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PubMed2001

Statistical shape analysis of volumetric capnograms: evaluation of a new approach for the assessment of pulmonary function in horses with chronic obstructive pulmonary disease.

The shape of the volumetric capnogram is modified by airway obstruction, and the evaluation of this deformation could allow an indirect measurement of bronchial patency. The study included 35 horses; five horses without evidence of pulmonary disease (group I) and 30 horses suffering from different degrees of chronic obstructive pulmonary disease (COPD) (groups II-IV). Data of recorded CO2 and volume curves were off-line plotted and statistically analysed using regression analysis. Analyses were performed separately for fractions 25-95% (VTE25-95), 25-50% (VTE25-50) and 50-95% (VTE50-95) of expiratory tidal volume. For VTE25-95 estimates of linear and quadratic regression parameters were significantly different between groups. For VTE25-50 linear terms were significant in all clinical groups and decreased considerably from group I to group IV. Linear and quadratic terms for VTE50-95 were significant in all clinical groups and increased with the severity of COPD. The difference of total expiratory CO2 volume was significant between all groups. Statistical analysis of the volumetric capnogram is a precise method for description of shape deformities of the single breath diagram for CO2 (SBD-CO2) in horses with COPD and global models including phase II and III of the SBD-CO2 are helpful in the detection of pulmonary function impairment. However, although the model of the statistical shape analysis of the SBD-CO2 is precise, it may not necessarily be a useful test to discriminate horses with minor, moderate and severe COPD for clinical use.

Animals↗
PubMed1997

Spontaneous breathing with the use of a laryngeal mask airway in children: comparison of sevoflurane and isoflurane.

We compared respiratory parameters during anaesthesia with sevoflurane and isoflurane through a laryngeal mask airway (LMA). Children were anaesthetized with O2 and air with 2.3% (1MAC) sevoflurane (n = 20) or 1.5% (1MAC) isoflurane (n = 20). After insertion of LMA, patients were allowed to breathe spontaneously and respiratory rate (RR) and PECO2 were measured (presurgery state). After the measurement, anaesthetic concentration was increased to 1.3 MAC (3.0% sevoflurane or 2.0% isoflurane) and surgical stimulation was added. Fifteen min after incision, the measurements were again performed (during surgery). In the sevoflurane group, mean RR and PECO2 were 32 breaths.min-1, and 6.0 kPa (45 mmHg) respectively, before surgery, and 35 breaths.min-1 and 7.0 kPa (52 mmHg) during surgery. In the isoflurane group, mean RR and PECO2 were 32 breaths.min-1 and 6.1 kPa (46 mmHg) respectively, before surgery, and 37 breaths.min-1 and 6.7 kPa (52 mmHg) during surgery. There were no statistical differences between the two anaesthetic groups. Clinical respiratory and cardiovascular parameters during spontaneous breathing with LMA in children are similar during sevoflurane and isoflurane anaesthesia.

Anesthetics, Inhalation↗
PubMed2003

Anaesthetic consequences for a child with complex multilevel airway obstruction -- recommendations for avoiding life-threatening sequelae.

A boy with a suspected lymphoid malignancy presented with gross head and neck lymphadenopathy, a middle mediastinal mass, and rapidly worsening airway obstruction. General anaesthesia was required for definitive histopathological diagnosis. The combination of nasopharyngeal obstruction, malignant infiltration of the tonsils and pharynx, laryngeal displacement, and potential tracheal compression put this patient at extreme risk for perioperative airway complications. Risk assessment, and the impact of anaesthesia on pharyngeal neuromechanical function and mediastinal masses are discussed. Caution with volatile anaesthetic agents is recommended in the patient with an inherently unstable pharynx and/or trachea, in whom airway patency relies on a spontaneously breathing technique and intact airway reflexes.

Airway Obstruction↗
PubMed2001

NPB-75: A portable quantitative microstream capnometer.

A portable quantitative microstream capnometer (NPB-75) was tested in intubated children. The end-tidal CO(2) values measured by this device showed good agreement with concomitantly measured values of a stationary mainstream capnometer (N-6000). This lightweight device, with a 4-hour battery life, graphic capnogram display, and audiovisual alarms is well suited for the prehospital setting.

Age Factors↗
PubMed2003

A comparison of the end-tidal CO2 measured by portable capnometer and the arterial PCO2 in spontaneously breathing patients.

