Cardiospasm

CARDIOSPASM PORTER P. VINSON, M.D. Professorof Bronchoscopy,Esophagoscopynnd Gastroscopy, hlrdical C,olIegc of Virginia RICHMOND,

VIRGINIA

Definition.

Cardiospasm, second only to carcinoma as a cause of dysphagia, is a disturbance in the nerve-muscle mechanism of the esophagus whereby the esophagogastric junction remains in a state of partial or complete contracture and produces epigastric pain, dysphagia and regurgitation of food. In association with the area of contraction at the cardia there usually is more or less diIatation of the esophagus above the point of obstruction. Various terms have been employed to describe the condition, none of which has been universally accepted because of uncertainty of the cause and exact nature of the disease. Among those that have been suggested are diffuse dilatation of the esophagus without anatomic stenosis, hiatal esophagismus, phrenospasm, achalasia of the cardia, esophagospasm, ectasis of the esophagus, idiopathic dilatation of the esophagus and congenital dilatation of the esophagus. Frequency. Cardiospasm is responsible for symptoms in approximately one-third of all patients who suffer from diffrcuIty in swallowing. Several thousand cases have been reported in medical literature, and some authors have reported several hundred cases. Age, Sex, and Racial Distribution. Cardiospasm may be observed at any age, but is most frequentIy seen in the third decade of life. In the white race males are more often affected than females; although I have observed many negro women with the disease, I have seen the condition in only one negro man. Etiologv. The etiology of cardiospasm is debatabIe, although chnical symptoms and postmortem findings suggest that dein the vagal nerve generative changes ganglia permit overactivity of the sym-

pathetic nerve elements, thus producing continuous spastic contraction of tht terminal portion of the esophagus. Lack of a well defined sphincter muscle at the cardia and absence of muscular hypertrophy, except in the wall of the esophagus above the area of stenosis, are factors that have seemed to invalidate cardiospasm as a descriptive term for the disease. PatboIogL’. The gross pathologic changes observed in the esophagus of patients who have suffered from cardiospasm depend upon duration of symptoms and the degree of dysphagia. In cases of average severity the cardia is tightly contracted and the wall of the esophagus above the area of stenosis is moderately dilated. Portions of the wall may be three or four times thicker than normal, whereas in other areas the wall is much thinner than normal. If there has been little or no retention of secretion and food in the esophagus, the mucous membrane may appear normal; but whenever the esophagus is widely dilated and angulated and secretions have been retained for any length of time, the mucous membrane becomes hy-pertrophied and mcerated, and large white macerated resemble malignant degenareas ma) eration. Malignant change has occurred in the esophagus in a few cases of cardiospasm, but I have not observed carcinoma at the cardia in any patient who previously had cardiospasm. It is my belief that when carcinoma is found at the cardia in patients with cardiospasm, the original lesion was carcinoma and was confused with cardiospasm. Microscopic studies of the esophawho have died from gus of patients cardiospasm, in whom degenerative changes have been demonstrated in the v,agal ner1.e fibers, have not been accepted as authentic 79

80

American

Journal

of Surgery

Vinson-Cardiospasm

because simiIar postmortem degenerative changes have been observed in patients who have not had cardiospasm. Symptomatology.-The three cardina1 symptoms of cardiospasm are pain, dysphagia and regurgitation of food. Pain occurs in from 60 to 70 per cent of the cases and varies in intensity from miId epigastric discomfort to attacks of such severity that hypodermic injections of morphine may be required for relief. In severity and distribution the location, attacks may resembIe gallstone coIic or coronary heart disease. Pain usuaIIy begins in the epigastrium and may radiate substernahy to the neck, ears and Iower jaw, sometimes extending down one or both arms to the eIbows. Often epigastric pain is the initiaI symptom of cardiospasm and may antedate other manifestations of the disease for months or years. The pain of cardiospasm is usuaIIy more frequent and of shorter duration than that of gaIIstone coIic. Absence of jaundice and IocaI soreness over the gaIIbIadder are other features that may be heIpfu1 in distinguishing the pain of cardiospasm from that of gaIIbIadder disease. Even after dysphagia develops, pain usuaIIy is not associated with the act of swaIIowing but occurs at any time, often at night, waking the patient from a sound sIeep. Dysphagia is present in practicaIIy a11 patients who suffer from cardiospasm, aIthough sometimes the patient may be unaware that obstruction occurs in the esophagus and may beIieve that food enters the stomach before being regurgitated. AIthough varying in intensity, dysphagia is usuahy continuous from the onset. The initia1 d&cuIty is frequently experienced on drinking cold water, and throughout the disease solid food can be swaIIowed more readily than Iiquid. AppIes, popcorn and a11 cold Iiquids, particuIarIy carbonated beverages, intensify dysphagia. The troubIe is usuaIIy more pronounced when the patient is eating in a pubIic pIace or when guests are present in his home. The fear of

