Anesthesiology
`61:339—341. 1984
`
`CLINICAL REI’OR’I‘S
`
`339
`
`Differences in Pulmonary Artery Wedge Pressmes Obtained
`by Balloon Inflation versus Impactlon Techniques
`
`ROGER L. ROYSTER, M.D.,* _]. CARSON JOHNSON, M.D.,T DONALD S. PROUGH. M.D.,:]:
`WILLIAM E. JOHNSTON, M.D.,i WILSON C. BEAMER, M.D.§
`
`Pulmonary artery wedge pressures (PAWPs) first were
`obtained by advancing non-balloon-tipped catheters under
`fluoroscopic guidance into an ”impacted wedge" (1W)
`position and more recently by advancing How-directed.
`balloon-tipped catheters into a balloon wedge (BW) po-
`sition. Deflated balloon-tipped catheters may migrate into
`an 1W position. which promptly should be recognized
`and the catheter repositioned until a pulmonary artery
`tracing is seen and a BW pressure once again can be
`obtained. We noticed in two patients, one with catheter
`migration and the other after cardiac catheterization. a
`difference between IW and BW pressures and wave forms.
`These observations prompted a prospective clinical study
`to characterize more clearly these differences.
`
`REPORT OF CASES
`
`Purim! l: A 65-year-old man with fever. bilateral pulmonary infil—
`trates. cardiac murmur, and suspected infective endocarditis of the
`initial valve was admitted to the ICU. A 7 French balloon-tipped flow-
`directed pulmonary artery catheter was passed into a 13W position,
`documenting a mean pressure of l2 mntHg and A and V wave aln-
`plitudes above the diastolic baseline of 2 and 4 mmHg. respectively.
`Because respiratory insufficiency progressed. his trachea was intubated.
`and he was ventilated with intermittent mandatory ventilation and
`positive end expiratory pressure. The pulmonary artery catheter was
`removed. since hemodynamic compromise had not been documented.
`The patient improved rapidly. but attempts to wean him front the
`ventilator resulted in severe hypoxemia. A pulmonary artery catheter
`again was inserted, and similar BW pressures were obtained.
`Because the patient appeared to have clinically significant mitral
`regurgitation. cardiac catheterization was performed. The right heart
`chambers were catheterimd with a No. 7 Lehman (non-bolloon-tipped)
`catheter and pressures were recorded. A mean IW pressure of 24
`mmHg. a post-A-wave pressure of 13 mmHg. and a peak V-wave
`amplitude of 44 mini-lg were demonstrated. A left ventriculogram
`confirmed significant rnitral regurgitation. After the patient had been
`returned to the ICU. a BW pressure tracing still did not demonstrate
`
`* Assistant Professor of Anesthesia. Associate in Cardiology.
`'l‘ ICU Research Fellow.
`.1: Assistant Professor of Anesthesia.
`§ instructor in Anesthesia.
`Received from the Department of Anesthesia. Bowman Gray School
`of Medicine of Wake Forest University. Winston-Salem. North Carolina
`27l03. Accepted for publication February 14. 1984. Presented in
`part at the Ninth Annual GulUAtlantic Anesthesia Residents Coti-
`ference. Gainesville. Florida. May IQBH.
`Address reprint requests to Dr. Royster.
`Key words: Equipment: catheters. {low-directed. Swan-Canal“.
`Monitoring: pulmonary artery wedge pressure.
`
`a large V-wave. so an IW pressure measurement was obtained; the
`tracing was identical to that obtained with the Lehman catheter.
`Patient 2: A 56-year~old Inan had a 7 French pulmonary artery
`catheter inserted for monitoring during an episode of acute respiratory
`Failure. The bedside nursing personnel requested evaluation of the
`position of the catheter because they suspected that the catheter had
`migrated to an IW position. Blood obtained from the distal lumen of
`the catheter had a pH of 7.61. a I’m, of IQ mmHg. and a P0, of 233
`mmHg. while systemic arterial blood had a pH of 7.48. a Pm, of 25
`mmHg. and a PO, of 15] mmHg. A post A-wave pressure was 15
`mmHg. and A and V wave amplitudes were 5 mmHg and 15 mmHg.
