Use of Bioimpedance to Assess Changes in Hemodynamics During Acute Administration of CPAP

Abstract

BackgroundAttempts to investigate the mechanisms by which continuous positive airway pressure (CPAP) therapy improves heart function in patients with obstructive sleep apnea (OSA) have been limited by the lack of non-invasive methods to assess cardiac performance. We used transthoracic electrical bioimpedance (TEB) to assess acute hemodynamic changes including heart rate (HR), stroke volume (SV), cardiac output (CO) and cardiac index (CI) during PAP titration in (1) post-operative cardiac surgery patients, (2) patients with severe OSA, and (3) normal healthy volunteers.MethodsPost-operative cardiac surgery patients were studied via TEB and pulmonary artery catheter (PAC) during acute titration of positive end-expiratory pressure (PEEP) while mechanically ventilated. Patients with severe OSA were studied non-invasively by TEB during acute CPAP titration in supine stage 2 sleep, and normal subjects while awake and recumbent.ResultsIn post-operative cardiac surgery patients (n = 3), increasing PEEP to 18 cmH2O significantly reduced SV and CI relative to baseline. There was no difference between TEB and PAC in terms of ability to assess variations in hemodynamic parameters. In patients with severe OSA (n = 3), CPAP titration to optimal pressure to alleviate obstructive apneas reduced HR, SV, CO and CI significantly compared to without CPAP. In three healthy subjects, maximal tolerated CPAP reduced SV and CO significantly compared to baseline.ConclusionsAcute administration of CPAP causes a decrease in CO and CI, apparently a consequence of a reduction in SV. TEB appears to be an accurate and reproducible non-invasive method of detecting changes in hemodynamics.

Model-based stability assessment of ventilatory control in overweight adolescents with obstructive sleep apnea during NREM sleep

“…Cardiac output was not measured during the experiment, but it is unlikely that there was a systematic difference between the two subject groups given their young age. Any change in cardiac output resulting from CPAP was likely to be comparable in both groups, considering that therapeutic CPAP was similar in both groups (see Table 1) (20,31). Pulmonary function tests revealed that there was no significant differ- ence in vital capacity (VC) or in functional residual capacity (FRC) between the groups (see Table 2), discarding the possibility that increased PG was associated with low lung volumes.…”

Sleep Apnea and Atrial Fibrillation; 2012 Update

“…Even the acute administration of CPAP may have profound cardiovascular effects. Several studies have reported that acute CPAP administration decreases stroke volume and cardiac output in patients with CHF and OSA [ 71 , 72 ], and one recent study found similar decreases in stroke volume and cardiac output in a range of patients including OSA patients without CHF, post-operative cardiac surgery patients, as well as healthy volunteers [ 73 ]. However, these findings have not been consistently reported [ 74 , 75 ] and the acute cardiovascular effects of CPAP are not fully understood.…”