移動通信在多功能遠程醫(yī)療保健系統(tǒng)中的應用外文翻譯@中英文翻譯@外文文獻翻譯

第 1 頁 共 20 頁 移動通信在多功能遠程醫(yī)療保健系統(tǒng)中的應用 摘要： 本論文主要研究方向是對遠程醫(yī)療和家庭監(jiān)測提供有效的緊急措施?？赡艹霈F(xiàn)緊急病例的場所很多，常見的有救護車，鄉(xiāng)村衛(wèi)生所及其它偏遠醫(yī)療場所，比如船在廣闊的海面航行時也是一個很普通的可能的緊急醫(yī)療場所的例子，不過我們監(jiān)測的重點是醫(yī)療遙感監(jiān)測和家庭遠程醫(yī)療。為了滿足上述不同領域的發(fā)展需求，我們設計了一個兼具實時、儲存和轉送功能的設備，該設備由一個基本單元和一個遠程醫(yī)療單元組成。一個完整的系統(tǒng)可以用于在救護車、鄉(xiāng)村衛(wèi)生所和輪船上處理緊急醫(yī)療事故，只需在緊急情況處安裝一個 可移動的遠程醫(yī)療單元，而在醫(yī)院專家處安裝一個基本單元；還可加強重病特別護理的防范工作，給重點護理組的醫(yī)生安裝一個基本可移動單元，同時遠程醫(yī)療單元仍在重點護理病人所在地，這樣就可實現(xiàn)對家庭的無線監(jiān)測，通過安裝遠程醫(yī)療單元在病人的家里，而基本單元在醫(yī)院或者是醫(yī)生的辦公室。該系統(tǒng)可傳輸重要的生物信號包括病人的肖像。而傳輸工作可通過 GSM 移動網(wǎng)絡系統(tǒng)、衛(wèi)星連接系統(tǒng)或那些較清晰的舊式電話系統(tǒng)進行。用這個裝置，在處理突發(fā)事故或遠程醫(yī)療事故時，一個專業(yè)醫(yī)生通過信息處理可以“移動”到病人所在地，從而指導非專業(yè)人員。為了保護 和存儲在遠程醫(yī)療過程中相互交換的所有數(shù)據(jù)，我們又開發(fā)了一個咨詢單元，使用多媒體資料庫存儲和管理系統(tǒng)收集的數(shù)據(jù)。該系統(tǒng)技術上已被多個無線電通訊方法所檢測，另外它已在三個不同國家臨床試驗，使用的是標準醫(yī)學協(xié)議。 背景 遠程醫(yī)療就是衛(wèi)生保健的傳遞及一段距離內使用無線電通信手段實現(xiàn)醫(yī)學知識的共享。所以，遠程醫(yī)療的目的是為了給人手不足的偏遠地區(qū)提供專家級的衛(wèi)生保健，通過現(xiàn)代化通信和信息知識提供先進的緊急醫(yī)療措施。遠程醫(yī)療的概念是大約 30 年前隨著一些現(xiàn)在很普通的技術，比如電話、傳真機等提出的。目前，遠程醫(yī)療系統(tǒng)包括的工 藝技術有交互式視頻、高清晰度監(jiān)視器、高速互聯(lián)網(wǎng)和交換系統(tǒng)及高速無線電通信含纖維光學和衛(wèi)星。 實時又專業(yè)化的醫(yī)學治療可以很大地提高人手不足的鄉(xiāng)村、偏遠地區(qū)的衛(wèi)生保健服務。有效的突發(fā)病例遠程醫(yī)療措施和家庭監(jiān)測方案是我們這個課題主要討論的范第 2 頁 共 20 頁 圍。在很多各種各樣的研究里，這個課題都是至關重要的。盡管救護車、鄉(xiāng)村衛(wèi)生所還有航海的輪船都可能發(fā)生緊急病例，但我們監(jiān)測的重點是醫(yī)療遙感勘測和后來的遠程家庭醫(yī)療。在緊急病例中必須進行立即治療，最近的調查表明入院前早期而又專業(yè)化的病人護理有利于病人的存活，尤其是嚴重的頭部損傷、脊髓 和內臟損傷，為了病人以后的康復，處理病人的手段至關重要。 我們可以看看過去的車輛事故統(tǒng)計：在 1997 年，美國報道的 6753500 事故中有42000 人喪身， 2182660 個司機， 1125890 個乘客受傷；歐洲同樣時期有 50000 個人因撞車而喪身，而 50 萬人嚴重受傷；另外 1997 年，在希臘一個國家有高達 1/3 的人是因撞車而死， 2500 個致命傷害中 77.4受傷時遠離有能力的衛(wèi)生保健機構，所以耗費了很長一段時間。此外，同樣的調查表明 66的死者是在死前最近的 24 小時喪身的。 減小這種事故的死亡率是完全可能的，可通 過采用一些病人可更好地進行院前護理、監(jiān)測的方法和策略。療養(yǎng)監(jiān)測也可解決病人突發(fā)情況，重點就在于醫(yī)院對重點護理組的病人進行持續(xù)的監(jiān)控，同時把監(jiān)控信息隨時隨地傳給能夠勝任的醫(yī)生。這樣，負責的醫(yī)生就的 24 小時掌握病人情況，即使不在場時也可通過先進的無線電通信手段提供重要的咨詢，換句話說，視頻監(jiān)控是完全可行的。 方法 遠程醫(yī)療系統(tǒng)的發(fā)展趨勢 由上所述，本論文的研究范圍是設計并實現(xiàn)一個綜合的醫(yī)療系統(tǒng)，該系統(tǒng)可以處理不同距離醫(yī)療系統(tǒng)的需要，尤其表現(xiàn)在以下幾方面： 給救護車，鄉(xiāng)村衛(wèi)生所（或其他偏遠的衛(wèi)生機構）和航海的輪船 提供緊急醫(yī)療措施 實現(xiàn)對重點護理病人的監(jiān)測 提供家庭護理，尤其是那些遭受慢性或永久性疾病的人（像心臟?。?，換句話說，我們研究的多功能系統(tǒng)由兩個主要部分組成： a. 遠程醫(yī)療單元（它可以是手提式電腦或其它） 第 3 頁 共 20 頁 基本單元或醫(yī)生單元（它也可是手提式電腦或其它，一般都位于中心醫(yī)院里 面 圖一描述了系統(tǒng)的總體體系機構，系統(tǒng)的每個不同的應用即遠程醫(yī)療單元位于病人所在處，而基本單元（或是叫醫(yī)生單元）即接收和監(jiān)測病人的生理信號及肖像處。遠程醫(yī)療裝置負責收集病人的資料（生理信號和肖像），然后自動把檢測到的信號傳送到基本單元?；締卧?一組用戶指令軟件組成，運用這套指令 可以接收遠程醫(yī)療裝置的資料、反饋信息及把重要信息存儲在地方資料室。該系統(tǒng)應用很廣泛 (每次只須稍作改變），可滿足現(xiàn)代衛(wèi)生保健的發(fā)展需求。 在系統(tǒng)技術實現(xiàn)以前，上述遠程醫(yī)療系統(tǒng)應用的總設想應根據(jù)目前的發(fā)展趨勢和需求而制定，只有這樣，在設計和發(fā)展過程中，才能把諸多因素都考慮進去，所以才能在任何環(huán)境和情形下達到最大的適用性和可用性。表一提供了這個總思路的結構，同時兼顧了一系列可影響遠程醫(yī)療的標準（如價格、輕便性、自治性、裝置的重量和大小、計算機、攝像機的類型和質量、所采用的通訊方 法），除此之外遠程醫(yī)療的應用還可通過其它標準檢驗，像安全需要，傳輸類型（連續(xù)地存儲和轉送），心電圖要求等。這些在系統(tǒng)總體技術描述中將作詳細說明。 系統(tǒng)設計和技術實現(xiàn) 由上述可知，系統(tǒng)由兩個獨立模塊組成（圖一）： a)一個位于病人所在地，叫做遠程醫(yī)療單元。 b)另一個位于醫(yī)生所在地，叫做基本單元。醫(yī)生在緊急病例或檢測一個偏遠地方病人時可使用該系統(tǒng)。 系統(tǒng)的設計和實現(xiàn)都建立在對用戶要求的詳細分析和對系統(tǒng)功能的具體反應的基礎上。而研究主要以遠程醫(yī)療項目所經(jīng)歷的過程為基礎，像救護車和急救 112，它們使用遠程醫(yī)療功能性裝 置的功能原型已經(jīng)建立了，且通過了初步評估。通過這些具體實踐，我們已經(jīng)定相了解了實現(xiàn)遠程醫(yī)療裝置的需要，這將進一步促進我們形成一個靈活的體系結構，可用于需要信息傳輸?shù)木o急病例或者是監(jiān)測病例。 遠程醫(yī)療單元負責從易發(fā)地帶收集和傳輸生理信號和病人的肖像，而醫(yī)生單元負責接收和顯示輸入數(shù)據(jù)。兩個場所間的信息流（分層描述）如圖二所示。 