Arterial Partial Pressure Of Carbon Dioxide Research Articles

Extracorporeal pumpless interventional lung assist in clinical practice: determinants of efficacy

Respiratory acidosis can become a serious problem during protective ventilation of severe lung failure. A pumpless arteriovenous interventional lung assist (iLA) for extracorporeal carbon dioxide removal has been used increasingly to control critical respiratory situations. The present study sought to evaluate the factors determining the efficacy of iLA and calculate its contribution to gas exchange. In a cohort of 96 patients with severe acute respiratory distress syndrome, haemodynamic parameters, oxygen consumption and carbon dioxide production as well as gas transfer through the iLA were analysed. The measurements demonstrated a significant dependency of blood flow via the iLA device on cannula size (mean+/-sd 1.59+/-0.52 L x min(-1) for 15 French (Fr), 1.94+/-0.35 L x min(-1) for 17 Fr, and 2.22 +/-0.45 L x min(-1) for 19 Fr) and on mean arterial pressure. Oxygen transfer capacity averaged 41.7+/-20.8 mL x min(-1), carbon dioxide removal was 148.0+/-63.4 mL x min(-1). Within two hours of iLA treatment, arterial oxygen partial pressure/inspired oxygen fraction ratio increased significantly and a fast improvement in arterial carbon dioxide partial pressure and pH was observed. Interventional lung assist eliminates approximately 50% of calculated total carbon dioxide production with rapid normalisation of respiratory acidosis. Despite limited contribution to oxygen transfer it may allow a more protective ventilation in severe respiratory failure.

Successful Transtracheal Lung Ventilation Using a Manual Respiration Valve

Lung ventilation through a thin transtracheal cannula may be attempted in patients with laryngeal stenosis or "cannot intubate, cannot ventilate" situations. It may be impossible to achieve sufficient ventilation if the lungs are spontaneously emptying only through the thin transtracheal cannula, which imposes high resistance to airflow, resulting in dangerous hyperinflation. Therefore, the authors describe the use of a manual respiration valve that serves as a bidirectional pump providing not only inflation but also active deflation of the lungs in case of emergency transtracheal lung ventilation. The effectiveness of such a valve was tested in vitro using mechanical lungs in combination with two different cannula sizes and various gas flows. The valve was then tested in five pigs using a transtracheal 16-gauge cannula with three different combinations of inspiratory/expiratory times and gas flows and an occluded upper airway. In the mechanical lungs, the valve permitted higher minute volumes compared with spontaneous lung emptying. In vivo, the arterial oxygen and carbon dioxide partial pressures increased initially and then remained stable over 1 h (arterial oxygen tension, 470.8 +/- 86.8; arterial carbon dioxide tension, 63.0 +/- 7.2 mmHg). The inspiratory pressures measured in the trachea remained below 10 cm H2O and did not substantially influence central venous and pulmonary artery pressures. Mean arterial pressure and cardiac output were unaffected by the ventilation maneuvers. This study demonstrated in vitro and in vivo in adult pigs that satisfactory lung ventilation can be assured with transtracheal ventilation through a 16-gauge cannula for a prolonged period of time if combined with a bidirectional manual respiration valve.

The influence of oxygenotherapy on the hypercapnia in patients with chronic obstructive pulmonary disease

Oxygen therapy is a necessary therapeutic method in treatment of severe chronic respiratory failure (CRF), especially in phases of acute worsening. Risks which are to be taken into consideration during this therapy are: unpredictable increase of carbon dioxide in blood, carbonarcosis, respiratory acidosis and coma. The aim of this study was to show the influence of oxygen therapy on changes of arterial blood carbon dioxide partial pressure. The study included 93 patients in 104 admittances to the hospital due to acute exacerbation of CFR. The majority of the patients (89.4%) had chronic obstructive pulmonary disease (COPD), while other causes of respiratory failure were less common. The effect of oxygenation was controlled through measurement of PaO2 and PaCO2 in arterial blood samples. To analyse the influence of oxygen therapy on levels of carbon dioxide, greatest values of change of PaO2 and PaCO2 values from these measurements, including corresponding PaO2 values from the same blood analysis were taken. The obtained results show that oxygen therapy led to the increase of PaO2 but also to the increase of PaCO2. The average increase of PaO2 for the whole group of patients was 2.42 kPa, and the average increase of PaCO2 was 1.69 kPa. There was no correlation between the initial values of PaO2 and PaCO2 and changes of PaCO2 during the oxygen therapy. Also, no correlation between the produced increase in PaO2 and change in PaCO2 during this therapy was found. Controlled oxygen therapy in patients with severe respiratory failure greately reduces the risk of unwanted increase of PaCO2, but does not exclude it completely. The initial values of PaO2 and PaCO2 are not reliable parameters which could predict the response to oxygen therapy.

