High FiO2 Research Articles

TRANSCUTANEOUS PRESSURE OF OXYGEN

A noninvasive tool to recognize early shock would improve outcome by providing prompt recognition of tissue ischemia and precise resuscitation endpoint. The skin is the first tissue bed to vasoconstrict in shock states. Studies have demonstrated that transcutaneous partial pressure of oxygen (PtCO2) increases with higher FiO2 in nonshock states as arterial pressure of oxygen (PaO2) increases, but in shock situations, PtCO2 mirrors changes in cardiac output and oxygen delivery with minimum response to increasing FiO2 and PaO2. This study examined the relationship of hemodynamic variables and the degree of PtCO2 response to FiO2 of 1.0 (identified as the "oxygen challenge test") to mortality and organ failure. This prospective observational study examined 38 patients requiring at least 24 h of cardiac output monitoring for shock resuscitation in the Surgical Intensive Care Unit. Patients were resuscitated to the standard protocol of blood pressure, urine output, oxygen delivery (DO2), and mixed venous O2 (SvO2). Seventy-nine percent of the patients (30/38) with a mean age of 59 +/- 21 years had septic shock or severe sepsis with a 26% mortality (10/38). Measurements included hemodynamic variables, PtCO2, and outcome (mortality and organ failure). In this study, the ability of PtCO2 value to increase by 21 mmHg on a FiO2 of 1.0, at 24 h of resuscitation, divided survivors from nonsurvivors, P <.001. The PtCO2 response to FiO2 may provide an additional noninvasive method of detecting early shock as well as a specific endpoint of resuscitation.

Effect of inspired oxygen fraction on alveolar derecruitment in acute respiratory distress syndrome

High fractions of inspired oxygen (FIO(2)) used in acute lung injury (ALI) may promote resorption atelectasis. The impact of derecruitment related to high FIO(2) in ALI is debated. We evaluated derecruitment with 100% vs. 60% FIO(2) at two levels of positive end-expiratory pressure (PEEP). Fourteen consecutive patients with ALI were studied. Recruited volume at two PEEP levels was computed from two pressure-volume curves, recorded from PEEP and from zero end-expiratory pressure, using the sinusoidal flow modulation method. PEEP-induced recruitment was measured during prolonged expiration as the difference between the two curves at a given pressure. PaO(2)/FIO(2) was also measured. PEEP was 5 +/- 1 or 14 +/- 3 cmH(2)O and FIO(2) was 60% or 100%, yielding four combinations. We looked for differences between the beginning and end of a 30-min period with each combination. With low PEEP and 100% FIO(2), recruited volume decreased significantly from 68 +/- 53 to 39 +/- 43 ml and PaO(2)/FIO(2) from 196 +/- 104 to 153 +/- 83 mmHg. With the three other combinations (low PEEP and 60% FIO(2) or high PEEP and 60% or 100% FIO(2)) none of the parameters decreased significantly. In mechanically ventilated patients with ALI the breathing of pure oxygen leads to derecruitment, which is prevented by high PEEP.

Relation between PaO2/FIO2 ratio and FIO2: a mathematical description

The acute respiratory distress syndrome (ARDS) is characterized by severe hypoxemia, a cornerstone element in its definition. Numerous indices have been used to describe this hypoxemia, such as the arterial to alveolar O2 difference, the intrapulmonary shunt fraction, the oxygen index and the PaO2/FIO2 ratio. Of these different indices the PaO2/FIO2 ratio has been adopted for routine use because of its simplicity. This ratio is included in most ARDS definitions, such as the Lung Injury Score [1] and in the American-European Consensus Conference Definition [2]. Ferguson et al. recently proposed a new definition including static respiratory system compliance and PaO2/FIO2 measurement with PEEP set above 10 cmH2O, but FIO2 was still not fixed [3]. Important for this discussion, the PaO2/FIO2 ratio is influenced not only by ventilator settings and PEEP but also by FIO2. First, changes in FIO2 influence the intrapulmonary shunt fraction, which equals the true shunt plus ventilation- perfusion mismatching. At FIO2 1.0, the effects of ventilation-perfusion mismatch are eliminated and true intrapulmonary shunt is measured. Thus, the estimated shunt fraction may decrease as FIO2 increases if V/Q mismatch is a major component in inducing hypoxemia (e.g., chronic obstructive lung disease and asthma). Second, at an FIO2 of 1.0 absorption atelectasis may occur, increasing true shunt [4]. Thus, at high FIO2 levels (> 0.6) true shunt may progressively increase but be reversible by recruitment maneuvers. Third, because of the complex mathematical relationship between the oxy-hemoglobin dissociation curve, the arterio-venous O2 difference, the PaCO2 level and the hemoglobin level, the relation between PaO2/FIO2 ratio and FIO2 is neither constant nor linear, even when shunt remains constant.

