Simultaneous Measurements of Cardiac Output during Rest and Exercise Using the Doppler and Nitrous Oxide Rebreathing Techniques

1983 ◽  
Vol 65 (3) ◽  
pp. 53P-53P ◽  
Author(s):  
V.I. Iyawe ◽  
N. Mehta ◽  
A.R.C. Cummin ◽  
K.B. Saunders
Keyword(s):  
Nitrous Oxide ◽  
Cardiac Output ◽  
Simultaneous Measurements ◽  
Rest And Exercise

Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot

2019 ◽  
Vol 59 (1) ◽  
pp. 160 ◽  
Author(s):  
M. R. Redding ◽  
R. Lewis ◽  
P. R. Shorten
Keyword(s):  
Nitrous Oxide ◽  
Real Time ◽  
Emission Inventory ◽  
N2o Emissions ◽  
Mineral N ◽  
A Value ◽  
Simultaneous Measurements ◽  
Heated Air ◽  
Temperature Contrast ◽  
Ammonia Volatilisation

The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and, subsequently, may form a source of indirect nitrous oxide (N2O) emissions. The present study simultaneously investigated volatilisation and deposition of N at a beef feedlot, semi-continuously over a 129-day period. These data were examined relative to pen manure parameters, management statistics and emission-inventory calculation protocols. Volatilisation measurements were conducted using a single, heated air-sampling inlet, centrally located in a feedlot pen area, with real time concentration analysis via cavity ring-down spectroscopy and backward Lagrangian stochastic (bLS) modelling. Net deposited mineral-N was determined via two transects of soil-deposition traps, with samples collected and re-deployed every 2 weeks. Total volatilised ammonia amounted to 210 tonnes of NH3-N (127 g/animal.day), suggesting that the inventory volatilisation factor probably underestimated volatilisation in this case (inventory, 30% of excreted N; 65 g N volatilised/animal.day; a value of ~60% of excreted N is indicated). Temperature contrast between the manure and air was observed to play a significant role in the rate of emission (R2 = 0.38; 0.46 Kendall’s tau; P < 0.05). Net deposition within 600 m of the pen boundary represented only 1.7% to 3% of volatilised NH4+-N, between 3.6 and 6.7 tonnes N. Beyond this distance, deposition approached background rates (~0.4 kg N/ha.year).

Cardiac output during rest and exercise in desert heat

1979 ◽  
Vol 11 (3) ◽  
pp. 234???238 ◽  
Author(s):  
L. G. MYHRE ◽  
I B ODDERSHEDE ◽  
D. B. DILL ◽  
M. K. YOUSEF
Keyword(s):  
Cardiac Output ◽  
Rest And Exercise

Hemorrhage during Isoflurane–Nitrous Oxide Anesthesia

2004 ◽  
Vol 100 (4) ◽  
pp. 885-893 ◽  
Author(s):  
Claudia Höhne ◽  
Pia Vogler ◽  
Ilka Frerking ◽  
Roland C. E. Francis ◽  
Erik R. Swenson ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Cardiac Output ◽  
Angiotensin Ii ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Hormonal Regulation ◽  
Receptor Blockade ◽  
Angiotensin Ii Receptor ◽  
Oxide Anesthesia

Background The objective of this study was to determine whether endothelin-A receptor blockade (ETAB) impairs hemodynamic and hormonal regulation compared with controls and angiotensin II receptor blockade (AT1B) during hypotensive hemorrhage in dogs under isoflurane-nitrous oxide anesthesia. Methods Six dogs were studied in four protocols: (1) control experiments (controls); (2) ETA blockade using ABT-627 (ETAB); (3) AT1 blockade using losartan (AT1B); and (4) combined AT1B and ETAB (AT1B + ETAB). After a 30-min awake period, isoflurane-nitrous oxide anesthesia was established (1.3 minimum anesthetic concentration). After 60 min of anesthesia, 20 ml blood/kg body weight was withdrawn within 5 min, and the dogs were observed for another hour. Thereafter, the blood was retransfused, and the dogs were observed for a final hour. Results Anesthesia: Cardiac output decreased in all protocols, whereas mean arterial pressure decreased more in AT1B and AT1B + ETAB than in controls and ETAB. Hemorrhage: After 60 min, cardiac output had decreased less in controls than in all other protocols. Mean arterial pressure decreased more during ETAB than in controls, but most severely during AT1B and AT1B + ETAB. Angiotensin II increased further only in controls and ETAB, whereas vasopressin and catecholamines increased similarly in all protocols. Retransfusion: Mean arterial pressure remained below controls in all protocols but was lowest when the AT1 receptor was blocked. Cardiac output fully recovered in all but the ETAB protocol. Conclusions ETAB impairs long-term hemodynamic regulation after hemorrhage and retransfusion during anesthesia despite an activation of vasoconstrictive hormones. This suggests that endothelins have a role in long-term cardiovascular regulation. AT1B impairs both short- and long-term blood pressure regulation during anesthesia and after hemorrhage.

