Konrad E Bloch

University of Zurich, Zürich, Zurich, Switzerland

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Publications (212)1056.64 Total impact

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    Full-text · Dataset · Dec 2015
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    ABSTRACT: Background Obstructive sleep apnoea (OSA) is highly prevalent and associated with cardiovascular and metabolic changes. OSA is usually diagnosed by polysomnography which is time-consuming and provides little information on the patient's phenotype thus limiting a personalised treatment approach. Exhaled breath contains information on metabolism which can be analysed by mass spectrometry within minutes. The objective of this study was to identify a breath profile in OSA recurrence by use of secondary-electrospray-ionization-mass spectrometry (SESI-MS). Methods Patients with OSA effectively treated with CPAP were randomised to either withdraw treatment (subtherapeutic CPAP) or continue therapeutic CPAP for 2 weeks. Exhaled breath analysis by untargeted SESI-MS was performed at baseline and 2 weeks after randomisation. The primary outcome was the change in exhaled molecular breath pattern. Results 30 patients with OSA were randomised and 26 completed the trial according to the protocol. CPAP withdrawal led to a recurrence of OSA (mean difference in change of oxygen desaturation index between groups +30.3/h; 95% CI 19.8/h,40.7/h, p<0.001) which was accompanied by a significant change in 62 exhaled features (16 metabolites identified). The panel of discriminating mass-spectral features allowed differentiation between treated and untreated OSA with a sensitivity of 92.9% and a specificity of 84.6%. Conclusion Exhaled breath analysis by SESI-MS allows rapid and accurate detection of OSA recurrence. The technique has the potential to characterise an individual's metabolic response to OSA and thus makes a comprehensible phenotyping of OSA possible. Trial registration number NCT02050425 (registered at ClinicalTrials.gov).
    No preview · Article · Dec 2015 · Thorax
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    ABSTRACT: Background: Patients with pulmonary hypertension (PH) may suffer from cognitive deficits that potentially relate to reduced oxygen delivery and cerebral tissue oxygenation (CTO). Objective: To evaluate the hypothesis that cognitive function improves with therapy, along with improved CTO. Methods: Twenty incident patients with arterial or chronic thromboembolic PH had CTO monitoring by near-infrared spectroscopy during diagnostic right heart catheterization. Cognitive tests [Trail Making Tests (TMTs), Victoria Stroop tests and the Five-Point Test (5PT)], the 6-min walk distance (6MWD) test, New York Heart Association (NYHA) class and health-related quality of life (HRQoL) were assessed and repeated after 3 months of disease-targeted medication. Results: At baseline, 45% of PH patients had cognitive deficits. At 3 months, the patients had improved on the TMT A and the Stroop 2 test [37 s (27; 55) versus 30 s (24; 42), p < 0.05, and 18 s (16; 22) versus 16 s (15; 20), p < 0.01], whereas CTO remained unchanged. Arterial oxygen saturation, NYHA class, 6MWD and HRQoL had also improved. Baseline CTO was the strongest predictor of cognitive function, even in multivariate analysis including age, 6MWD and HRQoL. Improvements in cognitive function were not associated with changes in CTO. Conclusions: In patients with PH, 3 months of disease-targeted medication resulted in better cognitive function. Although CTO was the strongest predictor of cognitive function at baseline, it did not change during target therapy. The results of this pilot study should be confirmed in an adequately powered controlled trial.
    No preview · Article · Oct 2015 · Respiration
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    ABSTRACT: Background Data on the long-term course of pulmonary artery pressure (mPAP) and development of high altitude pulmonary hypertension (HAPH) are scant. Therefore, we initiated a prospective cohort study in highlanders. Methods: Kyrgyz highlanders living at high altitude (3000-4000 m) underwent yearly questionnaire evaluations, clinical examinations, echocardiography, overnight pulse oximetry (SpO2), spirometry, and a 6 minute walk test starting in 2012. Results: Since 2012, 143 highlanders were included. In 51 of these, mean±SD age 46±12y, 22 women, repeated evaluations from 2012 and 2014 revealed an increase in mPAP while the NYHA functional class, the 6 minute walk distance, FEV1 and nocturnal SpO2 decreased (table in ERJ). In multiple regression analysis including age, gender, mPAP and nocturnal SpO2 at 2012 as predictors, the change in mPAP was correlated with age (Coeff 0.24, P=0.001) and mPAP at baseline (-0.55, P<0.001), R2=0.4534, P<0.001. Conclusions: Pulmonary artery pressure in highlanders was higher than values reported for healthy lowlanders. Moreover mPAP increased considerably within a short time period, in particular in older highlanders and those with a lower initial mPAP. Long-term observations may help to better understand the factors associated with a risk of HAPH.
    No preview · Article · Sep 2015 · European Respiratory Journal
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    ABSTRACT: Introduction: Patients with COPD experience poor sleep at sea level. We investigated whether this was aggravated during a stay at altitude. Methods: 32 COPD patients, GOLD 2-3, living below 800 m, mean±SD age 64±6 yrs, FEV1 60±15% pred., underwent polysomnography and questionnaire evaluations during one night at 490m, 1650m and 2590m, in random order. Results: Compared to 490m sleep studies at the higher altitudes revealed reduced oxygen saturation, a rise in central apnoea/hypopnoea index, reduced slow wave sleep and sleep efficiency, and an impaired subjective sleep quality (table in ERJ). The latter was correlated with the nocturnal oxygen saturation (Spearman r=0.22, P=0.03) but not with the AHI (Spearman r=-0.12, P=0.24). Conclusions: During a stay at moderate altitude lowlanders with COPD experience pronounced hypoxemia that induces central sleep apnoea and sleep disturbances.
    No preview · Article · Sep 2015 · European Respiratory Journal
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    ABSTRACT: Objective: We quantified exercise performance of lowlanders with COPD travelling to moderate altitude and investigated whether reduced cerebral oxygen availability would limit performance. Methods: 31 COPD patients, GOLD grade 2-3, underwent constant-load bicycle spiroergometry to exhaustion at 60% of maximal work rate (mean±SD 65±29W) at 490m and 2590m in randomized order. Pulmonary gas exchange, arterial blood gases, cerebral tissue oxygenation (CTO) by near-infrared spectroscopy, and middle cerebral artery peak blood flow velocity (MCAv) by transcranial Doppler ultrasound were measured. The final 30sec of exercise were compared between altitudes. Results: At 2590m endurance was significantly reduced in association with reduced CTO compared to 490m. The exercise-induced increase in MCAv was similar at both altitudes while MCAv sensitivity to exercise-induced hypoxia was reduced at 2590m (table in ERJ). Conclusions: In lowlanders with COPD travelling to 2590m exercise endurance was reduced compared to 490m. Our data suggest that impaired cerebral oxygen availability limits exercise performance in patients with COPD at 2590m.
    No preview · Article · Sep 2015 · European Respiratory Journal

