Preoperative Gender Differences in Pulmonary Gas Exchange in Morbidly Obese Subjects

Zavorsky, Gerald S.; Christou, Nicolas V.; Kim, Do Jun; Carli, Franco; Mayo, Nancy E.

doi:10.1007/s11695-008-9527-6

Cited by 23 publications

(51 citation statements)

References 45 publications

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“…16 Briefl y, 15 min prior to the o 2 peak test a rapid-response thermocouple was positioned in the hub of the radial artery catheter. The catheter and extension were routinely fl ushed with heparinized saline.…”

Section: Arterial Catheterizationmentioning

confidence: 99%

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Corrected End-Tidal PCO2 Accurately Estimates PaCO2 at Rest and During Exercise in Morbidly Obese Adults

Pouwels

Wit

Teijink

et al. 2013

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Measurements of arterial blood gases are important in studies of ventilatory control during exercise and can give valuable information about the effi ciency of ventilation and gas exchange. To avoid the invasive procedure of placing arterial catheters for sampling arterial blood, partial pressure of end-tidal CO 2 (P etco 2 ) has been used as a noninvasive method to estimate Pa co 2 in young, healthy adults at rest and during exercise. [1][2][3][4] These studies have concluded that, although P etco 2 may slightly underestimate Pa co 2 at rest, P etco 2 is a good index of Pa co 2 during resting conditions. During exercise, the instantaneous P aco 2 fl uctuates cyclically with breathing, 5 and the P etco 2 is higher than the average P aco 2 over the complete breathing cycle. 6 Therefore, P etco 2 may overestimate Pa co 2 during exercise, when CO 2 production, ventilation, and tidal volume (V t ) are all increased. 7 To circumvent this problem, Jones et al 3 developed a regression equation to predict Pa co 2 from P etco 2 (P jco 2 ) and V t that corrects for the overestimation of Pa co 2 by P etco 2 :J 2 E T 2 T P CO 5.5 0.9 P CO 2.1 V (Equation 1) where V t is in liters.Background: Obesity affects lung function and gas exchange and imposes mechanical ventilatory limitations during exercise that could disrupt the predictability of Pa CO 2 from end-tidal P CO 2 (P ETCO 2 ), an important clinical tool for assessing gas exchange effi ciency during exercise testing. Pa CO 2 has been estimated during exercise with good accuracy in normal-weight individuals by using a correction equation developed by Jones and colleagues (P JCO 2 5 5.5 1 0.9 3 P ETCO 2 -2.1 3 tidal volume). The purpose of this project was to determine the accuracy of Pa CO 2 estimations from P ETCO 2 and P JCO 2 values at rest and at submaximal and peak exercise in morbidly obese adults. Methods: Pa CO 2 and P ETCO 2 values from 37 obese adults (22 women, 15 men; age, 39 Ϯ 9 y; BMI, 49 Ϯ 7; [mean Ϯ SD]) were evaluated. Subjects underwent ramped cardiopulmonary exercise testing to volitional exhaustion. P ETCO 2 was determined from expired gases simultaneously with temperature-corrected arterial blood gases (radial arterial catheter) at rest, every minute during exercise, and at peak exercise. Data were analyzed using paired t tests. Results: P ETCO 2 was not signifi cantly different from Pa CO 2 at rest (P ETCO 2 5 37 Ϯ 3 mm Hg vs Pa CO 2 5 38 Ϯ 3 mm Hg, P 5 .14). However, during exercise, P ETCO 2 was signifi cantly higher than Pa CO 2 (submaximal: 42 Ϯ 4 vs 40 Ϯ 3, P , .001; peak: 40 Ϯ 4 vs 37 Ϯ 4, P , .001, respectively). Jones' equation successfully corrected P ETCO 2 , such that P JCO 2 was not signifi cantly different from Pa CO 2 (submax: P JCO 2 5 40 Ϯ 3, P 5 .650; peak: 37 Ϯ 4, P 5 .065). Conclusion: P JCO 2 provides a better estimate of Pa CO 2 than P ETCO 2 during submaximal exercise and at peak exercise, whereas at rest both yield reasonable estimates in morbidly obese individuals. Clinicians and physiologists can obtain accurate estimations ...

