Skip to main content
 

Main menu

  • Home
  • Content
    • Current Issue
    • Editor's Commentary
    • Archives
    • Most-Read Papers of 2022
  • Authors
    • Author Guidelines
    • Submit a Manuscript
  • Reviewers
    • Reviewer Information
    • Create Reviewer Account
    • Reviewer Guidelines: Original Research
    • Reviewer Guidelines: Reviews
    • Appreciation of Reviewers
  • CRCE
    • Through the Journal
    • JournalCasts
    • AARC University
    • PowerPoint Template
  • Open Forum
    • 2023 Open Forum
    • 2023 Abstracts
    • Previous Open Forums
  • Podcast
    • English
    • Español
    • Portugûes
    • 国语
  • Videos
    • Video Abstracts
    • Author Interviews
    • The Journal

User menu

  • Subscribe
  • My alerts
  • Log in

Search

  • Advanced search
American Association for Respiratory Care
  • Subscribe
  • My alerts
  • Log in
American Association for Respiratory Care

Advanced Search

  • Home
  • Content
    • Current Issue
    • Editor's Commentary
    • Archives
    • Most-Read Papers of 2022
  • Authors
    • Author Guidelines
    • Submit a Manuscript
  • Reviewers
    • Reviewer Information
    • Create Reviewer Account
    • Reviewer Guidelines: Original Research
    • Reviewer Guidelines: Reviews
    • Appreciation of Reviewers
  • CRCE
    • Through the Journal
    • JournalCasts
    • AARC University
    • PowerPoint Template
  • Open Forum
    • 2023 Open Forum
    • 2023 Abstracts
    • Previous Open Forums
  • Podcast
    • English
    • Español
    • Portugûes
    • 国语
  • Videos
    • Video Abstracts
    • Author Interviews
    • The Journal
  • Twitter
  • Facebook
  • YouTube
  • LinkedIn
Research ArticleOriginal Research

End-Tidal-to-Arterial PCO2 Ratio as Signifier for Physiologic Dead-Space Ratio and Oxygenation Dysfunction in Acute Respiratory Distress Syndrome

Richard H Kallet and Michael S Lipnick
Respiratory Care February 2021, 66 (2) 263-268; DOI: https://doi.org/10.4187/respcare.08061
Richard H Kallet
Department of Anesthesia and Perioperative Care, Respiratory Care Division, University of California, San Francisco at San Francisco General Hospital, San Francisco, California.
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • For correspondence: [email protected]
Michael S Lipnick
Department of Anesthesia and Perioperative Care, Critical Care Division, University of California, San Francisco at San Francisco General Hospital, San Francisco, California.
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Figures & Data
  • Info & Metrics
  • References
  • PDF
Loading

Abstract

BACKGROUND: The ratio of end-tidal CO2 pressure to arterial partial pressure of CO2 (Embedded Image) was recently suggested for monitoring pulmonary gas exchange in patients with ARDS associated with COVID-19, yet no evidence was offered supporting that claim. Therefore, we evaluated whether Embedded Image might be relevant in assessing ARDS not associated with COVID-19.

METHODS: We evaluated the correspondence between Embedded Image and the ratio of dead space to tidal volume (VD/VT) measured in 561 subjects with ARDS from a previous study in whom Embedded Image data were also available. Subjects also were analyzed according to 4 ranges of Embedded Image representing increasing illness severity (≥ 0.80, 0.6–0.79, 0.50–0.59, and < 0.50). Correlation was assessed by either Pearson or Spearman tests, grouped comparisons were assessed using either ANOVA or Kruskal-Wallis tests and dichotomous variables assessed by Fisher Exact tests. Normally distributed data are presented as mean and standard deviation(SD) and non-normal data are presented as median and inter-quartile range (IQR). Overall mortality risk was assessed with multivariate logistic regression. Alpha was set at 0.05.