regurgitation under such circumstances undoubtedIy aggravates dysphagia. At onset of dysphagia there may be Ioss of weight and strength for a time, but then the patient reaches a IeveI at which the weight is maintained on a restricted diet. A portion of the Iost weight may actuaIIy be regained if the patient Iearns to force food through the cardia. This may be accompIished by first taking soIid food into the esophagus, drinking a gIass or two of water, inspiring deepIy with the chin on the chest, and increasing intrathoracic pressure by contracting the thoracic and abdomina1 muscIes without permitting air to be expeIIed from the respiratory tract. In this manner food can frequentIy be forced into the stomach in considerabIe amounts. This procedure is not without risk, however, as in one of my patients spontaneous pneumothorax deveIoped foIIowing this method of forced deglutition. Complete symptomatic obstruction of the esophagus is often noted in cardiospasm, and one of my patients had to take a11 food through a gastrostomy tube for During this time saliva eighteen years. that accumuIated in the esophagus had to be regurgitated at frequent intervaIs. At onset of dysphagia food may be regurgitated immediateIy after it is swaIlowed or as soon as it becomes obstructed at the cardia. As the disease progresses and the esophagus becomes diIated, food and secretions are retained in the distended sac for a Ionger time. Sometimes food is regurgitated that has been ingested severa days previousIy. Retention of food in the esophagus may Iead to regurgitation and strangulation at night. The patient may not be awakened by the cough associated with stranguIation; others in the house may be disturbed, however, and the patient may find that his piIIow has been discoIored by material he has regurgitated. Regurgitation of bIood in small or even Iarge amounts is noted occasionahy and unquestionabIy resuIts from uIceration associated with retention of food in the esophagus.

New

SERIES

VOL. LVI.

No.

I

Vinson-Cardiospasm

Pulmonary symptoms are often associated with cardiospasm and may vary from dyspnea after meaIs, caused by pressure on surrounding structures from a dilated esophagus HIed with food, to puImonary abscess resulting from regurgitation of materia1 from the esophagus and aspiration. Ch ronic pulmonary suppuration often folIows repeated aspiration of food that is regurgitated during sIeep. In a case reported by Shelburneg a dilated esophagus filled with food was interpreted as an abscess in the mediastinum on roentgenoscopic examination because in association with regurgitation and aspiration of food, pulmonary infection had developed with fever, cough, Ieukocytosis and other evidences of suppurative disease. When exploratory puncture of the mediastinal mass revealed material identified as coming from the esophagus, further studies were made and the true nature of the tumor was recognized. Syncopal attacks have been observed in patients with cardiospasm, and in a few instances sudden death has occurred, evidently from vagal origin. In the patients whom I have observed, the symptoms of cardiospasm have usuaIIy been present approximateIy seven years. Clinical Findings. In the usual case of cardiospasm general physical examination is essentially negative except for Ioss of weight that-is proportiona to the degree and duration of dysphagia. Alteration in the sounds heard over the esophagus with during deglutition were a stethoscope formerlv mentioned as significant in the diagnosis of cardiospasm, but probabIy have little or no vaIue. In severe cases emaciation and dehydration may be pronounced, and puImonary infection may be apparent. Studies of the blood may reveaI Ieukocytosis if infection in the Iung is acute, or dehydration may resuIt in concentration of a11 the elements of the blood. Severe hemorrhage from the esophagus is seldom seen in cardiospasm, but when it occurs, secondary anemia mav be present.

Roentgenoscopic

Examination.

