En model til simulere klinisk relevant Hypoxi i mennesker
Summary
Hypoxi simulering hos mennesker er normalt udført ved at inhalere hypoxiske gasblandinger. Til denne undersøgelse blev apnø dykkere bruges til at simulere dynamisk hypoxi hos mennesker. Derudover blev fysiologiske ændringer i desaturation og re-mætningskinetik evalueret med non-invasive værktøjer som Near-Infrared-spektroskopi (NIRS) og perifer iltning mætning (SpO 2).
Abstract
In case of apnea, arterial partial pressure of oxygen (pO2) decreases, while partial pressure of carbon dioxide (pCO2) increases. To avoid damage to hypoxia sensitive organs such as the brain, compensatory circulatory mechanisms help to maintain an adequate oxygen supply. This is mainly achieved by increased cerebral blood flow. Intermittent hypoxia is a commonly seen phenomenon in patients with obstructive sleep apnea. Acute airway obstruction can also result in hypoxia and hypercapnia. Until now, no adequate model has been established to simulate these dynamics in humans. Previous investigations focusing on human hypoxia used inhaled hypoxic gas mixtures. However, the resulting hypoxia was combined with hyperventilation and is therefore more representative of high altitude environments than of apnea. Furthermore, the transferability of previously performed animal experiments to humans is limited and the pathophysiological background of apnea induced physiological changes is poorly understood. In this study, healthy human apneic divers were utilized to mimic clinically relevant hypoxia and hypercapnia during apnea. Additionally, pulse-oximetry and Near Infrared Spectroscopy (NIRS) were used to evaluate changes in cerebral and peripheral oxygen saturation before, during, and after apnea.
Introduction
Klinisk relevant akut hypoxi og samtidig hypercapni er for det meste ses hos patienter med obstruktiv søvnapnø syndrom (OSAS), akut luftvejsobstruktion eller under genoplivning. Store begrænsninger inden for OSAS og andre hypoxemiske tilstande indbefatter den begrænsede overførbar viden om patofysiologien afledt af dyreforsøg og at humane modeller er ikke-eksisterende 1. At efterligne hypoxi hos mennesker, har hypoxiske gasblandinger hidtil blevet bruges 2 – 7. Men disse betingelser er mere repræsentative for højtliggende omgivelser end af kliniske situationer, hvor hypoxi generelt ledsages af hyperkapni. For at overvåge vævsoxygenering under hjertestop og genoplivning, har dyreforsøg udført 8 for at undersøge fysiologiske kompenserende mekanismer.
Apnø-dykkere er sunde atleter i stand til at trykke på vejrtrækning impulsder er fremkaldt af lav arteriel oxygenmætning 9 og en øget pCO2 10,11. Vi undersøgte apnø dykkere for at efterligne kliniske situationer med akut hypoksi og samtidig hypercapni 12. Denne model kan anvendes til at evaluere kliniske opsætninger, forbedre den patofysiologiske forståelse af patienter med OSAS eller patologiske vejrtrækning lidelser, og afslører nye muligheder for at studere en potentiel tæller afbalanceringsmekanisme i tilfælde af apnø. Endvidere til forskellige teknikker detektere hypoxi hos mennesker kan testes for gennemførlighed og nøjagtighed i tilfælde af dynamiske hypoksi, som findes i nødsituationer (dvs., luftvejsobstruktioner, laryngospasme eller kan ikke intubere, kan ikke ventilere situationer) eller til at simulere intermitterende hypoxi hos patienter med OSAS.
Noninvasive teknikker til påvisning af hypoxi hos mennesker er begrænsede. Perifer pulsoximetri (SpO 2) er en godkendt værktøj i pre-Hospital og hospitaler til at opdage hypoxi 13. Metoden er baseret på lysabsorption af hæmoglobin. Imidlertid er SpO 2 måling begrænset til perifer arteriel iltning og kan ikke anvendes i tilfælde af pulseless elektrisk aktivitet (PEA) eller centraliseret minimal cirkulation 14. I modsætning hertil kan Near-infrarød spektroskopi anvendes til at bedømme hjernevæv iltmætning (RSO 2) i realtid under PEA, under hæmorrhagisk shock eller efter subarachnoid blødning 15-19. Dens anvendelse er i konstant vækst 20 og metodiske undersøgelser har afsløret en positiv sammenhæng mellem SpO 2 og RSO 2 3,4.
I denne undersøgelse, giver vi en model til at simulere klinisk relevant hypoxi hos mennesker og præsentere en trin-for-trin metode til at sammenligne perifere pulsoximetri og NIRS i tilfælde af de- og re-mætning. Ved at analysere fysiologiske data i tilfælde af enpnea, kan vores forståelse af counter balancing mekanismer forbedres.
Protocol
Representative Results
Discussion
Den samlede apnø tid er primært forårsaget af lunge størrelse og ilt forbrug per minut og påvirket af en persons evne til at modstå vejrtrækningsrefleks forårsaget af stigende pCO2 eller faldende pO 2. Apnø dykkere er uddannet til at maksimere deres ånde-hold varighed og er vant til at gøre det i maksimal inspiration. Derfor tiden indtil hypoxi er påviselige adskiller mellem individer og afhænger af emnet fysiske tilstand og træning status og måske endda variere fra deres daglige sta…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
Special thanks to all volunteers who participated in the original study. The work of L. Eichhorn was supported through a scholarship of the Else-Kröner-Fresenius Foundation. The authors would like to thank Springer, Part of Springer Science+Business Media, for copyright clearance (License Number 3894660871180) and the kind permission of reusing previously published data.
Materials
| SpO2 | Dräger Medical AG&CO.KG | SHP ACC MCABLE-Masimo Set | peripheral SpO2-Monitoring |
| Non Invasive Blood Pressure (NIBP) | Dräger Medical AG&CO.KG | NIBP cuff M+, MP00916 | |
| Electrocardiographic (ECG) | Dräger Medical AG&CO.KG | Infinity M540 Monitor | ECG monitoring |
| Docking station | Dräger Medical AG&CO.KG | M500 Docking Station | connection of M540 to laptop |
| NIRS | NONIN Medical’s EQUANOX | Model 7600 Regional Oximeter System | measuring of cerebral and tissue oxygenation |
| NIRS diodes | EQUANOX Advance Sensor | Model 8004CA | suited for measuring cerebral and somatic oxygen-saturation |
| Laptop | |||
| DataGrabber | Dräger Medical AG&CO.KG | DataGrabber v2005.10.16 | software to synchronize M540 with laptop |
| eVision | Nonin Medical. Inc. | Version 1.3.0.0 | software to synchronize NONIN with laptop |
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