Changes In PaCO2 Research Articles

Position does not affect the optic nerve sheath diameter during laparoscopy.

BackgroundIncrease in intracranial pressure (ICP) is one of the physiologic changes during laparoscopic surgery, which is known to be associated with positional changes. Changes of ICP can be measured directly by invasive method, but ultrasonographic measurement of optic nerve sheath diameter (ONSD) is known to be a rapidly applicable technique for evaluating ICP. The aim of this study is to investigate the change of ONSD according to the positional change during laparoscopic surgery.MethodsFemale patients scheduled to undergo laparoscopic surgery were enrolled. Fifty-seven patients were assigned according to the position during surgery (Group T: gynecological surgery, Trendelenburg position, n = 27 vs. Group RT: laparoscopic cholecystectomy, Reverse trendelenburg position, n = 30). After induction of anesthesia, ONSD, PaCO2, end-tidal carbon dioxide (ETCO2), and mean arterial pressure (MAP) were measured. Parameters were measured at 6 time points during surgery.ResultsThere were no significant differences in the demographic data of patients, procedure time, and anesthesia. After pneumoperitoneum and positional change, ONSD, ETCO2, and MAP increased in both groups until 15 min and returned to the baseline. However, no significant differences in changes of ONSD, PaCO2, ETCO2, and MAP were observed between two groups.ConclusionsONSD during laparoscopic surgery with pneumoperitoneum increased slightly until 15 minutes, but there were no significant differences according to the position. Increases in ICP during laparoscopic surgery with short period of pneumoperitoneum would be small in disregard of position in patients without intracranial pathology.

Transcutaneous continuous carbon dioxide tension monitoring reduced incidence, degree and duration of hypercapnia during combined regional anaesthesia and monitored anaesthesia care in shoulder surgery patients

We studied the impact of transcutaneous continuous carbon dioxide tension (PtcCO2) monitoring on ventilation and oxygenation during monitored anaesthesia care (MAC) in patients scheduled for shoulder surgery with continuous interscalene block. 50 patients were randomised either to the intervention (I-group) or the control (C-group) group. In both groups MAC was performed using target controlled infusion of propofol and remifentanil. MAC regimen was adapted to PtcCO2 values in the I-group, whereas the C-group was blinded for these values. Primary outcome was the incidence, degree and duration of hypoventilation stages. In the I-group and the C-group the mean ± SD [range] of PtcCO2 and PaCO2 was 5.79 ± 0.84 [4.37] and 5.44 ± 0.59 [2.78] kPa, as well as 6.41 ± 1.17 [6.29] and 6.01 ± 0.96 [7.15] kPa. Periods of PtcCO2/PaCO2 > 6.5 kPa were 21.0 ± 35.7/1.2 ± 4.2 min in the I-group and 45.6 ± 40.0/18.6 ± 26.8 min in the C-group. Severe hypercapnia (PtcCO2 and/or PaCO2 > 7.5 kPa) was dected in 3/0 patients of the I-group and in 10/3 patients of the C-group. PtcCO2 and PaCO2 showed a strong correlation (r = 0.78), but only moderate agreement with a mean bias (LOA) of -0.37 (-1.69; +0.95) kPa showing an overestimation of the PaCO2. Sensitivity and specificity of PtcCO2 to detect changes of PaCO2 was 0.94 and 0.56, respectively. In no patient SpO2 or SaO2 values lower than 90% were measured. Despite a moderate agreement between PaCO2 and PtcCO2 the PtcCO2 monitoring significantly reduced incidence, degree and duration of hypercapnia in shoulder surgery patients with MAC.

The use of non-invasive ventilation in very old patients with hypercapnic acute respiratory failure because of COPD exacerbation.

We prospectively enrolled 207 patients (121 were 75 or older and 86 younger than 75) who were admitted to three Respiratory Monitoring Units. The primary outcomes were intubation and mortality rates; the secondary outcomes were changes in arterial blood gases analysis, non-invasive ventilation (NIV) duration and length of hospital stay. Hospital mortality was similar in the two groups, as were intubation rates. The proportion who died in the very old patient group was 19.8% (24/121) vs. 10.4% (9/86) in the younger group. Intubation rate was 10.7% (13/121) in the very old patient group and 11.6% (10/86) in the younger group. The presence of comorbidities, the severity of illness (SAPS II), the level of consciousness, NIV failure (intubation), absolute value of pH prior to NIV, as well as the changes in pH and paCO2 and PaO2 /FiO2 after 2 h of NIV, were the variables associated with higher mortality. Very old patients had significantly higher NIV duration than younger patients (69.0 ± 47.0 vs. 57.0 ± 27.0 h) (p ≤ 0.03) and hospital stays (11.6 ± 3.8 vs. 8.4 ± 1.4) (p ≤ 0.02). The use of NIV in very old patients was effective in many cases. Endotracheal intubation after NIV failure was not efficacious in either group.

