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At least 145 records · Page 8Linked to original sources
PubMed2000

Monitoring of respiratory rate in postoperative care using a new photoplethysmographic technique.

OBJECTIVE: Photoplethysmography (PPG) is a non-invasive optical technique that measures variations in skin blood volume and perfusion. The PPG signal contains components that are synchronous with respiratory and cardiac rhythms. We undertook this study to evaluate PPG for monitoring patients' respiratory rate in the postoperative care unit, using a new prototype device. We compared it with the established technique, transthoracic impedance (TTI). METHODS: PPG signals from 16 patients (ASA classes 1-2, mean age 43 years) who were recovering from general anaesthesia after routine operations were recorded continuously for 60 minutes/patient. The respiratory synchronous part of the PPG signal was extracted by using a bandpass filter. Detection of breaths in the filtered PPG signals was done both visually and by using an automated algorithm. In both procedures, the detected breaths were compared with the breaths detected in the TTI reference. RESULTS: A total of 10,661 breaths were recorded, and the mean +/- SD respiratory rate was 12.3 +/- 3.5 breaths/minute. When compared with TTI, the rates of false positive and false negative breaths detected by PPG (visual procedure) were 4.6 +/- 4.5% and 5.8 +/- 6.5%, respectively. When using the algorithm for breath detection from PPG, the rates of false positive and false negative breaths were 11.1 +/- 9.7% and 3.7 +/- 3.8%, respectively, when compared to TTI. Lower respiratory rates increased the occurrence of false-positive breaths that were detected by the PPG using visual identification (p < 0.05). The same tendency was seen with the automated PPG procedure (p < 0.10). CONCLUSIONS: Our results indicate that PPG has the potential to be useful for monitoring respiratory rate in the postoperative period.

Adult↗
PubMed1983

Involvement of alpha- and beta-adrenoreceptors in the central action of norepinephrine on temperature, metabolism, heart and respiratory rates of the conscious primate.

The effect of the central blockade of alpha- and beta-adrenoreceptors on the action of norepinephrine (NE) infused by the intracerebroventricular (ICV) route was examined in the unanesthetized primate. After cannulae for ICV infusion were implanted sterotaxically, each monkey (Macaca fasicularis) was placed in a restraint chair fitted with a transparent dome for measurement of O2 uptake. During an experiment, the following responses were monitored simultaneously on a polygraph: skin and colonic temperatures, heart and respiratory rates, and metabolic rates as reflected by O2 uptake. Following an ICV infusion of 150 micrograms NE, colonic temperature, heart and metabolic rates declined while skin temperature increased and respiratory rate remained unchanged. Pretreatment with ICV phentolamine (100 micrograms), an alpha-adrenoreceptor antagonist, attenuated the changes in temperature, heart and metabolic rates and reduced respiratory rate. Similar ICV infusion of 100 micrograms propranolol, a beta-adrenoreceptor antagonist, tended also to attenuate the responses induced by NE, but overall was much less efficacious than phentolamine. Our results indicate that although catecholaminergic neurons mediate these vital physiological processes principally by central alpha-adrenoreceptors, a substantial beta-adrenoreceptor component also participates in the mechanism responsible for specific functional changes.

Animals↗
PubMed1978

Respiratory rate and ATP content of stria vascularis of guinea pig in vitro.

Stria vascularis from guinea pig cochleae was incubated in vitro to determine its metabolic response to variations in substrate and ion composition of the incubation medium. The respiratory rate at 37 degrees C in a medium containing glucose and pyruvate as substrate was 17.3 +/- 1.33 (SEM, n = 51) microliter O2/mg dry weight-hour. The stria could not maintain constant respiration by relying solely upon endogenous fuel stores. With substrate supplied, the ATP level could be maintained at about 73% of that existing in vivo. Glucose appears to be an adequate substrate for stria in vitro since glutamate, pyruvate, and fumarate did not increase the respiratory rate. Succinate increased respiration markedly but did not increase the ATP level. Ouabain (10(-4) M) caused a 48% decrease in the respiratory rate. Incubation in Na+-free and K"-free medium, each resulted in irreversible decrease of respiratory rate comparable to (or greater than) that caused by ouabain. These data are in accord with the high activity of Na+-K+-ATPase in the stria and the pronounced sensitivity of the endolymphatic potential to ouabain.