a) 遠程醫(yī)療單元 遠程醫(yī)療單元主要包括四個模塊，生理信號獲得模塊，負責接收生理信號；數(shù)第 4 頁 共 20 頁 碼相機模塊負責捕獲圖像；處理部件大多是私人計算機；通訊模塊（ GSM、衛(wèi)星或光學地面模擬器）。 所收集的病 人生理信號（然后傳送到基本單元）主要有： 心電圖，由病人所用的監(jiān)視器決定 心跳率 無入侵血壓 入侵血壓 體溫 肺活量 所使用的計算機由遠程應用的類型決定（遠程醫(yī)療單元所發(fā)揮的作用），如表一所示， a)要求系統(tǒng)自動化，形狀小的，一臺像東芝， 100ct 的筆記本電腦即可，較輕便的機器裝置如圖 3 所示。 b)要求半自動，大小不限的，采用典型的奔騰處理機即可。c)而那些不要求自動化，輕便及大小的，一般的臺式機即可選用。 遠程醫(yī)療單元的控制是完全自動化的。遠程醫(yī)療單元用戶要做的僅僅是把生理信號檢測器連接到病人，然后打開計算機 。計算機將自動連接到基本單元。盡管基本單元幾乎控制了系統(tǒng)的所有操作，遠程醫(yī)療單元用戶仍需掌握一部分操作指令，這樣當系統(tǒng)處于偏遠衛(wèi)生所或輪船上時，兩個地方的人就可對話了。 b) 基本單元（或醫(yī)生單元） 基本單元主要由一臺接有調制解調器的精密計算機組成，它的作用主要是負責數(shù)據(jù)交換。另外，基本單元的計算機還負責顯示遠程醫(yī)療單元的輸入信號。當一個專家使用醫(yī)院以外的基本單元時，比如在重病特別護理病房，由圖一用一臺 GSM 的筆記本電腦或一臺裝有 POTS 調制解調的臺式機就可。而當基本單元位于醫(yī)院里時，只需一臺連接到醫(yī)院信息網(wǎng)絡并 裝有 POTS 調制解調的臺式機。專家們就可把它作為一個處理終端。 通過基本單元，用戶可以完全控制遠程醫(yī)療端。用戶還能夠監(jiān)測與客戶端（遠程醫(yī)療單元）的連接狀態(tài)，發(fā)送像圖四那樣的操作模式（生理信號和圖像）到遠程醫(yī)療第 5 頁 共 20 頁 單元。只要基本單元連接到醫(yī)院局域網(wǎng)，用戶可選擇連接到任何一個遠程醫(yī)療單元，如圖五所示基本單元的入網(wǎng)用戶可以選擇連接到任何一個遠程醫(yī)療單元，入網(wǎng)單元可以是重點護理組的遠程醫(yī)療單元或通過電話線上網(wǎng)的遠距離移動用戶單元。 基本單元用戶可以監(jiān)測來自遠程醫(yī)療端的生理或圖像信號，而且也能夠一直與病人進行交談。該單元 可完全控制遠程醫(yī)療部分。醫(yī)生可以發(fā)送所有可能的命令來獲取圖像和生理信號，圖 6 顯示了一個典型的生理信號接收窗口（持續(xù)操作）。 當系統(tǒng)操作圖像模塊時，醫(yī)生可以在圖像上加些注解，然后把加注解后的圖像發(fā)送到遠程醫(yī)療端，遠程醫(yī)療端的用戶也可以把接收到的信息再加上注解，然后反饋回基本單元處。 當系統(tǒng)操作生理信號模塊時（如圖 6 所示），對重要生理信號的傳輸方法有兩種，連續(xù)傳輸、儲存和轉送傳輸?shù)姆椒ā２捎檬裁捶椒ㄈQ于所傳輸?shù)男碾妶D的波形通道和無線通路的數(shù)據(jù)傳輸率。持續(xù)操作時，基本端用戶可以向遠程醫(yī)療監(jiān)測端發(fā)送指令對波形進行 測量，如血壓；用戶也可暫停輸入心電圖。 c) 技術約束 可行性 生理信號傳輸 不僅是生理信號，監(jiān)測的信息像警鈴或監(jiān)測到的狀況也需從遠程醫(yī)療端傳輸?shù)交径?， ECG 波形和 SPO2 或 CO2 波形（若可獲得）是連續(xù)的傳輸信號。對所有的監(jiān)測器， ECG 數(shù)據(jù)以 10bits/樣品或 12bits/樣品進行采樣，采樣率是 200 樣品 /s，所以對一個 ECG 通道相當于是 2000bits/s 或 2400bits/s.SPO2 或 CO2 波形是以 10bits/樣品取樣，取樣率是 100 樣品 /s，所以一個通道就是 1000bits/s。最新監(jiān)測數(shù)據(jù)是以 1 次 /s 進行刷新，所以傳輸少量數(shù)據(jù)大約可以達到 200bits/s,系統(tǒng)使用的所有監(jiān)測器可以提供收集到的信號的數(shù)字輸出量。 圖像傳輸 遠程醫(yī)療端數(shù)碼相機所能捕獲的圖像是 320*240 像素，采用的是 JPEG 進行壓縮，最終數(shù)據(jù)大約是 5-6kB，取決于使用 JPEG 的壓縮率。 傳輸率 第 6 頁 共 20 頁 信號是通過 GSM、衛(wèi)星或 POTS 傳輸?shù)?。系統(tǒng)技術測試使用的 GSM 網(wǎng)絡，目前允許的數(shù)據(jù)傳輸率達到了 9600bps（但處于正常的操作狀態(tài)下），使用高速環(huán)繞交換數(shù)據(jù)時可達到 43200bps.衛(wèi)星連接傳輸率取決于儀器和衛(wèi)星系統(tǒng)的使用場合；大概范 圍是 2400bps 到 64000bps。使用不同種類的衛(wèi)星系統(tǒng)會增加儀器的價錢和用戶的開銷。像我們這種情況使用 INMARAS 電話系統(tǒng)即可，而數(shù)據(jù)傳輸率僅僅是 2400bps，但儀器便宜，開銷少。 POTS 可以達到的數(shù)據(jù)傳輸率是 56000bps，所以它能夠支持連續(xù)而又快速的信息傳輸（如表二所示）。 通過無線通訊傳輸實際所能達到的數(shù)據(jù)傳輸率從來不會超過理論值，而實際數(shù)據(jù)傳輸率取決于系統(tǒng)使用的地區(qū)和時間。傳輸生理信號有兩種方法實時傳輸，連續(xù)地將信號從客戶端傳輸?shù)郊曳掌?；儲存和轉發(fā)傳輸，信號提前獲得并儲存在客戶端，然后 作為文件傳輸給服務器。采取什么方法主要取決于所使用的無線電通訊的最大數(shù)據(jù)傳輸率和不同情況下生理信號監(jiān)測器的數(shù)字輸出量。 最后的結果是 多功能 電子醫(yī)療系統(tǒng) ,是一個能在不同的應用領域中被采用的靈活的體系結構，該系統(tǒng)已通過了很多醫(yī)療設備和無線通信設備的試驗。本論文所針對的對象是鄉(xiāng)村衛(wèi)生所、救護車或航海的輪船。 數(shù)據(jù)傳輸使用的是 TCP/IP網(wǎng)絡協(xié)議，網(wǎng)絡傳輸數(shù)據(jù)使用 TCP/IP協(xié)議簡單且容易，又具有高帶寬、低誤碼率。要傳輸 n 字節(jié)的數(shù)據(jù)塊，使用 TCP/IP 協(xié)議，需在報頭另加 55 字節(jié)。在傳輸少量數(shù)據(jù)的情況下，這 加額外增加大量數(shù)據(jù)（例如，當傳輸 10 字節(jié)時，網(wǎng)絡將自動增加至 65 字節(jié)）。 當傳輸?shù)臄?shù)據(jù)流大小大于最大允許的傳輸單元時，這個數(shù)據(jù)流將分裂成幾個較小的數(shù)據(jù)包，每個包都和允許的最大傳輸單元一樣大，而達到目的地時，所有分裂的包將會重新連接；如果其中分裂的任何一個包丟失，將會引起嚴重錯誤。 考慮到數(shù)據(jù)傳輸?shù)纳鲜鰞煞N情況，尤其是那種低帶寬、高差錯率的網(wǎng)絡（像 GSM移動網(wǎng)絡和衛(wèi)星連接）。采用一種充分利用帶寬的方法，使傳輸?shù)臄?shù)據(jù)要么充分大，要么充分小。 為了測量使用 GSM 網(wǎng)絡時 TCP/IP 的執(zhí)行，對不同大小的數(shù)據(jù)塊進行測 試，該測試使用的是 GSM 調制解調器， NOKIA2.0 電話卡。進行試驗時，選擇了從 71 到 479 字節(jié)的數(shù)據(jù)包，數(shù)據(jù)包的大小與發(fā)送的數(shù)據(jù)率成正比，發(fā)送時使用串口 RS232 。