RESULTS: Embedded Image correlated strongly with VD/VT (r = –0.87 [95% CI –0.89 to –0.85], P < .001). Decreasing Embedded Image was associated with increased VD/VT and hospital mortality between all groups. In the univariate analysis, for every 0.01 decrease in Embedded Image, mortality risk increased by ∼1% (odds ratio 0.009, 95% CI 0.003–0.029, P < .001) and maintained a strong independent association with mortality risk when adjusted for other variables (odds ratio 0.19, 95% CI 0.04–0.91, P = .039). Embedded Image < 0.50 was characterized by very high mean ± SD value for VD/VT (0.82 ± 0.05, P < .001) and high hospital mortality (70%).

CONCLUSIONS: Using Embedded Image as a surrogate for VD/VT may be a useful and practical measurement for both management and ongoing research into the nature of ARDS.

  • ARDS
  • ratio of arterial-to-alveolar oxygen tension
  • ratio of dead space to tidal volume
  • end-tidal carbon dioxide pressure

Introduction

The seminal study by Nuckton and colleagues1 demonstrated that the ratio of physiologic dead space to tidal volume (VD/VT) at ARDS onset was a strong, independent predictor of mortality risk. Since then, numerous studies have confirmed and expanded these findings.2-9 Others have demonstrated the value of using VD/VT measurements to detect lung recruitment and de-recruitment,10-14 as well as insight into the effects of pharmacologic therapies for ARDS.15-17

Unfortunately, it has been our perception that, despite both the clinical value of VD/VT and wide access to indirect calorimetry and volumetric capnography monitors, measuring VD/VT has not been universally embraced by the larger critical care community.18,19 Surrogate measures for estimating VD/VT now are commonly utilized and include versions of the Harris-Benedict or other equations.20,21 Another is the ventilatory ratio, which compares arterial partial pressure of CO2 (Embedded Image) and minute ventilation to corresponding “ideal” and “predicted” values as a signifier for VD/VT.22 In the absence of bedside capnography, these substitutes serve an important function.

Despite the general lack of enthusiasm for measuring VD/VT, bedside capnography is much more widely used to measure end-tidal CO2 pressure (Embedded Image). Given this backdrop amid the current COVID-19 pandemic, Gattinoni and colleagues23 offered the ratio of Embedded Image to evaluate pulmonary gas exchange dysfunction. Specifically, they stated that Embedded Image < 1 “suggests” the presence of elevated intrapulmonary shunt fraction and VD/VT. With few exceptions (eg, differences in how Embedded Image and expired Embedded Image are measured, or the effect of prolonged expiratory time constants on Embedded Image), there is always a positive difference between Embedded Image and Embedded Image. Therefore, Embedded Image will always be < 1, regardless of the severity of gas-exchange dysfunction. Therefore, without citing supportive evidence, the suggestion is not particularly informative.

We were intrigued by the possibility that Embedded Image might be a meaningful signifier for pulmonary gas exchange dysfunction in ARDS in general. Because Embedded Image is easily calculated with readily available technology at the bedside, it may be useful both for patient management and ongoing research into the course of ARDS. It may also obviate the need for calculating surrogate measures when basic capnography is available at the bedside. Therefore, we retrospectively studied the association between Embedded Image and measurements of gas exchange dysfunction in a large number of ARDS subjects.

QUICK LOOK

Current knowledge

The ratio of dead space to tidal volume (VD/VT) increases with ARDS severity and is strongly associated with increasing intrapulmonary shunt and mortality. Assessing each of these variables requires additional data collection or calculations that are not widely performed in clinical practice. In contrast, basic bedside capnography is widely practiced. Both increasing dead-space ventilation and oxygenation dysfunction are associated with an increased difference between arterial partial pressure of CO2 (Embedded Image) and end-tidal CO2 pressure (Embedded Image).

What this paper contributes to our knowledge

In ARDS, a strong association exists between an increasing VD/VT and a decreasing Embedded Image ratio, with only a moderate association with increasing oxygenation dysfunction. The use of ratio cutoff values representing increasing severity of Embedded Image was significantly associated with an increasing VD/VT, oxygenation dysfunction, illness severity scores, and mortality, and this might be a convenient and useful measurement for both clinical management and research into the nature and progression of ARDS.