Adenosine Triphosphate↗
PubMed1995

Measurement of respiratory rate and timing using a nasal thermocouple.

OBJECTIVE: The aims of this study were to assess aspects of the response of a small thermocouple to temperature change, and to evaluate whether such a thermocouple could be used intermittently to measure respiratory rate and timing by detecting the changes in nasal temperature occurring with breathing. METHODS: The study had three parts. First, three similar, fast-responding thermocouples were immersed repeatedly in warm water. Second, the influence of atmospheric temperature on the signal of a thermocouple placed at different sites within the nasal orifice was studied. The signals produced were continuously displayed and analyzed using a laptop computer to allow evaluation of the thermocouples' response characteristics. Third, simultaneous respiratory recordings were acquired using a nasal thermocouple and a nasal pneumotachograph in 12 teenaged subjects. The respiratory rate and the periods of time taken for inspiration (Ti) and expiration (Te) were calculated and compared. RESULTS: The thermocouples' responses to the temperature changes associated with breathing and immersion into water were rapid and consistent. The rate of the signals' decay, following the peak signal marking expiration, was influenced by the atmospheric temperature. The time constants of the thermocouples were similar (mean time constant = 0.41 sec, standard deviation (SD) = 0.07). Optimal respiratory recordings were obtained, with least discomfort, when the thermocouple was positioned at 0 to 4 mm within the nasal orifice. In comparing the respiratory recordings acquired simultaneously with a thermocouple and pneumotachograph, the respiratory rates were identical, and the Ti and Te values were similar (mean difference 0.04 sec (95% CI: -0.11 to 0.21 sec) and -0.04 sec (95% CI: -0.20 to 0.12 sec), respectively). CONCLUSIONS: Intermittent measurements of respiratory rate and timing using a nasal thermocouple accurately reflected measurements obtained from nasal airflow using a pneumotachograph.

Adolescent↗
PubMed2002

Nebulized fentanyl citrate improves patients' perception of breathing, respiratory rate, and oxygen saturation in dyspnea.

Dyspnea, a subjective symptom of impaired breathing, occurs in 70% of terminally ill cancer patients. Current treatments are suboptimal and little is known about the patient's perception of effect. We tested nebulized inhaled fentanyl citrate on patient perceptions, respiratory rate, and oxygen saturation. The study was conducted using a convenience sample of 35 cancer patients on a dedicated oncology unit. We assessed patient perception (did breathing stay the same, worsen, or improve), respiratory rate, and oxygen saturation by pulse oximetry at baseline, 5 minutes, and 60 minutes. Twenty-six of 32 (81%) patients reported improvement in breathing, 3 (9%) were unsure, and 3 (9%) reported no improvement. Oxygen saturation improved from 94.6% at baseline to 96.8% at 5 minutes and 96.7% at 60 minutes (P = 0.0069 compared to baseline). Respiratory rates improved from a baseline of 28.4/min to 25.9/min at 5 minutes and 24.1/min at 60 minutes (P = 0.0251 compared to baseline). No side effects were observed. Inhaled nebulized fentanyl citrate significantly improved patient perception of breathing, respiratory rate, and oxygen saturation. This inexpensive and readily available treatment may offer substantial relief of end-of-life dyspnea. Randomized trials, dose, and length of effect trials are underway.

Administration, Inhalation↗
PubMed2001

Respiratory rate as a predictor of positive lung aspirates in young Gambian children with lobar pneumonia.

Clinical predictors of a positive bacterial culture from lung aspirate or blood culture were investigated in 90 children under 5 years of age with lobar pneumonia on whom both lung aspiration and blood culture were performed. Of the 66 children with a respiratory rate of > or = 50 breaths/min, 35 (53%) had positive bacterial lung aspirates compared with only five (21.7%) of 23 children with a respiratory rate of < 50 breaths/min (odds ratio [OR] 4.06, 95% confidence interval [CI] 1.24-15.46, p = 0.02). Of the 41 children with positive lung aspirates, 31 (76%) had negative blood cultures. In contrast with children with positive lung aspirates, there were no clinical predictors of a positive blood culture. A respiratory rate of > or = 50 breaths/min in children with radiological evidence of lobar pneumonia would support lung aspiration as a positive result is significantly more likely than in children with a lower respiratory rate.

Bacteremia↗
PubMed1999

The PEP transducer: a new way of measuring respiratory rate in the non-intubated patient.

