The Effect of Heart Disease on Pulmonary Function

Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

Postgraduate Medical Journal (April 1976) 52, 209-214.

The effect of heart disease on pulmonary function

C. W. HERTZ M.D. Krankenhaus Mlhlenberg, Malente

Summary arterial blood pressure. Whereas the majority of In pulmonary congestion dyspnoea is due not only to arterial hypertensions are so-called essential hyper- an increase in elastic but also in viscous work. tensions, pulmonary hypertension is almost ex- Increased airway resistance can be reduced in most clusively secondary to a heart or lung disorder. Only of these cases by inhalation of adrenergic or anti- the consequences of blood drainage impairments cholinergic agents. Therefore, besides bronchial muco- secondary to heart disease will be considered in this sal swelling induced by congestion in the bronchial paper. vessels via bronchopulmonary anastomoses, broncho- Because of its low-pressure system the pulmonary spasm can take place and lead to cardiac asthma. The circulation is more dependent upon external influ- possible genesis of this bronchoconstriction is dis- ences than the systemic circulation. Two factors are cussed. important for the distribution of blood in the lung. As early as 1934, Bjdrkman showed by means of THE close relationship between cardiac and respi- bronchospirometry that when a person lies on his ratory function is apparent since cardiac and pul- side there is a considerable increase in pulmonary monary disorders can lead to the same symptom, blood flow in the lower side (Bjbrkman, 1934). In copyright. namely dyspnoea. Heart diseases with impaired blood 1953, Martin, Cline and Marshall found by means of drainage from the lung show effects similar to gas analyses from various bronchi a decrease in the the bronchopneumopathies but the extent to which ventilation-perfusion ratio from top to bottom when pulmonary congestion affects respiratory mechanics the body was in an upright position and hence a has not been determined. relatively increased blood flow in the base of the The cardiovascular system and the lung are one lung (Martin, Cline and Marshall, 1953). This was functional unit. The heart is an later West auxiliary organ for confirmed by and Dollery (1960) using a http://pmj.bmj.com/ respiration in that it is the machine which renders radioactive tracer. When pulmonary blood flow is the respiratory function of the lung effective in the increased, i.e. during physical exercise, but also in peripheral areas of the body. The pulmonary circu- pulmonary congestion due to increased pulmonary lation is perfused by the same blood flow volume venous pressure there is increased perfusion of the as the systemic circulation; however, it differs in lung apex. Dollery and West (1960) showed that in essential aspects from the latter. pulmonary congestion the situation can occur in The mean pressure in the pulmonary artery is which the upper parts of the lung are better perfused normally approximately one-sixth of the mean than the lower parts, possibly as a result of inter- on September 27, 2021 by guest. Protected arterial pressure in the systemic circulation, and the stitial oedema in the lower sections of the lung. resistance in the pulmonary circulation is approxi- In addition to hydrostatic pressure, the relation- mately one-tenth of that in the systemic circulation. ship between intrapulmonary vascular pressure and There are no valves in the pulmonary veins; this alveolar pressure also plays a part in pulmonary fact is of particular importance in connection with blood distribution. If, for example, the alveolar pulmonary hypertension in left venticular failure or pressure exceeds the pulmonary venous pressure, the mitral stenosis. If the blood from the lung is pre- pulmonary blood flow is determined more by the vented from draining, the pulmonary arterial pres- pulmonary arterial/alveolar pressure difference than sure is increased as a consequence of the increased by the arteriovenous pressure difference. Thus, pulmonary venous pressure. By contrast, in the whereas obstructive bronchopneumopathies are systemic circulation a venous drainage block of the often associated with increased alveolar pressure, right atrium does not have any noteworthy effect on heart diseases involving pulmonary congestion result Correspondence: Professor C. W. Hertz, Department of n the reverse case, i.e. increased pulmonary venous Internal Medicine, Krankenhaus Milhlenberg, D 2427 pressure and a more homogeneous distribution of Malente, Federal Republic of Germany. blood within the lung. Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

210 C. W. Hertz

140 -7 30- 1 20 -6 I 0 E 100 5 E 90 c 0 ,80 K 42 70-

c060~~~~~~~~~~~~~~~ 40

30- 20- I 0

N I II tE N I UIEa N I urnB C Wvisc Wo copyright. FIG. 1. Mean values + 2 s.e. mean of the compliance (C), total inspiratory work (Wtot), and viscous work (Wvisc) in healthy subjects (N), and with three grades of mitral stenosis (N.Y. Heart Association Classi- fication). Number of patients in each group: N, 12; I, 30; II, 43; III, 27. All values expressed as percentage of healthy controls. Work expressed as gcm/ml.