An end-tidal CO2 (ETCO2) monitor (capnometer) is used most often as a noninvasive substitute for PaCO2 in anesthesia, anesthetic recovery and intensive care. However, the utility and accuracy of the portable capnometer in spontaneously breathing patients with or without chronic pulmonary diseases has received little recognition. To determine the utility of the portable capnometer in general wards and in in-home care, we examined the correlation between ETCO2 measured by a portable capnometer and simultaneous PaCO2 measured in 41 spontaneously breathing patients. TV-ETCO2 (ETCO2 measured by tidal volume maneuver) was lower than PaCO2 by an average of 9.0 mmHg and VC-ETCO2 (ETCO2 measured by vital capacity maneuver) was lower than PaCO2 by an average of 0.5 mmHg. The mean difference between PaCO2 and VC-ETCO2 was not statistically significant. Regression analysis showed a close correlation between VC-ETCO2 and PaCO2 (r = 0.91, P < 0.0001). Thus,VC-ETCO2 was highly correlated with PaCO2. Furthermore, a close correlation between VC-ETCO2 and PaCO2 was also observed in patients with compromised pulmonary function (r = 0.88, P < 0.0001 in patients with below 70% of FEV(1.0)%; r = 0.89, P < 0.0001 in patients with below 80% of %VC). Our studies show that VC-ETCO2 measured by the portable capnometer gives a reliable pointestimate of PaCO2, and can be useful to evaluate the respiratory condition of spontaneously breathing patients in general wards and in in-home care.

Aged↗
PubMed2002

Validity of pulmonary function indices derived from the volumetric capnogram in horses with recurrent airway obstruction (RAO).

The objective of this study was to determine the accuracy with which pulmonary function indices derived from the volumetric capnogram can diagnose different degrees of recurrent airway obstruction (RAO) in 63 warmblood horses. The sensitivity, specificity, the area under the receiver operating curve (AUC), optimal cut-off values and predictive values of the indices were calculated. The results obtained have shown that there is no single index characterised by specificity and sensitivity to differentiate with an accuracy of >90 per cent between the different degrees of RAO compared to the clinical examination. The indices A(1)/A(2) and VD(alv)/ VT(alv) (AUC=0.55 and 0.53) appeared to have the highest relative sensitivity and specificity to differentiate between healthy horses and horses suffering from subclinical or minor RAO and the indices VD(phys)/ VT and VD(Bohr)/ VT between horses suffering from subclinical or minor RAO and horses with moderate to severe RAO (AUC=0.71 and 0.70). We do not consider it acceptable to use cut off values optimised for both maximal sensitivity and specificity, because a great number of horses would have been inappropriately classified.

Airway Obstruction↗
PubMed1997

End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest.

BACKGROUND: Survival after cardiac arrest occurring outside the hospital averages less than 3 percent. Unfortunately, the outcome of prolonged resuscitative attempts cannot be predicted. End-tidal carbon dioxide levels reflect cardiac output during cardiopulmonary resuscitation. We prospectively determined whether death could be predicted by monitoring end-tidal carbon dioxide during resuscitation after cardiac arrest. METHODS: We performed a prospective observational study in 150 consecutive victims of cardiac arrest outside the hospital who had electrical activity but no pulse. The patients were intubated and evaluated by mainstream end-tidal carbon dioxide monitoring. Our hypothesis was that an end-tidal carbon dioxide level of 10 mm Hg or less after 20 minutes of standard advanced cardiac life support would predict death. RESULTS: There was no difference in the mean age or initial end-tidal carbon dioxide level between patients who survived to hospital admission (survivors) and those who did not (nonsurvivors). After 20 minutes of advanced cardiac life support, end-tidal carbon dioxide (+/-SD) averaged 4.4+/-2.9 mm Hg in nonsurvivors and 32.8+/-7.4 mm Hg in survivors (P< 0.001). A 20-minute end-tidal carbon dioxide value of 10 mm Hg or less successfully discriminated between the 35 patients who survived to hospital admission and the 115 nonsurvivors. When a 20-minute end-tidal carbon dioxide value of 10 mm Hg or less was used as a screening test to predict death, the sensitivity, specificity, positive predictive value, and negative predictive value were all 100 percent. CONCLUSIONS: An end-tidal carbon dioxide level of 10 mm Hg or less measured 20 minutes after the initiation of advanced cardiac life support accurately predicts death in patients with cardiac arrest associated with electrical activity but no pulse. Cardiopulmonary resuscitation may reasonably be terminated in such patients.

Adult↗
PubMed2001

Misplaced endotracheal tubes by paramedics in an urban emergency medical services system.

