Validation of respiratory inductive plethysmography (LifeShirt) in obesity hypoventilation syndrome.

Validation of respiratory inductive plethysmography (LifeShirt system) (RIPLS) for tidal volume (VT), minute ventilation (V˙E), and respiratory frequency (fB) was performed among people with untreated obesity hypoventilation syndrome (OHS) and controls. Measures were obtained simultaneously from RIPLS and a spirometer during two tests, and compared using Bland Altman analysis. Among 13 OHS participants (162 paired measures), RIPLS-spirometer agreement was unacceptable for VT: mean difference (MD) 3 mL (1%); limits of agreement (LOA) -216 to 220 mL (±36%); V˙E MD 0.1 L min(-1) (2%); LOA -4.1 to 4.3 L min(-1) (±36%); and fB: MD 0.2 br min(-1) (2%); LOA -4.6 to 5.0 br min(-1) (±27%). Among 13 controls (197 paired measures), RIPLS-spirometer agreement was acceptable for fB: MD -0.1 br min(-1) (-1%); LOA -1.2 to 1.1 br min(-1) (±12%), but unacceptable for VT: MD 5 mL (1%); LOA -160 to 169 mL (±20%) and V˙E: MD 0.1 L min(-1) (1%); LOA -1.4 to 1.5 L min(-1) (±20%). RIPLS produces valid measures of fB among controls but not OHS patients, and is not valid for quantifying respiratory volumes among either group.

Validity of arterialised-venous P CO2, pH and bicarbonate in obesity hypoventilation syndrome.

This prospective study investigated the validity of arterialised-venous blood gases (AVBG) for estimating arterial carbon dioxide P CO2, pH and bicarbonate (HCO3(-)) in people with obesity hypoventilation syndrome (OHS). AVBGs were obtained from an upper limb vein, after heating the skin at 42-46°C. Arterial blood gas (ABG) and AVBG samples were taken simultaneously and compared using Bland Altman analysis. Between-group differences were assessed with independent t-tests or Mann-Whitney U tests. Forty-two viable paired samples were analysed, including 27 paired samples from 15 OHS participants, and 15 paired samples from 16 controls. AVBG-ABG agreement was not different between groups, or between dorsal hand, forearm and antecubital AVBG sampling sites, and was clinically acceptable for P Co2: mean difference (MD) 0.4 mmHg (0.9%), limits of agreement (LOA) -2.7-3.6 mmHg (± 6.6%); pH: MD -0.008 (-0.1%), LOA -0.023-0.008 (± 0.2%); and HCO3(-): MD -0.3 mmol L(-1) (-1.0%), LOA -1.8-1.2 mmol L(-1) (± 5.3%). AVBG provides valid measures of [Formula: see text] , pH, and HCO3(-) in OHS.

Electroencephalographic arousals during sleep do not alter the pressor response to Cheyne-Stokes respiration in subjects with chronic heart failure.

This study examined the influence of electroencephalographic (EEG) arousal on the magnitude and morphology of the pressor response to Cheyne-Stokes respiration (CSR) in subjects with congestive heart failure (CHF). Thirteen subjects with stable CHF (left ventricular ejection fraction, 26 +/- 7%) and CSR (apnea-hypopnea index 52 +/- 15 h(-1)) underwent overnight polysomnography with beat-to-beat measurement of systemic arterial blood pressure (BP). CSR events were divided into those with or without an EEG arousal defined according to the criteria of the American Sleep Disorders Association. The pressor response was quantified in terms of the delta BP change (difference between the minimum BP during apnea and maximum BP during hyperpnea). Changes in the morphology of the pressor response were assessed by subdividing individual respiratory events into six periods (three during apnea: A1, A2, A3; and three during hyperpnea: H1, H2, H3). Considerable fluctuations in BP and heart rate (HR) were observed across the CSR cycle (delta mean BP 20.2 +/- 6.5 mmHg). The presence of an EEG arousal did not alter the amplitude of fluctuations in BP. Mean blood pressure (MBP) increased 21.0 +/- 7.5 mmHg with arousal versus 19.3 +/- 5.8 mmHg without arousal (NS). A repeated measures ANOVA showed no significant interaction between the presence of arousal and the proportional change in mean BP across the six periods, indicating that an EEG arousal had no effect on the morphology of MBP change during CSR [F(5,60) = 1.44, P = 0.22]. This study showed that EEG-defined arousal does not amplify the pressor response to CSR in CHF.

Night-to-night variability in sleep in cystic fibrosis.

OBJECTIVES: The impact of night-to-night variability (NNV) on polysomnography (PSG) has been reported mainly in normal subjects, the elderly and patients with obstructive sleep apnea with focus on changes in the apnea/hypopnea index, rather than measures of nocturnal oxygenation. There is very limited data on NNV in patients with cystic fibrosis (CF). The goal of this study was to assess for first-night effect and reliability of PSG measurements on nocturnal oxygenation and respiratory disturbance in CF. METHODS: A prospective observational study was performed in patients with CF who consented to PSG on two consecutive nights. Paired t-tests and intra-class correlation coefficients (ICCs) were calculated for repeated measures of sleep stage time, sleep efficiency, arousal indices, measures of nocturnal oxygenation, and respiratory events in all sleep stages. RESULTS: Thirty-one patients with CF were studied, aged 27+/-8 (mean+/-1 SD) years and forced expiratory volume in 1 s (FEV(1)) of 37+/-11% of predicted. Relative to the first-night PSG, on the second PSG, we observed the following: shorter latency to rapid eye movement (REM) sleep (P<0.001), increased sleep efficiency (P<0.01), decreased wake after sleep onset (WASO) time (P<0.01), decreased percentage of non-REM time with oxyhemoglobin saturation by pulse oximetry (SpO(2))< or =90% (P<0.05), decreased number of central apneas per hour (P<0.05) and reduced respiratory rate in stage 2 sleep on night 2 (P<0.05). Despite these changes, the ICCs between night 1 and night 2 showed good repeatability/reliability for measures of nocturnal oxygenation and indices of respiratory disturbance, including the percentage of total sleep time with SpO(2)< or =90% (ICC=0.85) and apnea-hypopnea index (ICC=0.75). Likewise, the ICCs were extremely high for respiratory rate in stage 2 (ICC=0.94), slow wave sleep (ICC=0.97), and REM sleep (ICC=0.96). CONCLUSION: Although a first-night effect is seen with sleep efficiency, REM latency, and WASO, a single-night PSG in patients with CF yields reliable information on nocturnal oxygenation and respiratory disturbance.