[Constancy of the nCPAP pressure values in the long-term monitoring of patients with obstructive sleep apnea]

Spike protein of SARS-CoV-2 variants: a brief review and practical implications

The scientific community has been alarmed by the possible immunological evasion, higher infectivity, and severity of disease caused by the newest variants of SARS-CoV-2. The spike protein has an important role in the cellular invasion of viruses and is the target of several vaccines and therapeutic resources, such as monoclonal antibodies. In addition, some of the most relevant mutations in the different variants are on the spike (S) protein gene sequence that leads to structural alterations in the predicted protein, thus causing concern about the protection mediated by vaccines against these new strains. The present review highlights the most recent knowledge about COVID-19 and vaccines, emphasizing the different spike protein structures of SARS-CoV-2 and updating the reader about the emerging viral variants and their classifications, the more common viral mutations described and their distribution in Brazil. It also compiles a table with the most recent knowledge about all of the Omicron spike mutations.

Longitudinal analysis of antibody dynamics in COVID-19 convalescents reveals neutralizing responses up to 16 months after infection

Elucidating the dynamics of the neutralizing antibody (nAb) response in coronavirus disease 2019 (COVID-19) convalescents is crucial in controlling the pandemic and informing vaccination strategies. Here we measured nAb titres across 411 sequential plasma samples collected during 1-480 d after illness onset or laboratory confirmation (d.a.o.) from 214 COVID-19 convalescents, covering the clinical spectrum of disease and without additional exposure history after recovery or vaccination against SARS-CoV-2, using authentic SARS-CoV-2 microneutralization (MN) assays. Forty-eight samples were also tested for neutralizing activities against the circulating variants using pseudotyped neutralization assay. Results showed that anti-RBD IgG and MN titres peaked at ~120 d.a.o. and subsequently declined, with significantly reduced nAb responses found in 91.67% of COVID-19 convalescents (≥50% decrease in current MN titres compared with the paired peak MN titres). Despite this decline, majority of the COVID-19 convalescents maintained detectable anti-RBD IgG and MN titres at 400-480 d.a.o., with undetectable neutralizing activity found in 14.41% (16/111) of the mild and 50% (5/10) of the asymptomatic infections at 330-480 d.a.o. Persistent antibody-dependent immunity could provide protection against circulating variants after one year, despite significantly decreased neutralizing activities against Beta, Delta and Mu variants. In conclusion, these data show that despite a marked decline in neutralizing activity over time, nAb responses persist for up to 480 d in most convalescents of symptomatic COVID-19, whereas a high rate of undetectable nAb responses was found in convalescents from asymptomatic infections.

A new predictive model for continuous positive airway pressure in the treatment of obstructive sleep apnea

BACKGROUND

Numerous mathematical formulas have been developed to determine continuous positive airway pressure (CPAP) without an in-laboratory titration study. Recent studies have shown that style of CPAP mask can affect the optimal pressure requirement. However, none of the current models take mask style into account. Therefore, the goal of this study was to develop new predictive models of CPAP that take into account the style of mask interface.

METHODS

Data from 200 subjects with attended CPAP titrations during overnight polysomnograms using nasal masks and 132 subjects using oronasal masks were randomized and split into either a model development or validation group. Predictive models were then created in each model development group and the accuracy of the models was then tested in the model validation groups.

RESULTS

The correlation between our new oronasal model and laboratory determined optimal CPAP was significant, r = 0.61, p < 0.001. Our nasal formula was also significantly related to laboratory determined optimal CPAP, r = 0.35, p < 0.001. The oronasal model created in our study significantly outperformed the original CPAP predictive model developed by Miljeteig and Hoffstein, z = 1.99, p < 0.05. The predictive performance of our new nasal model did not differ significantly from Miljeteig and Hoffstein's original model, z = -0.16, p < 0.90. The best predictors for the nasal mask group were AHI, lowest SaO2, and neck size, whereas the top predictors in the oronasal group were AHI and lowest SaO2.

CONCLUSION

Our data show that predictive models of CPAP that take into account mask style can significantly improve the formula's accuracy. Most of the past models likely focused on model development with nasal masks (mask style used for model development was not typically reported in previous investigations) and are not well suited for patients using an oronasal interface. Our new oronasal CPAP prediction equation produced significantly improved performance compared to the well-known Miljeteig and Hoffstein formula in patients titrated on CPAP with an oronasal mask and was also significantly related to laboratory determined optimal CPAP.

Multinight recording and analysis of continuous positive airway pressure airflow in the home for titration and management of sleep disordered breathing

OBJECTIVES

The authors examined magnitude/variability of residual sleep disordered breathing (SDB) at pressures around the therapeutic continuous positive airway pressure (CPAP), and described a multinight approach to CPAP titration/retitration consisting of recording airflow and summarizing SDB over multiple nights at multiple pressures and choosing an optimal pressure from these summarized data.

DESIGN

Prospective, single-center nonblinded study.

PATIENTS

Ten female/18 male patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) (respiratory disturbance index [RDI] 67/h), 17 newly-initiated, 11 chronic CPAP users.