`respectively.
`The catheter was withdrawn until a pulmonary artery tracing was
`obtained. Blood obtained from the distal lumen at that time dem-
`
`onstrated a pH of 7.44. :1 P00, of3l mmHg. and a P0, of 28 mini-lg.
`A BW pressure obtained with the catheter in that position demonstrated
`a post A-wave pressure of 17 mmHg. and A and V wave amplitudes
`that both were only 3.5 mmHg.
`
`METHODS
`
`Sixty patients in the ICU who had pulmonary artery
`catheters inserted through a commercially available sterile
`shield qualified for our clinical study, which was approved
`by the Hospital Research Practices Committee. All ma-
`nipulations of the catheter were performed by members
`of the ICU physician staff. Systemic artery pressure and
`pulmonary artery pressure tracings or an electrocardio-
`gram (ECG) and pulmonary artery pressure tracings were
`recorded. The balloon was inflated and a BW wave form
`
`recorded. Then the balloon was deflated, and the catheter
`
`advanced into an IW position identified by the loss of
`the phasic pulmonary artery wave form and the presence
`of obvious A and V waves typical of a wedged wave form.
`Simultaneous arterial pressure or ECG and IW pressures
`again were recorded. The catheter then was withdrawn
`to the point in the pulmonary artery where inflation of
`the balloon with l to 1.5 ml air was necessary to obtain
`a BW pressure.
`All PAWPs were measured at end-expiration and re-
`corded. ‘The catheter transducer system was not flushed
`once the comparison sequence was begun. The wedge
`position was documented by a shift of the peak pressure
`event in the wave form as compared with the peak event
`in the pulmonary artery wave form. The post A wave,
`peak V wave. and mean PAWPs were recorded elec-
`tronically, and difierences between the BW and [W pres-
`sures were analyzed by a paired Student’s t test for sig-
`nificance ofP < 0.05.
`
`339
`
`PRAXAIR 1023
`
`339
`
`

`

`CLINICAL
`
`REI'O R'l'S
`
`Alwstltetinlogr
`V 5]. No 3. Sq! “NH
`
`damped BW and 1W wave forms, which made compar-
`isons impossible. Twelve of the 60 patients demonstrated
`obvious differences in wave form between the two
`
`PAWPs. The 1W tracings demonstrated greater phasic
`changes in A and V wave amplitudes (fig. l)and generally
`had higher pressures then the BW tracings (table 1).
`Among these 12 patients. eight had an 1W V-wave am-
`plitude at least 5 mmHg greater than the BW V-wave
`amplitude (fig. 2). The differences in V-wave amplitude
`and post-A wave pressure obtained in the two catheter
`positions were significant (P < 0.05). The comparison of
`mean PAWPs yielded no statistically significant difierence,
`which partially may be explained by the larger mean BW
`pressure (7 mini-lg) in patient 1.
`
`DISCUSSION
`
`PAWP is an indirect measurement of left ventricular
`
`filling or left ventricular end-diastolic pressure. The ab-
`solute value and the wave form of the wedge pressure
`may be affected by a variety of factors, including the
`location of the catheter tip,l the intravascular volume,
`the natural resonant frequency and damping of the cath-
`eter—transducer system,2 and the compliance of the left
`ventricle, the left atrium, and the pulmonary artery.’5
`Differences in wedge pressure wave forms obtained by
`balloon inflation and impaction techniques are relatively
`common but usually are clinically unimportant. However.
`the additional information obtained by using both tech-
`niques in certain critically ill patients may aid in diagnosis
`and treatment. Although there are recognized limitations
`to basing a definitive diagnosis of mitral regurgitation on
`the presence of V waves on a BW tracing}| failure to
`demonstrate large V waves with bedside pulmonary artery
`catheteriaation in the patient I contributed to the delay
`in diagnosis of mitral regurgitation. Such a delay in the
`diagnosis of an acute hemodynamically compromising
`event may contribute to a fatal outcome.‘1 Additionally,
`Moser and Spragg5 have suggested routine impaction
`wedging during catheter insertion, and Braunwald and
`Gorlinti have shown this to be a safe procedure in a large
`series of patients.
