Chest
Volume 89, Issue 5, May 1986, Pages 627-635
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Clinical Investigations
Hypercapnia in the Obstructive Sleep Apnea Syndrome: A Reevaluation of the “Pickwickian Syndrome”

https://doi.org/10.1378/chest.89.5.627Get rights and content

The mechanisms of hypercapnia in eight patients with the “Pickwickian” syndrome and obstructive sleep apnea (OSAS) were evaluated pretherapy and posttherapy (tracheostomy in seven patients and chronic nocturnal use of nasal CPAP in one). Four patients (correctors) became eucapnic within two weeks of therapy. Four others (noncorrectors) remained hypercapnic. Neither residual apneas, changes in pulmonary function, change in anatomic dead space, nor changes in ventilatory chemoresponsiveness differentiated the two groups, nor did the last three factors account for return to eucapnia in the correctors. The results indicated two separate mechanisms exist for chronic hypercapnia in OSAS: 1) a critical balance between the ventilation during the time spent awake and hypoventilation due to apneas, a mechanism removed by treatment for obstructive apnea; and 2) sustained hypoventilation independent of the apnea phenomenon and therefore not correctible. The subset of patients with the second mechanism appears to represent the true “Pickwickian” syndrome and can be identified before therapy by measuring a low level of ventilation in the sustained awake state.

Section snippets

Methods

Eight chronically hypercapnic patients with obstructive sleep apnea syndrome were evaluated before and after therapy for their apneas. Therapy consisted of permanent tracheostomy in seven patients; one patient was successfully treated with nightly use of a nasal mask which delivered continuous positive airway pressure (nasal CPAP). In each case, the patient was able to reduce his arterial Pco2 below 40 mm Hg by voluntary hyperventilation. All patients were obese and hypersomnolent. Six of the

Results

Table 1 lists anthropometric data and arterial blood gas levels of the patients before treatment, establishing the degree of chronic hypercapnia. Data from the pretreatment all-night sleep studies are also shown, documenting that each patient had severe obstructive sleep apnea.

Tracheostomy and nasal CPAP resulted in relief of hypersomnolence and disappearance of snoring in all cases. Peripheral edema disappeared or decreased in those in whom it was present.

Sleep pattern before treatment was

Discussion

In the present study, tracheostomy or chronic nocturnal use of nasal CPAP produced complete correction of the obstructive sleep apnea syndrome in all eight hypercapnic patients. However, correction of the chronic hypercapnia occurred in only four of the eight. The association of chronic hypercapnia with obstructive sleep apnea is now well recognized,6 and a variable response of this hypercapnia after correction of the upper airway obstruction has been observed by others.14, 15, 16

Possible

References (18)

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This study was supported by grants from the National Institutes of Health, Division of Research Resources RR 96 and from the New York Lung Association.

Manuscript received September 16; revision accepted November 21.

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