Near-fatal pediatric asthma managed with pumpless arteriovenous carbon dioxide removal*

To describe the use of pumpless arteriovenous carbon dioxide removal in support of four pediatric patients with near-fatal asthma. Report of four cases. Tertiary care university pediatric intensive care unit. Four pediatric patients, ages 4, 10, 12, and 13, were intubated and initially managed with positive pressure ventilation for severe respiratory failure. Despite pharmacologic therapy with inhaled beta-agonists, inhaled anticholinergics, systemic corticosteroids, and intravenous magnesium, marked progressive hypercapnia and acidosis rapidly developed requiring high levels of positive pressure ventilation. Application of pumpless arteriovenous carbon dioxide removal (AVCO2R) via percutaneous femoral cannulation. Arterial or mixed venous carbon dioxide partial pressure (PCO2) and pH were measured before and at intervals following initiation of AVCO2R. Before cannulation, PCO2 was elevated to 100, 108, 90, and 186 mm Hg in the four patients, with corresponding pH of 7.07, 6.96, 7.09, and 6.80, respectively. Pco2 levels were reduced to more acceptable levels (37-57 mm Hg) within 2-4 hrs of initiation of AVCO2R, with corresponding improvements in pH despite reductions in ventilatory frequency and tidal volumes to safe levels. Duration of support ranged from 18 hrs to 5 days during resolution of bronchospasm. No red blood cell or platelet transfusions were required, and no complications resulted from AVCO2R or from mechanical ventilation. All patients were discharged from the hospital without sequelae. Percutaneous cannulation with a simplified pumpless extracorporeal circuit is capable of removing sufficient carbon dioxide to allow application of a protective ventilatory strategy in severe hypercapnic pediatric respiratory failure. The procedure was safely applied without complications in four pediatric patients as young as 4 yrs of age.

Review Series: Lung function made easy: Assessing gas exchange

In clinical practice there are two sorts of measurements, a) arterial oxygen and carbon dioxide partial pressure (PaO2, PaCO2) or arterial oxygen saturation (SaO2), and b) the transfer capacity for carbon monoxide (TLCO). The former measures the output or performance of the lung as a gas exchanger, and the latter estimates the available surface area or potential for gas exchange. As gas exchange deteriorates (PaO2 falls and PaCO2 rises), the body compensates by increasing ventilation and lowering PaCO2). Therefore, a high PaCO2 represents chronic respiratory or "compensation" failure, either chemo-insensitivity ("won't breathe") or neuromuscular weakness/increased work of breathing ("cannot breathe"). Chronic respiratory failure may progress to acute failure in which PaCO2 falls and PaCO2 rises progressively, assisted ventilation is usually required. The TLCO is a laboratory test which measures the integrity of the blood-gas barrier, it is particularly useful in the assessment of emphysema, interstitial disease and pulmonary vascular disease.

Noninvasive Assisted Pressure-Controlled Ventilation: As Effective as Pressure Support Ventilation in Chronic Obstructive Pulmonary Disease?

Background: Noninvasive ventilation (NIV) is being increasingly used in hypercapnic chronic obstructive pulmonary disease (COPD) patients but the most appropriate ventilation mode is still not known. Objectives: The aim of this study was to investigate if assisted pressure-controlled ventilation (APCV) can be a better alternative to pressure-support ventilation (PSV) for NIV in COPD patients with acute hypercapnic respiratory failure (AHRF). Methods: In this prospective randomized study, we evaluated the early effects of noninvasive APCV and PSV in 34 consecutive COPD patients with AHRF. Patients were randomized into 1 of the 2 modes, and respiratory and hemodynamic values were compared before and after 1 h of NIV. Results: Baseline values did not differ between the 2 groups. There were significant improvements in partial arterial carbon dioxide pressure and pH levels in the APCV group when compared with baseline (p < 0.05). Cardiac output and cardiac index decreased in both groups (p < 0.05) but more significantly in the PSV group (p < 0.0001). The decreases in stroke volume index and increases in arterial oxygen content after NIV were also considerable in both groups (p < 0.05). Central venous pressure and systemic vascular resistance index values increased notably only after PSV (p < 0.05). Conclusions: From these data, we deduce that APCV can be a better alternative to PSV for NIV in COPD patients with AHRF owing to its more beneficial physiological effects.

