End-tidal Carbon Dioxide Tension Research Articles

Effect of mild hypocapnia on hemodynamic and bispectral index responses to tracheal intubation during propofol anesthesia in children

The purpose of this study was to investigate the effect of mild hypocapnia on hypertension and arousal response after tracheal intubation in children during propofol anesthesia. Forty-four children, American Society of Anesthesiologists physical status I-II patients, aged 3-9 years were randomly allocated to either the normocapnia group [end-tidal carbon dioxide tension (ETCO2=35 mmHg, n=22)] or the hypocapnia group (ETCO2=25 mmHg, n=22). Anesthesia was induced with propofol 2.5 mg/kg. Five minutes after the administration of rocuronium 0.6 mg/kg, laryngoscopy was attempted. The mean arterial pressure (MAP), heart rate (HR), SpO2 and bispectral index (BIS) were measured during induction and intubation periods. The maximal change in the BIS with tracheal intubation (ΔBIS) was defined as the difference between the baseline value and the maximal value within the first 5 min after intubation. Before tracheal intubation, the change in BIS over time was not different between the groups. After tracheal intubation, the changes in the MAP, HR and BIS over time were not significantly different between the groups. The mean value±SD of ΔBIS was 5.7±5.2 and 7.4±5.5 in the normocapnia and hypocapnia groups, respectively, without any intergroup difference. This study showed that mild hypocapnia did not attenuate hemodynamic and BIS responses to tracheal intubation in children during propofol anesthesia. Our results suggested that hyperventilation has no beneficial effect on hemodynamic and arousal responses to tracheal intubation in children.

Arterial and end-tidal carbon dioxide difference in pediatric intensive care.

Background and Aim:Arterial carbon dioxide tension (PaCO2) is considered the gold standard for scrupulous monitoring in pediatric intensive care unit (PICU), but it is invasive, laborious, expensive, and intermittent. The study aims to explore when we can use end-tidal carbon dioxide tension (PETCO2) as a reliable, continuous, and noninvasive monitor of arterial CO2Materials and Methods:Concurrent PETCO2, fraction of inspired oxygen, PaCO2, and arterial oxygen tension values of clinically stable children on mechanical ventilation were recorded. Children with extra-pulmonary ventriculoatrial shunts were excluded. The PETCO2 and PaCO2 difference and its variability and reproducibility were studied.Results:A total of 624 concurrent readings were obtained from 105 children (mean age [SD] 5.53 [5.43] years) requiring invasive bi-level positive airway pressure ventilation in the PICU. All had continuous PETCO2 monitoring and an arterial line for blood gas measurement. The mean (SD) number of concurrent readings obtained from each child, 4-6 h apart was 6.0 (4.05). The PETCO2 values were higher than PaCO2 in 142 observations (22.7%). The PaCO2–PETCO2 difference was individual admission specific (ANOVA, P < 0.001). The PaCO2–PETCO2 difference correlated positively with the alveolar-arterial oxygen tension [P(A-a)O2] difference (ρ = 0.381 P < 0.0001). There was a fixed bias between the PETCO2 and PaCO2 measuring methods, difference +0.66 KPa (95% confidence interval: +0.57 to +0.76).Conclusions:The PaCO2–PETCO2 difference was individual specific. It was not affected by the primary disorder leading to the ventilation.

The effect of desflurane versus propofol on regional cerebral oxygenation in the sitting position for shoulder arthroscopy

The sitting position may cause significant hemodynamic instability and cerebral hypoperfusion. We investigated the effects of desflurane and propofol on regional cerebral oxygenation (rSO2) in the sitting position during arthroscopic shoulder surgery. Forty patients undergoing arthroscopic shoulder surgery in the sitting position were randomly allocated to the desflurane group (n = 20) or the propofol group (n = 20). Anesthetic agents were maintained and adjusted with the effect-site concentration of propofol (2-3.5 μg/ml) or desflurane (4-7 vol%) to obtain a bispectral index (BIS) of 40-50. The hemodynamic variables, end-tidal carbon dioxide tension (ETCO2) and rSO2 were measured and evaluated. There were no differences in BIS, hemodynamic variables and ETCO2 between the groups. The rSO2 values in the desflurane group were higher compared to the propofol group at 3, 5, 7 and 9 min after the sitting position (P = 0.031, 0.047, 0.025 and 0.034, respectively). However, it decreased significantly from the baseline values at 3, 5, 7 and 9 min after the sitting position in both groups (P < 0.001). The change in rSO2 across time was not significantly different between the groups (P = 0.183). The incidence of rSO2 <75% of the baseline values after the sitting position was similar between the groups (0 and 10% in the desflurane and propofol group, respectively, P = 0.487). When anesthetized patients were raised to the sitting position, desflurane preserved cerebral oxygenation better than propofol at equipotent concentrations in terms of BIS. However, both anesthetics were associated with significant decrease in the rSO2 values during the sitting position.

