Rebreathing techniques for pulmonary capillary blood flow and tissue volume

Sackner, Marvin A.; Markwell, G.; Atkins, Neal; Birch, Stephen; Fernandez, Robert

doi:10.1152/jappl.1980.49.5.910

Cited by 49 publications

(35 citation statements)

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“…Pulmonary tissue volume was calculated from gas fractions during rebreathing as the difference between distribution space for a water-soluble gas (freon) and a water-insoluble gas (neon) (9). Coefficient of variation in 12 measurements on separate days of pulmonary tissue volume in a normal subject was 7% in the supine position.…”

Section: Methodsmentioning

confidence: 99%

Hemodynamics in diabetic orthostatic hypotension.

Hilsted¹,

Parving²,

Christensen³

et al. 1981

J. Clin. Invest.

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A B S T R A C T Hemodynamic variables (blood pressure, cardiac output, heart rate, plasma volume, splanchnic blood flow, and peripheral subcutaneous blood flow) and plasma concentrations of norepinephrine, epinephrine, and renin were measured in the supine position and after 30 min of quiet standing. This was done in normal subjects (n = 7) and in juvenile-onset diabetic patients without neuropathy (n = 8), with slight neuropathy (decreased beat-to-beat variation in heart rate during hyperventilation) (n = 8), and with severe neuropathy including orthostatic hypotension (n = 7). Blood pressure decreased precipitously in the standing position in the diabetics with orthostatic hypotension, whereas moderate decreases were found in the other three groups. Upon standing, heart rate rose and cardiac output and plasma volume decreased similarly in the four groups. The increases in total peripheral resistance, splanchnic vascular resistance and subcutaneous vascular resistance were all significantly lower (P < 0.025) in the patients with orthostatic hypotension compared with the other three groups. The increase in plasma norepinephrine concentrations in the patients with orthostatic hypotension was significantly lower (P < 0.025) than in the patients without neuropathy, whereas plasma renin responses to standing were similar in the four groups. We conclude that in diabetic hypoadrenergic orthostatic hypotension the basic pathophysiological defect is lack of ability to increase vascular resistance, probably due to impaired sympathetic activity in the autonomic nerves innervating resistance vessels; cardiac output and plasma volume responses to standing are similar to those found in normal subjects and in diabetics without neuropathy.

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Section: Methodsmentioning

confidence: 99%

Hemodynamics in diabetic orthostatic hypotension.

Hilsted¹,

Parving²,

Christensen³

et al. 1981

J. Clin. Invest.

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“…Q c measurements were determined by using the Sackner algorithm by fitting a line over all of the alveolar plateau regions from expiration after clearing the deadspace. Q c was calculated (38).…”

Section: Gas Rebreathing: Foreign and Physiological Soluble Gasesmentioning

confidence: 99%

Simultaneous determination of the accuracy and precision of closed-circuit cardiac output rebreathing techniques

