Basic Res. Cardiol. 73, 497-505 (1978) 9 1978 Dr. Dietrich Steinkopff Verlag, Darmstadt ISSN 0300-8428
Department of Physiology, University of Ou]u, Oulu (Finland)
P u l m o n a r y c i r c u l a t i o n in the r e i n d e e r P u l m o n a l k r e i s l a u f b e i m Rentier J. T i m i s j ~ r v i
and L. H i r v o n e n
With 6 figures and 1 table (Received J a n u a r y 24, 1978) Summary Right heart catheterizations were performed in 56 sessions on 25 reindeer with determinations of blood pressure and oxygen saturation. Cardiac output was calculated from cineangiocardiograms. When the animals were placed in prone position, heart rate was about 50/rain, m i x e d venous blood oxygen saturation 68 to 72%, right ventricular systolic pressure 27 mmHg, p u l m o n a r y arterial pressure 25/18/11 mmHg, p u l m o n a r y arterial wedge pressure 6-8 m m H g and p u l m o n a r y transfer time 4 to 5 cardiac cycles. When the animals were placed on their side, the heart rate rose to 90 b/rain, mixed venous blood oxygen saturation decreased by about 4% and the right ventricular and p u l m o n a r y arterial pressures increased by about 10 m m H g ; p u l m o n a r y arterial wedge pressure did not change. Hypoxemia led to an increase in heart rate, cardiac output and pulmonary arterial pressure; the latter two measures tended to increase whenever the heart rate increased. U n d e r the conditions stated here, an increased p u l m o n a r y vascular resistance was calculated w h e n p u l m o n a r y arterial pressure was increased. T h e r e i n d e e r is a r u m i n a n t i n d i g e n o u s to t u n d r a a n d t a i g a a r e a s s h o w i n g a h i g h l e v e l of a d a p t a t i o n to t h e s e c o n d i t i o n s . O l d e r s t o c k s of r e i n d e e r w e r e o n c e s u b j e c t e d to a n n u a l m i g r a t i o n s ; t h e s e a r e o n l y of v e r y l i m i t e d e x t e n t n o w a d a y s w i t h t h e a d a p t i o n of a n o r g a n i z e d h e r d i n g s y s t e m . T h e r e i n d e e r is n e v e r t h e l e s s e x p o s e d to t h e d e m a n d s of p h y s i c a l a c t i v i t y , for i n s t a n c e i n p u l l i n g s l e d g e s a n d for c a r r y i n g l o a d s , a n d t h e s u r v i v a l of e a c h a n i m a l d e p e n d s to a g r e a t e x t e n t o n its a b i l i t y to d i g for l i c h e n u n d e r t h e snow in winter. T h e v o l u m e s a n d f u n c t i o n i n g of t h e r e i n d e e r h e a r t r e a c t r a p i d l y to v a r i o u s s t i m u l i a n d m a r k e d p o s t u r a l c h a n g e s (1). T h e h e i g h t e n e d p u l m o n a r y v a s c u l a r r e a c t i v i t y of b o v i n e s p e c i e s to v a r i o u s i n t e r v e n t i o n s s u c h as h y p o x i a a n d e n d o t o x i n h a s b e e n r e c o g n i z e d e a r l i e r (2, 3), a n d s p o n t a n e o u s p u l m o n a r y h y p e r t e n s i o n h a s b e e n n o t e d i n b o v i n e c a l v e s (4). T h e p r e s e n t work concerns the pulmonary circulation in the reindeer, especially during hypoxia.