Peripheral neuropathy and the risk of cardiovascular events in type 2 diabetes mellitus.

Identifying individuals with diabetes at high risk of cardiovascular disease (CVD) remains challenging. We aimed to establish whether peripheral neuropathy (PN) is associated with incident CVD events and to what extent information on PN may improve risk prediction among individuals with type 2 diabetes. We obtained data for individuals with type 2 diabetes, and free of CVD, from a large primary care patient cohort. Incident CVD events were recorded during a 30-month follow-up period. Eligible individuals had complete ascertainment of cardiovascular risk factors and PN status at baseline. The association between PN and incident CVD events (non-fatal myocardial infarction, coronary revascularisation, congestive cardiac failure, transient ischaemic attack and stroke) was evaluated using Cox regression, adjusted for standard CVD risk factors. We assessed the predictive accuracy of models including conventional CVD risk factors with and without information on PN. Among 13 043 eligible individuals, we recorded 407 deaths from any cause and 399 non-fatal CVD events. After adjustment for age, sex, ethnicity, systolic blood pressure, cholesterol, body mass index, HbA1c, smoking status and use of statin or antihypertensive medication, PN was associated with incident CVD events (HR 1.33; 95% CI 1.02 to 1.75, p=0.04). The addition of information on PN to a model based on standard CVD risk factors resulted in modest improvements in discrimination for CVD risk prediction and reclassified 6.9% of individuals into different risk categories. PN is associated with increased risk for a first cardiovascular event among individuals with diabetes.

Utility of cerebral oxymetry for assessing cerebral arteriolar carbon dioxide reactivity during cardiopulmonary bypass.

Our study evaluated changes in cerebral arterial oxygen saturation (rSO2) during cardiopulmonary bypass (CPB) that were caused by changes in arterial carbon dioxide tension (PaCO2). A group of 126 patients undergoing routine, elective, first-time coronary artery bypass graft surgery (CABG) was entered into a prospective study using bilateral near-infrared spectroscopy (NIRS) before anesthetic induction (T1), after anesthetic induction (T2), and continuing at 5-minute intervals during moderate hypothermic (32°C) CPB. Pump flows were set at 2.5 L/min/m(2) and adjusted to maintain mean arterial pressure (MAP) within 10 mmHg of the MAP recorded at the initial fifth minute of CPB (T3). Thirty-two patients were excluded from data collection because MAP could not be stabilized within the target range of 60-90 mmHg. In the remaining 94 patients, after obtaining steady state flow, MAP, and oxygenation, a trial period of hypocarbia (mean PaCO2 of 30 mmHg) was induced by increasing oxygenator fresh gas flow rate (FGFR) to 2.5 L/min/m(2) (T4). A reciprocal period was then measured at reduced FGFR (0.75 L/min/m(2)) (T5). After 20 minutes of a higher (2.75 L/min/m(2)) (FGFR), mean PaCO2 decreased from a baseline of 38 ± 4 mmHg to 30 ± 2 mmHg. This was associated with a parallel decrease (-10 ± 9%) in mixed cerebral oxygen saturation without alteration of mean arterial oxygen tension (PaO2), lactate, MAP, CPB flow, or other parameters implying increased cerebral oxygen extraction. Parallel changes in PaCO2 and rSO2 occur during CPB when other variables remain constant, and are due to the effects of carbon dioxide on cerebral arterioles. Cerebral oxygen saturation measured by NIRS may be a useful indirect measure of PaCO2 when continuous blood gas analysis is not possible during open-heart surgery. Cerebral oximetry values may be useful measurements for setting an optimum gas flow rate through the oxygenator.

