Skip to main content

Main menu

  • Home
  • Current issue
  • ERJ Early View
  • Past issues
  • ERS Guidelines
  • Authors/reviewers
    • Instructions for authors
    • Submit a manuscript
    • Open access
    • Peer reviewer login
  • Alerts
  • Subscriptions
  • ERS Publications
    • European Respiratory Journal
    • ERJ Open Research
    • European Respiratory Review
    • Breathe
    • ERS Books
    • ERS publications home

User menu

  • Log in
  • Subscribe
  • Contact Us
  • My Cart

Search

  • Advanced search
  • ERS Publications
    • European Respiratory Journal
    • ERJ Open Research
    • European Respiratory Review
    • Breathe
    • ERS Books
    • ERS publications home

Login

European Respiratory Society

Advanced Search

  • Home
  • Current issue
  • ERJ Early View
  • Past issues
  • ERS Guidelines
  • Authors/reviewers
    • Instructions for authors
    • Submit a manuscript
    • Open access
    • Peer reviewer login
  • Alerts
  • Subscriptions

Impact of obstructive sleep apnoea and intermittent hypoxia on blood rheology: a translational study

Xavier Waltz, Andrew E. Beaudin, Elise Belaidi, Jill Raneri, Jean-Louis Pépin, Vincent Pialoux, Patrick J. Hanly, Samuel Verges, Marc J. Poulin
European Respiratory Journal 2021 58: 2100352; DOI: 10.1183/13993003.00352-2021
Xavier Waltz
1Dept of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
2Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
3Laboratoire HP2, Grenoble Alpes University, INSERM, CHU Grenoble Alpes, Grenoble, France
9These two authors contributed equally to this work
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Andrew E. Beaudin
1Dept of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
2Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
9These two authors contributed equally to this work
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • ORCID record for Andrew E. Beaudin
Elise Belaidi
3Laboratoire HP2, Grenoble Alpes University, INSERM, CHU Grenoble Alpes, Grenoble, France
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Jill Raneri
4Sleep Centre, Foothills Medical Centre, Calgary, AB, Canada
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Jean-Louis Pépin
3Laboratoire HP2, Grenoble Alpes University, INSERM, CHU Grenoble Alpes, Grenoble, France
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Vincent Pialoux
5Laboratoire Interuniversitaire de Biologie de la Motricité, University of Lyon, Lyon, France
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • ORCID record for Vincent Pialoux
Patrick J. Hanly
2Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
4Sleep Centre, Foothills Medical Centre, Calgary, AB, Canada
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Samuel Verges
3Laboratoire HP2, Grenoble Alpes University, INSERM, CHU Grenoble Alpes, Grenoble, France
10S. Verges and M.J. Poulin contributed equally to this article as lead authors and supervised the work
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • ORCID record for Samuel Verges
Marc J. Poulin
1Dept of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
2Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
6Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
7Dept of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
8Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
10S. Verges and M.J. Poulin contributed equally to this article as lead authors and supervised the work
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • ORCID record for Marc J. Poulin
  • For correspondence: poulin@ucalgary.ca
  • Article
  • Figures & Data
  • Info & Metrics
  • PDF
Loading

Abstract

Background Haemorheological alterations are reported in obstructive sleep apnoea (OSA) and reversed with continuous positive airway pressure (CPAP), observations potentially explained by intermittent hypoxia (IH)-induced oxidative stress. Our objective was to investigate whether IH causes haemorheological alterations via oxidative stress.

Methods Wistar rats were exposed to normoxia (n=7) or IH (n=8) for 14 days. 23 moderate-to-severe OSA patients were assessed at three time-points: baseline, after randomisation to either 2 weeks of nocturnal oxygen (n=13) or no treatment (n=10) and after 1 month of CPAP treatment (n=17). Furthermore, an OSA-free control group (n=13) was assessed at baseline and after time-matched follow-up. We measured haemorheological parameters (haematocrit, blood viscosity, plasma viscosity (rats only), erythrocyte aggregation and deformability (humans only)) and redox balance (superoxide dismutase (SOD), glutathione peroxidase, protein oxidation (advanced oxidation protein products (AOPPs)) and lipid peroxidation (malondialdehyde)). We also tested the haemorheological sensitivity of erythrocytes to reactive oxygen species (ROS) in our human participants using the oxidant t-butyl hydroperoxide (TBHP).

Results In rats, IH increased blood viscosity by increasing haematocrit without altering the haemorheological properties of erythrocytes. IH also reduced SOD activity and increased AOPPs. In humans, baseline haemorheological properties were similar between patients and control participants, and properties were unaltered following oxygen and CPAP, except erythrocyte deformability was reduced following oxygen therapy. Redox balance was comparable between patients and control participants. At baseline, TBHP induced a greater reduction of erythrocyte deformability in patients while CPAP reduced TBHP-induced increase in aggregation strength.

Conclusions IH and OSA per se do not cause haemorheological alterations despite the presence of oxidative stress or higher sensitivity to ROS, respectively.

Abstract

Obstructive sleep apnoea and/or intermittent hypoxia per se are not significantly implicated in haemorheological disturbances https://bit.ly/3seciGd

Introduction

Obstructive sleep apnoea (OSA) is characterised by repetitive apnoeas and hypopnoeas resulting in intermittent hypoxaemia (IH), recurrent arousals and intrathoracic pressure swings during sleep [1], all of which are implicated in the pathogenesis of cardiovascular and cerebrovascular disease in OSA [2–5].

Although the many features of OSA, including IH, intermittent hypercapnia, sleep fragmentation, increased negative intrathoracic pressure and elevated sympathetic nerve activity, likely contribute to the increased risk of vascular disease in OSA, evidence implicates chronic IH exposure as the main mediator [6]. A major pathway through which IH contributes to vascular risk is by increasing oxidative stress [7], which in turn promotes endothelial dysfunction [8]. Another potential mechanism is oxidative stress-induced haemorheological alterations [9–12].