An evaluation of capnography monitoring during the apnoea test in brain-dead patients

Diagnosis of brain death usually requires the absence of spontaneous respiratory movements during the apnoea test and an arterial carbon dioxide partial pressure above 60 mmHg. On the other hand, although capnography (end-tidal CO(2)) is currently monitored in intensive care unit patients, it has not been evaluated during the apnoea test in brain-dead patients. Therefore, the aim of this prospective study was first to investigate the usefulness of capnography monitoring, and secondly to evaluate the variation of the carbon dioxide partial pressure-end-tidal CO(2) gradient during the apnoea test in clinically brain-dead patients. After local Ethics Committee approval, 60 clinically brain-dead patients were investigated. End-tidal CO(2) was continuously recorded before, during and after the apnoea test. Arterial blood gases were sampled immediately before and after the apnoea test for calculation of the carbon dioxide partial pressure-end-tidal CO(2) gradient. The apnoea test was clinically positive in 58 patients, whereas end-tidal CO(2) was equal to 0 during the apnoea. During the 20-min apnoea test, carbon dioxide partial pressure increased from 40 +/- 7 to 97 +/- 19 mmHg (P < 0.001) with a rate of 2.8 +/- 0.9 mmHg min(-1), end-tidal CO(2) increased from 31 +/- 6 to 68 +/- 17 mmHg (P < 0.001) and carbon dioxide partial pressure-end-tidal CO(2) gradient increased from 9 +/- 4 to 29 +/- 10 mmHg (P < 0.001). In two patients, the apnoea test was clinically negative because of the occurrence of spontaneous respiratory movements, whereas capnography showed contemporaneously significant increases in end-tidal CO(2). End-tidal CO(2) should be systematically monitored and recorded, at least for medico-legal considerations, during the apnoea test in brain-dead patients. The high variability in the carbon dioxide partial pressure-end-tidal CO(2) gradient increase precludes any extrapolation of the carbon dioxide partial pressure from the end-tidal CO(2) at the end of the apnoea test.

Cerebral haemodynamics and carbon dioxide reactivity during sepsis syndrome

BackgroundMost patients with sepsis develop potentially irreversible cerebral dysfunctions. It is yet not clear whether cerebral haemodynamics are altered in these sepsis patients at all, and to what extent. We hypothesized that cerebral haemodynamics and carbon dioxide reactivity would be impaired in patients with sepsis syndrome and pathological electroencephalogram patterns.MethodsAfter approval of the institutional ethics committee, 10 mechanically ventilated patients with sepsis syndrome and pathological electroencephalogram patterns underwent measurements of cerebral blood flow and jugular venous oxygen saturation before and after reduction of the arterial carbon dioxide partial pressure by 0.93 ± 0.7 kPa iu by ypervent ilation. The cerebral capillary closing pressure was determined from transcranial Doppler measurements of the arterial blood flow of the middle cerebral artery and the arterial pressure curve. A t test for matched pairs was used for statistical analysis (P < 0.05).ResultsDuring stable mean arterial pressure and cardiac index, reduction of the arterial carbon dioxide partial pressure led to a significant increase of the capillary closing pressure from 25 ± 11 mmHg to 39 ± 15 mmHg (P < 0.001), with a consecutive decrease of blood flow velocity in the middle cerebral artery of 21.8 ± 4.8%/kPa (P < 0.001), of cerebral blood flow from 64 ± 29 ml/100 g/min to 39 ± 15 ml/100 g/min (P < 0.001) and of jugular venous oxygen saturation from 75 ± 8% to 67 ± 14% (P < 0.01).ConclusionIn contrast to other experimental and clinical data, we observed no pathological findings in the investigated parameters of cerebral perfusion and oxygenation.