Asupan Karbohidrat, Asupan Lemak dan PaCo2 pada Pasien Kritis

Background:The physiological changes occur deteriorating rapidly on critical patients so that it can lead to death if not quickly and accuratelytreated. Two circumstances that can lead to worsening an organ are hypoxemia and malnutrition. Problems can arise when nutrition administered with inappropriate total energy, such as the provision of excessively carbohydrates cause hipercapnea, hyperglycemia, increased O2 consumption and CO2 production, while low fat intake causes hypoxemia. This research aimed to determine the relationship between carbohydrate and fat intake with changes in PaCO2.Objective : The purpose of this study was to determine the relationship between the intake of carbohydrates and fats with PaCO2 changes in critically ill patients .Method: This researchis observational with cross-sectional researchdesign. The experiment was conducted in the ICU room of Semarang Regional Hospital. Samplesare all subjects who were treated in the ICU room and meet the criteria of inclusion and exclusionand limited in period of 3 weeks. The research subjects were adult age group at least 18 years old male or female with the inclusion criteria of having experienced respiratory failure, using ventilator, not experience shock in the last 24 hours, blood pressure is not hypotension, receiving food through enteral or combination of enteral or parenteral. Its exclusion criteria is patients with complex organ failure clinically diagnostic in 24 hours experienced shock, not fed for≥ 4 hours, with hemoglobin level 8 g/ dL, malnutrition status based on anthropometric TSFexamination. The collected data were age, hemoglobin, blood pressure, TSF, carbohydrate intake, fat intake, changes in PaCO2. Analysis data used Shapiro-Wilk, Pear son Product Moment correlation.Results: The most of carbohydrate intake including in the high category (66.7 %), the majority of fat intake fall in the category of less (58.7 %). The majority of PaCO2 in day 1 and 2 (66.7 % and 50 %) are included in the high category. There was relationship between carbohydrate intake with changes in PaCO2 (p =0,024 r = 0,643). There was relationship between fat intake with changes in PaCO2 (p = 0,046, r = - 0,584).Conclusion: There was relationship between carbohydrate intakes with changes in PaCO2 and there was relationship between fat intake with changes in PaCO2.

Effect of Oxygen-driven Nebulization at Different Oxygen Flows in Acute Exacerbation of Chronic Obstructive Pulmonary Disease Patients

ObjectivesThe aim of this study was to study the effect of oxygen-driven nebulization (ODN) at different oxygen flows on heart rate, respiratory rate, SpO2, SaO2, PaO2, PaCO2 and pH of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients. MethodsAccording to random number table, 9 AECOPD patients were randomly divided into 3 groups, numbered A, B and C and treated with ODN. Oxygen flow of groups A, B and C was 4-5, 6-7 and 8-9L/min, respectively. Heart rate, respiratory rate, SpO2, SaO2, PaO2, PaCO2 and pH were recorded before ODN and 30 minutes after ODN. Statistical differences of data before or after ODN were analyzed by analysis of variance and F-test, whereas data before and after ODN were tested by paired t test. ResultsThere was no significant difference of heart rate, respiratory rate, SpO2, PaO2, PaCO2, SaO2 and pH among 3 groups before ODN or after ODN. The heart rate was increased in all groups after ODN. But significant increase was only present in groups A and C but not in group B. SaO2 was significantly increased in group C after ODN but no statistical difference was observed between before and after ODN in groups A and B. There was no significant change in respiratory rate, SpO2, PaO2, PaCO2, SaO2 and pH between before and after ODN in all groups. ConclusionsOptimal oxygen flow in ODN-treating AECOPD patients may be 6-7L/min.

Influence of cerebrovascular resistance on the dynamic relationship between blood pressure and cerebral blood flow in humans.

We examined the hypothesis that changes in the cerebrovascular resistance index (CVRi), independent of blood pressure (BP), will influence the dynamic relationship between BP and cerebral blood flow in humans. We altered CVRi with (via controlled hyperventilation) and without [via indomethacin (INDO, 1.2 mg/kg)] changes in PaCO2. Sixteen subjects (12 men, 27 ± 7 yr) were tested on two occasions (INDO and hypocapnia) separated by >48 h. Each test incorporated seated rest (5 min), followed by squat-stand maneuvers to increase BP variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis (TFA). Beat-to-beat BP, middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv), and end-tidal Pco2 were monitored. Dynamic pressure-flow relations were quantified using TFA between BP and MCAv/PCAv in the very low and low frequencies through the driven squat-stand maneuvers at 0.05 and 0.10 Hz. MCAv and PCAv reductions by INDO and hypocapnia were well matched, and CVRi was comparably elevated (P < 0.001). During the squat-stand maneuvers (0.05 and 0.10 Hz), the point estimates of absolute gain were universally reduced, and phase was increased under both conditions. In addition to an absence of regional differences, our findings indicate that alterations in CVRi independent of PaCO2 can alter cerebral pressure-flow dynamics. These findings are consistent with the concept of CVRi being a key factor that should be considered in the correct interpretation of cerebral pressure-flow dynamics as indexed using TFA metrics.

