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PubMed1996

A comparison of pulse oximetry and respiratory rate in patient screening.

OBJECTIVE: To examine how well respiratory rate correlates with arterial oxygen saturation status as measured by pulse oximetry, and determine whether respiratory rate measurements detect oxygen desaturation reliably. METHODS: Respiratory rate (RR) and oxygen saturation (SaO2) were measured prospectively on 12,096 consecutive adult emergency department triage patients at a university medical center. Respiratory rate was measured by counting ausculated breath sounds for 1 min. Pulse oximetry was used to measure SaO2. Measurements were analysed by age (with one group for 18-19 year olds, groups for every 10 yr from age 20 to age 60, and groups for every 5 yr for subsequent ages). Pearson correlation coefficients were calculated for each age group as well as the weighted average coefficient. Cases having oxygen saturation below 90% were examined to determine how frequently they exhibited increased RR (increased RRs were defined as any rate in the upper five percentile by age. RESULTS: Correlation coefficients ranged from 0.379 to -0.465 with a weighted mean of -0.160. Coefficients for ages 18 through 70 years (representing 10,740 patients) all had magnitude < 0.252. Overall, only 33% of subjects with oxygen saturation below 90% exhibited increased RR. CONCLUSIONS: Respiratory rate measurements correlate poorly with oxygen saturation measurements and do not screen reliably for desaturation. Patients with low SaO2 do not usually exhibit increased RR. Similarly, increased RR is unlikely to reflect desaturation.

Adolescent↗
PubMed2004

[Effects of different respiratory rates on PaCO2 and plasma potassium concentration].

OBJECTIVE: To observe the effects of different respiration rates on the CO2 partial pressure and plasma potassium concentration during general anesthesia. METHODS: Forty-two surgical patients under general anesthesia with normal preoperative arterial CO2 partial pressure and plasma potassium concentration were randomized into 2 groups. After intubation, all patients were placed on the mechanical ventilator (Ohmeda 210 anesthesia machine) with tidal volume 10 ml/kg and oxygen flow rate 1.5 L/min. Initial respiratory rate of group I patients was set to 12 times per minute for 30 minutes, and then was adjusted according to calculation with 0.3 x PaCO2. Respiratory rate of group II patients was set to 8 times per minute. Blood samples were collected for arterial blood gas analysis preoperatively, and 30 and 60 minutes after intubation. Linear regression was used to analyze the relationship between PaCO2 and plasma with K+ concentration and Student's t test was used to test the differences at different time points. An overall alpha of 0.05 was considered significant for the outcome variables. RESULTS: In two groups, PaCO2 (mmHg) was related with K+ concentration (mmol/L) (P < 0.05) at all time points. 30 minutes after intubation, PaCO2 and K+ concentration significantly decreased (P < 0.05) and recovered to preoperative level after the respiratory rate being adjusted [(to 8.85 +/- 0.73) times/min] for another 30 minutes in group I. No significant difference in respect to PaCO2 and K+ concentration was found between any two time points in group II. CONCLUSION: Traditional ventilation with VT 10 ml/kg and RR 12-15 times/min will probably produce hyperventilation and hypokalemia.

Adult↗
PubMed1982

Raised respiratory rate in elderly patients: a valuable physical sign.

Measurements of respiratory rate in 82 long-stay patients aged 67-101 years yielded a normal range of 16-25 breaths a minute. In a prospective study of 60 consecutive acute admissions to a geriatric unit, 19 out of 21 patients diagnosed as lower respiratory tract infections had respiratory rates above the upper limit of normal on the day of diagnosis; the rise in respiratory rate preceded the clinical diagnosis. All eight patients who were diagnosed on admission as having a lower respiratory tract infection had a respiratory rate greater than 26, with a mean of 29.7 breaths a minute. Patients admitted for other conditions-for example, urinary tract infection-rarely had respiratory rates outside the normal range. Accurate measurement of respiratory rate is a valuable diagnostic aid in elderly patients.

Aged↗
PubMedDate not supplied

Respiratory rate and pattern disturbances in acute brain stem infarction.