Hypopnea-dominant sleep-disordered breathing in extreme obesity

Introduction There appears to be a difference in the pathophysiological development of dynamic upper airway obstruction manifested as hypopneas in contrast to the static obstruction of apneas. We designed a study to test the hypothesis that extremely obese patients manifest sleep-disordered breathing predominantly as hypopneas with very few apneas. Materials and methods We performed a retrospective review of the data of 90 adults with obstructive sleep apnea–hypopnea syndrome (OSAHS), and assigned them to one of two groups. Group B had a body mass index (BMI) ⩾ 45 kg/m2, while Group A had a BMI 35 kg/m2, matched for age and gender with Group B. We excluded all those with age 18 years, pregnancy, BMI ⩾ 35 45 kg/m2 and those with ⩾ 5 central apneas/h. The primary outcome measure was the hypopnea/apnea ratio (HAR). The secondary measures were obstructive apnea–hypopnea index (AHI), obstructive and central apnea indices, hypopnea index, oxygen saturation (SpO2) nadir, end-tidal carbon dioxide tension (PetCO2), and presence or absence of obesity-hypoventilation syndrome (OHS). Data were analyzed with t-test for independent samples, and results expressed as group mean ± standard deviation, with p 0.05 considered significant. Results There were 45 subjects in each group. The mean age was 50.6 ± 11.5 years in Group A and 47.4 ± 12.7 years in Group B. The mean BMI was 28.9 ± 4 kg/m2 in Group A and 54.5 ± 8 kg/m2 in Group B. There were 15 patients with OHS, 4 in Group A and 11 in Group B. The HAR was significantly higher in the extremely obese Group B (38.8 ± 50.7) compared to Group A (10.6 ± 16.5), p = 0.0008, as was the hypopnea index (28.7 ± 28.6 in Group B vs 12.6 ± 8.4 in Group A, p = 0.0005) and AHI (35.5 ± 33.8 vs 22 ± 23, p = 0.03), but not the apnea index (11.2 ± 23.5 in Group A and 6.7 ± 13.6 in Group B, p = 0.25). The SpO2 nadir was lower in Group B (79.1 ± 7.1% vs 83.1 ± 6.7%, p = 0.007). There were no significant differences in sleep capnometry or sleep architecture. The HAR was higher in Group B regardless of gender, race or presence of OHS. There were no significant differences in HAR between OHS and non-OHS subjects, even when matched for BMI. The difference in HAR between Groups A and B was more robust in men than in women. Conclusion Sleep-disordered breathing in extremely obese (BMI ⩾ 45 kg/m2) subjects is manifested predominantly by hypopneas rather than apneas. This suggests a different pathophysiology, with implications for potential directed treatment modalities.

Elective use of an uncuffed small-bore cricothyrotomy tube with balloon occlusion of the subglottic airway

To conduct a qualitative observational study on positive pressure ventilation through a percutaneous uncuffed small-bore cricothyrotomy tube with balloon occlusion of the subglottic airway to minimize supraglottic leak. Ten consecutive procedures were performed in the nine men enrolled in this study. The demographics of the participants were: aged 50-73 yr, weight 48-87 kg, American Society of Anesthesiologists class I-II, and scheduled for endoscopic submucosal dissection via flexible endoscopy for en bloc resection of superficial meso- and hypopharyngeal cancer. The airway was initially secured with a supraglottic airway (SGA) under sevoflurane-based anesthesia, and a cricothyrotomy was then performed using a Portex(®) Minitrach II uncuffed cricothyrotomy tube (4-mm internal diameter). Following SGA removal, a Coopdech(®) bronchial blocker was orally or nasally inserted, and the balloon was inflated to occlude the trachea immediately beneath the glottis. The ventilator setting was initially based on observation of chest motion and end-tidal carbon dioxide tension and then readjusted according to arterial blood gas levels. All procedures were completed within a median time of 149 min. Effective ventilation was achieved in all patients despite mild hypercapnia (PaCO2 of 58 mmHg at maximum) in some patients. SpO2 levels were maintained at ≥ 98%. This technique provides effective intraoperative ventilation and easy endoscopic access, and it countermeasures against the likely complication of postoperative laryngeal edema. Moreover, there is no need for conventional tracheostomy or prolonged intubation. This approach establishes a curative and less invasive pharyngeal cancer therapy. Certain adverse outcomes can be avoided, including impaired speech and swallowing, possible delayed closure of the stoma, or a compromised cosmetic outcome.

