110:
377:. The use of an actual column of mercury to measure pressure normally requires correction for the density of mercury at the actual temperature and the sometimes significant variation of gravity with location, and may be further corrected to take account of the density of the measured air, water or other fluid.
294:
conducted experiments with mercury that allowed him to measure the presence of air. He would dip a glass tube, closed at one end, into a bowl of mercury and raise the closed end up out of it, keeping the open end submerged. The weight of the mercury would pull it down, leaving a partial vacuum at the
416:
In medicine, pressure is still generally measured in millimetres of mercury. These measurements are in general given relative to the current atmospheric pressure: for example, a blood pressure of 120 mmHg, when the current atmospheric pressure is 760 mmHg, means 880 mmHg relative to
286:
claimed that all things are made of air that is simply changed by varying levels of pressure. He could observe water evaporating, changing to a gas, and felt that this applied even to solid matter. More condensed air made colder, heavier objects, and expanded air made lighter, hotter objects. This
336:, both of which vary with local conditions, specific standard values for these two parameters were adopted. This resulted in defining a "millimetre of mercury" as the pressure exerted at the base of a column of mercury 1 millimetre high with a precise density of
324:, the mercury column's sensitivity to temperature and local gravity, and the greater convenience of other instrumentation. They displayed the pressure difference between two fluids as a vertical difference between the mercury levels in two connected reservoirs.
1123:
Gijón-Conde, T; Sánchez-Martínez, M; Graciani, A; Cruz, JJ; López-García, E; Ortolá, R; Rodríguez-Artalejo, F; Banegas, JR (July 2019). "Impact of the
European and American guidelines on hypertension prevalence, treatment, and cardiometabolic goals".
327:
An actual mercury column reading may be converted to more fundamental units of pressure by multiplying the difference in height between two mercury levels by the density of mercury and the local gravitational acceleration. Because the
400:
The precision of modern transducers is often insufficient to show the difference between the torr and the millimetre of mercury. The difference between these two units is about one part in seven million or
109:
317:
went farther, having his brother-in-law try the experiment at different altitudes on a mountain, and finding indeed that the farther down in the ocean of atmosphere, the higher the pressure.
1013:
Council
Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC
278:
For much of human history, the pressure of gases like air was ignored, denied, or taken for granted, but as early as the 6th century BC, Greek philosopher
194:, are reflecting the fact (common basic knowledge among health care professionals) that this is the usual unit of blood pressure in clinical medicine.
295:
far end. This validated his belief that air/gas has mass, creating pressure on things around it. Previously, the more popular conclusion, even for
1193:
1051:
299:, was that air was weightless and it is vacuum that provided force, as in a siphon. The discovery helped bring Torricelli to the conclusion:
1028:
507:
1097:
1230:
17:
1206:
303:
We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight.
1045:
952:
124:
174:
unit, the millimetre of mercury is still often encountered in some fields; for example, it is still widely used in
1176:
996:
171:
1078:
500:
1016:
1012:
1098:
National Center for
Biotechnology Information of the National Library of Medicine of the United States.
1267:
1262:
532:
308:
462:
95:
1099:
1032:
493:
457:
363:
chosen for this definition is the approximate density of mercury at 0 °C (32 °F), and
542:
467:
291:
967:
445:
279:
320:
Mercury manometers were the first accurate pressure gauges. They are less used today due to
527:
451:
8:
439:
254:
127:
1149:
179:
1234:
1212:
1202:
1172:
1141:
1041:
478:
321:
218:
135:
113:
1153:
1133:
428:
374:
333:
1137:
957:
408:. By the same factor, a millitorr is slightly less than a micrometre of mercury.
329:
287:
was akin to how gases become less dense when warmer and more dense when cooler.
424:
191:
1256:
1216:
962:
517:
314:
273:
152:
1027:
1145:
187:
1122:
947:
522:
474:
381:
139:
434:
1074:
175:
131:
41:
134:, formerly defined as the extra pressure generated by a column of
296:
283:
183:
972:
537:
198:
1192:
Hoffman, Dorothy; Singh, Bawa; Thomas, John H. (1998).
311:, was essentially the first documented pressure gauge.