Risk factors, Sequential Organ Failure Assessment and Model for End‐stage Liver Disease scores for predicting short term mortality in cirrhotic patients admitted to intensive care unit

Prognostic scores in an intensive care unit (ICU) evaluate outcomes, but derive from cohorts containing few cirrhotic patients. To evaluate 6-week mortality in cirrhotic patients admitted to an ICU, and to compare general and liver-specific prognostic scores. A total of 312 consecutive cirrhotic patients (65% alcoholic; mean age 49.6 years). Multivariable logistic regression to evaluate admission factors associated with survival. Child-Pugh, Model for End-stage Liver Disease (MELD), Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores were compared by receiver operating characteristic curves. Major indication for admission was respiratory failure (35.6%). Median (range) Child-Pugh, APACHE II, MELD and SOFA scores were 11 (5-15), 18 (0-44), 24 (6-40) and 11 (0-21), respectively; 65% (n = 203) died. Survival improved over time (P = 0.005). Multivariate model factors: more organs failing (FOS) (<3 = 49.5%, > or =3 = 90%), higher FiO(2), lactate, urea and bilirubin; resulting in good discrimination [area under receiver operating characteristic curve (AUC) = 0.83], similar to SOFA and MELD (AUC = 0.83 and 0.81, respectively) and superior to APACHE II and Child-Pugh (AUC = 0.78 and 0.72, respectively). Cirrhotics admitted to ICU with > or =3 failing organ systems have 90% mortality. The Royal Free model discriminated well and contained key variables of organ function. SOFA and MELD were better predictors than APACHE II or Child-Pugh scores.

Efficiency of oxygen administration: Sequential gas delivery versus “flow into a cone” methods

Fio2 values of a new oxygen mask that exploits efficiencies afforded by sequential gas delivery (SGD) were compared to those of a nonrebreathing mask (NRM) and a Venturi oxygen mask. Prospective, single-blinded, randomized study. Laboratory study. Eight healthy male volunteers. Volunteers breathed through each of the masks at various minute ventilations (VE). Oxygen flows were 2, 4, and 8 L/min to the SGD mask but only 8 L/min to the other masks. Net FIO2 was calculated from end-tidal fractional concentrations of oxygen and CO2 with the alveolar gas equation. Only the SGD mask at an oxygen flow of 8 L/min consistently provided both FIO2>0.95 (at resting VE) and higher FIO2 than the other masks at all VE. The SGD mask delivered FIO2 comparable to other masks at only a fraction of the oxygen flow and was characterized by a consistent relation between FIO2 and oxygen flow for a given VE. We conclude that SGD can be exploited to provide FIO2>0.95 with oxygen flows as low as 8 L/min, as well as accurate and efficient dosing of oxygen even in the presence of hyperpnea.

