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PubMed2004

Intracerebroventricular administration of the angiotensin II receptor antagonist saralasin reduces respiratory rate and tidal volume variability in freely moving Wistar rats.

The possible importance of intra-individual variations in respiratory rate and tidal volume has recently gained interest in psychiatric research, as a result of the observations that patients with panic disorder or premenstrual dysphoric disorder display enhanced respiratory variability as compared to controls. Although the role of brain neurotransmitters in the regulation of breathing has been extensively studied, as yet data on the central regulation of respiratory variability is sparse. Prompted by previous studies indicating that angiotensin II (ANG II) may influence ventilation as well as anxiety, we have studied the effect of intracerebroventricular administration of an ANG II receptor antagonist, saralasin, on respiratory variability in unrestrained, freely moving male Wistar rats. Treatment with saralasin, 5 mug dissolved in 1 mul saline followed by 9 mul saline in each lateral cerebral ventricle, did not influence tidal volume, but markedly reduced tidal volume variability (p=0.0005), as compared to saline injections (10 mul). Respiratory rate was reduced by saralasin (p=0.02), and there was also a non-significant tendency for a reduction in respiratory rate variability. Both minute volume (p=0.005) and volume/10 s variability (p=0.0006) were reduced. It is suggested that ANG II in the brain of Wistar rats may regulate respiratory rate and tidal volume variability.

Angiotensin Receptor Antagonists↗

PubMedDate not supplied

Effect of lung, liver, and kidney toxicants on respiratory rate in the mouse.

The intraperitoneal administration of either butylated hydroxytoluene (BHT) +/- thoracic X-irradiation, or cyclophosphamide, and intravenous injection of oleic acid, resulted in lung injury and repair in BALB/c mice which could be assessed in unanesthetized animals by changes in respiratory rate (RR) using a total body plethysmograph. Studies with BHT +/- X-rays, and cyclophosphamide found that the RR right before sacrifice (2 weeks after BHT and 3 weeks after cyclophosphamide) correlated well (r = 0.19) with the degree of pulmonary fibrosis as measured by changes in hydroxyproline content. However, prior to this timepoint, there was a peak and trough in respiratory rate response that could not be correlated with the time course of fibrosis development in the BHT-X-ray model. In an effort to determine the influence of pulmonary edema and lung cell proliferation on respiratory rate changes, an agent (oleic acid) capable of producing lung injury followed by a high level of cellular proliferation with only minimal development of fibrosis was studied. These studies showed that good correlations were found on day 3 following injection (day of peak increase in respiratory rate) between respiratory rate and either lung wet weight (r = 0.81) or the degree of cellular proliferation as measured by the incorporation of thymidine into pulmonary DNA (r = 0.80). Liver (carbon tetrachloride) and kidney (mercuric chloride) toxicants, and starvation produced decreases or no change in RR.

Animals↗

PubMedDate not supplied

A fuzzy approach to the rate control in an artificial cardiac pacemaker regulated by respiratory rate and temperature: a preliminary report.

Fuzzy theory was applied to the rate control of a cardiac pacemaker which uses two parameters, respiratory rate and temperature, as the parameters for rate regulation. Using 25 fuzzy reasoning rules derived from five mongrel dogs, the pacing rates in three animals were calculated and compared with the intrinsic heart rates. It is concluded that the fuzzy method is well suited for the rate determination of a multi-parameter rate-responsive cardiac pacemaker.

Algorithms↗

PubMed2004

Changes in transcutaneous carbon dioxide, oxygen saturation, and respiratory rate after interscalene block.