1233:. National Physical Laboratory (NPL). Archived from
1091:
993:
BS 350: Part 1: 1974 – Conversion factors and tables
380:
Each millimetre of mercury can be divided into 1000
420:Routine pressure measurements in medicine include:
186:. For example, the U.S. and European guidelines on
1191:
411:
1254:
344:when the acceleration due to gravity is exactly
1201:. San Diego, CA: Academic Press. p. 171.
501:
253:). Although the two units are not equal, the
197:One millimetre of mercury is approximately 1
1116:
1029:International Bureau of Weights and Measures
1008:
1006:
1100:"Articles demonstrating pressures in mm Hg"
508:
494:
1195:Handbook of vacuum science and technology
1169:Tables of Physical and Chemical Constants
1003:
264:) is negligible for most practical uses.
1171:(XV ed.). Longman. pp. 22–23.
1166:
108:
395:
142:high, and currently defined as exactly
14:
1255:
1067:
1034:The International System of Units (SI)
332:of mercury depends on temperature and
190:, in using millimeters of mercury for
178:, as demonstrated for example in the
24:
25:
1279:
1167:Kaye, G.W.C.; Laby, T.H. (1986).
953:Centimetre or millimetre of water
934:
856:
771:
704:
643:
571:
463:Pulmonary artery catheterization
1057:from the original on 2021-06-04
1223:
1185:
1160:
1021:
985:
412:Use in medicine and physiology
13:
1:
1040:(8th ed.), p. 127,
997:British Standards Institution
978:
433:Intraocular pressure, with a
1138:10.1097/HJH.0000000000002065
1079:American Medical Association
1075:"AMA Manual of Style Online"
7:
1017:European Economic Community
941:
27:Manometric unit of pressure
10:
1284:
477:units are used to measure
271:
267:
489:
96:English Engineering units
91:
77:
73:
55:
47:
37:
32:
450:Intramuscular pressure (
1126:Journal of Hypertension
458:Central venous pressure
309:Torricelli's experiment
159:pascals. It is denoted
468:Mechanical ventilation
305:
292:Evangelista Torricelli
116:
103:0.01933678 lbf/in
18:Millimeters of mercury
968:Pound per square inch
543:Pound per square inch
446:Intracranial pressure
301:
290:In the 17th century,
272:Further information:
121:millimetre of mercury
112:
33:millimetre of mercury
528:Technical atmosphere
452:compartment syndrome
396:Relation to the torr
384:of mercury, denoted
307:This test, known as
219:atmospheric pressure
999:. 1974. p. 49.
533:Standard atmosphere
486:
440:Cerebrospinal fluid
255:relative difference
68:... is equal to ...
1237:on 28 January 2015
484:
427:, measured with a
322:mercury's toxicity
180:medical literature
117:
101:
93:
85:
79:
1268:Mercury (element)
1263:Units of pressure
1208:978-0-12-352065-4
939:
938:
155:or approximately
114:Mercury barometer
107:
106:
56:Conversions
51:mmHg, mm Hg
16:(Redirected from
1275:
1247:
1246:
1244:
1242:
1231:"Pressure Units"
1227:
1221:
1220:
1200:
1189:
1183:
1182:
1164:
1158:
1157:
1132:(7): 1393–1400.
1120:
1114:
1113:
1111:
1110:
1095:
1089:
1088:
1086:
1085:
1071:
1065:
1064:
1063:
1062:
1056:
1039:
1025:
1019:
1010:
1001:
1000:
989:
932:
931:
928:
921:
920:
917:
910:
909:
906:
899:
898:
895:
888:
887:
884:
880:
868:
867:
864:
854:
853:
850:
844:
842:
841:
838:
835:
827:
826:
823:
816:
815:
812:
805:
804:
801:
789:
788:
785:
782:
769:
764:
763:
755:
754:
741:
740:
737:
734:
727:
726:
719:
718:
715:
712:
702:
701:
694:
692:
680:
679:
676:
673:
665:
659:
658:
650:
641:
630:
629:
626:
623:
620:
611:
609:
600:
598:
589:
587:
578:
510:
503:
496:
487:
483:
429:sphygmomanometer
417:perfect vacuum.
