Transcutaneous PCO2 Research Articles

Flap Monitoring by Transcutaneous PO2 and PCO2: Importance of Transcutaneous PCO2 in Determining Follow-up Treatment for Compromised Free Flaps

The authors conducted a two-part study to determine whether transcutaneous oxygen pressure (TcPO (2)) and transcutaneous carbon dioxide pressure (TcPCO (2)) can be used to monitor flap viability after transplantation. The first part was an animal study in which TcPO (2) and TcPCO (2) were measured in 10 epigastric island flaps subjected to arterial or venous ischemia. The second part was a clinical study in which both were measured in 27 free skin flaps. In the experimental study, TcPO (2) decreased to nearly 0 mmHg after 10 minutes of arterial and venous ischemia. TcPCO (2) increased to 100 mmHg after 60 minutes of either type of ischemia. In the clinical study, congestion was suspected in six flaps on the basis of clinical signs alone. Three congested flaps with TcPCO (2) more than 90 mmHg were selected for intervention. The remaining three congested flaps, with TcPCO (2) 80 mmHg or less, survived completely without further treatment. The TcPO (2) of all treated flaps and of the six flaps not requiring further treatment was 0 mmHg. Results of experimental study indicate that TcPO (2) is more sensitive than TcPCO (2) to flap ischemia. However, results of clinical study suggest that it is very hard to distinguish congested flaps from healthy flaps by TcPO (2) alone. The authors believe that a congested flap with a TcPCO (2) more than 90 mmHg requires further treatment.

Effects of non‐invasive pressure support ventilation (NI‐PSV) on ventilation and respiratory effort in very low birth weight infants

Nasal continuous positive airway pressure (NCPAP) is used to provide support to non-intubated infants, but it often fails. Pressure support ventilation (PSV) is a mode of synchronized ventilation that can supplement the spontaneous breathing effort, but it is unknown if it is effective in non-intubated very low birth weight (VLBW) infants. To compare the acute physiological effects of non-invasive PSV (NI-PSV) versus NCPAP on tidal volume (V(T)), minute ventilation (V(E)), gas exchange, breathing effort, and chest wall distortion in VLBW infants. Stable preterm infants of birth weight less 1,250 g were studied during consecutive 2 hr periods of NCPAP and NI-PSV in random sequence. VT, V(E), and thoraco-abdominal synchrony were measured using respiratory inductance plethysmography. Breathing effort was measured by esophageal manometry. Gas exchange was measured by pulse oximetry and transcutaneous PCO2. Fifteen infants of birth weight (mean +/- SD) 808 +/- 201 g and 25.9 +/- 1.8 weeks gestational age were studied while on NCPAP 5.3 +/- 0.6 cm H2O and on NI-PSV with 7.9 +/- 1.3 cm H2O above NCPAP of pressure support. There were no differences in VT, V(E), PCO2 or hypoxemia episodes. Peak and minute inspiratory effort were significantly reduced in NI-PSV mode as compared to NCPAP. There was a significant reduction in indices of chest wall asynchrony in NI-PSV mode. When compared to NCPAP, NI-PSV did not increase minute ventilation, but it effectively unloaded the patient's respiratory pump as indicated by a lower inspiratory effort and reduced chest wall distortion.

Improvement of Microcirculation and Healing of Venous Hypertension and Ulcers With Crystacide ®: Evaluation With a Microcirculatory Model, Including Free Radicals, Laser Doppler Flux, and PO2/PCO2Measurements

In 32 patients with chronic venous insufficiency and venous hypertension associated with ulcerations, the effects of the local application of a hydrogen peroxide cream (Crystacide) applied onto the skin was evaluated using a complex, proportional, microcirculatory model to assess and quantify venous microangiopathy after local treatment. A comparative group treated without Crystacide was included. Laser Doppler flowmetry was used to assess skin perfusion (flux and venoarteriolar response) in association with transcutaneous PO2 and PCO2 measurements. Local plasma free radicals were evaluated in the area surrounding the venous ulcer using the D-Roms test. Crystacide was applied around and on the ulcer for 10 days. Crystacide was more effective than the control treatments. PO2 was increased (improved, P < .05), and plasma free radicals, PCO2, and laser Doppler flowmetry were decreased (improving toward normal values, P < .05). Also, the ulcerated area was significantly smaller at 10 days in the Crystacide group in comparison with controls (P < .05). In the proportional microcirculatory model, all parameters indicated an important level of improvement significantly larger than in controls. In conclusion, in chronic venous insufficiency and venous ulcerations, local treatment with Crystacide (10 days) improves the microcirculation and decreases skin free radicals, thus improving healing.