Material and m e t h o d s Right heart catheterization was performed through the jugular vein in fifty-six sessions on twenty-five reindeer (Rangifer tarandus tarandus L.) five to eighteen m o n t h s of age and ranging in weight from 19 to 44 kg. The right atrial, ventricular, and p u l m o n a r y arterial pressures were recorded with a Statham pressure trans759
498
Basic Research in Cardiology, Vol. 73, No. 5 (1978)
d u c e r (Type 53210~ P 37), a n e l e c t r o m a n o m e t e r a n d a M i n g o g r a p h 34 jet r e c o r d e r (Elema-SchSnander, Stockholm). Blood oxygen saturations were measured with an O x i m e t e r - D e n s i t i o m e t e r ( T y p e 351, N o 140, A / S N y c o t r o n , Oslo). C i n e a n g i o c a r d i o g r a m s w e r e r e c o r d e d in r i g h t l a t e r a l p r o j e c t i o n w i t h a n i n e - i n c h Siemens image intensifier and an Arriflex camera (Siemens Aktiengesellschaft, E r l a n g e n ) a t a s p e e d of 30 f r a m e s p e r s e c o n d . U r o g r a f i n | 76% ( S c h e r i n g - L e i r a s , T u r k u ) , 1 rnl p e r k g b.w. dose, w a s u s e d as t h e c o n t r a s t m e d i u m ; a n d t h e a n i m a l w a s p l a c e d e i t h e r o n its s i d e or in p r o n e p o s i t i o n d u r i n g f i l m i n g . T h e s t r o k e v o l u m e for c a r d i a c o u t p u t d e t e r m i n a t i o n w a s c a l c u l a t e d f r o m t h e c i n e a n g i o c a r d i o g r a m s b y a g e o m e t r i c m e t h o d p u b l i s h e d p r e v i o u s l y (5). T h e p u l m o nary circulation time was estimated from the time difference between visualization of t h e p u l m o n a r y a r t e r y to t h e v i s u a l i z a t i o n of t h e left a t r i u m . L i d o c a i n w a s u s e d as a local a n a e s t h e t i c . S e d a t i o n w a s i n d u c e d u s i n g 1.2 to 1.5 m g d i a z e p a m p e r k g b.w. i n t r a v e n o u s l y . D e e p e r a n a e s t h e s i a w a s i n d u c e d w i t h 5 to 20 m g p e n t o b a r b i t a l s o d i u m p e r k g of b.w. E n d o t r a c h e a l i n t u b a t i o n or t r a c h e ostomy with positive pressure ventilation were used during pentobarbital anaest h e s i a if b r e a t h i n g i r r e g u l a r i t i e s o c c u r r e d . H y p o x i a w a s i n d u c e d b y m e a n s of a 10% m i x t u r e of o x y g e n i n n i t r o g e n o r b y i m p a i r m e n t of r e s p i r a t i o n u n d e r p e n t o b a r b i t a l sodium.
Results Anatomy of the reindeer right ventricle The thickness of the right ventricular free wall of five autopsied animals with a heart weight of 350 to 400 g ranged from 3 mm at the intervent r i c u l a r s u l c u s t o 12 m m a t t h e s i t e o f t h e p a p i l l a r y m u s c l e . T h e m i d p o r t i o n o f t h e w a l l n e a r t h e p a p i l l a r y m u s c l e w a s 9 t o 10 m m t h i c k . D u r i n g e j e c t i o n
Fig. 1. A n g i o c a r d i o g r a m of a 5 - m o n t h - o l d r e i n d e e r i n l a t e r a l p r o j e c t i o n . C o n t r a s t m e d i u m w a s i n j e c t e d i n t o t h e r i g h t a t r i u m . A: r i g h t v e n t r i c l e i n diastole. B: r i g h t v e n t r i c l e i n systole. P u l m o n a r y a r t e r i e s are v i s i b l e i n t h e u p p e r p a r t s of t h e p i c t u r e s .
