| Popis: |
Izhodišča: Anestezijski dihalni sistem je vmesnik, ki dovaja in odvaja pline med anestezijsko delovno postajo in bolnikom. Cilj študije je bil določiti možne zapore v dihalnem sistemu in kako jih najti z dinamičnim funkcionalnim testiranjem. Predstavili smo analizo retrogradnih pretokov skozi absorber CO2 pri različnih anestezijskih delovnih postajah. V simulacijskem okolju smo izvedli različne scenarije, kjer smo izklopili dihalni balon iz dihalnega sistema. Metode: Eksperimentalno študijo smo izvedli z anestezijsko delovno postajo Dräger Primus s funkcijo razdruževanja svežih plinov, na katero smo priključili simulator bolnika METI HPS. S funkcionalnimi testi, kjer smo pri volumsko nadzorovani ventilaciji primerjali koaksialni dihalni sistem z zaporo in brez zapore. Pri primerih sušenja absorberja smo podrobno izvedli funkcionalno analizo pri odprtem in zaprtem nastavku Y. V simulacijskih scenarijih z izklopljenim dihalnim balonom smo merili časovni potek kisika, dušikovega oksidula in sevoflurana pri različnih pretokih svežega plina (FGF=0,5, 1 ali 2 L/min) in različnimi nosilnimi plini (kisik/zrak in kisik/dušikov oksidul). Rezultati: Zapora notranje cevi koaksialnega dihalnega sistema povzroči dvig največjega tlaka (iz 35 mbar na 70 mbar). Retrogradni pretoki, ki lahko sušijo absorbent najdemo pri delovnih postajah Dräger Cato, Dräger Julian, Dräger Fabius GS in Dräger Primus, pri tem je nastavek Y zaprt. V scenarijih z odklopom dihalnega balona se delež kisika v vdihanem zraku (FIO2) zmanjša iz 57 % na 37 % (FGF=1 L/min nosilni plin=kisik/zrak). Prav tako se v vseh scenarijih zmanjšajo vrednosti dušikovega oksidula in sevoflurana. Zaključki: Poudarjamo, da je v sistemih z razdruževanjem svežih plinov, dihalni balon aktivna komponenta dihalnega sistema med umetno ventilacijo in ima funkcijo zbiralnika plinov. Predlagamo uporabo inspiratorne pavze med dinamičnim testiranjem dihalnega sistema, ko je razlika med sistemom z zaporo in sistemom brez zapore najvišja. Pri sistemih z razdruževanjem svežih plinov se v fazi inspirija pretok svežih plinov preko ventila razdruževanja usmeri v dihalni balon in scenariji iz te serije imajo za posledico hipoksijo in manjšo globino anestezije. Background: Anesthesia breathing system is an interface of medical devices that transports gases between the anesthesia workstation and the patient. The aim of this study was to determine potential obstruction in breathing system and how to identify this obstruction with dynamic functional testing. We provided an analysis of retrograde flow through CO2 absorbers in different anesthesia workstation. In the simulated environment we conducted different scenarios where we disconected breathing bag from breathing system. Methods: The experimental study was performed in vitro on Dräger Primus anesthesia workstation (with fresh gas decoupling system) which was connected to an high-fidelity Human Patient Simulator METI HPS. With functional tests of the volume control ventilation we compared obstructed and unobstructed coaxial breathing system. In cases of the absorbent dessiccation we tried to detail the functional analysis to examines the causes and consequences of closed and open Y-piece. In simulation scenarious with breathing bag disconnection, we measured time-course of oxygen, nitrous oxyde and sevoflurane at variable rates of fresh gas flow (FGF=0.5, 1 or 2 L/min) and at different carier gases (oxygen/air and oxygen/nitrous oxyde). Results: Occlusion of the inner tube of coaxial breathing circuit produces increased peak inspiratory pressures (from 35 mbar to 70 mbar). A retrograde flow of fresh gas causing absorbent desiccation can occur in a Dräger Cato, Dräger Julian, Dräger Fabius GS or Dräger Primus anesthesia workstations with the Y-piece connector closed. In scenarios with disconnected breathing bag, the fraction of inspired oxygen (FIO2) was reduced from 57 % to 37 % (FGF=1 L/min carier gas=oxygen/air). Nitrous oxyde and Sevoflurane was also reduced in all scenarious. Conclusions: It should be pointed out that in fresh gas decoupling systems the reservoir bag is an active component of the breathing system during mechanical ventilation and it functions as a respiratory gas reservoir. We sugested to use the pressure waveform with inspiratory pause, where the difference between obstructed and unobstructed breathing system is maximal. In the fresh gas decoupling system, during the inspiratory phase, the fresh gas flow is diverted into a reservoir bag by a decoupling valve and this series of scenarios results in hypoxia and awareness. |