Determinants of dynamic hyperinflation during metronome-paced tachypnea in COPD and normal subjects

In COPD, dynamic hyperinflation (DH) occurs during exercise and during metronome-paced tachypnea (MPT). We investigated the relationship of DH with breathing pattern and ventilation (V˙E) in COPD and normal subjects (NS).In 35 subjects with moderate COPD and 17 younger healthy volunteers we measured inspiratory capacity (IC), breathing frequency (fR), expiratory time (TE), ventilation (V˙E) and end-tidal carbon dioxide tension (PETCO2) at baseline and after 30s of MPT at 40breaths/min with metronome-defined I:E ratios of 1:1 and 1:2. A reduction in IC (ΔIC) was taken to indicate DH. In COPD subjects, DH correlated with TE but not with V˙E or PETCO2, and was best predicted by total lung capacity. NS also showed DH (although less than in COPD), which correlated with PETCO2 but not with fR, TE or V˙E.We conclude that MPT evokes DH in both NS and patients with COPD. TE is the most important determinant of DH during MPT in patients with COPD.

The use of a double‐lumen central venous catheter for airway management in pediatric patients undergoing laryngeal papillomatosis surgery

To evaluate the efficacy and safety of a spontaneous ventilation anesthesia technique with insufflation of oxygen and volatile agent through a double-lumen central venous catheter (DLCVC) in pediatric patients undergoing suspension laryngoscopic surgery for laryngeal papillomatosis. Thirty-six pediatric patients with laryngeal papillomatosis undergoing suspension laryngoscopic surgery were anesthetized with oxygen and volatile anesthetic insufflation while spontaneously breathing. Anesthesia was induced by inhalation of 8% sevoflurane in oxygen by mask. Atropine, dexamethasone, lidocaine, and midazolam were administered intravenously. The tip of a 7Fr DLCVC was inserted below the glottis after placement of the laryngoscope and establishing suspension. Anesthesia was maintained with insufflation of 4-6% sevoflurane and oxygen with a total fresh gas flow of 6 l·min(-1) through the 14G (larger lumen) of the DLCVC. Endtidal carbon dioxide tension (PetCO2) was monitored using the other lumen of the DLCVC, which was connected to the CO2 sampling line. Duration of the procedure as well as total anesthesia time was recorded. Electrocardiography (ECG), heart rate (HR), mean arterial pressure (MAP), oxygen saturation (SpO2), and PetCO2 were also monitored. Arterial blood was sampled for blood gas analysis including pH, PaO2 , PaCO2 , and actual base excess (ABE). Complications, including intraoperative patient movement, hypoxemia (SpO2 < 95% during oxygen insufflation), nausea, vomiting, bronchospasm, and arrhythmias, were recorded. There was a significant increase in PetCO2 and PaCO2 (P values <0.05) as well as a decrease in ABE, pH, and PaO2 (P values <0.05) in samples collected before and after surgery. MAP, HR, and SpO2 after surgery were not significantly different from after induction values (P values >0.05). During surgery, SpO2 < 95% in three cases and body movements in three cases were observed. No patient had any other of the complications previously described. Furthermore, no postsurgical endotracheal intubation was needed in any patient. After establishing an adequate depth of anesthesia, a spontaneous ventilation anesthesia technique with insufflation of oxygen and volatile agent through a DLCVC is feasible in pediatric patients undergoing suspension laryngoscopic surgery for laryngeal papillomatosis.