OBJECTIVES: To explore the use of a pyroelectric polymer (PEP) film as a transducer for a simple respiratory rate monitor and to evaluate the transducer in a laboratory situation. METHODS: Laboratory evaluation of a new pyroelectric transducer for measurement of respiratory rate. RESULTS: The amplified output from the pyroelectric film produced an excellent respiratory trace when used on a normal spontaneously breathing subject. The transducer is cheap, robust, and reliable. CONCLUSIONS: PEP films have the potential to be used as cheap and effective transducers in respiratory rate monitors for non-intubated patients. In the laboratory, they have many desirable characteristics which should now be evaluated in a clinical setting.

Evaluation Studies as Topic↗
PubMed1997

Does the respiratory rate in sea urchin embryos increase during early development without proliferation of mitochondria?

During early development of the sea urchin, the respiratory rate, enhanced upon fertilization, is maintained up to hatching (pre-hatching period) and then gradually increases to a maximum at the gastrula stage (post-gastrula period). Except for a short duration after fertilization, respiration in embryos is strongly inhibited by CN- and antimycin A. During the whole span of early development, the amounts of proteins, cytochromes and the specific activities of cytochrome c oxidase and reduced nicotinamide adenine dinucleotide (NADH) cytochrome c reductase in mitochondria are practically the same as in unfertilized eggs. A marked augmentation of mitochondrial respiration after hatching probably occurs without net increase in whole mitochondrial intrinsic capacities. Carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP) or tetramethyl p-phenylenediamine (TMPD) enhances the respiratory rate in the pre-hatching period but hardly augments the respiration in the post-gastrula period. In the presence of both FCCP and TMPD, the respiratory rate in the pre-hatching period was as high as in the post-gastrula period. Probably, electron transport in the mitochondrial respiratory chain is regulated by acceptor control and limitation of cytochrome c reduction in the pre-hatching period and released from those regulations in the post-gastrula period. Acceptor control of respiration is experimentally reproduced in isolated mitochondria by making adenine nucleotide levels as those levels in the pre-hatching period.

Animals↗
PubMed2002

Changes in hepatic and renal enzyme concentrations and heart and respiratory rates in new zealand white rabbits after anesthetic treatments.

To assess the response of hepatic and renal biochemical parameters and heart and respiratory rates to anesthesia, we allocated 30 New Zealand White rabbits to three treatment groups (n = 10 each) which received intravenous (i.v.) saline or ketamine (10 mg/kg i.v.) with either xylazine (3 mg/kg i.v.) or diazepam (2 mg/kg i.v.). Blood samples were obtained from the central ear artery before injection and at 10, 30, 60, and 120 min and 24 h after injection. Plasma alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma glutamiltransferase, blood urea nitrogen, and creatinine levels were measured by using an autoanalyzer. The administration of ketamine-xylazine or ketamine-diazepam significantly increased plasma alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, and creatinine levels, although most parameters remained within the normal range for the species. Respiratory rate significantly decreased in both anesthetized groups whereas heart rate significantly decreased after ketamine-xylazine administration. We concluded that both ketamine-xylazine and ketamine-diazepam induced changes in hepatic and renal biochemical parameters and heart and respiratory rates. Therefore, these changes should be taken into account during the interpretation of experimental results obtained from animals under general anesthesia because the effect of anesthetics may lead to erroneous conclusions.

Adjuvants, Anesthesia↗
PubMedDate not supplied

Evaluation of peak inspiratory pressure, tidal volume and respiratory rate during ventilation of premature lambs using a self-inflating bag.

OBJECTIVE: To evaluate the peak inspiratory pressure, tidal volume and respiratory rate achieved during manual ventilation of premature lambs, using a self-inflating bag. METHODS: In this descriptive, experimental study, five pairs of physicians, selected at random among 35 neonatologists working at a neonatal intensive care unit and with experience in the resuscitation of newborn infants, ventilated five intubated premature lambs using a self-inflating bag. Pressure and flow monitor signals were passed through a transducer and digitized for recording and analysis. Tidal volume and pressure curves were obtained from the integral of flow rate, at peak, during the last 50 seconds of every fifth minute, and analyzed. RESULTS: Median pressure was 39.8 (IQ(25-75%) 30.2-47.2) cmH(2)O; being below 20 in 1.1% of cases and above 40 in 49.1%. Seven out of 10 physicians produced more than six pressure peaks of over 40 cmH(2)O. Median tidal volume/kg was 17.8 (IQ(25-75%) 14.1-22.4) mL, being below 5 mL in 0.1% of cases and greater than or equal to 20 mL in 37.7%. All of the physicians propelled five or more ventilation cycles with tidal volume/kg of 20 mL or more. Respiratory rate was between 30 and 60 cycles/minute in 65.9% of cases, being below 30 in 6.8% of cases and over 60 in 27.3% of cases. CONCLUSIONS: There was major variation in peak inspiratory pressure and tidal volume/kg values, which were in many cases elevated, attaining levels that habitually cause biotrauma, while respiratory rates were adequate in the majority of cases.