However, it is known that the distribution of >50 mm in alveolar oxygen pressure in unilateral pulmonary blood flow is not only dependent upon hypoxia. The effect of unilateral CO2 increase on http://pmj.bmj.com/ these mechanical factors but also on local oxygen blood flow distribution due to re-breathing has been pressures. Owing to a marked regional lowering of studied using bronchospirometry with oxygen the alveolar oxygen pressure there is a local increase respiration (Hertz, 1956b). In thirty-two studies in in vascular resistance and, hence, diversion of blood twenty patients the mean blood flow in the CO2 re- into better perfused parts. This mechanism may also breathing side decreased to 93-6% of the baseline play a role in pulmonary congestion because of a value. No greater effects can be anticipated under local shift of the ventilation: perfusion ratio which physiological conditions because no marked local on September 27, 2021 by guest. Protected may give rise to vasoconstriction. The effect of local Pco2 increases can be expected in distribution dis- hypoxia on blood flow distribution was shown 20 orders. General hypercapnia is a different matter; years ago by means of bronchospirometry with but this is not expected in functional disorders of unilateral re-breathing to result in a decrease in cardiac aetiology. blood flow of approximately 30°o (Hertz, 1955, Although mechanical forces and gas pressures 1956a). have an effect on pultnonary blood flow, the reverse There are few studies on the effect of local Pco2 can occur, in which case changes in blood flow have increase in man. The effects of a local Pco 2 increase, an effect on lung function. however, will always be less than those of local In left heart failure, resulting either from an hypoxia since the local CO2 pressure cannot exceed increase in pressure in the left atrium or an increase that of the mixed venous blood, and this is only in end-diastolic pressure in the left ventricle, there is slightly greater than that of the arterial blood. vascular congestion of the lung which has an effect Unilateral re-breathing will result in a difference on respiratory mechanics. The elastic properties of in alveolar CO 2 pressure between the two sides of the the lung are dependent upon all components of the lung of 5-15 mm Hg compared with a difference of lung tissue, including the blood in the pulmonary Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

Heart disease andpulmonary function 211

16 1-5 14 130 - .13 1 2O : - ~~~~~~~~~~~~~~~~~~~~~~1 12 120 -12

100 to\ ..90 7 j S \ \ q8 Ew

C b C b a b 0 C ~~~WviscW~~~~~ot copyright.

FIG. 2. Individual values together with mean ± s.e. mean for compliance (C), total inspiratory work (Wtot), and viscous work of breathing (Wvisc) before (a) and after (b) inhalation oforciprenaline in twenty-seven cases of mitral stenosis with bronchial obstruction (after Hamm and Scholmerich. 1964). vessels, so that blood congestion must result in a stenosis stage I (New York Association classification) reduction in static compliance. As early as 1888, von forty-three patients in stage II and forty-seven http://pmj.bmj.com/ Basch described experiments which showed a re- patients in stage III. A reduced compliance was found duced compliance of the lungs in vascular congestion which was related to the severity of the disease. The (von Basch, 1888). main cause for the increased elastance is, above all, Several authors have reported a restrictive venti- the blood volume in the lung, but other factors such latory disorder in left heart failure and reduced vital as interstitial oedema, fibrosis, possibly small areas capacity. Thus, in the twenties, daily measurement of of atelectasis, swelling of the bronchial mucosa, and

