- Mac Measurement Arm
- Measure Arm Circumference
- Performance Measure For Machine Learning
- Measure For Mass
- Gps Field Measure 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]
PDF Measure It is an Acrobat plug-in tool. It enables accurate measurement of the distance and angle between two points on a page. To measure a distance, click anywhere on a PDF page to set a. Photo Measures is the most elegant and the easiest way to save measures on your own photos on iPhone and iPad! Architectural Digest - 'Very useful when shopping or meeting with contractors' Tuaw.com - 'It's perfect for your own work around the house, and handy for creating plans to. You can't easily increase font size on a Mac in a specific font setting, but there are two different ways to get it done.; You can, for example, change the resolution of your display to. An iPad Pro 10.5 will measure approximately 10.5 inches when measured diagonally across the screen. The measurement does not include the bezel. If you are measuring, only measure the active part of the screen. Consequently, a 12.9 iPad Pro will measure just under 13 inches when the screen is measured diagonally as shown in the image above.
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
![Dog Dog](https://www.reech.media/wp-content/uploads/2017/01/Shingler-Banners.jpg)
Factors affecting MAC[edit]
Certain physiological and pathological states may alter MAC. For example, MAC increases with hyperthermia and hypernatremia. 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)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Minimum_alveolar_concentration&oldid=985541945'
The Measure app uses augmented reality (AR) technology to turn your device into a tape measure. You can gauge the size of objects, automatically detect the dimensions of rectangular objects, and save a photo of the measurement. And with iPad Pro 12.9-inch (4th generation), iPad Pro 11-inch (2nd generation), iPhone 12 Pro, and iPhone 12 Pro Max, you can measure objects more easily with visible guides, measure a person’s height, and see a history of your measurements.
Before you start
First, make sure that your device's software is up to date. The Measure app works on these devices:
Also make sure that you're in a place with good lighting.
How to take a single measurement
- Open the Measure app, then follow any onscreen instructions that ask you to move your device around. This gives your device a frame of reference for the object you're measuring and the surface it's on. Keep moving your device until a circle with a dot in the center appears.
- Move your device so that the dot is over the starting point of your measurement, then tap the Add button .
- Slowly move your device until the dot is over the ending point of your measurement, then tap the Add button again.
After you take a measurement, you can adjust its starting and ending points. Touch and hold one of the points, then drag it where you want it to go. The measurement changes as you move the point.
Mac Measurement Arm
Save your measurement
While the measurement is displayed, you can tap the number to see it in inches and centimeters. Tap Copy, and the value is sent to your clipboard so you can paste it into another app. Tap Clear to start over.
You can also take a photo that shows the object and its measurement. Just tap the Shutter button , and the photo appears in the lower-left corner of your screen. Tap it to make edits using Markup, or swipe left to save it to your Photos app.
How to take multiple measurements
- After you take the first measurement, move your device to place the dot over another location on or near the object.
- Tap the Add button to start the second measurement, then move your device to place the dot somewhere along the existing measurement.*
- Tap the Add button again and the second measurement appears.
- Repeat these steps to take as many measurements as you'd like.
Tap the Undo button to remove the most recent measurement, or tap Clear to start over.
* Additional measurements must start or end somewhere along an existing measurement. Otherwise, all previous measurements are replaced by the newest one.
Measure a rectangle
Measure Arm Circumference
If your device detects that the object you're measuring is a square or rectangle, it automatically places a measurement box around the object. Tap the Add button and measurements appear for the object's width and length. Move your device slightly, and the object's calculated area appears.
While the measurement is displayed, you can tap the calculated area number to see the length of the diagonal as well as the area in square inches or square meters.
Use the Measure app with iPad Pro 12.9-inch (4th generation), iPad Pro 11-inch (2nd generation), iPhone 12 Pro, and iPhone 12 Pro Max
Performance Measure For Machine Learning
iPad Pro 12.9-inch (4th generation), iPad Pro 11-inch (2nd generation), iPhone 12 Pro, and iPhone 12 Pro Max use the LiDAR Scanner to help you measure objects more quickly and accurately with the Measure app.
Not sure if your device has a LiDAR Scanner? Find out which iPad model you have or which iPhone model you have.
![Measure Measure](/uploads/1/2/4/3/124384592/192292041.jpg)
Measure a person's height
When the Measure app detects a person in the viewfinder, it automatically measures their height from the ground to the top of their head, hat, or hair. You can tap the shutter button to take a photo of the person with their height measurement. Then you can use Markup on the photo, save it, and share it.
Measure For Mass
Use vertical and edge guides
On iPad Pro 12.9-inch (4th generation), iPad Pro 11-inch (2nd generation), iPhone 12 Pro, and iPhone 12 Pro Max, guide lines help you measure the height and straight edges of furniture, countertops, and other objects easily and precisely. Guide lines appear automatically along edges and when making a vertical measurement.
Snap your starting and ending points to the yellow guide line, then tap a measurement to see the expanded information that iPad Pro provides. You can view the measurement's elevation, distance away, angle, and more.
See more granular measurements with Ruler View
Gps Field Measure For Mac
The Measure app on iPad Pro 12.9-inch (4th generation), iPad Pro 11-inch (2nd generation), iPhone 12 Pro, and iPhone 12 Pro Max adds a ruler overlay to line measurements, showing you the object's dimension in granular increments. Move your iPad Pro close to a line measurement to see the ruler view appear, then tap the shutter button to take a photo so you can use the increments for planning projects.
See your measurement history
Tap the list button to view all the measurements that you've taken during the current session, including screenshots that you took. This helps you keep track of dimensions as you measure a space or series of objects. You can copy the dimensions into Notes, Mail, or any app you want to save your list in, or clear them to start over.
Learn more
You can also use your iPhone or iPod touch as a level.