Effects of Antenatal Glucocorticoids on Circulatory Adaptation at Birth in the Ovine Fetus

Objective: Adaptation to extra-uterine life requires dramatic increase in pulmonary blood flow. Mechanisms that induce pulmonary vasodilatation at birth are incompletely understood but include alveolar ventilation, increase in PaO₂, and production of vasoactive mediators. We hypothesized that antenatal glucocorticoids (GC) increase pulmonary vasodilatation to birth-related stimuli. Study Design: To test this hypothesis, we studied the pulmonary hemodynamic response at birth to mechanical ventilation with low (<10%) and then with high (100%) FiO₂ in chronically prepared late-gestation fetal lambs treated or not by antenatal maternal steroids. Results: Basal mean aortic and pulmonary artery pressure (PAP), left pulmonary blood flow, pulmonary vascular resistance (PVR), and blood gas were similar between control and dexamethasone-treated animals (GC group). During mechanical ventilation with low FiO₂, mean PVR decreased by 40% in the control group (from 0.44 ± 0.01 to 0.25 ± 0.01 mm Hg/ml/min) and by 60% in the GC group (from 0.44 ± 0.02 to 0.19 ± 0.02 mm Hg/ml/min) (p < 0.01). When subsequently ventilated with 100% O₂, there was no difference in PVR decrease between groups (0.15 ± 0.02 mm Hg/ml/min in the GC group vs. 0.14 ± 0.01 mm Hg/ml/min in the control group). Conclusion: Antenatal GC enhance pulmonary vasodilatation induced by alveolar ventilation at birth but do not alter the pulmonary vascular response to O₂. We speculate that antenatal steroids exposure improve adaptation at birth through acceleration of both parenchymal and vascular lung maturation.

A new BAL fluid instillation and aspiration technique: A multicenter randomized study

Bronchoalveolar lavage (BAL) is a widely used clinical and research tool even though certain steps in the procedure have not been standarized. One step that is subject to variation is the technique used to instill and recover BAL fluid. Our aim was to assess whether attaching a plastic tube between the syringe and the working channel of the flexible bronchoscope allowed recovery of more fluid in comparison with recovery using only a syringe, and whether tubing had a favorable impact on diagnostic yield and complications. A randomized multicenter study was performed in eleven public hospitals in Catalonia (Spain). Patients scheduled for BAL were randomly assigned to tubing (n=140) or no-tubing groups (n=155). Flexible bronchoscopy and a 150 mL BAL in three 50 mL aliquots with or without tubing attached to the syringe. In the group with tubing, 8% more fluid was recovered. The difference was both statistically significant and clinically relevant given that 17.4% more diagnoses, 6.9% fewer complications, and 8.8% fewer technical failures were recorded. Based on these results, we recommend performing BAL using plastic tubing between the 50 mL syringe and the working channel of the flexible bronchoscope when carrying out manual instillation and suction.

A high blood lactate induced by heavy exercise does not affect the increase in submaximal $$\dot V{\text{O}}_2 $$ with hyperoxia

Few studies evidenced an enhancement in oxygen uptake (VO2) during submaximal exercise in hyperoxia. This O2 "overconsumption" seems to increase above the lactate threshold. The aim of this study was to determine whether the hyperoxia-induced enhancement in VO2 may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean VO2 max= 53.8 ml min-1 kg-1) were randomized to two series of exercise in either normoxia or hyperoxia corresponding to an inspired O2 fraction (FIO2) of 30%. Each series consisted of 6 min cycling at 50% VO2 max (Moderate1), 5 min cycling at 95%VO2 max (Near Max) and then 6 min at 50% VO2 max (Moderate2). In both series Near Max was performed in normoxia. VO2 was significantly greater under hyperoxia than in normoxia during Moderate1 (2192 +/- 189 vs. 2025 +/- 172 ml min-1) and during Moderate2 (2352 +/- 173 vs. 2180+ /- 193 ml min-1). However, the effect of the high FIO2 was not significantly different on VO2Moderate2 (+172+/-137 ml min-1 with [La] approximately 6 mmol l-1) compared to VO2Moderate1 (+166 +/- 133 ml min-1 with [La] approximately 2.4 mmol l-1). [La] at the onset of Moderate2 was not different between normoxia and hyperoxia (10.1 +/- 2.2 vs. 10.9 +/- 1.6 mmol l-1). The results show that VO2 is significantly increased during moderate exercise in hyperoxia. But this O2 overconsumption was not modified by a high [La] induced by a prior heavy exercise. It could be concluded that lactate accumulation is not directly responsible for the increase in O2 overconsumption with intensity during exercise in hyperoxia.