Haemorheology is the study of blood flow properties, including blood viscosity, plasma viscosity, erythrocyte aggregation and erythrocyte deformability [13–17], and their impact on blood flow resistance and tissue oxygenation [16, 18, 19]. In observational studies, untreated OSA patients are reported to have altered blood viscosity and erythrocyte aggregation [20–23], two haemorheological alterations predictive of adverse cardiovascular and cerebrovascular events (unstable angina, myocardial infarction and stroke) [24] and endothelial dysfunction [25]. Importantly, in a nonrandomised intervention, 5 days of continuous positive airway pressure (CPAP) treatment appears to reverse haemorheological alterations in OSA patients [22], potentially through correction of OSA-related IH-induced oxidative stress. However, the relationships between IH, oxidative stress and haemorheological alterations have not been examined in the context of OSA.

Employing a translational study design with both an animal model of IH and newly diagnosed OSA patients, we investigated the extent to which 1) IH causes haemorheological alterations and 2) oxidative stress contributes to haemorheological alterations in OSA. We hypothesised that IH causes haemorheological alterations via oxidative stress. To test this hypothesis, we assessed oxidative stress and blood rheology in rats exposed to IH for 14 days, and we compared the effects of nocturnal oxygen therapy (a treatment that rectifies OSA-related IH, but not sleep fragmentation and intrathoracic negative pressure swings related to apnoeic events) and CPAP treatment (a treatment that corrects IH and ancillary features of OSA) in humans. Finally, we examined the susceptibility of blood rheological properties to reactive oxygen species (ROS) in vitro by treating erythrocytes from OSA patients with an oxidant.

Materials and methods

Additional details are provided in the supplementary material.

Animal model of IH (Grenoble, France; 212 m above sea level)

All animal experiments were performed in Grenoble in 2017 in accordance with the Institute for Laboratory Animal Research “Guide for the Care and Use of Laboratory Animals” and approvals (201603301129626) from the Université Grenoble Alpes Ethical Committee. After randomisation, male Wistar rats were exposed to either normoxia (n=7) or severe IH (n=8) for 14 days (8 h·day−1). IH consisted in 60 s cycles alternating 30 s of hypoxia (5% inspiratory oxygen fraction (FIO2) and 30 s of normoxia (21% FIO2). Normoxic rats were exposed to similar air–air cycles. Next, rats were anaesthetised using intraperitoneal injection of pentobarbital (60 mg·kg−1) and received an intravenous heparin injection before blood draw.

Human experiments (Calgary, AB, Canada; 1103 m above sea level)

Experiments were performed according to the Declaration of Helsinki and approved by the Conjoint Health Research Ethics Board of the University of Calgary (REB15-1153). 23 newly diagnosed patients with moderate-to-severe OSA (oxygen desaturation index (ODI) ≥15 events·h−1 and arterial oxygen saturation (SaO2) <90% for ≥12% of total recording time) and 13 OSA-free control participants were recruited (age 18–66 years) between January 2014 and June 2016. OSA was diagnosed by home sleep apnoea testing (HSAT) (Remmers Sleep Recorder; Sagatech Electronics, Calgary, AB, Canada) [26]. The ODI was calculated by indexing the number of times SaO2 decreases by ≥4% to the total SaO2 recording time. Furthermore, a manual respiratory event index (REI) representing the number of apnoeas–hypopnoeas per hour was determined using only the flow channel. Exclusion criteria included previous stroke, body mass index (BMI) ≥40 kg·m−2, peripheral vascular disease, coronary artery disease, hypertension, nephropathy, diabetes, respiratory disorders, pregnancy, current smoker and taking medications affecting the vasculature. All participants gave written informed consent.

Human experimental protocol

The human experimental protocol is shown in supplementary figure E1. After a familiarisation visit, OSA patients performed visit 1 to determine baseline parameters. Next, patients were randomised into either nocturnal oxygen therapy (OSA O2; n=13) or no treatment (OSA Air; n=10) for 2 weeks before a second experimental visit. After visit 2, all patients received CPAP and underwent visit 3 after ∼4 weeks of adherent treatment (post-CPAP). Treatment adherence was defined as CPAP use for ≥4 h·night−1 for ≥70% of the days over 4 consecutive weeks [27]. Before each visit (baseline, post-oxygen and post-CPAP), patients underwent HSAT. Between visit 2 and visit 3 (post-CPAP), six patients were lost to follow-up.

13 OSA-free (HSAT) control participants age and sex matched with OSA patients were recruited. Each performed familiarisation, baseline and follow-up visits. Follow-up visits were scheduled to correspond approximately with the interval between visit 1 (baseline) and visit 3 (post-CPAP) for OSA patients.

Blood pressure in humans

During visit 1, resting brachial blood pressure (BP755; Omron Healthcare, Burlington, ON, Canada) was measured ≥3 times throughout a 10-min period and then averaged.

Haemorheological and haematological parameters

Nonfasting venous blood samples were drawn and placed in EDTA tubes for haematological and haemorheological measurements within 4 h after blood sampling.

Rats

Haematocrit was measured by microcentrifugation. Blood and plasma viscosity were measured at 25°C using a cone-plate viscometer (MCR 302 with CPE 50 spindle; Anton Paar, Graz, Austria). Blood viscosity was measured at low (2.15 s−1) and high shear rates (1000 s−1) and plasma viscosity at 1000 s−1. Blood viscosity was determined both on native blood and after normalising blood to a haematocrit of 40%.

Humans

Haematocrit was measured using a blood gas analyser (ABL837 FLEX; Radiometer, Brønshøj, Denmark). Blood viscosity was measured at ∼23°C using a cone-plate viscometer (DV2T with CPE40 spindle; Brookfield, Middleboro, MA, USA) at low (45 s−1) and higher shear rates (225 s−1). Erythrocyte deformability was measured at 3 and 30 Pa by ektacytometry (at 37°C) and erythrocyte aggregation by syllectometry at a standardised haematocrit of 40% (at 37°C). The disaggregation threshold was determined using a reiteration procedure (LORRCA MaxSis; RR Mechatronics, Hoorn, The Netherlands) [28]. White blood cell and platelet total counts, haemoglobin concentration, and mean cell volume and mean cell haemoglobin concentration were determined using a haematology analyser (Max M-Retic; Coulter, Fullerton, CA, USA).

