Cardiovascular Research, 1974, 8, 330-337. Pulsatile flow in pulmonary artery, capillary, and vein in the dog' Downloaded from https://academic.oup.com/cardiovascres/article/8/3/330/298317 by guest on 25 September 2021 WARREN G. GUNTHEROTH, RICHARD GOULD, JOHN BUTLER, and EDWIN KINNEN~ With the technical assistance of Donald Breazeale, George McGough, and John Mendenhall From the Departments of Pediatrics and Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA AUTHORS' SYNoPsis The temporal relationship of flow pulses in the pulmonary artery, capil- laries, and veins was investigated in 10 chronic dog preparations with pulsed ultrasonic flowmeters and a nitrous oxide-body plethysmograph for capillary flow. Implanted pressure transducers in the left atrium provided reference to the conventional atrial pulses: A, C, X-descent, V, and Y-descent. Left atrial contraction produced an A-wave pressure transient followed by retrograde flow up the veins. The C-pressure pulse occasionally produced a minimal trough in the venous flow pattern. Early in ventricular systole, X-descent in left atrial pressure preceded a venous flow pulse of modest amplitude, which began prior to the onset of the pulse of capillary flow. On average, right ventricular ejection was followed in 37 msec by the major flow pulse in the capillaries, which in turn was fol- lowed 68 msec later by the onset of venous flow. This venous flow pulse was simultaneous with a rise in left atrial pressure, the V-wave. With the onset of diastole, the Y-descent in atrial pressure pre- ceded a major venous flow pulse. With accelerated heart rate, separation of the V and Y venous flow pulses was lost, and a monophasic pulse was found. Pulsatile flow patterns in the main pulmonary or to reflect left ventricular dynamics (Morgan artery have been reported for the past decade et al, 1966b), or a combination of both right and from ultrasonic and electromagnetic flow re- left heart activity (Kinnen and Stankus, 1968). cordings (Franklin et al, 1962; Hoffman et al, An analysis of the temporal sequence of the flow 1965; Morgan et al, 1966a). Pulmonary capillary patterns in the pulmonary artery, capillary, and flow is also pulsatile, as has been shown by Lee vein and the downstream pressure pulses in the and Du Bois (1955), with a nitrous oxide-body left atrium would be of considerable assistance in plethysmograph technique (Wasserman et al, resolving the origin of the pulsatile flow pattern 1966). Similarly, pulmonary vein flow is pulsatile, in the pulmonary vein. and the pulse has been regarded as transmitted We have combined the use of pulsed ultrasonic from the pulmonary artery (Morkin et al, 1965) flowmeters, nitrous oxide-body plethysmograph, and implanted pressure transducers, providing Supported by Public Health Service Grants HE 03998. HE 13517. and HE 10289. E.K. was a Special Fellow of the Public Health Service the first simultaneous measurement of pulmonary (HE 48675). artery, capillary and vein flow, and left atrial Reprint requests to: Warren 0.Guntheroth, Department of Pedia- trics (RD-20). University of Washington School of Medicine, Seattle, pressure. We conclude that the forward flow Washington 98195, USA. pulses in the pulmonary vein cannot be ascribed a Present address: Department of Electrical Engineering, University of Rochester, Rochester, New York. entirely to transmitted pulses from the right 331 Flow pulses in pulmonary artery, capillary, and vein heart, but represent a variable interaction between absorption of nitrous oxide was recorded from the vis a tergo and uis a fronte. airflow into the plethysmograph after the lungs had been inflated with an 80% N20:20%O2 mixture. Methods Brief apnoea is induced by hyperventilating just The dogs, weighing 16 to 24 kg, were anaesthetized before the absorption recording. The record of the with pentobarbital (30 mg/kg iv). Respiration was absorption after a similar inflation with air, which supported by a Palmer respirator and a left gives the zero flow level, was subtracted point by thoracotomy was performed under surgical asepsis. point, manually, to obtain the true capillary blood Downloaded from https://academic.oup.com/cardiovascres/article/8/3/330/298317 by guest on 25 September 2021 Light-weight, bivalved flow transducers for a flow. The frequency response of the plethysmo- pulsed ultrasonic flowmeter (Franklin et al, 1959; graphic apparatus is flat to 13 Hz. Zero flow levels Mullins et al, 1962) were placed around the for the ultrasonic flowmeter were obtained by root of the main pulmonary artery and the left temporary cardiac arrest with intravenous actyl- lower lobe pulmonary vein. The flow probes were choline. Calibration was not performed since timing large enough to cause no compression of the of events was our primary concern in this study. artery or vein with the chest open. Silastic cannulae. Records of pulmonary vein flow were used only were inserted through purse-string sutures into the from those animals in the first two or three weeks main pulmonary artery and left atrium in the first after operation to minimize the risk of fibrosis five animals and solid-state pressure transducers causing obstructed pulmonary vein flow. Moreover, were implanted in the last five. the presence of fibrosis, confirmed by necropsy The animals were allowed to recover for one after several weeks, could easily be predicted by week. Records were obtained under light anaes- the diminished and dampened flow signal during thesia using morphine (2 mg/kg im) and pento- the cardiac cycle. The internal diameter of the barbital (15 mg/kg iv). The animal was intubated venous flow probe was 6 mm, which was one third and placed in a dog-sized, whole-body plethys- of the diameter of the probe for the pulmonary mograph of 47.5 1. (Fig. 1). The technique has been artery, and consequently one ninth of the cross- previously described (Cheney et al, 1969); pulsatile sectional area. With identical amplification of the FIG. I Dog plethysmograph. Flow into the box through the flowmeter (3) reflects instantaneous N20 absorption in the pulmonary capillaries from the previously inflated lung, during apnoea. Other flow transients due to gas absorption and the mechanical activity of the heart are recorded afrer an exactly similar air inflation (air bag) and subtracted from the experimental record after inflation with N20(N20 bag). FA= femoral artery catheter, Ppa=pulmonary artery pressure, PLA=left atrial pressure, V =flowmeter in wall of plethysmograph, QPa =pulmonary artery pow, QPV =pulmonary venous flow, Jug vein =jug venous catheter. 332 Guntheroth, Gould, Butler, and Kinnen flow signal for the two vessels, it was possible to (Linderholm et al, 1962). We tested this with our estimate the relationship of flow in the pulmonary apparatus by injecting a small bolus (about 0.5 ml.) vein to the cardiac output (root of the pulmonary of saline into a small pulmonary vein of an acutely artery). Since there are usually five pulmonary veins, prepared dog in the plethysmograph. A very thin a damped flow record would result if the flow in the (0.6 mm ID; 1.5 mm OD) polyethylene catheter was pulmonary vein was substantially reduced below threaded retrogradely up the pulmonary vein from one fifth of the cardiac output. For the actual the left atrium to pierce the wall of a small vein and recording, the amplifier gain for the pulmonary then the lung surface. It was drawn through until a Downloaded from https://academic.oup.com/cardiovascres/article/8/3/330/298317 by guest on 25 September 2021 vein was increased, relative to the pulmonary bell-shaped expansion on its inner end wedged in a artery, for better identification of the component venous bifurcation. The catheter was cut as short pulses. as possible and connected to a thick walled T-tube, The plethysmograph record has been assumed to one limb of which went toa strain gauge manometer lag the capillary flow events by between 5 msec and the other to a 5 ml. syringe. The system was ( Wasserman and Comroe, 1962) and 20 msec filled with saline. Striking the plunger caused a PULMONARY ARTERY FLO\ One SeconL N20 PLETHY LEFT ATRIAL PULMONARY VEIN FLOW $ E LEC TROCAR DyIy"Ytlt 10 GRAM FIG. 2 Photographic recording of simultaneous pulsatile pulmonary flows in an intact chronic animal pre- paration with left atrial pressure and the electrocardiogram. The left atrial pressure was obtained with an implanted, solid-state device. Pulmonary artery and vein flow were recorded with pulsed ultrasonic flowmeters. The pulmonary capillary flow record is that obtained with nitrous oxide, and for quantitative data the curves obtained with air must be subtracted point by point. However, in this animal the upstroke of the major pulse is not afected for purpose of timing, except for the instrumental time lag of 16 msec (roughly three quarters of a division). Component waves of pulmonary vein flow and left atrial pressure are labelled according to con- ventional alphabetic usage. 333 Flow pulses in pulmonary artery, capillary, and vein pressure transient via the T-tube and a flow jet into recorded on photographic paper. In the figures used the small veins and capillaries. In six studies, the here selection was dictated primarily by the clarity resulting transient in the capillary blood flow from of wave form of the pulmonary vein flow. (With the plethysmographic record lagged the pressure primary variables of three flows and three pressures transient an average of 16 msec (range 15.3 to records of one or two of these would occasionally 17.3 msec). This 16-msec delay was used in calcu- be less than optimal.) However, the numerical data lating transit time. on transmission time and the conclusions as to the Although it is not possible to obtain pulmonary relationships of the pressure and flow wave com- Downloaded from https://academic.oup.com/cardiovascres/article/8/3/330/298317 by guest on 25 September 2021 capillary flow records in unanaesthetized dogs, it is ponents rest on analysis of literally thousands of possible to record flows with the ultrasonic flow- feet of analog recordings from all 10 animals.