Methods

Data were abstracted from a previous study of VD/VT using volumetric capnography in subjects with early ARDS.3 Briefly, contemporaneous measurements of expired gas and arterial blood gases along with full ventilator systems checks were made early in the course of ARDS (99% within 48 h of syndrome onset) via volumetric capnopgraphy.3 These subjects were managed with the National Institutes of Health ARDS Clinical Trials Network ventilator protocol, which was adopted for clinical management in 2000.24,25 In 2010, the wide availability of volumetric capnography at San Francisco General Hospital allowed us to incorporate VD/VT measurements into our routine assessment and clinical management of ARDS. Between 2010 and 2017, 561 of the original 685 subjects (82%) from the previous study also had paired measurements for Embedded Image and Embedded Image available for analysis.3 As detailed in the previous study, illness severity scores were calculated on the day of ARDS onset along with basic demographic information and status at hospital discharge.

We assessed oxygenation using the ratio of arterial-to-alveolar oxygen tension (Embedded Image) because it is a more precise physiologic measure of pulmonary oxygen diffusion as it accounts for alveolar Embedded Image,26 and thus the effects of permissive hypercapnia during lung-protective ventilation. In addition, Embedded Image values < 0.50 are associated with high degrees of intrapulmonary shunt, particularly at Embedded Image ≥ 0.50.26-28 We also used the formula Embedded Image because it reflects both alveolar and shunt-associated dead space.

Data are reported as either mean ± SD or median and interquartile range (IQR). Correlation between variables were assessed with Pearson or Spearman tests. Comparisons between groups were made using one-way analysis of variance and Tukey-Kramer multiple comparison tests, or with Kruskal-Wallis multiple comparisons test and Dunn post-test. Paired comparisons were made using either unpaired t test or the Mann-Whitney test. Dichotomous variables were assessed with the Fisher exact test. Data were analyzed using PRISM 8.4 (GraphPad, La Jolla, California). Alpha was set at 0.05. Use of this database was approved by the University of California, San Francisco Committee on Human Research.

Data were analyzed in 3 ways. First, the correlation between Embedded Image with VD/VT and Embedded Image was assessed. Second, data were categorized into ranges of Embedded Image that represent increasing severity of CO2 excretion dysfunction. Because the data were skewed toward values suggesting less severe dysfunction (ie, 73% were ≥ 0.60), we divided Embedded Image data into 4 groups that would facilitate clinical apprehension: ≥ 0.80, 0.6–0.79, 0.50–0.59, and < 0.50. Within these groupings, we also included variables previously shown to be associated with hospital mortality in other studies3,22,29,30: Acute Physiology and Chronic Health Evaluation score (APACHE II),31 Simplified Acute Physiology Score (SAPS II),32 age, presence of sepsis, enrollment eligibility criteria used by the ARDS Clinical Trials Network,25 cutoff values signifying organ dysfunction (eg, platelets < 150 × 103/mm3, total bilirubin > 2 mg/dL), ventilatory ratio, oxygenation index, respiratory system compliance, and driving pressure. Third, we performed step-wise, backward, logistical regression modeling using the variables described above. Variables with a P value < .10 were entered into the final model. Model goodness of fit was assessed with the Hosmer-Lemeshow test.

Results

A strong negative relationship was found between Embedded Image and VD/VT: r = –0.87 (95% CI –0.89 to –0.85), P < .001 (Fig. 1). In contrast, only a moderate relationship was found with Embedded Image: r = 0.46 (95% CI 0.38–0.52), P < .001. Analyzing subjects by group revealed that decreasing Embedded Image coincided with elevated VD/VT and ventilatory ratio, decreasing Embedded Image, increasing oxygenation index, and increasing APACHE II and SAPS II scores (Table 1). All comparisons between variables across groups were statistically significant. Values of Embedded Image < 0.50 coincided with very high VD/VT and low Embedded Image (ie, only 14% of alveolar partial pressure of O2 was reflected in arterial partial pressure of O2). The mortality risk was significant between all 4 groups. As Embedded Image decreased, hospital mortality increased from 20% at values ≥ 0.80 to 70% when Embedded Image fell to < 0.50 (Table 2, Fig. 2). All measures of gas exchange dysfunction distinguished survivors from non-survivors (Table 3).

Fig. 1.
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 1.

Relationship between groupings of the ratio of end-tidal CO2 pressure to arterial partial pressure of CO2 pressure (Embedded Image) by severity and corresponding ratio of physiologic dead space to tidal volume (VD/VT).

