Limitations of end-tidal CO2 as an early indicator of central hypovolemia in humans

John G. McManus, Kathy L. Ryan, Melinda J. Morton, Caroline A. Rickards, William H. Cooke, Victor A. Convertino

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Objective. This study tested the hypothesis that pulmonary end-tidal CO2 (PETCO2) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. Methods. Measurements of PETCO2, systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were obtained in 50 healthy human subjects during baseline supine rest and exposure to progressive reductions of central blood volume produced by application of lower body negative pressure (LBNP). Results. As increasing amounts of LBNP were applied, SBP, DBP, MAP, HR, SV, and PETCO2 decreased (p < 0.001). RR was not altered (p = 1.0). The decrease in PETCO2 did not begin to occur until 40% of maximal LBNP was applied. While PETCO2 decreased progressively thereafter, the range of baseline values (28.8-49.2 mmHg) varied more than the reduction in PETCO2 elicited by maximal LBNP (baseline = 40.1 ± 0.6 mmHg; maximal LBNP = 29.8 ± 1.0 mmHg). The earliest significant alteration was observed in SV, which occurred at 20% of maximal LBNP. MAP did not decline significantly until 80% of maximal LBNP was reached. PETCO2 was correlated positively with SV (r2 = 0.87). Conclusions. Although PETCO2tracked decreases in SV in this human model of progressive central hypovolemia, reductions in PETCO2were small relative to the range of baseline values. Thus, monitoring such small reductions in PETCO2 as an early warning of imminent cardiovascular collapse during hemorrhage may not be clinically useful without monitors capable of providing continuous trending.

Original languageEnglish (US)
Pages (from-to)199-205
Number of pages7
JournalPrehospital Emergency Care
Volume12
Issue number2
DOIs
StatePublished - Apr 1 2008
Externally publishedYes

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Lower Body Negative Pressure
Hypovolemia
Lung
Stroke Volume
Respiratory Rate
Blood Volume
Heart Rate
Volunteers
Healthy Volunteers
Arterial Pressure
Hemorrhage

Keywords

  • Cardiovascular collapse
  • Hemorrhagic shock
  • Lower body negative pressure

ASJC Scopus subject areas

  • Emergency Medicine
  • Emergency

Cite this

Limitations of end-tidal CO2 as an early indicator of central hypovolemia in humans. / McManus, John G.; Ryan, Kathy L.; Morton, Melinda J.; Rickards, Caroline A.; Cooke, William H.; Convertino, Victor A.

In: Prehospital Emergency Care, Vol. 12, No. 2, 01.04.2008, p. 199-205.

Research output: Contribution to journalArticle

McManus, John G. ; Ryan, Kathy L. ; Morton, Melinda J. ; Rickards, Caroline A. ; Cooke, William H. ; Convertino, Victor A. / Limitations of end-tidal CO2 as an early indicator of central hypovolemia in humans. In: Prehospital Emergency Care. 2008 ; Vol. 12, No. 2. pp. 199-205.
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abstract = "Objective. This study tested the hypothesis that pulmonary end-tidal CO2 (PETCO2) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. Methods. Measurements of PETCO2, systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were obtained in 50 healthy human subjects during baseline supine rest and exposure to progressive reductions of central blood volume produced by application of lower body negative pressure (LBNP). Results. As increasing amounts of LBNP were applied, SBP, DBP, MAP, HR, SV, and PETCO2 decreased (p < 0.001). RR was not altered (p = 1.0). The decrease in PETCO2 did not begin to occur until 40{\%} of maximal LBNP was applied. While PETCO2 decreased progressively thereafter, the range of baseline values (28.8-49.2 mmHg) varied more than the reduction in PETCO2 elicited by maximal LBNP (baseline = 40.1 ± 0.6 mmHg; maximal LBNP = 29.8 ± 1.0 mmHg). The earliest significant alteration was observed in SV, which occurred at 20{\%} of maximal LBNP. MAP did not decline significantly until 80{\%} of maximal LBNP was reached. PETCO2 was correlated positively with SV (r2 = 0.87). Conclusions. Although PETCO2tracked decreases in SV in this human model of progressive central hypovolemia, reductions in PETCO2were small relative to the range of baseline values. Thus, monitoring such small reductions in PETCO2 as an early warning of imminent cardiovascular collapse during hemorrhage may not be clinically useful without monitors capable of providing continuous trending.",
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AU - Ryan, Kathy L.

AU - Morton, Melinda J.

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AU - Cooke, William H.

AU - Convertino, Victor A.

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N2 - Objective. This study tested the hypothesis that pulmonary end-tidal CO2 (PETCO2) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. Methods. Measurements of PETCO2, systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were obtained in 50 healthy human subjects during baseline supine rest and exposure to progressive reductions of central blood volume produced by application of lower body negative pressure (LBNP). Results. As increasing amounts of LBNP were applied, SBP, DBP, MAP, HR, SV, and PETCO2 decreased (p < 0.001). RR was not altered (p = 1.0). The decrease in PETCO2 did not begin to occur until 40% of maximal LBNP was applied. While PETCO2 decreased progressively thereafter, the range of baseline values (28.8-49.2 mmHg) varied more than the reduction in PETCO2 elicited by maximal LBNP (baseline = 40.1 ± 0.6 mmHg; maximal LBNP = 29.8 ± 1.0 mmHg). The earliest significant alteration was observed in SV, which occurred at 20% of maximal LBNP. MAP did not decline significantly until 80% of maximal LBNP was reached. PETCO2 was correlated positively with SV (r2 = 0.87). Conclusions. Although PETCO2tracked decreases in SV in this human model of progressive central hypovolemia, reductions in PETCO2were small relative to the range of baseline values. Thus, monitoring such small reductions in PETCO2 as an early warning of imminent cardiovascular collapse during hemorrhage may not be clinically useful without monitors capable of providing continuous trending.

AB - Objective. This study tested the hypothesis that pulmonary end-tidal CO2 (PETCO2) tracks reductions in central blood volume in human volunteers exposed to progressive central hypovolemia. Methods. Measurements of PETCO2, systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures, heart rate (HR), stroke volume (SV), and respiratory rate (RR) were obtained in 50 healthy human subjects during baseline supine rest and exposure to progressive reductions of central blood volume produced by application of lower body negative pressure (LBNP). Results. As increasing amounts of LBNP were applied, SBP, DBP, MAP, HR, SV, and PETCO2 decreased (p < 0.001). RR was not altered (p = 1.0). The decrease in PETCO2 did not begin to occur until 40% of maximal LBNP was applied. While PETCO2 decreased progressively thereafter, the range of baseline values (28.8-49.2 mmHg) varied more than the reduction in PETCO2 elicited by maximal LBNP (baseline = 40.1 ± 0.6 mmHg; maximal LBNP = 29.8 ± 1.0 mmHg). The earliest significant alteration was observed in SV, which occurred at 20% of maximal LBNP. MAP did not decline significantly until 80% of maximal LBNP was reached. PETCO2 was correlated positively with SV (r2 = 0.87). Conclusions. Although PETCO2tracked decreases in SV in this human model of progressive central hypovolemia, reductions in PETCO2were small relative to the range of baseline values. Thus, monitoring such small reductions in PETCO2 as an early warning of imminent cardiovascular collapse during hemorrhage may not be clinically useful without monitors capable of providing continuous trending.

KW - Cardiovascular collapse

KW - Hemorrhagic shock

KW - Lower body negative pressure

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