Impact of sevoflurane anesthesia on brain oxygenation in children younger than 2 years

To assess the impact of sevoflurane and anesthesia-induced hypotension on brain oxygenation in children younger than 2 years. Inhalational induction with sevoflurane is the most commonly used technique in young children. However, the effect of sevoflurane on cerebral perfusion has been only studied in adults and children older than 1 year. The purpose of this study was to assess the impact of sevoflurane anesthesia on brain oxygenation in neonates and infants, using near-infrared spectroscopy. Children younger than 2 years, ASA I or II, scheduled for abdominal or orthopedic surgery were included. Induction of anesthesia was started by sevoflurane 6% and maintained with an expired fraction of sevoflurane 3%. Mechanical ventilation was adjusted to maintain an endtidal CO2 around 39 mmHg. Brain oxygenation was assessed measuring regional cerebral saturation of oxygen (rSO2 c), measured by NIRS while awake and 15 min after induction, under anesthesia. Mean arterial pressure (MAP) variation was recorded. Hundred and ninety-five children were included. Anesthesia induced a significant decrease in MAP (-27%). rSO2 c increased significantly after induction (+18%). Using children age for subgroup analysis, we found that despite MAP reduction, rSO2 c increase was significant but smaller in children ≤ 6 months than in children >6 months (≤ 6 months: rSO2 c = +13%, >6 months: rSO2 c = +22%; P < 0.0001). Interindividual comparison showed that, during anesthesia at steady-state with comparable CMRO2, rSO2 c values were significantly higher when MAP was above 36 mmHg. And the higher the absolute MAP value during anesthesia was, the higher the rSO2 c was. We observed a rSO2 c variation ≤ 0 in 21 patients among the 195 studied, and the majority of these patients were younger than 6 months (n = 19). No increase or decrease of rSO2 c during anesthesia despite reduction of CMRO2 can be explained by a reduction of oxygen supply. Using the ROC curves, we determined that the threshold value of MAP under anesthesia, associated with rSO2 c variation ≤ 0%, was 39 mmHg in all the studied population (AUC: 0.90 ± 0.02; P < 0.001). In children younger than 6 months, this value of MAP was 33 mmHg, and 43 mmHg in children older than 6 months. Despite a significant decrease of MAP, 1 MAC of sevoflurane induced a significant increase in regional brain oxygenation. But subgroup analysis showed that MAP decrease had a greater impact on brain oxygenation, in children younger than 6 months. According to our results, MAP value during anesthesia should not go under 33 mmHg in children ≤6 months and 43 mmHg in children >6 months, as further changes in MAP, PaCO2 or hemoglobin during anesthesia may be poorly tolerated by the brain.

GAL‐160 is a potent orally bioavailable ventilatory stimulant in rats (873.3)

GAL‐160 is a novel chemoreceptor modulator entering early clinical development as a therapeutic for sleep‐disordered breathing. Here, we describe GAL‐160’s properties as a ventilatory stimulant in rats. The effects of bolus GAL‐160 (0.01 – 10 mg/kg IV) on breathing, mean arterial pressure (MAP) and heart rate (HR, as inferred from pulse rate) were measured using whole‐body plethysmography and blood pressure telemetry in conscious rats. GAL‐160 dose‐dependently increased minute volume (Emax ~400% above baseline; ED50 0.05 mg/kg) by increasing tidal volume and respiratory rate. At the highest dose tested, and in comparison to vehicle‐treated controls GAL‐160 produced no significant changes in mean arterial MAP (7.1 ± 2.3%) or HR (‐8.3 ± 5.7%). GAL‐160 (20 mg/kg PO) increased minute volume (Emax ~ 100% above vehicle) which remained elevated for up to 75 minutes post‐gavage with no effect on MAP (0.1 ± 0.5%) or HR (7.6 ± 0.7%) compared to vehicle. The pharmacokinetic‐pharmacodynamic relationship for GAL‐160 was evaluated following IV infusion and using changes in PaCO2 as a marker for ventilatory stimulation. The GAL‐160 plasma concentration associated with a statistically significant reduction in PaCO2 (10% decrease relative to baseline) was 380 ng/ml. Collectively, these data demonstrate that GAL‐160 is a potent, orally bioavailable ventilatory stimulant with negligible effects on cardiovascular function.