數(shù)據(jù)第 7 頁 共 20 頁 包的大小依次有 7.95.143.239.287.335.383.431.455.479 字節(jié)。 由上所述，圖 8 是對數(shù)據(jù)傳輸?shù)臏y量。我們對要選擇的數(shù)據(jù)塊大小的要求是：不給傳輸數(shù)據(jù)加過長的報頭，不會引起數(shù)據(jù)傳輸?shù)姆謮K，不會給信號的傳輸引起很大的時延。經(jīng)多方面考慮，我們選擇的數(shù)據(jù)塊大小是 431 字節(jié)。 結論 我們已經(jīng)開發(fā)了適于遠程醫(yī)療應用的醫(yī)療產(chǎn)品 ，該裝置使用 GSM 移動電話連接，衛(wèi)星連接或 POTS 連接，允許收集和傳輸生理信號、病人的肖像，具有雙向視頻功能。在接收數(shù)據(jù)和與專家交談時，允許用戶在可自由模式下操作，這種先進的人為控制界面提高了系統(tǒng)的功能性。為了在日常健康預防中介紹該系統(tǒng)，通過使用一個可控制的醫(yī)療協(xié)議系統(tǒng)已被臨床試驗。目前，該系統(tǒng)已經(jīng)在兩個不同國家，希臘和塞浦路斯安裝且正在使用。據(jù)現(xiàn)在的發(fā)展情形可以看出系統(tǒng)很有前景，所以為滿足未來需求，激勵著我們不斷發(fā)展和提高該系統(tǒng)。 8 Multi-purpose HealthCare Telemedicine Systems with mobile communication link support E Kyriacou*1,2, S Pavlopoulos1, A Berler1, M Neophytou1, A Bourka1, A Georgoulas1, A Anagnostaki1, D Karayiannis3, C Schizas2, C Pattichis2,A Andreou2 and D Koutsouris1 abstract The provision of effective emergency telemedicine and home monitoring solutions are the major fields of interest discussed in this study. Ambulances, Rural Health Centers (RHC) or other remote health location such as Ships navigating in wide seas are common examples of possible emergency sites, while critical care telemetry and telemedicine home follow-ups are important issues of telemonitoring. In order to support the above different growing application fields we created a combined real-time and store and forward facility that consists of a base unit and a telemedicine (mobile) unit. This integrated system: can be used when handling emergency cases in ambulances, RHC or ships by using a mobile telemedicine unit at the emergency site and a base unit at the hospital-experts site, enhances intensive health care provision by giving a mobile base unit to the ICU doctor while the telemedicine unit remains at the ICU patient site and enables home telemonitoring, by installing the telemedicine unit at the patients home while the base unit remains at the physicians office or hospital. The system allows the transmission of vital biosignals (312 lead ECG, SPO2, NIBP, IBP, Temp) and still images of the patient. The transmission is performed through GSM mobile telecommunication network, through satellite links (where GSM is not available) or through Plain Old Telephony Systems (POTS) where available. Using this device a specialist doctor can telematically move to the patients site and instruct unspecialized personnel when handling an emergency or telemonitoring case. Due to the need of storing and archiving of all data interchanged during the telemedicine sessions, we have equipped the consultation site with a multimedia database able to store and manage the data collected by the system. The performance of the system has been technically tested over several telecommunication means； in addition the system has been clinically validated in three different countries using a standardized medical protocol. Background Telemedicine is defined as the delivery of health care and sharing of medical knowledge over a distance using telecommunication means. Thus, the aim of Telemedicine is to provide expert-based health care to understaffed remote sites and to provide advanced 9 emergency care through modern telecommunication and information technologies. The concept of Telemedicine was introduced about 30 years ago through the use of nowadays-common technologies like telephone and facsimile machines. Today, Telemedicine systems are supported by State of the