198 ]uq 1955

A Method of Measuring Maximum Breathing Capacities in Individual Lungs by Bronchospirometry

By J. B. CLARK and G. P. MAHER-LOUGHNAN From the Respiratory Function Unit, Colindale Hospital, London

When measuring respiratory function in general, two main methods are employed, those dealing with gaseous exchanges (measurements of Respiration) and those which assess movement of air (measurements of Ventilation).

In this paper we are concerned exclusively with methods of measuring ventilation, although it is recognized that no picture of respiratory function can be complete without including assessments of respiratory exchange.

Of recent years the static methods of measuring ventilation, including the several components of the total lung volume have been found wanting" (Gilson and Hugh- Jones, I949) and during the past few years interest has centred more on studying air moving in and out of the lungs. A dynamic measurement, the Maximum Breathing Capacity, was described originally by Hermannsen (I933) as 'the maximum volume of air that can be breathed in unit time during voluntary hyperventilation'. In practice the greatest volume of air that can be expired in I5-2o seconds was measured, and expressed in litres pcr minute.

Objections "to the test are chiefly that it is subjective, being dependent on the patient's co-operation, an inconstant factor which in itself cannot be estimated. There is also an inherent error in all spirometers, not easily compensated, which bccomes evident at high rcspiratory rates (Bcrnstcin and Mendel, I95I).

The use of a 'timed vital capacity' hasbeen suggested as a more useful guide, especially during the expiratory phase, since it is there that timing reveals appreciable differences in the presence of disease.

Continental workers have developed these

timed expiratory assessments, and indices based on them; Gaensler (I95O and I95 I) described an electrical timing mechanism which can be used with a standard spiro- metcr. Using this or similar timing devices the 'one second capacity' was defined as that volume of air expelled in one second during a forced maximum expiration.

In this country a further development has been described by Kennedy (I953). He defined a vital spirogram (V.S.) as a tracing obtained when a person expels the whole of the vital capacity into a spirometer and then immediately inspires maximally from the spirometer, the movement of the spirometer being recorded on a fast kymograph. The expiratory phase he terms the expiratory vital spirogram (E.V.S.) which was shown (Kennedy, I95O ) to have two phases, a steep linear fraction breaking away into a less steep and finally undulatory curve, at the 'Critical Point'.

A detailed analysis of the first phase of the E.V.S. reveals:

(I) That the average flow rate corresponds very closely to the average hi.B.C, flow rate.

(2) That the average flow rate of this phase is a repeatable measure, which can be ascertained with accuracy, and from one examination to another the rate remains constant for e a c h person, as revealed by recognized statistical standards; furthermore the overall standard error is about +5 per cent.

(3) That the volume of air expired during this phase corresponds to the tidal volume of the M.B.C. of the subject.

There are occasions when the critical point is hard to locate; Kennedy measured the average expiratory flow rate over a known period using a. transparent protrac-

July. 1955 T U B E R C L E 199

tor. Experimentation determined the interval as the first 0.75 second of the E.V.S.; and from the volume expired in this period, which is equivalent to a near-optimal breathing rate of 4o respirations/minute, the estimated M.B.C. is calculated. This measurement he called the 'Estimated Flow Rate at 4 ° Breaths per l~linute' - shortened for convenience to E.F.R . 4°,

As compared with the Maximum Breath- ing Capacity the method has many advan- tages; it is rapid in execution, much less disturbing to a sick patient, it provides a record which on repetition has proved very constant for each individual (Kennedy, i953); the tracings reveal those breaths during which the patient has not co- operated fully, providing thereby an ob- jective check of what must remain inevitably a subjective test. It is apparent, too, that by this method a flow rate can be measured without the necessity of evoking those high respiratory rates which probe the spirometer error referred to already.

Comroe (I95I), in reviewing Pulmonary Function Tests, pointed out the exhausting nature of the M.B.C. assessment. This is a very real problem in the case of patients with active pulmonary tuberculosis, where such considerable respiratory exertions for I5-2o second periods (which need to be repeated perhaps several times to provide a true check) carry with them a certain risk. Kennedy's method is very much more acceptable on clinical grounds when applied to the tuber- culous patient, since obtaining a series of vital spirograms is neither exacting for the patient nor worrying to the physician.