Jarvis¹,

Levine²,

Prisk³

et al. 2007

Journal of Applied Physiology

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Simultaneous determination of the accuracy and precision of closed-circuit cardiac output rebreathing techniques. J Appl Physiol 103: [867][868][869][870][871][872][873][874] 2007. First published June 7, 2007; doi:10.1152/japplphysiol.01106.2006.-Foreign and soluble gas rebreathing methods are attractive for determining cardiac output (Q c) because they incur less risk than traditional invasive methods such as direct Fick and thermodilution. We compared simultaneously obtained Q c measurements during rest and exercise to assess the accuracy and precision of several rebreathing methods. Q c measurements were obtained during rest (supine and standing) and stationary cycling (submaximal and maximal) in 13 men and 1 woman (age: 24 Ϯ 7 yr; height: 178 Ϯ 5 cm; weight: 78 Ϯ 13 kg; V O2max: 45.1 Ϯ 9.4 ml⅐kg Ϫ1 ⅐min Ϫ1; mean Ϯ SD) using one-N 2O, four-C2H2, one-CO2 (single-step) rebreathing technique, and two criterion methods (direct Fick and thermodilution). CO 2 rebreathing overestimated Q c compared with the criterion methods (supine: 8.1 Ϯ 2.0 vs. 6.4 Ϯ 1.6 and 7.2 Ϯ 1.2 l/min, respectively; maximal exercise: 27.0 Ϯ 6.0 vs. 24.0 Ϯ 3.9 and 23.3 Ϯ 3.8 l/min). C 2H2 and N2O rebreathing techniques tended to underestimate Q c (range: 6.6 -7.3 l/min for supine rest; range: 16.0 -19.1 l/min for maximal exercise). Bartlett's test indicated variance heterogeneity among the methods (P Ͻ 0.05), where CO 2 rebreathing consistently demonstrated larger variance. At rest, most means from the noninvasive techniques were Ϯ10% of direct Fick and thermodilution. During exercise, all methods fell outside the Ϯ10% range, except for CO 2 rebreathing. Thus the CO2 rebreathing method was accurate over a wider range (rest through maximal exercise), but was less precise. We conclude that foreign gas rebreathing can provide reasonable Q c estimates with fewer repeat trials during resting conditions. During exercise, these methods remain precise but tend to underestimate Q c. Single-step CO 2 rebreathing may be successfully employed over a wider range but with more measurements needed to overcome the larger variability.foreign gas rebreathing; physiological gas rebreathing; direct Fick; thermodilution CARDIAC OUTPUT (Q c ), the volume of blood pumped by the heart each minute, can be measured several ways, both invasively and noninvasively. Each technique has advantages and limitations that may restrict its application during exercise. The direct Fick method has been implemented in humans in clinical environments since 1940 (21); together with the thermodilution method, they are considered "gold standard" Q c techniques. These methods, however, are expensive, require medical expertise, and are invasive, limiting their widespread utility (44). For instance, occasional reported complications associated with these gold standards include arrhythmias and pulmonary artery or right ventricle perforation (30, 40).Rebreathing techniques, employing foreign or physiological tracers, are attractive alternatives because their relative risk is considerably...

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“…Pulmonary tissue volume was calculated from the gas tensions during rebreathing from the difference between the distribution space for a water-soluble gas (freon) and a water-insoluble gas (neon) [9]. Coefficients of variation were 7% (supine rest), 14% (50 W) and 18% (100 W).…”

Section: Me~o~mentioning

confidence: 99%

Haemodynamic changes during graded exercise in patients with diabetic autonomic neuropathy

et al. 1982

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Summary. Haemodynamic variables were measured during supine rest and during ergometer cycle exercise at two work loads (50 W and 100 W) in normal subjects (n = 7), in insulin-dependent diabetic subjects without neuropathy (n --8), in insulin-dependent diabetic subjects with slight autonomic neuropathy (decreased beat-to-beat variation in heart rate, which is considered due to a cardiac parasympathetic defect; n = 8), and in insulin-dependent diabetic subjects with severe autonomic neuropathy, including orthostatic hypotension (n = 7). Compared with normal subjects, cardiac stroke volume was lower in the diabetic subjects with autonomic neuropathy, both at rest and during exercise (p < 0.025), whereas intermediate values were found in the diabetic subjects without neuropathy. The increase in cardiac output in response to exercise was smaller (p < 0.05) in both diabetic groups with autonomic neuropathy compared with the normal and diabetic subjects without autonomic neuropathy. The increase in hepato-splanchnic vascular resistance was smaller in the diabetic subjects with severe autonomic neuropathy than in the normal subjects and the diabetic subjects without autonomic neuropathy (p < 0.025), whereas intermediate values were found in the diabetic subjects with slight autonomic neuropathy. We conclude that, in diabetic patients with severe autonomic neuropathy, the responses of the heart and the splanchnic resistance vessels to exercise are impaired. While sympathetic neuropathy may be responsible for impaired function of splanchnic resistance vessels, both cardiac sympathetic neuropathy and diabetic cardiomyopathy may be involved in the impaired cardiac response to exercise in diabetic subjects with autonomic neuropathy.

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Rebreathing techniques for pulmonary capillary blood flow and tissue volume

Cited by 49 publications

References 0 publications

Hemodynamics in diabetic orthostatic hypotension.

Hemodynamics in diabetic orthostatic hypotension.

Simultaneous determination of the accuracy and precision of closed-circuit cardiac output rebreathing techniques

Haemodynamic changes during graded exercise in patients with diabetic autonomic neuropathy

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