Art Technologies like Interactive video, high resolution monitors, high speed computer networks and switching systems, and telecommunications superhighways including fiber optics, satellites and cellular telephony 1. The availability of prompt and expert medical care can meaningfully improve health care services at understaffed rural or remote areas. The provision of effective emergency Telemedicine and home monitoring solutions are the major fields of interest discussed in this study. There are a wide variety of examples where those fields are crucial. Nevertheless, Ambulances, Rural Health Centers (RHC) and Ships navigating in wide seas are common examples of possible emergency sites, while critical care telemetry and Telemedicine home follow-ups are important issues of telemonitoring. In emergency cases where immediate medical treatment is the issue, recent studies conclude that early and specialized pre-hospital patient management contributes to the patients survival 2. Especially in cases of serious head injuries, spinal cord or internal organs trauma, the way the incidents are treated and transported is crucial for the future well being of the patients. A quick look to past car accident statistics points out clearly the issue: During 1997, 6753500 incidents were reported in the United States 3 from which about 42000 people lost their lives, 2182660 drivers and 1125890 passengers were injured. In Europe during the same period 50000 people died resulting of car crash injuries and about half a million were severely injured. Furthermore, studies completed in 1997 in Greece 4, a country with the worlds third highest death rate due to car crashes, show that 77,4 % of the 2500 fatal injuries in accidents were injured far away from any competent healthcare institution, thus resulting in long response times. In addition, the same studies reported that 66% of deceased people passed away during the first 24 hours. The reduction of all those high death rates is definitely achievable through strategies and measures, which improve access to care, administration of pre-hospital care and patient monitoring techniques.Critical care telemetry is another case of handling emergency situations. The main point is to monitor continuously intensive care units (ICU) patients at a hospital and at the same time to display all telemetry information to the competent doctors anywhere, anytime 14. In this pattern, the responsible doctor can be informed about the patients condition at a 24-hour basis and provide vital consulting even if hes not physically present. This is feasible through advanced telecommunications means or in other words via Telemedicine. Methods Trends and needs of Telemedicine systems 10 As mentioned above, scope of this study was to design and implement an integrated Telemedicine system, able to handle different Telemedicine needs especially in the fields of: Emergency health care provision in ambulances, Rural Hospital Centers (or any other remote located health center) and navigating Ships Intensive care patients monitoring Home telecare, especially for patients suffering from chronic and /or permanent diseases (like heart disease). In other words we determined a Multi-purpose system consisting of two major parts: a) Telemedicine unit (which can be portable or not portable depending on the case) and b) Base unit or doctors unit (which can be portable or not portable