Cardiorespiratory interaction with continuous positive airway pressure

Effects of continuous positive air pressure on intraocular pressure in patients with obstructive sleep apnea during the split-night study: An open-label randomized controlled trial

BACKGROUND

Intraocular pressure (IOP) is known to increase at midnight, when continuous positive airway pressure (CPAP) is initiated in split-night CPAP titration (SN-CPAP titration), in patients with obstructive sleep apnea (OSA); therefore, possible excessive increase in the IOP should be investigated. However, related studies on this topic are scarce. OSA causes increases and decreases in the IOP; however, its fluctuation during sleep remains unclear. Therefore, we determined the timing of these fluctuations in the IOP during sleep at night.

METHODS

This study included 25 patients with OSA. A 7-hour period of night sleep was divided into first (Sleep-1) and second halves (Sleep-2). Patients were randomly divided into the SN (natural breathing during Sleep-1, CPAP applied during Sleep-2) and C (without CPAP) groups. IOP was measured using the iCare Pro before Sleep-1 and after Sleep-1 and Sleep-2. The main hypothesis was that IOP would be significantly higher in the SN group than in the C group. The sub-hypothesis was that the effects of OSA on IOP are manifested at different times. The correlation is shown as Pearson's r for normally distributed data or Spearman's rho for non-normally distributed data. The difference between the SN and C groups in the time course of IOP during the night's sleep was analyzed using repeated-measures analysis of variance. A P value of <.05 was considered significant.

RESULTS

No significant difference was found in IOP between the groups, but the SN group showed a significantly increased IOP during Sleep-2 (post hoc Bonferroni test). The apnea-hypopnea index inversely correlated with IOP changes in Sleep-1 and positively correlated with those in Sleep-2.

CONCLUSION

This study does not support our main hypothesis that SN-CPAP titration promotes the effect of CPAP in increasing IOP. However, an expected range of the effect of increased CPAP on IOP has also been suggested. IOP-lowering and IOP-raising effects were predominant in the first and second halves of sleep in OSA, thereby providing a new perspective on measured IOP and supporting the subhypothesis.

A Bidirectional Association Between Obstructive Sleep Apnea and Metabolic-Associated Fatty Liver Disease

Obesity is considered a twentieth-century epidemic and is a growing concern among health professionals. Obesity and its complications contribute to multiple chronic illnesses, such as type 2 diabetes (T2D), metabolic syndrome, obstructive sleep apnea (OSA), malignancy, and cardiovascular and liver diseases. In the last two decades, a bidirectional association between OSA and metabolic-associated fatty liver disease (MAFLD), independent of obesity, has been established. Both conditions have similar risk factors and metabolic comorbidities that may imply a common disease pathway. This review compiles the evidence and delineates the relationship between OSA and MAFLD from a clinical and diagnostic aspect.

Should we treat with continuous positive airway pressure severe non-sleepy obstructive sleep apnea individuals without underlying cardiovascular disease?

The majority of the current international obstructive sleep apnea (OSA) guidelines base the recommendation to treat OSA with continuous positive airway pressure (CPAP) on the presence of symptoms (principally, albeit not exclusively on daytime hypersomnolence). In nonsleepy patients, even with severe OSA, controversies remain, as clear evidence supporting CPAP treatment of this subgroup of OSA patients is lacking. However, given the nonnegligible proportion of non-sleepy OSA patients, clinicians often face a serious dilemma since CPAP treatment in these patients may prove to be not cost-effective. Here, we propose a simple three-step-based algorithm that attempts to better phenotype non-sleepy OSA patients prior to reaching a CPAP treatment decision while also considering a series of clinically relevant elements in the process that may improve with CPAP therapy. Such algorithm focuses on the presence of several OSA symptoms that are susceptible to benefit from treatment and also relies on OSA phenotypes that need to be considered in an effort to achieve optimal cardiovascular prevention. Here, we attempt to establish a framework for clinicians who are evaluating severe nonsleepy OSA patients in their practices. However, the algorithm proposal needs to be extensively validated before being systematically implemented in clinical settings.