vital capacity in left heart failure was used as an changes in alveolar surface tension, may also play a on September 27, 2021 by guest. Protected indicator of therapeutic success. part. The conditions in pulmonary congestion suggest As a result of the reduction in compliance, the that increase in respiratory work is required to work of breathing was increased, depending upon overcome elastic resistance. Mitral stenosis is well the degree of severity of the clinical symptoms of suited for the study of this problem since the haemo- mitral stenosis. In approximately 40%. ofthe patients dynamic disturbance is relatively constant. Studies with mitral stenosis the viscous work had also of the mechanics of respiration have shown that increased above normal values, again dependent respiratory work increases not only to overcome upon the degree of severity of the disorder (Fig. 1, elastic resistance but also to overcome viscous column 3). resistances. Figure 1 shows the results of studies in The increased viscous work is probably primarily 100 operated, and therefore confirmed, cases of the result of bronchial obstruction. Thus the total mitral stenosis by Hamm and Scholmerich (1964). and viscous respiratory work decreases and the On the left are the mean values for compliance as a dynamic compliance increases after the inhalation of percentage of the expected value as found in twelve orciprenaline (Fig. 2). In most cases, the viscous healthy volunteers, thirty patients with mitral respiratory work does not return to normal. The Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

212 C. W. Hertz 16 did not apply only to the obstructive cases, but was 15 also found, to a lesser extent, in those patients whose viscous repiratory work lay within the normal range. 140 14 The increase in residual volume in mitral stenosis is 13 therefore not necessarily a characteristic of bronchial 130 obstruction. It is likely that vascular congestion and 120 12 interstitial oedema and pulmonary fibrosis play a greater role. The effect of vascular congestion on the 10 I E E elasticity of the lung appears to be a function of the 100 10 v} air content. In animal experiments Borst et al. (1957)

uc found that, as a result of a sudden fall in pressure in 90 I 9 a) I the left atrium, more of the residual air escaped

8 .C_ from the already collapsed lungs. 2.) 80 -6 In contrast with the findings in patients with F c 70 7 -X increased viscous respiratory work, the changes in . -- -r- 0 the FEV1 were less The purely restric- 60 I... 6 convincing. r I... Y-k tive cases of mitral stenosis were within the normal Ii 5 50 ix s: range. In mitral stenosis with additional obstruction it the FEV1 was scattered irregularly down to of 40 r rl 4 30/Y s. XXI the vital capacity. This may have been due to the 30 3 fact that the FEV1 is measured at the point of maximum inspiration when the bronchial diameter 20 * . 2 is at its greatest and the flow resistance therefore

10 relatively low. In contrast, the viscous respiratory work is measured in the normal end-expiratory 0 0 c wtot Wvisc position. On the other hand, our own studies, with values for viscous respiratory work of approximatelycopyright. FIG. 3. Individual values together with mean + s.e. 4 gcm/ml, there was no demonstrable relationship mean for compliance (C), total inspiratory work (Wtot), and viscous work of breathing (Wvisc) in fifty-seven with relative FEV1 (Ghosh and Hertz, 1971). As has cases of mitral stenosis with pulmonary restriction and already been shown, the mean values for viscous forty-three cases with additional bronchial obstruction respiratory work lay between 2 5 and 3-2 gcm/ml in (after Hamm and Scholmerich, 1964). all cases ofmitral stenosis investigated by Hamm and Sch6lmerich (1964). Only in twenty patients was the increase in dynamic compliance is probably also viscous respiratory work greater than 4 gcm/ml and attributable to the reduction of obstruction since the accordingly the FEV1 in twenty-three patients was http://pmj.bmj.com/ dynamic compliance in obstruction does not corre- less than 65%. spond to the static compliance. The obstruction The finding that left heart failure can cause an which can be deduced from the results of this study airway obstruction was confirmed using body is of primary importance. As a result of the increased plethysmography. Figure 4 shows the results of vascular congestion of the lung the tissue frictional Kammler et al. (1968) in fifteen healthy control resistance may also contribute to the increase in subjects (I), twenty-seven patients with heart disease, viscous respiratory work. Hysteresis is only likely to who complained of dyspnoea on fairly vigorous on September 27, 2021 by guest. Protected be of importance in extreme pulmonary congestion exercise (II), and thirty-five patients with heart and in the oedematous lung as a result of altered disease with dyspnoea on light exercise (III). In surface tensions. many cases, especially in those with more severe Figure 3, also taken from the study by Hamm and heart disease, there was a slight to moderate increase Sch6lmerich (1964), presents data for cases divided in airway resistance. Here again, as Wettengel (1974) into restrictive and obstructive groups. Cases showed in seven patients with mitral stenosis, a termed obstructive were those which showed a clear reduction in resistance was achieved by inhalation response to orciprenaline as well as those in which of an adrenergic and anticholinergic agent. Within the ratio of viscous: elastic work was > 0 75. The 30 min of inhalation of an atropine derivative, difference in the mean values for percentage com- resistance fell by 36°/ and, after orciprenaline, by pliance were not significant, whereas the differences 28%. in the total and, above all, the viscous work of It has thus been shown that in many patients with breathing were highly significant. pulmonary congestion, there is bronchial obstruc- In most cases of mitral stenosis there was an tion. These results are in agreement with the clinical increase in residual volume. However, this increase findings, for example in congestive bronchitis. Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