BACKGROUND: We used transcutaneous (TC) carbon dioxide (CO2) monitoring to prospectively evaluate changes in respiratory status after interscalene anesthesia in 45 adults (40 successful and 5 unsuccessful blocks). METHODS: TC-CO2 oxygen saturation and respiratory rate were recorded every minute for 5 minutes before block and every 2 minutes for a total of 30 minutes (15 data sets) after injection of the local anesthetic solution. RESULTS: After successful block, TC-CO2 increased from 41 +/- 5 mm Hg to a maximum value of 44 +/- 6 mm Hg (P < 0.0001) and the respiratory rate increased from 14 +/- 2 breaths/min to a maximum of 20 +/- 4 breaths/min (P < 0.001). The increase in TC-CO2 was > or = 5 mm Hg in 11 patients and > or = 10 mm Hg in 4 patients, with a maximum increase of 12 mm Hg. Of the 600 TC-CO2 data points recorded (15 each from the 40 patients with a successful block), 62 (10.3%) showed a TC-CO2 value of 50 mm Hg or greater, with a maximum value of 57 mm Hg. No significant change in TC-CO2 or respiratory rate was seen in the five patients with unsuccessful block. CONCLUSION: After interscalene blockade, we found an increase in respiratory rate and hypercarbia that resulted in no clinically significant effect.

Amides↗

PubMed1980

Rapid action of glucagon on hepatic mitochondrial calcium metabolism and respiratory rates.

The time course for the effects of acute, in vivo glucagon treatment on energy-linked functions of isolated hepatic mitochondria has been studied. After 1 min of glucagon treatment, two changes are observed in mitochondrial function. State 4 (nonphosphorylating) respiratory rates with L-glutamate as substrate are decreased. No significant change is observed in the State 4 respiratory rates with succinate as substrate at 1 min of treatment. Concurrent with the change in nonphosphorylating respiratory rates is a decrease in the half time of spontaneous calcium release from mitochondria preloaded with calcium in a phosphate-containing medium. After 2-4 min of treatment, the previously reported stimulations in rates of State 3 (phosphorylating) respiration and calcium influx into mitochondria are observed. After approximately 6 min of treatment, these changes have reached their maxima. The combined effects of increased calcium uptake rate and decreased calcium efflux rate leads to a decrease in the calcium cycling rate of mitochondria. This decrease in the cycling rate should lead to the increased efficiency of mitochondrial energy transduction and may be responsible, in part, for the increased functional capability of mitochondria isolated from glucagon-treated animals. A correlate of the reduced cycling rate is a decrease in the steady-state concentration at which the mitochondria can buffer the calcium concentration of the incubation medium. The changes observed in calcium efflux rates and respiratory rates exhibit a time course consistent with possible intermediates in the glucagon-induced stimulation of hepatic gluconeogenesis.

Animals↗

PubMedDate not supplied

The non-contact monitoring of heart and respiratory rates using laser irradiation: an experimental simultaneous monitoring with and without clothes during biochemical hazards.

The purpose of this study is to develop a non-contact method to evaluate the heart and respiratory rates simultaneously using a single optical sensor which can be used without the removal of clothes before a decontamination procedure in biochemical hazards. We measured the heart and respiratory rates with and without clothes to assess the vital sign monitoring before decontamination. In order to monitor the heart and respiratory rates of rabbits simultaneously, the respiratory and cardiac peaks were separated using fast Fourier transform from a 5 mW helium-neon laser (wavelength 632.8 nm) reflected off the chest walls of rabbits. A cloth (50 mm x 50 mm, 2 mm thick) was placed on the chest of the rabbits to simulate the vital sign monitoring with clothes. The heart rate measured using this method agreed with the rate derived from an electrocardiogram (r = 0.82, p<0.05). The respiratory rate correlated with the manually measured respirator rate (r = 0.93, p<0.05). This method appears promising as a non-contact method for monitoring the heart and respiratory rates of patients under biochemically hazardous conditions.

Animals↗

PubMed1991

Respiratory rate: measurement of variability over time and accuracy at different counting periods.