Prehospital noninvasive positive pressure ventilation for severe respiratory distress in adult patients: An updated meta-analysis

AIM

To compare the effect of prehospital noninvasive positive pressure ventilation (NIPPV) and standard care for severe respiratory distress.

BACKGROUND

Severe respiratory distress is an important cause of death in adult patients. There is a growing body of research exploring the benefits of nasal intermittent positive pressure ventilation (NIPPV) for patients undergoing severe respiratory distress. However, a systematic review is needed to synthesise and summarise this body of knowledge to identify the effectiveness of NIPPV. This is an update of a meta-analysis first published in 2014.

DESIGN

Meta-analysis based on PRISMA guidelines.

METHODS

Databases including PubMed, Embase, Scopus and the Cochrane Library databases were electronically searched to identify randomised controlled trials (RCTs) that reported NIPPV therapy for adult patients with severe respiratory distress. The retrieval time is limited from inception to August 2021. Two reviewers independently screened literature, extracted data and assessed risk bias of included studies. Meta-analysis was performed by using STATA 11.0 software.

RESULTS

A total of 10 studies involving 1465 patients were included. The meta-analysis results showed that compared with standard care, CPAP therapy decreased intubation rate (RR = 0.43, 95% CI: 0.27-0.67, p < .001, I²  = 0.0%), reduced hospital stay (WMD = -4.19, 95% CI: -5.62, -2.77) and ICU stay (WMD = -0.65, 95% CI: -1.09, -0.20) for patients with severe respiratory distress. However, no significant effects of NIPPV were observed on in-hospital mortality (RR = 0.83, 95% CI: 0.64-1.07) and ICU admission rate (RR = 0.93, 95% CI: 0.73-1.19).

CONCLUSIONS

Adult patients with NIPPV treatment for severe respiratory distress had a significantly lower intubation rate and shorter hospital and ICU stay, compared with those with standard care. However, no effect of NIPPV on in-hospital mortality was observed. Further study is needed by enrolling large-sample original studies.

RELEVANCE TO CLINICAL PRACTICE

Among patients with severe respiratory distress, prehospital NIPPV, compared with standard care, was associated with lower intubation rate and shorter hospital and ICU stay in our study. Although our meta-analysis did not find a relationship between prehospital NIPPV and in-hospital mortality and ICU admission rate, which may be limited by the number of studies included and the small sample size. However, our study still suggested that the use of prehospital NIPPV was beneficial to the condition of patients with severe respiratory distress.

ELMO, a new helmet interface for CPAP to treat COVID-19-related acute hypoxemic respiratory failure outside the ICU: a feasibility study

Objective:

To assess the feasibility of using a new helmet interface for CPAP, designated ELMO, to treat COVID-19-related acute hypoxemic respiratory failure (AHRF) outside the ICU.

Methods:

This was a proof-of-concept study involving patients with moderate to severe AHRF secondary to COVID-19 admitted to the general ward of a public hospital. The intervention consisted of applying CPAP via the ELMO interface integrated with oxygen and compressed air flow meters (30 L/min each) and a PEEP valve (CPAP levels = 8-10 cmH₂O), forming the ELMOcpap system. The patients were monitored for cardiorespiratory parameters, adverse events, and comfort.

Results:

Ten patients completed the study protocol. The ELMOcpap system was well tolerated, with no relevant adverse effects. Its use was feasible outside the ICU for a prolonged amount of time and was shown to be successful in 60% of the patients. A CPAP of 10 cmH₂O with a total gas flow of 56-60 L/min improved oxygenation after 30-to 60-min ELMOcpap sessions, allowing a significant decrease in estimated FIO₂ (p = 0.014) and an increase in estimated PaO₂/FIO₂ ratio (p = 0.008) within the first hour without CO₂ rebreathing.

Conclusions:

The use of ELMOcpap has proven to be feasible and effective in delivering high-flow CPAP to patients with COVID-19-related AHRF outside the ICU. There were no major adverse effects, and ELMO was considered comfortable. ELMOcpap sessions significantly improved oxygenation, reducing FIO₂ without CO₂ rebreathing. The overall success rate was 60% in this pilot study, and further clinical trials should be carried out in the future.