Clinical outcome of the off-pump coronary artery bypass surgery- a comparison between combined high thoracic epidural anaesthesia with GA and GA alone

Background: The common challenges for the cardiac anaesthesiologist during off pump coronary artery surgery (OPCAB) include haemodynamic stability during the different stressful surgical events and multiple cardiac manipulations, providing adequate myocardial protection, and obtaining effective postoperative analgesia leading to early discharge from the intensive care unit. Objective: This study has been undertaken with a view to find out whether a combined high thoracic epidural anaesthesia (HTEA) with general anaesthesia (GA) is safe and more efficient in providing overall cardiovascular stability as well as improving the parameters leading to a better outcome in terms of a shorter and more predictable road maps to recovery. Methods: Sixty patients aged within 40-70 years, without having any coagulopathy disorder, any emergency surgery or left main disease scheduled for CABG on beating heart were enrolled in prospective, randomized observational comparative study. Patients were divided in two groups. In group A patients received GA alone and in group B patients received high thoracic epidural anaesthesia with GA. The parameters including heart rate, SPO2, CVP, arterial blood pressure, ECG, and ABG analysis were recorded before induction, during induction, intubation and during different events of the surgery. Post operative pain score, sedation score, ventilator hour, duration in the ICU stay, rescue analgesic need and post operative complications was assessed and recorded. Results: significant per-operative mean heart rate changes were observed all the events except at wound closure and during anastomosis with D1/D2 and the mean difference of mean arterial pressure at intubations, skin incision, sternotomy, pericardiotomy, during anastomosis of distal end of the graft with RCA, PDA, LCX and D1/D2 were observed statistically significant (p&lt;0.05). No incidence of different arrhythmia occurred in group B, premature ventricular complex (PVC) was statistically significant (p&lt;0.05) between two groups. No significant change was found in per-operative pH of arterial blood, PaCO2 and PaO2 changes at different times. Post operative pain score (VAS 0-100) in different time interval was found significant (p&lt;0.05) change between two groups in all follow-up times. Status of rescue analgesics were observed statistically significant (p&lt;0.05). The mean ventilator hours were 7.4±1.09 hours in group A and 5.3±0.81 hours in group B. The mean ICU stay was 72.9±9.2 hours in group A and 57.1±12.0 hours in group B. No post-operative complication was observed in both groups. The data were compiled and analyzed by using statistical software SPSS (ver. 12.0) and significance test performed by unpaired t test and Chi square test. P value &lt;0.05 was considered as statistically significant. Conclusion: Both anaesthetic techniques are equally safe but better clinical outcome of the OPCAB surgery with the high thoracic epidural anaesthesia with GA. DOI: http://dx.doi.org/10.3329/jbsa.v22i2.18142 Journal of BSA, 2009; 22(2): 54-60

Role of Toll-like receptor 4 in mechanical ventilation-induced increase in pulmonary capillary permeability in diabetic mice