407:
406:
375:standard gravity
372:
371:
368:
362:
360:
351:
349:
343:
341:
263:
262:
252:
250:
247:
241:
239:
238:
235:
232:
231:
230:
216:
214:
213:
210:
207:
170:Although not an
158:
151:
150:
147:
102:
94:
86:
80:
30:
29:
21:
1283:
1282:
1278:
1277:
1276:
1274:
1273:
1272:
1253:
1252:
1251:
1250:
1240:
1238:
1229:
1228:
1224:
1209:
1198:
1190:
1186:
1179:
1165:
1161:
1121:
1117:
1108:
1106:
1096:
1092:
1083:
1081:
1073:
1072:
1068:
1060:
1058:
1054:
1048:
1037:
1026:
1022:
1011:
1004:
991:
990:
986:
981:
958:Inch of mercury
944:
929:
926:
924:
918:
915:
913:
907:
904:
902:
896:
893:
891:
885:
882:
878:
876:
865:
862:
860:
851:
848:
846:
839:
836:
833:
832:
830:
824:
821:
819:
813:
810:
808:
802:
799:
797:
786:
783:
780:
778:
767:
761:
759:
752:
750:
738:
735:
732:
730:
724:
722:
716:
713:
710:
708:
699:
697:
690:
688:
677:
674:
671:
669:
663:
656:
654:
648:
639:
627:
624:
621:
618:
616:
607:
605:
596:
594:
585:
583:
576:
514:
485:Pressure units
479:Starling forces
414:
404:
402:
398:
369:
366:
364:
358:
356:
347:
345:
339:
337:
334:surface gravity
330:specific weight
276:
270:
260:
258:
248:
245:
243:
236:
233:
228:
226:
225:
224:
222:
211:
208:
205:
204:
202:
156:
148:
145:
143:
100:
92:
87:133.322 Pa
84:
78:
28:
23:
22:
15:
12:
11:
5:
1281:
1271:
1270:
1265:
1249:
1248:
1222:
1207:
1184:
1177:
1159:
1115:
1090:
1066:
1046:
1020:
1002:
983:
982:
980:
977:
976:
975:
970:
965:
960:
955:
950:
943:
940:
937:
936:
933:
922:
911:
900:
889:
874:
873:1 lbf/in
870:
869:
858:
855:
828:
817:
806:
795:
791:
790:
776:
773:
770:
765:
756:
747:
743:
742:
728:
720:
706:
703:
695:
686:
682:
681:
666:
660:
651:
645:
642:
637:
633:
632:
613:
602:
591:
580:
573:
570:
566:
565:
562:
559:
556:
553:
550:
546:
545:
540:
535:
530:
525:
520:
515:
513:
512:
505:
498:
490:
473:In physiology
471:
470:
465:
460:
455:
448:
443:
437:
431:
425:Blood pressure
413:
410:
397:
394:
269:
266:
192:blood pressure
105:
104:
98:
89:
88:
82:
75:
74:
71:
70:
65:
58:
57:
53:
52:
49:
45:
44:
39:
35:
34:
26:
9:
6:
4:
3:
2:
1280:
1269:
1266:
1264:
1261:
1260:
1258:
1236:
1232:
1226:
1218:
1214:
1210:
1204:
1197:
1196:
1188:
1180:
1174:
1170:
1163:
1155:
1151:
1147:
1143:
1139:
1135:
1131:
1127:
1119:
1105:
1101:
1094:
1080:
1076:
1070:
1053:
1049:
1047:92-822-2213-6
1043:
1036:
1035:
1030:
1024:
1018:
1014:
1009:
1007:
998:
994:
988:
984:
974:
971:
969:
966:
964:
963:Inch of water
961:
959:
956:
954:
951:
949:
946:
945:
923:
912:
901:
890:
875:
872:
871:
859:
829:
818:
807:
796:
793:
792:
777:
774:
766:
757:
748:
745:
744:
729:
721:
707:
696:
687:
684:
683:
667:
661:
652:
646:
638:
635:
634:
614:
603:
592:
581:
574:
568:
567:
563:
560:
557:
554:
551:
548:
547:
544:
541:
539:
536:
534:
531:
529:
526:
524:
521:
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491:
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447:
444:
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438:
436:
432:
430:
426:
423:
422:
421:
418:
409:
393:
391:
387:
383:
378:
376:
353:
335:
331:
325:
323:
318:
316:
315:Blaise Pascal