The respiratory rates/minute of 97 children were monitored every 10-15 minutes over one hour, by an observer and by pneumogram, at which times two 30 second and one 60 second counts were obtained. The children were under 5 years of age with lower respiratory tract infections (n = 20), upper respiratory tract infections (n = 34), or controls without acute respiratory infection (n = 43). The difference between respiratory rate count determined simultaneously by observation and pneumogram in relation to their mean count was analysed for the 60 second counting period, 30 plus 30 second period, and the 30 second period doubled. The mean difference for the 60 second period was 1.79, for the 30 plus 30 second period 1.42, and for the 30 second period doubled 1.72. The variability between respiratory rate counts determined by observation and pneumogram was significantly lower in counts obtained when the subject was sleeping and higher when agitated compared with obtaining a count when the subject was awake and calm or feeding. The variability was also significantly lower in subjects with lower respiratory tract infections compared with those with upper respiratory tract infections and control subjects without respiratory symptoms. In the same patient, over the one hour, 50% of the 60 second counts varied by up to 14 breaths/minute and 75% by up to 21 breaths/minute. The least variability was seen in children with a lower respiratory tract infection, who tended to maintain their rapid breathing in contrast to those with an upper respiratory tract infection and controls without respiratory symptoms. About 10% of initial 30 second counts, 12% of 60 second, and 16% of initial and repeat 30 second attempts to obtain accurate counts failed. Failures occurred more frequently in children <2 months of age and those agitated. The data from this study suggest that one minute's counting either at a stretch or in two blocks of 30 second intervals is better than counting the respiratory rate for 30 seconds, when the child is either awake and calm or when asleep.

Child, Preschool↗

PubMed1998

Sleep, respiratory rate, and growth hormone in chronic neonatal lung disease.

This study assessed whether respiratory rates (RRs) correlate with urinary growth hormone (U-GH) excretion and sleep architecture in infants with chronic neonatal lung disease (CNLD) in early (1 month), middle (6 months), and late (10 months) infancy. Twenty-three preterm infants (CNLD=16, controls=7) were studied on 51 occasions. CNLD infants were stratified according to mean non-REM sleep respiratory rate (NREM RR) in early infancy into "High RR CNLD" infants (mean NREM RR >2 SD higher than controls) and "Normal RR CNLD" infants (mean NREM RR within 2 SD of controls' mean). "High RR CNLD" infants (RR >45) had a lower mean birthweight (P=0.015), current weight (P=0.042), current length (P=0.02), and growth velocity in early infancy (grams/week gained: P=0.042) than "Normal RR CNLD" and control infants. Mean (95% CI) U-GH excretion (ng U-GH/g urinary creatinine) was higher in "High RR CNLD" infants in air or their usual O2 (1,932 [459, 3,406]) than "Normal RR CNLD" (394 [147, 642]) and controls (320 [147, 492]) (P=0.024). With resolution of tachypnea by mid-infancy, hemoglobin oxygen saturation (SaO2) >93%, mean growth parameters and U-GH excretion for the "High RR CNLD" group were not significantly different from "Normal RR CNLD" and control groups. CNLD infants demonstrated increased sleep efficiency (P=0.016), whereas controls had similar sleep efficiency between early and middle infancy (P=0.452). Mean percent time in REM sleep (REM%) and slow wave sleep (SWS%) were not significantly different between early and middle infancy and did not vary in relation to respiratory rate. We conclude that tachypneic infants with CNLD have slower growth and elevated U-GH excretion in early infancy. With resolution of tachypnea, growth improved, U-GH excretion decreased, and sleep consolidation occurred. An elevated U-GH in tachypneic CNLD infants may reflect stress, compromised nutrition (GH resistance), or a feedback loop involving a direct effect of GH on lung growth and repair.

Bronchopulmonary Dysplasia↗

PubMed1994

Tidal volume and respiratory rate changes during CO2 rebreathing after lung transplantation.