View this table:
  • View inline
  • View popup
  • Download powerpoint
Table 1.

Gas Exchange and Illness Severity Characteristics Across Ranges of Embedded Image

View this table:
  • View inline
  • View popup
  • Download powerpoint
Table 2.

Hospital Mortality Across Ranges of Embedded Image

Fig. 2.
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 2.

Relationship between groupings of the ratio of end-tidal CO2 pressure to arterial partial pressure of CO2 pressure (Embedded Image) by severity and corresponding hospital mortality.

View this table:
  • View inline
  • View popup
  • Download powerpoint
Table 3.

Differences Between Survivors and Non-Survivors in Measures of Gas Exchange Dysfunction

In the univariate analysis, for every 0.01 increase in Embedded Image, mortality risk decreased by ∼1% (odds ratio 0.009, 95% CI 0.003–0.029, P < .001) (Fig. 3). In multivariate logistic regression modeling, both Embedded Image and ventilatory ratio remained independent predictors of mortality after controlling for other variables (Table 4). Area under the receiver operating characteristic curve was 0.84 (95% CI 0.81–0.87), P < .001.

Fig. 3.
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 3.

Univariate analysis of the ratio of end-tidal CO2 pressure to arterial partial pressure of CO2 pressure (Embedded Image) and mortality risk.

View this table:
  • View inline
  • View popup
  • Download powerpoint
Table 4.

Mortality as a Function of Embedded Image

Discussion

The primary finding of our study is that, during lung-protective ventilation, decreasing Embedded Image in early ARDS is associated with increasing VD/VT, oxygenation dysfunction, illness severity scores, and mortality. Moreover, Embedded Image is independently associated with mortality risk after adjusting for variables known to increase mortality in ARDS. Our findings were similar to those that we previously reported for ventilatory ratio, which is another surrogate for VD/VT.22 Therefore, Embedded Image is a convenient and elegant surrogate for VD/VT that can be used to assess both pulmonary function and mortality risk in ARDS.

As implied in the methods section, Embedded Image is derived from an equation often used for estimating alveolar dead space: Embedded Image. However, accurate measurement of alveolar dead space requires volumetric capnography (ie, the ability to measure the slope of phase III in the capnograph).33 Embedded Image itself is an unreliable indicator of true alveolar dead space.34 This stems from the fact that, like the Enghoff modification of the Bohr equation, utilizing Embedded Image introduces the alveolar-capillary interface as a factor.35 In the presence of increased intrapulmonary shunt, as occurs in ARDS, rising Embedded Image coincides with decreasing Embedded Image.36 Considerable intrapulmonary shunting accounts for 20–33% of alveolar dead space in animal models.37 In our study, alveolar and shunt-associated dead space accounted for over half of the measured physiologic dead space as Embedded Image fell to < 0.60.

As mentioned earlier, despite 2 decades of research demonstrating the value of directly measuring VD/VT in patients with ARDS, adoption of this measurement as part of routine clinical management remains relatively sparse. This has motivated others to find alternative signifiers of dead space, particularly for evaluating mortality in large databases rather than evaluating the effects of therapy per se.

Estimating VD/VT based upon approximations of resting energy expenditure to calculate CO2 production substantially underestimates measured VD/VT, with reported bias ranging from –0.16 to –0.32.13,38 Nonetheless, in non-survivors all estimates of VD/VT have been reported to be significantly higher compared to estimates in survivors.38 In particular, an unadjusted estimate of VD/VT in both survivors and non-survivors (eg, those not correcting resting energy expenditure for body temperature) were very close to those in whom VD/VT was measured.38

Likewise, we previously reported that ventilatory ratio is moderately correlated with VD/VT (r = 0.66, P < .001) and was independently associated with mortality both in univariate and multivariate analyses at 2.07 (95% CI 1.53–2.85, P < .001) and 1.59 (95% CI 1.15–2.32, P = .004), respectively.22 In our study, which consisted of a large subset of data from a previous study, we found a moderate but slightly weaker correlation between ventilatory ratio and VD/VT (r = 0.55, P < .001) and a modestly higher mortality association in both the univariate and multivariate analyses at 2.25 (95% CI 1.68–3.07, P < .001) and 1.63 (95% CI 1.06–2.53, P = .03).