Speaking-Related Dyspnea in Healthy Adults

To reveal the qualities and intensity of speaking-related dyspnea in healthy adults under conditions of high ventilatory drive, in which the behavioral and metabolic control of breathing must compete. Eleven adults read aloud while breathing different levels of inspired carbon dioxide (CO(2)). After the highest level, participants provided unguided descriptions of their experiences and then selected descriptors from a list. On a subsequent day, participants read aloud while breathing high CO(2) as before, then rated air hunger, physical exertion, and mental effort (with definitions provided). Recordings were made of ventilation (with respiratory magnetometers), end-tidal partial pressure of CO(2), transcutaneous PCO(2), oxygen saturation, noninvasive blood pressure, heart rate, and the speech signal. Unguided descriptions were found to reflect the qualities of air hunger, physical exertion (work), mental effort, and speech-related observations. As CO(2) stimulus strength increased, participants experienced increased perception of air hunger, physical exertion, and mental effort. Simultaneous increases were observed in ventilation, tidal volume, end-inspiratory and end-expiratory volumes, expiratory flow during speaking, nonlinguistic junctures, and nonspeech expirations. Two qualities of speaking-related dyspnea--air hunger and physical exertion--are the same as those reported for many other types of nonspeech dyspnea conditions and, therefore, may share the same physiological mechanisms. The mental effort quality associated with speaking-related dyspnea may reflect a conscious drive to balance speech requirements and ventilatory demands. These findings have implications for developing better ways to evaluate and manage clients with respiratory-based speech problems.

Validation study of a new transcutaneous PCO2 measurement system using an automatic blood gas controller in healthy subjects and clinical usefulness of a new transcutaneous PCO2 measurement system for patients

Validation study of a new transcutaneous PCO₂ measurement system using an automatic blood gas controller in healthy subjects and clinical usefulness of a new transcutaneous PCO₂ measurement system for patients

The Use of Transcutaneous Pco2 to Titrate Hypocapnia and Reduce Pulmonary Vascular Resistance During Mitral Valve Replacement in a Patient with Severe Pulmonary Hypertension

The Use of Transcutaneous Pco2 to Titrate Hypocapnia and Reduce Pulmonary Vascular Resistance During Mitral Valve Replacement in a Patient with Severe Pulmonary Hypertension

Transcutaneous arterial carbon dioxide pressure monitoring in critically ill adult patients

To evaluate the accuracy of transcutaneous PCO(2) (PtcCO(2)) as a surrogate for arterial PCO(2) (PaCO(2)) in a cohort of adult critically ill patients in a medical intensive care unit (ICU). Prospective observational study comparing paired measures of transcutaneous and arterial PCO(2). A 26-bed medical ICU. Fifty ICU patients monitored with a SenTec Digital Monitor placed at the ear lobe over prolonged periods. A total of 189 paired PCO(2) measures were obtained. Twenty-one were excluded from analysis, because profound skin vasoconstriction was present (PCO(2) bias =-10.8+/-21.8 mmHg). Finally, 168 were analysed, including 137 obtained during mechanical ventilation and 82 under catecholamine treatment. Body temperature was below 36 degrees C for 27 measurements. Mean duration of monitoring was 17+/-17 h. The mean difference between PaCO(2) and PtcCO(2) was -0.2+/-4.6 mmHg with a tight correlation (R(2)=0.92, p>0.01). PCO(2) bias did not significantly change among three successive measurements. Changes in PaCO(2) and in PtcCO(2) between two blood samples were well correlated (R(2)=0.78, p>0.01). Variations of more than 8 mmHg in PtcCO(2) had 86% sensitivity and 80% specificity to correctly predict similar changes in PaCO(2) in the same direction. Catecholamine dose or respiratory support did not affect PtcCO(2) accuracy. Hypothermia has only a small effect on accuracy. No complication related to a prolonged use of the sensor was observed Transcutaneous PCO(2) provides a safe and reliable trend-monitoring tool, provided there is no major vasoconstriction.