Timisj~rvl and Hirvonen, Pulmonary circulation in the reindeer
499
Table 1. Pressure values for the pulmonary circulation in the reindeer under various conditions (mm Hg). Condition
Control
n
18
P u l m o n a r y arterial pressure Right Right atrial ventricular systohc diastolic m e a n pressure pressure
wedge
2- 6
6-8
P u l m o n a r y hypertension: Uncontrolled 25 2-10 Hypoxic 20 4-15
22-27
20-27
10-12
16
up to 60 up to 150
up to 60 up to 35 up to 42 up to 150 up to 90 up to 110
6-8 up to 20
a l l t h e d i m e n s i o n s of t h e r i g h t v e n t r i c u l a r c a v i t y d e c r e a s e d a n d t h e f r e e c h a m b e r w a l l t h i c k e n e d (fig. 1). P a r a m e t e r s o f t h e p u l m o n a r y circulation u n d e r c o n t r o l c o n d i t i o n s The various pressures recorded under control conditions are given in T a b l e 1. T h e m e a n p u l m o n a r y c i r c u l a t i o n t r a n s f e r t i m e w i t h r e g u l a r c a r d i a c r h y t h m w a s f o u r t o f i v e c a r d i a c c y c l e s (in f i f t e e n a n i m a l s ) c o r r e s p o n d i n g t o f i v e s e c o n d s a t a h e a r t r a t e of 50 t o 60 b / r a i n . T h e o x y g e n s a t u r a t i o n of p u l m o n a r y a r t e r i a l b l o o d ( m i x e d v e n o u s b l o o d ) w a s 68 to 72% in f i f t e e n successive experiments on eight animals in prone position; the corres p o n d i n g v a l u e s w h e n t h e a n i m a l s w e r e p l a c e d o n t h e i r s i d e w e r e 64 to 68 per cent. P u l m o n a r y arterial h y p e r t e n s i o n Pulmonary arterial pressure in the reindeer was labile. It could be increased during controlled procedures, but would also increase in an u n c o n t r o l l e d m a n n e r ( T a b l e 1). A g r a d u a l i n c r e a s e in p r e s s u r e w a s o b s e r v e d w i t h i n h a l f a n h o u r of t h e i n t r o d u c t i o n of t h e c a r d i a c c a t h e t e r i n animals under mild sedation without any other measures. The pressure i n c r e a s e s t a r t e d 5 t o 10 m i n u t e s e a r l i e r a n d w a s m o r e p r o n o u n c e d in t h e a n i m a l s k e p t o n t h e i r s i d e . H o l d i n g of b r e a t h , t h e V a l s a l v a e f f e c t , a n d s o m e t i m e s a l s o r u m i n a t i o n w e r e o b s e r v e d a t t h e i n i t i a l s t a g e of t h i s p r e s s u r e r i s e . A s p o n t a n o u s d e c l i n e i n p r e s s u r e to a r o u n d t h e i n i t i a l l e v e l o c c u r r e d w i t h i n 30 t o 120 m i n u t e s . A o r t i c a n d m i x e d v e n o u s b l o o d o x y g e n saturations were reduced during the hypertensive period. Pentobarbital sodium administration was rapidly foUowed by respiratory irregularities ranging from periodic ventilation to apnea, by reduced arterial oxygen saturation and by pulmonary hypertension. Other effects n o t e d w e r e i n c r e a s e d s a l i v a t i o n , b l o a t i n g of t h e a b d o m e n a n d r e g u r g i t a t i o n of t h e r u m e n c o n t e n t s l e a d i n g to a n e c e s s i t y f o r e n d o t r a c h e a l i n t u b a tion. H y p o x i a i n d u c e d b y a n a t m o s p h e r e of 10% o x y g e n in n i t r o g e n c a u s e d the heart rate, right atrial and ventricular and pulmonary arterial pressures t o r i s e ( T a b l e 1). T h e s e t h r e e t y p e s of p r e s s u r e r i s e : u n c o n t r o l l e d , i n d u c e d b y p e n t o b a r bital and induced by anoxic hypoxia, caused parallel changes in the pulmonary circulation and could not be distinguished from one another
Baslc Research in Cardiology, Vol. 73, No. 5 (1978)
500
._c 200 . E
o~ -1-
E E
_(3 ILl F"" rr t--
n-
150-
< -r 100
10(
HR 50 PPAS
PPAs PPAM PPAM
50-
Z 0
HR N
I
70
I
I
p
80 90 100 AORTIC OXYGEN SATURATION %
Fig. 2. Heart rate (HR), p u l m o n a r y arterial systolic (PPAs) and m e a n (PPAM)pressures plotted against aortic blood oxygen saturation (So2). Solid lines indicate prone position and dotted lines side position. Equations for the curves: HR (prone) = -0.146(So~) 2 + 20.2(So~) - 518, index of fit 0.780, n = 16; HR (side) = -0.044(So2)2 + 4.2(So~) + 104, index of fit 0.600, n = 32; PPAS (prone) = -0.039(So~)2 + 5.1(So2) - 92.2, index of fit 0.815, n = 27; PPAS (side) = 0.0007(Soz)2 - 0.67(So~) + 99.6, index of fit 0.411, n = 48; PPAM (prone) = -0.019(So~)2 + 1.95(So2) + 14.6, index of fit 0.806, n = 27; PPAM (side) = -0.002(So2)2 - 0.16(So=) + 60.1, index of fit 0.432, n = 48.