Ventilatory ratio is a less unwieldly method for evaluating the relationship between CO2 excretion dysfunction and ARDS compared to derivations based upon the Harris-Benedict and other equations. Thus, it is perhaps ideal for use in large observational or interventional studies when capnography is not widely used. Nonetheless, ventilatory ratio itself is somewhat unwieldly for clinical use compared to Embedded Image. In particular, it does not translate as easily when evaluating interventions such as PEEP titration, prone positioning, or recruitment maneuvers. Regardless of these small differences, when direct measurement of VD/VT is unavailable, either method is a suitable substitute.

Conclusions

Our analysis suggests that Embedded Image can be used as a surrogate for both VD/VT and oxygenation dysfunction in patients with ARDS. Similar to elevated VD/VT in early ARDS, decreasing Embedded Image is also associated with increasing illness severity and mortality risk. Although Embedded Image was recently proposed specifically for monitoring patients with ARDS associated with COVID-19, currently there are no data available to evaluate its potential relevance or utility.

Footnotes

  • Correspondence: Richard H Kallet MSc RRT FAARC, 2070 Fell St, Apt #1, San Francisco, CA 94117. E-mail: richkallet{at}gmail.com
  • Mr Kallet has disclosed a relationship with Nihon Kohden. Dr Lipnick has disclosed no conflicts of interest.