To evaluate the contribution of the respiratory pattern to the ventilatory response after lung transplantation, we studied the changes in minute ventilation, tidal volume, and respiratory rate during CO2 rebreathing in 14 patients with severe obstructive pulmonary disease, and compared them with 10 normal subjects. Seven patients underwent a bilateral lung transplantation and 7 patients had single-lung transplantation. Single-lung transplant recipients increased their respiratory rate by the last postoperative test compared with either preoperative or initial test periods (0.38 +/- 0.13 versus 0.027 +/- 0.24 or 0.12 +/- 0.08 breaths.min-1.mm Hg-1; p < 0.005). Bilateral lung transplant recipients showed a diminished ability to augment their respiratory rate by the last postoperative test compared with either preoperative or initial test periods (0.13 +/- 0.23 versus 0.54 +/- 0.25 or 0.25 +/- 0.29 breaths.min-1.mm Hg-1; p < 0.06). The restored ventilatory response by the fourth postoperative week was due to a statistically significant increase in tidal volume for both single and bilateral lung transplant recipients. This study demonstrates that when lung transplant recipients have an appropriate ventilatory response to CO2 rebreathing, single-lung transplant recipients have a respiratory pattern similar to normal; whereas the bilateral lung transplant recipients show the effects of total pulmonary denervation. We conclude that the preserved ventilatory response in lung transplant recipients is composed of a respiratory pattern that is influenced by the presence or absence of vagal inputs.

Adult↗

PubMed1987

The effect of body position on the respiratory rate of infants with tachypnea.

In neonatal disease states where lung compliance is reduced (e.g., inadequate resorption of fetal lung fluid or, surfactant deficiency) an infant's normally low functional residual capacity (FRC) decreases even further. Tachypnea is an efficient compensatory maneuver for the newborn. We evaluated the effect of different bed and body positions on the increased respiratory rate observed in infants with transient tachypnea of the newborn (TTN), infant respiratory distress syndrome (RDS), and bronchopulmonary dysplasia (BPD). Seventeen infants were studied (TTN, n = 6; RDS, n = 6; BPD, n = 5) in four different positions: supine flat, supine elevated, prone flat, and prone elevated. Respiratory rate and heart rate were evaluated in each position. Analysis of variance for the three patient groups showed a lower respiratory rate when the bed was elevated 20-30 degrees compared to flat (P = 0.0001), in the prone posture compared to supine (P = 0.031), and no significant difference in heart rate. The lowest mean respiratory rate occurred when patients were in the prone elevated position. The significant improvement in tachypnea seen in the prone and elevated positions was likely related to improved FRC resulting from reduced cephalad stress on the diaphragm from the abdomen. Positioning neonatal patients with respiratory insufficiency was a simple and safe therapeutic maneuver with prompt and demonstrable benefit.

Beds↗

PubMed1997

Lower respiratory rates without decreases in oxygen consumption during neonatal synchronized intermittent mandatory ventilation.

OBJECTIVE: We tested the hypothesis that synchronization to patient effort during intermittent mandatory ventilation (SIMV), when compared to conventional unsynchronized intermittent mandatory ventilation (IMV), will decrease energy expenditure, as reflected by decreased oxygen consumption (VO2). DESIGN: We used a four-period crossover design. Each patient was studied over four 30-min continuous time intervals. Patients were randomized to receive initially IMV or SIMV, then crossed over such that each patient was treated twice with each modality. Data were analyzed using an analysis of variance technique. SETTING: Patients were receiving treatment in the newborn intensive care unit of Children's Hospital, St. Paul. PATIENTS: We studied 17 patients, who ranged from 23 to 37 weeks gestation, were < or = 14 days old, and had study weights from 623 to 3015 g. All were mechanically ventilated for hyaline membrane disease. MEASUREMENTS AND RESULTS: We measured and compared VO2, carbon dioxide consumption (VCO2), minute ventilation (VE), total respiratory rate, heart rate, arterial blood pressure, and arterial oxygen saturation (SaO2) values during IMV and SIMV. Total respiratory rate fell significantly during SIMV (73 +/- 26 during IMV, 57 +/- 17 during SIMV, p < 0.01) in spite of no significant change in VO2 (0.6 +/- 0.16% fall in VO2 during SIMV) or VCO2 (4.2 +/- 0.19% increase in VCO2 during SIMV) values. Moreover, there were no significant differences in heart rate, blood pressure, VE, or SaO2 values with either form of therapy. CONCLUSIONS: Though total respiratory rate fell, these data do not support the hypothesis that SIMV significantly reduces respiratory rate by decreasing oxygen consumption and carbon dioxide production during infant mechanical ventilation. Rather, the marked fall in respiratory rate may be due to a more efficient respiratory pattern.