Assessment of function in the tuberculous subject cannot stop at total figures relating to both lungs combined; information on individual lung function is often required when planning surgery. Surgical treatment today may often include both lungs, where function is impaired already by disease or by previous treatment, as by pleura thickened during artificial pneumothorax or by a diaphragm rendered atonic by repeatedly crushing the phrenic nerve.

Method The fasting patient is given pentobarbitone i~ grains one hour before passing the tube, foUowed half an hour later by omnopon I/6 grain and scopolamine I/I5O grain. Tile larynx and trachea are prepared as for bronchoscopy, butacaine sulph. ('Butyl') 4 per cent has proved to be the most effica- cious substance for topical use, and it is not usual thereafter for the subject to cough, but a spray of butyl is adequate to deal with the contingency should it arise after intubation.

F I G . I.

. . . . . . . t

A tube made in this country, designed by Marsh in I95 I, which we have modified slightly, was found to b e more mechanically acceptable than the Carlens (i949) tube with which we started our investigations. The carinal hook is tied in a special slip knot, and the thread is passed through the tracheal tube; in this way the hook can be freed without danger of damage to the larynx by tightening the thread. The tube is passed using a curved metalqntroducer and, with practice, the cords are negotiated using in- direct laryngoscopy; very occasionally intu- bation by direct laryngoscopy was employed, a method which reflected inexperience in the earlier days. When the latex hook has passed the larynx the restraining knot is released, the tube is rotated and pa~sed down until tile hook engages tile carina; first the tracheal blocker is inflated, slowly to prevent in- ducing a cough, followed by inflation of the

200 T U B E R C L E July 1955

bronchial btockerl The patient is screened and the location of the tube confirmed, then a film is taken as a permanent record and the patient connected to the closed circuit.

Initially routine data are obtained on a slow-moving drum and then for the E.F.R. 4° the fast gear is engaged*. Before recording, the patient is instructed carefully in the technique of the method, and is given several trial runs with appropriate rest intervals until the routine is well Understood and his co- operation assured. Then he is asked to give from 6-8 maximum expirations into the c i r cu i t - a f t e r a pause a further 6-8 maxi- mum efforts are called for, and very oc- casionally, if results are not consistent, more are recorded; the patient is encouraged constantly to provide maximum efforts during these recordings, although, as will be seen, a range of average good expirations provides a close pattern of ratios, so that the

*The standard 'Double Benedict' model has been modified in several essentials to satisfy the needs of this method, and to provide a minimum of circuit zeslstance.

problem of incomplete co-operation can be surmounted.

This reproduction of tracings illustrates the pattern of recordings obtained by the method.

The tube is withdrawn at this stage and the patient is encouraged to cough and to clear all accumulated secretions. The time needed to obtain differential measurements as described, additional to the preceding routine bronchospirometry, is about three to five minutes.

After a few minutes of rest the patient is told to breathe into a closed spirometer cir- cuit, and the orthodox E.F.R. 4° and Vital Capacity tracings are obtained at the same session.

Results. Bronchospirometrlc Findings Differential readings of a sample of 2o among the first 2oo bronchospirometric studies carried out at Colindale Hospital are

$ P I ~ M L ~ [ R RECOt~D

- - - - h i . . . . . - : l " !...-w

FIG. 2.

July 1955 T U B E R C L E 201

presented here to illustrate the quality of measurement of the E.F.R. 4°. At first two cases are shown, representing differing

FIG. 3"

emphasis of air-shift by the participating lungs. It can be seen how a ratio is obtained, with a fair degree of constancy, of the

Fro. 4.

relative air-shifts by the two lungs: these ratios are applied later to measurements obtained by spirometry.

Case z . - To illustrate physiological distribu- tion of air-shift between R. and L. lungs.

Mean Standard

error S.c. per cent

of mean

E.F.R2 ° (litres per mln.)

R. lung L. lung R 42.o 3 o.o 46.o 33 "5 46 "5 34 .o 48.o 34.o 48.o 34.o 48.o 34"o 5o-o 36.o

47 .o 33.6

2 . 9 2"2

6-n 6. 4

R. R. +L.

+L. per cent ,2"o 58.4 '9 "5 57 "9 I°'5 57 "8 12.o 58.5 12.o 58.5 ~2"o 58-5 ~,6.o 58.2

Io.6 58-5

5.2 0.26

6. 3 o.45

Case 2 . - T o illustrate unilateral predomi- nance. (Note the bronchospiromet W tube in situ.)

Mean Standard

error S.c. per cent

of mean

E . F . R . 4o

(lilres per rain.)