STUDY OBJECTIVE: To determine the incidence of unrecognized, misplaced endotracheal tubes inserted by paramedics in a large urban, decentralized emergency medical services (EMS) system. METHODS: We conducted a prospective, observational study of patients intubated in the field by paramedics before emergency department arrival. During an 8-month period, emergency physicians assessed tube position at ED arrival using a combination of auscultation, end-tidal carbon dioxide (ETCO(2)) monitoring, and direct laryngoscopy. RESULTS: A total of 108 intubated patients were studied. On arrival in the ED, 25% (27/108) of patients were found to have improperly placed endotracheal tubes. Of the misplaced tubes, 67% (18/27) were found to be in the esophagus, whereas in 33% (9/27), the tip of the tube was found to be in the hypopharynx, above the vocal cords. Of the patients with misplaced tubes noted in the hypopharynx, 33% (3/9) died while in the ED. For the patients found to have tubes in the hypopharynx, 56% (5/9) had evidence of ETCO(2) on ED arrival. For the patients found to have esophageal tube placement on ED arrival, 56% (10/18) died in the ED. Esophageal intubation was associated with an absence of expired CO(2) (17/18, 94%) on ED arrival. The single patient in this subset with a recordable ETCO(2) had been nasotracheally intubated with the tip of the endotracheal tube noted in the esophagus while spontaneous respirations were present. On patient arrival to the ED, 63% (68/108) of the patients had direct laryngoscopy in addition to ETCO(2) determination. All patients had ETCO(2) evaluation performed on arrival. All patients in whom an absence of ETCO(2) was demonstrated on patient arrival underwent direct laryngoscopy. In cases in which direct laryngoscopy was not performed, the attending physician documented the ETCO(2) in conjunction with the presence of bilateral breath sounds. CONCLUSION: The incidence of out-of-hospital, unrecognized, misplaced endotracheal tubes in our community is excessively high and may be reflective of the incidence occurring in other communities. Data from other communities are needed to clarify the scope of this alarming issue.

Allied Health Personnel↗
PubMed2003

Elimination of ventilator dead space during synchronized ventilation in premature infants.

BACKGROUND: Mainstream airflow sensors used in neonatal ventilators to synchronize mechanical breaths with spontaneous inspiration and measure ventilation increase dead space and may impair carbon dioxide (CO(2)) elimination. OBJECTIVE: To evaluate a technique consisting of a continuous gas leakage at the endotracheal tube (ETT) adapter to wash out the airflow sensor for synchronization and ventilation monitoring without CO(2) rebreathing in preterm infants. DESIGN: Minute ventilation (V'(E)) by respiratory inductance plethysmography, end-inspiratory and end-expiratory CO(2) by side-stream microcapnography, and transcutaneous CO(2) tension (TcPCO(2)) were measured in 10 infants (body weight, 835+/-244 g; gestational age, 26+/-2 weeks; age, 19+/-9 days; weight, 856+/-206 g; ventilator rate, 21+/-6 beats/min; PIP, 16+/-1 centimeters of water (cmH(2)O); PEEP, 4.2+/-0.4 cmH(2)O; fraction of inspired oxygen (FIo(2)), 0.26+/-0.6). The measurements were made during four 30-minute periods in random order: IMV (without airflow sensor), IMV+Sensor, SIMV (with airflow sensor), and SIMV+Leak (ETT adapter continuous leakage). RESULTS: Airflow sensor presence during SIMV and IMV+Sensor periods resulted in higher end-inspiratory and end-expiratory CO(2), Tcpco(2), and spontaneous V'(E) compared with IMV. These effects were not observed during SIMV+Leak. CONCLUSIONS: The significant physiologic effects of airflow sensor dead space during synchronized ventilation in preterm infants can be effectively prevented by the ETT adapter continuous leakage technique.

Blood Gas Analysis↗
PubMed1998

Metabolism of parenterally administered fat emulsions in the rat: studies of fatty acid oxidation with 1-13C- and 8-13C-labelled triolein.

To reassess the hypothesis that fatty acid catabolism occurs to completion via beta-oxidation, male Sprague-Dawley rats receiving continuous total parenteral nutrition (TPN) including 43% energy as fat were infused with [1-(13)C]- or [8-(13)C]triolein. Expired CO2 was collected continuously for 4 h and its 13C:12C ratio determined by isotope-ratio mass spectrometry. Bicarbonate retention was also assessed over 4 h by infusion of NaH14CO3 and measurement of the expired 14CO2. A possible loss of label from [8-(13)C]oleic acid from the citric acid cycle via labelled acetyl-CoA without oxidation to CO2 was assessed by infusing further animals with acetate labelled with 14C either at C atoms 1 or 2 and determination of its conversion to expired 14CO2. At isotopic steady state, 63.2 (SE 1.6)% (n 8) of the infused [1-(14)C]acetate and 46.0 (SE 1.2)% (n 8) of [2-(14)C]acetate was recovered as expired 14CO2. After correction for bicarbonate retention and non-oxidative isotope loss, 37.3 (SE 1.2)% (n 20) of the [1-(13)C]triolein was found to have been oxidized, whereas 32.6 (SE 1.0)% (n 20) of the [8-(13)C]triolein was oxidized (P < or = 0.01). The lower oxidation of the C atom at position 8 of oleic acid than that at position 1 indicates incomplete oxidative breakdown of the fatty acid after entering beta-oxidation.