Positive end-expiratory pressure during laparoscopy: cardiac and respiratory effects

Study ObjectiveTo determine the effect of positive end-expiratory pressure (PEEP) on the respiratory system and on cardiac function. DesignProspective randomized study. SettingOperating room. Patients60 ASA physical status 1 women scheduled for pelvic laparoscopic surgery. InterventionsPatients were ventilated normally during surgery; PEEP was modified depending on patient group allocation. Group A was the control group and did not receive PEEP. Group B received PEEP 5 cmH2O and Group C received PEEP 10 cmH2O. MeasurementsRespiratory parameters measured were partial pressure of arterial oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), and end-tidal carbon dioxide tension (ETCO2). Cardiac parameters measured were left ventricular end-diastolic volume index (LVEDVI), ie, ratio of LVEDV/body surface area (BSA; [LVEDVI = end-diastolic volume [EDV]/BSA); left ventricular (LV) systolic function, tricuspid annular plane systolic excursion (TAPSE), right ventricular (RV) fractional area change (FAC), RV dimensions in the apical 4-chamber view, tracing basal and mid-cavity minor dimensions and longitudinal dimension, cardiac index, systolic pulmonary artery pressure (PASP), and systolic RV pressure (RVSP). Respiratory and cardiac measurements were recorded at T0 (baseline); T1 (after anesthesia induction, before pneumoperitoneum induction); at 10 (T2), 20 (T3), and 30 (T4) minutes after CO2 insufflation; and at the end of surgery (T5). Main ResultsVentilation with PEEP at 10 cm H2O led to significant improvement in both respiratory and cardiac parameters. A reduction in pulmonary vascular resistance and enhanced washout of expiratory CO2 occurred. Ten and, to a lesser extent, 5 cm H2O of PEEP decreased LV stroke work. ConclusionsVentilation with PEEP (up to 10 cm H2O) recruits the hypoventilated areas of the lungs and reduces cardiac afterload.

Preservation of the metabolic rate of oxygen in preterm infants during indomethacin therapy for closure of the ductus arteriosus

The aim of this study was to assess and quantify the effects of indomethacin on cerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) in preterm infants undergoing treatment for a patent ductus arteriosus (PDA). CBF and CMRO2 were measured before and after the first dose of a 3-d course of indomethacin to close hemodynamically significant PDA in preterm neonates. Indocyanine-green (ICG) concentration curves were acquired before and after indomethacin injection to quantify CBF and CMRO2. Eight preterm neonates (gestational age, 27.6 ± 0.5 wk; birth weight, 992 ± 109 g; 6 males:2 females) were treated at a median age of 4.5 d (range, 4-21 d). Indomethacin resulted in an average CBF decrease of 18% (pre- and post-CBF = 12.9 ± 1.3 and 10.6 ± 0.8 ml/100 g/min, respectively) and an OEF increase of 11% (pre- and post-OEF = 0.38 ± 0.02 and 0.42 ± 0.02, respectively) but no significant change in CMRO2 (pre- and post-CMRO2 = 0.83 ± 0.07 and 0.76 ± 0.07 ml O2/100 g/min, respectively). Corresponding mean blood pressure (BP), arterial oxygen saturation (SaO2), heart rate, and end-tidal carbon dioxide tension levels remained unchanged. Indomethacin resulted in significant reduction in CBF but did not alter CMRO2 because of a compensatory increase in OEF.

The effect of a peptide-containing synthetic lung surfactant on gas exchange and lung mechanics in a rabbit model of surfactant depletion

BackgroundCurrently, a new generation of synthetic pulmonary surfactants is being developed that may eventually replace animal-derived surfactants used in the treatment of respiratory distress syndrome. Enlightened by this, we prepared a synthetic peptide-containing surfactant (Synsurf) consisting of phospholipids and poly-l-lysine electrostatically bonded to poly-l-glutamic acid. Our objective in this study was to investigate if bronchoalveolar lavage (BAL)-induced acute lung injury and surfactant deficiency with accompanying hypoxemia and increased alveolar and physiological dead space is restored to its prelavage condition by surfactant replacement with Synsurf, a generic prepared Exosurf, and a generic Exosurf containing Ca2+.MethodsTwelve adult New Zealand white rabbits receiving conventional mechanical ventilation underwent repeated BAL to create acute lung injury and surfactant-deficient lung disease. Synthetic surfactants were then administered and their effects assessed at specified time points over 5 hours. The variables assessed before and after lavage and surfactant treatment included alveolar and physiological dead space, dead space/tidal volume ratio, arterial end-tidal carbon dioxide tension (PCO2) difference (mainstream capnography), arterial blood gas analysis, calculated shunt, and oxygen ratios.ResultsBAL led to acute lung injury characterized by an increasing arterial PCO2 and a simultaneous increase of alveolar and physiological dead space/tidal volume ratio with no intergroup differences. Arterial end-tidal PCO2 and dead space/tidal volume ratio correlated in the Synsurf, generic Exosurf and generic Exosurf containing Ca2+ groups. A significant and sustained improvement in systemic oxygenation occurred from time point 180 minutes onward in animals treated with Synsurf compared to the other two groups (P < 0.001). A statistically significant decrease in pulmonary shunt (P < 0.001) was found for the Synsurf-treated group of animals, as well as radiographic improvement in three out of four animals in that group.ConclusionIn general, surfactant-replacement therapy in the animals did not fully restore the lung to its prelavage condition. However, our data show that the formulated surfactant Synsurf improves oxygenation by lowering pulmonary shunt.