Optoacoustic, Noninvasive, Real-Time, Continuous Monitoring of Cerebral Blood Oxygenation: An In Vivo Study in Sheep

Current, invasive cerebral oxygenation monitors require either retrograde jugular venous bulb cannulation or intraparenchymal probe insertion. There is no accurate, noninvasive, continuous monitor of cerebral blood oxygenation. The authors designed, built, and tested novel optoacoustic instrumentation that continuously measures blood oxygenation in the superior sagittal sinus (SSS) in vivo in 12 anesthetized sheep. In this technique, laser pulses generate acoustic signals, the amplitudes and slopes of which are proportional to oxyhemoglobin saturation in the SSS. Optoacoustic signals from the SSS measured through the scalp and cranium were compared with directly measured oxyhemoglobin saturation in blood withdrawn from the cannulated SSS. In the first experiments (feasibility), FIO2 changes produced rapid corresponding changes in optoacoustic signals and arterial oxygen saturation. In the second experiments (validation), the authors correlated oxyhemoglobin saturation in the SSS with optoacoustic signals and developed quantifying algorithms. In eight of nine validation experiments, the authors quantified optoacoustic signals by subtracting the temporal profile at low FIO2 (0.08-0.1) from profiles at higher FIO2 and integrating those signals in the range from 3 to 5 micros. In each validation experiment, optoacoustic signals showed tight temporal association and good linear correlation with measured oxyhemoglobin saturation (r2 0.75 to 0.99 for eight individual experiments). The optoacoustic system detects signals induced in the SSS and optoacoustic signals from the SSS linearly correlate with oxyhemoglobin saturation. The data suggest that the optoacoustic technique merits clinical evaluation.

Novel Self-inflating Resuscitators Maintaining High FiO2with High Minute Ventilation

Background: Self inflating resuscitators are widely used for the patients who need positive pressure ventilation during transport. During self inflating resuscitator ventilation, the may decreases even with the use of the oxygen reservoir. Such phenomenon may increase the difficulty and risk of transport of the critically ill patients. Twin self inflating resuscitator was assembled by being modified from two conventional ones to achieve more stable . Methods: The twin self inflating resuscitator and one conventional adult self inflating resuscitator were tested on a test lung. In the twin resuscitator, two adult self inflating resuscitators were connected serially without distal unidirectional valve plate. The resuscitators were compressed at variable tidal volumes, respiratory rates and oxygen flow rates, guided by the monitor. Results: With conventional self inflating resuscitator ventilation, the was maintained over 95% until minute ventilation of at respectively 5, 10, 15 L/min oxygen flow rate. With serial type, the started to decrease with the minute ventilation over at 5, 10, 15 L/min oxygen flow rate. Conclusions: By simple connection of two self inflating resuscitators, the during self inflating resuscitator ventilation could be maintained during almost two times of minute ventilation compared to conventional ones.

Transfusion-Related Acute Lung Injury (TRALI): A Retrospective Analysis of 119 Cases.