312:
310:
304:
300:
298:
293:
288:
285:
281:
275:
274:Pressure head
265:
256:
251: pascals
242: ≈
220:
200:
195:
193:
189:
185:
181:
177:
173:
168:
166:
162:
154:
141:
137:
133:
129:
126:
122:
115:
111:
99:
97:
90:
83:
76:
72:
69:
66:
64:
60:
59:
54:
50:
46:
43:
40:
36:
31:
19:
1241:16 September
1239:. Retrieved
1235:the original
1225:
1194:
1187:
1168:
1162:
1129:
1125:
1118:
1107:. Retrieved
1103:
1093:
1082:. Retrieved
1069:
1059:, retrieved
1033:
1023:
992:
987:
794:1 Torr
472:
419:
415:
399:
389:
385:
379:
355:The density
354:
326:
319:
313:
306:
302:
289:
277:
217:of standard
196:
188:hypertension
169:
164:
160:
120:
118:
67:
62:
61:1 mmHg
38:Unit of
746:1 atm
636:1 bar
382:micrometres
257:(less than
201:, which is
182:indexed in
1257:Categories
1178:0582463548
1109:2023-09-02
1084:2018-02-24
1061:2021-12-16
979:References
948:Bar (unit)
685:1 at
569:1 Pa
475:manometric
388:or simply
361: kg/m
342: kg/m
280:Anaximenes
165:mm Hg
140:millimetre
125:manometric
1217:162128757
564:(lbf/in)
435:tonometer
350: m/s
1154:86674318
1146:31145710
1052:archived
1031:(2006),
942:See also
442:pressure
176:medicine
132:pressure
81:SI units
42:Pressure
1015:of the
843:
831:
798:133.322
723:735.559
631:lbf/in
615:1 Pa =
604:1 Pa =
593:1 Pa =
582:1 Pa =
575:1 Pa =
561:(Torr)
390:microns
297:Galileo
284:Miletus
268:History
244:133.322
240:
223:
215:
203:
157:133.322
153:pascals
144:133.322
136:mercury
1215:
1205:
1175:
1152:
1144:
1104:PubMed
1044:
925:51.714
779:14.695
768:1.0332
731:14.223
670:14.503
664:750.06
649:1.0197
606:7.5006
595:9.8692
584:1.0197
558:(atm)
552:(bar)
518:Pascal
184:PubMed
63:in ...
48:Symbol
1199:(PDF)
1150:S2CID
1055:(PDF)
1038:(PDF)
914:0.068
903:0.070
892:0.068
861:0.019
847:0.001
820:0.001
809:0.001
760:1.013
709:0.967
698:0.980
655:0.986
617:0.000
612:Torr
555:(at)
549:(Pa)
403:0.000
365:9.806
359:595.1
346:9.806
340:595.1
259:0.000
123:is a
1243:2020
1213:OCLC
1203:ISBN
1173:ISBN
1142:PMID
1042:ISBN
973:Torr
881:.757
787:5142
775:760
739:1203
725:2401
717:3541
601:atm
579:bar
538:Torr
405:015%
386:μmHg
261:015%
199:torr
161:mmHg
138:one
128:unit
1134:doi
930:572
927:932
919:964
916:045
908:958
905:306
897:573
894:947
886:168
883:293
879:894
866:775
863:336
852:789
849:315
840:760
822:359
814:224
811:333
803:421
800:368
784:775
781:948
753:325
751:101
736:307
733:343
714:105
711:841
700:665
691:066
678:022
675:773
672:773
628:730
625:737
622:037
619:145
590:at
523:Bar
373:is
370:m/s
282:of
249:421
246:368
237:760
229:325
227:101
212:760
163:or
149:415
146:387
130:of
1259::
1211:.
1148:.
1140:.
1130:37
1128:.
1102:.
1077:.
1050:,
1005:^
995:.
935:—
857:—
845:≈
825:51
772:—
762:25
758:≡
749:≡
705:—
693:.5
689:98
668:=
662:=
657:92
653:=
647:=
644:—
640:10
610:10
599:10
588:10
577:10
572:—
481:.
392:.
367:65
357:13
352:.
348:65
338:13
172:SI
167:.
119:A
1245:.
1219:.
1181:.
1156:.
1136::
1112:.
1087:.
877:6
837:/
834:1
608:×
597:×
586:×
509:e
502:t
495:v
454:)
234:/
221:(
209:/
206:1
20:)
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