Transcutaneous Pco2 monitoring in critically ill adults: Clinical evaluation of a new sensor*

In critically ill patients, arterial blood gas analysis is the gold standard for evaluating systemic oxygenation and carbon dioxide partial pressure. A new miniaturized carbon dioxide tension Pco2-Spo2 single sensor (TOSCA, Linde Medical Sensors AG, Basel, Switzerland) continuously and noninvasively (transcutaneously) monitors both Paco2 and oxygen saturation by pulse oximetry (Spo2). The present study was designed to investigate the usability and the accuracy of this device in critically ill patients. Prospective clinical investigation. A 20-bed, university-affiliated, surgical intensive care unit. Patients admitted after major surgery, multiple trauma, or septic shock equipped with an arterial catheter. The heated (42 degrees C) sensor was fixed at the earlobe using an attachment clip. Transcutaneous Pco2 (TcPco2) measurements were correlated with Paco2 values (measured using a blood gas analyzer). In addition, the differences between Paco2 and TcPco2 values were evaluated using the method of Bland-Altman. We studied 55 patients, aged 18-80 (mean 57 +/- 15) yrs. A total of 417 paired measurements were compared. Correlation between TcPco2 and Paco2 was r = .86 (p < .01) in the Paco2 range of 24-101 mm Hg. Mean bias (+/-sd) between the two methods of measurement (Bland-Altman analysis) was 1.2 +/- 6.0 mm Hg with TcPco2 slightly overestimating arterial carbon dioxide tension. Nineteen percent of the measured values were outside of the acceptable clinical range of agreement of +/-7.5 mm Hg. The present study suggests that Paco2 can be acceptably assessed by measuring TcPco2 using the TOSCA Pco2-Spo2 sensor.

Errors in monitoring transcutaneous Pco2 on the ear*

Jikei University School of Medicine, Tokyo, Japan(Kagawa) Department of Anesthesia, UCSF, San Francisco, CA(Severinghaus)

Continuous noninvasive monitoring of transcutaneous blood gases for a stable and persistent BOLD contrast in fMRI studies in the rat

The physiological status of anesthetized rats greatly influences blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI). Monitoring of physiological parameters, particularly partial pressure of carbon dioxide (pCO(2)) levels in the blood, is therefore an important part in the design and performance of reliable fMRI experiments. In this paper, the use of a transcutaneous blood gas analyzing system in rats as a completely noninvasive and MR-compatible method is demonstrated. It was successfully used to monitor continuously pCO(2) values, as an effective alternative to more invasive methods, such as analysis of repetitive arterial blood samples or endtidal capnography. In addition, the transcutaneous pCO(2) of rats anesthetized for long periods was studied using different anesthetic substances and experimental protocols. On-line monitoring of pCO(2) values permitted experimental conditions to be established in which the animals remained normocapnic and during which a robust and consistent BOLD contrast could be observed upon somatosensory forepaw stimulation. A transcutaneous pCO(2) threshold level was defined for the reliable detection of a stimulus-dependent BOLD response.

Cardiovascular Support for Low Birth Weight Infants and Cerebral Hemodynamics: A Randomized, Blinded, Clinical Trial