Following Institutional Review Board approval, detailed data involving patient, product, and clinical factors was retrospectively gathered on 119 TRALI cases identified between 1991 and 1998 at University of Alberta Hospital in Edmonton, AB. This data was gathered as a complement to previously published work (Silliman et al, Blood 2003: 101: 454) on the epidemiology and etiology of TRALI which consisted of 90 sequentially-identified TRALI reactions in 81 patients. In the current study we sought additional detailed clinical and laboratory data on these cases and others identified during the stated time period. Our aim was to help characterize patients who get TRALIs and/or to identify clinical correlates of TRALI. All TRALI were identified on the basis of 1) acute onset of respiratory distress mandating urgent medical intervention as the predominant symptom (peripheral or central cyanosis was noted in virtually all cases and all required supplemental oxygen.); 2)symptoms temporally associated with transfusion of a blood product, and 3) no other cause for the acute respiratory deterioration evident. All diagnoses were reviewed by a transfusion medicine physician. Data was abstracted onto prepared questionnaire forms by 2 of us (LKB and LP) following detailed review of hospital charts and transfusion service records. An electronic database was then prepared using deidentified forms (unique patient code substituted for name and date of birth) and data entered by double entry to assure accuracy. Not all data fields were available on all patients. Preliminary data analysis of these TRALI cases reveals:1.Mean age of TRALI patients: 39.07 years (range 3 mos – 91 years).2.Gender: 49% male, 51 % female3.Hypoxemia: Arterial blood gases available on 41 cases. All hypoxemic on basis of O2 saturation < 90% on room air or higher FIO2.4.Diagnosis of malignancy: 77 / 119 = 65 % of which 54 (45%) were on chemotherapy. Most of the malignancies were hematological.5.Cardiopulmonary bypass: 13 patients: 9 coronary artery bypass grafts (one with valve replacement), 3 valve replacements and one ventricular septal defect closure6.Surgery: 58 cases with preceding surgery within 1–2 days of TRALI (17 central venous cather insertions, 4 endoscopy or bronchoscopy and 37 other major or minor surgery)7.Time from initiation of transfusion to onset of symptoms: < 15 mins (n=15), 15 min – 1 hr (n=56), 1–2 hrs (n=14), unknown (n = 34)8.Type of venous access used for transfusion: central line (n = 24), peripheral line (n=7), unknown (n=63)9.Pre-transfusion white blood cell (WBC) count x 10-9/L: Available in 107 cases.. Average = 13.8 (range 0.1 – 259). WBC > 30: n = 8; WBC < 1.5: n = 40; WBC 1.1–1.5: n = 3; WBC 0.6–1.0: n = 9; WBC 0.3–0.5: n = 21; WBC 0.2: n = 4; WBC 0.1: n=3.Although these data are retrospective and limited, they suggest that TRALI can be seen in any age group, is equally common in males and females, is most often rapid in onset (15 min – 1 hour), and can occur even at low WBCs. Although it is unclear from the present data alone, an increased frequency of TRALI was noted in a nested case-control study (see reference above) in patients with underlying hematological malignancy and antecedent cardiopulmonary bypass.

Endothelin B Receptor Blockade Attenuates Pulmonary Vasodilation in Oxygen-Ventilated Fetal Lambs

Background: Endothelin-1 (ET-1) contributes to the regulation of pulmonary vascular tone in the normal ovine fetus and in models of perinatal pulmonary hypertension. In the fetal lamb lung, the effects of ET-1 depend on the balance of at least two endothelin receptor subtypes: ET_A and ET_B. ET_A receptors are located on smooth muscle cells and mediate vasoconstriction and smooth muscle proliferation. Stimulation of endothelial ET_B receptors causes vasodilation through release of nitric oxide and also functions to remove ET-1 from the circulation. However, whether activation of ET_B receptors contributes to the fall in pulmonary vascular tone at birth is unknown. Objective and Methods: To determine the role of acute ET_B receptor blockade in pulmonary vasodilation in response to birth-related stimuli, we studied the hemodynamic effects of selective ET_B receptor blockade with BQ-788 during mechanical ventilation with low (<10%) and high FiO₂ (100%) in near-term fetal sheep. Results: Intrapulmonary infusion of BQ-788 did not change left pulmonary artery (LPA) blood flow and pulmonary vascular resistance (PVR) at baseline. In comparison with controls, BQ-788 treatment attenuated the rise in LPA flow with low and high FiO₂ ventilation (p < 0.001 vs. control for each FiO₂ concentration). PVR progressively decreased during mechanical ventilation with low and high FiO₂ in both groups, but PVR remained higher after BQ-788 treatment throughout the study period (p < 0.001). Conclusions: We conclude that selective ET_B receptor blockade attenuates pulmonary vasodilation at birth. We speculate that ET_B receptor stimulation contributes to pulmonary vasodilation at birth in the ovine fetus.