d u r i n g t h e c o u r s e of t h e e x p e r i m e n t s . T h u s t h e c o r r e l a t i o n s for t h e p u l m o n a r y a r t e r i a l p r e s s u r e i n t h e s t a t i s t i c a l c a l c u l a t i o n s a p p l y to t h e w h o l e m a t e r i a l w i t h o u t i d e n t i f y i n g t h e p r i m a r y c a u s e of t h e p r e s s u r e i n c r e a s e : t h e n u m b e r of a n i m a l s i n v o l v e d is i n d i c a t e d i n t h e r e s p e c t i v e f i g u r e s . T h e c o m b i n e d s e r i e s i n c l u d e d five c a s e s w i t h l o w h e a r t r a t e (_< 60 b / r a i n ) a n d normal oxygen saturations associated with mildly elevated pulmonary a r t e r i a l p r e s s u r e ( s y s t o l i c p r e s s u r e u p to 44 m m H g ) . T h e h e a r t r a t e a n d p u l m o n a r y a r t e r i a l s y s t o l i c a n d m e a n p r e s s u r e s r o s e as a r e s u l t of r e d u c e d a o r t i c b l o o d o x y g e n s a t u r a t i o n (fig. 2) i n d e p e n d e n t l y of t h e c a u s e of t h i s reduction. The initial heart r a t e a n d p u l m o n a r y arterial pressure levels were higher in the animals placed on their side than in those in prone position. At low oxygen saturations the heart rate was equal in both positions, but the pulmonary arterial pressure rose more in the prone position. I n f i g u r e 3 p u l m o n a r y a r t e r i a l s y s t o l i c p r e s s u r e is p l o t t e d a g a i n s t pulmonary arterial blood oxygen saturation. Pulmonary arterial pressure w a s h i g h e r i n i t i a l l y i n t h e a n i m a l s l y i n g o n t h e i r side, a n d t h e n r o s e as t h e p u l m o n a r y a r t e r i a l o x y g e n s a t u r a t i o n d e c r e a s e d , t h o u g h i n a less p r o n o u n c e d m a n n e r w h e n t h e a n i m a l w a s k e p t o n its side.
T i m i s j ~ v i and Hirvonen, Pulmonary circulation in the reindeer
501
o~ lO0
1"
E E LI.I rr' r I1.1 ~r
a.
50
N 0
I
I
f
I
I
40
50
60
70
80
OXYGEN SATURATION %
F i g . 3. P u l m o n a r y arterial s y s t o l i c p r e s s u r e a s a f u n c t i o n o f p u l m o n a r y a r t e r i a l blood oxygen saturation. Solid line indicates prone position and dotted line, side p o s i t i o n . E q u a t i o n s f o r t h e c u r v e s : PPAS ( p r o n e ) = - 0 . 0 1 9 ( S o 2 ) 2 + 0.75(So2) + 72.2, i n d e x o f fit 0.786, n = 40; PPAS ( s i d e ) = - 0 . 0 1 4 ( S o 2 ) 2 + 0.71(So2) + 56.5, i n d e x o f f i t 0.413, n = 80.
P u l m o n a r y arterial p r e s s u r e rose as h e a r t rate increased (fig. 4), w h e r e a s cardiac o u t p u t increased as a f u n c t i o n of heart rate (fig. 4) a n d of b l o o d o x y g e n d e s a t u r a t i o n (fig. 5). P u l m o n a r y arterial p r e s s u r e rose w i t h the increase in cardiac o u t p u t (figs. 4 a n d 5) in the animals in p r o n e position, b u t this correlation was n o t significant in animals lying on their side. U n d e r the c o n d i t i o n s stated here an increased p u l m o n a r y v a s c u l a r resistance was calculated w h e n p u l m o n a r y arterial p r e s s u r e was i n c r e a s e d .~
~.
CO
=~3oo
W
. . . co
.S
;oo~ 200.