  • Copyright © 2021 by Daedalus Enterprises

References

  1. 1.↵
    1. Nuckton TJ,
    2. Alonso JA,
    3. Kallet RH,
    4. Daniel BM,
    5. Pittet JF,
    6. Eisner MD,
    7. et al
    . Pulmonary dead-space fraction as a risk factor for death in the acute respiratory distress syndrome. N Engl J Med 2002;346(17):1281-1286.
    OpenUrlCrossRefPubMed
  2. 2.↵
    1. Kallet RH,
    2. Alonso JA,
    3. Pittet JF,
    4. Matthay MA
    . Prognostic value of the pulmonary dead-space fraction during the first 6 days of acute respiratory distress syndrome. Respir Care 2004;49(9):1008-1014.
    OpenUrlAbstract/FREE Full Text
  3. 3.↵
    1. Kallet RH,
    2. Zhuo H,
    3. Ho K,
    4. Lipnick MS,
    5. Gomez A,
    6. Matthay MA
    . Lung injury etiology and other factors influencing the relationship between dead-space fraction and mortality in ARDS. Respir Care 2017;62(10):1241-1248.
    OpenUrlAbstract/FREE Full Text
  4. 4.
    1. Raurich JM,
    2. Vilar M,
    3. Colomar A,
    4. Ibanez J,
    5. Ayestaran I,
    6. Perez-Barcena J,
    7. et al
    . Prognostic value of the pulmonary dead-space fraction during the early and intermediate phases of acute respiratory distress syndrome. Respir Care 2010;55(3):282-287.
    OpenUrlAbstract/FREE Full Text
  5. 5.
    1. Cepkova M,
    2. Kapur V,
    3. Ren X,
    4. Quinn T,
    5. Zhuo H,
    6. Foster E,
    7. et al
    . Pulmonary dead space fraction and pulmonary artery systolic pressure as early predictors of clinical outcome in acute lung injury. Chest 2007;132(3):836-842.
    OpenUrlCrossRefPubMed
  6. 6.
    1. Phillips CR,
    2. Chesnutt MS,
    3. Smith SM
    . Extravascular lung water in sepsis-associated acute respiratory distress syndrome: indexing with predicted body weight improves correlation with severity of illness and survival. Crit Care Med 2008;36(1):69-73.
    OpenUrlCrossRefPubMed
  7. 7.
    1. Lucangelo U,
    2. Bernabe F,
    3. Vatua S,
    4. Degrassi G,
    5. Villagra A,
    6. Fernandez R,
    7. et al
    . Prognostic value of different dead space indices in mechanically ventilated patients with acute lung injury and ARDS. Chest 2008;133(1):62-71.
    OpenUrlCrossRefPubMed
  8. 8.
    1. Kallet RH,
    2. Zhuo H,
    3. Liu KD,
    4. Calfee CS,
    5. Matthay MA
    , National Heart Lung and Blood Institute ARDS Network Investigators. The association between physiologic dead-space fraction and mortality in subjects with ARDS enrolled in a prospective multi-center clinical trial. Respir Care 2014;59(11):1611-1618.
    OpenUrlAbstract/FREE Full Text
  9. 9.↵
    1. Kallet RH,
    2. Ho K,
    3. Lipnick MS,
    4. Matthay MA
    . Pulmonary mechanics and gas exchange characteristics in uncommon etiologies of acute respiratory distress syndrome. J Thorac Dis 2018;10(8):5030-5038.
    OpenUrl
  10. 10.↵
    1. Fengmei G,
    2. Jin C,
    3. Songqiao L,
    4. Congshan Y,
    5. Yi Y
    . Dead space fraction changes during PEEP titration following lung recruitment in patients with ARDS. Respir Care 2012;57(10):1578-1585.
    OpenUrlAbstract/FREE Full Text
  11. 11.
    1. Bohm SH,
    2. Maisch S,
    3. von Sandersleben A,
    4. Thamm O,
    5. Passoni I,
    6. Martinez Arca J,
    7. et al
    . The effects of lung recruitment on the phase III slope of volumetric capnography in morbidly obese patients. Anesth Analg 2009;109(1):151-159.
    OpenUrlCrossRefPubMed
  12. 12.
    1. Maisch S,
    2. Reissmann H,
    3. Fuellekrug B,
    4. Weismann D,
    5. Rutkowski T,
    6. Tusman G,
    7. et al
    . Compliance and dead space fraction indicate an optimal level of positive end-expiratory pressure after recruitment in anesthetized patients. Anesth Analg 2008;106(1):175-181.
    OpenUrlCrossRefPubMed
  13. 13.↵
    1. Charron C,
    2. Repesse X,
    3. Bouferrache K,
    4. Bodson L,
    5. Castro S,
    6. Page B,
    7. et al
    . PaCO2 and alveolar dead space are more relevant than PaO2/FiO2 ratio in monitoring the respiratory response to prone position in ARDS patients: a physiological study. Crit Care 2011;15(4):R175.
    OpenUrlCrossRefPubMed
  14. 14.↵
    1. Unzueta C,
    2. Tusman G,
    3. Suarez-Sipmann F,
    4. Bohm S,
    5. Moral V
    . Alveolar recruitment improves ventilation during thoracic surgery: a randomized controlled trial. Br J Anaesth 2012;108(3):517-524.
    OpenUrlCrossRefPubMed
  15. 15.↵
    1. Liu KD,
    2. Levitt J,
    3. Zhuo H,
    4. Kallet RH,
    5. Brady S,
    6. Steingrub J,
    7. et al
    . Randomized clinical trial of activated protein C for the treatment of acute lung injury. Am J Respir Crit Care Med 2008;178(6):618-623.
    OpenUrlCrossRefPubMed
  16. 16.
    1. Kallet RH,
    2. Jasmer RM,
    3. Pittet JF
    . Alveolar dead-space response to activated protein C in acute respiratory distress syndrome. Respir Care 2010;55(5):617-622.
    OpenUrlAbstract/FREE Full Text
  17. 17.↵
    1. Raurich JM,
    2. Ferreruela M,
    3. Llompart-Pou JA,
    4. Vilar M,
    5. Colomar A,
    6. Ayestaran I,
    7. et al
    . Potential effects of corticosteroids on physiological dead-space fraction in acute respiratory distress syndrome. Respir Care 2012;57(3):377-383.
    OpenUrlAbstract/FREE Full Text