Respiratory rates and patterns were studied in 23 patients with acute brain stem infarction using impedance pneumography. Autopsy was obtained in six of eight fatal cases. Pontine lesions were present in all patients, with coexistent infarction of midbrain in four and of medulla in nine. Respiratory rate and pattern abnormalities observed included Cheyne-Stokes respiration, Cheynb-Stokes variant pattern and tachypnea. Abnormalities of respiratory rate and pattern of varying duration were observed at some time in all patients. All patients in whom prominent Cheyne-Stokes respiration or tachypnea were observed had extensive bilateral pontine lesions involving both basal and tegmental portions. However, not all patients with large pontine infarcts had Cheyne-Stokes respiration or tachypnea. Cheyne-Stokes respiration was prominent in four patients (two fatal, two nonfatal). Cheyne-Stokes variant pattern was present frequently in four patients (one fatal, three nonfatal). Sustained tachypnea developed in five patients, four of whom died. In ten patients (one fatal, nine nonfatal), normal respiratory rate and pattern predominated with only rare or occasional apperance of Cheyne-Stokes respiration or Cheyne-Stokes variant pattern, especially during sleep. The types of respiratory rate and pattern abnormalities in acute brain stem infarction were not specifically related to the level of lesions, but rather to the size and bilaterality of the lesions. Respiratory alkalosis was present in varying degrees in most patients with either tachypnea or prominent CSR.

Acute Disease↗
PubMed1983

Determination of the relative involvement of mu-opioid receptors in opioid-induced depression of respiratory rate by use of beta-funaltrexamine.

Using a simple method to measure respiratory rate, it was clearly shown that the depression of respiratory rate caused by morphine, ethylketazocine or [D-Ala2,D-Leu5]enkephalin was not altered by the highly selective, irreversible mu-antagonists, beta-funaltrexamine (beta-FNA) at a dose which produced marked antagonism of morphine antinociception. These results indicated that antinociception and depression of respiratory rate are mediated by different receptor interactions. However using a different method to measure respiratory rate (body plythesmograph), beta-FNA caused substantial antagonism of morphine-induced respiratory depression indicating that the degree to which mu-receptor interactions contribute to the depression of respiratory rate depends on the methodology. Possible explanations for this difference are discussed. It is concluded that careful consideration of the methodology must be given when one measures respiratory rate and caution must be exercised if measurement of rate alone is used to assess opioid-induced respiratory depression.

Analgesics↗
PubMed1994

Presentation and evaluation of a new optical sensor for respiratory rate monitoring.

A new optical sensor for respiratory rate monitoring was simultaneously compared with an acoustic sensor and a transthoracic impedance plethysmograph during normoventilation in the respiratory rate range of 9-17 breaths per minute. The response characteristics of the optical sensor were then measured during simulation of central apnoea and tachypnoea. Visual observation was chosen as the reference method for monitoring the respiratory rate. The measurements were performed in ten healthy volunteers and the respiratory signals recorded on an analogue tape and strip-chart recorder and analysed off-line. The response characteristics of the fibre optic sensor corresponded well with those of the acoustic sensor and impedance plethysmograph. All three methods responded rapidly to an apnoeic event.

Adult↗
PubMed1998

Approximate entropy of respiratory rate and tidal volume during weaning from mechanical ventilation.

OBJECTIVE: To determine the effects of respiratory failure on respiratory rate pattern and tidal volume pattern. DESIGN: Prospective, clinical study. SETTING: Cardiovascular intensive care unit. PATIENTS: Ten patients within 12 hrs of cardiac surgery, and 21 patients who required prolonged (>7 days) mechanical ventilation. INTERVENTIONS: Patients were placed on spontaneous ventilation for weaning trials. MEASUREMENTS AND MAIN RESULTS: During spontaneous ventilation, each breath's instantaneous respiratory rate and tidal volume were recorded for later analysis. Approximate entropy (ApEn) was calculated for respiratory rate and tidal volume series of the terminal 1000 breaths on each spontaneous ventilation trial in series of 100, 300, and 1000 breaths. Ten patients (controls) were studied and extubated within 12 hrs of cardiac surgery. The other 21 patients were studied during attempts to wean them from mechanical ventilation. These patients passed (Group V-Pass) 59 and failed (Group V-Fail) 14 weaning trials. Mean tidal volume did not vary between groups, but respiratory rate increased progressively from the control group to Group V-Pass to Group V-Fail (p < .017). Conversely, approximate entropy of respiratory rate (ApEn-RR) did not vary among the three groups at any time series length, but approximate entropy of tidal volume (ApEn-VT) increased from the control group to Group V-P (p< .017) to Group V-F (p< .017) at all time series lengths. ApEn-VT was very specific but only moderately sensitive at identifying respiratory failure. CONCLUSION: Respiratory failure causes tidal volume patterns to become increasingly irregular, but increasing respiratory rate has no effect on respiratory rate pattern.

Aged↗
PubMed2006

An automated algorithm for determining respiratory rate by photoplethysmogram in children.

