There was no significant difference in mean alveolar .... characteriziry the pressure/flow relationship is satisfactory only ... Alveolar pressures and flow rates were.
4 8 ~
Medical Research Society
t h e alveoli. The diagnostic value of t h i s index i s diminished i f its physiological v a r i a b i l i t y is unknown. Five experienced laboratory s t a f f , 3 male and 2 female aged between 25 and 49 years, performed six nitrogen washout t e s t s s e r i a l l y on two separate occasions. Gas concentration was measured w i t h a mass spectrometer and flow by a heated i n l i n e Fleisch-pneumotachograph. Data was analysed by a KOntron PS180 microcomputer. There was no s i g n i f i c a n t difference i n mean alveolar mixing efficiency on t h e two occasions (7613% f SD 8.4 - 76.7% f 5 . 2 ) . The l a r g e s t individual range over a s e r i e s was 15.1%; t h e The mean difference smallest was 1.5%. between individual highest and lowest r e s u l t s over both s e r i e s was 8.1%. Individual c o e f f i c i e n t s of v a r i a t i o n (CV) ranged from 7.5% t o 0.7%; mean CV’s f o r each s e r i e s was 3.4% and 4.34% respectively. The r e p e a t a b i l i t y of t h e t e s t has been demonstrated on a b e l l - j a r model t o be high (mean CV = 1.4% n = 3 6 ) ; t h e difference must represent physiological variability.
135
TEE ROLE OF HORMONES IN TH3 GENERATICN OEDEMA I N CQL PULMONALE
OF
T. W. EVANS, A. McKEEVER, G. BARER, I.HENDEXLSW, and P. HWARD Deparhent of Medicine and Zoology, Cniversity of Sheffield, Sheffield SlO 2JF
Two theories attempt t o explain t h e presence of oedema in p a t i e n t s with c o r pulmonale secondary t o chronic o b s t m c t i v e airways disease. A conventional view regards failure of t h e h e a r t aa a pump t o cause poor renal perfusion, a c t i v a t i o n of t h e renin angiotensin system and secondary sodium and water retention. However ri&t v e n t r i c u l a r muscle function is not compmised by t h e increase in afterload afforded by pulmonary hypertension. Left v e n t r i c u l a r function i s s i m i l a r l y unaffected and cardiac output is n o m a l or s l i & t l y elevated during the acute and convalescent phapes of exacerbations of An a l t e r n a t i v e approach c o r pulmonale. regards endocrine a l n o m a l i t i e s as responsible f o r t h e f o m a t i o n of oedema i n such patients. Rats subjected t o a three week period of hypoxia develop anatomical changes i n t h e h e a r t a$ pulmonary vasculature similar t o these found i n patients. In a a e r i e s of experiments u s i n g this model, plaana renin a c t i v i t y (PRA) and p l a m a concentrations of aldosterone, a n t i d i u r e t i c hormone (.4W)and corticosterone were measumd in control and hypoxaenic rats, over a 3 week period and the d i s t r i h t i o n of body water measured terminally. There w a s a progressive r i s e i n PRA with a tenfold elevation in aldostemne l e v e l s in experimental animals compared with controls. However, plaana sodium increased marginally and p l a m a volume remained normal O r even f e l l in some instances. AX3 concentrations were reduced in hypoxaemic rats. Despite hi& and increasing aldostemne and PRA concentrations during hypoxia, sodium and water retention was not detected. Hypoxia m a y thus inhibit the a c t i o n s of these hormones.
136
DOES D I V I N G EXPOSURE INDUCE AIRFLOW OBSTRUCTION? I.S. DAVEY, J . E .
