Openobex 1.3 For Mac
Minimum alveolar concentration or MAC is the concentration of a vapour in the alveoli of the lungs that is needed to prevent movement (motor response) in 50% of subjects in response to surgical (pain) stimulus. MAC is used to compare the strengths, or potency, of anaesthetic vapours.[1] The concept of MAC was first introduced in 1965.[2]
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MAC actually is a median value, not a minimum as term implies. The original paper proposed MAC as the minimal alveolar concentration,[3] which was shortly thereafter revised to minimum alveolar concentration.[4] A lower MAC value represents a more potent volatile anesthetic.
Other uses of MAC include MAC-BAR (1.7-2.0 MAC), which is the concentration required to block autonomic reflexes to nociceptive stimuli, and MAC-awake (0.3-0.5 MAC), the concentration required to block voluntary reflexes and control perceptive awareness.
Formal definition[edit]
The MAC is the concentration of the vapour (measured as a percentage at 1 atmosphere, i.e. the partial pressure) that prevents patient movement in response to a supramaximal [5] stimulus (traditionally a set depth and width of skin incisions) in 50% of subjects. This measurement is done at steady state (assuming a constant alveolar concentration for 15 minutes), under the assumption that this allows for an equilibration between the gasses in the alveoli, the blood and the brain. MAC is accepted as a valid measure of potency of inhalational general anaesthetics because it remains fairly constant for a given species even under varying conditions.
Meyer-Overton hypothesis[edit]
The MAC of a volatile substance is inversely proportional to its lipid solubility (oil:gas coefficient), in most cases. This is the Meyer-Overton hypothesis put forward in 1899–1901 by Hans Horst Meyer and Charles Ernest Overton. MAC is inversely related to potency, i.e. high MAC equals low potency.
The hypothesis correlates lipid solubility of an anaesthetic agent with potency (1/MAC) and suggests that onset of anaesthesia occurs when sufficient molecules of the anaesthetic agent have dissolved in the cell's lipid membranes, resulting in anaesthesia. Exceptions to the Meyer-Overton hypothesis can result from:
- convulsant property of an agent
- specific receptor (various agents may exhibit an additional effect through specific receptors)
- co-administration of Alpha2 agonists (dexmedetomidine) and/or opioid receptor agonists (morphine/fentanyl) can decrease the MAC[6][7]
- Mullin's critical volume hypothesis
- Positive modulation of GABA at GABAA receptors by barbiturates or benzodiazepines
Factors affecting MAC[edit]
Certain physiological and pathological states may alter MAC. For example, MAC increases with hyperthermia and hypernatremia. interestingly, human subjects with red hair have also been found to have increased MAC. Conversely, anemia, hypercarbia, hypoxia, hypothermia, hypotension (MAP < 40 mmHg), and pregnancy seem to decrease MAC. Duration of anesthesia, gender, height and weight seem to have little effect on MAC.
Age has been shown to affect MAC. MAC begins to rise at one month of age with a peak at approximately 6 months of age. There is a subsequent steady decline in MAC with increasing age, with the exception of another peak during puberty.[4] There is a linear model that describes the change in MAC of approximately 6% per decade of age.
Medications, illicit drugs, and prior substance use history have also been found to affect MAC. For example, acute use of amphetamines, cocaine, ephedrine, and chronic use of alcohol increase MAC. Whereas, administration of propofol, etomidate, barbiturates, benzodiazepines, ketamine, opiates, local anesthetics, lithium, verapamil, and alpha 2-agonists (dexmedetomidine, clonidine) decrease MAC. Acute alcohol intoxication and chronic amphetamine use have also been found to decrease MAC.
MAC values are additive. For instance, when applying 0.3 MAC of drug X and 1 MAC of drug Y the total MAC achieved is 1.3 MAC. In this way nitrous oxide is often used as a 'carrier' gas to decrease the anesthetic requirement of other drugs.
Common MAC values[edit]
Values are known to decrease with age and the following are given based on a 40-year-old (MAC40):[8]
- Nitrous oxide - 104 [8]
- Xenon - 72 [8]
- Desflurane - 6.6 [8]
- Ethyl Ether - 3.2
- Sevoflurane - 1.8 [8]
- Enflurane - 1.63 [8]
- Isoflurane - 1.17 [8]
- Halothane - 0.75 [8]
- Chloroform - 0.5
- Methoxyflurane - 0.16
References[edit]
- ^'Policy: Ban on Use of Ether'. Laboratory Animal Science Center. Archived from the original on 2008-06-09. Retrieved 2008-11-10.
- ^Eger EI, Saidman LJ, Brandstater B (1965). 'Minimum alveolar anesthetic concentration: a standard of anesthetic potency'. Anesthesiology. 26 (6): 756–63. doi:10.1097/00000542-196511000-00010. PMID5844267.
- ^Merkel, Giles; Eger, Edmond I. (1963-05-01). 'A Comparative Study of Halothane and Halopropane AnesthesiaIncluding Method for Determining Equipotency'. The Journal of the American Society of Anesthesiologists. 24 (3): 346–357. doi:10.1097/00000542-196305000-00016. ISSN0003-3022. PMID13935000.
- ^ abEger, Edmond I.; Saidman, Lawrence J.; Brandstater, Bernard (1965-11-01). 'Minimum Alveolar Anesthetic ConcentrationA Standard of Anesthetic Potency'. The Journal of the American Society of Anesthesiologists. 26 (6): 756–763. doi:10.1097/00000542-196511000-00010. ISSN0003-3022. PMID5844267.
