[Sleep apnea syndrome as cause and consequence of congestive heart failure]

Comparison of Carbon Dioxide Rebreathing During Application of Continuous Positive Airway Pressure With 3 Types of Nasal Mask

A comparison is made between the end-tidal fractional concentration of carbon dioxide (FETCO2) obtained during application of varying levels of continuous positive airway pressure (CPAP) with a prototype mask (from Carburos Metálicos) and FETCO2 obtained with 2 commonly used nasal masks (Profile Lite and ComfortClassic from Respironics). The nasal FETCO2 was measured on 3 consecutive days in 11 healthy volunteers, 12 patients with severe obstructive sleep apnea-hypopnea syndrome, and 12 hypercapnic patients. A different mask was randomly assigned on each day and the FETCO2 was measured after 3 minutes of CPAP at 4, 5, 6, 8, 10, 15, and 20 cm H2O. Although in all cases a progressive reduction in FETCO2 was observed with increasing CPAP, the effect was greatest with the prototype mask at all pressures. In the 3 different study groups the pressures obtained with the prototype mask were similar to those generated by the CPAP machine. In conclusion, the lower concentration of nasal CO2 obtained using the prototype mask suggests that it causes less rebreathing.

[Determining cardiac output by carbon dioxide rebreathing in patients with sleep apnea-hypopnea syndrome]

The objective of the present study was to determine the relation between resting cardiac output in patients with sleep apnea-hypopnea syndrome but without arterial hypertension or heart failure as measured indirectly by the carbon dioxide rebreathing method and left ventricular function evaluated by transthoracic echocardiography. We also compared the variability and reproducibility of the measurements obtained by the equilibrium and exponential methods. In patients with sleep apnea-hypopnea syndrome there was a modest but significant association between resting cardiac output and left ventricular shortening fraction (r=0.690; P<.001) and left ventricular ejection fraction (r=0.690; P<.001). In addition, mean (SD) cardiac output obtained by the equilibrium method showed a lower coefficient of variability (0.21 [0.08]) than that of the exponential method (0.16 [0.09]) (P<.01) as well as a narrower reproducibility interval.

Factores que influyen en el síndrome de apneas-hipopneas durante el sueño

BACKGROUND AND OBJECTIVE

Evaluate the influence of some variables (gender, age, alcohol intake and obesity) on the apnea/hypopnea index (AHI) in patients with sleep apnea/hypopnea syndrome (SAHS).

PATIENTS AND METHOD

We retrospectively reviewed medical records of patients with SAHS in the Hospital General Universitario of Murcia. We assessed demographic variables, alcohol intake, Epworth's scale, obesity and cardiorespiratory polygraphy or polysomnography. A multivariate regression model was used to explain the AHI in relation with other variables.

RESULTS

We reviewed 127 medical records of patients with SAHS. Alcohol intake was the most powerful variable influencing the AHI, followed by the numeric value of the Epworth's Scale. No statistical significance was found with regard to the the rest of variables.

CONCLUSIONS

In patients with SAHS, the AHI can be related to the alcohol intake and the numeric value of Epworth's Scale.