  18. 18.↵
    1. Kallet RH,
    2. Daniel BM,
    3. Garcia O,
    4. Matthay MA
    . Accuracy of physiologic dead space measurements in patients with acute respiratory distress syndrome using volumetric capnography: comparison with the metabolic monitor method. Respir Care 2005;50(4):462-467.
    OpenUrlAbstract/FREE Full Text
  19. 19.↵
    1. Doorduin J,
    2. Nollet JL,
    3. Vugts MP,
    4. Roesthuis LH,
    5. Akankan F,
    6. van der Hoeven JG,
    7. et al
    . Assessment of dead-space ventilation in patients with acute respiratory distress syndrome: a prospective observational study. Crit Care 2016;20(1):121.
    OpenUrl
  20. 20.↵
    1. Siddiki H,
    2. Kojicic M,
    3. Li G,
    4. Yilmaz M,
    5. Thompson TB,
    6. Hubmayr RD,
    7. et al
    . Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials. Crit Care 2010;14(4):R141.
    OpenUrlCrossRefPubMed
  21. 21.↵
    1. Pais FM,
    2. Sinha P,
    3. Liu KD,
    4. Matthay MA
    . Influence of clinical factors and exclusion criteria on mortality in ARDS observational studies and randomized controlled trials. Respir Care 2018;63(8):1060-1069.
    OpenUrlAbstract/FREE Full Text
  22. 22.↵
    1. Sinha P,
    2. Calfee CS,
    3. Beitler JR,
    4. Soni N,
    5. Ho K,
    6. Matthay MA,
    7. et al
    . Physiologic analysis and clinical performance of the ventilatory ratio in acute respiratory distress syndrome. Am J Respir Crit Care Med 2019;199(3):333-341.
    OpenUrl
  23. 23.↵
    1. Gattinoni L,
    2. Chiumello D,
    3. Rossi S
    . COVID-19 pneumonia: ARDS or not? Crit Care 2020;24(1):154.
    OpenUrlPubMed
  24. 24.↵
    1. Kallet RH,
    2. Jasmer RM,
    3. Pittet JF,
    4. Tang JF,
    5. Campbell AR,
    6. Dicker R,
    7. et al
    . Clinical implementation of the ARDS network protocol is associated with reduced hospital mortality compared with historical controls. Crit Care Med 2005;33(5):925-929.
    OpenUrlCrossRefPubMed
  25. 25.↵
    1. Brower RG,
    2. Matthay MA,
    3. Morris A,
    4. Schoenfeld D,
    5. Thompson BT,
    6. et al
    Acute Respiratory Distress Syndrome Network, Brower RG, Matthay MA, Morris A, Schoenfeld D, Thompson BT, et al. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342(18):1301-1308.
    OpenUrlCrossRefPubMed
  26. 26.↵
    1. Gilbert R,
    2. Auchincloss JH Jr.,
    3. Kuppinger M,
    4. Thomas MV
    . Stability of the arterial/alveolar oxygen partial pressure ratio. Effects of low ventilation/perfusion regions. Crit Care Med 1979;7(6):267-272.
    OpenUrlCrossRefPubMed
  27. 27.
    1. Doyle DJ
    . Arterial/alveolar oxygen tension ratio: a critical appraisal. Can Anaesth Soc J 1986;33(4):471-474.
    OpenUrlPubMed
  28. 28.↵
    1. Bredenberg CE,
    2. James PM,
    3. Collins J,
    4. Anderson RW,
    5. Martin AM Jr.,
    6. Hardaway RM
    3rd. Respiratory failure in shock. Ann Surg 1969;169(3):392-403.
    OpenUrlPubMed
  29. 29.↵
    1. Seeley E,
    2. McAuley DF,
    3. Eisner M,
    4. Miletin M,
    5. Matthay MA,
    6. Kallet RH
    . Predictors of mortality in acute lung injury during the era of lung protective ventilation. Thorax 2008;63(11):994-998.
    OpenUrlAbstract/FREE Full Text
  30. 30.↵
    1. Kallet RH,
    2. Lipnick MS,
    3. Zhuo H,
    4. Pangilinan LP,
    5. Gomez A
    . Characteristics of Nonpulmonary Organ Dysfunction at Onset of ARDS Based on the Berlin Definition. Respir Care 2019;64(5):493-501.
    OpenUrlAbstract/FREE Full Text
  31. 31.↵
    1. Knaus WA,
    2. Draper EA,
    3. Wagner DP,
    4. Zimmerman JE
    . APACHE II: a severity of disease classification system. Crit Care Med 1985;13(10):818-829.
    OpenUrlCrossRefPubMed
  32. 32.↵
    1. Le Gall JR,
    2. Lemeshow S,
    3. Saulnier F
    . A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study. JAMA 1993;270(24):2957-2963.
    OpenUrlCrossRefPubMed
  33. 33.↵
    1. Fletcher R,
    2. Jonson B,
    3. Cumming G,
    4. Brew J
    . The concept of deadspace with special reference to the single breath test for carbon dioxide. Br J Anaesth 1981;53(1):77-88.
    OpenUrlCrossRefPubMed
  34. 34.↵
    1. Hardman JG,
    2. Aitkenhead AR
    . Estimation of alveolar deadspace fraction using arterial and end-tidal CO2: a factor analysis using a physiological simulation. Anaesth Intensive Care 1999;27(5):452-458.
    OpenUrlPubMed
  35. 35.↵
    1. Kallet RH
    . Measuring dead-space in acute lung injury. Minerva Anestesiol 2012;78(11):1297-1305.
    OpenUrlPubMed
  36. 36.↵
    1. Tang Y,
    2. Turner MJ,
    3. Baker AB
    . Effects of alveolar dead-space, shunt and V/Q distribution on respiratory dead-space measurements. Br J Anaesth 2005;95(4):538-548.
    OpenUrlCrossRefPubMed
  37. 37.↵
    1. Severinghaus JW,
    2. Stupfel M
    . Alveolar dead space as an index of distribution of blood flow in pulmonary capillaries. J Appl Physiol 1957;10(3):335-348.
    OpenUrlPubMed
  38. 38.↵
    1. Beitler JR,
    2. Thompson BT,
    3. Matthay MA,
    4. Talmor D,
    5. Liu KD,
    6. Zhuo H,
    7. et al
    . Estimating dead-space fraction for secondary analyses of acute respiratory distress syndrome clinical trials. Crit Care Med 2015;43(5):1026-1035.
    OpenUrl
PreviousNext
Back to top