depending on the case and usually located at a Central Hospital). Figure 1 describes the overall system architecture. In each different application the Telemedicine unit is located at the patients site, whereas the base unit (or doctors unit) is located at the place where the signals and images of the patient are sent and monitored. The Telemedicine device is responsible to collect data (biosignals and images) from the patient and automatically transmit them to the base unit. The base unit is comprised of a set of user-friendly software modules, which can receive data from the Telemedicine device, transmit information back to it and store important data in a local database. The system has several different applications (with small changes each time), according to the current healthcare provision nature and needs. Before the systems technical implementation, an overview of the current trends and needs in the aforementioned Telemedicine applications was made, so that the different requirements are taken into account during design and development, thus ensuring 11 maximum applicability and usability of the final system in distinct environments and situations. Table 1 provides the results of this overview, which was done towards a predefined list of criteria that usually influence a Telemedicine application implementation (cost, portability, autonomy, weight and size of Telemedicine device, type and quality of PC and camera, communication means used). Besides the above, the Telemedicine applications can be examined towards other criteria, like for example security needs, transmission type (continuos, store & forward) needs, ECG leads required (3 or 12 leads), etc. These last are examined in more detail in the next paragraph, where the overall technical description of the system is provided. System design and technical implementation As mentioned above, the system consists of two separate modules (Figure 1): a) the unit located at the patients site called Telemedicine unit and b) the unit located at doctors site called Base Unit. The Doctor might be using the system either in an Emergency case or when monitoring a patient from a remote place. The design and implementation of the system was based on a detailed user requirements analysis, as well as the corresponding system functional specifications. The study was mainly based on the experience of Telemedicine projects named AMBULANCE 22 and Emergency 112 33 where functional prototypes of a device with emergency Telemedicine functionalities was built and extensively evaluated. Through these project we had phased the need to implement a telemedicine device, which would facilitate a flexible architecture and could be used in several emergency or monitoring cases that have simiral needs of information transmition. 12 The Telemedicine unit is responsible for collecting and transmitting biosignals and still images of the patients from the incident place to the Doctors location while the Doctors unit is responsible for receiving and displaying incoming data. The information flow (using a layered description) between the two sites can be seen in Figure 2. a) Telemedicine Unit The Telemedicine unit mainly consists of four modules, the biosignal acquisition module, which is responsible for biosignals acquisition, a digital camera responsible for image capturing, a processing unit, which is basically a Personal Computer, and a