If a patient suffering from difficuIty in swaIIowing is in fairIy good physical condition and can swallow soft food with a reasonabIe degree of comfort, roentgenoscopic examination of the esophagus should be made, using a suspension of barium suIfate in water as contrast medium. This may be flavored as desired. If, however, dysphagia is severe and the patient dehydrated and emaciated, roentgenoscopic studies should be deferred unti1 provision has been made for removal of the barium from the esophagus or the patient has swallowed a thread to permit stretching of the area of obstruction. Unless such precautions are observed, barium may complete occIusion of impending stenosis, and gastrostomy for feeding may become necessary. Roentgenoscopic examination in cardiospasm reveals a smooth cigar-tip type of obstruction at the cardia with more or less dilatation of the esophagus above the point of stenosis. The esophagus may be diffusely dilated and fusiform, S-shaped or Aaskshaped. If food is present in the esophagus, areas of irreguIarity may be noted and may arouse suspicion of malignancy. Roentgenoscopic study is of value in differentiating other lesions in the esophagus from cardiospasm, especially diverticuIum just above the cardia, hiatal diaphragmatic hernia and diffuse spasm of the esophagus. Special Examination. By chemical and physical methods material that has been regurgitated or aspirated from the esophagus in cardiospasm can usually be distinguished from food or secretion that has been vomited from the stomach. Esophagoscopy may be useful in the diagnosis and treatment of cardiospasm, but it is not indicated nor desirable in a11 cases. The necessity for evacuation of all food and secretion from the esophagus during esophagoscopy makes endoscopic study in cardiospasm particularly disagreeable to the patient, and when areas of ulceration are reveaIed, differentiation from carcinoma may be impossible. Esoph-

82

American Journal of Surgery

Vinson-Cardiospasm

agoscopy may be heIpfu1 in patients with compIete symptomatic obstruction of the esophagus from cardiospasm in faciIitating passage of a feeding tube into the stomach, thus obviating the necessity of gastrostomy. When the esophagus is widely diIated or anguIated, the cardia may be diffIcuIt to identify. A more heIpfu1 method than esophagoscopy in ascertaining that obstruction at the cardia has resuIted from spasm is the passage of a No. 60 French sound into the stomach, guided by a previousIy swaIIowed silk thread. If there is nothing more than sIight eIastic resistance at the cardia to passage of the sound, the diagnosis of cardiospasm is practicaIIy assured. Differential Diagnosis. Cardiospasm must be distinguished not onIy from a11 Iesions in the esophagus that cause dysphagia, but aIso from Iesions that produce acute abdomina1 and thoracic pain, especiaIIy gaIIstones and coronary heart disease. Secondary manifestations of the disease must aIso be distinguished from suppurative puImonary disease and from various Iesions that produce attacks of syncope. Of the Iesions in the esophagus that may be particuIarIy diffIcuIt to differentiate from cardiospasm, carcinoma is the most frequent and most important. Carcinoma of the cardiac end of the stomach, particuIarIy the scirrhus or “Ieather bottIe” type, may produce smooth obstruction on roentgenoscopic study, and symptoms of dysphagia may have been noted for a year or Ionger. On passing sounds through the cardia, however, dense obstruction is ‘encountered, which serves to distinguish the Iesion from cardiospasm. CicatricaI stricture seIdom occurs at the cardia, and organic stenosis at this area aImost aIways resuIts from carcinoma. Epiphrenic diverticuIa of the esophagus may cause symptoms that resemble those but carefu1 roentgenoof cardiospasm, scopic study is usuaIIy suflicient for identification.

Herniation of a portion of the stomach through the esophageal hiatus in the diaphragm, either so-called congenital shortening of the esophagus with hernia, or para-esophagea1 hernia, may produce symptoms that suggest cardiospasm; but in hernia gaseous distention is more often observed, and dysphagia is usuaIIy of an intermittent type. Roentgenoscopic and esophagoscopic examination is required to determine the type of hernia and to differentiate it from cardiospasm. “ Peptic uIcer ” of the esophagus is usuaIIy uIceration at the junction of the esophagus and stomach in congenital shortening of the esophagus with hernia and is not a primary Iesion. As the area of uIceration heaIs, contraction frequentIy occurs and stricture deveIops. Since the point of stenosis is Iocated just above the diaphragm, hernia with stricture must be differentiated from cardiospasm, which can be done by roentgenoscopic study, passage of sounds through the esophagus and esophagoscopy. TREATMENT