Assessment of plasma redox balance in rats and humans

Antioxidant enzymes

We determined plasma superoxide dismutase (SOD) [29] and glutathione peroxidase (GPX) activities, as previously described [30].

Oxidative stress biomarkers

Lipid peroxidation and protein oxidation were assessed by quantifying plasma malondialdehyde (MDA) [31] and advanced oxidation protein product (AOPP) concentrations, respectively, as previously described [32].

Erythrocyte rheological response to ROS in humans

Erythrocytes from OSA patients and control participants were incubated with either 5.4 mmol·L−1 of the oxidant t-butyl hydroperoxide (TBHP) diluted in ethanol (Sigma Aldrich, St Quentin-Fallavier, France) (TBHP condition) or with ethanol alone (sham condition) for 10 min at 23°C [11]. Erythrocytes were then resuspended in autologous plasma at a standard haematocrit of 40% prior to erythrocyte deformability and aggregation measurements.

Statistical analyses

For baseline data, we compared OSA and control participants using either independent t-tests or Mann–Whitney rank sum tests. Furthermore, since OSA may be protective or deleterious with respect to cardiovascular and cerebrovascular disease depending on disease severity [33], patients were also divided into two groups based upon the median ODI, i.e. less severe (ODI <35.4 events·h−1) and more severe (ODI ≥35.4 events·h−1) and compared with control participants. Additional details are provided in the supplementary material. Analyses were performed using SPSS version 23 (IBM, Armonk, NY, USA) and presented as mean±sd. The α-level was set a priori at 0.05.

Results

Impact of IH on haematocrit and blood rheology in rats

Figures 1 and 2 show the effects of IH on haematocrit and blood rheology in rats. IH led to an increase in haematocrit (figure 1a). Plasma viscosity was not affected by IH (figure 1b). Blood viscosity at low (figure 2a) and high (figure 2b) shear rates was increased following IH exposure. However, when measured at a normalised haematocrit of 40%, blood viscosity at both low (figure 2c) and high (figure 2d) shear rates was no longer different between hypoxic and normoxic rats.

FIGURE 1
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 1

Effects of intermittent hypoxia (IH) on a) haematocrit and b) plasma viscosity in rats. FIO2: inspiratory oxygen fraction. Male Wistar rats were exposed to either 14 days of normoxia (n=7) or IH (n=8). The IH stimulus consisted of 60 s cycles alternating 30 s of hypoxia (hypoxic phase at 5% FIO2) and 30 s of normoxia (normoxic phase at 21% FIO2) for 8 h·day−1. One rat was lost for plasma viscosity measurements in the IH group because of a lack of blood/plasma. ***: p<0.001.

FIGURE 2
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 2

Effects of intermittent hypoxia (IH) on a, b) native and c, d) normalised blood viscosity in rats: a, c) 2.15 s−1 and b, d) 1000 s−1. FIO2: inspiratory oxygen fraction. Male Wistar rats were exposed to either 14 days of normoxia (n=7) or IH (n=8). The IH stimulus consisted of 60 s cycles alternating 30 s of hypoxia (hypoxic phase at 5% FIO2) and 30 s of normoxia (normoxic phase at 21% FIO2) for 8 h·day−1. One rat was lost for normalised blood viscosity measurements in the IH group because of a lack of blood/plasma. ***: p<0.001.

Impact of IH on redox balance in rats

Severe IH reduced SOD activity and increased AOPPs (figure 3a and c, respectively), but had no effect on GPX activity and MDA (figure 3b and d, respectively).

FIGURE 3
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 3

Effects of intermittent hypoxia (IH) on redox balance in rats: a) superoxide dismutase (SOD), b) glutathione peroxidase (GPX), c) advanced oxidation protein products (AOPPs) and d) malondialdehyde (MDA). FIO2: inspiratory oxygen fraction. Male Wistar rats were exposed to either 14 days of normoxia (n=7) or IH (n=7). The IH stimulus consisted of 60 s cycles alternating 30 s of hypoxia (hypoxic phase at 5% FIO2) and 30 s of normoxia (normoxic phase at 21% FIO2). *: p<0.05.

Baseline characteristics and parameters in control participants and OSA patients

Baseline participant characteristics are summarised in table 1. Age and sex distribution were similar between control participants and OSA patients, whereas OSA patients had a higher BMI, ODI and REI, and greater nocturnal hypoxaemia compared with control participants. Furthermore, control participants, less severe OSA patients and more severe OSA patients had similar age and sex distributions. The more severe OSA patients had a higher BMI compared with control participants. By design ODI, REI and SaO2 <90% exhibited the following continuum: control participants<less severe OSA patients<more severe OSA patients.

View this table:
  • View inline
  • View popup
TABLE 1

Baseline participant characteristics, haematological and haemorheological parameters

OSA patients had higher diastolic blood pressure compared with control participants and tended to have higher mean arterial blood pressure; these results were driven by the more severe OSA patients who had higher mean and diastolic blood pressures compared with control participants.

There were no differences in baseline haematological and haemorheological parameters between control participants and OSA patients. Similarly, no differences were observed between control participants, less severe OSA and more severe OSA patients.

Impact of oxygen and CPAP therapies on blood rheology in OSA patients

Adherence to oxygen and CPAP therapies is summarised in table 2. The mean duration of nocturnal oxygen therapy was 14.5 days with an average use of 7.2 h·night−1. During the 30 days immediately prior to the final experimental visit, OSA patients used CPAP for >4 h·night−1 on ∼89% of the nights, with an average duration of 6 h·night−1. Both oxygen and CPAP led to a decrease in ODI, REI and time with SaO2 <90%. Oxygen therapy increased mean nocturnal SaO2 to a greater extent than CPAP, but decreased REI to a lesser extent than CPAP.

View this table:
  • View inline
  • View popup
TABLE 2

Adherence to oxygen and continuous positive airway pressure (CPAP) treatments and impact of oxygen and CPAP therapies on obstructive sleep apnoea (OSA) severity

Despite excellent adherence to nocturnal oxygen and CPAP therapy, neither treatment modified blood rheological properties (supplementary figures E2 and E3, respectively). However, oxygen therapy caused a decrease in erythrocyte deformability measured at high shear stress (supplementary figure E2f).

