A simple formula for adjusting arterial carbon dioxide tension

Wexler, H. R.; Lok, Peter

doi:10.1007/bf03007805

Cited by 42 publications

(51 citation statements)

References 4 publications

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“…Although this variation in dead space between Vt 6 and Vt 4 limits the possibility of comparing PaCO 2 and pH with both Vts, the purpose of this part of the study was just to determine if severe hypercapnia and respiratory acidosis could be avoided during ventilation with Vt 4. Although 30 minutes may seem a short period, it has been shown that it is enough to reach a new equilibrium in PaCO 2 after changes in ventilation [25,26]. Our data suggest that a ventilatory strategy based on a Vt of 4 ml/kg would be feasible in several ARDS patients.…”

Section: Discussionmentioning

confidence: 65%

Preliminary study of ventilation with 4 ml/kg tidal volume in acute respiratory distress syndrome: feasibility and effects on cyclic recruitment - derecruitment and hyperinflation

et al. 2013

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IntroductionCyclic recruitment-derecruitment and overdistension contribute to ventilator-induced lung injury. Tidal volume (Vt) may influence both, cyclic recruitment-derecruitment and overdistension. The goal of this study was to determine if decreasing Vt from 6 to 4 ml/kg reduces cyclic recruitment-derecruitment and hyperinflation, and if it is possible to avoid severe hypercapnia.MethodsPatients with pulmonary acute respiratory distress syndrome (ARDS) were included in a crossover study with two Vt levels: 6 and 4 ml/kg. The protocol had two parts: one bedside and other at the CT room. To avoid severe hypercapnia in the 4 ml/kg arm, we replaced the heat and moisture exchange filter by a heated humidifier, and respiratory rate was increased to keep minute ventilation constant. Data on lung mechanics and gas exchange were taken at baseline and after 30 minutes at each Vt (bedside). Thereafter, a dynamic CT (4 images/sec for 8 sec) was taken at each Vt at a fixed transverse region between the middle and lower third of the lungs. Afterward, CT images were analyzed and cyclic recruitment-derecruitment was determined as non-aerated tissue variation between inspiration and expiration, and hyperinflation as maximal hyperinflated tissue at end-inspiration, expressed as % of lung tissue weight.ResultsWe analyzed 10 patients. Decreasing Vt from 6 to 4 ml/kg consistently decreased cyclic recruitment-derecruitment from 3.6 (2.5 to 5.7) % to 2.9 (0.9 to 4.7) % (P <0.01) and end-inspiratory hyperinflation from 0.7 (0.3 to 2.2) to 0.6 (0.2 to 1.7) % (P = 0.01). No patient developed severe respiratory acidosis or severe hypercapnia when decreasing Vt to 4 ml/kg (pH 7.29 (7.21 to 7.46); PaCO2 48 (26 to 51) mmHg).ConclusionsDecreasing Vt from 6 to 4 ml/kg reduces cyclic recruitment-derecruitment and hyperinflation. Severe respiratory acidosis may be effectively prevented by decreasing instrumental dead space and by increasing respiratory rate.

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Section: Discussionmentioning

confidence: 65%

Preliminary study of ventilation with 4 ml/kg tidal volume in acute respiratory distress syndrome: feasibility and effects on cyclic recruitment - derecruitment and hyperinflation

et al. 2013

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“…A correlation between high dead space and mortality has been found in patients with ARDS [26]. Therefore, in our analysis, we used the “corrected minute ventilation” (VE corr ) as a surrogate for dead space [27] and found that even after adjusting for VE corr , severe hypercapnia remains strongly associated with mortality. Moreover, Brown et al [32] showed that a minute ventilation of >13.9 l/min was an important predictor of hospital mortality at 90 days in acute lung injury, similar to our findings (>14 l/min).…”

Section: Discussionmentioning

confidence: 99%

“…Because clinical practices regarding MV strategies in patients diagnosed with ARDS have changed over time, the model was also adjusted for the period of the study. In addition, because dead space is strongly associated with mortality [26] and may be a confounding factor for hypercapnia, we calculated the corrected minute ventilation (VE corr ) for a normal PaCO 2 (calculated as minute ventilation × actual PaCO 2 /40 mmHg) as a surrogate for dead space [27] and introduced this as a co-variable into the univariate and multivariate model. We created a vertical plot showing the adjusted odds ratio (OR) for ICU mortality and PaCO 2 as categorized.…”