Pressure-Controlled versus Volume-Controlled One-Lung Ventilation for MIDCAB

One-lung ventilation is limited by hypoventilation and hypoxemia because of increasing airway pressure and intrapulmonary shunt. Previous clinical studies compared pressure-controlled versus volume-controlled ventilation during one-lung ventilation in patients with pre-existing pulmonary disease. We studied 50 patients undergoing thoracotomy and one-lung ventilation because of cardiovascular disease. After two-lung ventilation with volume-controlled ventilation, patients were divided randomly into two groups. In one group, ventilation was switched to pressure-controlled ventilation after starting one-lung ventilation. In the other group, volume-controlled ventilation was continued. Parameters of ventilation, pulmonary function and systemic and pulmonary hemodynamics were recorded. We observed, that peak airway pressure, dead space ventilation and arterial carbon dioxide partial pressure were significantly higher during volume-controlled ventilation. After one-lung ventilation patients with pressure controlled ventilation had lower alveolar-arterial oxygen tension difference and a higher arterial oxygen partial pressure with significant differences for those patients in the intensive care unit. We conclude that pressure-controlled ventilation may be useful to improve gas exchange and alveolar recruitment during one lung ventilation.

Estimation of arterial from a lung model during ramp exercise in healthy young subjects

The aim of this study is to propose a new approach to estimate non-invasively arterial carbon dioxide partial pressure (P(a)CO2) approach was based on the reconstruction of alveolar gas composition over each breath from a tidally ventilated lung model (P(M)(CO2)). Eight healthy young subjects were studied during a ramp exercise test on a cycle ergometer. Arterial samples were drawn at rest and every minute during the exercise test for determination of P(a)CO2 . P(a)CO2 was compared with indirect estimates of P(CO2) : P(M)(CO2), end-tidal P(CO2) (P(ET)(CO2)) and an empirical equation involving P(ET)(CO2) and tidal volume (P(J)(CO2)). The difference between estimated and measured P(a)CO2 on the whole ramp exercise was -0.3+/-1.9mmHg for P(M)(CO2), 1.0+/-2.2mmHg for P(ET)(CO2) and -1.7+/-1.7mmHg for P(J)(CO2) . P(ET)(CO2) and P(J)(CO2) were significantly different from actual P(a)CO2 (P<0.001). It is concluded that, on the basis of the bias, the breathing lung model gave better estimates of P(a)CO2 than the two other indirect methods during ramp exercise.

Outcome value of Clara cell protein in serum of patients with acute respiratory distress syndrome

Injury to the alveolocapillary barrier characterizes ALI/ARDS; therefore determining levels of lung epithelium-specific small proteins in serum may help predict clinical outcomes. We examined whether serum Clara cell protein (CC-16) concentration is correlated with the outcome, mechanical ventilation duration, and incidence of nonpulmonary organ failure. Prospective multicenter observational study conducted by the Quebec Critical Care Network. Seventy-eight adult ARDS patients requiring mechanical ventilation were enrolled and 28-day mortality was the primary outcome. Ventilatory parameters were computed and blood was sampled daily. Clinical information collected included cause of death, duration of mechanical ventilation, number of ventilator-free days, and organ failures. Median serum levels of CC-16 were significantly higher in nonsurvivors than survivors on days 0-2 (19.93 microg/l, IQR 11.8-44.32, vs. 8.9, 5.66-26.38) and sustained up to day 14. CC-16 levels were correlated positively with the number of failing organs (rho 0.3623) and requirement for prolonged mechanical ventilation. Predictors of patient mortality included age, arterial carbon dioxide partial pressure, CC-16, and APACHE II score (odds ratios 1.35, 1.52, 1.37, 1.159, respectively). Higher initial CC-16 serum level is associated with increased risk of death, fewer ventilator-free days, and increased frequency of nonpulmonary multiple organ failure. CC-16 is a valuable biomarker of ARDS that may help predict outcome among ARDS patients with high-risk mortality.