0.
..." ..I
0
PPAS PPAS
Department of Physiology, University of Ou]u, Oulu (Finland)
P u l m o n a r y c i r c u l a t i o n in the r e i n d e e r P u l m o n a l k r e i s l a u f b e i m Rentier J. T i m i s j ~ r v i
and L. H i r v o n e n
With 6 figures and 1 table (Received J a n u a r y 24, 1978) Summary Right heart catheterizations were performed in 56 sessions on 25 reindeer with determinations of blood pressure and oxygen saturation. Cardiac output was calculated from cineangiocardiograms. When the animals were placed in prone position, heart rate was about 50/rain, m i x e d venous blood oxygen saturation 68 to 72%, right ventricular systolic pressure 27 mmHg, p u l m o n a r y arterial pressure 25/18/11 mmHg, p u l m o n a r y arterial wedge pressure 6-8 m m H g and p u l m o n a r y transfer time 4 to 5 cardiac cycles. When the animals were placed on their side, the heart rate rose to 90 b/rain, mixed venous blood oxygen saturation decreased by about 4% and the right ventricular and p u l m o n a r y arterial pressures increased by about 10 m m H g ; p u l m o n a r y arterial wedge pressure did not change. Hypoxemia led to an increase in heart rate, cardiac output and pulmonary arterial pressure; the latter two measures tended to increase whenever the heart rate increased. U n d e r the conditions stated here, an increased p u l m o n a r y vascular resistance was calculated w h e n p u l m o n a r y arterial pressure was increased. T h e r e i n d e e r is a r u m i n a n t i n d i g e n o u s to t u n d r a a n d t a i g a a r e a s s h o w i n g a h i g h l e v e l of a d a p t a t i o n to t h e s e c o n d i t i o n s . O l d e r s t o c k s of r e i n d e e r w e r e o n c e s u b j e c t e d to a n n u a l m i g r a t i o n s ; t h e s e a r e o n l y of v e r y l i m i t e d e x t e n t n o w a d a y s w i t h t h e a d a p t i o n of a n o r g a n i z e d h e r d i n g s y s t e m . T h e r e i n d e e r is n e v e r t h e l e s s e x p o s e d to t h e d e m a n d s of p h y s i c a l a c t i v i t y , for i n s t a n c e i n p u l l i n g s l e d g e s a n d for c a r r y i n g l o a d s , a n d t h e s u r v i v a l of e a c h a n i m a l d e p e n d s to a g r e a t e x t e n t o n its a b i l i t y to d i g for l i c h e n u n d e r t h e snow in winter. T h e v o l u m e s a n d f u n c t i o n i n g of t h e r e i n d e e r h e a r t r e a c t r a p i d l y to v a r i o u s s t i m u l i a n d m a r k e d p o s t u r a l c h a n g e s (1). T h e h e i g h t e n e d p u l m o n a r y v a s c u l a r r e a c t i v i t y of b o v i n e s p e c i e s to v a r i o u s i n t e r v e n t i o n s s u c h as h y p o x i a a n d e n d o t o x i n h a s b e e n r e c o g n i z e d e a r l i e r (2, 3), a n d s p o n t a n e o u s p u l m o n a r y h y p e r t e n s i o n h a s b e e n n o t e d i n b o v i n e c a l v e s (4). T h e p r e s e n t work concerns the pulmonary circulation in the reindeer, especially during hypoxia.