Section: Methodsmentioning

confidence: 99%

Severe hypercapnia and outcome of mechanically ventilated patients with moderate or severe acute respiratory distress syndrome

et al. 2017

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Purpose To analyze the relationship between hypercapnia developing within the first 48 h after the start of mechanical ventilation and outcome in patients with acute respiratory distress syndrome (ARDS). Patients and methods We performed a secondary analysis of three prospective non-interventional cohort studies focusing on ARDS patients from 927 intensive care units (ICUs) in 40 countries. These patients received mechanical ventilation for more than 12 h during 1-month periods in 1998, 2004, and 2010. We used multivariable logistic regression and a propensity score analysis to examine the association between hypercapnia and ICU mortality. Main outcomes We included 1899 patients with ARDS in this study. The relationship between maximum PaCO2 in the first 48 h and mortality suggests higher mortality at or above PaCO2 of ≥50 mmHg. Patients with severe hypercapnia (PaCO2 ≥50 mmHg) had higher complication rates, more organ failures, and worse outcomes. After adjusting for age, SAPS II score, respiratory rate, positive end-expiratory pressure, PaO2/FiO2 ratio, driving pressure, pressure/volume limitation strategy (PLS), corrected minute ventilation, and presence of acidosis, severe hypercapnia was associated with increased risk of ICU mortality [odds ratio (OR) 1.93, 95% confidence interval (CI) 1.32 to 2.81; p = 0.001]. In patients with severe hypercapnia matched for all other variables, ventilation with PLS was associated with higher ICU mortality (OR 1.58, CI 95% 1.04–2.41; p = 0.032). Conclusions Severe hypercapnia appears to be independently associated with higher ICU mortality in patients with ARDS.

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“…For example, the ARDS Definition Task Force 9 attempted to use corrected minute ventilation (i.e. [Pa CO2 x minute ventilation] / 40) 21 as a potential surrogate for dead-space in defining those with severe lung injury. Yet this surrogate was not used in the final definition because of a “lack of evidence for predictive validity”.…”

Section: Discussionmentioning

confidence: 99%

The Association Between Physiologic Dead-Space Fraction and Mortality in Subjects With ARDS Enrolled in a Prospective Multi-Center Clinical Trial

et al. 2013

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Objective To test the association between pulmonary dead-space fraction (VD/VT) and mortality in patients with ARDS (Berlin Definition, PaO2/FiO2 ≤ 300 mm Hg; PEEP ≥ 5 cm H2O) enrolled into a clinical trial incorporating lung-protective ventilation. Design Prospective, multi-center study. Setting Medical-surgical intensive care units in the United States. Subjects 126 ALI patients enrolled into a phase III randomized, placebo-controlled study of aerosolized albuterol. Interventions None Measurements and Main Results VD/VT and pulmonary mechanics were measured within 4 hours of enrollment and repeated daily on study days 1 and 2 in subjects requiring arterial blood gases for clinical management. At baseline, non-survivors had a trend towards higher VD/VT compared to survivors (0.62 ± 0.11 vs. 0.56 ± 0.11 respectively, p = 0.08). Differences in VD/VT between non-survivors and survivors became significant on study days 1 (0.64 ± 0.12 vs. 0.55 ± 0.11 respectively, p = 0.01) and 2 (0.67 ± 0.12 vs. 0.56 ± 0.11 respectively, p=0.004). Likewise, the association between VD/VT and mortality was significant on study day 1 (odds ratio per 0.10 change in VD/VT [95% confidence interval]: 6.84 [1.62–28.84] p = 0.01; and study day 2: 4.90 [1.28–18.73] p = 0.02) after adjusting for VD/VT, PaO2/FiO2, oxygenation index, vasopressor use and the primary risk for ARDS. Using a Cox proportional hazard model, VD/VT was associated with a trend towards higher mortality (HR = 4.37 [CI: 0.99 – 19.32]; p = 0.052) that became significant when the analysis was adjusted for daily oxygenation index (HR = 1.74 [95% CI: 1.12 – 3.35] p = 0.04). Conclusions Markedly elevated VD/VT (≥ 0.60) in early ARDS is associated with higher mortality. Measuring VD/VT may be useful in identifying ARDS patients at increased risk of death who are enrolled into a therapeutic trial.

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A simple formula for adjusting arterial carbon dioxide tension

Cited by 42 publications

References 4 publications

Preliminary study of ventilation with 4 ml/kg tidal volume in acute respiratory distress syndrome: feasibility and effects on cyclic recruitment - derecruitment and hyperinflation

Preliminary study of ventilation with 4 ml/kg tidal volume in acute respiratory distress syndrome: feasibility and effects on cyclic recruitment - derecruitment and hyperinflation

Severe hypercapnia and outcome of mechanically ventilated patients with moderate or severe acute respiratory distress syndrome

The Association Between Physiologic Dead-Space Fraction and Mortality in Subjects With ARDS Enrolled in a Prospective Multi-Center Clinical Trial

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