Determination of optimal arterial carbon dioxide partial pressure (paCO2) in patients with brain injury

Determination of optimal arterial carbon dioxide partial pressure (paCO2) in patients with brain injury

Magnetic resonance imaging evaluation of bone marrow changes in obstructive sleep apnoea syndrome in adults

The aim of this study was to evaluate bone marrow reconversion in patients with obstructive sleep apnoea syndrome (OSAS) by means of magnetic resonance imaging (MRI). To our knowledge, no explicit correlation between OSAS and such parameter has been documented in the literature. During a 35-month period, 33 patients with a clinical diagnosis of OSAS, obese but without restrictive or obstructive ventilatory defects, were evaluated with MRI during wakefulness in all patients with T1-, PD- and T2-weighted sequences in the sagittal and axial plane within 1 week after polysomnography. MRI showed bone marrow reconversion in 33.3% of patients. Patients with bone marrow reconversion showed higher mean haematocrit (HT) values, lower mean nocturnal oxyhaemoglobin saturation, higher percentage of sleep time with oxygen saturation (SaO2) <90%, lower nadir, as well as greater neck adiposity and soft-palate lengthening compared with patients without bone marrow reconversion. Furthermore, in patients with bone marrow reconversion, haematocrit (HT) was negatively correlated with daytime arterial oxygen partial pressure (PaO2) and positively with arterial carbon dioxide partial pressure (PaCO2). In patients with OSAS, bone marrow reconversion is probably correlated with the severity of nocturnal desaturation. As bone marrow reconversion is, for unknown reasons, greater in adults younger than 40 years, MRI evidence of bone marrow reconversion could be useful in young individuals for the early diagnosis of sleep-disordered breathing and prevention of associated cardiovascular diseases.

An Evaluation of Transcutaneous Carbon Dioxide Partial Pressure Monitoring during Apnea Testing in Brain-dead Patients

Diagnosis of brain death usually requires an arterial carbon dioxide partial pressure (Paco2) of 60 mmHg during the apnea test, but the increase in Paco2 is unpredictable. The authors evaluated whether transcutaneous carbon dioxide partial pressure (Ptcco2) monitoring during apnea test can predict that a Paco2 of 60 mmHg has been reached. The authors compared Ptcco2 measured with a transcutaneous ear sensor (V-Sign Sensor, Sentec Digital Monitoring System; SENTEC-AG, Therwil, Switzerland) and Paco2 obtained from arterial blood gas measurements in 32 clinically brain-dead patients. In the first 20 patients, the mean Paco2-Ptcco2 gradient was 0.7 +/- 3.6 mmHg at baseline and 8.7 +/- 7.1 mmHg after 20 min of apnea. Using receiver operating characteristic curve analysis (area under the curve: 0.983 +/- 0.013), the best threshold value of Ptcco2 to predict that a Paco2 of 60 mmHg had been reached was 60 mmHg (positive predictive value: 1.00 [0.93-1.00]). In the following 12 patients investigated with use of this Ptcco2 target value of 60 mmHg, the mean duration of the apnea test (11 +/- 4 vs. 20 +/- 0 min; P < 0.001), hypercapnia (74.0 +/- 4.9 vs. 98.3 +/- 20.0 mmHg; P < 0.001), acidosis (pH: 7.18 +/- 0.06 vs. 7.11 +/- 0.08; P < 0.001), and decrease in arterial oxygen partial pressure (-47 +/- 44 vs. -95 +/- 89; P < 0.05) at the end of the test were reduced as compared with the 20-min apnea test group. During the apnea test in brain-dead patients, a Ptcco2 of 60 mmHg accurately predicts that a Paco2 of 60 mmHg has been reached. This may allow a reduction in the duration of the apnea test and consecutively limit occurrence of complications.

Prospective, Randomized, Placebo‐controlled Study of the Effect of TENS on Postthoracotomy Pain and Pulmonary Function