Material and m e t h o d s Right heart catheterization was performed through the jugular vein in fifty-six sessions on twenty-five reindeer (Rangifer tarandus tarandus L.) five to eighteen m o n t h s of age and ranging in weight from 19 to 44 kg. The right atrial, ventricular, and p u l m o n a r y arterial pressures were recorded with a Statham pressure trans759
498
Basic Research in Cardiology, Vol. 73, No. 5 (1978)
d u c e r (Type 53210~ P 37), a n e l e c t r o m a n o m e t e r a n d a M i n g o g r a p h 34 jet r e c o r d e r (Elema-SchSnander, Stockholm). Blood oxygen saturations were measured with an O x i m e t e r - D e n s i t i o m e t e r ( T y p e 351, N o 140, A / S N y c o t r o n , Oslo). C i n e a n g i o c a r d i o g r a m s w e r e r e c o r d e d in r i g h t l a t e r a l p r o j e c t i o n w i t h a n i n e - i n c h Siemens image intensifier and an Arriflex camera (Siemens Aktiengesellschaft, E r l a n g e n ) a t a s p e e d of 30 f r a m e s p e r s e c o n d . U r o g r a f i n | 76% ( S c h e r i n g - L e i r a s , T u r k u ) , 1 rnl p e r k g b.w. dose, w a s u s e d as t h e c o n t r a s t m e d i u m ; a n d t h e a n i m a l w a s p l a c e d e i t h e r o n its s i d e or in p r o n e p o s i t i o n d u r i n g f i l m i n g . T h e s t r o k e v o l u m e for c a r d i a c o u t p u t d e t e r m i n a t i o n w a s c a l c u l a t e d f r o m t h e c i n e a n g i o c a r d i o g r a m s b y a g e o m e t r i c m e t h o d p u b l i s h e d p r e v i o u s l y (5). T h e p u l m o nary circulation time was estimated from the time difference between visualization of t h e p u l m o n a r y a r t e r y to t h e v i s u a l i z a t i o n of t h e left a t r i u m . L i d o c a i n w a s u s e d as a local a n a e s t h e t i c . S e d a t i o n w a s i n d u c e d u s i n g 1.2 to 1.5 m g d i a z e p a m p e r k g b.w. i n t r a v e n o u s l y . D e e p e r a n a e s t h e s i a w a s i n d u c e d w i t h 5 to 20 m g p e n t o b a r b i t a l s o d i u m p e r k g of b.w. E n d o t r a c h e a l i n t u b a t i o n or t r a c h e ostomy with positive pressure ventilation were used during pentobarbital anaest h e s i a if b r e a t h i n g i r r e g u l a r i t i e s o c c u r r e d . H y p o x i a w a s i n d u c e d b y m e a n s of a 10% m i x t u r e of o x y g e n i n n i t r o g e n o r b y i m p a i r m e n t of r e s p i r a t i o n u n d e r p e n t o b a r b i t a l sodium.
Results Anatomy of the reindeer right ventricle The thickness of the right ventricular free wall of five autopsied animals with a heart weight of 350 to 400 g ranged from 3 mm at the intervent r i c u l a r s u l c u s t o 12 m m a t t h e s i t e o f t h e p a p i l l a r y m u s c l e . T h e m i d p o r t i o n o f t h e w a l l n e a r t h e p a p i l l a r y m u s c l e w a s 9 t o 10 m m t h i c k . D u r i n g e j e c t i o n
Fig. 1. A n g i o c a r d i o g r a m of a 5 - m o n t h - o l d r e i n d e e r i n l a t e r a l p r o j e c t i o n . C o n t r a s t m e d i u m w a s i n j e c t e d i n t o t h e r i g h t a t r i u m . A: r i g h t v e n t r i c l e i n diastole. B: r i g h t v e n t r i c l e i n systole. P u l m o n a r y a r t e r i e s are v i s i b l e i n t h e u p p e r p a r t s of t h e p i c t u r e s .
