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Comparison of Arterial-End-Tidal PCO2 Difference and Dead Space/Tidal Volume Ratio in Respiratory Failure
Section snippets
METHODS
Seven men and ten women patients between the ages of 25 and 80 years of age were studied. These patients, with a variety of clinical problems (Table I), required endotracheal intubation and mechanical ventilation and were taken from our medical-respiratory intensive care unit population.
Measurements on an individual patient were completed within a 20-min period during which no changes were made on any ventilator settings. All patients were ventilated with a volume-cycled ventilator (Bourns Bear
RESULTS
Patient characteristics and clinical diagnoses are presented in Table 1. Comparisons of individual and mean arterial Pco2, end-tidal Pco2, arterial-end-tidal Pco2 difference, and VD/VT (calculated using several methods) are shown in Table 2.
The difference between PaCO2 and PETCO2 can be seen in Figure 1, showing a considerable variation in PETCO2 for values of PaCO2. Figure 2 shows the relationship between P(a-et)CO2 and VD/VT. The P(a-et)CO2 varied from 0 to 39 mm Hg; P(a-et)CO2 correlated
DISCUSSION
In normal subjects at rest who have a VD/VT <0.30, the difference between PaCO2 and PEYCO2 is small.5, 11, 12 In these subjects, to whose lung units ventilation and perfusion are relatively uniformly distributed, the PCO2 of the mixture of blood coming from these units (PaCO2) is not much different from the PCO2 of gas in any individual lung unit. Thus, the PCO2 of lung units that empty at the end of expiration (PETCO2) is very close to PaCO2. However, in patients with lung disease, VD/VT can
REFERENCES (13)
- et al.
The arterial to end-expiratory carbon dioxide tension gradient in acute pulmonary embolism and other cardiopulmonary diseases
Chest
(1974) - et al.
Evaluation of the progress and prognosis of adult respiratory distress syndrome: simple respiratory physiologic measurement
Chest
(1979) - et al.
Titration of PEEP by the arterial minus end-tidal carbon dioxide gradient
Chest
(1984) Indications for arterial blood gas analysis
Ann Intern Med
(1986)- et al.
Endtidal carbon dioxide as a measure of arterial carbon dioxide during intermittent mandatory ventilation
Chest
(1981) - et al.
Physiologic dead space and alveolar-arterial gas pressure differences during exercise
Clin Sci
(1966)
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2019, NeuroImageCitation Excerpt :Et-CO2 is usually 2–5 mmHg lower than PaCO2 in healthy adults (Nunn and Hill, 1960), as about 1–2% alveoli are not participating in gas exchange in the lung, and thus, the air inside these alveoli dilutes CO2 in the exhaled air (Bhavani-Shankar et al., 1995; Fletcher et al., 1981). The volume of these poorly perfused alveoli, referred to as alveolar dead space, accounts for about 5–10% of the tidal volume in healthy adults (Williams et al., 1997) and varies with age and clinical situations (Askrog, 1966; Burrows, 1989; Yamanaka and Sue, 1987). Although Et-CO2 could be lower than PaCO2, a strong correlation between Et-CO2 and PaCO2 has been reported (McSwain et al., 2010; Peebles et al., 2007; Sullivan et al., 2005).
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Manuscript received December 19; revision accepted March 16.
Reprint requests: Dr. Sue, Harbor-UCLA Medical Center, 1000 West Carson Street, Torrance, CA 90509
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Fellow, Division of Respiratory Physiology and Medicine. Supported by PHS grant HL 07388.
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Associate Professor of Medicine