We investigated the efficacy of transcutaneous electrical nerve stimulation (TENS) for postthoracotomy pain control in a prospective, randomized, double-blind, placebo-controlled study. We studied two groups of patients undergoing posterolateral thoracotomy. In group 1, TENS was used postoperatively on 60 patients for 5 days. Group 2 contained 56 patients without TENS. In both groups a visual analog scale (VAS) was used to indicate if analgesia was needed. When the VAS was higher than 4, an analgesic was administered. We observed the forced expiratory volume in 1 second (FEV(1)), the forced vital capacity (FVC), partial arterial oxygen pressure (PaO2), partial arterial carbon dioxide pressure (PaCO2), and how many doses of analgesia were given at postoperative 0 (extubation time), 2, 6, 12, 24, 48, 72, and 120 hours. TENS was not employed in patients with cardiac or neurologic disease. In group 1, TENS reduced the need to administer opioids during the 5-day postoperative period. This result is statistically significant (P = 0.013). Additionally, following the sixth postoperative hour, TENS increased the spirometric breath function. The FEV1, FVC, and PaO2 were high and PaCO2 was low when the first group is compared to the second. All these results are statistically significant (P = 0.012, P = 0.01, P = 0.024, and P = 0.02 respectively). We observed that TENS produced no evidence of side effects or intolerance in the patients of group 1. TENS is thus beneficial for pain relief following thoracotomy and has no side effects. Consequently, the routine use of TENS following thoracic surgery is recommended.

Zacopride and 8-OH-DPAT reverse opioid-induced respiratory depression and hypoxia but not catatonic immobilization in goats

Neurophysiological studies have shown that serotonergic ligands that bind to 5-HT1A, 5-HT7, and 5-HT4 serotonin receptors in brain stem have beneficial effects on respiratory neurons during opioid-induced respiratory depression. The effect of these ligands on respiratory function and pulmonary performance has not been studied. We therefore examined the effects of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), an agonist of 5-HT1A and 5-HT7 receptors, and zacopride, an agonist of 5-HT4 receptors, to establish whether these ligands would reverse opioid-induced respiratory depression and hypoxia without affecting the immobilizing properties of the opioid drug etorphine. When etorphine was used to sedate and immobilize goats, it significantly decreased respiratory rate (P = 0.013), percent hemoglobin oxygen saturation (P < 0.0001), and arterial oxygen partial pressure [Pa(O2); F(10,70) = 5.67, P < 0.05] and increased arterial carbon dioxide partial pressure [F(10,70) = 3.87, P < 0.05] and alveolar-arterial oxygen partial pressure gradient [A-a gradients; F(10,70) = 8.23, P < 0.0001]. Zacopride and 8-OH-DPAT, coadministered with etorphine, both attenuated the effects of etorphine; respiration rates did not decrease, and percent hemoglobin oxygen saturation and Pa(O2) remained elevated. Zacopride decreased the hypercapnia, indicating an improvement in ventilation, whereas 8-OH-DPAT did not affect the hypercapnia and, therefore, did not improve ventilation. The main beneficial effect of 8-OH-DPAT was on the pulmonary circulation; it improved oxygen diffusion, indicated by the normal A-a gradients, presumably by improving ventilation perfusion ratios. Neither zacopride nor 8-OH-DPAT reversed etorphine-induced catatonic immobilization. We conclude that serotonergic drugs that act on 5-HT1A, 5-HT7, and 5-HT4 receptors reverse opioid-induced respiratory depression and hypoxia without reversing catatonic immobilization.

Comparative study of three intramuscular anaesthetic combinations (medetomidine/ketamine, medetomidine/fentanyl/midazolam and xylazine/ketamine) in rabbits