Fetal effects of maternal supplementary oxygen during Caesarean section

This review summarises the current issues, knowledge and research on the effects of maternal supplementary oxygen therapy on the fetus during Caesarean section. This is a controversial subject since supplementary oxygen has the potential to confer both benefits and also harm to the fetus, depending on the circumstances. For elective Caesarean section, breathing room air under regional anaesthesia or 30% oxygen under general anaesthesia is not associated with either maternal or fetal hypoxia. A prolonged uterine-incision-to-delivery (U-D) interval of up to 310 s is not a major factor per se for development of fetal hypoxia or acidosis, and no benefits could be derived from breathing supplementary oxygen in this situation. Although it appears rational to provide supplementary oxygen in the presence of a hypoxic or compromised fetus, to achieve meaningful increases in fetal oxygenation, a very high inspired oxygen fraction (FiO2) is required. However, it still remains unclear whether this is beneficial for the fetus. The process of damage to the hypoxic fetus is one of oxidative stress mediated by free radicals generated during reperfusion (ischaemia-reperfusion injury). Independently, hyperoxia from breathing supplementary oxygen also induces formation of free radicals by direct mitochondrial electron transfer. Although hyperoxia could lessen the severity of fetal hypoxia, there is also a theoretical risk of an enhanced reperfusion injury. This issue has not been resolved in a clinical study, but an animal study reported enhanced formation of free radicals after an episode of fetal hypoxia in the group receiving supplementary oxygen. For elective Caesarean section, current evidence suggests that supplementary oxygen is unnecessary. For emergency Caesarean section, further data are required before a conclusion can be made for its beneficial and adverse effects. Improvement of fetal oxygenation should be the primary objective, and this is achievable in the short term by using a very high FiO2. Although there is also a possibility of an enhanced reperfusion injury, particularly in the preterm and non-labouring patients, further data are necessary before a conclusion can be made.

Infection with Ureaplasma urealyticum: is there a specific clinical and radiological course in the preterm infant?

Background: Despite having mild early respiratory disease, many preterm babies develop chronic lung disease (CLD). Intrauterine infection with Ureaplasma urealyticum has been associated with preterm labour and CLD. Objective: To...

Infection with Ureaplasma urealyticum: is there a specific clinical and radiological course in the preterm infant?

<b>Background:</b> Despite having mild early respiratory disease, many preterm babies develop chronic lung disease (CLD). Intrauterine infection with <i>Ureaplasma urealyticum</i> has been associated with preterm labour and CLD. <b>Objective:</b> To test the hypothesis that infection with <i>U urealyticum</i> results in a specific clinical and radiological picture in the first 10 days of life. <b>Methods:</b> Retrospective study of 60 ventilated babies &lt; 30 weeks gestation, who had tracheal secretions tested for <i>U urealyticum</i>. Placental histology was reviewed by a paediatric pathologist for signs of chorioamnionitis. Chest radiographs were independently reviewed by two paediatric radiologists according to previously agreed criteria. All reviewers were blinded to the infection status of the babies. <b>Results:</b> Twenty five babies were <i>U urealyticum</i> positive. These were more likely to experience chorioamnionitis (p = 0.004), premature rupture of membranes (p = 0.01), and spontaneous vaginal delivery (p = 0.09). <i>U urealyticum</i> positive babies had fewer signs of respiratory distress syndrome on early chest radiographs (p = 0.038), and they could be weaned from their ventilation settings (fraction of inspired oxygen (Fio₂) and mean airway pressure) more quickly in the first few days. Subsequently <i>U urealyticum</i> positive babies deteriorated clinically and radiologically. More often they required ventilation to be restarted (p = 0.051), a higher proportion being ventilated on day 10 (p = 0.027) with higher Fio₂ (p = 0.001) and mean airway pressure (p = 0.002). Their chest radiographs showed more emphysematous changes as early as day 5 (p = 0.045), with a pronounced difference by day 10 (p = 0.009). <b>Conclusions:</b> Preterm ventilated babies with <i>U urealyticum</i> in their tracheal secretions have a different clinical and radiological course, with less acute lung disease but early onset of CLD, compared with those with negative cultures.

