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Accurate, automated, continuously displayed pulmonary artery pressure measurement
72
ABSTRACTS
oxide. Each dog was monitored with arterial and pulmonary artery catheters, a transcutaneous Ps analyzer, and two pulse oximeters. An IL-282 Co-oximeter was used to periodically measure arterial oxyhemoglobin (0,Hb) and carboxyhemoglobin (COHb) as percentages of the total hemoglobin. The Pa%, Pa-,, and pH, were measured in the same blood specimens using standard electrodes. When the inspired oxygen concentration was reduced in the absence of COHb, the pulse oximeter saturation (SpO,) estimated 0,Hb with reasonable accuracy. COHb levels were than varied slowly from O-75% in each dog. As the COHb level increased and oxyhemoglobin decreased, both pulse oximeters continued to read an oxygen saturation of greater than 90%, while the actual 0,Hb fell below 30%. In the presence of COHb, the SpO, is approximately the sum of COHb and O,Hb, and, thus, may seriously overestimate 0,Hb. The pulse oximeter, as the sole indicator of blood oxygenation, should, therefore, be used with caution in patients with recent carbon monoxide exposure. On the other hand, transcutaneous Po, falls linearly as COHb increases, and reaches about one-fifth of its initial value at the highest COHb levels despite the maintenance of constant arterial PO,. (Reprinted with permission.) Accuracy
of Response
Hypoxia.
Severinghaus
of Six Pulse
JW,
Naifeh,
Oximeters
KH.
to Profound
Anesthesiology
67551, 1987. Oxygen saturation, Sp,%, was recorded during rapidly induced 42.4 + 7.2-s plateaus of profound hypoxia at 40-70% saturation by 1 or 2 pulse oximeters from each of six manufacturers (NE = Nellcor NlOOe, OH = Ohmeda 3700e, NO - Novametrix 500@versions 2.2 and 3.3 (revised instrumentation), CR - Criticare CSI 501+@ version .27 and version .28 in 501 & 502 (revised instrumentation), PC - PhysioControl Lifestat 1600@, and MQ = Marquest/ Minolta PulseOx 78). Usually, one probe of each pair was mounted on the ear, the other on a finger. Semi-recumbent, healthy, normotensive, non-smoking Caucasian or asian volunteers (age range 18-64 yr) performed the test six to seven times each. After insertion of a radial artery catheter, subjects hyperventilated 3% CO,, O-5% O*, balance N,. Saturation Sco,, computed on-line from mass spectrometer end-tidal PO, and P,, was used to manually adjust Fro, breath by breath to obtain a rapid fall to a hypoxic plateau lasting 30-45s, followed by rapid resaturation. Arterial Hb,,% (Radiometer OSM-3”) sampled near the end of the plateau averaged 55.5 + 7.5%. SC,% (from the mass spectrometer) and Sa,% (from pH and P%, by Corning 178@) differed from Hb%% by + 0.2 t 3.6% and 0.4 f 2.8%. respectively. The plateaus were always long enough to permit instruments to demonstrate a plateau with ear probes, but finger probes sometimes failed to provide plateaus in subjects with peripheral vasoconstriction. Nonetheless, Sp,, read significantly too low with finger probes at 55% mean Saol The mean error with ear probes was not significant. Several instruments occasionally defaulted to zero saturation during rapid desaturation. Precision was independent of probe location, but differed widely between instruments. The studies provided data with which manufacturers could improve function, as illustrated by subsequent series with CR and NO.
The authors conclude that square-waves of hypoxia can assess both the transient and the steady-state profound hypoxic responses of pulse oximeters, disclosing a variety of problems, and facilitating their resolution. An addendum follows the article. (Reprinted with permission.) Bedside
Measurement
Patients
With
KE, Hill
RD. et al.
Acute
of Pulmonary Respiratory
Capillary
Failure.
in
Pressure
Collee
GG, Lynch
Anesthesiology 66:614, 1987.