ObjectiveTo compare the quality of surgical anaesthesia and cardiorespiratory effects of three intramuscular (IM) anaesthetic combinations in rabbits. Study designProspective randomized cross-over experimental study. AnimalsNineteen adult female chinchilla mixed-bred rabbits weighing 3.9 ± 0.8 kg. MethodsRabbits were given one of three IM anaesthetic combinations: 0.25 mg kg−1 medetomidine and 35.0 mg kg−1 ketamine (M–K), 0.20 mg kg−1 medetomidine and 0.02 mg kg−1 fentanyl and 1.0 mg kg−1 midazolam (M–F–Mz) and 4.0 mg kg−1 xylazine and 50 mg kg−1 ketamine (X–K). The effects of anaesthesia on nociceptive reflexes, circulatory and respiratory function were recorded. Statistical analyses involved repeated measures anova with paired Student's t-test applied post hoc. P-values <0.05 were considered as significant. ResultsReflex loss was most rapid and complete in M–K recipients, whereas animals receiving M–F–Mz showed the longest tolerance of endotracheal intubation (78.1 ± 36.5 minutes). Loss of righting reflex was significantly most rapid (p < 0.05) in the X–K group (114.7 ± 24.0 minutes). Surgical anaesthesia was achieved in 16 of 19 animals receiving M–K, in 14 animals receiving M–F–Mz, and in seven animals with X–K, but only for a short period (7.1 ± 11.6 minutes). This was significantly (p < 0.001) shorter than with M–K (38.7 ± 30.0 minutes) and M–F–Mz (31.6 ± 26.6 minutes). Heart rates were greatest in X–K recipients; lowest HR were seen in animals receiving M–F–Mz. Mean arterial blood pressure was significantly higher (about 88 mmHg) during the first hour in the M–K group. During recovery, the greatest hypotension was encountered in the X–K group; minimum values were 53 ± 12 mmHg. Six of 19 animals in the M–F–Mz group showed a short period of apnoea (30 seconds) immediately after endotracheal intubation. Respiratory frequency was significantly lower in this group (p < 0.001). Highest values for arterial carbon dioxide partial pressures (PaCO2) (6.90 ± 0.87 kPa; 52.5 ± 6.5 mmHg) occurred after induction of anaesthesia in group M–F–Mz animals. There was a marked decrease in PaO2 in all three groups (the minimum value 5.28 ± 0.65 kPa [39.7 ± 4.9 mmHg] was observed with M–K immediately after injection). Arterial PO2 was between 26.0 and 43.0 kPa (196 and 324 mmHg) in all groups during O2 delivery and decreased – but not <7.98 kPa – on its withdrawal. Immediately after drug injection, pHa values fell in all groups, with lowest values after 30 minutes (7.23 ± 0.03 with M–K, 7.28 ± 0.05 with M–F–Mz, and 7.36 ± 0.04 with X–K). The X–K animals showed significantly (p < 0.001) higher pH values than medetomidine recipients. During 1 hour of anaesthesia pH values in the medetomidine groups remained below those of the X–K group. ConclusionsSurgical anaesthesia was induced in most animals receiving medetomidine-based combinations. Arterial blood pressure was maintained at baseline values for about 1 hour after M–K. Transient apnoea occurred with M–F–Mz and mandates respiratory function monitoring. Oxygen enrichment of inspired gases is necessary with all three combinations. Endotracheal intubation is essential in rabbits receiving M–F–Mz. Clinical relevanceThe quality of surgical anaesthesia was greatest with M–K. All combinations allowed recoveries of similar duration. It is theoretically possible to antagonize each component of the M–F–Mz combination.

Normothermic Cardiopulmonary Bypass in a Patient With Moyamoya Disease

A B n OYAMOYA DISEASE (MMD), a relatively common occlusive cerebrovascular disorder in Asian patients,1-3 ften causes cerebral stroke in response to changes in blood ressure, arterial carbon dioxide partial pressure (PaCO2), or ody temperature.4-9 Performance of cardiopulmonary bypass CPB) can be challenging in these patients. Therefore, the uthors present a normothermic CPB case in a patient with MD.

Evaluation of a New Combined Transcutaneous Measurement of Pco2/Pulse Oximetry Oxygen Saturation Ear Sensor in Newborn Patients