  • No preview · Conference Paper · Sep 2015

  • No preview · Article · Sep 2015 · European Respiratory Journal

  • No preview · Conference Paper · Sep 2015
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    ABSTRACT: Background Data on the long-term course of pulmonary artery pressure (mPAP) and development of high altitude pulmonary hypertension (HAPH) are scant. Therefore, we initiated a prospective cohort study in highlanders. Methods: Kyrgyz highlanders living at high altitude (3000-4000 m) underwent yearly questionnaire evaluations, clinical examinations, echocardiography, overnight pulse oximetry (SpO2), spirometry, and a 6 minute walk test starting in 2012. Results: Since 2012, 143 highlanders were included. In 51 of these, mean±SD age 46±12y, 22 women, repeated evaluations from 2012 and 2014 revealed an increase in mPAP while the NYHA functional class, the 6 minute walk distance, FEV1 and nocturnal SpO2 decreased (table). In multiple regression analysis including age, gender, mPAP and nocturnal SpO2 at 2012 as predictors, the change in mPAP was correlated with age (Coeff 0.24, P=0.001) and mPAP at baseline (-0.55, P<0.001), R2=0.4534, P<0.001. Conclusions: Pulmonary artery pressure in highlanders was higher than values reported for healthy lowlanders. Moreover mPAP increased considerably within a short time period, in particular in older highlanders and those with a lower initial mPAP. Long-term observations may help to better understand the factors associated with a risk of HAPH.
    No preview · Article · Sep 2015 · European Respiratory Journal
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    ABSTRACT: Background: Physical performance of lowlanders with COPD is impaired during altitude travel. We investigated whether this is related to cardiac dysfunction. Methods and Results: 37 patients, 20 men, median age 66y (quartiles 60;69) with COPD, GOLD 2/3, median FEV1 57% pred (49;71) living below 800m were recruited. Echocardiography, pulse oximetry (SpO2) and 6 min walk distance (6MWD) were assessed at 490m (Zurich) and in the first morning after patients had spent one night at 2590m (Davos). At 490m SpO2 and the 6MWD were 94% (93;96) and 542m (471;585), respectively; right ventricular systolic pressure (RVSP) was 23mmHg (18; 29), RV end-systolic and diastolic areas were 8.4cm2 (7.7;11) and 15.1cm2 (14.1;17.5), respectively; left ventricular ejection fraction (LVEF) was 67% (63;70). At 2590m, corresponding values were SpO2 89% (87;91), 6MWD 506m (447;583),RVSP 39mmHg (34;49), RV end-systolic and diastolic areas 10.5cm2 (8.3;12) and 15.9cm2 (13.8;19.2), LVEF 64% (59;67), P<0.05, all comparisons to 2590 vs. 490m. Conclusions: In lowlanders with COPD, GOLD 2-3, hypoxemia at moderate altitude is associated with a moderate increase in RVSP, and dysfunction of both the right and left ventricle. Therefore, the altitude induced reduction of physical performance of COPD patients may not only be due to ventilatory limitation but mainly due to cardiovascular dysfunction.
    No preview · Article · Sep 2015 · European Respiratory Journal