Animals↗
PubMed1982

Renal and cutaneous vasomotor and respiratory rate adjustments to peripheral cold and warm stimuli and to bacterial endotoxin in conscious rabbits.

In conscious rabbits peripheral cold stimuli decreased respiratory rate and increased cutaneous vasomotor tone while simultaneously renal sympathetic nervous discharge decreased. Peripheral warm stimuli produced the reverse pattern of autonomic effector activity. Injection of a bacterial endotoxin at warm ambient temperature elicited a biphasic fever response. Within the first 60 min cutaneous vasomotor tone increased, simultaneously renal sympathetic activity decreased. Therefore, ear skin vessels dilated and renal sympathetic activity increased by about 100%. Respiratory rate remained depressed during both fever phases. Renal blood flow was investigated in a second series of experiments and showed a negative stimulation but only in the first phase of fever. The results show that renal innervation is involved in the typical thermoregulatory autonomic activity pattern by which temperature homeostasis is preserved. The vasomotor patterns of cold and heat stress developing during fever are compatible with the concept of a changed set-point of the body thermostat. The depressed respiratory rate and the lack of the renal vascular response to the increased nervous activity during the second fever phase and their reversal to normal after acetylsalicylate (ASA) indicate the participation of prostaglandins modifying peripheral and central neurotransmitter mechanisms.

Animals↗
PubMed1994

Effect of body position on spontaneous respiratory rate and tidal volume in patients with obesity, abdominal distension and ascites.

BACKGROUND: Nursing textbooks and tradition suggest that the high-Fowler's position is best to optimize diaphragmatic excursion and effective breathing pattern. The optimal position for intubated patients with obesity, ascites or abdominal distention has yet to be determined but is important because weaning trial outcomes may reflect the effect of position rather than weaning trial tolerance. OBJECTIVE: To determine the body position that optimizes breathing pattern (tidal volume and respiratory rate) in spontaneously breathing, intubated patients with a large abdomen. METHODS: Nineteen intubated patients with abdominal distention, ascites or obesity who were on continuous positive airway pressure or the pressure support ventilation mode were studied in the 0 degrees, 45 degrees, 90 degrees and reverse Trendelenburg's at 45 degrees positions for 5 minutes prior to data collection. RESULTS: The RT at 45 degrees position resulted in a significantly larger tidal volume and lower respiratory rate than the 90 degrees position in intubated, spontaneously breathing patients with a large abdomen. The 45 degrees position resulted in a significantly lower respiratory rate than at 90 degrees; however, no difference in tidal volume was demonstrated. DISCUSSION: A high respiratory rate and low tidal volume potentiates atelectasis and ultimately failure to wean. It is important that the effect of positioning on breathing pattern in intubated patients be determined so that care planning results in optimal outcomes. CONCLUSIONS: The results of this study have implications for the selection of chair and bed positioning during weaning trials.

Adult↗
PubMed1986

Strain difference in the effects of morphine on the rectal temperature and respiratory rate in male mice.

Effects of morphine on the rectal temperature and respiratory rate, and [3H]naloxone binding to brain membranes from seven brain regions were compared among six strains of male mice, including DBA/2N, C57BL/6N, BALB/c, C3H/HeN, A/J and ICR. The administration of 10 and 20 mg/kg doses of morphine HCl to these strains of mice decreased rectal temperature and respiratory rate. However, there was a significant strain difference in these two measures of the effect of morphine. The DBA/2N strain was the most sensitive in both measures of morphine action. The magnitude of hypothermia was positively correlated with respiratory depression among six strains of mice after the administration of 10 and 20 mg/kg morphine HCl, suggesting common mechanisms. Strain difference in naloxone binding in the brain regions could not explain that of the morphine responses, because there was no correlation between the intensity of morphine-induced hypothermia or respiratory depression and the regional [3H]naloxone binding for the mouse strains.