Heart disease andpulmonary function 213

10- r= 0 650

4_y + 1-32 x-0-1

Dyspnoea i+t+ 2, / -+ . No dyspnoea

I fl m

FIG. 4. Airway resistance (Rt) in cardiac patients. I = healthy control copyright. subjects (n = 15), II = patients with heart disease, who complained of dyspnoea on fairly vigorous exercise (n = 27), III = cardiac patients with dyspnoea on light exercise (n = 35) (after Kammler et al., 1968).

Because the blood from the bronchial arteries drains So far, there have only been hypotheses about into the pulmonary veins via the broncho-pulmonary the possible genesis of this bronchoconstriction in capillary network, there is congestion in the pul- pulmonary congestion. Perhaps the congestion gives monary veins as well as in the bronchial circulation. rise to metabolites in the bronchial mucosa which This can lead to an oedema ofthe bronchial wall with cause bronchoconstriction. It was demonstrated in http://pmj.bmj.com/ concomitant constriction of the lumen and transu- animal experiments that irritant receptors can be dation into the bronchial lumen. The bronchial and stimulated by pulmonary congestion. An increase in pulmonary arteries, like the bronchial and pulmo- airway resistance was demonstrated when the pres- nary veins, are connected with each other by ana- sure in the left atrium was rapidly increased and this stomoses so that the two circulations are closely could be abolished by vagotomy or atropine. The connected. Morphologically, several authors have extreme retardation in flow or blood stasis in certain found an enlargement of all parts of the bronchial areas of the lung in advanced pulmonary congestion on September 27, 2021 by guest. Protected vascular system in mitral stenosis. may be of importance. Following blockade of one Apart from this constriction of the bronchial branch of the pulmonary artery, there was a reduc- lumen due to mucosal swelling, bronchospasm may tion in respiratory volume in the same side of the also play a part in the obstruction caused by left lung, which could only be explained by broncho- heart failure. Thus, sudden attacks of respiratory constriction. The blood in the dependent vessels distress and wheezing induced by acute pulmonary stagnates and there is a diminution in tidal volume congestion are referred to as cardiac asthma. Pul- and, incidentally, also in respiratory rate (Hertz monary oedema can also be heralded by clinical and et al., 1962). The addition of CO 2 to the respired air auscultatory findings which resemble those of status of the blocked side not only abolished the reduction asthmaticus. This can give rise to greater resistance in rate but also the unilateral reduction in tidal values than those described. However, in the cases of volume. One can speculate whether local hypo- mitral stenosis, the obstruction was reversible on capnia or even acapnia is to some extent responsible inhalation of a bronchospasmolytic agent, which for this and the effect of the addition of CO2 tends seems to show that there is a broncho-constrictor to support this. For, wherever blood was stagnating component. in the pulmonary capillaries with maintained venti- Postgrad Med J: first published as 10.1136/pgmj.52.606.209 on 1 April 1976. Downloaded from