Effects of a constant rate infusion of magnesium sulphate in healthy dogs anaesthetized with isoflurane and undergoing ovariohysterectomy

ObjectiveTo determine the effects of intravenous (IV) magnesium sulphate (MgSO4) as a bolus followed by a constant rate infusion (CRI) on anaesthetic requirements, neuroendocrine stress response to surgery, haemostasis and postoperative analgesia in healthy dogs undergoing ovariohysterectomy. Study designBlinded randomized clinical trial. AnimalsSixteen female dogs. MethodsAfter intramuscular premedication with acepromazine (0.05 mg kg−1) and morphine (0.3 mg kg−1), anaesthesia was induced with diazepam (0.2 mg kg−1) and propofol (2 mg kg−1) intravenously and maintained with isoflurane in oxygen in all dogs. Dogs were randomly assigned to two groups, M and C. Group M received MgSO4 (50 mg kg−1 over 15 minutes, followed by a 15 mg kg−1 hour−1 CRI). Group C received an equivalent bolus and CRI of lactated Ringer's solution. In addition, all dogs received lactated Ringer's solution (10 mL kg−1 over 15 minutes followed by 10 mL kg−1 hour−1). End-tidal isoflurane and carbon dioxide tensions, cardio-respiratory variables, arterial blood gases, electrolytes, ACTH and cortisol concentrations were measured at different time points. Thromboelastography (TEG) was performed pre- and post-anaesthesia. Postoperative pain was evaluated using the short form of the Glasgow Composite Pain Scale. Data were analysed with repeated measures anova and Mann–Whitney U tests (p< 0.05). ResultsNo statistically significant differences between groups were found in any of the measured variables. However, the alpha angle and maximal amplitude recorded by TEG in group M were significantly increased post-anaesthesia, but remained within the reference interval. One dog in Group M and two in Group C received rescue analgesia during recovery. Conclusions and clinical relevanceAs used in this study, MgSO4 failed to decrease isoflurane requirements, postoperative pain and stress hormone concentrations; however, it did not produce any cardio-respiratory or major haemostatic side effects. Administration of intravenous MgSO4 together with an opioid during ovariohysterectomy in dogs does not seem to provide any clinical advantage.

Vascular and right ventricular remodelling in chronic thromboembolic pulmonary hypertension

In chronic thromboembolic pulmonary hypertension (CTEPH) increased pulmonary vascular resistance is caused by fibrotic organisation of unresolved thromboemboli. CTEPH mainly differs from pulmonary arterial hypertension (PAH) by the proximal location of pulmonary artery obliteration, although distal arteriopathy can be observed as a consequence of non-occluded area over-perfusion. Accordingly, there is proportionally more wave reflection in CTEPH, impacting on pressure and flow wave morphology. However, the time constant, i.e. resistance × compliance, is not different in CTEPH and PAH, indicating only trivial effects of proximal wave reflection on hydraulic right ventricular load. More discriminative is the analysis of the pressure decay after pulmonary arterial occlusion, which is more rapid in the absence of significant distal arteriopathy. Structure and function of the right ventricle show a similar pattern to right ventricular hypertrophy, namely dilatation and wall thickening, as well as loss of function in CTEPH and PAH. This is probably related to similar loading conditions. Hyperventilation with hypocapnia is characteristic of both PAH and CTEPH. Ventilatory equivalents for carbon dioxide, as a function of arterial carbon dioxide tension, conform to the alveolar ventilation equation in both conditions, indicating a predominant role of increased chemosensitivity. However, a slight increase in the arterial to end-tidal carbon dioxide tension gradient in CTEPH shows a contribution of increased dead space ventilation.