BACKGROUND: We have developed an automated algorithm to allow the measurement of respiratory rate directly from the photoplethysmogram (pulse oximeter waveform). AIM: To test the algorithm's ability to determine respiratory rate in children. METHODS: A convenience sample of patients attending a paediatric Accident and Emergency Department was monitored using a purpose-built pulse oximeter and the photoplethysmogram (PPG) recorded. Respiration was also recorded by an observer activating a push-button switch in synchronization with the child's breathing. The switch marker signals were processed to derive a manual respiratory rate that was compared with the wavelet-based oximeter respiratory rate derived from the PPG signal. RESULTS: Photoplethysmograms were obtained from 18 children aged 18 mo to 12 y, breathing spontaneously at rates of 17 to 27 breaths per minute. There was close correspondence between the wavelet-based oximeter respiration rate and the manual respiratory rate, with the difference between them being less than one breath per minute in all children. CONCLUSION: Our automated algorithm allows the accurate determination of respiratory rate from photoplethysmograms of a heterogeneous group of children. We believe that our automated wavelet-based signal-processing techniques could soon be easily incorporated into current pulse oximetry technology.

Algorithms↗
PubMed1996

Heart and respiratory rates and their significance for convective oxygen transport rates in the smallest mammal, the Etruscan shrew Suncus etruscus.

Heart and respiratory rates of the smallest mammal (mean adult body mass 2g), the Etruscan shrew Suncus etruscus, were determined at rest and under stress conditions. Heart rate was obtained from electrocardiograms (ECGs), recorded via foot electrodes. The mean +/- S.D. heart rate of resting animals (ambient temperature 22 degrees C) was 835 +/- 107 min-1, the mean maximal rate amounted to 1093 +/- 235 min-1. The highest single value recorded was 1511 min-1, which is the highest heart rate reported so far for an endotherm. The respiratory rate was also obtained from ECG recordings, which showed the electrical activity of the breathing muscles during inhalation, and additionally by recording the movements of the thoracic wall with a laser autofocus system. The mean resting respiratory rate was 661 +/- 93 min-1, the mean maximal rate was 758 +/- 109 min-1 and the highest single value recorded was 894 min-1. At 22 degrees C, the specific oxygen consumption rate is 67 times higher in resting S. etruscus than in resting humans. Under these conditions, the respiratory rate of the shrew is 47 times higher but the heart rate only 12 times higher than in man. Therefore, to achieve an adequate circulatory oxygen transport rate, the product of relative stroke volume and arterio-venous O2 difference has to be 5.6 times higher in the shrew than in man, whereas for an appropriate ventilatory oxygen transport rate the product of relative tidal volume and oxygen extraction has to be only 1.4 times higher in this small insectivore than in man. The maximal possible oxygen transport rates of the ventilatory and the circulatory system have been estimated and compared with the diffusional transport capacity of the lung. These rates amount to approximately 1000 ml O2 kg-1 min-1. According to our results and data in the literature, an aerobic scope of 7-10 seems to be realistic for the Etruscan shrew.

Animals↗
PubMed1992

[Capnometry in pediatric anesthesia. The effect of the measurement site and respiratory rate].

OBJECTIVE: To evaluate the influences of site of measurement, respiratory rate, and tidal volume on end-tidal PCO2 measurement in children ventilated with a non-rebreathing system. SETTING: Paediatric surgical patients of a university hospital. PATIENTS: Thirty-one children scheduled for major abdominal or urogenital surgery; weight varying between 2.2 and 9.8 kg. INTERVENTIONS AND METHODS: During a relative steady-state situation, end-tidal carbon dioxide partial pressure (PetCO2) was measured at the proximal and distal ends of the endotracheal tube by a sidestream analyser (Datex, Normocap) and between the proximal end of the tube and the Y-piece of the ventilator by a mainstream analyser (Hewlett Packard, HP14265A). PetCO2 was corrected for water vapor and calculated as partial pressure at a barometric pressure of 760 mmHg. At the same time, capillary blood was taken for blood gas analysis. The capillary-end-tidal PCO2 gradient [dPCO2(cap-et)] was computed to compare the three capnometric methods. Statistical analysis was performed with the Friedmann test. Correlations were calculated by means of the least-square fitting method and significance of the correlation was checked with the F-test. RESULTS: dPCO2 (cap-et) did not differ significantly in children with more than 6 kg body weight. In patients less than 6 kg, however, the three capnometric methods revealed significantly different dPCO2 (cap-et) values (P less than 0.01): dPCO2 (cap-et) was 3.0 +/- 4.7 mmHg at the distal end of the endotracheal tube, 5.8 +/- 4.6 mmHg at the proximal end, and 8.7 +/- 4.6 mmHg between the proximal sidestream connector and the Y-piece of the ventilator. There was no correlation between tidal volume and dPCO2 (cap-et) (Fig. 1), however, a significant relation was found between respiratory rate and dPCO2 (cap-et) (Fig. 2) and between respiratory rate and the PCO2 difference between the distal and proximal ends of the endotracheal tube (Fig. 3). CONCLUSIONS: Even in a non-rebreathing system, capnometry is influenced by the site of measurement. In small children with body weight below 6 kg, analysis of an endotracheal sample may provide the best PetCO2 values. In our opinion, dPCO2 (cap-et) in the present investigation was not caused by rebreathing or by pendelluft (a significant correlation between dPCO2 (cap-et) and tidal volume would then have been expected), but was mainly due to ventilation-perfusion mismatch. This may result from high respiratory rates causing inadequate ventilation of lung regions with long time-constants.