`
`
`
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`
`I. Comparison of wedge pressure antl correlation with elec-
`1" It:.
`trutardioglam. A. Wedge pressure by balloon inllation (BW). B. Wedge
`pressure by catheter impaction (IW). Pressures obtained a liar minutes
`apart.
`
`R E5 U L'l's
`
`In many patients, an 1W pressure was not obtainable
`due to the limitation of catheter length available within
`the sterile shield. In addition. several patients had very
`
`TABLE 1. impaction wants Balloon Wedge Pressure Measurements
`
`V-Wave Amplitude
`IW
`BW
`Mean PAW?
`IW
`BW
`
`
`
`
`
`
`
`Post A-Wave Amplitude
`
`IW
`BW
`
`
`340
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`340
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`

`

`Anesthesiology
`v m. NH 3. Sup Isis-I
`
`35
`
`PeakVWaveInmmHg 5
`aEE8Impactlon
`
`5
`
`25
`20
`15
`10
`Balloon Peak V Wave in mm Hg
`
`30
`
`FIG. 2. Comparison of impaction peak V waves with balloon peak
`V waves. Straight line equals line of identity. which shows that the
`inmaclion peak V waves were higher than balloon peak V waves.
`
`Perhaps the difference in wedge pressure wave forms
`can be explained in part by variations in the diameter of
`the pulmonary artery system at the sites where BW and
`[W pressure are obtained. Bell et at' performed wedge
`pulmonary arteriograms to document the anatomy at the
`site of wedging and showed that the manner of catheter
`impaction in different areas (such as at a bifurcation), in
`dilated vessels, or in tortuous vessels may determine
`whether a phasic tracing or an unsatisfactory tracing is
`obtained. An additional factor may be some damping
`
`CLINICAL REI’OR’I'S
`
`341
`
`characteristic of the inflated or overinflated balloon. The
`
`inflating pattern of the balloon in human cadavers, as
`demonstrated radiographically with contrast media in»
`Hation. varied with whether the balloon was in the mid
`or distal portion of the pulmonary artery? The larger
`cross-sectional area of the pulmonary vasculature distal
`to an'inflated balloon may create a more compliant system
`than the smaller cross-sectional area of vessels distal to a
`
`catheter advanced to an impacted position. The latter,
`less compliant system might produce A and V waves of
`greater amplitude.
`In summary. there appear to be differences (20% of
`our patients) in BW and IW pressures that have not been
`described previously. Impacting the catheter with an un-
`inflated balloon may result in a better tracing ofA and
`V wave forms, thus giving additional information about
`left—sided cardiac events.
`
`REFERENCES
`
`I. Bell ALL Jr. Haynes WFjr. Sltimomura 5, Dallas DP: Influence
`of catheter tip position on pulmonary wedge pressures. Ciro
`Res IU:2l5-—2I9. [962
`2. O'Quin R. Marini_|_|: Pulmonary artery occlusion pressure: Clinical
`physiology. measurement. and intelpreunion. Am Rev Respir
`Dis 128:3I9—32fi. 1983
`Fuchs RM.
`l-leuser RR. Yin FCP, Bt'inker JA: Limitations of
`pulmonary wedge V waves in diagnosing Initral regurgitation.
`Am} Cardiol 49:849-854. 1982
`4. Friedman AW. Stein L: Pitfalls in bedside diagnosis of severe
`acute mitral regurgitation. Chest 78:436-441. [980
`. Moser KM. Spragg RC: Use of the balloon-tipped pulmonary
`artery catheter in pulmonary disease. Ann Intern Med 98:53—
`58, [983
`Hntunwald E. Gol'lin R: Total population studied. procedures
`employed. and incidence of complications. Cooperative Study
`on Cardiac Catlteterivation. Edited by Bnlunwald E. Swan HJC.
`Circulation 37—58(Suppl):8—Ifi. l968
`l-Iardyj-I". Morrissette M, 'l'aillelerj. Vauclair It: l’athophysiology
`of rupture of the pulmonary artery by pulmonary artery bal-
`loon-tipped catheters. Anesth Analg 62:925—930. 1933
`
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`341
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