Analysis of Variance↗

PubMed1997

The determinants of respiratory rate during mechanical ventilation.

The independent and interactive effect of feedback related to volume, CO2, inspiratory flow, and arousal state on the regulation of respiratory rate in mechanically ventilated humans is not well characterized. We examined the rate response of eight normal volunteers during both quiet wakefulness and non-rapid-eye-movement (NREM) sleep, while mechanically ventilated through a nasal mask in an assist/control mode with a machine back-up rate of 2 breaths/min. Tidal volume (VT) was set slightly above spontaneous VT and then increased by 0.2 L every 3 min up to 1.8 L or 25 ml/kg. Either an inspiratory flow of 40 L/min or an inspiratory time of 2 s (iso-T(I)) was set, with CO2 added (F(I)CO2 > 0) or F(I)CO2 = 0. Measurements were made during both quiet wakefulness and NREM sleep. We found that as VT increased, the respiratory rate decreased; the rate decline was observed during wakefulness and sleep, and under isocapnic as well as hypocapnic conditions. Increasing inspiratory flow raised the respiratory rate during wakefulness and NREM sleep. During NREM sleep, hypocapnia resulted in wasted ventilator trigger efforts. In summary, both VT and inspiratory flow settings affect the respiratory rate, and depending on state, can affect CO2 homeostasis. Ventilator settings appropriate for wakefulness may cause ventilatory instability during sleep.

Adolescent↗

PubMed1987

Cigarettes, respiratory rate, and the relaxation paradox.

Recent research indicates that individuals differ in their physiological reactions to nicotine, some showing strong increases in heart rate within 1 min of beginning to smoke and others showing little or no heart rate change with smoking. In the present research, monitoring of the respiratory rates of these two types of smokers before, during, and after smoking revealed that the former show an increase in respiratory rate while smoking, whereas the latter show a decrease. It is suggested that these changes in respiratory rate, a relatively easily monitored bodily function, may provide the cues used by smokers for inferring the effect that smoking has on them, that is, stimulating versus relaxing.

Adult↗

PubMed2000

Photoplethysmography for simultaneous recording of heart and respiratory rates in newborn infants.

Ten newborn infants, born at 25-41 wk of gestation and nursed in a neonatal intensive care unit or in a neonatal intermediate care unit, underwent monitoring of heart and respiratory rates with a new technique using an optical sensor, 0-60 d postnatally. The aim of this study was to compare the heart and respiratory rates recorded in infants by photoplethysmography with a probe positioned on three monitoring sites, namely the leg, buttock and interscapular region, with the rates recorded by ECG and transthoracic impedance, respectively. The recordings were compared in order to determine which individual heart beats and respiratory cycles were recorded with one or both relevant techniques. A high degree of association (r =0.99) was found between the respiratory rates recorded by photoplethysmography and by transthoracic impedance. Recordings of heart rates by ECG were also highly associated with the photoplethysmographic rates as measured at two (r = 0.99) of the three monitoring sites. It is concluded that heart and respiratory rates in infants can be monitored satisfactorily by the new method based on photoplethysmography. This method offers the advantage of recording several physiological parameters non-invasively with a single probe during the neonatal period.

Apnea↗

PubMed1993

Respiratory rate predicts cardiopulmonary arrest for internal medicine inpatients.