INTERVENTIONS

A custom CPAP device (Fisher & Paykel Healthcare) recording airflow and pre-programmed to vary CPAP between 2-3 cm H2O below and 1-2 cm H2O above prescription pressure as determined by a full laboratory titration.

RESULTS

Airflow and pressure continuously recorded for multiple nights (15.9 ± 5.1 nights) at four to seven different pressures in each patient. SDB events manually scored from the airflow as apnea (airflow reduction > 90%), hypopnea (airflow reduction > 30% lasting 10 to 120 sec with inspira-tory flow limitation [IFL]) and runs of sustained IFL > 2 min identified. RDI = (apnea + hypopnea)/total sleep time calculated for each night and an obstruction index, including sustained IFL, also was calculated. PressureMultinight was obtained for each patient from multiple nights of data using two mathematical techniques. Night-to-night variability of SDB indices was low in some patients and significant in others. PressureMultinight could be determined in 17 of 28 patients and was similar to the in-laboratory pressure.

CONCLUSIONS

This study showed that recording multiple nights of CPAP airflow in the home and analyzing these data for residual SDB provided useful information, including the possibility of determining a therapeutic prescription for fixed CPAP in most patients and identification of others with significant physiologic variability of SDB.

The need for pressure changes in CPAP therapy 2-3 months after initial treatment: a prospective trial in 905 patients with sleep-disordered breathing

OBJECTIVE

The aim of the study was to investigate the need for pressure change in patients with sleep-disordered breathing (SDB) several weeks after therapy initiation. We prospectively studied 905 consecutive patients (740 men and 165 women) with SDB and therapeutic intervention with continuous positive airway pressure (CPAP)/bilevel PAP.

METHODS

Several weeks after therapy initiation, patients were restudied for control, and pressure was optimized if it was necessary. The differences in CPAP pressure from initial treatment and control night were assessed. Anthropometric data, polysomnography data, Epworth sleepiness scale, and Berlin questionnaire scores were correlated to pressure differences from the first and control titration nights.

RESULTS

Pressure change was needed in 511 patients (58.2%). Pressure increase was more frequent than pressure reduction (41.7% vs. 11.7%). Mean pressure increase in CPAP was 1.3 mbar, and mean decrease, 1.6 mbar. In the bilevel PAP group, the mean increase in inspiratory pressure was 1.2 mbar, and in expiratory pressure, 0.8 mbar; the mean decrease in inspiratory pressure was 1.9 mbar, and in expiratory pressure, 1.4 mbar. No correlation was found between anthropometric data, sleep efficacy, the amount of rapid eye movement sleep per night, or questionnaire scores and pressure change.

CONCLUSION

Our results show that pressure changes are necessary in the majority of patients several weeks after therapy initiation. Therefore, re-evaluation of therapy pressure is useful.

Use of conventional and self-adjusting nasal continuous positive airway pressure for treatment of severe obstructive sleep apnea syndrome: a comparative study

STUDY OBJECTIVES

To compare conventional and self-adjusting nasal continuous positive airway pressure (nCPAP) therapy in patients with severe obstructive sleep apnea syndrome with respect to suppression of respiratory disturbances, quality of sleep, mean mask pressure, and patient compliance.

DESIGN

Cohort study of consecutive patients with obstructive sleep apnea syndrome, single-blinded.

SETTING

Clinical sleep laboratory in Germany.

PATIENTS

Fifty patients (44 men, 6 women who ranged in age from 35 to 71 years) with polysomnographically confirmed severe obstructive sleep apnea syndrome (respiratory disturbance index [RDI], >20/h).

MEASUREMENTS AND INTERVENTIONS

After baseline polysomnography, patients were randomly treated with nCPAP either in conventional (group 1) or in automatically adjusting (group 2) mode. Three to 6 months after adjustment, all patients underwent polysomnography again. They also were examined with a portable monitoring device and received a questionnaire on subjective well-being and device evaluation.

RESULTS

Anthropometric and respiratory data were comparable in both groups; body mass index had not changed significantly in the follow-up. RDI dropped by 91.5% (from 38.3+/- 13.9/h to 3.6+/-4.4/h) in conventional and by 93.6% (from 35.5+/-9.6/h to 2.4+/-1.6/h) in self-adjusting mode (statistically not significant [NS]). Sleep efficiency decreased by 4.0% in conventional and increased by 2.0% in self-adjusting mode (NS). In both groups, normal sleep structure was largely restored. Mean mask pressure was 8.1+/-2.5 cm H2O in group 1 and 6.5+/-1.7 cm H2O in group 2 (p<0.01). Patient compliance in terms of nights per week of mask appliance was better in the self-adjusting mode (5.7+/-0.7 to 6.5+/-0.4; p<0.01).

CONCLUSION

Self-adjusting nCPAP demonstrates the same reliability in suppression of respiratory disturbances as fixed-mask pressure therapy. Sleep quality is slightly superior, patient compliance is highly significantly better.