Maintaining adequate organ blood flow is the target of vasopressor treatment, but the impact of these measures on cerebral perfusion has not yet been evaluated systematically in a randomized, blinded, clinical trial. To explore the effects on brain hemodynamics of 2 different inotropic agents used to treat systemic hypotension among low birth weight (LBW) infants. Newborns of <1501 g birth weight or <32 weeks' gestational age, with a mean blood pressure (MBP) lower than gestational age in the first 24 hours of life, were assigned randomly to receive dopamine (DP) (2.5, 5, 7.5, or 10 microg/kg per minute; n = 28) or epinephrine (EP) (0.125, 0.250, 0.375, or 0.5 microg/kg per minute; n = 32), at doses that were increased in a stepwise manner every 20 minutes until the optimal MBP (MBP-OP) was attained and maintained. Continuous monitoring of quantitative changes in cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, cerebral intravascular oxygenation (HbD) (the difference between oxyhemoglobin and deoxyhemoglobin), and cerebral blood volume (CBV) were assessed with near-infrared spectroscopy. MBP, heart rate, transcutaneous Pco2 and Po2, and peripheral oxygen saturation were recorded continuously and analyzed at baseline, 20 minutes after each dose increase (T1, T2, T3, and T4) until MBP-OP was reached, and then every 20 minutes up to 1 hour of stable MBP-OP. Fifty-nine infants were considered for analysis. Patients did not differ in birth weight or gestational age (1008 +/- 286 g and 28.3 +/- 2.3 weeks, respectively, in the DP group and 944 +/- 281 g and 27.7 +/- 2.4 weeks in the EP group). Studies were performed at a mean age of 5.3 +/- 3.7 hours of life (range: 2-16 hours). MBP-OP was attained for 96.3% of patients with DP and 93.7% with EP (responders). For those patients, MBP, heart rate, CBV, and HbD increased from baseline throughout the study period, with no differences between groups except for a higher heart rate with EP. Changes in MBP were correlated significantly with changes in HbD. Dose escalation of drugs produced no differences between groups in the behavior of the variables, except for a greater heart rate with EP from 20 minutes after dose 2 (T2) onward. Drug-induced changes in cerebral hemodynamics varied with gestational age; the EP-induced increase in CBV was greater among less mature patients (<28 weeks), whereas the DP-induced increase in CBV was greater among patients of > or =28 weeks. Among hypotensive LBW infants, cardiovascular support with low/moderate-dose DP or low-dose EP increased cerebral perfusion, as indicated by the increase in both CBV and HbD. Low-dose EP was as effective as low/moderate-dose DP in increasing MBP among LBW infants.

Changes in transcutaneous PCO2 on earlobe represent hypoperfusion characterized by systemic increase in lactate

Changes in transcutaneous PCO2 on earlobe represent hypoperfusion characterized by systemic increase in lactate

Hypoventilation alvéolaire au cours du sommeil et ventilation assistée à domicile

An alveolar hypoventilation physiologically occurs during sleep and more specifically during REM sleep. During obstructive chronic respiratory failures, increases in PaCO2 that are associated with REM sleep can participate to the severity of daytime hypercapnia and in a subgroup of patients lead to an indication of nocturnal non-invasive ventilation (NIV) in association with the long-term oxygen therapy. A REM sleep hypoventilation generally appears during the early course of restrictive chronic respiratory failures. This REM sleep hypoventilation represents one of the most frequent reasons for initiating NIV in restrictive respiratory insufficiencies. Obesity-hypoventilation syndrome (OHS) refers to a hypercapnic chronic respiratory failure in which REM sleep hypoventilation is one of the main determinants. In France, in 2004, OHS is the primary chronic respiratory failure leading to at home NIV. NIV on OHS aims to maintain upper airway patency as sleep apnoea is frequently associated and to allow sufficient alveolar ventilation during REM sleep. Thus, sleep alveolar hypoventilation should be systematically assessed in obese patients and during the time curse evolution of all the chronic respiratory failures. This can be done relatively easily by using nocturnal oximetry concurrently with a transcutaneous PCO2 measurement. The understanding of exact mechanisms underlying abnormal respiratory events occurring during sleep allows optimising adjustments in NIV parameters.

