Timo Leppänen

Novel parameters reflect changes in morphology of respiratory events during weight loss

Apnea-hypopnea-index (AHI), disregarding the respiratory event morphology, is currently used in estimation of severity of obstructive sleep apnea (OSA). The purpose of the current study was to evaluate the potential of novel parameters in estimation of changes in severity of OSA during weight loss. Polygraphic data of 67 patients, 37 in the control (no weight loss) and 30 in the weight loss (>5%) groups was evaluated at baseline and after two year follow-up. Changes in the values of novel parameters, incorporating detailed information of respiratory event characteristics, were evaluated and compared with changes in AHI. The median AHI in the weight loss group decreased significantly during the follow-up. The number of shorter respiratory events decreased in the weight loss group, while the longer ones remained, increasing the median durations of the respiratory events by 20-62%. For this reason the decrease of the values of the novel parameters were smaller compared to AHI in the weight loss group. This suggests that the severity of OSA might not fall as linearly during weight loss as AHI suggests. Moreover, the novel parameters containing more detailed information on the morphology characteristics may provide valuable supplementary information for the assessment of the severity of OSA.

Length of Individual Apnea Events Is Increased by Supine Position and Modulated by Severity of Obstructive Sleep Apnea.

Positional obstructive sleep apnea (OSA) is common among OSA patients. In severe OSA, the obstruction events are longer in supine compared to nonsupine positions. Corresponding scientific information on mild and moderate OSA is lacking. We studied whether individual obstruction and desaturation event severity is increased in supine position in all OSA severity categories and whether the severity of individual events is linked to OSA severity categories. Polygraphic recordings of 2026 patients were retrospectively analyzed. The individual apnea, and hypopnea durations and desaturation event depth, duration, and area of 526 included patients were compared between supine and nonsupine positions in different OSA severity categories. Apnea events were 6.3%, 12.5%, and 11.1% longer (p < 0.001) in supine compared to nonsupine position in mild, moderate, and severe OSA categories, respectively. In moderate and severe OSA categories desaturation areas were 5.7% and 25.5% larger (p < 0.001) in supine position. In both positions the individual event severity was elevated along increasing OSA severity category (p < 0.05). Supine position elevates apnea duration in all and desaturation area in moderate and severe OSA severity categories. This might be more hazardous for supine OSA patients and therefore, estimation of clinical severity of OSA should incorporate also information about individual event characteristics besides AHI.

Amount of weight loss or gain influences the severity of respiratory events in sleep apnea

Abstract Severity of obstructive sleep apnea (OSA) is estimated based on respiratory events per hour [i.e., apnea–hypopnea index (AHI)]. The aim of this study was to investigate effects of weight change on the severity of respiratory events. Respiratory event severity, including duration and morphology, was estimated by determining parameters quantifying obstruction and desaturation event lengths and areas, respectively. Respiratory events of 54 OSA patients treated with dietary intervention were evaluated at baseline and after 5-year follow-up in subgroups with different levels of weight change. AHI, oxygen desaturation index (ODI) and obstruction event severities decreased during weight loss. In lower level weight loss, the decrease was milder in obstruction severity than in AHI and ODI, indicating that the decrease in the number of events is more focused on less severe events. In weight gain groups, parameters incorporating obstruction event severity, AHI and ODI increased, although increase was greater in parameters incorporating obstruction event severity. The number and severity of respiratory events were modulated differently by the level of weight change. AHI misses this change in the severity of respiratory events. Therefore, parameters incorporating information on the respiratory event severities may bring additional information on the health effects obtained with dietary treatment of OSA.

RemLogic plug-in enables clinical application of apnea-hypopnea index adjusted for severity of individual obstruction events.