Impact of oxygen and CPAP therapies on redox balance

At baseline, redox balance was similar between OSA patients and control participants (figure 4). Furthermore, neither CPAP (figure 4) nor oxygen therapy (figure 5) altered SOD and GPX activities or AOPP and MDA concentrations.

FIGURE 4
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 4

Effects of continuous positive airway pressure (CPAP) therapy on redox balance: a) superoxide dismutase (SOD) activity, b) glutathione peroxidase (GPX) activity, c) advanced oxidation protein products (AOPPs) and d) malondialdehyde (MDA). OSA: obstructive sleep apnoea. Control participants: n=13; OSA pre-CPAP: n=17; OSA post-CPAP: n=17.

FIGURE 5
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 5

Effects of oxygen therapy on redox balance: a) superoxide dismutase (SOD) activity, b) glutathione peroxidase (GPX) activity, c) advanced oxidation protein products (AOPPs) and d) malondialdehyde (MDA). OSA: obstructive sleep apnoea. OSA Air: OSA patients not treated with oxygen (n=10); OSA pre-/post-O2: OSA patients treated with oxygen for 2 weeks (n=13). Two samples for AOPPs (pre- and post-O2 in c) and one sample for MDA (post-O2 in d) were lost for technical reasons.

Erythrocyte rheological susceptibility to ROS at baseline in humans

Human erythrocyte haemorheological susceptibility to ROS at baseline is shown in figure 6. Incubation of erythrocytes with TBHP reduced erythrocyte aggregation (figure 6a), increased erythrocyte aggregation strength (i.e. disaggregation threshold) (figure 6b), and decreased erythrocyte deformability measured at low (figure 6c) and high shear stress (figure 6d). Compared with control participants, TBHP-induced decrease of erythrocyte deformability tended to be greater at low shear stress (p=0.08) and was further exacerbated at higher shear stress in OSA patients (figure 6c and d, respectively).

FIGURE 6
  • Download figure
  • Open in new tab
  • Download powerpoint
FIGURE 6

Erythrocyte rheological susceptibility to reactive oxygen species (t-butyl hydroperoxide (TBHP) incubation) at baseline: a) aggregation, b) disaggregation threshold, c) deformability at 3 Pa and d) deformability at 30 Pa. OSA: obstructive sleep apnoea. Control participants: n=9; OSA patients: n=13. *: p<0.05; ns: nonsignificant.

Impact of oxygen and CPAP therapies on erythrocyte rheological susceptibility to ROS

The impact of oxygen and CPAP therapies on erythrocyte rheological susceptibility to ROS is shown in supplementary figures E4 and E5, respectively. TBHP-induced increase in the erythrocyte disaggregation threshold in OSA patients was unchanged after oxygen treatment (p=0.13) (supplementary figure E4b) and reduced after CPAP treatment (supplementary figure E5b). TBHP-induced alterations in erythrocyte aggregation and deformability were unchanged following oxygen (supplementary figure E4) and CPAP therapies (supplementary figure E5).

Discussion

In rats, we demonstrated that severe IH increased oxidative stress and blood viscosity. However, IH-induced blood hyperviscosity was driven by an increase in haematocrit without concomitant qualitative erythrocyte haemorheological alterations (i.e. erythrocyte aggregation and deformability). Furthermore, we showed in humans that moderate-to-severe OSA was not associated with either haemorheological abnormalities or oxidative stress. Consequently, oxygen and CPAP treatments had no effect on blood rheology, except that oxygen therapy reduced erythrocyte deformability. Nevertheless, erythrocyte deformability was more sensitive to ROS in OSA patients. Furthermore, CPAP decreased the susceptibility of the erythrocyte aggregation strength to ROS. These results suggest that, although OSA patients had a similar degree of oxidative stress compared with control participants at baseline, erythrocyte haemorheological properties are more impacted by ROS induction in OSA patients.

Effects of IH and OSA on haemorheology

Previous studies have reported that OSA patients have, for a given haematocrit, higher blood viscosity and erythrocyte aggregation [21, 22, 34]. Although speculated to result from chronic IH exposure [22], the question of whether IH per se is capable of producing these haemorheological disturbances had not been investigated until now. By exposing male Wistar rats to either 14 days of normoxia or IH, we found that IH leads to an increase in haematocrit and blood viscosity. Yet, when blood viscosity was measured at a standard haematocrit of 40%, it was no longer different between normoxic and IH groups. At a given haematocrit, blood viscosity assessed at low shear rate is mainly determined by erythrocyte aggregation, whereas at high shear rates it is mainly determined by erythrocyte deformability [35]. This suggests that the IH-induced increase in blood viscosity was driven by the increase in haematocrit and that 14 days of severe IH does not cause alterations in erythrocyte aggregation and deformability.

Next, to interrogate the role of IH on haemorheological alterations in OSA, we compared the effects of nocturnal oxygen (a treatment that rectifies OSA-related IH and not ancillary features since apnoeas still persist) and CPAP (a treatment that corrects IH and ancillary features) therapies on haemorheology, in newly diagnosed OSA patients. In contrast to previous studies [21, 22], we observed no haemorheological alterations in OSA patients prior to treatment of OSA. Moreover, in contrast to our animal model of IH, we observed similar haematocrit levels between OSA patients and control participants. This difference between our animal model and OSA patients likely arose from the more severe IH exposure in the animal model compared with our OSA cohort. Furthermore, corroborating the observations made in our animal model of IH, blood viscosity was not different between OSA and control participants when assessed at a standard haematocrit (i.e. 40%). Another potential explanation for the absence of haemorheological alterations in our OSA patients compared with what has been reported previously [21, 22] is that previous studies recruited OSA patients with comorbidities including hypertension, type 2 diabetes mellitus and coronary artery disease, whereas we recruited only normotensive patients free of overt cardiovascular disease. Hence, IH or OSA may not be the sole cause of haemorheological alterations previously reported.