Immediate post-operative effects of tracheotomy on respiratory function during mechanical ventilation

IntroductionTracheotomy is widely performed in the intensive care unit after long-term oral intubation. The present study investigates the immediate influence of tracheotomy on respiratory mechanics and blood gases during mechanical ventilation.MethodsTracheotomy was performed in 32 orally intubated patients for 10.5 ± 4.66 days (all results are means ± standard deviations). Airway pressure, flow and arterial blood gases were recorded immediately before tracheotomy and half an hour afterwards. Respiratory system elastance (Ers), resistance (Rrs) and end-expiratory pressure (EEP) were evaluated by multiple linear regression. Respiratory system reactance (Xrs), impedance (Zrs) and phase angle (φrs) were calculated from Ers and Rrs. Comparisons of the mechanical parameters, blood gases and pH were performed with the aid of the Wilcoxon signed-rank test (P = 0.05).ResultsErs increased (7 ± 11.3%, P = 0.001), whereas Rrs (-16 ± 18.4%, P = 0.0003), Xrs (-6 ± 11.6%, P = 0.006) and φ rs (-14.3 ± 16.8%, P = <0.001) decreased immediately after tracheotomy. EEP, Zrs, blood gases and pH did not change significantly.ConclusionLower Rrs but also higher Ers were noted immediately after tracheotomy. The net effect is a non-significant change in the overall Rrs (impedance) and the effectiveness of respiratory function. The extra dose of anaesthetics (beyond that used for sedation at the beginning of the procedure) or a higher FiO2 (fraction of inspired oxygen) during tracheotomy or aspiration could be related to the immediate elastance increase.

A new way of noninvasive ventilation in ICU patients. An innovation modification of the continuous positive airway pressure (CPAP) face mask Boussignac–Vygon in order to use it in chronic obstructive pulmonary disease (COPD) (type II) patients

Noninvasive mechanical ventilation (NIMV) is the support of the ventilation of the patient using kinds of mechanical means but without intubation. The advantages of NIMV are well known (autonomous interruption and adaptation, intervals in use, self-performed, no humidification needed, no sedation, possibility of expectorations, coughing, talking, feeding, and so on) and the disadvantages of IMV (during intubation [spasm, heart attack, dilatation of stomach], during IMV obstruction, ventilator-associated pneumonia [VAP], take-off, after intubation, tracheostomia). Among different types of NIMV (negative pressure [iron lung], positive pressure [intermittent positive pressure ventilation, spontaneous intermittent mechanical ventilation, PSV, BiPAP, PAV], CPAP), in recent years a face CPAP mask (Boussignac–Vygon) has been developed and used in a mode of CPAP ventilation. An O2 supply is used to create through a special valve mechanism continuous positive pressure in the airways. Although this mask is very effective to correct hypoxemia, it has two serious disadvantages: (1) it uses very high flow of O2 to create an effective CPAP, resulting in an uncontrolled FiO2 more than 60% (up to 95%) in the majority of cases; (2) it cannot be used in COPD II patients because the high FiO2 obligatory used overtreats hypoxemia ending not in correction, but in exacerbation of hypercapnia.

MKK3 Mitogen-Activated Protein Kinase Pathway Mediates Carbon Monoxide-Induced Protection Against Oxidant-Induced Lung Injury

The stress-inducible gene heme oxygenase (HO-1) has previously been shown to provide cytoprotection against oxidative stress. The mechanism(s) by which HO-1 provides this cytoprotection is poorly understood. We demonstrate here that carbon monoxide (CO), a byproduct released during the degradation of heme by HO, plays a major role in mediating the cytoprotection against oxidant-induced lung injury. We show in vitro that CO protects cultured epithelial cells from hyperoxic damage. By using dominant negative mutants and mice deficient in the genes for the various MAP kinases, we demonstrate that the cytoprotective effects of CO are mediated by selective activation of the MKK3/p38 beta protein MAP kinase pathway. In vivo, our experiments demonstrate that CO at a low concentration protects the lungs, extends the survival of the animals, and exerts potent anti-inflammatory effects with reduced inflammatory cell influx into the lungs and marked attenuation in the expression of pro-inflammatory cytokines.