Intravenous boluses of fentanyl, 1 µg kg−1, and remifentanil, 0.5 µg kg−1, give similar maximum ventilatory depression in awake volunteers

The relative respiratory effects of fentanyl and remifentanil, administered as i.v. bolus, have not previously been studied. We determined what remifentanil bolus dose gave the same maximum depression of ventilation as 1 µg kg(-1) of fentanyl. Twelve healthy volunteers rebreathed in a system designed to dampen variations in end-tidal carbon dioxide tension PE'CO2 so that measurements would be obtained at similar levels of CO(2) stimulation. The minute ventilation was measured before (V(preinj)) and after injection (V(nadir)) of fentanyl, 1 µg kg(-1), and remifentanil, 0.25, 0.5, and 1 µg kg(-1). The remifentanil doses were plotted against V(nadir)/V(preinj) in a log-probit diagram to determine what amount gave the same maximum ventilatory depression as the fentanyl dose. V(nadir) was [median (inter-quartile range)] 51 (38-64)% of V(preinj) after fentanyl, and 70 (61-77), 50 (46-56), and 29 (24-38)%, respectively, after remifentanil. The nadir occurred 5.0 (4.4-7.0) min after fentanyl, and 3.8 (2.7-4.6), 2.9 (2.7-3.2), and 3.0 (2.7-3.2) min after remifentanil injection. PE'CO2 at ventilation nadir was 6.26 (5.98-6.62) kPa after fentanyl, and 6.18 (6.12-6.50), 6.11 (5.91-6.45), and 6.11 (5.93-6.45) kPa after remifentanil 0.25, 0.5, and 1 µg kg(-1), respectively. A remifentanil dose of 0.47 (0.42-0.62) µg kg(-1) was equidepressant to 1 µg kg(-1) of fentanyl. Fifteen minutes after fentanyl injection, the median minute ventilation was 30-40% less than after injection of remifentanil, 0.25 and 0.5 µg kg(-1) (P<0.05). Fentanyl, 1 µg kg(-1), and remifentanil, 0.5 µg kg(-1), gave similar maximum ventilatory depression. The onset of and recovery from ventilatory depression were faster with remifentanil.

Exercise testing to predict outcome in idiopathicversusassociated pulmonary arterial hypertension

We tested the ability of exercise testing to predict not only survival, but also time to clinical worsening (TTCW) in idiopathic versus associated pulmonary arterial hypertension (PAH). 136 patients with PAH (85 idiopathic and 51 with associated conditions) underwent cardiopulmonary exercise testing and a 6-min walk test. Death or transplantation, and clinical worsening events were recorded. 32 patients died and four had lung transplantation. In a univariate analysis, PAH patients survival was associated with oxygen uptake (V'(O(2))) at peak exercise and at the anaerobic threshold, ventilatory equivalent for carbon dioxide (minute ventilation (V'(E))/carbon dioxide production (V'(CO(2))) at the anaerobic threshold ((at))), V'(E)/V'(CO(2)) slope and distance walked. TTCW was associated with peak V'(O(2)) and V'(O(2),at), V'(E)/V'(CO(2),at), end-tidal carbon dioxide tension measured at the anaerobic threshold, peak oxygen pulse, increase in oxygen pulse and distance walked. In a multivariable analysis, distance walked and V'(E)/V'(CO(2),at) predicted survival, and only peak V'(O(2)) predicted TTCW. The receiver operating characteristic curve-derived cut-off values were 305 m for the 6-min walk distance, 54 for V'(E)/V'(CO(2),at) and 11.6 mL·kg(-1)·min for peak V'(O(2)). In the subgroup with associated PAH, no variable independently predicted either survival or clinical worsening. We conclude that several exercise variables predict survival and clinical stability in idiopathic PAH. Exercise variables are less accurate predictors of outcome in associated PAH.