(ClinicalTrials.gov identifier: NCT04470258 [http://www.clinicaltrials.gov/])

Reversibility of retinochoroidal vascular alteration in patients with obstructive sleep apnea after continuous positive air pressure and surgical intervention

Purpose

The aim of this work was to study various retinochoroidal parameters in patients with obstructive sleep apnea syndrome (OSAS) and the effect of interventions on these parameters at 6 months follow-up.

Methods

A total of 36 patients were recruited prospectively from the otorhinolaryngology clinics of a large tertiary center between September 2018 to March 2020. The subjects were divided into three groups depending upon intervention chosen for OSAS: Group A (surgery, i.e., uvulopalatopharyngoplasty), group B (medical therapy, i.e., continuous positive air pressure) and group C (no intervention). Various retinochoroidal parameters which were studied included retinal thickness (RT), choroidal thickness (CT), choroidal vascularity index (CVI), arteriovenous ratio (AVR), capillary density index (CDI) in superficial and deep retina, at baseline and 6 months of follow-up after the intervention.

Results

In group A, CT increased significantly at 6 months (332.76 ± 86.41 um) compared to baseline (306.28 ± 78.19) (P = 0.0004). Similarly, CDI at both superficial and deep capillary plexus increased significantly at 6 months (superficial CDI: 0.65 ± 0.04, deep CDI: 0.38 ± 0.01) compared to baseline (superficial CDI: 0.62 ± 0.03, deep CDI: 0.36 ± 0.02) (P = 0.004 and 0.002 respectively). In group B, CT increased significantly at 6 months (361.38 ± 78.63 um) compared to baseline (324.21 ± 76.97 um) (P = 0.008). Also, CVI showed a significant decrease at 6 months (65.74 ± 1.84%) compared to baseline (67.36 ± 1.57%) (P = 0.019). In group C, all except CDI in deep capillary plexus showed a significant decrease at 6 months (0.35 ± 0.01) compared to baseline (0.36 ± 0.02) (P = 0.003).

Conclusion

OSAS alters various retinochoroidal parameters and timely intervention in patients with OSAS can prevent these alterations. Also, these retinochoroidal parameters could serve as one of the markers to monitor the disease progression.

Obstructive Sleep Apnea-Induced Neurogenic Nocturnal Hypertension: A Potential Role of Renal Denervation?

There is a bidirectional, causal relationship between obstructive sleep apnea (OSA) and hypertension. OSA-related hypertension is characterized by high rates of masked hypertension, elevated nighttime blood pressure, a nondipper pattern of nocturnal hypertension, and abnormal blood pressure variability. Hypoxia/hypercapnia-related sympathetic activation is a key pathophysiological mechanism linking the 2 conditions. Intermittent hypoxia also stimulates the renin-angiotensin-aldosterone system to promote hypertension development. The negative and additive cardiovascular effects of OSA and hypertension highlight the importance of effectively managing these conditions, especially when they coexist in the same patient. Continuous positive airway pressure is the gold standard therapy for OSA but its effects on blood pressure are relatively modest. Furthermore, this treatment did not reduce the cardiovascular event rate in nonsleepy patients with OSA in randomized controlled trials. Antihypertensive agents targeting sympathetic pathways or the renin-angiotensin-aldosterone system have theoretical potential in comorbid hypertension and OSA, but current evidence is limited and combination strategies are often required in drug resistant or refractory patients. The key role of sympathetic nervous system activation in the development of hypertension in OSA suggests potential for catheter-based renal sympathetic denervation. Although long-term, randomized controlled trials are needed, available data indicate sustained and relevant reductions in blood pressure in patients with hypertension and OSA after renal denervation, with the potential to also improve respiratory parameters. The combination of lifestyle interventions, optimal pharmacological therapy, continuous positive airway pressure therapy, and perhaps also renal denervation might improve cardiovascular risk in patients with OSA.