214 C. W. Hertz

lation the CO2 pressure was reduced within a very BJORKMAN, S. (1934) Bronchospirometrie. Eine Methode, die short time to values approaching zero (Hertz et al., Funktion der menschlichen Lunge getrennt und gleich- zeitig zu untersuchen. Acta medica scandinavica, Suppl. 1962). 56, 1. Finally, in advanced pulmonary congestion, espe- BORST, H.G., BERGLUND, E., WHITTENBERGER, J.L., MEAD, J., cially in mitral stenosis, several investigators have McGREGOR, M. & COLLIER, C. (1957) The effects of demonstrated a reduction in diffusion capacity. pulmonary vascular pressures on the mechanical properties of the lungs of anesthetized dogs. Journal of Clinical This showed that there is a clear correlation with the Investigation, 36, 1708. degree of severity of the underlying heart disease. DOLLERY, C.T. & WEST, J.B. (1960) Regional uptake of The main causes of dyspnoea in heart disease are radioactive oxygen and carbon dioxide in the lungs of to be found primarily in the increased elastic work of patients with mitral stenosis. Circulation Research, 8, 765. GHOSH, S.K. & HERTZ, C.W. (1971) Die Beziehungen breathing as a result of the reduced compliance with zwischen Sekundenkapazitat und anderen atemmechani- overfilling of the pulmonary blood vessels and, schen GroBen. Klinische Wochenschrift. 49, 1083. secondly, in the obstruction, which plays a promi- HAMM, J. & SCHOLMERICH, P. (1964) 'Uber Lungenschwellung nent role in cardiac asthma. The reduction in und Lungenstarrheit'. Atemmechanische Untersuchungen an 100 Mitralstenosen. Klinische Wochenschrift, 42, 1108. diffusion capacity in the development of dyspnoea HERTZ, C.W. (1955) Die DurchblutungsgroBe hypoventi- plays, at most, only a subordinate role. lierter Lungenbezirke. Verhandlungen der Deutschen Congestive bronchitis with early pulmonary Gesellschaftfiir Kreislaufforschung, 21, 447. oedema, and the severe respiratory insufficiency in HERTZ, C.W. (1956a) Untersuchungen uber den EinfluB der chronic bronchitis can show the same alveolaren Gasdrucke auf die intrapulmonale Durchblu- clinical tungsverteilung. Klinische Wochenschrift, 34, 472. picture. However, with a view to therapy, it is of the HERTZ, C.W. (1956b) Einseitige C02-Erhohung und Durch- utmost importance to differentiate between them. If blutungsgroBe jeder Lungenseite. Klinische Wochen- a patient presents with advanced dyspnoea and schrift, 34, 532. rhonchi over the lung areas and pulmonary oedema HERTZ, C.W., WITZLEB, E., FREUND, H. & SCHLEPPER, M. (1962) Veranderungen der Atmung bei einseitiger Blockade is erroneously diagnosed, the administration of der A. pulmonalis. Pfluigers Archiv fiur die gesamte oxygen and morphine could have deleterious effects. Physiologie des Menschen und der Tiere, 276, 280. This is because morphine acts as a respiratory KAMMLER, E., REICHEL, G., ULMER, W.T., SCHURMEYER, E. depressant and the administration of oxygen can & WINDHAGEN, K.E. (1968) Untersuchungen zur pul-copyright. monalen und cardialen Dyspnoe. Verhandlungen der lead to CO2 narcosis, especially if advanced respi- Deutschen Gesellschaft far innere Medizin, 74, 210. ratory acidosis already exists. For purposes of MARTIN, C.J., CLINE, F. JR & MARSHALL, H. (1953) Lobar differential diagnosis, blood gas analysis and X-ray alveolar gas concentrations: effect of body position. can be of assistance. With the modern specialization Journal of Clinical Investigation, 32, 617. WEST, J.D. & DOLLERY, C.T. (1960) Distribution of blood of medicine it is important for the chest physician to flow and ventilation-perfusion ratio in the lung measured be aware of left heart failure and for the cardiologist with radioactive CO2- Journal of Applied Physiology, 15, to be aware of respiratory insufficiency. 405. WETTENGEL, R. (1974) The effects of Sch 1000 MDI in http://pmj.bmj.com/ patients with mitral stenosis. In: The place of parasympa- References tholytic drugs in the management of chronic obstructive BASCH, S. VON (1888) Ober Lungenschwellung und Lungen- airways disease. International Symposium, Killarney, 21 starrheit. Wiener medizinische Presse, 14, 587. September 1974. on September 27, 2021 by guest. Protected