COTES and J.W. REED
Departments of Occupational Health and Hygiene, and Physiological Sciences, The University, Newcastle upon Tyne. NE2 4AA. the basis of cross-sectional information Cmsbie and colleagues suggested t h a t airflow obstruction might be an occupational r i s k of divers (J. appl. Physiol. 1979, 46, 639-45). This i n t e r p r e t a t i o n was disputed by Bouhuys and Beck (Ibid. 1979; 1136). W e have used r e s u l t s of measurement of forced expiratory ) and forced v i t a l capacity (FVC) volume (FEV contained ii’?he Decompression Sickness Registry together with flow volume curves obtained with a McDermott spirometer on 81 l o c a l divers t o explore the position further. Allowance was made for age, s t a t u r e and smoking: except where in-dicated a 1% probability was accepted a s significant, On
z,
Cross-sectional analysis of t h e r e s u l t s for 858 divers confirmed the association of FVC w i t h diving exposure observed by Cmsbie. However, as suggested by Bouhuys and Beck the negative correlation between FEVg of N C and FVC as percent of predicted applied t o divers independent of age and also t o a control non-diving population. FEV$ was correlated negatively w i t h the maximal depth t o which a diver had been exposed and.positively w i t h years of diving. For t h e 81 local divers the FEF 25% FVC was reduced compared w i t h the reference value and negatively correlated w i t h years of diving; t h i s observation is evidence for diving exposure a f f e c t i n g small lung airways. Longitudinal analysis of t h e r e s u l t s over 5 years for 255 men showed a j u s t s i g n i f i c a n t association @ < 0 . 0 5 ) between r a t e of change of FVC per annum and progression of diving exposure. In divers who reduced t h e i r diving exposure the r a t e of decline of FEV1.O and FVC appeared t o be increased. ‘Ihe r e s u l t s suggest t h a t any beneficial e f f e c t of diving is temporary: the long-term sequelae need t o be examined further.
137 THE
EFFECP OF FWW 2ATE CN 6 DIFFERENr CIlARACIERIZING THE PRESSURE/FLOW RELATIONSHIP OF ‘MEAIWAYS OF
S.J.JF”IMS,
J . B . m AND G.M.CXHRANE
Dept. of Respiratory Medicine Guy’s Hospital, London SEl 9FS Although a s e n s i t i v e measure of airway obstruction, the standard method (CuBOis) of characteriziry the pressure/flow relationship is s a t i s f a c t o r y only when it approximates a s t r a i g h t line. This condition is not met i n p a t i e n t s with severe obstruction (Alpers & Guyatt, C l i n Sci 1967;67:1-10) or i n normal healthy people a t high flow rates. This study examines the e f f e c t s of flow amplitude on ‘the Dubis method i n comparison with 5 alternatives.
49P
Medical Research Society Alveolar pressures and flow rates were measured in 6 normal healthy people during panting manoeuvres performed at a range of flow amplitudes between .5 and 5.5 l/s. m e data was analysed using 6 different methods: Rs,-slope of pressure/flow curve between f.5 l/s (Ixlbois): Ri,-peak pressure and flow: Rev,-pcessure and flow at mean lung volune: Rff,-peak flow and pressure at same instant: R€,- pressure and flow from Fourier analysis and M , - a least quared difference fit in a linear htmIogenous model. At flow amplitudes of less than 2.5 l/s the coefficients of variation between the 6 methods were less than 15% in 85% of the manoeuvres. At 5 l/s four of the methods (Rev, Ri, F&, M)remained within 15% but Rs was about half their value. The discrepancy between these four methods and that of -is is apparent at flow rates which occur during exercise. This effect is imprtant to the measurement of 'resistance' in patients with airways obstruction since their pressure/flow plots at low flow rates are similar in shape to those fran normals at high flows. Each of these methods can easily be wrfonned on a micro-canouter. (Xlr results suggest that Ri, which &n be evaluated hand, is preferable to the DuBois methcd.
solution. A consistent r i s e in hydrogen concentration occurred f o r 30 minutes vs b a s a l This ' ' l e v e l s , mean r i s e = 10 + 10 PPM (W,.05)f r i s e was suppressed by p r i o r teethbrushing and Chlorhexidine mouthwash, mean = 2 + 3 PPM (P)o.% Thus, f o r optimal measurement of-end-expiraby hydrogen concentrations using an electrochemical c e l l , s u b j e c t s should be relaxed,resbsd, non-smoking, and avoid additional carbohydrate. Caution i s necessary before i n t e r p r e t i n g an e e r i s e in concentration of hydrogen as rapid transit unless o r m c r o f l o r a a r e suppressed. *(paired t
-
test)
13 9 THE EFFECT OF DIFFERENT DOSES OF SODIUM CROMOGLYCATE ON COLD AIR-INDUCED ASTHWA
J.N.