Medical. Many drugs that act antispasmodicaIIy have been utiIized in the management of cardiospasm, but for the most part the resuIts of medical treatment have been disappointing. At times pain is suf%cientIy intense to require hypodermic injection of morphine, but as pain is of a recurring nature, administration of narcotics shouId be avoided because of the danger of drug addiction. BelIadonna or atropin have been used extensiveIy in an effort to relieve both pain and dysphagia. One of my patients obtained temporary relief from dysphagia by the use of hypodermic injections of atropin suIfate. Increasing amounts of the drug became necessary to produce the desired resuIts unti1 at the time of my observation, g gr. was used hypodermicaIIy at each injection. After injection of the drug, dysphagia was reIieved for an hour or more, during which time food and fluid were ingested in large

NEW

SERIES VOI.. LVI.

No.

,

Vinson-Cardiospasm

amounts. Soon afterward esophageal obstruction became complete again, and all food, fluid and swahowed saliva were regurgitated until a similar dose of atropin sulfate was administered hypodermically. In the majority of patients, relief, even of a temporary nature, is not obtained by antispasmodic drugs. I have given injections of atropin sulfate in doses of 455 gr. every hour until the patient showed evidence of acute poisoning without producing relaxation of the cardia. Occasionally, the use of tincture of belladonna in doses of 15 to 20 drops every three or four hours has seemed to relieve pain which might persist at the cardia after dilatation of the area of spasm. Nitrites have been recommended in treatment, but I have not seen benelicial results in the few patients for whom I have used this form of medication. Local treatment of ulceration in the esophagus through an esophagoscope is of no value because ulceration results from stagnation of food, and until relief from obstruction can be obtained, ulceration will Frequent passage of a stomach persist. tube into the esophagus for feeding or lavage is not advisable. One patient, whom I observed, produced severe hemorrhage from trauma in the lower portion of the esophagus by this practice. When dehydration and emaciation are present, introduction of fluids, usually a solution of normal saline containing I0 per cent glucose, should be given intravenously in adequate quantity. This treatment may be supplemented by subcutaneous injection of fluid and also by proctoclysis. Transfusion of whole blood or blood serum may be advisable in certain patients. Surgical. hlany surgical procedures have been employed in the management of cardiospasm. One of the earliest forms of surgical treatment was the relatively simple procedure of opening the stomach and dilating the cardia manuahy. In two of my patients this method was used because tortuositv of the esophagus prevented introduction of a dilator from above.

When this operation becomes necessary, location of the cardia is facihtated by having the patient swallow a thread prior to exploration, the thread serving as a guide to the cardia for the fingers which are introduced into the stomach. Plastic operations on the cardia, such as are employed in congenital hypertrophic pyIoric stenosis, have also been utilized in cardiospasm but with indifferent results. In marked dilatation and anguIation of the esophagus esophagogastrostomy has been performed, but the risk of the operation is high and functional results hav-e not proved satisfactor?;. Accumulating evidence that cardiospasm is the result of overaction of the sympathetic nerve supply of the cardia has led to operations designed to interrupt the sympathetic nerve fibers enervating this portion of the esophagus. A few fairly satisfactory results have been obtained by remov,ing sympathetic ganglia in the splanchnic area, whereas other surgeons who believe that the major portion of the sympathetic nerve suppIy of the cardia originates in the cervical area, have resected the cervical sympathetic ganglia. ProbabIy compIete or almost complete removal of the sympathetic nerve fibers that control the contracting function of the cardia would relieve symptoms of cardiospasm, but it is likely that enervation is derived from many areas and that complete sympathectomy is impossible. Gastrostomy as a palliative operation is seldom necessary and whenever it has been performed, usuaIly indicates ignorance of manifestations of cardiospasm or neglect in treatment. Dilatation. Mechanical stretching of the cardia has proved the most effective method for treatment of patients with As indicated under “Treatcardiospasm. dilatation of the carment ” ~ “ Surgical,” dia has been accomplished in a few patients by opening the stomach through an nbdominal incision and stretching the area of spasm by introducing several fingers from the stomach into the esophagus. A simpler