Impact of CPAP on Forehead Near-infrared Spectroscopy Measurements in Patients With Acute Respiratory Failure: Truth or Illusion

BACKGROUND

Critically ill patients with acute respiratory failure admitted to an intensive care unit are at high risk for cerebral hypoxia. We investigated the impact of continuous positive airway pressure (CPAP) therapy on regional cerebral tissue oxygenation (rSO2).

MATERIALS AND METHODS

In total, 40 extubated surgical intensive care unit patients requiring classic oxygen therapy (COT) for acute respiratory failure were examined. Near-infrared spectroscopy (INVOS 5100C, Covidien) was used for 30 minutes to detect bilateral rSO2 during COT via facemask (6 L/min) and CPAP therapy (40% fraction of inspired oxygen, 8 cm H2O CPAP) using a randomized crossover study design. Patients served as their own control. Continuous hemodynamic routine monitoring and blood gas analysis were performed. The effect of CPAP therapy on rSO2 and influence of assessed covariables were investigated using a mixed linear model.

RESULTS

Median rSO2 increased from 57.9% (95% confidence interval [CI], 54.2-61.5) during COT to 62.8% (95% CI, 59.2-66.5) during CPAP therapy (P<0.0001). The estimated difference from the mixed model between COT and CPAP is -5.0 (95% CI, -6.3 to -3.7). Median arterial partial pressure of carbon dioxide decreased from 47.8±5.1 mm Hg during COT to 43.1±5 mm Hg during CPAP (P<0.001), whereas arterial partial pressure of oxygen remained unchanged (P=0.329). In total, 23% of patients had SO2 levels <50%, with a higher prevalence under COT.

CONCLUSIONS

Our results reveal that CPAP therapy compared with COT may influence rSO2 in patients with acute respiratory failure. However, the cause of the rSO2 increase following CPAP application remains to be elucidated, and the accuracy of cerebral oximetry during CPAP therapy in patients with acute respiratory failure remains questionable.

Obstructive sleep apnea, hypertension, resistant hypertension and cardiovascular disease

Obstructive sleep apnea (OSA) is one of the most common causes of hypertension (HTN) and cardiovascular disease (CVD). It is also a quite common underlying factor in resistant HTN (RHTN). The main etiological factor of OSA is obesity, which is a rapidly growing global epidemic. To control obesity, patients should be encouraged by health care professionals to lose weight and be educated about weight loss strategies such as lifestyle modifications, which include regular exercise, low-calorie diet, low sodium intake, smoking cessation, and decreased alcohol consumption. This review also emphasizes the importance of screening for OSA as the major underlying cause of essential, and RHTN, which can lead to CVD and can cause end-organ damage. It also stresses the importance of using continuous positive airway pressure (CPAP) and its beneficial effects, along with other antihypertensive regimens, in treating HTN, and RHTN. Treatment with CPAP therapy decreases sympathetic activity, high blood pressure (BP), heart rate, and CVD as well as its associated mortality.

Influence of nasal CPAP on cardiorespiratory control in healthy neonate

The present study aimed to further unravel the effects of nasal continuous positive airway pressure (nCPAP) on the cardiovascular and respiratory systems in the neonatal period. Six-hour polysomnographic recordings were first performed in seven healthy newborn lambs, aged 2-3 days, without and with nCPAP application at 6 cmH₂O (nCPAP-6), in randomized order. The effects of nCPAP-6 on heart rate variability, respiratory rate variability, and cardiorespiratory interrelations were analyzed using a semiautomatic signal processing approach applied to ECG and respiration recordings. Thereafter, a cardiorespiratory mathematical model was adapted to the experimental conditions to gain further physiological interpretation and to simulate higher nCPAP levels (8 and 10 cmH₂O). Results from the signal processing approach suggest that nCPAP-6 applied in newborns with healthy lungs: 1) increases heart rate and decreases the time and frequency domain indices of heart rate variability, especially those representing parasympathetic activity, while increasing the complexity of the RR-interval time series; 2) prolongs the respiratory cycle and expiration duration and decreases respiratory rate variability; and 3) slightly impairs cardiorespiratory interrelations. Model-based analysis revealed that nCPAP-6 increases the heart rate and decreases respiratory sinus arrhythmia amplitude, in association with a reduced parasympathetic efferent activity. These results were accentuated when simulating an increased CPAP level. Overall, our results provide a further understanding of the effects of nCPAP in neonates, in the absence of lung disease.NEW & NOTEWORTHY Application of nasal continuous positive airway pressure (CPAP) at 6 cmH₂O, a level very frequently used in newborns, alters heart and respiratory rate variability, as well as cardiorespiratory interrelations in a full-term newborn model without lung disease. Moreover, whereas nasal CPAP at 6 cmH₂O decreases parasympathetic efferent activity, there is no change in sympathetic efferent activity.