Right ventricular to pulmonary artery conduit instead of modified Blalock-Taussig shunt improves postoperative hemodynamics in newborns after the norwood operation

Objective: Perioperative mortality, prolonged postoperative recovery after the Norwood procedure, and mortality between stage I and stage II might be related to shunt physiology. A right ventricular to pulmonary artery conduit offers a banded physiology in contrast to a Blalock-Taussig shunt. The purpose of this study was to assess the hemodynamic differences and their consequences in the postoperative course between Norwood patients with a Blalock-Taussig shunt and those with a right ventricular to pulmonary artery conduit. Methods From October 1999 until May 2002, 32 unselected consecutive patients underwent a Norwood procedure at the General Hospital Linz. The first 18 patients received a Blalock-Taussig shunt. In the remaining 14 patients we performed a right ventricular to pulmonary artery conduit. Both groups were compared. Results The diastolic blood pressure was significantly higher in the right ventricular to pulmonary artery conduit group ( P < .001). Despite a higher FIO 2, PO 2 levels tended to be lower in the first 5 postoperative days. At the age of 3 months, catheterization labora- tory data showed a lower Qp/Qs ratio in the same group (0.86 [0.78; 1] versus 1.55 [1.15; 1.6]; P = .005) and a higher dp/dt (955 [773; 1110] vs 776 [615; 907]; P = .018). (Descriptive data reflect medians and quartiles [in brackets].) Hospital survival was 72% in the Blalock-Taussig shunt group versus 93% in the right ventricular to pulmonary ar- tery conduit group. Mortality between stage I and stage II was 23% in the Blalock-Taussig shunt group versus 0% in the right ventricular to pulmonary artery conduit group. Conclusions A higher diastolic blood pressure and a lower Qp/Qs ratio were associated with a more stable and efficient circulation in patients with a right ventricular to pulmonary artery conduit. More intensive ventilatory support was necessary during the first postoperative days. We did not note any adverse effects of the ventriculotomy on ventricular performance.

Validation of Dysfunctional Ventilatory Weaning Response

PURPOSETo further clinically validate the defining characteristics of dysfunctional ventilatory weaning response (DVWR) in patients requiring long‐term mechanical ventilation.METHODSThe Weaning Readiness Assessment Scale (WRAS), a 28‐item, 60‐point scale used to assess patients' readiness to wean from mechanical ventilation, was used to collect data on a large data set of 533 patients who were on mechanical ventilation &gt;4 days. Data were collected every other day until the patient was weaned, discharged, or expired. The WRAS is comprised of two subscales: the physiological/behavioral (PPBB) subscale and ventilatory subscale (VVV).FINDINGSA content validity index of 0.88 indicated that the variables and their scoring ranges were appropriate for the study population. Interrater and test‐retest reliability measures were 0.93 and 0.92, respectively. Internal consistency (Cronbach's alpha, p&lt;0.05) for the PPBB and VVV subscales were .69 and .76, respectively. Data were available on 533 subjects and analyzed by principal component extraction with varimax rotation, resulting in a two‐factor solution with strong loadings for 17 variables. In addition, preliminary one‐way analysis of variance showed statistical significance (p&lt;0.05) on these 17 variables. Where statistical significance was not present, the trend was in the expected direction.DISCUSSIONThese data imply that 10 of the 17 variables alone and in combination affect weaning from mechanical ventilation and lend support to the existing defining characteristics of DVWR. In addition, data revealed 7 statistically significant symptom variables affecting weaning from mechanical ventilation that are currently not listed as defining characteristics for DVWR: need for multiple vasopressors, fluid overload, multiple antibiotic use, bronchodilator use, need for high FiO2, and high PEEP levels.CONCLUSIONSFor most patients, weaning from mechanical ventilation is a smooth transition. Patients who require &gt;3 days of mechanical ventilation are an expensive patient population for acute care hospitals. Forty percent to 42% of mechanically ventilated patients either fail the initial spontaneous breathing trial (24%) or are extubated and require reintubation (16%–18%). The weaning process for long‐term mechanically ventilated patients has fiscal and psychosocial ramifications for the patient, family and friends, and healthcare providers.