84

American Journal of Surgery

Vinson-Cardiospasm

and more satisfactory method of diIating the cardia is by introduction of sounds or a diIator that can be distended in the esophagus, through the mouth, guided into the stomach by a previousIy swaIIowed siIk thread. The thread should be twisted and not braided siIk, and size D is usuaIIy smaI1 enough to be swaIIowed easiIy and yet strong enough to provide sufficient guidance for the diIator. When the thread is swaIIowed at the rate of about a foot an hour, it wiI1 pass through the esophagus into the stomach and coiIs of smaI1 intestine so that after fifteen or twenty feet have been swaIIowed over a period of twentyfour hours, it can be drawn taut without being puIIed out of the stomach. When the thread is thus fixed, it wiI1 permit guidance of sounds through the area of obstruction. After the thread has been utiIized as a guide and dilatation has been accompIished, the thread outside the mouth is cut off and the portion which has been swaIIowed wiI1 pass through the gastrointestina1 tract and be expeIIed in the feces. If symptomatic esophagea1 obstruction is pronounced, the patient may have some diffrcuIty swaIIowing a thread, and perseverance wiI1 be required before a sufficient amount is ingested to permit its use as a guide for passage of diIators. When a patient has faiIed to swaIIow a thread after attempting to do so for severa days, many ideas may be suggested to faciIitate its passage into the stomach, one of which is to tie a shot to the end of the thread. It has been my experience, however, that any method other than the simpIe procedure of taking the thread on the tongue and ingesting it sIowIy and continuousIy is neither desirabIe nor effective. If a patient has compIete obstruction of the cardia and diffrcuIty is encountered in swaIIowing a thread, esophagoscopy may be necessary in order to introduce a tube into the stomach for feeding. It is advisabIe, however, to continue to insist for an indefinite period of time that the patient attempt to

swaIIow a thread before esophagea1 instrumentation is empIoyed. In case it is found to be impossibIe to enter the stomach with an esophagoscope, soreness of the throat occasioned by esophagoscopy wiI1 further interfere with degIutition and may necessitate gastrostomy for feeding. After a thread has been swaIlowed, the cardia shouId be diIated with sounds. A bIunt oIive, No. 41 French, is first introduced into the stomach over the guiding thread, and if obstruction is not encountered, it is foIIowed by passage of a No. 60 French sound. ApproximateIy IO per cent of the number of patients so treated wiI1 be reIieved temporariIy from a11 symptoms. In haIf of the patients who obtain reIief, symptoms do not recur. In those who have recurrence of symptoms and in the Iarger group who do not obtain temporary compIete reIief from dysphagia by passage of sounds, the cardia shouId be distended with some type of expanding dilator. For this purpose I prefer the RusseII hydrostatic dilator that was made popular by PIummer. The diIator is introduced over the guiding thread into the cardia and is expanded with water, usuaIIy to twenty-six or twenty-eight feet of water pressure. This aImost always causes pain and a smaI1 amount of bIeeding, but foIIowing dilatation a11 types of food can be swaIIowed normaIIy, and in 75 per cent of cases reIief from symptoms is permanent. In the remaining cases there may be miId recurrence of symptoms during the six months foIIowing diIatation, but in the majority of patients compIete relief wiI1 be obtamed by repeating the treatment. Recurrence aImost never happens in a patient who obtains reIief for six months foIIowing treatment. Epigastric pain folIowing passage of sounds or stretching with the hydrostatic diIator may be suffrcientIy severe to require hypodermic injection of morphine suIfate, gr. $6 to $i. The pain may occur immediateIy after the cardia has been

N F\\

SEHIES

Vol.. LVI. No. I

Vinson-Cardiospasm

dilated or twenty-four to thirty-six hours later. When pain is miId, it may be relieved by sipping hot water, but when it is persistent, 13 drops of tincture of belladonna three or four times a day may afford relief. Inflation of an expanding dilator with air is not so satisfactory as using water pressure because air is more difficult to control, and adequate pressure with air is not easily obtained. I have not used Hurst’s mercury bougies, but I do not beIieve they can be introduced through the cardia so comfortably, accurateIy, or safely as sounds guided by a previousIy swahowed silk thread. Prognosis. If dilatation of the cardia with a hydrostatic dilator is reserved for patients who have not obtained rehef from passage of a No. 60 French sound into the stomach, the danger attending dilatation of the cardia in cardiospasm is negIigibIe. In over a thousand consecutive dilatations of the cardia with sounds and a hydrostatic dilator during the past fifteen years I have not had one serious complication. Relief from symptoms occurs immediately following treatment, and significant recurrence of discomfort is rarely observed. Patients who require treatment more radical than dilatation are seldom seen. Probably the majority of patients who hr,tve been subjected to radical treatment could have been relieved by much simpler procedures. F,ai I ure to relieve cardiospasm b?, hy-drostatic dilatation usually results from Iack of persistence on the part of the patient in swallowing a thread so that the dilator is not accurateIy introduced into the cardia or from inability to maintain proper position of the dilator in the cardia during inflation. DIFFUSE