R. luni L. lung 39 .0 x2"5 5 x'5 4 x .o x3.o 54.0 41 .o i4.o 55.o 42"o x4.o 56.o 42.0 i5.o 57.0 44"o I5"o 59"o

41 "5 I4"° 5 5 " 5

2 .o I -o 3 .o

4 .8 7 "I 5"4

R. R . + L per Cell

75.8 76.o 74"6 75"o 73.6 74.6

74"9

0"87

I ' 2

Every case has the data tabulated as above, from which the figures in Table I are ob- tained.

These columns demonstrate how with wide variations between maximum and minimum flow rates, due to varying degrees of co-operation on the part of the patients, ratios of air shift by each lung remain constant.

These ratios can be applied thereafter to the total Flow Rate as determined by spirometry.

202 T U B E R C L E July 1955

TABLE I E.F.R. a° (litres per rain.)

Case ~rO. I

2

3 4 5

6 7 8 9

IO

I I i2

I3 I4 I5

i6 17 I8 I9 20

R. lung Mean Range 47"O 8"O 41 "5 5 .0 23" 5 I2" 5 33"O 9"0 I6" 5 5"0

IO" 5 I "O 35"5 IO'O 20"5 5"O 36"0 I5"O I8"O 4"0

50"5 IO'O 29"o 6"O 27" 5 8" 5 X7"O 16"O 15" 5 7"0

35-0 i6.o 3 o.o 2.o 37"o 5"5 27"5 6.0 38.0 I2;O

L. lung Mean Range

33.6 6.0 i4.o 2. 5 i o - o 5"o I3"O 3"5 i8.o 6.0

20.0 I "5 26"0 7"O I5" 5 4"0 27" 5 I2" 5 I7"O 4"0

54'5 I4"° 31 .o 6.0 20.0 6. 5 i9.o 16. 5 9 .0 3"5

20. 5 8.0 43"o 6.0 23.o 3"5 22. 5 4.0 35.0 I4" 5

R. + L . Mean -4- s.e.

80 "5 5 "2 55"5 3 .o 33"5 6.I 46.o 4"4 34"5 4"7

30.5 I "o 61.5 6"3 36"0 3"6 63"5 10. 9 35"° 3"4

IO5.O 8. 4 59"5 5 .2 47'5 5"3 36.0 I2"O 24"5 3"7

55 "5 8 "4 73"o 3"o 60.0 3"2 5 o.o 3"9 73"° 9"3

R/R. +L. per cent

lllean -b s.e. range 58.5 0.26 0- 7 74"9 o'87 2"2 7o.o o '77 2-5 7 I '5 o'53 I ' 5 47"7 o.6o i-4

34.2 0.67 I ' 7 57"7 0"92 2"5 56"4 0"39 I ' o 57,0 o '9 I 2" 3 5 I ' 6 0"95 2"2

48.2 0.63 1.8 48"3 o ' I 3 0"3 57"4 0"25 0"7 47 .8 0"67 ! ' 8 63- 7 I-o 5 3"0

62. 9 I .o 9 3"x 41.2 0.63 I ' 7 6 I ' 6 0"70 2"0 55"2 0"87 2-2 5 x'9 0"84 2"4

In T a b l e I I rat ios found by broncho- sp i romet ry are appl ied to flow r a t e s measured spirometrical ly.

TABLE I I Broncho- Spiromelry

I spiromelry Ratio

Case.A~o. (R/tot.%) E.F.R. *° (L./min)

By calculation

E.F.RA ° (L./Min) R. lung L. lung

2

3 4 5 6 7 8 9

IO I I I2

I3 14 x5 16 17 i8 x9 20

58 "5 73"5 70.2 72.o 47 "5 34 "5 58.o 56 "5 57"5 51 "5 48-o 48 "5 57 "5 47 "5 63"o 63"o 41 .o 62-o 55"o 51 .o

9 o.o IO0"O

50.0 6o-o 69.o 74"o

io8.o 41 "0

I09"O 68.o

i5 i . o 64"o 68.o 62.o 36.o 7o'o 91 .o 67-o

IO9.O 96.o

52 "5 37 "5 73 "5 26 "5 35.o x5.o 43"o x7.o 33"o 36.o 25 "5 48 "5 62 "5 45"5 23.0 I8"O

6 2 "5 46"5 35"o 33"o 72 "5 78"5 31 -o 33.o 39.o 29-o 29 "5 32 "5 22. 5 13- 5 44.o 26.o 37 "5 53"5 41 !5 25- 5 6o.o 49.o 49"o 47"o

T a b l e I I I gives the sum o f E .F .R . 4° measured by b ronchosp i romet ry , fol lowed by the cor responding figure ob ta ined b y

Case aVo. I

3 4 5 6 7 8 9

IO I I I 2

I3 14 I5 x6 x7 i8 I9 20

TABLE I I I

Broncho- spirometry R.+L.