A modified single breath method for estimation of cardiac output in humans at rest and during exercise

1987 ◽  
Vol 72 (4) ◽  
pp. 437-441 ◽  
Author(s):  
Y. M. H. Al-Shamma ◽  
R. Hainsworth ◽  
N. P. Silverton
Keyword(s):  
Cardiac Output ◽  
Normal Subjects ◽  
Random Errors ◽  
O2 Uptake ◽  
Mean Values ◽  
Single Breath ◽  
Expired Gas ◽  
The Mean ◽  
Rest And Exercise ◽  
Single Breath Method

1. This study was undertaken to determine the accuracy of a modification of a single breath method for estimation of cardiac output. The technique incorporated a single rebreathing stage followed by a prolonged expiration. Cardiac output was determined from the O2 uptake and the instantaneous changes in O2 and CO2 in the expired gas during the prolonged expiration. 2. The mean values and the random errors (determined from the differences between pairs of estimates) of cardiac outputs in normal subjects at rest and exercise were 5.42 and ± 0.60 litres/min (2 sd, 60 pairs) and 14.1 and ±1.8 litres/min (40 pairs). 3. Larger random errors were obtained in a group of cardiac patients but, except in hypoxic patients, the mean values obtained by the single breath and the direct (Fick) methods were almost identical. 4. We conclude that our modification of the single breath method is simple to use and sufficiently reliable for use in humans both at rest and during steady states of light exercise.

Simultaneous measurements of cardiac output by thermodilution, esophageal doppler, and electrical impedance in anesthetized patients

1988 ◽  
Vol 2 (5) ◽  
pp. 590-595 ◽  
Author(s):  
Lawrence C. Siegel ◽  
Steven L. Shafer ◽  
Gilbert M. Martinez ◽  
Allen K. Ream ◽  
James C. Scott
Keyword(s):  
Cardiac Output ◽  
Electrical Impedance ◽  
Esophageal Doppler ◽  
Simultaneous Measurements

An open-circuit method for determining lung diffusing capacity during exercise: comparison to rebreathe

2005 ◽  
Vol 99 (5) ◽  
pp. 1985-1991 ◽  
Author(s):  
Eric M. Snyder ◽  
Bruce D. Johnson ◽  
Kenneth C. Beck
Keyword(s):  
Cardiac Output ◽  
Breathing Pattern ◽  
Open Circuit ◽  
Diffusing Capacity ◽  
External Work ◽  
Capillary Recruitment ◽  
Single Breath ◽  
Circuit Technique ◽  
Alveolar Capillary ◽  
Rest And Exercise

To avoid limitations associated with the use of single-breath and rebreathe methods for assessing the lung diffusing capacity for carbon monoxide (DlCO) during exercise, we developed an open-circuit technique. This method does not require rebreathing or alterations in breathing pattern and can be performed with little cognition on the part of the patient. To determine how this technique compared with the traditional rebreathe (DlCO,RB) method, we performed both the open-circuit (DlCO,OC) and the DlCO,RB methods at rest and during exercise (25, 50, and 75% of peak work) in 11 healthy subjects [mean age = 34 yr (SD 11)]. Both DlCO,OC and DlCO,RB increased linearly with cardiac output and external work. There was a good correlation between DlCO,OC and DlCO,RB for rest and exercise (mean of individual r2 = 0.88, overall r2 = 0.69, slope = 0.97). DlCO,OC and DlCO,RB were similar at rest and during exercise [e.g., rest = 27.2 (SD 5.8) vs. 29.3 (SD 5.2), and 75% peak work = 44.0 (SD 7.0) vs. 41.2 ml·min−1·mmHg−1 (SD 6.7) for DlCO,OC vs. DlCO,RB]. The coefficient of variation for repeat measurements of DlCO,OC was 7.9% at rest and averaged 3.9% during exercise. These data suggest that the DlCO,OC method is a reproducible, well-tolerated alternative for determining DlCO, particularly during exercise. The method is linearly associated with cardiac output, suggesting increased alveolar-capillary recruitment, and values were similar to the traditional rebreathe method.

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