  • No preview · Article · Sep 2015 · European Respiratory Journal
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    ABSTRACT: Lowlanders commonly report a poor sleep quality during the first few nights after arriving at high altitude. Polysomnographic studies reveal that reductions in slow wave sleep are the most consistent altitude induced changes in sleep structure identified by visual scoring. Quantitative spectral analyses of the sleep electroencephalogram have confirmed an altitude related reduction in the low frequency power (0.8-4.6 Hz). Although some studies suggest an increase in arousals from sleep at high altitude this is not a consistent finding. Whether sleep instability at high altitude is triggered by periodic breathing or vice-versa is still uncertain. Overnight changes in slow wave derived encephalographic measures of neuronal synchronization in healthy subjects were less pronounced at moderately high (2590 m) compared to low altitude (490 m) and this was associated with a decline in sleep related memory consolidation. Correspondingly, exacerbation of breathing and sleep disturbances experienced by lowlanders with obstructive sleep apnea during a stay at 2590 m was associated with poor performance in driving simulator tests. These findings suggest that altitude related alterations in sleep may adversely affect daytime performance. Despite recent advances in our understanding of sleep at altitude further research is required to better establish the role of gender and age in alterations of sleep at different altitudes, to determine the influence of acclimatization and of altitude related illness, and to uncover the characteristics of sleep in highlanders that may serve as a study paradigm of sleep in patients exposed to chronic hypoxia due to cardiorespiratory disease. Copyright © 2015, Journal of Applied Physiology.
    No preview · Article · Jul 2015 · Journal of Applied Physiology
  • Konrad E Bloch · Tsogyal D Latshang · Silvia Ulrich
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    ABSTRACT: Bloch, Konrad E., Tsogyal D. Latshang, and Silvia Ulrich. Patients with obstructive sleep apnea at altitude. High Alt Med Biol. 00:000-000, 2015.-Obstructive sleep apnea (OSA) is highly prevalent in the general population, in particular in men and women of older age. In OSA patients sleeping near sea level, the apneas/hypopneas associated with intermittent hypoxemia are predominantly due to upper airway collapse. When OSA patients stay at altitudes above 1600 m, corresponding to that of many tourist destinations, hypobaric hypoxia promotes frequent central apneas in addition to obstructive events, resulting in combined intermittent and sustained hypoxia. This induces strong sympathetic activation with elevated heart rate, cardiac arrhythmia, and systemic hypertension. There are concerns that these changes expose susceptible OSA patients, in particular those with advanced age and co-morbidities, to an excessive risk of cardiovascular and other adverse events during a stay at altitude. Based on data from randomized trials, it seems advisable for OSA patients to use continuous positive airway pressure treatment with computer controlled mask pressure adjustment (autoCPAP) in combination with acetazolamide during an altitude sojourn. If CPAP therapy is not feasible, acetazolamide alone is better than no treatment at all, as it improves oxygenation and sleep apnea and prevents excessive blood pressure rises of OSA patients at altitude.
    No preview · Article · May 2015 · High altitude medicine & biology