Objective To evaluate the role of Toll-like receptor 4 (TLR4) in mechanical ventilationinduced increase in pulmonary capillary permeability in diabetic mice.Methods Two types of mice,aged 8-10 weeks,weighing 20-25 g,were used in this study:free wild type mice (C3H/HeN) and TLR4 gene mutation type (C3H/HeJ).Diabetes was induced by intraperitoneal streptozotocin 150 mg/kg (in citric acid buffer solution 0.1 mol/L) and confirmed by blood glucose level ＞ 16 mmol/L.Each type of diabetic mice was randomly divided into 2 groups (n =14 each):group diabetes + sham operation (group DS) and group diabetes + mechanical ventilation (group DM).The animals were anesthetized with intraperitoneal ketamine,midazolam and atropine.Tracheal intubation was performed and the animals kept spontaneous breathing in group DS.The animals were mechanically ventilated (FiO2 50％,RR 70 bpm,VT 15 ml/kg,PEEP 2 cmH2O) for 4 h in group DM.Arterial blood samples were obtained at 4 h of ventilation for blood gas analysis,PaO2 and PaCO2 were recorded,and NO concentration in the serum was measured.Then the animals were sacrificed and the lungs were removed for determination of W/D lung weight ratio (W/D ratio),content of evans blue (EB),and expression of caveolin-1,endothelial nitric oxide synthase (eNOS) and phosphor-eNOS (p-eNOS) (by Western blot).The ratio of p-eNOS/eNOS was calculated.Results Compared with group DS,PaO2,PaCO2 and p-eNOS/eNOS ratio were significantly decreased,and W/D ratio,EB content and caveolin-1 expression were increased in group DM (P ＜ 0.05).Compared with C3H/HeN mice,W/D ratio,caveolin-1 expression and EB content were significantly decreased,peNOS/eNOS ratio and serum NO concentrations were increased (P ＜ 0.05),and no significant changes in PaO2 and PaCO2 were found in C3H/HeJ mice in group DM (P ＞ 0.05).Conclusion TLR4 increases the pulmonary capillary permeability after mechanical ventilation in diabetic mice through effectively combining with caveolin-1 and reducing NO bioavailability. Key words: Toll-like receptor 4 ; Respiratory distress syndrome, adult; Diabetes mellitus; Capillary permeability

A conceptual model for CO2-induced redistribution of cerebral blood flow with experimental confirmation using BOLD MRI

Cerebrovascular reactivity (CVR) is the change in cerebral blood flow (CBF) in response to a change in a vasoactive stimulus. Paradoxical reductions in CBF in response to vasodilatory stimulation (‘steal’) are associated with vascular pathology. However, a pathophysiological interpretation of ‘steal’ requires a comprehensive conceptual model linking pathology and changes in blood flow. Herein, we extend a simple model explaining steal published in the late 1960s by incorporating concepts of CBF regulation from more recent studies to generate a comprehensive dynamic model. The main elements of the model are: (a) the relationship between changes in CBF and the arterial partial pressure of carbon dioxide (PaCO2) in healthy vascular regions is sigmoidal; (b) vascular regions vasodilate to compensate for decreased perfusion pressure, leading to (c) an encroachment on vasodilatory reserve and, reduced CVR; (d) a vasodilatory stimulus may increase CBF capacity above the flow capacity of major cerebral blood vessels; and (e) this limitation induces competitive intra-cerebral redistribution of flow from territories with low vasodilatory reserve to those with high reserve. We used CVR measurements generated by applying precise, computer-controlled changes in PaCO2 as the vasoactive stimulus, and measured blood oxygen level dependent (BOLD) MRI signals as high resolution surrogates of CBF to test predictions derived from this model. Subjects were 16 healthy adults and 16 patients with known cerebral steno-occlusive diseases. We observed regional sigmoidal PaCO2–BOLD response curves with a range of slopes; graded changes in PaCO2 resulted in redistributions of BOLD signal consistent with the known underlying vascular pathology and predictions of the model. We conclude that this model can be applied to provide a hemodynamic interpretation to BOLD signal changes in response to hypercapnia, and thereby aid in relating CVR maps to pathophysiological conditions.

Physiological comparison of breathing patterns with neurally adjusted ventilatory assist (NAVA) and pressure-support ventilation to improve NAVA settings

Neurally adjusted ventilator assist (NAVA) assists spontaneous breathing in proportion to diaphragmatic electrical activity (EAdi). Here, we evaluate the effects of various levels of NAVA and PSV on the breathing pattern and, thereby, on PaCO2 homeostasis in 10 healthy volunteers. For each ventilation mode, four levels of support (delivered pressure 0 i.e. baseline, 5, 8, and 10cmH2O) were tested in random order. EAdi, flow, and airway pressure were recorded. Optoelectronic plethysmography was used to study lung volume distribution. During both PSV and NAVA, EAdi decreased with the level of assistance (P<0.01). Tidal volume (VT) increased and PtCO2 decreased with increased levels of PSV (P=0.044 and P=0.0004; respectively) while no change was observed with NAVA. Subject–ventilator synchronization was better with NAVA than with PSV. NAVA and PSV similarly decreased the abdominal contribution to VT. No airflow profile similarities were observed between baseline and mechanical ventilation. Diaphragmatic activity can decrease during NAVA without any change in VT and PaCO2. This suggests that NAVA adjustment cannot be based solely on VT and PCO2 criteria.Registered by Frédéric Lofaso and Nicolas Terzi on ClinicalTrials.gov, #NCT01614873.