Timisj~rvl and Hirvonen, Pulmonary circulation in the reindeer
499
Table 1. Pressure values for the pulmonary circulation in the reindeer under various conditions (mm Hg). Condition
Control
n
18
P u l m o n a r y arterial pressure Right Right atrial ventricular systohc diastolic m e a n pressure pressure
wedge
2- 6
6-8
P u l m o n a r y hypertension: Uncontrolled 25 2-10 Hypoxic 20 4-15
22-27
20-27
10-12
16
up to 60 up to 150
up to 60 up to 35 up to 42 up to 150 up to 90 up to 110
6-8 up to 20
a l l t h e d i m e n s i o n s of t h e r i g h t v e n t r i c u l a r c a v i t y d e c r e a s e d a n d t h e f r e e c h a m b e r w a l l t h i c k e n e d (fig. 1). P a r a m e t e r s o f t h e p u l m o n a r y circulation u n d e r c o n t r o l c o n d i t i o n s The various pressures recorded under control conditions are given in T a b l e 1. T h e m e a n p u l m o n a r y c i r c u l a t i o n t r a n s f e r t i m e w i t h r e g u l a r c a r d i a c r h y t h m w a s f o u r t o f i v e c a r d i a c c y c l e s (in f i f t e e n a n i m a l s ) c o r r e s p o n d i n g t o f i v e s e c o n d s a t a h e a r t r a t e of 50 t o 60 b / r a i n . T h e o x y g e n s a t u r a t i o n of p u l m o n a r y a r t e r i a l b l o o d ( m i x e d v e n o u s b l o o d ) w a s 68 to 72% in f i f t e e n successive experiments on eight animals in prone position; the corres p o n d i n g v a l u e s w h e n t h e a n i m a l s w e r e p l a c e d o n t h e i r s i d e w e r e 64 to 68 per cent. P u l m o n a r y arterial h y p e r t e n s i o n Pulmonary arterial pressure in the reindeer was labile. It could be increased during controlled procedures, but would also increase in an u n c o n t r o l l e d m a n n e r ( T a b l e 1). A g r a d u a l i n c r e a s e in p r e s s u r e w a s o b s e r v e d w i t h i n h a l f a n h o u r of t h e i n t r o d u c t i o n of t h e c a r d i a c c a t h e t e r i n animals under mild sedation without any other measures. The pressure i n c r e a s e s t a r t e d 5 t o 10 m i n u t e s e a r l i e r a n d w a s m o r e p r o n o u n c e d in t h e a n i m a l s k e p t o n t h e i r s i d e . H o l d i n g of b r e a t h , t h e V a l s a l v a e f f e c t , a n d s o m e t i m e s a l s o r u m i n a t i o n w e r e o b s e r v e d a t t h e i n i t i a l s t a g e of t h i s p r e s s u r e r i s e . A s p o n t a n o u s d e c l i n e i n p r e s s u r e to a r o u n d t h e i n i t i a l l e v e l o c c u r r e d w i t h i n 30 t o 120 m i n u t e s . A o r t i c a n d m i x e d v e n o u s b l o o d o x y g e n saturations were reduced during the hypertensive period. Pentobarbital sodium administration was rapidly foUowed by respiratory irregularities ranging from periodic ventilation to apnea, by reduced arterial oxygen saturation and by pulmonary hypertension. Other effects n o t e d w e r e i n c r e a s e d s a l i v a t i o n , b l o a t i n g of t h e a b d o m e n a n d r e g u r g i t a t i o n of t h e r u m e n c o n t e n t s l e a d i n g to a n e c e s s i t y f o r e n d o t r a c h e a l i n t u b a tion. H y p o x i a i n d u c e d b y a n a t m o s p h e r e of 10% o x y g e n in n i t r o g e n c a u s e d the heart rate, right atrial and ventricular and pulmonary arterial pressures t o r i s e ( T a b l e 1). T h e s e t h r e e t y p e s of p r e s s u r e r i s e : u n c o n t r o l l e d , i n d u c e d b y p e n t o b a r bital and induced by anoxic hypoxia, caused parallel changes in the pulmonary circulation and could not be distinguished from one another
Baslc Research in Cardiology, Vol. 73, No. 5 (1978)
500
._c 200 . E
o~ -1-
E E
_(3 ILl F"" rr t--
n-
150-
< -r 100
10(
HR 50 PPAS
PPAs PPAM PPAM
50-
Z 0
HR N
I
70
I
I
p
80 90 100 AORTIC OXYGEN SATURATION %
Fig. 2. Heart rate (HR), p u l m o n a r y arterial systolic (PPAs) and m e a n (PPAM)pressures plotted against aortic blood oxygen saturation (So2). Solid lines indicate prone position and dotted lines side position. Equations for the curves: HR (prone) = -0.146(So~) 2 + 20.2(So~) - 518, index of fit 0.780, n = 16; HR (side) = -0.044(So2)2 + 4.2(So~) + 104, index of fit 0.600, n = 32; PPAS (prone) = -0.039(So~)2 + 5.1(So2) - 92.2, index of fit 0.815, n = 27; PPAS (side) = 0.0007(Soz)2 - 0.67(So~) + 99.6, index of fit 0.411, n = 48; PPAM (prone) = -0.019(So~)2 + 1.95(So2) + 14.6, index of fit 0.806, n = 27; PPAM (side) = -0.002(So2)2 - 0.16(So=) + 60.1, index of fit 0.432, n = 48.