Oxygénothérapie du nouveau-né : matériels de surveillance non invasive

In newborn and premature infants whose lung immaturity entails a limited capacity for O2 detoxification, the use of supplemental oxygen should be continuously and non-invasively monitored. Pulse oximetry and transcutaneous O2 monitoring are the systems most used in the NICU. Major limitations of pulse oximetry are motion artifact, sensitivity to excessive light, cutaneous hypoperfusion, hypothermia, venous congestion, arterio-venous shunting, strong skin pigmentation, anemia and high percentage of abnormal hemoglobin. Alarm habituation is a further major risk. New oxymeters show less motion, artifact and higher accuracy during low oxygen saturation. The accuracy during high oxygen saturation is very dependent on the specific oxymeter model used. Transcutaneous O2 monitoring is usually combined with transcutaneous PCO2 monitoring, hence enabling evaluation of oxygenation as well as ventilation. A major risk of this method is related to the heated electrode sensor, which can induce skin burns. A combined ear sensor for pulse oximetry and PCO2 monitoring seems promising.

Cheyne-Stokes Respiration in Stroke

Central sleep apnea (CSA) and Cheyne-Stokes respiration have been reported in association with stroke, but their pathophysiologic correlates have not been well described. To test the hypotheses that (1) CSA in patients with stroke is associated with nocturnal hypocapnia and (2) in those stroke patients with CSA and with left ventricular (LV) systolic dysfunction, periodic breathing (PB) will have a Cheyne-Stokes respiration pattern in which cycle duration is greater than in those without LV systolic dysfunction. We prospectively performed polysomnography and echocardiography in 93 patients with stroke. CSA was defined as central apneas and hypopneas occurring at a rate of 10 or more per hour of sleep. In patients with CSA, we compared PB cycle duration between those with normal and impaired LV systolic function (LV ejection fraction [LVEF] > 40% and < or = 40%, respectively). CSA was found in 19% of subjects who had lower nocturnal transcutaneous PCO2 (39.3 +/- 0.9 vs. 42.8 +/- 0.8 mmHg, p = 0.015) and a higher prevalence of LVEF of 40% or less (22 vs. 5%, p = 0.043) than stroke patients without CSA. There was no significant difference in stroke location or type between the two groups. In patients with CSA, those with LVEF of 40% or less had a longer PB cycle than those with an LVEF of more than 40% (66.6 +/- 5.6 vs. 46.6 +/- 2.9 seconds, p = 0.006), but had no symptoms of heart failure. In patients with stroke, CSA is associated with hypocapnia and occult LV systolic dysfunction but is not related to the location or type of stroke. The presence of LV systolic dysfunction is associated with a Cheyne-Stokes pattern of hyperpnea.

Nasal Bilevel vs. Continuous Positive Airway Pressure in Preterm Infants

Our aim was to compare the effects of nasal bilevel positive airway pressure (N-BiPAP) and nasal continuous positive airway pressure (N-CPAP) on gas exchange in preterm babies. Twenty preterm infants (mean gestational age, 26.3 weeks; mean weight at study, 1,033 g) were evaluated. Patients received two repeated cycles of N-CPAP alternated with N-BiPAP, for a total of four alternated phases, each phase lasting 1 hr. Transcutaneous PO2 (TcPO2), transcutaneous PCO2 (tcPCO2), pulsoximetry, and respiratory rate were recorded every 15 min. Arterial blood gases and acid-base balance were measured at the beginning of the first study period on baseline CPAP and at the end of the last study period on bilevel positive airway pressure. During the two N-BiPAP phases, a statistically significant (P < 0.001) increase of peripheral oxygen saturation and tcPO2, and a significant (P < 0.001) reduction of tcPCO2 and respiratory rate, were noted as compared to the two N-CPAP periods. In addition, a significant improvement of PO2 (P < 0.003) and a reduction of PCO2 were noted at the end of the test (P < 0.02). In conclusion, N-BiPAP, as compared to N-CPAP, improved gas exchange in preterm infants.