E.F.R. ao 8 o ' 5

55 "5 33 "5 46-o 34"5 3o'5 6I "5 36.o 63 "5 35"o

io5-o 59 "5 47 "5 36.o 24"5 55 "5 73"o 60"O

5 o.o 73"o

Spirometry

Total E.F.RA °

90.0 I OO'O

5o.o 60.0 69.o 74"o

io8.o 4 x .o

IO9.O 68.o

I5I .o 64.o 68.o 6_o.o 3 6.o 7o'o 9x .o 6 7.o

xo9.o 96.o

E.F.R2 ° Bronchy Spiromy per cent

89 "5 55 "5 67"o 76 "5 50"0 4 t "o 57"° 88"o 58"o 51 "5 69" 5 93"° 7 o 'O 58.o 68.o 79 "5 8o.o 89"5 46.o 76.o

July 1955 T U B E R C L E 203

spirometry in order to measure the limita- tions caused by the presence of a tube in the trachea.

Discussion It is the aim of this paper to outline a practicable method of determining the maximum volume of air that can be expired by individual lungs in unit time.

Bernstein (I954) in a critical survey pointed out an error inherent in many standard spirometers which appears during fast expiratory efforts, due to oscillations in the water-jacket. To illustrate the point tracings were shown, taken from one patient, revealing -oscillations - on the Knipping curves, but not on those from an improved model. It is of interest, however, that these oscillations develop in the lower, later phases of the tracings and do not affect materially the flow rate during the first 0.75 second of expiration.

In discussing the pulmonary function tests in common use, Con/roe (I95i) voiced the justifiable criticism of bronchospiro- metry that breathing through narrow tubes is unnatural and evaluation of results is difficult.

Breathing through tubes ceases to be physiological when the demand for air exceeds the capacity of the tubes to deliver the air; for example, a person breatbes comfortably through unobstructed nostrils when at rest and during mild exercise, but the 'capacity' of the nostril fails during greater exertions when oral breathing commences.

Modern designs of bronchospirometry tubing aim at providing the widest possible airways, so that provided the correct size of tube is employed in each patient, an airway is available to each lung larger in cross- section than the corresponding nostril. I f care is taken, therefore, to limit the patient's activity while measuring his respiratory function the tubing will permit adequate airways without that subjective discomfort which can cause unphysiological over- breathing. The limit is exceeded when

attempts are made to ascertain the Maximum Breathing Capacity; forced in- spiratory-expiratory efforts repeated for z5-2o seconds provide a very real distur- bance to the patient; coughing is evoked and dyspnoea and revolt against the closed circuit is experienced. On the other hand it is unusual for a patient subjectively to find difficulty in providing the 6--8 maximum expiratory efforts required for Kennedy's E.F.R. 4° assessment, which becomes thereby a most practicable method for use with bronchosp!rometry.

Objectively, the limit set by a tube in the trachea must be recognized and compen- sated - it would be invalid to measure rapid air flow from individual lungs through two relatively narrow tubes and to presume that the sum of these represents the physiological air-shaft.

The method which we advocate here is to obtain by bronchospirometry the contribu- tion of individual lungs - subjected as each is to the s a m e limiting factor (the area of cross-section of each tube is the same). This contribution, expressed as a ratio; can ' then be applied to the true flow rate measured iby spirometry without intubation. .... -,~,~.

Table I shows that separate lung assess- ments can be performed with reasonable constancy (S.e of R/R 4- L per cent usually less than i.o) and further that less thar~ maximum efforts provide this same con- stancy of ratio - an important point when considering an intubated subject.

Table II demonstrates the application o f these ratios to flow rates obtained by orthodox spirometric means.