Since haemorheological properties were unaltered at baseline, both oxygen and CPAP therapies had no major effects on blood rheological parameters, except for a reduction in erythrocyte deformability at high shear stress with oxygen therapy. As oxygen therapy induced a mild degree of hyperoxia compared with CPAP (i.e. 95.5% versus 92.2%) (table 2), it is possible that this greater oxygenation may have increased intra-erythrocytic oxidative stress as a result of greater oxygen availability [36]. Baskurt et al. [9] showed that superoxide anions (i.e. ROS) generated externally have a minor effect on erythrocyte deformability, in contrast to superoxide anions generated internally to erythrocytes. Hence, despite unchanged plasma redox balance as measured in the present study, the reduction of erythrocyte deformability observed may be due to the presence of intra-erythrocytic oxidative stress [9]. Additional research is required to test this hypothesis as intra-erythrocytic oxidative stress was not measured in our study.

Effects of IH and OSA on redox balance

In rats, severe IH caused oxidative stress without affecting erythrocyte deformability and aggregation, demonstrating that chronic IH exposure causes only moderate redox imbalance without affecting haemorheology. Furthermore, we did not observe plasma oxidative stress in moderate-to-severe OSA patients.

Nevertheless, we observed that alterations in erythrocyte deformability induced by the same concentration of ROS in situ were exacerbated in erythrocytes from OSA patients compared with control subjects (figure 6). We propose that OSA patients may have reduced intra-erythrocytic antioxidant capacities and therefore greater susceptibility to oxidative stress-induced changes in erythrocyte deformability. This is clinically relevant since a 17% decrease in erythrocyte deformability increases blood flow resistance by 75% (normal endothelial function) to 225% (endothelial dysfunction) [14].

Erythrocyte oxidation with TBHP caused an increase of erythrocyte aggregation strength and a reduction of erythrocyte aggregation and deformability. After oxygen therapy, despite a numerically lower increase in the erythrocyte aggregation threshold and a lower decrease in erythrocyte deformability, these changes were not significant (supplementary figure E4). The same observations were made after CPAP therapy, except that the susceptibility of the erythrocyte aggregation threshold to ROS was significantly reduced (supplementary figure E5). These results are not explained by any changes in plasma redox balance following oxygen or CPAP therapies. Future studies should investigate the effect of IH on intra-erythrocytic ROS production and intra-erythrocytic antioxidant capacities.

Our study has several methodological limitations. First, although cone-plate viscometers were used to assess blood viscosity in both the animal experiments performed in France and the human experiments performed in Canada, they were not the same models. As such, blood viscosity was assessed using different shear rates within the animal (2.15 and 1000 s−1) and human experiments (45 and 225 s−1). Blood viscosity measured at very low shear rates is more affected by erythrocyte aggregation, whereas blood viscosity measured at high shear rates mainly reflects erythrocyte deformability. Hence, blood viscosity measured in our animal experiments is a better surrogate of erythrocyte aggregation and deformability compared with blood viscosity measured in our human experiments. However, this was compensated by directly measuring erythrocyte aggregation and deformability properties in human experiments. This was not possible in animal experiments performed in France.

Second, erythrocyte deformability is a multifactorial phenomenon that depends on cytoplasmic viscosity, volume-to-surface ratio, membrane elasticity, tank treading motion and erythrocyte deformations due to cellular collisions. In the human experiments, erythrocyte deformability was measured using ektacytometry. Using this method, erythrocytes are resuspended in polyvinylpyrrolidone at a low haematocrit (<1%) far below physiological values (i.e. ∼35–45%). Furthermore, polyvinylpyrrolidone viscosity is about 30 times larger than plasma viscosity. Hence, ektacytometry does not take into account phenomena such as deformations due to cellular collisions.

In summary, this study demonstrates that IH, both in an experimental animal model and in humans with OSA, does not in itself cause haemorheological alterations. Similarly, severe IH-induced oxidative stress does not necessarily cause haemorheological disturbances. Interestingly, despite the absence of baseline differences in plasma oxidative stress, we found that OSA patients were vulnerable to a decrease in erythrocyte deformability when exposed to increased ROS. This finding is relevant for clinical scenarios in which OSA patients might experience a higher level of ROS (e.g. diabetes, obesity, hypertension, early atherosclerosis, etc.). Taken together, our results suggest that haemorheological alterations reported in previous studies may be caused by comorbidities associated with OSA, rather than OSA alone.

Supplementary material

Supplementary Material

Please note: supplementary material is not edited by the Editorial Office, and is uploaded as it has been supplied by the author.

Supplementary material ERJ-00352-2021.SUPPLEMENT

Shareable PDF

Supplementary Material

This one-page PDF can be shared freely online.

Shareable PDF ERJ-00352-2021.Shareable

Acknowledgements

We thank the healthy volunteers and OSA patients who participated in this study. We also thank Gwennou Coupier, Thomas Podgorski and Lionel Bureau from the Laboratoire Interdisciplinaire de Physique (LIPhy) (Grenoble University, Grenoble, France) for the provision of a blood viscometer, and Lauren L. Drogos (Laboratory of Human Cerebrovascular Physiology, University of Calgary, Calgary, AB, Canada) for her help with blood rheological data collection. Finally, we thank the staff at the Sleep Centre at Foothills Medical Centre, Healthy Heart Sleep Company, Dream Sleep Respiratory (DRS) services and Rimer Alco North America (RANA) Respiratory Care Group in Calgary for their support in participant recruitment and follow-up throughout the study.

Footnotes

  • This article has supplementary material available from erj.ersjournals.com

  • This article has an editorial commentary: https://doi.org/10.1183/13993003.01169-2021

  • Author contributions: The work outlined in this manuscript was led by a multigroup collaboration of senior team members including P.J. Hanly (OSA), V. Pialoux (oxidative stress), E. Belaidi and J-L. Pépin (IH in rodents), and S. Verges and M.J. Poulin (human integrative physiology and IH). X. Waltz, A.E. Beaudin, P.J. Hanly and M.J. Poulin conceived the experimental design of studies conducted in patients with OSA. E. Belaidi, X. Waltz, J-L. Pépin and S. Verges conceived the experimental design of studies conducted in rodents. Primary supervision for X. Waltz was provided by P.J. Hanly and M.J. Poulin (Calgary) and S. Verges (Grenoble), and primary supervision for A.E. Beaudin was provided by P.J. Hanly and M.J. Poulin. The experiments in patients with OSA were performed by A.E. Beaudin, J. Raneri and X. Waltz. The experiments in rodents were performed by X. Waltz and E. Belaidi. All co-authors contributed to the interpretation of the data. X. Waltz wrote the first draft of the manuscript and other co-authors edited the manuscript.