In this report, the authors present the results of 34 estimates of pulmonary capillary pressure (Pcap) in 15 adult patients receiving intensive care for acute respiratory failure (ARF). Within the pulmonary artery pressure profile during transient balloon occlusion, the authors identified two exponential pressure decay components-the slower one representing the discharge of the pulmonary capillary pressure through the pulmonary venous resistance. By extrapolating this exponential to its origin at the moment of pulmonary artery occlusion, a pressure within the pulmonary vascular bed which approximates pulmonary capillary pressure (Pcap) was identified. Pcap and not the pulmonary artery occlusion pressure (PAOP), is the major driving pressure forcing fluid from the pulmonary microvasculature. The results indicate that a discrete value for pulmonary capillary pressure can be reproducibly measured in paralyzed ventilated patients. The data report that mean pulmonary artery pressure, pulmonary capillary pressure, and total pulmonary vascular resistance (PVR) are increased in acute respiratory failure, but there is considerable variation in the distribution of pulmonary vascular resistance between the arterial and venous beds. The data suggest that there in unequal and variable partitioning of the increased PVR during acute respiratory failure. Bedside pressure profile Pcap measurements will allow optimum reduction of Pcap during ARF by infusing vasoactive agents to modify the distribution of PVR or reducing the PAOP. (Reprinted with permission.) Accurate, Automated, Continuously Displayed Artery Pressure Measurement. Mitchell MM,
Jones BR, et al.
Pulmonary
Meathe
EA.
Anesthesiology 671294, 1987.
A computerized signal processing technique that removes low-frequency respiratory variation from pulmonary artery pressure and other central vascular pressure measurements, and produces a waveform devoid of respiratory artifact, has been developed. This technique has been integrated into a portable bedside monitor. The authors tested the technique in critically ill patients, and found that, compared to physician readings of conventional strip charts, it proved to be a very convenient and accurate method of determining pulmonary artery pressures continuously, regardless of ventilation. (Reprinted with permission.) Postoperative Analgesia of Bupivacaine-Adrenaline.
Tokics
L, et al.
With
lntrspleurel
Brismar.
Administration
B,
Pettersson
N,
Acta Anaesthesiol Stand 31:515, 1987.
Twenty-one patients who underwent elective cholecystectomy were studied with regard to the effect of intrapleural administration of bupivacaine-adrenaline solution on postop-
ABSTRACTS
oxide. Each dog was monitored with arterial and pulmonary artery catheters, a transcutaneous Ps analyzer, and two pulse oximeters. An IL-282 Co-oximeter was used to periodically measure arterial oxyhemoglobin (0,Hb) and carboxyhemoglobin (COHb) as percentages of the total hemoglobin. The Pa%, Pa-,, and pH, were measured in the same blood specimens using standard electrodes. When the inspired oxygen concentration was reduced in the absence of COHb, the pulse oximeter saturation (SpO,) estimated 0,Hb with reasonable accuracy. COHb levels were than varied slowly from O-75% in each dog. As the COHb level increased and oxyhemoglobin decreased, both pulse oximeters continued to read an oxygen saturation of greater than 90%, while the actual 0,Hb fell below 30%. In the presence of COHb, the SpO, is approximately the sum of COHb and O,Hb, and, thus, may seriously overestimate 0,Hb. The pulse oximeter, as the sole indicator of blood oxygenation, should, therefore, be used with caution in patients with recent carbon monoxide exposure. On the other hand, transcutaneous Po, falls linearly as COHb increases, and reaches about one-fifth of its initial value at the highest COHb levels despite the maintenance of constant arterial PO,. (Reprinted with permission.) Accuracy
of Response
Hypoxia.
Severinghaus
of Six Pulse
JW,
Naifeh,
Oximeters
KH.