Abstract Obstructive sleep apnea (OSA) is diagnosed based on obstruction event incidence, albeit individual obstruction event severity is connected to increased mortality rate. Adjusted-AHI parameter, incorporating number and severity of obstruction events, has shown good potential, but is calculated using custom-made MATLAB® functions. To allow its clinical use, this study introduces the RemLogic™ plug-in. It is tested comparing adjusted-AHI values calculated with the plug-in and MATLAB® with a hundred patients. Furthermore, retrospective follow-up (mean ± SD = 194.1 ± 54.0 months) of 1128 working-age men was conducted to evaluate potential of adjusted-AHI to enhance diagnostic of OSA. Adjusted-AHI values were strongly correlated (r = 1.000, p < 0.001) and their average difference (mean ± SD) was minimal (0.08 ± 0.19%). Using adjusted-AHI to define OSA severity resulted in a higher hazard ratio of mortality in the severe OSA group and, for the first time, adjusted-AHI was found to explain independently the overall mortality and non-fatal cardiovascular events. Importantly, the present plug-in enables clinical use of adjusted-AHI, enhancing assessment of OSA severity.

Simulation of Required CPAP Usage to Normalize AHI in Obstructive Sleep Apnea Patients

Obstructive sleep apnea (OSA) is a highly prevalent disease with severe health consequences. The severity of OSA is estimated with apnea-hypopnea-index (AHI). OSA is often treated with continuous positive airway pressure (CPAP). The aim of the current work was to create a numerical simulator showing benefits of different levels of usage of CPAP treatment. 226 male OSA patients were evaluated. CPAP treatment was simulated in 5 min intervals starting from the beginning of the night and continuing until the end. The cutoff point where AHI reached normal level of <5 events/h were determined for mild, moderate and severe OSA categories. We found a trend of increasing AHI towards the end of the night. The median values of required simulated CPAP usage times to normalize the AHI values (AHI < 5 events/h) were 3.9 h, 5.3 h and 6.2 h in the mild, moderate and severe OSA severity categories, respectively. CPAP treatment adherence can be limited in OSA patients due to several reasons. The presented CPAP treatment simulation tool could aid the clinicians to give patient specific recommendation to the OSA patients for required CPAP treatment times and to motivate the patients to higher adherence levels of the treatment. This could possibly better prevent the harmful health consequences related to OSA.

Differences in arousal probability and duration after apnea and hypopnea events in adult OSA patients

OBJECTIVE In obstructive sleep apnea (OSA), breathing cessations are often followed by arousals, leading to sleep fragmentation and thus impaired sleep quality. Arousals and fragmented sleep are also related to detrimental cardiovascular events. The key index for OSA diagnosis (i.e. the apnea-hypopnea index) attributes equal diagnostic value to apneas and hypopneas, despite the fact that the associated arousals and desaturations may be very different. Thus, considering the severity of the consequences of apneas and hypopneas could enhance the estimation of OSA severity. In this study, we investigate whether the probability and duration of apnea- and hypopnea-related arousals differ and whether the differences in desaturation severity following apneas and hypopneas are dependent on sleep stage. APPROACH Polysomnographic recordings of 348 consecutive OSA patients were included for analysis. The severity of arousals and desaturations associated with hypopneas within different sleep stages was compared to that of arousals and desaturations associated with apneas. In addition, the probability of arousals related to apneas and hypopneas was evaluated within OSA severity categories. MAIN RESULTS Apneas caused arousals less frequently than hypopneas in N1, N2, and N3 sleep in all OSA severity categories. However, the arousals caused by apneas were longer (p  <  0.001) and the desaturations related to apneas were more severe (p  <  0.001) than those related to hypopneas in N1, N2, and rapid eye movement sleep even after adjustment for respiratory event durations. SIGNIFICANCE Desaturations and arousals related to apneas are more severe than those related to hypopneas. Therefore, apneas followed by arousal or desaturation should have a different diagnostic value than hypopneas when assessing OSA severity and related risk for cardiovascular consequences.