Carbon Dioxide↗
PubMed1998

Craniosacral rhythm: reliability and relationships with cardiac and respiratory rates.

Craniosacral rhythm (CSR) has long been the subject of debate, both over its existence and its use as a therapeutic tool in evaluation and treatment. Origins of this rhythm are unknown, and palpatory findings lack scientific support. The purpose of this study was to determine the intra- and inter-examiner reliabilities of the palpation of the rate of the CSR and the relationship between the rate of the CSR and the heart or respiratory rates of subjects and examiners. The rates of the CSR of 40 healthy adults were palpated twice by each of two examiners. The heart and respiratory rates of the examiners and the subjects were recorded while the rates of the subjects' CSR were palpated by the examiners. Intraclass correlation coefficients were calculated to determine the intra- and inter-examiner reliabilities of the palpation. Two multiple regression analyses, one for each examiner, were conducted to analyze the relationships between the rate of the CSR and the heart and respiratory rates of the subjects and the examiners. The intraexaminer reliability coefficients were 0.78 for examiner A and 0.83 for examiner B, and the interexaminer reliability coefficient was 0.22. The result of the multiple regression analysis for examiner A was R = 0.46 and adjusted R2 = 0.12 (p = 0.078) and for examiner B was R = 0.63 and adjusted R2 = 0.32 (p = 0.001). The highest bivariate correlation was found between the CSR and the subject's heart rate (r = 0.30) for examiner A and between the CSR and the examiner's heart rate (r = 0.42) for examiner B. The results indicated that a single examiner may be able to palpate the rate of the CSR consistently, if that is what we truly measured. It is possible that the perception of CSR is illusory. The rate of the CSR palpated by two examiners is not consistent. The results of the regression analysis of one examiner offered no validation to those of the other. It appears that a subject's CSR is not related to the heart or respiratory rates of the subject or the examiner.

Adult↗
PubMed2000

Relationship between ATP level and respiratory rate in sea urchin embryos.

In sea urchin embryos, the rate of respiration, as a result of electron transport through the mitochondrial respiratory chain, was enhanced after hatching without any change in the intrinsic capacity of electron transport in mitochondria. The increase in respiratory rate after hatching was accompanied by an evident decrease in intracellular adenosine triphosphate (ATP) concentration without any change in intracellular levels of adenosine diphosphate (ADP) and adenosine monophosphate (AMP). Adenosine triphosphate is proposed to fortify acceptor control of respiration at high concentrations and to reduce the respiratory rate even in the presence of ADP, the acceptor. The relationships between the respiratory rate and intracellular ATP concentration in embryos were the same as those in mitochondria isolated from embryos, obtained in the presence of ADP at the same concentration as in the embryos. Probably, the respiratory rate is enhanced after hatching because of the decrease in the level of ATP. In embryos kept in a medium containing adenosine, intracellular ATP concentration increased especially after hatching, without any change in the ADP level, and the respiratory rate after hatching was made as low as the rate expected, based on the relationships obtained on isolated mitochondria. The respiratory rate in embryos probably depends on intracellular ATP concentration, irrespective of the developmental stage in early development.

Adenosine Triphosphate↗
PubMed1983

Anaesthetic uptake by the goldfish: effect of respiratory rate.