  • No preview · Article · May 2015 · Pneumologie
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    ABSTRACT: High altitude pulmonary hypertension (HAPH), a chronic altitude related illness, causes hypoxemia and impaired exercise performance. We evaluated the hypothesis that hemodynamic limitation and hypoxemia in patients with HAPH are associated with impaired cerebral tissue oxygenation (CTO) compared to healthy highlanders (HH) and lowlanders (LL). We studied 36 highlanders with HAPH and 54 HH at an altitude of 3250 m, and 34 LL at 760 m. Mean(±SD), mean pulmonary artery pressures were 34(±3), 22(±5), 16(±4) mmHg, respectively (p<0.05, all comparisons). CTO was monitored by near-infrared spectroscopy along with pulse oximetry (SpO2 ) during quiet breathing of room air (RA) and oxygen for 20 min each, and during hyperventilation with RA and oxygen, respectively. In HAPH, HH and LL breathing RA, SpO2 was 88(±4)%, 92(±2)%, 95(±2)% (p<0.001, all comparisons), CTO was similar in the 3 groups: 68(±3%), 68(±4)% 69(±4)% (P = NS, all comparisons). Breathing oxygen increased SpO2 and CTO significantly more in HAPH than in HH and LL. Hyperventilation (RA) did not reduce CTO in HAPH but in HH and LL; hyperventilation (oxygen) increased CTO in HAPH only. Highlanders with and without HAPH studied at 3250 m have a similar CTO as healthy lowlanders at 760 m even though highlanders were hypoxemic. The physiologic response to hyperoxia and hypocapnia assessed by cerebral NIRS suggests that healthy highlanders and even highlanders with HAPH effectively maintain an adequate CTO. This adaptation may be of particular relevance since an adequate cerebral oxygenation is essential for vital brain functions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · May 2015 · Experimental physiology
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    ABSTRACT: Introduction: Patients with chronic obstructive pulmonary disease (COPD) might be particularly susceptible to hypoxia-induced autonomic dysregulation. Decreased baroreflex sensitivity (BRS) and increased blood pressure variability (BPV) are markers of impaired cardiovascular autonomic regulation and there is evidence for an association between decreased BRS/increased BPV and high cardiovascular risk. The aim of this study was to evaluate the effect of a short-term exposure to moderate altitude on blood pressure (BP) and measures of cardiovascular autonomic regulation in COPD patients. Methods: Continuous morning beat-to-beat BP was non-invasively measured with a Finometer device during ten minutes atlow altitude (490 m, Zurich) and at two days at moderate altitude (2590 m, Davos Jakobshorn) – the order of altitude exposure was randomized. Outcomes of interest were mean systolic and diastolic BP, BPV expressed as coefficient of variation, and spontaneous BRS. Changes between low altitude and day one and day two at moderate altitude were assessed by analysis of variance (ANOVA) for repeated measurements with Fisher post hoc analysis. Results: 39 patients with moderate to severe COPD (mean±SD age 64±6.2 y, FEV1 1.7±0.7 l, SpO2 93.6±1.8) were included. Systolic morning BP increased by +10.9 mm Hg [95% CI 4.6, 17.2] (p = 0.001) and diastolic morning BP by +6.4 mm Hg [95% CI 2.2, 10.6] (p = 0.004) in response to altitude exposure. BRS significantly and progressively decreased (p = 0.004) at moderate altitude, whereas BPV significantly and progressively increased (p < 0.001) upon exposure to altitude (table 1). Conclusion: Short-term exposure of lowlanders with COPD to moderate altitude is associated with a clinically relevant increase in blood pressure which seems to be related to autonomic dysregulation.
    No preview · Conference Paper · Apr 2015
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    ABSTRACT: Introduction: Patients with obstructive sleep apnea (OSA) suffer from cognitive impairment and are at increased risk of stroke. Suspected underlying mechanisms include cerebral hypoxia related to repetitive arterial oxygen desaturation and impaired cerebrovascular autoregulation. Using a randomized controlled CPAP withdrawal protocol, we evaluated the hypothesis that patients with untreated OSA experience clinically relevant nocturnal cerebral hypoxia which may be prevented by CPAP therapy. Methods: OSA patients established on CPAP treatment taking part in a trial on the effects of CPAP withdrawal on myocardial perfusion were included. Patients were randomized to either continue therapeutic CPAP or to withdraw it for two weeks by using a subtherapeutic CPAP-device. Nocturnal polygraphy including continuous monitoring of regional cerebral tissue oxygenation(CTO) by near infrared spectroscopy (NIRS) with optodes placed on the skin of the forehead was performed at baseline and after two weeks of either therapeutic or subtherapeutic CPAP. Outcomes of interest were the mean nocturnal CTO, the cerebral oxygen desaturation index (cerebral