- ^Miller ANESTHESIOLOGY
- ^* Daniel M, Weiskopf RB, Noorani M, Eger EI (January 1998). 'Fentanyl augments the blockade of the sympathetic response to incision (MAC-BAR) produced by desflurane and isoflurane: desflurane and isoflurane MAC-BAR without and with fentanyl'. Anesthesiology. 88 (1): 43–9. doi:10.1097/00000542-199801000-00009. PMID9447854.
- ^Katoh T, Kobayashi S, Suzuki A, Iwamoto T, Bito H, Ikeda K (February 1999). 'The effect of fentanyl on sevoflurane requirements for somatic and sympathetic responses to surgical incision'. Anesthesiology. 90 (2): 398–405. doi:10.1097/00000542-199902000-00012. PMID9952144.
- ^ abcdefgh* Nickalls, R. W. D., & Mapleson, W. W. (August 2003). 'Age-related iso-MAC charts for isoflurane, sevoflurane, and desflurane in man'. British Journal of Anaesthesia. 91 (2): 170–4. doi:10.1093/bja/aeg132. PMID12878613.CS1 maint: multiple names: authors list (link)
1.3
Legal notice
OpenOBEX is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with OpenOBEX. If not, see <http://www.gnu.org/>.
Introduction
This library tries to implement a generic OBEX Session Protocol. It does not implement the OBEX Application FrameWork.When you read this it's very useful to have a copy of the OBEX specification. It is available for download on IrDA's website http://www.irda.org. Make sure you have obex.h and obex_const.h too. You might also find the OpenOBEX test-apps useful.
Programming the library
Preparations
To be able to use the OpenOBEX API you must include the file openobex/obex.h.First of all you must create an OBEX instance by calling OBEX_Init. In this call you specify what transport you want to use, an event callback, and optional flags. OBEX_Init will return a handle which shall be passed to almost all other functions.
To let the parser do some work you must call OBEX_HandleInput. It will block for the specified timeout if there is no data to read. You can call OBEX_GetFD if you want to do select() yourself.
The event callback
The event callback shall be a function with the obex_event_t prototype:Arguments:
- handle : OBEX handle
- obj : OBEX object
- mode : OBEX_CLI for client event or OBEX_SRV, for server event
- event : The event. See obex_const.h for possible events.
- obex_cmd : Command if any (depending on event type)
- obex_rsp : Response if any (depending on event type)
To this function events from the library will be passed to you, for example when an operation finishes. OBEX_SetUserData and OBEX_GetUserData are useful if you need to access your own private data from inside the event callback.
Client Operations
First of all you must connect the transport using OBEX_TransportConnect or one of- FdOBEX_TransportSetup.
When the transport is connected you shall most likely also send an OBEX Connect, to let the library negotiate MTU etc. OBEX Connect is sent as any other OBEX command.
When you are done sending your requests you shall end by sending an OBEX Disconnect request and then call OBEX_TransportDisconnect.
To send a request to you must first create an OBEX Object by calling OBEX_ObjectNew with the command opcode as argument. Next you add headers to it using OBEX_ObjectAddHeader. Finally you send away the request using OBEX_Request.
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When the request has finished you'll get an OBEX_EV_REQDONE event. You can get any headers sent in response (like in a OBEX Get) by calling OBEX_ObjectGetNextHeader.
A Put would look something like this:
OBEX Put example
Server Operations
To act as a server you must first tell the transport to receive incoming connections via the function OBEX_ServerRegister. When an incoming connection is coming you'll get an OBEX_EV_ACCEPTHINT event. If you ignore this event no more incoming connections will be accepted, but if you call OBEX_ServerAccept you'll get back a new OBEX handle and the old handle will still be listening to connections.Openobex 1.3 For Mac Download
When an incoming request comes you'll first get an OBEX_EV_REQHINT event. The supplied OBEX Object is allocated by the library so you do not need to create it yourself.
The OBEX_EV_REQHINT event comes before the parser start receiving the request, so you can cancel requests that your application does not support early.
Set the response to the request using OBEX_ObjectSetRsp.
You can tell the parser to deliver the body-header as a stream when this event comes using OBEX_ObjectReadStream.
When the request is received you'll get an OBEX_EV_REQ event. Get the headers from the object by calling OBEX_ObjectGetNextHeader. You can now change the response if you decide to reject the request. Add any headers you want in the response here too.
When your response is successfully sent you'll get an OBEX_EV_REQDONE event.
After you have received and answered an OBEX Disconnect request you shall call OBEX_TransportDisconnect.
Event callback of a typical server
API Reference
See: lib/obex.c, include/openobex/obex.h, include/openobex/obex_const.h.
Authors and Contact
Authors and major contributors:- Dag Brattli <dagb@cs.uit.no>
- Pontus Fuchs <pontus.fuchs@tactel.se>
- Jean Tourrilhes <jt@hpl.hp.com>
- Marcel Holtmann <marcel@holtmann.org>
- Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
- Christian W. Zuckschwerdt <zany@triq.net>
- Herton Ronaldo Krzesinski <herton@conectiva.com.br>
- Alex Kanavin <ak@sensi.org>
- Johan Hedberg <johan.hedberg@nokia.com>
- Hendrik Sattler <post@hendrik-sattler.de>
See: