Continuousrecording of pulmonary artery pressure in unrestricted … · standard readily available Medilog miniaturised tape recorder with a four channel facility for multiple recordings

Br HeartJ 1984; 51: 421-6

Continuous recording of pulmonary artery pressure inunrestricted subjectsHAMID IKRAM, A M RICHARDS, E J HAMILTON, M GARY NICHOLLS

From the Department of Cardiology, The Princess Margaret Hospital, Christchurch, New Zealand

SUMMARY Continuous ambulatory pulmonary artery pressures were recorded using a conventionalNo 5 French Goodale-Lubin fluid filled catheter linked to the Oxford Medilog system of a portabletransducer-perfusion unit and miniaturised recorder. Data retrieval and analysis were performedusing a PB2 Medilog playback unit linked to a PDP 11 computer system. The total system has a

frequency response linear to 8 Hz allowing accurate pressure recording over the full range of heartrates. Ten recordings in 10 patients yielded artefact free data for 80% or more of the recordedperiod. This inexpensive reliable method allows pulmonary artery pressures to be recorded inunrestricted subjects.

The diagnosis of pulmonary hypertension, primary orsecondary, requires the accurate measurement ofpulmonary artery pressure. Despite occasional reportsof non-invasive methods' reliable assessment of pul-monary pressure still requires cardiac catheterisation.

Initially, right heart catheterisation was confined tothe diagnostic laboratory, where recordings are gener-ally limited to a period of minutes only.2 Cathetermodifications by Bradley,3 Fife and Lee,4 and Swan etalS made it possible for pulmonary artery pressurerecordings to be performed safely at the bedside overmoderately long periods of time. Nevertheless, therecording equipment is bulky, and this, together withthe unknown hazards of ambulatory pulmonarycatheterisation, have restricted the use of this techni-que to severely ill patients confined to bed.67 Hencevariations in pulmonary artery pressures due to nor-mal physiological influences are largely unknown.This is true both in health and in disease. Theresponse of primary pulmonary hypertension to vari-ous vasodilator agents has been of particular interestrecently.8-0 Nevertheless, the absence of reliableinformation on the range of spontaneous variability inthis and other forms of pulmonary hypertension seri-ously limits the evaluation of therapeutic interven-tions. "I A method for prolonged recording of pulmo-nary artery pressure in unrestricted subjects is thusrequired.

Requests for reprints to Dr A M Richards, Department of Endo-crinology, The Princess Margaret Hospital, Christchurch 2, NewZealand.

Accepted for publication 1 November 1983

The only report of continuous ambulatory pulmo-nary pressure monitoring is by Nathan et al. 1 2 Theseworkers used a specially developed solid state catheterand recording system. We report our experience usinga conventional fluid filled catheter and a standardrecording system for measuring pulmonary arterypressure in unrestricted subjects.

Patients and methods

Ten patients (nine men and one woman) undergoingdiagnostic cardiac catheterisation, including rightheart studies, gave consent to additional ambulatoryrecordings of pulmonary artery pressure. The studyprotocol was approved by the hospital ethical commit-tee. The Table shows the clinical details together withmaximum and minimum recorded pulmonary systolicand diastolic pressures.

EQUIPMENTCatheterPulmonary arterial catheterisation was performed viaa right antecubital percutaneous entry in five patientsand via a right subclavian venous entry in five underlocal anaesthesia with plain 1% xylocaine. A No 5French Goodale-Lubin catheter was inserted and itstip positioned in the main pulmonary artery underfluoroscopic guidance. Wheni venous access at theantecubital or subclavian site had been achieved abolus of 4000 units of heparin was given through thecatheter. Its position was checked for stability duringcoughing and deep breathing. The catheter was firmlyfixed at its entry site with a suture and an adhesiveskin dressing.

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Table Pulmonary arterial pressures (mm Hg)

Case Age Diagnosis NYHA Pulnonanyaer pre Duration ofNo y) fmcional recoring

class Systolic Diastolic (h)

Max Min Max Min

1 49 CAD III 62 27 28 8 242 70 MI III 50 20 20 5 203 57 CAD II 28 15 7 1 214 61 AI II 36 22 21 4 225 55 CAD III 37 16 17 2 106 62 CAD II 35 10 17 3 107 48 MS II 88 32 55 20 258 70 MI III 75 50 38 17 109 53 AS II 45 17 25 4 1110 71 AI III 92 53 60 32 10

CAD, coronary artery diseaae; MI, mitral incompetence; AI, aordc incompetence; MS, mitral stenosis; AS, aortic stenosis; max,mmm; mM, minimum.

Initial experiments using single end hole catheterssuch as a No 5 French Cournand or Swan-Ganz cathe-ter gave consistently poor recordings because of repe-ated impaction of the single catheter orifice against thevessel wail. A No 6 French NIH catheter with six sideholes was then used to ensure a free passage between

the lumens of the pulmonary artery and catheter forthe transmission of a pressure pulse; however, clot-ting of the small side holes occurred in four of 12preliminary cases studied using this catheter. All 10cases reported below were studied using a No 5French Goodale-Lubin catheter with two side holes

Fig. 1 Pulmonay artesy presse recording system using (1) a No 5 French GoodaleuLubin catheter, (2) comection tubing, (3) atransducererfmion un, (4) a connecton plug, (5) a Medilog m itned tape recorder, and (6) ECG leads.

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Ambulatory pulmonary artery pressure recording0

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Fig. 2 Frequency response of the pulmonary artery pressurerecording and playback system.

and an end hole.

Transducer-perfusion unit and recorderThe catheter was connected to the transducer-perfusion unit with 80 cm of non-distensible tubing(internal diameter 0-6 mm). The 100 g unit consists ofa semiconductor strain gauge and a delta pump casttogether in an epoxy casting, which also contains a 40ml capacity reservoir for heparinised saline. The fluidchannel interconnections are integrally moulded inthe casting and include a three way tap for calibratingthe transducer while in use or for flushing the catheterwhen necessary. Anticoagulation was provided by asolution of 8000 IU of heparin in 40 ml of 0.90/o salinefor irrigating the catheter at a rate of 3-4 ml/h. Thisequipment is of proven reliability and its use incontinuous systemic arterial pressure recording isreported elsewhere.13 14 To maintain the patency ofthe catheter the unit pump speed was reset to give therate of irrigation mentioned above. This was approx-imately double the rate used with systemic arterialirrigation. The transducer was carried at chest heightwith the semiconductor strain gauge positioned underfluoroscopic guidance over the tip of the catheter inthe pulmonary artery. The transducer signal wasrecorded together with the electrocardiogram fromchest leads on a multichannel miniaturised Medilogtape recorder worn on a belt at waist level. The totalweight of the equipment was 900 g. Fig. 1 showscomponents of the system. At least two calibrationsusing a mercury column were made during each studyusually near the beginning and end of the recording.A simple protocol, which included periods of lying

supine and standing and mild symptom limited exer-cise climbing several ffights of stairs, was completedby each patient.

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Data retnieval and analysisData retrieval and analyses were performed by a PB2Medilog playback deck coupled with a PDP1 1 com-puter system which provided graphical and digitalprintouts of systolic, diastolic, and mean pulmonaryartery pressures and heart rate, all averaged over 10beat samples. The facility for beat by beat analysis isavailable. The time required from the start of tapeplayback to printout of data was about 30 minutes.

Results

Patient tolerance of the ambulatory recording proce-dure was excellent. All patients were able to sleepsatisfactorily with the equipment in place. Recordingsranged in duration from 10 to 25 hours. No complica-tions occurred either in this group of 10 patients or inany of the 20 patients in whom preliminary studieshad been performed using other catheters.On playback, mercury column calibrations

matched perfectly on all tapes indicating negligiblebaseline drift. The frequency response of the wholesystem-that is, from catheter tip to the output of theMedilog playback amplifier-was laboratory tested ina-similar way to that described by Goldberg et al.'5Fig. 2 shows the system response. Two resonancesoccurred, one at 16 Hz and one at 60 Hz, which canbe attributed to the narrow extension tubing and theNIH catheter respectively.The Medilog playback amplifier and the Medilog

recorder amplifier both showed a frequency responsedropoff at 8 Hz, which limits the capability of thewhole system to record high frequency waveforms.The fifth harmonic of a pressure waveform associatedwith a heart rate of 100 beats/min can still be recordedunder such circumstances.The fluid filled catheter system was compared in

situ with a high fidelity transducer tipped Millarcatheter during catheterisation. Fig. 3 shows recordedwaveforms. The fluid filled catheter response was notdamped thus allowing direct comparison with record-ings from the Millar catheter. From Fig. 3 it is clearthat the pressure waveforms matched each other.With the filtering given by the recording and playbackamplifiers, the fluid filled catheter system gave a"clean" waveform (Fig. 4).The transducer was placed on the anterior chest

wall approximately 5 cm away from the tip of thecatheter. This caused a change in the zero referencepressure of about 4 mm Hg if the patient changedfrom lying to standing.