In order to assess the uptake of halothane by the goldfish, the respiratory rate of six fish was studied when water temperature was varied with and without changes in oxygen or carbon dioxide tension. The effective dose 50 of halothane (ED-50-H) and the time taken to reach it (T-ED-50-H) at an FIO2 of 0.35 in nitrogen, were studied when temperature and CO2 tension were varied. Nomograms were drawn to predict respiratory rate as a function of water CO2 tension, when CO2 was bubbled in air or in oxygen, and with changes in water temperature. At low temperatures (5 degrees C to 7.5 degrees C), respiratory rate remained below 10 per min, irrespective of CO2 partial pressure. At 28 degrees C, a CO2 partial pressure of 8 +/- 0.2 kPa produced a respiratory rate of 125 +/- 3/min in air, and in oxygen unexpectedly 140 +/- 3/min. Halothane ED-50 varied with temperature (0.8% at 10 degrees C and 1.6% at 23 degrees C). Time to reach ED-50-H decreased with increases in respiratory rate, but increased as water temperature was elevated.

Animals↗
PubMed2003

Osteoid osteoma: elevation of cardiac and respiratory rates at biopsy needle entry into tumor in 10 patients.

PURPOSE: To evaluate changes in cardiac and respiratory rates in a consecutive series of patients who underwent percutaneous treatment for lesions presumed to be osteoid osteoma in whom general anesthesia was established. MATERIALS AND METHODS: Changes in cardiac and respiratory rates were evaluated after establishment of stable general anesthesia in 14 patients who underwent needle biopsy and radio-frequency treatment. Cardiac and respiratory rates were recorded at penetration of skin, muscle, periosteum, cortex, and tumor. Treatment was performed before the biopsy report was available. RESULTS: Biopsy results revealed osteoid osteoma in 10 patients, chondroblastoma in one, and a herniation pit in one. Results in the two remaining patients were nondiagnostic and were excluded. Puncture of skin, muscle, and periosteum caused no detectable change. However, in the 10 patients with biopsy-proved osteoid osteoma, puncture of the tumor caused the mean cardiac rate to increase an average of 26 beats per minute (40%) to 91 (range, 62-114; P <.001) and the mean respiratory rate to increase an average of 12 breaths per minute (50%) to a mean of 37 (range, 25-52; P <.001). These changes occurred within seconds of tumor puncture and were often the first indication to the surgeon that the tumor had been entered. In the two patients with other diagnoses at biopsy, no such change was apparent. CONCLUSION: Mean cardiac and respiratory rates increase significantly at needle puncture of osteoid osteoma.

Adolescent↗
PubMed1993

Experimental evaluation of two new sensors for respiratory rate monitoring.

Visual observation was chosen as the reference method for measuring the respiratory rate in ten healthy volunteers. The new fibre-optic and acoustic sensors were simultaneously compared with capnography and transthoracic impedance plethysmography during normoventilation in the respiratory rate range of 6-24 breaths per minute and at a fixed respiratory rate of 13 breaths per minute. In addition a simulation of central apnoea was performed. All the measurements were recorded on an analogue tape recorder and a strip-chart recorder and analysed off line. The analyses of the recordings were performed by a person who was unable to see the monitoring systems. There was no discrepancy in the results of these methods. Each of the methods responded rapidly to an apnoeic event. The new fibre-optic and acoustic sensors correlate well with more traditional methods such as capnography and transthoracic impedance plethysmography for respiratory rate monitoring.

Acoustics↗
PubMed1994

The oxygen cost of breathing may predict weaning from mechanical ventilation better than the respiratory rate to tidal volume ratio.

OBJECTIVE: To compare the respiratory rate to tidal volume ratio with the oxygen cost of breathing to see which could more accurately predict the outcome of ventilator weaning for surgical patients. DESIGN: Prospective comparison of two modalities used to predict the likelihood of successful ventilator weaning. PATIENTS: Twenty-eight consecutive patients with chronic respiratory insufficiency requiring long-term mechanical ventilation in the surgical intensive care unit at New England Deaconess Hospital, Boston, Mass, were studied. MAIN OUTCOME MEASURES: The oxygen cost of breathing and the respiratory rate to tidal volume ratio were measured during spontaneous breathing. Patients extubated within 2 weeks of being studied were designated as extubated while patients not extubated within this period or requiring reintubation were recorded as not extubated. RESULTS: The oxygen cost of breathing predicted successful extubation in all five patients who were extubated, and failure in 20 of 23 patients who could not be extubated (sensitivity, 100%; specificity, 87%). In contrast, the respiratory rate to tidal volume ratio predicted extubation for only two of five patients who were extubated and predicted failure in only 12 of 23 patients who could not be extubated (sensitivity, 40%; specificity, 52%). CONCLUSION: For this group of patients requiring prolonged ventilation, the oxygen cost of breathing proved to be a more reliable predictor of both successful extubation and failure.

Aged↗