Transtracheal High-Flow Insufflation Supports Spontaneous Respiration in Chronic Respiratory Failure

Transtracheal insufflation of oxygen-enriched air at a high flow rate has been proposed to support ventilation. The purpose of this study was to investigate the physiologic effects of high-flow insufflation unobtrusively with a respiratory inductive plethysmograph in patients with chronic respiratory failure. Using a respiratory inductive plethysmograph also permitted monitoring of end-expiratory lung volume, and respiratory variables could be quantified independently of the tracheal bias flow. Prospective randomized comparison of low-flow vs high-flow transtracheal insufflation. Pulmonary division of a tertiary teaching hospital. Fourteen spontaneously breathing outpatients with chronic hypoxemic respiratory failure carrying a transtracheal catheter for long-term oxygen therapy. Oxygen-enriched air (fraction of inspired oxygen, 0.37) at 15 L/min and oxygen at 1.5 L/min were transtracheally administered for 1 h each. The breathing pattern and the end-expiratory lung volume were monitored by inductive plethysmography along with pulse oximetry and transcutaneous PCO2. Arterial blood gases were also analyzed at the end of the hour of both low-flow and high-flow insufflation. High-flow insufflation decreased the mean (+/- SEM) minute ventilation (Ve) by 20% from 8.37 +/- 0.49 to 6.66 +/- 0.57 L/min, the mean respiratory rate from 19.2 +/- 0.9 to 15.7 +/- 1.0 breaths/min, while mean expiratory time increased from 2.0 +/- 0.1 to 2.8 +/- 0.2 s, and end-expiratory lung volume decreased by 0.55 +/- 0.15 L compared to low-flow oxygen insufflation (p < 0.05 for all comparisons). Mean arterial and transcutaneous PCO2 decreased from 45 +/- 1 to 43 +/- 1 mm Hg and from 54 +/- 2 to 53 +/- 2 mm Hg, respectively (p < 0.05 in both instances), while arterial PaO2 and oxygen saturation did not change. High-flow transtracheal insufflation of oxygen-enriched air assists ventilation by reducing Ve without compromising gas exchange and by reducing end-expiratory lung volume, possibly through the reversal of dynamic hyperinflation.

Initial Transcutaneous Pco2 Overshoot with Ear Probe at 42°C

To investigate an unexpectedly high initial skin CO2 pressure with a new small earlobe probe* heated to 42 degrees C containing both transcutaneous (tcPCO2) and pulse oximeter saturation (SpO2) sensors. The probe was mounted on the ear lobe of six patients during abdominal or thoracic surgery and on several awake volunteers. The probe was mounted on a cheek or forearm in two other volunteers. Patients were artificially ventilated under general anesthesia at constant end-expiratory PCO2. In patients, at 8 +/- 3 min after mounting, tcPCO2 peaked 5 mmHg higher than its final value (p = 0.0067, n = 6, paired t-test). After 25 min, tcPCO2 was not different from PaCO2 (arterial). Similar overshoots were recorded with this device when mounted on the arm or cheek and with a standard transcutaneous PCO2 probe set to 42 degrees C, mounted on the ear lobe, arm or chest of awake volunteers. In two volunteers, we found that heating the sensor to 45 degrees C for the first 15 min on the ear, and then decreasing it to 42 degrees C prevented overshoot, and provided valid tcPCO2 data 3 - 5 min after application of the sensor. A temperature of 42 degrees C may increase local skin temperature and metabolism before vasodilating more remote arteriolar control of sub-sensor capillary flow. We suggest that transcutaneous PCO2 probes be initially set to 44 - 45 degrees C for 5 - 15 min to induce prompt vasodilation to prevent this overshoot and then reduced to 42 degrees C to avoid skin thermal injury in case of long-term application.

202 Cerebral Haemodynamics and Lung Mechanics in Preterm Infants During Synchronized Intermittent Mandatory Ventilation (SIMV) and Synchronized Intermittent Positive Pressure Ventilation (SIPPV), with and Without Volume Guaranteed (VG)