All 10 studies yielded artefact free data for 800/o ormore of the recording time. Substandard recordingswere due to repeated clotting of the catheter tip anddamping of the pressure wave because of kinking ofthe catheter or extension tubing or both. Clear trac-



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Fig. 3 Comparison ofpulmonaryartery pressure waveforms obtainedwith an undampedfluidfilled catheter(7) and a Millar* catheter.

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ings of pulmonary artery pressure during exercise nary arterieswere obtained. In four patients symptoms occurred pressure (17iduring exercise including dyspnoea, chest tightness, gradient ofand threatened syncope. In each case symptoms coin- stenosis. Thcided with the peak pulmonary artery pressure. Sys- monary artetolic pressures recorded ranged from 10 to 92 mm Hg with dyspnand diastolic pressures from 1 to 60 mm Hg. Two patient had Icases are reported in more detail to illustrate the type Both paticof information made accessible by the technique. levels of ex(

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UTSk 48 year old woman with known mitralsented with a six month history of pro-rtness of breath on exertion. At righterisation a pulmonary artery pressure ofIg was recorded. Over a 24 hour period,nbulatory recording showed pressures as!0 mm Hg at rest. With exercise, sheptomatic with mild dyspnoea and chestinciding with a maximum recorded pres-5 mm Hg (Fig. 5).resented to his general practitioner withLchest pain. Clinical signs suggested aorticrdiac catheterisation showed normal coro-s and a normal resting pulmonary artery'/4 mm Hg). A resting peak aortic systolic80 mm Hg confirmed severe aortic valvee ambulatory study recorded a peak pul-ry pressure of 45/25 mm Hg coincidingoea and "lightheadedness" after thebriskly climbed three ffights of stairs.ents were asymptomatic at rest and at lowercise. The studies allowed pulmonary

Fig. 5 Pulmonary artery pressureand heart rate at rest and during mildexercise (case 7).

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Ambulatory pulmonary artery pressure recording

artery pressures to be matched with symptoms duringdaily activities.

Discussion

The technique used in this study shows the feasibilityof continuous recording of pulmonary artery pressurein unrestricted subjects. The equipment is readilyavailable and has been widely used in ambulatorystudies of systemic arterial pressure. We used thestandard readily available Medilog miniaturised taperecorder with a four channel facility for multiplerecordings. Our method has a limited frequencyresponse which is, however, adequate for pressurerecording if not for waveform analysis. The problemof clotting of the catheter tip has been avoided byusing multi-holed catheters, moderate doses of hepa-rin, and an increased pump flow. Heparin bondedcatheters, which are commercially available and havebeen successful in reducing pressure wave damping inSwan-Ganz catheters,16 may be used as an alternativeapproach. The problem of zero referencing can beovercome by taking a lateral radiograph and estimat-ing the catheter to transducer distance; this can thenbe used to correct the recorded value if an absolutepressure is needed. The data retrieval system allowsbeat by beat analysis of systolic, mean, and diastolicpressures and heart rate. Our use of a catheter with alumen permits blood sampling for measuring oxygencontent and thereby calculating cardiac output by theFick method. Central injection of an indicatorthrough the catheter allows cardiac output to bemeasured by the Hamilton-Stewart method. Thecatheter is also suitable for high pressure pulmonarycontrast angiography.The only alternative technique of ambulatory pul-

monary artery pressure monitoring is that describedby Nathan et al,'2 who used a solid state transducertipped catheter. Their system had a high frequencyresponse, and the positioning of the transducer in thepulmonary artery eliminated any problem with zeroreferencing. As yet, however, the components of thissystem are scarce, expensive, and fragile and do notallow in vivo calibration.The system used is invasive and hence attended by

potential hazards-for example sepsis or perforationof cardiac structures. The catheters used in our studywere smaller than the Swan-Ganz catheters used forroutine haemodynamic monitoring and less stiff thanmany pacing wires used in endocardial pacing. Mostcomplications reported with long term pulmonaryarterial catheterisation have been due to the impactionof an inflated balloon in a distal branch of the pulmo-nary artery with resulting perforation of the ves-sel.'7 18 The absence of a balloon on the catheter weused is an important safeguard, but great care is

425needed with skin fixation to ensure that the catheterdoes not pass further into the vein. Our experienceand that of Nathan et al'2 suggests that ambulatorypulmonary arterial catheterisation for up to 24 hoursis safe and well tolerated.