STAINFORTH AND R.A.
LEWIS
Medicine I,Southampton General Hospital, Southampton. SO9 4XY
*. EXHALED BREATH HYDEOGEN CONCENTRATION: FACIl3R.S INnuENCING TIE ACCURACY OF ITS ...
1
MEASURPWT I N MAN D.G. S. W
THOMPSON, P. BINFIELD, A. DE BELDER, m AND M. WILSON
Medical Unit and Department of Physiology, The London Hospital, London, El IBB Colonic b a c t e r i a l metabolism of carbohydrate r e s u l t s in lydrogen production which then appears in exhaled breath. A r i s e i n endexpiratory breath hydrogen concentration'after ingestion of non-absorbed carbohydrate thus signals its a r r i v a l a t the caecum and provides E. measure of upper i n t e s t i n a l t r a n s i t (Bond J.H., L e v i t t M.D., J. Lab. C l i n . Med. 1974, 85, -546). A s e n s i t i v e electrochemical c e l l f o r rapid brsatf, hydrogen measurement is now a v a i l a b l e (G.M.I. L t d Renfrew) and the technique is becoming increasingly employed i n human research. Wehave tested t h i s technique and i d e n t i f i e d s e v e r a l f a c t o r s which influence its accuracy. Hyperventilation and mild exercise: S e r i a l b r d h hydrogen samples were measured in 7 subjects, at r e s t , a f t e r 39 seconds hyperventilation, and l a t e r , a f t e r walking. Both a c t i v i t i e s reduced the recorded hydrogen concentration compared t o r e s t i n g levels. For hyperventilation, mean reduction = 14 + 5 (SD) p a r t s per million (PPM) (PQ.01): For calking = 10 + 7 PPM (p(0.05): CiRarette Smoking: A consisfent r i s e in measured values above basal were found during smoking i n 7 subjects, mean change = 70 + 48 PPM (P(O.01): This r i s e was g r e a t e r than explicable by presence of Carbon Monoxide ( t o which the c e l l is a l s o s e n s i t i v e ) . O r a l Anaerobic Microflora: 7 fasted subjects performed a 2 minute mouthwash with 20% sucrose
The sodium cromoglycate (SCG) metered dose inhaler (MDI) delivers lmg o f SCG compard to 20mg SCG from 1 spfncap. Initial trials found no dffference f n efffcacy between the recomnended doses of SCG nly MDI (2mg qdsl and spincaps (2Omg qds), despite the 10-fold dffference f n dose. Me compared the e f f e c t o f d i f f e r e n t doses o f SCG given by MDI and spi nhaler i n protectf ng against col d-f nduced bronchoconstrictfon i n asthmatfc patients. Ten (Em, 2F) mfld, atopic asthmatic subjects, mean age 28 years and mean FEY1 95% predicted were studied. They inhaled 2mg SCG by MDI, lOmg SCG by MDI. 201119 SCG by spinhaler or matched placebo on separate occasions i n random order. sGaw was measured i n a body plethysmograph before and 15 min a f t e r placebo o r SCG. Cold challenge was then performed by the subject hypervent i l a t f n g cold a i r under iscapnic conditions f o r 5 mfn (VE = 30 + 0.58 SM L/min), temp insp a i r = -8.5 +-0.27 C). A f t e r challenge sGaw was mezured a t 2 min fntervals f o r 20 min. and then every 5 min f o r a f u r t h e r 20 min. lOmg SCG produced a small increase I n sGaw after-jnhalation from 1.22 t o 1.34 skPa (p
