The increased prevalence of adult obesity has been one of the most striking epidemiologic phenomenon in most countries around the world during these last 100 years. It is also a matter of great concern in children 5 to 12 years old in whom the prevalence of obesity has been multiplied by three in the United States and by four in France between 1960 and 2000. (1)
Because adult obesity is a risk factor for obstructive sleep apnea syndrome (OSAS), obesity-hypoventilation syndrome (OHS), acute hypercapnic respiratory failure (AHRF), and higher incidence of respiratory postsurgical complications, it is not surprising to see that obesity is now considered as an emerging cause of chronic respiratory failure (CRF) requiring domiciliary ventilatory assistance. (2) CRF in obese patients is a frequent issue in clinical practice and is usually diagnosed either in the context of an AHRF in the emergency department or when investigating a potential diagnosis of OSAS or even during a preoperative evaluation. Approximately 10% of patients with OSAS have daytime hypercapnia, often associated with pulmonary hypertension. (3) Obstructive airways disease may be associated in some of these patients and constitutes the so-called overlap syndrome. (4-6) Another clinical picture of CRF in obese patients is OHS, (3) previously called the Pickwickian syndrome, (7) which is associated with a range of different sleep respiratory patterns such as hypoventilation, obstructive apneas, central apneas, or a combination of these.
Noninvasive ventilation (NIV) using a nasal or facial mask has been proposed to alleviate respiratory failure of various origins. (8) In obese patients, mechanisms of action probably include unloading of respiratory muscles, (9) correction of nocturnal hypoventilation and resetting of the respiratory centers. (8) However, the data are limited, and we need to better understand the physiologic effects of NIV in these patients. Surprisingly, very few articles or chapters have focused on the issue of obese patients treated by NIV in the acute (10-12) or the chronic setting, (13-16) and only included a limited number of patients with short follow-up. Waiting for a clinical assessment like in acute COPD, NIV should be today considered early in the management of an obese patient with AHRF (when endotracheal intubation is not immediately required) in order to prevent the risk from endotracheal intubation, to reduce hospital stay and to correct the underlying sleep respiratory disorders. Domiciliary NIV should be also considered when daytime hypercapnia and nocturnal hypoventilation are present. In this situation, precursory clinical signs often associate morning headaches, impaired cognitive function, or reduced daytime vigilance (the "obese sleepy patient" as described by Claman et al (17)), but diagnoses may also be made much later with cor pulmonale and/or nocturnal arrhythmias.
In this issue of CHEST (see page 587) De Llano et al describe a large group of 54 obese patients treated by NIV for hypercapnic respiratory failure and followed up at least during 1 year (50 [+ or -] 25 months [[+ or -] SD]). NIV was initiated electively in 20 patients and in the immediate outcome of an AHRF episode in the remaining 34 patients. Most of the patients improved under bilevel positive pressure ventilation adapted according to night oximetry and daytime arterial blood gas (ABG) analysis, and were discharged home with nocturnal NIV and additional oxygen. The authors show that NIV is efficient either in acute as in chronic setting with a reduction of daytime sleepiness, a sustained improvement of ABG values on a long-term basis, and a low mortality rate. However, NIV was not accepted by 15 of the 69 initially screened patients, and this situation was associated with a significant risk of death (four of seven in ARF and three of eight in CRF). Another point emphasized by De Llano et al is the primary role of polysomnographic (PSG) recordings during follow-up, when patients achieve a stable clinical condition: 13% of patients were free of associated OSAS, and the remaining received a diagnosis of OSAS with an apnea-hypopnea index of 43.3 [+ or -] 25.6. In 31 patients, this PSG recording attested that a simple continuous positive airway pressure (CPAP) device was sufficient to prevent from further recurrence of respiratory failure. Moreover, a significant proportion of patients were allowed to stop additional oxygen therapy.
Therefore, a new sphere of activity is opening for respiratory physicians, especially those working in intermediate care units where a significant number of obese patients with daytime hypercapnia are managed, either in the acute or the chronic setting. At hospital admission for AHRF and otherwise contraindicated, NIV should be the first-line treatment using bilevel positive pressure ventilators and sometimes flow-preset ventilators in case of primary failure. Domiciliary NIV allows to correct the underlying sleep respiratory disorders and may prevent from the risk of recurrent AHRF episodes. PSG studies may help to titrate NIV during initiation and also to evaluate a further shift of the ventilatory assistance (with or without oxygen) to a CPAP device alone.
Antoine Cuvelier, MD, PhD
Jean-Francois Muir, MD, FCCP
Drs. Cuvelier and Muir are from the Service de Pneumologie, Hopital de Bois-Guillaume, Rouen, France.
Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).
Correspondence to: Antoine Cuvelier MD, PhD, Service de Pneumologie et Unite de Soins Intensifs Respiratoires, Hopital de Bois-Guillaume, CHU de Rouen, 76031 Rouen CEDEX, France; e-mail: firstname.lastname@example.org
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