Ambulatory recording of pulmonary arterial pres-sure using fluid filled catheters and readily availablecomponents is versatile and practical and can be usedin the investigation of many hitherto unresolvedphysiological, pathophysiological, and therapeuticproblems affecting the pulmonary circulation. Pre-liminary studies indicate that by the addition ofanother transducer perfusion unit connected to abrachial artery cannula pulmonary artery and sys-temic artery pressures may be recorded simultane-ously in unrestricted subjects.

We thank the National Heart Foundation of NewZealand for supporting this study.

References

1 Askenazi J, Koenigsberg DI, Ziegler JH, Lesch M.Echocardiographic estimates of pulmonary artery wedgepressure. N Engl J Med 1981; 305: 1566-8.

2 Cournand A, Ranges HA. Catheterization of the rightauricle in man. Proc Soc Exp Biol Med 1941; 46: 462-6.

3 Bradley RD. Diagnostic right heart catheterisation withminiature catheters in severely ill patients. Lancet 1964;ii: 941-2.

4 Fife WP, Lee BS. Construction and use of self-guidingright heart and pulmonary artery catheter. J Appl Physiol1965; 20: 148-9.

5 Swan HJC, Ganz W, Forrester J, Marcus H, DiamondG, Chonette D. Catheterization of the heart in man withuse of a flow-directed, balloon-tipped catheter. N Engl JMed 1970; 283: 447-51.

6 Archer G, Cobb LA. Long term pulmonary artery pres-sure monitoring in the management of the critically ill.Ann Surg 1974; 180: 747-52.

7 Moser KM, Spragg RG. Use of the balloon-tipped pul-monary artery catheter in pulmonary disease. Ann IntemMed 1983; 98: 53-8.

8 Camerini F, Alberti E, Klugmann S, Salvi A. Primarypulmonary hypertension: effects of nifedipine. Br HeartJ 1980; 44: 352-6.

9 Rubin LJ, Groves BM, Reeves JT, Frosolono M, HandelF, Cato AE. Prostacyclin-induced acute pulmonaryvasodilation in primary pulmonary hypertension. Circu-lation 1982; 66: 334-8.

10 Rubin LJ, Peter RH. Oral hydralazine therapy for prim-ary pulmonary hypertension. N Engi J7 Med 1980; 302:69-73.

11 Rich S, Martinez J, Lam W, Rosen KM. Captopril astreatment for patients with pulmonary hypertension:problem of variability in assessing chronic drug treat-ment. Br HeartJ 1982; 48: 272-7.

12 Nathan AW, Perry SG, Cochrane T, Banim SO, Spurrell



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RAJ, Camm AJ. Ambulatory monitoring of pulmonaryartery pressure: a preliminary clinical evaluation. BrHeartJ 1983; 49: 33-7.

13 Millar-Craig MW, Hawes D, Whittington J. New systemfor recording ambulatory blood pressure in man. MedBiol Eng Comput 1978; 16: 727-31.

14 Mann S, Millar-Craig MW, Balasubramanian V, Cash-man PMM, Raftery EB. Ambulant blood pressure:reproducibility and the assessment of interventions. ClinSci 1980; 59: 497-500.

15 Goldberg AD, Raftery EB, Green HL. The Oxford con-tinuous blood-pressure recorder: technical and clinical

Ikram, Richards, Hamilton, Nichollsevaluation. Postgrad Med J 1976; 52 (suppl 7): 104-9.

16 Hoar PF, Wilson RM, Mangano DT, Avery GJ, Szar-nicki RJ, Hill JD. Heparin bonding reduces throm-bogenicity of pulmonary-artery catheters. N Engl J Med1981; 305: 993-5.

17 Foote GA, Schabel SI. Pulmonary complications of theflow-directed balloon-tipped catheter. N Engl J Med1974; 290: 927-31.

18 Sise MJ, Hollingsworth P, Brimm JE, Peters RM, Vir-gilio RW, Shackford SR. Complications of the flow-directed pulmonary artery catheter: a prospectiveanalysis in 219 patients. Crit Care Med 1981; 9: 315-8.



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Continuousrecording of pulmonary artery pressure in unrestricted … · standard readily available Medilog miniaturised tape recorder with a four channel facility for multiple recordings