Effects of manually-assisted cough combined with postural drainage, saline instillation and airway suctioning in critically-ill patients during high-frequency oscillatory ventilation: a prospective observational single centre trial

Background: Chest physiotherapy may aid sputum clearance during conventional ventilation. However, the role of chest physiotherapy during high-frequency oscillatory ventilation (HFOV) is unclear. This study aimed to determine the effects manually-assisted cough (MAC), postural drainage, saline instillation and airway suction during HFOV. Methods: This was an observational study of a chest physiotherapy intervention in adult critically ill patients during HFOV. Measures included gas exchange, HFOV and haemodynamic variables 1 h before, immediately before, and 15 min, 1 h, 6 h and 12 h after intervention. Wet weight of airway secretions was also measured. Linear mixed modelling compared pre-intervention gas exchange, HFOV and haemodynamic variables with the four specified time-points after intervention. Results: Seventeen adults (ten females) with moderate to severe respiratory failure were studied (age, 49 years SD 14; Acute Physiology and Chronic Health Evaluation II score (APACHE II score) 21 SD 6; PaO2/FiO2 of 139 mmHg SD 51). There was a statistically, although not clinically significant reduction in PaO2/FiO2 for up to 1 h after intervention, but no significant changes in oxygenation index, PaCO2, pH, or haemodynamic parameters up to 12 h after intervention. A reduction in delta pressure (ΔPaw) at 15 min (p < 0.05) and 1 h (p < 0.05) post intervention was not correlated with sputum wet weight. Conclusions: MAC, postural drainage, saline instillation and airway suctioning during HFOV in critically ill patients was well tolerated with no clinically significant effect on arterial blood gases or haemodynamics. ΔPaw decreased for up to 1 h after intervention, but was not explained by the weight of sputum removed.

Cerebral hemodynamic and oxygenation changes induced by inner and heard speech: a study combining functional near-infrared spectroscopy and capnography

The aim of this study was to investigate the effects of inner and heard speech on cerebral hemodynamics and oxygenation in the anterior prefrontal cortex (PFC) using functional near-infrared spectroscopy and to test whether potential effects were caused by alterations in the arterial carbon dioxide pressure (PaCO2). Twenty-nine healthy adult volunteers performed six different tasks of inner and heard speech according to a randomized crossover design. During the tasks, we generally found a decrease in PaCO2 (only for inner speech), tissue oxygen saturation (StO2), oxyhemoglobin ([O2Hb]), total hemoglobin ([tHb]) concentration and an increase in deoxyhemoglobin concentration ([HHb]). Furthermore, we found significant relations between changes in [O2Hb], [HHb], [tHb], or StO2 and the participants' age, the baseline PETCO2, or certain speech tasks. We conclude that changes in breathing during the tasks led to lower PaCO2 (hypocapnia) for inner speech. During heard speech, no significant changes in PaCO2 occurred, but the decreases in StO2, [O2Hb], and [tHb] suggest that changes in PaCO2 were also involved here. Different verse types (hexameter and alliteration) led to different changes in [tHb], implying different brain activations. In conclusion, StO2, [O2Hb], [HHb], and [tHb] are affected by interplay of both PaCO2 reactivity and functional brain activity.

Respiratory CO2 response depends on plasma bicarbonate concentration in mechanically ventilated patients

ObjectiveThere is controversy about the effects of high plasma bicarbonate concentration ([HCO3−]) and the CO2 response test. We analyzed the relationship between [HCO3−] and the variation in hydrogen ion concentration (pH) for a given change in PaCO2, and its effects upon CO2 response. DesignA retrospective study was carried out. SettingTwo intensive care units. PatientsSubjects with and without chronic obstructive pulmonary disease (COPD), at the beginning of weaning from mechanical ventilation. InterventionsThe CO2 response was evaluated by the re-inhalation of expired air method, measuring the hypercapnic ventilatory response (ΔVE/ΔPaCO2) and hypercapnic drive response (ΔP01/ΔPaCO2), where VE is minute volume and P0.1 is airway occlusion pressure 0.1s after the initiation of inspiration. Main outcome measures[HCO3−] and CO2 response. ResultsA total of 120 patients in the non-COPD group and 48 in the COPD group were studied. COPD patients had higher mean [HCO3−] than non-COPD patients (33.2±5.4 vs. 25.7±3.7mmol/l, p<0.001). In both non-COPD and COPD patients we observed a significant inverse linear relationship between [HCO3−] and pH change per mmHg of PaCO2 (p<0.001), ΔVE/ΔPaCO2 (p<0.001) and ΔP0.1/ΔPaCO2 (p<0.001). ConclusionsThere is an inverse linear relationship between [HCO3−] and the variation of pH for a given change in PaCO2 and the CO2 response.