Acetates↗
PubMedDate not supplied

A virtual instrument (VI) for haemodynamic management in ICU and during surgery.

Systolic pressure variations (SPV) during mechanical ventilation and its single components, related to short apnea, reflect changes of the volemic condition of the patient. To introduce their determination during clinical monitoring for different fluid states and for different tidal volumes, they must be computed on-line without introducing interference with standard activities. A system computing on-line systolic pressure variation during mechanical ventilation, connected to standard monitoring devices, has been proposed. It is based on a notebook PC implemented with graphical software comprising a user panel in the form of a virtual instrument and is able to acquire, process and present signals from different instruments utilized in ICU and during surgery. It can be used as a base to assess the ability of computed parameters helpful in clinical decision. The use of a notebook PC and open software allows operators, even if non-expert in computer science, to test and implement this, as well as other innovative tools in clinical practice.

Blood Pressure Determination↗
PubMed2004

Breathing patterns in term infants delivered by caesarean section.

AIM: To compare the breathing patterns of infants born by elective caesarean section to those infants delivered by caesarean section after a failed trial of labour. METHODS: Healthy term infants born by caesarean section were studied. The study group (n = 13) had no trial of labour, whereas infants in the control group (n = 13) failed a trial of labour. Polysomnographic study was performed at 36 h of age. Heart and respiratory rate, type and duration of apnoeas, arterial oxygen saturation and lower limb movements were analysed. RESULTS: Term infants born by elective caesarean section had a shorter duration of pregnancy and weighed less. Their heart rate was faster, they had more mixed apnoeas, and during quiet sleep they had more central apnoeas of longer duration. CONCLUSION: Cardiorespiratory patterns in infants delivered by elective caesarean section are different from those delivered by caesarean section after a failed trial of labour.

Brain↗
PubMedDate not supplied

End-tidal carbon dioxide monitoring in the prehospital setting.

End-tidal carbon dioxide (ETCO2) monitoring is an exciting technology and has the potential to become a very useful tool in the prehospital setting. It can be useful in verifying endotracheal tube position and during cardiopulmonary resuscitation in the field. Recent reports of misplaced endotracheal tubes in the prehospital setting make it important to ensure that paramedics learn correct techniques of endotracheal intubation, and that they verify tube placement with an ETCO2 monitor. The new American Heart Association guidelines require secondary confirmation of proper tube placement in all patients by exhaled CO2 immediately after intubation and during transport. This article covers the terminology, the basic physiology, the technology (both colorimetric detectors and infrared capnometers), and the clinical applications of ETCO2 monitoring with special reference to the pediatric patient.

Capnography↗
PubMedDate not supplied

Confirmation of airway placement.

Proper airway management in the prehospital setting is essential. Recent data from Orange County, Florida, suggest that the problem of misplaced endotracheal tubes may be greater than previous studies have indicated. Strong medical direction, strict protocols, and active continuous quality improvement programs are needed to ensure that paramedics learn the correct techniques of endotracheal intubation, and that they verify tube placement with an end-tidal carbon dioxide monitor, and maintain ongoing monitoring of tube placement during transport.

Algorithms↗
PubMedDate not supplied

Management of difficult airways in the field.

Establishing an airway is a critical first step in emergency management of comatose patients and those who have suffered head trauma, cardiac arrest, or respiratory failure. The use of succinylcholine, a paralytic, to assist with intubation is a safe and effective way to help establish an airway under difficult circumstances, in the prehospital setting. It requires excellent intubation skills, a thorough knowledge of the indications and contraindications of its use, and similar knowledge of any other medications employed. Succinylcholine-assisted intubation should never be implemented without close physician monitoring. Therefore, under the auspices of strong medical control, it is an effective way to establish adequate oxygenation and to control ventilation in some of the most critical patients encountered in the field. Additionally, because physical examination alone is not dependable for ensuring proper endotracheal tube placement, an objective confirmatory device such as an end-tidal carbon dioxide detector should be used.

Capnography↗