SPAS.M

OF THE

ESOPHAGUS

SPASM

AT

CARDIA

THE

AND

The symptoms of diffuse spasm of the esophagus may be indistinguishabIe from cardiospasm, but roentgenoscopic study will usuahy be sufficient for differentiation. In cases of diffuse spasm the Iower haIf

of the esophagus presents evidence of excessive spastic contraction on roentgenoscopic examination, and on esophagoscopic examination the lumen of the esophagus may appear almost obliterated. DiIating sounds may be passed through the esophagus, but usuahy enough resistance is encountered to require a moderate degree of pressure before the sounds can be introduced into the stomach. Relief from dysphagia is less often obtained by diIatation in diffuse spasm than in cardiospasm. One of my patients, who suffered from diffuse spasm of the lower haIf of the esophagus, required gastrostomy for feeding for eight years and then was spontaneouslv relieved from difhcultv. During the activity of the spasm he was treated by medicines, esophagoscopy, hydrostatic dilatation of the cardia, passage of sounds, and bilateral cervicothoracic sympathetic ganglionectomy, al1 without beneficial effect. Two years after treatment was discontinued, symptoms disappeared as suddenly as they had appeared. In the majority of cases of cardiospasm the disease is not associated with intrathoracic or intra-abdominal lesions and is not dependent upon emotional factors Diffuse for its origin or perpetuation. with spasm, however, may be associated intra-abdominal lesions, and intermittent spasm at the cardia is frequently seen in patients who are nervously unstable. Intermittent spasm at the cardia is seldom associated with significant symptoms other than epigastric pain and recurring obstruction of food at the cardia. Roent,genoscopic examination usually does not reveal evidence of obstruction at the cardia, but occasionally the passage of a sound wiII afford relief from symptoms. REFERENCES I. BROWNE, D. C. and MCHARDY, GORDON. Medical management of cardiospasm, New Orleans At. f’P s. J., 93: 627-634, 1941. 2. FREEMAN, E. B. Symptoms, diagnosis and treatRev. Cnstroment of chronk cardiospasm. enterol., 7: 385-390, 1930.

86 3. -.

American Journal of Surgery

Conservative

treatment

Vinson-Cardiospasm of achaIasia.

Arch.

SW&, 41: 1141-I 145, 1940. 4. GRAY, H. K. and SKINNER, I. C. Operative

treatment of cardiospasm, J. Tboracic Surg., IO: 220-243, rg4o; abstract, J. A. M. A., 116: 895,

1941. 5. OCHSNER, E. W. A. and DEBAKEY, M. E. SurgicaI considerations of achalasia: review of literature and report of three cases. Arch. Surg., 41: I 146I 183, 1940. 6.p. Surgical treatment of achaIasia of esbphagus. Surg., Gynec. ti Obst., 72: 290-297, 1941.

7. RITVO, MAX and MCDONALD, E. J. Value of nitrites in cardiospasm (achalasia of esophagus) : preIiminary report, Am. J. Roentgend., 43: 500508, rg4o; abstract, J. A. M. A., I 14: 2501, 1940. 8. SCHMIDT, H. W. Diffuse spasm of Iower haIf of esophagus. Am. J. Digest. Dis. CYNutrition, 6: 693-700, 1939. g. SHELBURNE, S. A. An unusua1 case of cardiospasm. J. A. M. A., 102: 285-286, 1934. IO. VINSON, P. P. The Diagnosis and Treatment of Diseases of the Esophagus. Chap. 6, pp. 85-114. SpringtieId, III., & BaItimore, Md., 1940. CharIes C. Thomas.

CYANOSIS may be defined as a bIuish discoIoration of the skin and visibIe mucous membranes. It may vary in tint from a deep purpIish hue to a greyish sIate coIor. It is due to the presence of an abnorma1 amount of reduced hemogIobin in the capiIIary bIood.