to Profound
Anesthesiology
67551, 1987. Oxygen saturation, Sp,%, was recorded during rapidly induced 42.4 + 7.2-s plateaus of profound hypoxia at 40-70% saturation by 1 or 2 pulse oximeters from each of six manufacturers (NE = Nellcor NlOOe, OH = Ohmeda 3700e, NO - Novametrix 500@versions 2.2 and 3.3 (revised instrumentation), CR - Criticare CSI 501+@ version .27 and version .28 in 501 & 502 (revised instrumentation), PC - PhysioControl Lifestat 1600@, and MQ = Marquest/ Minolta PulseOx 78). Usually, one probe of each pair was mounted on the ear, the other on a finger. Semi-recumbent, healthy, normotensive, non-smoking Caucasian or asian volunteers (age range 18-64 yr) performed the test six to seven times each. After insertion of a radial artery catheter, subjects hyperventilated 3% CO,, O-5% O*, balance N,. Saturation Sco,, computed on-line from mass spectrometer end-tidal PO, and P,, was used to manually adjust Fro, breath by breath to obtain a rapid fall to a hypoxic plateau lasting 30-45s, followed by rapid resaturation. Arterial Hb,,% (Radiometer OSM-3”) sampled near the end of the plateau averaged 55.5 + 7.5%. SC,% (from the mass spectrometer) and Sa,% (from pH and P%, by Corning 178@) differed from Hb%% by + 0.2 t 3.6% and 0.4 f 2.8%. respectively. The plateaus were always long enough to permit instruments to demonstrate a plateau with ear probes, but finger probes sometimes failed to provide plateaus in subjects with peripheral vasoconstriction. Nonetheless, Sp,, read significantly too low with finger probes at 55% mean Saol The mean error with ear probes was not significant. Several instruments occasionally defaulted to zero saturation during rapid desaturation. Precision was independent of probe location, but differed widely between instruments. The studies provided data with which manufacturers could improve function, as illustrated by subsequent series with CR and NO.
The authors conclude that square-waves of hypoxia can assess both the transient and the steady-state profound hypoxic responses of pulse oximeters, disclosing a variety of problems, and facilitating their resolution. An addendum follows the article. (Reprinted with permission.) Bedside
Measurement
Patients
With
KE, Hill
RD. et al.
Acute
of Pulmonary Respiratory
Capillary
Failure.
in
Pressure
Collee
GG, Lynch
Anesthesiology 66:614, 1987.
In this report, the authors present the results of 34 estimates of pulmonary capillary pressure (Pcap) in 15 adult patients receiving intensive care for acute respiratory failure (ARF). Within the pulmonary artery pressure profile during transient balloon occlusion, the authors identified two exponential pressure decay components-the slower one representing the discharge of the pulmonary capillary pressure through the pulmonary venous resistance. By extrapolating this exponential to its origin at the moment of pulmonary artery occlusion, a pressure within the pulmonary vascular bed which approximates pulmonary capillary pressure (Pcap) was identified. Pcap and not the pulmonary artery occlusion pressure (PAOP), is the major driving pressure forcing fluid from the pulmonary microvasculature. The results indicate that a discrete value for pulmonary capillary pressure can be reproducibly measured in paralyzed ventilated patients. The data report that mean pulmonary artery pressure, pulmonary capillary pressure, and total pulmonary vascular resistance (PVR) are increased in acute respiratory failure, but there is considerable variation in the distribution of pulmonary vascular resistance between the arterial and venous beds. The data suggest that there in unequal and variable partitioning of the increased PVR during acute respiratory failure. Bedside pressure profile Pcap measurements will allow optimum reduction of Pcap during ARF by infusing vasoactive agents to modify the distribution of PVR or reducing the PAOP. (Reprinted with permission.) Accurate, Automated, Continuously Displayed Artery Pressure Measurement. Mitchell MM,
Jones BR, et al.
Pulmonary
Meathe
EA.
Anesthesiology 671294, 1987.
A computerized signal processing technique that removes low-frequency respiratory variation from pulmonary artery pressure and other central vascular pressure measurements, and produces a waveform devoid of respiratory artifact, has been developed. This technique has been integrated into a portable bedside monitor. The authors tested the technique in critically ill patients, and found that, compared to physician readings of conventional strip charts, it proved to be a very convenient and accurate method of determining pulmonary artery pressures continuously, regardless of ventilation. (Reprinted with permission.) Postoperative Analgesia of Bupivacaine-Adrenaline.
Tokics
L, et al.
With
lntrspleurel
Brismar.
Administration
B,
Pettersson
N,
Acta Anaesthesiol Stand 31:515, 1987.
Twenty-one patients who underwent elective cholecystectomy were studied with regard to the effect of intrapleural administration of bupivacaine-adrenaline solution on postop-