Animals↗
PubMed1996

Optical aspects of a fibre-optic sensor for respiratory rate monitoring.

A new sensor for respiratory rate monitoring is described. The sensor uses an optical fibre that detects the evaporated humidity from the mouth and/or nose at each exhalation. The condensed humidity substantially alters the coupling of light from the optical fibre to the surrounding medium, which can be monitored by a photo-detector. The sensing principle is evaluated using ray-tracing simulation and scattering measurements.

Computer Simulation↗
PubMed1988

The effects of n-butanol vapour on respiratory rate and tidal volume.

Exposure to n-butanol vapour gave rise to a sensory irritation response which was measured by the reflexively induced decrease in respiratory rate in mice according to the American standard method (E981-84). The response reached maximum within the 1st min of exposure. In this period the expected threshold response (RD-0) and the concentration expected to depress the respiratory rate by 50% (RD-50) were extrapolated to be 233 ppm and 11,696 ppm, respectively. The response followed the dynamics of a bimolecular reaction between butanol and the sensory irritant receptor. For concentrations below 3000 ppm, the response faded due to desensitization. However, concentrations above 3000 ppm gave rise to a new decrease in respiratory rate due to activation of lung receptors. Two types of lung receptors, probably J-receptors and stretch receptors, were involved. The sensory irritation response measured by the standard method gave a threshold response which was comparable to that found by electrophysiological experiments in rats. The irritation response in man as well as the maximum allowable concentration in the working environment were adequately predicted from the sensory irritation response in mice.

1-Butanol↗
PubMed1999

Evaluation of a new fibre-optical monitor for respiratory rate monitoring.

OBJECTIVES: To present further development of a fibre-optical respiratory rate monitor and evaluate the function in the final version. METHODS: Respiration was recorded in 18 healthy volunteers of ages 9-83 years by three different methods simultaneously: fibre-optical monitoring, capnography and manually. The recordings were made-breath by breath in four 3-minute periods in each subject. In total there were 54 observations, corresponding to 648 minutes. The recordings were fed simultaneously into a computer. Two subjects were excluded because of pronounced differences between all three methods. One person was later diagnosed as having a nasal septum deviation. Recordings with any kind of technical problem were also excluded. RESULTS: In total 516 minutes were analysed. Students' paired t-test showed a mean of 0.5 and 0.3 more breaths were recorded by fibre-optical monitor compared with the manual method and capnography respectively. The 95% confidence interval of the differences between the fibre-optical monitor and the other two methods was -0.5 to +1.5 when the mean respiratory frequency was 14 breaths per minute. Analysis of variance revealed that the fibre-optical monitor tended to overestimate the mean respiratory rate (p < 0.001). CONCLUSION: The fibre-optical monitor has sufficient accuracy for clinical monitoring. It is easy to use and inexpensive. Combinations with pulse oximetry seem attractive, to use especially for application outside "high tech areas," for example when respiratory depressant drugs are used or in ambulances.

Adolescent↗
PubMed1991

Body temperature and respiratory rate of lactating dairy cattle under field and chamber conditions.

A coordinated field and chamber experiment assessed breed, sire, and cow differences in body temperatures and respiratory rates. During each of 4 yr, 10 lactating Ayrshire, Guernsey, Holstein, and Jersey cows, 40 animals per yr, were observed in the field on 10 d when the air temperature approached 32 degrees C. For the first 3 yr, each cow also was exposed in a controlled atmospheric chamber at 40 degrees C and 34 mm Hg vapor pressure. Significant breed differences were found for body temperature and respiratory rate. The order of tolerance to hot conditions was Jersey, Guernsey, Ayrshire, and Holstein both in the field and chamber. Significant sire differences, interpreted as genetic, were found for the field measures but not in the chamber. Repeatability of individual field observations for a cow on different days in a year ranged from .38 to .55. Correlations between the average of 10 observations for a cow in the field during a year and the chamber evaluation were positive but lower than the repeatability values. Correlations of ambient temperature with body temperatures and respiratory rates were highest; those for radiation were next, followed by vapor pressure and air movement.

Analysis of Variance↗