Hypoventilation daytime

Hukins CA, Hillman DR. Daytime predictors of sleep hypoventilation in Duchenne muscular dystrophy. Am J Respir Crit Cate Med 2000 161 166-170. 

Figure 1 Home oximetry (A) and split-night polysomnography (B) in an ALS patient with daytime hypercapnia and hypoventilation symptoms.

Ward S, Chatwin M, Heather S, et al. Randomised controlled trial of non-invasive ventilation (NIV) for nocturnal hypoventilation in neuromuscular and chest wall disease patients with daytime normocapnia. Thorax 2005 60 1019-1024. 

Careful patient selection is important if diaphragmatic pacing is to be effective. The main indications are SCI above C3, central alveolar hypoventilation, which may be idiopathic or secondary to brain stem injury, or other conditions that affect daytime or nocturnal ventilatory control. Whereas patients with high SCI require 24-hour ventilation, those with hypoventilation may only require support for part of this cycle. 

This case illustrates that close to normal daytime gas exchange can occur despite hypoventilation at night. As the latter was progressive, the repeat sleep study was valuable in determining when to initiate ventilatory support. 

OHS, previously called the Pickwickian syndrome (6), is defined as the association of obesity, sleep-disordered breathing (SDB) with daytime h)q)ersomnolence, and hypercapnia (Pacc>2 > 45 mmHg) in the absence of any other respiratory disease (Fig. 1). SDB can present as obstructive apneas and hypopneas, obstructive hypoventilation due to increased upper airway resistance, and/or central hypoventilation (7). The prevalence of OHS is 36% in patients with BMI between 35 and 40 kg/m, and 48%, if BMI equals or exceeds 50 (8). Without adequate treatment, patients with OHS develop cor pulmonale and recurrent episodes of hypercapnic respiratory failure, and loss of survival (Fig. 2). OHS is one of the many etiologies of CRF and has become a growing indication to initiate longterm noninvasive ventilation (NIV) in most European countries (9,10). 

Mechanical ventilation (MV) with bi-level NIV must be considered in the presence of nocturnal hypoventilation, especially if accompanied by cor pulmonale, nocturnal arryth-mias, morning headache, impaired cognitive function, or reduced daytime vigilance. Right heart failure is also frequently present. The obese sleepy patient (27) with chronic hypoxia and hypercapnia is the typical presentation of OHS. To adapt to NIV, it is important to identify the nocturnal respiratory pattern of such patients. 

Chouri-Pontarollo N, Btnel J-C, Tamisier R, et aL Impaired objeetive daytime vigilance in obesity-hypoventilation syndrcnne impact of non-invasive ventilation. Chest 2007 131 148-155. 

In a recent study, 25 patients with ALS became dependent on NIPPV, including 13 who became continuously dependent for 19.7 16.9 months without developing acute respiratory distress or oxyhemoglobin desaturation. For another 76 patients, the daytime Sa02 baseline persistently decreased to <95%, 78 times because of some combination of alveolar hypoventilation and airway congestion. For 41 patients, the baseline was corrected by some combination of NIPPV and MAC for 11.1 8.7 months before desaturation recurred in 27. Of the latter, 11 underwent tracheostomy, 14 died in less than two months, and two were again corrected by the addition of MAC to NIPPV. Thirty-three of the 35 patients for whom the Sac>2 could not be normalized required tracheostomy or died within two months. The difference between the patients who could be spared respiratory... 

The most accepted indication for NPPV is diurnal hypercapnia in a stable state because it is the signature of overt ventilatory failure. Most recommendations concern patients with NMD and, in particular, patients with Duchenne muscular dystrophy in whom ventilatory support should be considered when daytime Paco2 exceeds 6 kPa (45 mmHg) (23-27). No guidelines or recommendations are available for the other causes of hypoventilation such as OSA or CF, but it seems reasonable to also consider diurnal hypercapnia as a criterion to propose NPPV in these patients. 

Most children are managed with NPPV (1,50). However, some require invasive ventilation through a tracheostomy. The main indications for a tracheostomy in children are airway abnormalities such as tracheobronchomalacia or tracheal stenosis, chronic disease of prematurity, and NMD (1,51,52). The indications for a tracheostomy are comparable to those of the adult population. They include the persistence of hypercapnia despite NPPV and additional measures such as daytime mouthpiece ventilation, aspiration, and bulbar dysfunction (53). In children, NPPV is more difficult to perform in those who might be 24-hour dependent, than in adults. Infants with primaiy alveolar hypoventilation (Ondine s curse) are preferentially ventilated by means of a tracheostomy (18). Tracheostomy ventilation favors airway inflammation (54) and may affect speech and language development (55). In children with progressive NMD, the decision of a tracheostomy has to be discussed on an individual basis, taking into account the familial environment and the parent s and child s perspective (52,56). In any case, sending children home with invasive ventilation is more difficult than when noninvasive ventilation is used (52). 

In the case of a 62-year-old woman with bilateral carotid body paraganglioma (19) and central alveolar hypoventilation—who received mechanical ventilation in 1990 with negative pressure through a poncho wrap and subsequently NIPPV through a nasal mask— two months after treatment symptoms, signs of right ventricular failure and daytime blood gases all improved. She has successfully been ventilated for 16 years. 

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