d u r i n g t h e c o u r s e of t h e e x p e r i m e n t s . T h u s t h e c o r r e l a t i o n s for t h e p u l m o n a r y a r t e r i a l p r e s s u r e i n t h e s t a t i s t i c a l c a l c u l a t i o n s a p p l y to t h e w h o l e m a t e r i a l w i t h o u t i d e n t i f y i n g t h e p r i m a r y c a u s e of t h e p r e s s u r e i n c r e a s e : t h e n u m b e r of a n i m a l s i n v o l v e d is i n d i c a t e d i n t h e r e s p e c t i v e f i g u r e s . T h e c o m b i n e d s e r i e s i n c l u d e d five c a s e s w i t h l o w h e a r t r a t e (_< 60 b / r a i n ) a n d normal oxygen saturations associated with mildly elevated pulmonary a r t e r i a l p r e s s u r e ( s y s t o l i c p r e s s u r e u p to 44 m m H g ) . T h e h e a r t r a t e a n d p u l m o n a r y a r t e r i a l s y s t o l i c a n d m e a n p r e s s u r e s r o s e as a r e s u l t of r e d u c e d a o r t i c b l o o d o x y g e n s a t u r a t i o n (fig. 2) i n d e p e n d e n t l y of t h e c a u s e of t h i s reduction. The initial heart r a t e a n d p u l m o n a r y arterial pressure levels were higher in the animals placed on their side than in those in prone position. At low oxygen saturations the heart rate was equal in both positions, but the pulmonary arterial pressure rose more in the prone position. I n f i g u r e 3 p u l m o n a r y a r t e r i a l s y s t o l i c p r e s s u r e is p l o t t e d a g a i n s t pulmonary arterial blood oxygen saturation. Pulmonary arterial pressure w a s h i g h e r i n i t i a l l y i n t h e a n i m a l s l y i n g o n t h e i r side, a n d t h e n r o s e as t h e p u l m o n a r y a r t e r i a l o x y g e n s a t u r a t i o n d e c r e a s e d , t h o u g h i n a less p r o n o u n c e d m a n n e r w h e n t h e a n i m a l w a s k e p t o n its side.
T i m i s j ~ v i and Hirvonen, Pulmonary circulation in the reindeer
501
o~ lO0
1"
E E LI.I rr' r I1.1 ~r
a.
50
N 0
I
I
f
I
I
40
50
60
70
80
OXYGEN SATURATION %
F i g . 3. P u l m o n a r y arterial s y s t o l i c p r e s s u r e a s a f u n c t i o n o f p u l m o n a r y a r t e r i a l blood oxygen saturation. Solid line indicates prone position and dotted line, side p o s i t i o n . E q u a t i o n s f o r t h e c u r v e s : PPAS ( p r o n e ) = - 0 . 0 1 9 ( S o 2 ) 2 + 0.75(So2) + 72.2, i n d e x o f fit 0.786, n = 40; PPAS ( s i d e ) = - 0 . 0 1 4 ( S o 2 ) 2 + 0.71(So2) + 56.5, i n d e x o f f i t 0.413, n = 80.
P u l m o n a r y arterial p r e s s u r e rose as h e a r t rate increased (fig. 4), w h e r e a s cardiac o u t p u t increased as a f u n c t i o n of heart rate (fig. 4) a n d of b l o o d o x y g e n d e s a t u r a t i o n (fig. 5). P u l m o n a r y arterial p r e s s u r e rose w i t h the increase in cardiac o u t p u t (figs. 4 a n d 5) in the animals in p r o n e position, b u t this correlation was n o t significant in animals lying on their side. U n d e r the c o n d i t i o n s stated here an increased p u l m o n a r y v a s c u l a r resistance was calculated w h e n p u l m o n a r y arterial p r e s s u r e was i n c r e a s e d .~
~.
CO
=~3oo
W
. . . co
.S
;oo~ 200.
0.
..." ..I
0
PPAS PPAS