communication module (GSM, Satellite or POTS modem). The biosignal acquisition module was designed to operate with some of the most common portable biosignal monitors used in emergency cases or in Intensive care Units such as a) CRITIKON DINAMAP PLUS Monitor Model 8700/9700 family of monitors, b) PROTOCOL-Welch Allyn Propaq 1xx Vital Signs Monitor, c) PROTOCOL-Welch Allyn Propaq Encore 2xx Vital Signs Monitor. The biosignals collected by the patient (and then transmitted to the Base Unit) are: ECG up to 12 lead, depending on the monitor used in each case. Oxygen Saturation (SpO2). Heart Rate (HR). Non-Invasive Blood Pressure (NIBP). Invasive blood Pressure (IP). Temperature (Temp) Respiration (Resp) 13 The PC used depends on the type of the Telemedicine application (role of the Telemedicine unit). As shown in Table 1: a) in cases where the autonomy and small size of the system are important (mainly in ambulances), a sub notebook like Toshiba libretto 100 ct portable PC is used, a picture of a portable device is shown in Figure 3 b) in cases where we need some autonomy but size is not considered an important element a Typical Pentium portable PC is used； c) in cases where we do not necessarily need autonomy, portability and small system size, a Typical Pentium Desktop PC is used. The control of the Telemedicine unit is fully automatic. The only thing the telemedicine unit user has to do is connect the biosignal monitor to the patient and turn on the PC. The PC then performs the connection to the base unit automatically. Although the base unit basically controls the overall system operation, the Telemedicine unit user can also execute a number of commands. This option is useful when the system is used in a distance health center or in a ship and a conversation between the two sites takes place. b) Base Unit (or Doctors Unit) The base unit mainly consists of a dedicated PC equipped with a modem, which is responsible for data interchange. In addition the base unit pc is responsible for displaying incoming signals from the Telemedicine unit. When an expert doctor uses the base unit located outside the hospital area (like in the Intensive Care Room application see Figure 1, a portable PC equipped with a GSM modem or a desktop PC equipped with a POTS modem is used. When the base unit is located in the hospital, a desktop PC connected to the Hospital Information Network (HIS) equipped with a POTS modem can additionally be used； the expert doctor uses it as a processing terminal. Through the base unit, user has the full control of the telemedicine session. The user is able to monitor the connection with a client (telemedicine unit), send commands to the telemedicine unit such as the operation mode (biosignals or images) Figure 4. In cases were the base station is connected to a Hospital LAN the user can choose to which of the 14 telemedicine units to connect to, as shown in Figure 5 the user of the base unit is able to choose and connect to anyone of the telemedicine units connected on the network. The units connected on the network can be ICU telemedicine units or distance mobile telemedicine units connected through phone lines. The Base Units user can monitor biosignals or still images coming from the Telemedicine unit, thus keeping a continuous online communication with the patient site. This unit has the full control of the Telemedicine session. The doctor (user) can send all possible commands concerning both still image transmission and biosignals transmission. Figure 6 presents a typical biosignal-receiving window (continuous operation). 