Exercise training reverses exertional oscillatory ventilation in heart failure patients

Exertional oscillatory ventilation (EOV) is an ominous prognostic sign in chronic heart failure (CHF), but little is known about the success of specific therapeutic interventions. Our aim was to study the impact of an exercise training on exercise capacity and cardiopulmonary adaptation in stable CHF patients with left ventricular systolic dysfunction and EOV. 96 stable CHF patients with EOV were included in a retrospective analysis (52 training versus 44 controls). EOV was defined as follows: 1) three or more oscillatory fluctuations in minute ventilation (V'(E)) during exercise; 2) regular oscillations; and 3) minimal average ventilation amplitude ≥5 L. EOV disappeared in 37 (71.2%) out of 52 patients after training, but only in one (2.3%) out of 44 without training (p<0.001). The decrease of EOV amplitude correlated with changes in end-tidal carbon dioxide tension (r= -0.60, p<0.001) at the respiratory compensation point and V'(E)/carbon dioxide production (V'(CO(2))) slope (r=0.50, p<0.001). Training significantly improved resting values of respiratory frequency (f(R)), V'(E), tidal volume (V(T)) and V'(E)/V'(CO(2)) ratio. During exercise, V'(E) and V(T) reached significantly higher values at the peak, while f(R) and V'(E)/V'(CO(2)) ratio were significantly lower at submaximal exercise. No change was noted in the control group. Exercise training leads to a significant decrease of EOV and improves ventilatory efficiency in patients with stable CHF.

Difference in the value of arterial and end-tidal carbon dioxide tension according to different surgical positions: Does it reliably reflect ventilation-perfusion mismatch?

BackgroundBody posture, as a gravitational factor, has a clear impact on pulmonary ventilation and perfusion. In lung units with mismatched ventilation and perfusion, gas exchange and/or elimination of carbon dioxide can be impaired. In this situation, differences in the value of arterial and end-tidal carbon dioxide tension [Δ(PaCO2 - PETCO2)] are expected to increase. This study was conducted to observe how Δ(PaCO2 - PETCO2) changed according to the 3 different surgical positions, and to determine whether Δ(PaCO2 - PETCO2) is a reliable predictor of ventilation/perfusion mismatch when a patient is in different postural positions.MethodsFifty-nine patients were divided into either the chronic obstructive pulmonary disease (COPD) group (n = 29) or the non-COPD group (n = 30). PaCO2 and PETCO2 were measured during surgery in the supine, prone, and lateral decubitus positions after a 10 minute stabilization period. The Δ(PaCO2 - PETCO2) were calculated and compared among positions.ResultsThe Δ(PaCO2 - PETCO2) decreased slightly in the prone position and increased significantly in the lateral decubitus position compared with the supine position in both groups. These patterns almost corresponded with the degree of ventilation/perfusion mismatch from the results of the radiological studies. The Δ(PaCO2 - PETCO2) in the COPD group was significantly greater than that in the non-COPD group at all surgical positions.ConclusionsLateral decubitus position is associated with marked increase in Δ(PaCO2 - PETCO2), especially in patients with COPD. The Δ(PaCO2 - PETCO2) is a simple and reliable indicator to predict ventilation/perfusion mismatch at different surgical positions in patients with or without COPD.

The Effect of Pressure-controlled Ventilation on Pulmonary Mechanics in the Prone Position During Posterior Lumbar Spine Surgery

When an anesthetized patient is turned to the prone position using the Wilson frame, dynamic compliance (Cdyn) decreases and peak airway pressure (Ppeak) increases. As pressure-controlled ventilation (PCV) decreases the Ppeak, this prospective, randomized study was designed to compare the effect of PCV and volume-controlled ventilation (VCV) on lung mechanics in the prone position using the Wilson frame during posterior lumbar spine surgery. Forty patients scheduled for posterior lumbar spine surgery were randomly allocated to receive mechanical ventilation using either the VCV (n=20) or PCV (n=20) mode. Respiratory variables (including Ppeak and Cdyn) and oxygenation parameters were recorded at the supine position (Tsupine) and 30 minutes after prone positioning (Tprone). During the study period, tidal volume, minute volume, end-tidal carbon dioxide tension, and positive end-expiratory pressure were comparable between the 2 groups. The Ppeak in the PCV group was lower than that in the VCV group throughout the study period (P=0.007 and 0.003 at Tsupine and Tprone, respectively) and was increased at Tprone compared with Tsupine in both groups. Cdyn was decreased from Tsupine to Tprone in both groups. However, the Cdyn in the PCV group was higher than that in the VCV group during the study period. The arterial oxygen tension was comparable between the 2 groups during the study period. PCV provides lower Ppeak compared with VCV when the ventilator is set to deliver the same tidal volume and variable respiratory rate to maintain a constant end-tidal carbon dioxide tension in patients undergoing posterior lumbar spine surgery in the prone position using the Wilson frame.