ODI, ≥3% dips) associated with apneas/hypopneas, and the number of patients experiencing a major fall in CTO of ≥13% which has been associated with neurophysiological signs of severe cerebral ischemia in neurosurgical patients [Al-Rawi, Stroke 2006]. Analyses were adjusted for baseline differences. Results: 21 patients (mean±SD: age = 63.0±8.9 yrs, apnea/hypopnea-index at diagnosis = 50.3±19.1/h) were enrolled. CPAP withdrawal led to a recurrence of OSA (increase in apnea/hypopnea index by +40.7/h; 95% CI:+31.1,+50.4/h, p < 0.001). This was associated with a reduced mean arterial and cerebral oxygenation and cyclic drops in CTO (increase in cerebral ODI by +37.0/h; 95% CI:+25.3,+48.7/h, p < 0.001). A major fall of CTO by ≥13% was observed in 4/9 patients treated with subtherapeutic CPAP but in none of the patients on therapeutic CPAP (chi square = 6.6, p = 0.01). Conclusions: CPAP therapy withdrawal – and thus recurrence of OSA – results in intermittent and sustained nocturnal cerebral tissue deoxygenation to a degree reported to cause cerebral dysfunction. These findings suggest that patients with untreated OSA are at increased risk of nocturnal cerebral damage, a threat than can be prevented by CPAP therapy.
    No preview · Conference Paper · Apr 2015
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    ABSTRACT: This work investigates the performance of cardiorespiratory analysis detecting periodic breathing (PB) in chest wall recordings in mountaineers climbing to extreme altitude. The breathing patterns of 34 mountaineers were monitored unobtrusively by inductance plethysmography, ECG and pulse oximetry using a portable recorder during climbs at altitudes between 4497 and 7546 m on Mt. Muztagh Ata. The minute ventilation (VE) and heart rate (HR) signals were studied, to identify visually scored PB, applying time-varying spectral, coherence and entropy analysis. In 411 climbing periods, 30–120 min in duration, high values of mean power (MPVE) and slope (MSlopeVE) of the modulation frequency band of VE, accurately identified PB, with an area under the ROC curve of 88 and 89 %, respectively. Prolonged stay at altitude was associated with an increase in PB. During PB episodes, higher peak power of ventilatory (MPVE) and cardiac (MP LFHR) oscillations and cardiorespiratory coherence (MP LFCoher), but reduced ventilation entropy (SampEnVE), was observed. Therefore, the characterization of cardiorespiratory dynamics by the analysis of VE and HR signals accurately identifies PB and effects of altitude acclimatization, providing promising tools for investigating physiologic effects of environmental exposures and diseases.
    Full-text · Article · Mar 2015 · Medical & Biological Engineering
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    ABSTRACT: Intact postural control is essential for safe performance of mountain sports, operation of machinery at altitude, and for piloting airplanes. We tested whether exposure to hypobaric hypoxia at moderate altitude impairs the static postural control of healthy subjects. In 51 healthy men, median age 24 y (quartiles 20;28), static control was evaluated on a balance platform in Zurich, 490 m, and during a 4-day sojourn in Swiss mountain villages at 1630 m and 2590 m, 2 days each. The order of altitude exposure was randomized. Total center of pressure path length (COPL) and sway amplitude measured in two directions by a balance platform, and pulse oximetry were recorded. Data were compared between altitudes. Median (quartiles) COPL during standing on both legs with eyes open at 490 m and in the evenings on the first and second days at 1630 and 2590 m, respectively were: 50 (45;57), 55 (48;62), 56 (49;61), 53 (47;59), 54 (48;60) cm, P<0.001 ANOVA. Corresponding arterial oxygen saturation was 97% (96;97), 95% (94;96), 95%(94;96), 92%(90;93), 93%(91;93), P<0.001. Anterior-posterior sway amplitudes were larger at 1630 and 2590 m compared to 490 m, P<0.001. Multiple logistic regression analysis confirmed that higher altitudes (1630 and 2590m) were independently associated with increased COPL when controlled for the order of altitude exposure and age (P=0.001). Exposure to 1630 and 2590m was associated with impaired static postural control even when visual references were available. ClinicalTrials.gov NCT01130948.
    Full-text · Article · Feb 2015 · PLoS ONE

Publication Stats

4k Citations
1,056.64 Total Impact Points

Institutions

  • 1997-2015
    • University of Zurich
      • • Center for Integrative Human Physiology
      • • Internal Medicine Unit
      • • Ophthalmology Unit
      • • Pneumologie
      Zürich, Zurich, Switzerland
  • 1990-2015
    • Schulthess Klinik, Zürich
      Zürich, Zurich, Switzerland
  • 1997-2014
    • University Hospital Zürich
      Zürich, Zurich, Switzerland
  • 2008
    • Universitätsspital Basel
      Bâle, Basel-City, Switzerland
  • 2006
    • Universität Basel
      Bâle, Basel-City, Switzerland