Background: Various techniques of mechanical ventilation can affect cerebral haemodynamics and oxygenation in preterm infants. Few studies have assessed cerebral haemodynamics and oxygenation during different modalities of patient triggered ventilation (PTV) in preterm infants.Aim: To study cerebral haemodynamics and oxygenation, by Near Infrared Spectroscopy (NIRS) and Echo-Doppler, during SIMV and SIPPV, with and without VG.Methods: Ten preterms (means±SD: BW=1316±666 g; GA=28.8±4.2 wks) with RDS were studied at 7.7±7.3 days of life, in SIPPV±VG and SIMV±VG, with VG set at 5 ml/kg. Each ventilation modality was used for 30 minutes in a random sequence. Concentration of cerebral oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb) and total haemoglobin (tHb) and Tissue Oxygenation Index (TOI) were continuously monitored by NIRS. At the beginning and at the end of each ventilation modality the Resistance Index (RI) in the Anterior Cerebral Artery was assessed by Echo-Doppler. Heart Rate (HR), Respiratory Rate (RR), Inspired Oxygen Concentration (FiO2), transcutaneous oxygen saturation (SaO2) and transcutaneous PCO2 (PtcCO2) were continuously monitored. Mean Airway Pressure (MAP), Mean Arterial Blood Pressure (MABP), Tidal Volume (Vt), and Compliance of the respiratory system (Crs) were measured at 5 minutes intervals. The results were expressed as means ± SD. Differences between the 4 ventilation modalities were considered statistically significant for p <0.05 by the Student's t test for paired values.Results: O2Hb, HHb, tHb and IR were stable and similar in the 4 ventilation modalities; oscillations never exceeded 5% of baseline values. TOI was always ± 60%. No differences were found in RR, Vt, HR, SaO2 and PtcCO2. Crs was below normal values in all modalities (SIMV=0.5±0.1; SIMV+VG=0.6±0.2; SIPPV=0.4±0.1; SIPPV+VG=0.5±0.1 ml/cmH2O/kg) and was slightly higher in SIMV than in SIPPV (p<0.02).Conclusions: These preliminary data suggest that acute changes in cerebral haemodynamics and oxygenation and in lung mechanics are minimal during PTV with low VG, irrespective of the type of ventilation used (SIMV or SIPPV ± VG).

245 Prediction of Cerebral Outcome at 24 Months in Preterm Infants by NIRS in The First 24 Hours After Birth

Background: The prognostic value of cerebral NIRS in preterm infants remains controversial. Impaired autoregulation of brain perfusion quantified as high coherence between oscillations of cerebral intravascular oxygenation and arterial blood pressure in sick preterm infants has been related to intracerebral haemorrhage and hypoxic ischemic encephalopathy (Tsuji 2000).Aim: To compare cerebral NIRS parameters during the first 24 hours of life in sick preterm infants with cerebral ultrasound findings and neurological outcome at 9 and 18 months. Patients: 31 preterm infants admitted to our NICU for respiratory distress. Gestational age ranged from 26 1/7 to 32 2/7 weeks (median: 27 2/7) and birth weight from 690 to 2440 g (median: 1030 g).Methods: Total haemoglobin (tHb) and oxygenaton index (OI) was measured with NIRS using a sensor placed frontoparietally at three time points: 1) within first 6 h, 2) 12 - 16 h and 3) 24–28 h. Heart rate, arterial blood pressure (MAP), arterial oxygen saturation and transcutaneous pO2 and pCO2 were recorded simultaneously. Cerebral ultrasound examination (Acuson 128XP, 7 MHz transducer) was performed at 12 to 24 hours of life, at days 3, 7, 14 and every two weeks until discharge. Psycho-motor-developmental index (Bayley, PDI), mental-developmental index (MDI) and the neurological status were assessed in all surviving infants at nine and 18 months corrected for prematurity. A late follow-up examination was done between 3 and 10 years.Results: Nine infants died within the first 10 days. Nine months after expected date of birth 10 out of 20 survivors were classified abnormal with MDI or PDI <85. (Parents of two infants refused the examination). At 18 months corrected for prematurity 3 out of 18 infants had abnormal neurological status. Coherence between OI or tHb and MAP or heart rate did not change significantly between the three session. Intact survivors had significantly higher coherence with 0.6 (IQR 0.38– 0.84) than survivors with abnormal neurological status 0.38 (IQR 0.24–0.52) and deaths 0.28 (IQR 0.24–0.52).Conclusion: In contrast to previous studies low coherencies in the first 24 hours were associated with intraventricular haemorrhage, death or abnormal neurological outcome at 18 months or later. Consistent predictive results are obtained with coherencies between MAP or HR and OI or tHb analysed at 6, 12 and 24 hours after birth.