15 c) Technical Constraints Feasibility Biosignals transmission 16 Along with biosignals, information concerning the monitor, such as the alarms or the monitor status, is transmitted from the Telemedicine unit to the base unit. The ECG waveform and SpO2 or Co2 Waveform (where available) is the continuous signals transmitted, trends are transmitted for the rest of data. ECG data are sampled at a rate of 200 samples/sec by 10 bits/sample or 12 bits/sample, for all monitors used, thus resulting in a generation of 2000 bits/sec and 2400 bits/sec for one ECG channel. SpO2 and Co2 waveforms are sampled at a rate of 100 samples/sec by 10 bit/sample； thus resulting in a generation of 1000 bits/sec for one channel. Trends for SpO2, HR, NIBP, BP, Temp and monitor data are updated with a refresh rate of one per second, thus adding a small fraction of data to be transmitted approximately up to 200 bits/sec. All biosignals monitors used with the system can provide digital output of the collected signals 36-38. Image transmission Images captured by the Telemedicine units camera have resolution 320 240 pixel and are compressed using the JPEG compression algorithm； the resulting data set is approximately 56 KB depending on the compression rate used for the JPEG algorithm 39. Transmission rate The signals transmission is done using GSM, Satellite and POTS links. For the time being, the GSM network that the system was technically tested on； allows transmission of data up to 9600 bps (when operating on the normal mode) and is able to reach up to 43200 bps when using the HSDC (High Speed Circuit Switched Data). The satellite links transmission rate depends on the equipment and the satellite system used in each case； it has a range from 2400 bps up to 64000 bps. The use of different satellite systems can increase the cost of equipment and cost of use； in our case we had used an INMARSAT-phone Mini-m system which can transmit data only up to 2400 bps, but has low equipment and use cost. Plain Old Telephony System (POTS) allows the transmission of data using a rate up to 56000 bps, thus enabling the continuous and fast information transmission (Table 2). The practical maximum data transfer rate over telecommunication means is never as high as the theoretical data transfer rate. Practical data rates depend on the time and the area where the system is used. Biosignals data transmission can be done in two ways: real time transmission where a continuous signal is transmitted from client to server or store and forward transmission where signals of a predefined period of time are stored in the client and transmitted as files to server. It mainly depends on the maximum data transfer rate of the telecommunication link used and the digital data output that the biosignal monitor has in each case. 17 Results Discussion The final result is a Multi-purpose Telemedicine system, which facilitates a flexible architecture that can be adopted in several different application fields. The system has been tested and validated for a variety of medical devices and telecommunication means. Results presented in this section are typical for the needs of system use in Rural Health Centers, in Ambulance Vehicles or in a Navigating Ship. Data