  • Conflict of interest: X. Waltz has nothing to disclose.

  • Conflict of interest: A.E. Beaudin reports other (scholarships) from the Canadian Institutes of Health Research – Heart and Stroke Foundation of Canada (HSFC), Alberta Innovates – Health Solutions (AIHS), and University of Calgary, during the conduct of the study.

  • Conflict of interest: E. Belaidi has nothing to disclose.

  • Conflict of interest: J. Raneri has nothing to disclose.

  • Conflict of interest: J-L. Pépin reports grants and other (research funds) from Air Liquide Foundation, grants, personal fees and other (research funds) from Agiradom, AstraZeneca, Philips and ResMed, grants and personal fees from Fisher and Paykel, Mutualia and Vitalaire, personal fees from Boehringer Ingelheim, Jazz Pharmaceutical, Night Balance and Sefam, outside the submitted work.

  • Conflict of interest: V. Pialoux has nothing to disclose.

  • Conflict of interest: P.J. Hanly has nothing to disclose.

  • Conflict of interest: S. Verges has nothing to disclose.

  • Conflict of interest: M.J. Poulin has nothing to disclose.

  • Support statement: X. Waltz received support from a Harley N. Hotchkiss Postdoctoral Fellowship (Hotchkiss Brain Institute (HBI)), Alberta Innovates – Health Solutions (AIHS) Postgraduate Fellowship programme, Canadian Institutes of Health Research (CIHR) Postdoctoral Fellowship, European Respiratory Society (ERS) Long-term Fellowship and “Fonds de dotation pour la Recherche en Santé Respiratoire (FRSR)”. A.E. Beaudin was supported by an AIHS Doctoral Fellowship, CIHR – Heart and Stroke Foundation of Canada (HSFC) Focus on Stroke Doctoral Fellowship, William H. Davies Medical Research Scholarship (University of Calgary), and Osten-Victor Graduate Scholarship in Cardiology (University of Calgary). Funding for the human part of the present project was provided by CIHR (PI M.J. Poulin, co-applicant P.J. Hanly) and BRAIN CREATE (an interdisciplinary training programme) funded by the Natural Sciences and Engineering Research Council of Canada (PI M.J. Poulin). Funding for the animal part of the present project was provided by “le fond de dotation AGIR pour les maladies chroniques” (E. Belaidi, S. Verges and J-L. Pépin). The LORRCA MaxSis (haemorheological measurements) was purchased with the HBI donor fund (University of Calgary). M.J. Poulin holds the Brenda Strafford Foundation Chair in Alzheimer Research. Funding information for this article has been deposited with the Crossref Funder Registry.

  • Received February 4, 2021.
  • Accepted April 8, 2021.
  • Copyright ©The authors 2021. For reproduction rights and permissions contact permissions{at}ersnet.org
https://www.ersjournals.com/user-licence

