meditation objectives: The mechanism(s) by which nasal continuous positive airway urgency (CPAP) is effective in the treatment of Cheyne-Stokes respiration (CSR) in patients with congestive heart failure (CHF) remains uncertain.

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meditation objectives: The mechanism(s) by which nasal continuous positive airway urgency (CPAP) is effective in the treatment of Cheyne-Stokes respiration (CSR) in patients with congestive heart failure (CHF) remains uncertain, and may involve an increase in total oxygen corpse stores (dampening), changes in central and peripheral controller gain, and/or improvement in cardiac function. The sense of this study was to evaluate the consequences of nasal CPAP on total oxygen stores, as measured through the rate of fall of arterial oxyhemoglobin saturation (dSa[O.sub.2]/dt), to determine if dampening may play a part in the attenuation of CSR in patients with CHF

Design: Prospective controll trial.

Setting: University hospital.

Patients: Nine male patients (mean [+ or -] SD age, 59 [+ or -] 8 years) with CHF and a mean left ventricular ejection fraction (LVEF) of 16 [+ or -] 4%



Interventions and measurements: All patients had known CSR as identified in succession a baseline polysomnographic study. Patients then underwent repeat polysomnography while receiving nasal CPAP (9 [+ or -] 03 cm [Hsub2]O) The polysomnography consisted of recording of breathing pattern, vibration oximetry, and EEG. dSa[O.sub.2]/dt was measured as the acclivity [i]or[/i] declivity of a line drawn adjacent to the falling linear portion of the arterial oxygen saturation (Sa[O.sub.2]) 1 associated with a central apnea. All patients underwent echocardiography and right-heart catheterization within 1 month of the subject of attention to measure LVEF and cardiac hemodynamics, respectively.

Results: There was a significant decrease in the apnea-hypopnea index (AHI) with nasal CPAP, from 44 [+ or -] 27 incidents per hour at baseline to 15 [+ or -] 24 incidents per hour with nasal CPAP (p = 0004) When compared to baseline, dSa[O.sub.2]/dt significantly decreased with nasal CPAP from 042 [+ or -] 015% to 020 [+ or -] 007%/ (p < 0001) The postapneic Sa[O.sub.2], when compared to baseline, significantly increased with nasal CPAP, from 87 [+ or -] 5% to 91 [+ or -] 4% (p < 005) The preapneic Sa[O.sub.2] did not significantly change, from a baseline of 96 [+ or -] 2% to 96 [+ or -] 3% with nasal CPAP (p = 08) When compared to baseline, the apnea duration and heart rate did not change with nasal CPAP. While there was a significant correlation noted between baseline postapneic Sa[O.sub.2] and dSa[O.sub.2]/dt (r = 08 p = 002) no correlation was seen between baseline preapneic Sa[O.sub.2] and dSa[O.sub.2]/dt (r = 01 p = 07) A significant correlation was noted between baseline dSa[O.sub.2]/dt and the AHI (r = 07 p = 002) With CPAP, there was a significant correlation noted between dSa[O.sub.2]/dt and the AHI (R = 07 p = 004) nevertheless no correlation was noted between dSa[O.sub.2]/dt and postapneic Sa[O.sub.2] (R = 01 p = 08)

Conclusion: Nasal CPAP significantly decreases dSa[O.sub.2]/dt and thus increases total corpse oxygen stores in patients with CSR and CHF by way of increasing oxygen body stores, dampening may be single of the mechanisms responsible for the attenuation of CSR seen with nasal CPAP.

solution words: Cheyne-Stokes respiration; congestive heart failure; dampening; nasal continuous positive airway pressure

Abbreviations: AHI = apnea-hypopnea index; BMI =body mass index. CHF=congestive heart failure; CPAP = continuous positive airway pressure; CSR = Cheyne-Stokes respiration; dSa[O.sub.2]/dt = rate of fall of arterial oxyhemoglobin saturation; FRC = functional residual volume; LVEF = left ventricular ejection fraction; Sa[O.sub.2] = arterial oxygen saturation; Sv[Osub2] = mixed venous oxygen saturation; TST = total slumber time; V[O.sub.2] = oxygen consumption

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Approximately 45 to 56% of patients with congestive heart failure (CHF) and a left ventricular ejection fraction (LVEF) of < 45% have Cheyne-Stokes respiration (CSR) during slumber (1-4) Characterized by a crescendo-decrescendo alteration in tidal bulk separated by periods of apnea or hypopnea, CSR has been associated with an increased mortality in patients with CHF (256) We have demonstrated that nasal continuous positive airway crushing (CPAP) and oxygen therapy were equally effective at decreasing the apnea-hypopnea index (AHI) in patients with CSR and CHF (4) still the mechanism(s) by which these treatment modalities improve CSR is uncertain and may involve increasing total material part oxygen stores (dampening), changes in central and peripheral controller gain, and/or improvement in cardiac function. In particular, it has been glance ated that nasal CPAP is effective by way of decreasing interstitial edema and pulmonary vagal afferent stimulation, resulting in a decrease in central and peripheral controller gain. (7-9) still an increased controller gain does not appear to be the single mechanism responsible, as not all patients with CHF and CSR demonstrate an increased sensitivity to C[Osub2] (1011)

Dampening consigns to the ability of the carcass to stabilize Pa[O.sub.2] and PaC[O.sub.2] during changes in ventilation. In patients with CHF interstitial edema causes a decrease in functional residual capacity (FRC) (12) leading to a decrease in total material part oxygen and C[O.sub.2] stores. As a eventuate the respiratory system becomes unstable (underdampened), with exaggerated changes in Pa[O.sub.2] and PaC[O.sub.2] during transient changes in ventilation. CSR can expand as a result of these changes in life-blood gas tensions.

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