transmission is done using the TCP/IP network protocol. Transmitting data over TCP/IP is a trivial and easy task when using networks, which have high bandwidth and low error rate. In order to transmit a buffer of n bytes through TCP/IP a header of about 55 bytes is added, this will add a great amount of data especially in cases that we transmit small buffers (e.g. when transmitting a buffer of 10 bytes the network protocol will increase this buffer to 65 bytes). When transmitting a buffer that has size larger than the Maximum Transfer Unit (MTU) this buffer will be fragmented in to smaller packets that each one has the size of the MTU, all small packets will be reconnected when arriving at the destination site； this case will cause problems when one of the fragmentation packets is lost 42 18 Considering the above two cases the transmission of data, especially through networks that have low bandwidth and high error rates (such as GSM mobile network and Satellite Links), has to be done in a way that will utilize the network use as much as possible. The buffers transmitted must have size that want be either too small or too big. In order to measure the performance of TCP/IP over the GSM network several sizes of data buffers had been tested. The tests were performed using GSM modem, Nokia Card Phone 2.0 for the telemedicine unit, and a POTS modem US robotics sportster voice 56 KBPS for the base unit. These two devices support compression protocol V42 bis. In order to perform the tests； buffers from 71 up to 479 bytes were selected； the size of buffers is proportional to the data rate that the Propaq 2xx sends through the RS232 serial port. The packets had sizes: 71, 95, 143, 239, 287, 335, 383, 431, 455, 479 bytes. Using all the above buffers we made some measurements on the bytes that were received and transmitted to and from the base unit of the telemedicine system. Figure 8 shows the results of the bytes transmitted and received from the server unit when having a telemedicine unit connected with GSM to the server. Numbers 1 to 10 represent the size of the buffers used, 1 for the smallest (71 bytes) up to 10 for the largest (479 bytes). The mean value of the bytes transmitted/received per second was recorded for 2 minutes per case. As can be seen transmitting small packets of data cased the transmition of more bytes because of the overhead added on each buffer. The continuous transmition of small buffers also cased some problems on the communication and on the overall telemedicine unit operation； it could stop the operation of the protocol or add some problem when reading data from the medical monitor (too many system resources were used). Having in mind all the above and the measurements of bytes transmitted (Figure 8) we had to select a buffer size that: would not add too much overhead to the transmitted data, would not cause fragmentation of the transmitted buffers and would not add too much delay on real time transmitted signal. Having in mind all the above the selected buffer size used was 431 bytes. Conclusions We have developed a medical device for telemedicine applications. The device uses GSM mobile telephony links, Satellite links or POTS links and allows the collection and transmission of vital biosignals, still images of the patient and bi-directional telepointing capability. The advance man-machine interface enhances the system functionality by allo