References

  1. ↵
    1. Kohler M,
    2. Stradling JR
    . Mechanisms of vascular damage in obstructive sleep apnea. Nat Rev Cardiol 2010; 7: 677–685. doi:10.1038/nrcardio.2010.145
    OpenUrlCrossRefPubMed
  2. ↵
    1. Nieto FJ,
    2. Young TB,
    3. Lind BK, et al.
    Association of sleep-disordered breathing, sleep apnea, and hypertension in a large community-based study. Sleep Heart Health Study. JAMA 2000; 283: 1829–1836. doi:10.1001/jama.283.14.1829
    OpenUrlCrossRefPubMedWeb of Science
    1. Qureshi A,
    2. Ballard RD
    . Obstructive sleep apnea. J Allergy Clin Immunol 2003; 112: 643–651. doi:10.1016/j.jaci.2003.08.031
    OpenUrlCrossRefPubMedWeb of Science
    1. Baguet JP,
    2. Barone-Rochette G,
    3. Tamisier R, et al.
    Mechanisms of cardiac dysfunction in obstructive sleep apnea. Nat Rev Cardiol 2012: 9: 679–688. doi:10.1038/nrcardio.2012.141
    OpenUrlCrossRefPubMed
  3. ↵
    1. Levy P,
    2. Kohler M,
    3. McNicholas WT, et al.
    Obstructive sleep apnoea syndrome. Nat Rev Dis Primers 2015: 1: 15015. doi:10.1038/nrdp.2015.15
    OpenUrlPubMed
  4. ↵
    1. Somers VK,
    2. White DP,
    3. Amin R, et al.
    Sleep apnea and cardiovascular disease: an American Heart Association/American College of Cardiology Foundation Scientific Statement from the American Heart Association Council for High Blood Pressure Research Professional Education Committee, Council on Clinical Cardiology, Stroke Council, and Council on Cardiovascular Nursing. In collaboration with the National Heart, Lung, and Blood Institute National Center on Sleep Disorders Research (National Institutes of Health). Circulation 2008; 118: 1080–1111. doi:10.1161/CIRCULATIONAHA.107.189420
    OpenUrlFREE Full Text
  5. ↵
    1. Lavie L
    . Oxidative stress inflammation and endothelial dysfunction in obstructive sleep apnea. Front Biosci 2012; 4: 1391–1403. doi:10.2741/469
    OpenUrl
  6. ↵
    1. Lavie L,
    2. Lavie P
    . CrossTalk opposing view: most cardiovascular diseases in sleep apnoea are not caused by sympathetic activation. J Physiol 2012; 590: 2817–2819. doi:10.1113/jphysiol.2012.233833
    OpenUrlCrossRefPubMed
  7. ↵
    1. Baskurt OK,
    2. Temiz A,
    3. Meiselman HJ
    . Effect of superoxide anions on red blood cell rheologic properties. Free Radic Biol Med 1998; 24: 102–110. doi:10.1016/S0891-5849(97)00169-X
    OpenUrlCrossRefPubMedWeb of Science
    1. Simmonds MJ,
    2. Meiselman HJ,
    3. Marshall-Gradisnik SM, et al.
    Assessment of oxidant susceptibility of red blood cells in various species based on cell deformability. Biorheology 2011; 48: 293–304. doi:10.3233/BIR-2012-0599
    OpenUrl
  8. ↵
    1. Hierso R,
    2. Waltz X,
    3. Mora P, et al.
    Effects of oxidative stress on red blood cell rheology in sickle cell patients. Br J Haematol 2014; 166: 601–606. doi:10.1111/bjh.12912
    OpenUrlCrossRefPubMed
  9. ↵
    1. Sinha A,
    2. Chu TT,
    3. Dao M, et al.
    Single-cell evaluation of red blood cell bio-mechanical and nano-structural alterations upon chemically induced oxidative stress. Sci Rep 2015; 5: 9768. doi:10.1038/srep09768
    OpenUrlCrossRefPubMed
  10. ↵
    1. Parthasarathi K,
    2. Lipowsky HH
    . Capillary recruitment in response to tissue hypoxia and its dependence on red blood cell deformability. Am J Physiol 1999; 277: H2145–H2157. doi:10.1152/ajpheart.1999.277.6.H2145
    OpenUrl
  11. ↵
    1. Baskurt OK,
    2. Yalcin O,
    3. Meiselman HJ
    . Hemorheology and vascular control mechanisms. Clin Hemorheol Microcirc 2004; 30: 169–178.
    OpenUrlPubMedWeb of Science
    1. Cabrales P,
    2. Tsai AG
    . Plasma viscosity regulates systemic and microvascular perfusion during acute extreme anemic conditions. Am J Physiol Heart Circ Physiol 2006; 291: H2445–H2452. doi:10.1152/ajpheart.00394.2006
    OpenUrlCrossRefPubMedWeb of Science
  12. ↵
    1. Waltz X,
    2. Pichon A,
    3. Mougenel D, et al.
    Hemorheological alterations, decreased cerebral microvascular oxygenation and cerebral vasomotion compensation in sickle cell patients. Am J Hematol 2012; 87: 1070–1073. doi:10.1002/ajh.23318
    OpenUrlPubMed
  13. ↵
    1. Waltz X,
    2. Pichon A,
    3. Lemonne N, et al.
    Normal muscle oxygen consumption and fatigability in sickle cell patients despite reduced microvascular oxygenation and hemorheological abnormalities. PLoS One 2013; 7: e52471. doi:10.1371/journal.pone.0052471
    OpenUrl
  14. ↵
    1. Baskurt OK,
    2. Meiselman HJ
    . Blood rheology and hemodynamics. Semin Thromb Hemost 2003; 29: 435–450. doi:10.1055/s-2003-44551
    OpenUrlCrossRefPubMedWeb of Science
  15. ↵
    1. Baskurt OK,
    2. Yalcin O,
    3. Ozdem S, et al.
    Modulation of endothelial nitric oxide synthase expression by red blood cell aggregation. Am J Physiol Heart Circ Physiol 2004; 286: H222–H229. doi:10.1152/ajpheart.00532.2003
    OpenUrlPubMed
  16. ↵
    1. Nobili L,
    2. Schiavi G,
    3. Bozano E, et al.
    Morning increase of whole blood viscosity in obstructive sleep apnea syndrome. Clin Hemorheol Microcirc 2000; 22: 21–27.
    OpenUrlPubMedWeb of Science
  17. ↵
    1. Dikmenoglu N,
    2. Ciftci B,
    3. Ileri E, et al.
    Erythrocyte deformability, plasma viscosity and oxidative status in patients with severe obstructive sleep apnea syndrome. Sleep Med 2006; 7: 255–261. doi:10.1016/j.sleep.2005.12.005
    OpenUrlCrossRefPubMed
  18. ↵
    1. Tazbirek M,
    2. Slowinska L,
    3. Skoczynski S, et al.
    Short-term continuous positive airway pressure therapy reverses the pathological influence of obstructive sleep apnea on blood rheology parameters. Clin Hemorheol Microcirc 2009; 41: 241–249. doi:10.3233/CH-2009-1175
    OpenUrlPubMed
  19. ↵
    1. Sinnapah S,
    2. Cadelis G,
    3. Waltz X, et al.
    Overweight explains the increased red blood cell aggregation in patients with obstructive sleep apnea. Clin Hemorheol Microcirc 2015; 59: 17–26. doi:10.3233/CH-121655
    OpenUrl
  20. ↵
    1. Ciuffetti G,
    2. Schillaci G,
    3. Lombardini R, et al.
    Prognostic impact of low-shear whole blood viscosity in hypertensive men. Eur J Clin Invest 2005; 35: 93–98. doi:10.1111/j.1365-2362.2005.01437.x
    OpenUrlPubMed
  21. ↵
    1. Yalcin O,
    2. Ulker P,
    3. Yavuzer U, et al.
    Nitric oxide generation by endothelial cells exposed to shear stress in glass tubes perfused with red blood cell suspensions: role of aggregation. Am J Physiol Heart Circ Physiol 2008; 294: H2098–H2105. doi:10.1152/ajpheart.00015.2008
    OpenUrlCrossRefPubMed
  22. ↵
    1. Flemons WW,
    2. Littner MR,
    3. Rowley JA, et al.
    Home diagnosis of sleep apnea: a systematic review of the literature. An evidence review cosponsored by the American Academy of Sleep Medicine, the American College of Chest Physicians, and the American Thoracic Society. Chest 2003; 124: 1543–1579. doi:10.1378/chest.124.4.1543
    OpenUrlCrossRefPubMedWeb of Science
  23. ↵
    1. Gay P,
    2. Weaver T,
    3. Loube D, et al.
    Evaluation of positive airway pressure treatment for sleep related breathing disorders in adults. Sleep 2006; 29: 381–401. doi:10.1093/sleep/29.3.381
    OpenUrlPubMedWeb of Science
  24. ↵
    1. Hardeman MR,
    2. Dobbe JG,
    3. Ince C
    . The Laser-assisted Optical Rotational Cell Analyzer (LORCA) as red blood cell aggregometer. Clin Hemorheol Microcirc 2001; 25: 1–11.
    OpenUrlPubMedWeb of Science
  25. ↵
    1. Oberley L,
    2. Spitz D
    . Nitroblue tetrazolium. In: Greenwald R, ed. Handbook of Methods for Oxygen Radical Research. Boca Raton, CRC Press, 1985; pp. 217–220.
  26. ↵
    1. Paglia DE,
    2. Valentine WN
    . Studies on the quantitative and qualitative characterization of erythrocyte glutathione peroxidase. J Lab Clin Med 1967; 70: 158–169.
    OpenUrlPubMedWeb of Science
  27. ↵
    1. Ohkawa H,
    2. Ohishi N,
    3. Yagi K
    . Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Anal Biochem 1979; 95: 351–358. doi:10.1016/0003-2697(79)90738-3
    OpenUrlCrossRefPubMedWeb of Science
  28. ↵
    1. Witko-Sarsat V,
    2. Friedlander M,
    3. Capeillere-Blandin C, et al.
    Advanced oxidation protein products as a novel marker of oxidative stress in uremia. Kidney Int 1996; 49: 1304–1313. doi:10.1038/ki.1996.186
    OpenUrlCrossRefPubMedWeb of Science
  29. ↵
    1. Lavie L
    . Oxidative stress in obstructive sleep apnea and intermittent hypoxia – revisited – the bad ugly and good: implications to the heart and brain. Sleep Med Rev 2014; 20: 27–45. doi:10.1016/j.smrv.2014.07.003
    OpenUrlPubMed
  30. ↵
    1. Steiner S,
    2. Jax T,
    3. Evers S, et al.
    Altered blood rheology in obstructive sleep apnea as a mediator of cardiovascular risk. Cardiology 2005; 104: 92–96. doi:10.1159/000086729
    OpenUrlCrossRefPubMedWeb of Science
  31. ↵
    1. Chien S
    . Filterability and other methods of approaching red cell deformability. Determinants of blood viscosity and red cell deformability. Scand J Clin Lab Invest Suppl 1981; 156: 7–12. doi:10.3109/00365518109097424
    OpenUrlPubMed
  32. ↵
    1. Winslow RM
    . Oxygen: the poison is in the dose. Transfusion 2013; 53: 424–437. doi:10.1111/j.1537-2995.2012.03774.x
    OpenUrlCrossRefPubMed
PreviousNext
Back to top
View this article with LENS
Vol 58 Issue 4 Table of Contents
European Respiratory Journal: 58 (4)
  • Table of Contents
  • Index by author
Email