In this issue

Respiratory Care: 66 (2)
Respiratory Care
Vol. 66, Issue 2
1 Feb 2021
  • Table of Contents
  • Table of Contents (PDF)
  • Cover (PDF)
  • Index by author

 

Print
Download PDF
Article Alerts
Sign In to Email Alerts with your Email Address
Email Article

Thank you for your interest in spreading the word on American Association for Respiratory Care.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
End-Tidal-to-Arterial PCO2 Ratio as Signifier for Physiologic Dead-Space Ratio and Oxygenation Dysfunction in Acute Respiratory Distress Syndrome
(Your Name) has sent you a message from American Association for Respiratory Care
(Your Name) thought you would like to see the American Association for Respiratory Care web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
End-Tidal-to-Arterial PCO2 Ratio as Signifier for Physiologic Dead-Space Ratio and Oxygenation Dysfunction in Acute Respiratory Distress Syndrome
Richard H Kallet, Michael S Lipnick
Respiratory Care Feb 2021, 66 (2) 263-268; DOI: 10.4187/respcare.08061

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero

Share
End-Tidal-to-Arterial PCO2 Ratio as Signifier for Physiologic Dead-Space Ratio and Oxygenation Dysfunction in Acute Respiratory Distress Syndrome
Richard H Kallet, Michael S Lipnick
Respiratory Care Feb 2021, 66 (2) 263-268; DOI: 10.4187/respcare.08061
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Google Plus One

Jump to section

  • Article
    • Abstract
    • Introduction
    • Methods
    • Results
    • Discussion
    • Conclusions
    • Footnotes
    • References
  • Figures & Data
  • Info & Metrics
  • References
  • PDF

Related Articles

Cited By...

Keywords

  • ARDS
  • ratio of arterial-to-alveolar oxygen tension
  • ratio of dead space to tidal volume
  • end-tidal carbon dioxide pressure

Info For

  • Subscribers
  • Institutions
  • Advertisers

About Us

  • About the Journal
  • Editorial Board

AARC

  • Membership
  • Meetings
  • Clinical Practice Guidelines

More

  • Contact Us
  • RSS
American Association for Respiratory Care

Print ISSN: 0020-1324        Online ISSN: 1943-3654

© Daedalus Enterprises, Inc.

Powered by HighWire