OBJECTIVE: To assess whether vital sign measurements could identify internal medicine patients at risk for cardiopulmonary arrest. DESIGN: Retrospective case-control study comparing 72 hours of pre-arrest vital sign measurements with 72 hours of vital sign measurements for patients from the same units who did not experience cardiopulmonary arrest. SETTING: Twelve non-intensive care internal medicine units at a large midwestern academic medical center. PATIENTS: Cases included all 59 inpatients who had experienced cardiopulmonary arrest between May 1989 and December 1990; patients who were designated do-not-resuscitate (DNR) or had less than 72 hours of vital sign recordings were excluded. Controls included 91 inpatients without cardiopulmonary arrest who were matched for units and who had 72 hours of vital sign recordings. RESULTS: The occurrence of one or more respiratory rates > 27 breaths per minute over a 72-hour period had a sensitivity of 0.54 and a specificity of 0.83 (odds ratio = 5.56, 95% CL = 2.67-11.49) in predicting cardiopulmonary arrest. Other respiratory rate thresholds were also predictive of arrest. The ability of respiratory rate to predict arrest was stronger in units with high incidences of arrest relative to units with low incidences, for example, in units for the management of gastrointestinal disease (sensitivity = 1.00, specificity = 0.86) and renal disease (sensitivity = 0.69, specificity = 0.87). Respiratory rate remained a significant predictor (p < 0.001) after controlling for patient age and gender. Pulse rate and blood pressure were not predictive of cardiopulmonary arrest. CONCLUSIONS: Using elevated respiratory rates as a signal for focused diagnostic studies and therapeutic interventions in internal medicine patients may be useful in reducing the incidence of subsequent cardiopulmonary arrest, and lowering associated morbidity and mortality.

Adolescent↗

PubMed1991

[Study of influence of respiratory rate to airway resistance in patients with pulmonary emphysema].

Application of the panting method is very difficult for patients with pulmonary emphysema (PE). We attempted to measure airway resistance (Raw) during quiet breathing and changing respiratory rate step by step in patients with PE using a pressure-type body plethysmograph system (BX-82) correcting measured values by temperature and humidity. Influence of the respiratory rate to Raw was studied at 0.5l/sec of inspiratory and expiratory flow. Whenever the respiratory rate was going up, the Raw increased in spite of the increase of the thoracic gas volume. Raw (2Hz) was about one and a half times as high as Raw (quiet breathing). On the other hand, when the respiratory rate was going up, elevation of the peak flow was always able to be recognized. It seemed that the state of the airway varied during the panting method. The Raw measured during 0.5 Hz breathing (nearly quiet breathing) had small variability. Because the airway state during 0.5 Hz breathing was nearly the same as that during quiet breathing, measurement of Raw (0.5Hz) can be regarded as a practical method in patients with PE.

Aged↗

PubMed1990

Respiratory rate and severity of illness in babies under 6 months old.

This paper defines the normal range of respiratory rate in babies under 6 months of age. It was counted by two observers in 1007 babies of whom 709 were seen when presenting to hospital for assessment of an acute illness, and 298 on a random basis at home. Whether they were asleep, content, or crying was recorded and the severity of their illness graded. The diagnosis was also recorded. The mean (SD) for the respiratory rate in babies seen awake was 61 (18) breaths/minute at hospital and 61 (14) breaths/minute at home. The respiratory rate when awake did not correlate with the severity of a baby's illness or the presence of serious lower respiratory tract infections. Sleeping babies had a significantly lower mean rate than awake babies at 42 (12) breaths/minute. Crying babies had a significantly lower mean rate than awake and content babies: 51 (14) breaths/minute compared with 61 (18) breaths/minute.

Acute Disease↗

PubMed1996

Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique.

An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. The cut-off frequency of the respiratory signal filter was selected automatically depending on the heart rate. Using digital filtering techniques, heart and respiratory signals were separated at rest and during exercise. The digital signal processor was employed to realize an adaptive and real-time filtering. The heart rate was calculated by the zero-crossing method and the respiratory rate from the peak interval of the filtered signal. To evaluate the newly developed monitor, an ECG for heart rate and a transthoracic impedance plethysmogram for respiratory rate were monitored simultaneously. To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.

Adult↗