Comparative incidence of cardiovascular changes during venous air embolism as detected by transesophageal echocardiography alone or in combination with end tidal carbon dioxide tension monitoring

The objective of our study was to compare the incidences of cardiovascular disturbance during venous air embolism (VAE) episodes detected using transesophageal echocardiography (TEE) and end tidal carbon dioxide (ETCO 2) tension monitoring. We retrospectively analyzed the anesthesia records of patients who underwent posterior fossa surgery while in the sitting position and who were simultaneously monitored using both TEE and ETCO 2 tension monitoring. Data on the occurrence of VAE and the cardiovascular changes associated with it were recorded. Patients were divided into the ETCO 2-positive group (both TEE and ETCO 2 tension monitoring indicated VAE) and the ETCO 2-negative group (TEE alone indicated VAE, no significant drop in ETCO 2). No instances of cardiovascular disturbance were detected in the ETCO 2-negative group, whereas the incidences of tachycardia and hypotension were 20% and 30%, respectively, in the ETCO 2-positive group. None of the episodes of VAE detected by TEE (without a fall in ETCO 2) were clinically significant. We conclude that ETCO 2 monitoring is sensitive enough to detect hemodynamically significant VAE episodes.

Neurologic Recovery Following Prolonged Out-of-Hospital Cardiac Arrest With Resuscitation Guided by Continuous Capnography

A 54-year-old man with no known cardiac disease collapsed outdoors in a small rural community. The cardiac arrest was witnessed, and immediate cardiopulmonary resuscitation was begun by a bystander and a trained first responder who was nearby. The patient was moved into a building across the street for continued resuscitation. First responders arrived with an automated external defibrillator, and ventricular fibrillation was documented. First responders delivered 6 defibrillation shocks, 4 of which transiently restored an organized electrocardiographic rhythm but with no pulse at any time. Additional emergency medical services personnel from nearby communities and an advanced life support (ALS) flight crew arrived. The flight crew initiated ALS care. The trachea was intubated, ventilation controlled, and end-tidal carbon dioxide tension continuously monitored. Antiarrhythmic and inotropic drugs were administered intravenously. An additional 6 shocks were delivered using the ALS defibrillator. End-tidal carbon dioxide measurements confirmed good pulmonary blood flow with chest compressions, and resuscitation was continued until a stable cardiac rhythm was restored after 96 minutes of pulselessness. The patient was transported by helicopter to the hospital. He was in cardiogenic shock but maintained a spontaneous circulation. Coronary angiography confirmed a left anterior descending coronary artery thrombotic occlusion that was treated successfully. After hospital admission, the patient required circulatory and ventilatory support and hemodialysis for acute renal failure. He experienced a complete neurologic recovery to his pre-cardiac arrest state. To our knowledge, this is the longest duration of pulselessness in an out-of-hospital arrest with a good outcome. Good pulmonary blood flow was documented throughout by end-tidal carbon dioxide measurements.

Cannabinoid effects on ventilation and breathlessness: A pilot study of efficacy and safety

Based on the neurophysiology of dyspnoea and the distribution of cannabinoid receptors within the central nervous system, we hypothesize that the unpleasantness of breathlessness will be ameliorated in humans by cannabinoids, without respiratory depression. Five normal and four chronic obstructive pulmonary disease (COPD) subjects entered a double blind, randomized, placebo-controlled crossover study with two test days. Subjects received sublingual cannabis extract or placebo. A maximum of 10.8 mg tetrahydrocannabinol and 10 mg cannabidiol were given. Breathlessness was simulated using fixed carbon dioxide loads. Measurements taken were of breathlessness (visual analogue scale [VAS] and breathlessness descriptors), mood and activation, end-tidal carbon dioxide tension and ventilatory parameters. These were measured at baseline and 2 hours post placebo and drug administration. Normal and COPD subjects showed no differences in breathlessness VAS scores and respiratory measurements before and after placebo or drug. After drug administration, COPD subjects picked 'air hunger' breathlessness descriptors less frequently compared to placebo. We have shown that breathlessness descriptors may detect an amelioration of the unpleasantness of breathlessness by cannabinoids without a change in conventional breathlessness ratings (VAS). A stimulus more specific for air hunger may be needed to demonstrate directly a drug effect on breathlessness. However, this study shows that the inclusion of respiratory descriptors may contribute to the assessment of drug effects on breathlessness.