Thank you for your interest in spreading the word on European Respiratory Society .

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Impact of obstructive sleep apnoea and intermittent hypoxia on blood rheology: a translational study
(Your Name) has sent you a message from European Respiratory Society
(Your Name) thought you would like to see the European Respiratory Society web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Print
Citation Tools
Impact of obstructive sleep apnoea and intermittent hypoxia on blood rheology: a translational study
Xavier Waltz, Andrew E. Beaudin, Elise Belaidi, Jill Raneri, Jean-Louis Pépin, Vincent Pialoux, Patrick J. Hanly, Samuel Verges, Marc J. Poulin
European Respiratory Journal Oct 2021, 58 (4) 2100352; DOI: 10.1183/13993003.00352-2021

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero

Share
Impact of obstructive sleep apnoea and intermittent hypoxia on blood rheology: a translational study
Xavier Waltz, Andrew E. Beaudin, Elise Belaidi, Jill Raneri, Jean-Louis Pépin, Vincent Pialoux, Patrick J. Hanly, Samuel Verges, Marc J. Poulin
European Respiratory Journal Oct 2021, 58 (4) 2100352; DOI: 10.1183/13993003.00352-2021
del.icio.us logo Digg logo Reddit logo Technorati logo Twitter logo CiteULike logo Connotea logo Facebook logo Google logo Mendeley logo
Full Text (PDF)

Jump To

  • Article
    • Abstract
    • Abstract
    • Introduction
    • Materials and methods
    • Results
    • Discussion
    • Supplementary material
    • Shareable PDF
    • Acknowledgements
    • Footnotes
    • References
  • Figures & Data
  • Info & Metrics
  • PDF

Subjects

  • Sleep medicine
  • Tweet Widget
  • Facebook Like
  • Google Plus One

More in this TOC Section

Original Research Articles

  • Effects of sotatercept on haemodynamics and right heart function
  • Effectiveness of airway clearance techniques in CF
  • Severe asddddddddddddddddddddddarasthma trajectories in adults: NORDSTAR cohort
Show more Original Research Articles

Sleep

  • OSA and 5-year cognitive decline in the elderly
  • Respiratory effort during sleep and prevalent hypertension in OSA
  • Inflammasome activation via oxLDL in OSA and subclinical atherosclerosis
Show more Sleep

Related Articles

Navigate

  • Home
  • Current issue
  • Archive

About the ERJ

  • Journal information
  • Editorial board
  • Press
  • Permissions and reprints
  • Advertising

The European Respiratory Society

  • Society home
  • myERS
  • Privacy policy
  • Accessibility

ERS publications

  • European Respiratory Journal
  • ERJ Open Research
  • European Respiratory Review
  • Breathe
  • ERS books online
  • ERS Bookshop

Help

  • Feedback

For authors

  • Instructions for authors
  • Publication ethics and malpractice
  • Submit a manuscript

For readers

  • Alerts
  • Subjects
  • Podcasts
  • RSS

Subscriptions

  • Accessing the ERS publications

Contact us

European Respiratory Society
442 Glossop Road
Sheffield S10 2PX
United Kingdom
Tel: +44 114 2672860
Email: journals@ersnet.org

ISSN

Print ISSN:  0903-1936
Online ISSN: 1399-3003

Copyright © 2023 by the European Respiratory Society