Positive end-expiratory pressure attenuates positional effect after thoracotomy.

CONTEXT:Thoracotomy is a common procedure. However, thoracotomy leads to lung atelectasis and deteriorates pulmonary gas exchange in operated side. Therefore, different positions with operated side lowermost or uppermost may lead to different gas exchange after thoracotomy. Besides, PEEP (positive end-expiratory pressure) influence lung atelectasis and should influence gas exchange.AIMS:The purpose of this study was to determine the physiological changes in different positions after thoracotomy. In addition, we also studied the influence of PEEP to positional effects after thoracotomy.MATERIALS AND METHODS:There were eight pigs in each group. Group I received left thoracotomy with zero end-expiratory pressure (ZEEP), and group II with PEEP; group III received right thoracotomy with ZEEP and group IV with PEEP. We changed positions to supine, LLD (left lateral decubitus) and RLD (right lateral decubitus) in random order after thoracotomy.RESULTS:PaO2 was decreased after thoracotomy and higher in RLD after left thoracotomy and in LLD after right thoracotomy. PaO2 in groups II and IV was higher than in groups I and III if with the same position. In group I and III, PaCO2 was increased after thoracotomy and was higher in LLD after left thoracotomy and in RLD after right thoracotomy. In groups II and IV, there were no PaCO2 changes in different positions after thoracotomy. Lung compliance (Crs) was decreased after thoracotomy in groups I and III and highest in RLD after left thoracotomy and in LLD after right thoracotomy. In groups II and IV, there were no changes in Crs regardless of the different positions.CONCLUSION:There were significant changes with regards to pulmonary gas exchange, hemodynamics and Crs after thoracotomy. The best position was non-operated lung lowermost Applying PEEP attenuates the positional effects.

S84 The effect of patient ventilator asynchrony (PVA) on health related quality of life during initiation of home mechanical ventilation (HMV)

IntroductionPoor patient-ventilator interaction has been shown to adversely affect respiratory muscle unloading, sleep quality, gas exchange and patient comfort whilst on ventilation. We hypothesised that nocturnal PVA during the first...

Nocturnal noninvasive positive pressure ventilation in stable COPD: A systematic review and individual patient data meta-analysis

The effects of nocturnal noninvasive positive pressure ventilation (NIPPV) in patients with stable chronic obstructive pulmonary disease (COPD) remain controversial. The Cochrane Airways group Register of Trials, MEDLINE, EMBASE and CINAHL were searched up to August 2012. Individual patient data from randomised controlled trials on NIPPV outcomes were selected for two separate meta-analyses: the first with follow-up of 3 months and the second with 12 months of follow-up. Additionally, subgroup analyses within the NIPPV group comparing IPAP levels, compliance and levels of hypercapnia on change in PaCO2 after 3 months were performed. Seven trials (245 patients) were included. All studies were considered of moderate to high quality. No significant difference was found between NIPPV and control groups after 3 or 12 months of follow-up when looking at PaCO2 and PaO2, 6-minute walking distance, health-related quality-of-life, forced expiratory volume in 1s, forced vital capacity, maximal inspiratory pressure and sleep efficiency. Significant differences in change in PaCO2 after 3 months were found for patients ventilated with IPAP levels of at least 18cm H2O, for patients who used NIPPV for at least 5hper night as well as for patients with baseline PaCO2 of at least 55mmHg when compared to patients with lower IPAP levels, poorer compliance or lower levels of hypercapnia. At present, there is insufficient evidence to support the application of routine NIPPV in patients with stable COPD. However, higher IPAP levels, better compliance and higher baseline PaCO2 seem to improve PaCO2.