From Table I I I can be seen the differences between additive b ronchospirometry totals and the figures measured by spirometry. Since three sizes of tubes are available, these differences refec t two va r i an t s - t i l e cross-sectional areas both of the broncho- spirometry tubes and of the patient's trachea and bronchus. As an academic exercise it is intended, if necropsy material be available from a subject who has had a recent assess-

204 T U B E R C L E Ju~ 1955

ment o f function, to relate the d iameter of the t rachea and bronchus in which the tube had been seated to the sum of these dia- meters found, by calculation, f rom the formula: E.F,R 4° ofR.+L, lungs bybronchospirometry = 2 rr r 2

E.F.R ~° of both lungs by spirometry 7r (x2-t-y ')

where r = r a d i u s of the tubes, x and y = radius o f the t rachea and bronchus respectively.

Summary A br ief review has been m a d e of methods of assessing vent i la tory funct ion wi th special appl icat ion to the tuberculous pat ient , who presents the par t icu la r p rob lem o f varying types and extent o f disease in bo th lungs and for wh om surgical t r ea tmen t may be neces- sary on one or bo th sides. Of ten it is desirable to assess each lung separately, and various dynamic methods o f measur ing venti lat ion are surveyed. Kennedy ' s in t roduc t ion of the Est imated Flow Ra te at 4o breaths per minute (E.F.R. 4°) is accepted as being a good prac t icable me thod to apply to the tuberculous pat ient . This p a p e r outlines the appl icat ion o f the me thod to broncho- spirometry, whereby ratios o f funct ion as between individual lungs are obtained. I t is emphasized tha t the ratios so ob ta ined must be appl ied to flow rates ob ta ined by or thodox spi rometry before a t rue est imate of the flow rate f rom each lung can be obtained.

T h e m e t h o d is rapid, adding only five minutes to the per iod o f i n t u b a t i o n normal ly needed for o ther bronchospirometr ic measures. I t is impor t an t tha t these dynamic measurements o f vent i la tory power should not replace, bu t should supplement the o ther well-tr ied methods o f assessing respir- a to ry capacity.

We would like to thank M r B. Benjamin for his advice over the presen ta t ion of tables,

Mrs M . J . Cur ry for her pat ient secretarial services and Miss Shaw for the pho tog raph ic reproduct ions.

References Bernstein, L. (z954) Thorax m, 63. Bernstein, L., and Mendel, D. (t95 l) Thorax, w, 297. Carlens, Eric (x949) 07. Thor. Surgery, xvm, 742. Comroe, J. H. (x95x) Amer. J. ~lfed., x, 356. Gaensler, E. A. 095 o) J . Allergy, xxr, ~3 -o, Gaensler, E. A. (x95x) Science, c.xtv, 444- Gilson, J. 121., and Hugh-Jones, P. 0949) Clin. Sci., vxr, x85. Hermannsen, J. (x933) Z. ges exp. Med., xc, x3o. Kennedy, M. 121. S. 095 o) Beltr. Silikose-Forsch., x, 19. Kennedy, M. 121. S. (z953) Thorax, vm, 73. Marsh, K. (I95 Q Verbal Communication. Brit Tub.

Assocn. Annual Conference (Cambridge).

Annual Report K E N T C O U N T Y COUNCIL. Annual Report

of the Medical Officer of Health, A. Elliott, for the Year i953 . Health Department, County Hall, Maidstone. September z954.

This annual report upon the health of Kent 's population of 1,558,9oo persons has its usual unattractive set-up. From it we gather that the County had a birth-rate of 14. x and a death-rate of z x "4, based on z 7,882 deaths, 7 o.5 per cent of which occurred at ages 65 and over. In I938 only 55"4 per cent of all deaths were at these late ages.

The infant mortality rate was as low as 22.2. Bronchitis contributed 977 deaths, pneumonia 7io, and tuberculosis (all forms) 285. Cancer of the lungs and bronchus claimed 54 ° deaths, oi which the males were nearly six times the females. There were z75 male deaths from pulmonary tuberculosis, of which only 5 were at ages under 25, and 124 at ages 45 and over; of 85 female deaths only 5 were under ages 25. Notifications declined from x.697 in x952 to z "402. Twenty-three chest clinics are maintained in the county in charge of chest physicians who organize the tuberculosis health visitor service. There were 4,7o9 contacts examined among whom z4o new cases were found. BCG vaccina- tion was given to I,o55 persons in close contact with patients suffering from tuberculosis. No reference is made to the waiting llst, to any domiciliary treatment, or to the beds available for institutional treatment.

The spot light of the report is an account of a day with the ambulance service.