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Section: Arterial Catheterizationmentioning

confidence: 99%

“…Other data from this study have been published previously that addressed the sex differences in alveolar-to-arterial oxygen pressure tension. 16 …”

mentioning

confidence: 99%

Corrected End-Tidal PCO2 Accurately Estimates PaCO2 at Rest and During Exercise in Morbidly Obese Adults

Pouwels

Wit

Teijink

et al. 2013

Chest

Self Cite

116

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“…[1][2][3] In contrast, evidence suggests that subjects with extreme obesity (BMI 40 kg/m 2 ) maintain PaCO2 from rest to peak exercise. 4,5 A PaCO2 35.0 mmHg during strenuous exercise suggests poor compensatory exercise hyperventilation, and PaCO2 38.0 mmHg suggests absence of a complete hyperventilatory response. 6 Of course, those definitions suggest that hyperventilation during exercise is only "compensatory" if it is necessary to prevent decreases in arterial oxygen pressure (PaO2).…”

mentioning

confidence: 99%

“…[1][2][3] About 75% of individuals with extreme obesity have a PaCO2 35.0 mmHg at peak exercise despite arterial plasma lactate (a breathing stimulant) levels of 8.0 mmol/L. 4 This demonstrates that most individuals with extreme obesity have a "poor breathing response" to strenuous, near maximal exercise that is likely mechanical in nature.…”

mentioning

confidence: 99%

“…The objective of this study was to examine if and how a second bout of intense exercise affects arterial blood-gas status in subjects with extreme obesity. We hypothesized that PaCO2 in extremely obese individuals would not change during a second exercise bout 40 minutes later because extremely obese individuals show a limited reduction in PaCO2 from rest to maximum exercise, 4,5 which is mostly mechanical in nature.…”

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Prior intense exercise reduces arterial carbon dioxide pressure in extreme obesity

Zavorsky

Kim²,

Cass³

et al. 2010

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Clin Invest Med 2010; 33 (5): E321-E334. AbstractPurpose: Unlike normal weight individuals, individuals with extreme obesity do not show a decrease in arterial carbon dioxide pressure (PaCO2) from rest to peak exercise. This indicates that breathing is compromised. The objective of this study was to determine if prior high intensity exercise lowers PaCO2 in comparison with a first bout, normalized for the same metabolic rate. Methods: Oxygen consumption during incremental, ramped exercise was matched to constant workload exercise (75% of peak power). Both protocols were to volitional exhaustion 39 ± 8 min apart. Eleven obese subjects (BMI = 47 ± 8 kg/m 2 , aerobic capacity = 2.3 ± 0.6 L/min) were evaluated. Forty paired samples were obtained at the same metabolic rate between the two protocols. Results: The mean absolute difference and 95% CI were large for arterial oxygen pressure (PaO2) = 9 (6, 11) mmHg and alveolar to arterial oxygen pressure difference (Aa-DO2) = 7 (5, 8) mmHg. The mean absolute difference for arterial oxyhemoglobin saturation (%SaO2) = 0.5 (0.4, 0.7) %; PaCO2 = 4 (3, 4) mmHg; physiological dead space to tidal volume ratio (VD/VT) = 0.04 (0.03, 0.05); and alveolar ventilation (VA) = 3 (2, 4) L/min. The recovery period after the first bout of exercise reduced the PaCO2 by 3 mmHg when matched for similar metabolic rates. Constant workload exercise predicted VA, %SaO2, VD/VT, and PaCO2, but not PaO2 or AaDO2 during incremental exercise at similar metabolic rates. Conclusion: Given a sufficient chemical stimulus, obese subjects will attempt to breathe more, although this does not mean more VA, which removes CO2.In normal-weight individuals (Body mass index or BMI = 18.5 to 24.9 kg/m 2 ), arterial carbon dioxide pressure (PaCO2) usually decreases from rest to peak exercise. The drop in PaCO2 is about 5 to 6 mmHg (from a resting value of 38 -40 mmHg to a peak exercise value of 34 mmHg). [1][2][3] In contrast, evidence suggests that subjects with extreme obesity (BMI 40 kg/m 2 ) maintain PaCO2 from rest to peak exercise. 4,5 A PaCO2 35.0 mmHg during strenuous exercise suggests poor compensatory exercise hyperventilation, and PaCO2 38.0 mmHg suggests absence of a complete hyperventilatory response. 6 Of course, those definitions suggest that hyperventilation during exercise is only "compensatory" if it is necessary to prevent decreases in arterial oxygen pressure (PaO2). If PaCO2 does not decrease between rest and peak exer-ORIGINAL RESEARCH

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Sex and Gender Differences in Endocrinology

Kautzky‐Willer

2011

Sex and Gender Aspects in Clinical Medicine

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Preoperative Gender Differences in Pulmonary Gas Exchange in Morbidly Obese Subjects

Cited by 23 publications

References 45 publications

Corrected End-Tidal PCO2 Accurately Estimates PaCO2 at Rest and During Exercise in Morbidly Obese Adults

Corrected End-Tidal PCO2 Accurately Estimates PaCO2 at Rest and During Exercise in Morbidly Obese Adults

Prior intense exercise reduces arterial carbon dioxide pressure in extreme obesity

Sex and Gender Differences in Endocrinology

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