Arterial oxygen saturation (Sao(2)) and arterial carbon dioxide partial pressure (Paco(2)) are 2 of the most important respiratory parameters in the treatment of critically ill neonates. Noninvasive monitoring of these parameters is desirable for continuous estimating of the respiratory status and reducing blood loss because of repeated blood gas analyses. Transcutaneous measurement of Pco(2) (Ptcco(2)) represents a simple and noninvasive technique for continuous monitoring of ventilation. However, sensor preparation, positioning, taping, and repeated changes of the sensor location make the handling difficult and complicate its use in the neonatal care unit. Recently, a new sensor for combined assessment of pulse oximetry oxygen saturation (Spo(2)) and Ptcco(2) has been introduced (TOSCA Monitor; Linde Medical Sensors, Basel, Switzerland). The monitor combines pulse oximetry and Ptcco(2) measurement in a single ear sensor, which works at 42 degrees C to enhance blood flow in capillaries below the sensor. In a prospective, open, nonrandomized study of 60 ill neonates, the new ear sensor for combined assessment of Spo(2) and Ptcco(2) at 42 degrees C was tested. The sensor was adapted to the ear of a neonate with a Varihesive layer (Conva Tec; Princeton, NJ). Data obtained from the ear sensor were compared with Spo(2 Finger/Heel), Sao(2), and Paco(2) obtained from arterial blood gas in 30 patients and with a capillary blood gas in an additional 30 patients using Bland Altman bias analysis. Data are presented as median (range). The postconceptional age of the patients was 38.3 weeks (range: 28 5/7-40 5/7) in the arterial group and 37.9 weeks (range: 29 6/7-41 0/7) in the capillary group. Age of the newborns studied was 3.5 days (range: 1-28) in the arterial blood sample group (n = 30) and 6 days (range: 2-28) in the capillary blood sample group (n = 30). Patient weight was 3.02 kg (range: 1.5-4.5) in the arterial group and 2.76 kg (range: 1.0-3.71) in the other group. Three patients had weights of <1500 g. Twenty-one of 60 patients were conventionally ventilated, 4 patients received high-frequency oscillation, and 35 were not ventilated. Mean difference (bias) and precision (2 SD of the mean difference) between Ptcco(2 TOSCA) and Paco(2) were -0.44 kPa (-3.21 mm Hg) and 0.82 kPa (6.02 mm Hg) and between Ptcco(2 TOSCA) and Pcapco(2) were -0.09 kPa (-0.67 mm Hg) and 1.11 kPa (8.07 mm Hg), respectively. Spo(2) assessment by the TOSCA revealed slightly higher values compared with Sao(2) (bias: -0.48%), whereas Spo(2) (Finger/Heel) values were slightly lower than Sao(2) (bias: 0.52%). The TOSCA monitor with the ear sensor adapted to ears of neonates allows reliable estimation of Sao(2) and Paco(2). A potential benefit is the reduction in motion artifacts because of less head movement in newborns and that only a single cable leads form the patient to the monitor. In addition, the sensor is not removed for chest radiograph or for nursing the infant on his or her parent's lap. Long-term studies in a large population with continuous measurements are required to confirm these preliminary findings and to elucidate the benefits in detection of respiratory deterioration and the potential side effects of this sensor.

Respiratory compliance but not gas exchange correlates with changes in lung aeration after a recruitment maneuver: an experimental study in pigs with saline lavage lung injury

IntroductionAtelectasis is a common finding in acute lung injury, leading to increased shunt and hypoxemia. Current treatment strategies aim to recruit alveoli for gas exchange. Improvement in oxygenation is commonly used to detect recruitment, although the assumption that gas exchange parameters adequately represent the mechanical process of alveolar opening has not been proven so far. The aim of this study was to investigate whether commonly used measures of lung mechanics better detect lung tissue collapse and changes in lung aeration after a recruitment maneuver as compared to measures of gas exchangeMethodsIn eight anesthetized and mechanically ventilated pigs, acute lung injury was induced by saline lavage and a recruitment maneuver was performed by inflating the lungs three times with a pressure of 45 cmH2O for 40 s with a constant positive end-expiratory pressure of 10 cmH2O. The association of gas exchange and lung mechanics parameters with the amount and the changes in aerated and nonaerated lung volumes induced by this specific recruitment maneuver was investigated by multi slice CT scan analysis of the whole lung.ResultsNonaerated lung correlated with shunt fraction (r = 0.68) and respiratory system compliance (r = 0.59). The arterial partial oxygen pressure (PaO2) and the respiratory system compliance correlated with poorly aerated lung volume (r = 0.57 and 0.72, respectively). The recruitment maneuver caused a decrease in nonaerated lung volume, an increase in normally and poorly aerated lung, but no change in the distribution of a tidal breath to differently aerated lung volumes. The fractional changes in PaO2, arterial partial carbon dioxide pressure (PaCO2) and venous admixture after the recruitment maneuver did not correlate with the changes in lung volumes. Alveolar recruitment correlated only with changes in the plateau pressure (r = 0.89), respiratory system compliance (r = 0.82) and parameters obtained from the pressure-volume curve.ConclusionA recruitment maneuver by repeatedly hyperinflating the lungs led to an increase of poorly aerated and a decrease of nonaerated lung mainly. Changes in aerated and nonaerated lung volumes were adequately represented by respiratory compliance but not by changes in oxygenation or shunt.