F25. Intranight variability of AHI can affect the efficiency of CPAP treatment

Introduction Obstructive sleep apnea (OSA) is a common disease with severe health consequences most commonly treated with continuous positive airway pressure (CPAP) device. However, the adherence to CPAP treatment is often limited and the usage of the CPAP device can be only around 4 h per night after 1 month usage ( Chai-Coetzer et al., 2013 ). Possibly for this reason the benefits of the CPAP usage in terms of cardiovascular outcomes are not always obvious ( McEvoy et al., 2016 ). The severity of OSA is estimated with apnea-hypopnea-index (AHI) together with daytime symptoms. AHI may vary hour by hour during the night. In the current study, the aim was to investigate whether there is a difference in AHI during the first 4 h of sleep (possible CPAP adherence) and during the worst 4 h during the night. Methods 2002 ambulatory polygraphic recordings of suspected OSA patients were evaluated. The patients were divided into normal, mild, moderate and severe OSA categories based on their total AHI. Total AHI, AHI during the first 4 h and AHI during the worst 4 h during the recording were analyzed. AHI during the first and the worst 4 h were then compared. Wilcoxon signed ranks test was used to estimate the statistical significance of the differences. p Results There were 972, 508, 260 and 262 patients in normal, mild, moderate and severe OSA categories, respectively. We found a trend of increasing AHI towards the end of the night. The median total AHI in these categories were 1.5, 8.7, 20.7 and 47.6 events/h, respectively. The median differences between the AHI during the worst 4 h and the first 4 h of the recording were 0.8, 4.8, 10.4 and 9.8 events/h ( p Conclusion There were statistically and clinically significant differences between the median AHI values of the worst 4 h and the first 4 h of the night in all OSA severity categories. CPAP adherence has been reported to be around 4 h per night ( Chai-Coetzer et al., 2013 ) and the CPAP usage is probably typically focused on the first hours from the beginning of the night. For these reasons the benefits of the CPAP usage are probably not as linear as the simple time of adherence indicates. With limited adherence time, CPAP treatment is not always able to prevent severe cardiovascular outcomes ( McEvoy et al., 2016 ). If the CPAP usage could be directed to the worst hours of the night at the same adherence level it might provide better treatment results. The total AHI would decrease more when CPAP would be used during the worst hours instead the first hours of the night.

Desaturation event characteristics and mortality risk in severe sleep apnea

Obstructive sleep apnea (OSA) is a public health problem with severe health consequences. The current OSA severity estimation is based on the average number of breathing cessation and desaturation events per hour of sleep, neglecting the individual event characteristics. The aim of the current study was to evaluate desaturation event morphology in de- ceased and matched control patients with severe OSA. 12 deceased and 12 AHI, age, BMI and follow-up time matched alive control patients with severe OSA were analyzed. Desaturation event durations, depths, and areas of the deceased and alive control patients were compared. Also the effect of different baseline level selection in the desaturation depth analysis was investigated. Patient demographics, apnea-hypopnea-index (AHI) and oxygen-desaturation-index (ODI) did not differ statistically significantly between the groups. The average oxygen saturation levels were statistically significantly lower 89.8% vs. 93.2% ( p =0.002) in the deceased patients compared to the alive controls. The median desaturation event duration 31.8s vs. 25.9s ( p =0.017), depth 15.0% vs. 9.5% ( p =0.006) and area 349.9s% vs. 201.4s% ( p<S0.001) were statistically significantly greater in the deceased patients compared to the alive control patients when using 100% saturation as baseline level for desaturation events. When the first point before desaturation onset was used as baseline no statistically significant differences ( p =0.089) were found between the deceased and alive control patients in desaturation depths. Based on quantitative inspection of the distributions of individual desaturation event characteristics the desaturation events were more severe in the deceased group. Patients with similar AHI and ODI can have different individual desaturation event characteristics. Selection of the baseline for desaturation event depth analysis can affect the estimation of the event severity. The analysis of the individual desaturation event characteristics can provide supplementary information on the severity estimation of OSA and support the individual mortality risk estimation in severe OSA patients.