hypercapnic patients.
The accuracy of estimation of PaCO(2) by transcutaneous monitoring was generally good in comparison with standard arterial blood gases examination. The device appears to be promising for use in obese patients to evaluate abnormalities in their alveolar ventilation.
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ABSTRACT: La mesure de la pression transcutanée en dioxyde de carbone (PtcCO2) n’est pas une technologie récente, les premiers essais remontant au début des années 1960. L’amélioration des moniteurs, la miniaturisation et le développement des électrodes utilisées permettent aujourd’hui de proposer en routine une surveillance de la PtcCO2 continue, fiable, non invasive, simple et rapide. Cet accès indirect et simple à la pression artérielle en CO2 (PaCO2) est pour le clinicien une aide précieuse dans nombre de situations cliniques. Les moniteurs actuels permettent de mesurer aussi de façon rapide et non invasive bien d’autres paramètres (saturation transcutanée en oxygène, fréquences respiratoire et cardiaque, indice de perfusion tissulaire…), utiles pour apprécier la fonction respiratoire d’un patient et pour en suivre l’évolution dans le temps. La tendance actuelle en réanimation est de faire le monitorage le moins invasif possible, même s’il convient d’être prudent quant à l’utilisation abusive ou inadéquate des paramètres ainsi mesurés. Cette revue fait la synthèse du mode de fonctionnement, des avantages et limites, ainsi que des domaines d’application des outils de mesure de la PtcCO2.Réanimation 03/2012; 21(2). DOI:10.1007/s13546-012-0450-4
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ABSTRACT: In the Western world, the prevalence of obese patients in intensive care units (ICU) is increasing. Additionally, morbid obesity has dramatic consequences on pulmonary function . Therefore, respiratory physicians and intensivists are more likely to manage a larger number of acute hypercapnic respiratory failure (AHRF) episodes in patients with a body mass index (BMI) .30 kg?m -2 . Cor pulmonale is a major cause of ICU admission, which requires mechanical ventilation with higher mortality in obese compared with nonobese patients . It is, therefore, surprising that experience of AHRF in obese patients has rarely been reported in the literature and, consequently, evidence-based guidelines remain to be established . If there are very few data in the literature about noninvasive ventilation (NIV) in obese patients with hypoxaemic respiratory failure , there are cumulating reports that suggest that NIV plays a key role in the treatment of obese patients with AHRF . AHRF in obese patients: epidemiological data Clinical characteristics and specificities of obese patients hospitalised in ICUs are currently not well established. In a retrospective cohort study in obese and nonobese patients, it has been shown that obese patients had more major comorbidities than nonobese patients, with a higher prevalence of COPD, sleep respiratory disorders, cor pulmonale and pulmonary hypertension . Similarly, obese patients had a higher prevalence of coronary heart diseases and systemic hypertension. In this study, it has been highlighted that pneumonia and hypoxaemic acute respiratory failure were the most frequent hospitalisation reasons for obese patients in the ICU . Although both cohorts had the same severity at admission, mean length of hospital stay was longer in obese patients compared with nonobese patients. This more-prolonged stay was associated with a higher incidence of complications during ICU stay and a more prolonged weaning period . A total of 12% of obese patients were tracheostomised compared with only 4% in nonobese patients. KOENIG  found that the probability of inhalation pneumonia was increased in obese patients, especially during post-surgery, due to an increase in abdominal pressure, increased incidence of gastro-oesophageal reflux and an augmented gastric pH. This should be paralleled with physiopathological consequences of obesity with an increased respiratory work during weaning, due to increased airway resistance, a low thoracic Eur Respir Mon, 2008, 41, 47–59. Printed in UK -all rights reserved. Copyright ERS Journals Ltd 2008; European Respiratory Monograph; ISSN 1025-448x.