Systemic hypertension in obstructive sleep apnea

There is consistent epidemiological evidence that sleep disordered breathing and systemic arterial hypertension are deeply associated, being linked through a bidirectional complex interaction among multiple mechanisms including autonomic nervous system alterations, inflammation, hormonal and hemodynamic components, sleep alterations. However there are several unanswered questions not only from a pathophysiological perspective, but also regarding the effects of obstructive sleep apnea (OSA) treatment on arterial blood pressure values. At present, while many studies have supported the possibility to obtain at least a small blood pressure reduction with OSA treatment, in particular in hypertensive patients, large trials have not clearly confirmed a significant anti-hypertensive effect, nor a beneficial effect of this intervention on cardiovascular endpoints including cardiovascular mortality. Aim of the present review article is to address the relationship between OSA and hypertension in the light of the latest evidence in the field. Moreover we will discuss research topics which need to be investigated in the future, in order to better clarify still pending issues with the aim of obtaining an early diagnosis, a more suitable phenotyping including comorbidities, and better strategies to improve patients' compliance and adherence to treatment.

The acute effect of continuous positive airway pressure titration on blood pressure in awake overweight/obese patients with obstructive sleep apnoea

OBJECTIVES

Continuous positive airway pressure (CPAP) improves upper airway obstruction in patients with obstructive sleep apnoea (OSA), who often are overweight-obese. Although it is thought that CPAP improves long-term blood pressure control (BP), the impact of acute and short-term CPAP use on the cardiovascular system in obese patients has not been described in detail.

METHODS

Obese patients (body mass index, BMI > 25 kg/m²) with OSA were studied awake, supine during incremental CPAP titration (4-20 cmH₂O, +2 cmH₂O/3 mins). BP was measured continuously with a beat-to-beat BP monitor (Ohmeda 2300, Finapres Medical Systems, Amsterdam/NL), BP variability (BPV) was calculated as the standard deviation of BP at each CPAP level, the 95% confidence interval (95%CI) was calculated and changes in BP and BPV were reported.

RESULTS

15 patients (12 male, 48 ± 10) years, BMI 38.9 ± 5.8 kg/m²) were studied; the baseline BP was 131.0 ± 10.2/85.1 ± 9.1 mmHg. BP and BPV increased linearly with CPAP titration (systolic BP r = 0.960, p < .001; diastolic BP r = 0.961, p < .001; systolic BPV r = 0.662, p = .026; diastolic BPV r = 0.886, p < .001). The systolic BP increased by +17% (+23.15 (7.9, 38.4) mmHg; p = .011) and the diastolic BP by +23% (+18.27 (2.33, 34.21) mmHg; p = .009), when titrating CPAP to 20 cmH₂O. Systolic BPV increased by +96% (+5.10 (0.67, 9.53) mmHg; p < .001) and was maximal at 14 cmH₂O, and diastolic BPV by +97% (+3.02 (0.26, 5.78) mmHg; p < .001) at 16 cmH₂O.

CONCLUSION

Short-term incremental CPAP leads to significant increases in BP and BPV in obese patients with OSA while awake. Careful titration of pressures is required to minimise the risk of nocturnal awakenings while improving BP control.