Difference In PaCO2 Research Articles

What do You Expect from Patients with Severe Head Trauma?

Background:Head trauma is one of the most common mortality and morbidity causes in adolescent. Numerous studies have been conducted on changes in laboratory results and mortality and morbidity prognostic factors; however, the obtained results have been varied and controversial. The aim of this study is to evaluate changes in laboratory findings and arterial blood gas (ABG) analyses test at admission and investigation of the relation between these changes with outcomes in patients with traumatic brain injury.Materials and Methods:In this study, laboratory and metabolic variables were compared in patients with severe brain trauma and normal subjects. Laboratory and metabolic variables and ABG were measured on admission in patients with severe brain trauma and then compared with normal values. At last, the correlation between these variables with the prognosis in the patients was studied.Results:Of 93 studied patients, 82 were male and 11 were female with the mean age of 30.54 years. Among the studied variables, prothrombin time (PT), partial thromboplastin time, international normalized ratio (INR), creatinine (Cr), blood sugar, sodium (Na+), potassium, white blood cell, and blood urea nitrogen increased while hemoglobin and platelet decreased significantly. Regarding the ABG results, the difference in PaCO2, HCO3, and SO2 at values was significant; whereas there were no statistical significant difference between the discharged and expired patients. In contrast, PT, INR, Cr, and Na had significant difference comparing the discharged and expired patients.Conclusion:Laboratory variables do change in patients with severe brain trauma; these changes are influential on patient prognosis, especially in case of PT, INR, Cr, and Na.

Breathing and Blood Pressure in Conscious and 1% Isoflurane Anesthetized Mice

Isoflurane is a commonly used inhaled anesthetic that can be adjusted for level of anesthetic depth and offers a rapid recovery for both clinical settings and laboratory animal research. Initial studies in our laboratory indicated no difference in PaCO2 (36.7±2.4 vs. 34.8±2.6 mmHg) or pH (7.43±0.02 vs. 7.43±0.02) between conscious (NO ISO) and 1% isoflurane (ISO) exposed CD‐1 mice. Our purpose was to investigate if arterial blood sampling with 1% ISO is a suitable alternative to conscious sampling for monitoring ventilation in a commonly studied mouse strain. This study aimed to test the hypothesis that breathing patterns and blood pressure in conscious and lightly isoflurane anesthetized B6/C57 mice are similar. At 3 months of age, 8 male B6/C57 mice (27.5±1.9 g body weight; MEAN±SD) underwent whole body unrestrained barometric plethysmography to quantify the pattern of breathing. Mice were tested during the light cycle with an isoflurane vaporizer preceding the animal chamber and a vacuum following the chamber (100 mL/min) to prevent accumulation of ISO. After a 30 min acclimation period with air (20.93% O2, balanced N2), mice were exposed to 5 minutes of the following: 2% ISO/air, 1% ISO/air, 1% ISO/10% O2 (hypoxia),1% ISO/air, 1% ISO/5% CO2 (hypercapnia); the last minute of each gas exposure was analyzed with Ponemah™ software. The same mice were administered these gas exposures without ISO (NO ISO) a week later; quiet baseline breathing was considered during this exposure as the 5 minutes when mice were not moving or sniffing in the cage. Breathing frequency (F; breaths/min), tidal volume (TV; mL/breath), and minute ventilation (MV; mL/min) were quantified; NO ISO vs. 1% ISO (MEAN±SD; *=p<0.05) shown in the following text. Quiet breathing compared to 1%ISO/air was not different for F: 185±30 vs. 168±31, TV: 0.29±0.04 vs. 0.31±0.16, or MV: 57.5±10.6 vs. 52.6±26.4. A blunted hypoxic response resulted with ISO; this was due to a lower F and MV (F: 265±31 vs. *176±22, TV: 0.41±0.07 vs. 0.39±0.14, MV: 123.8±27.1 vs. *72.3±29.9). Hypercapnia also resulted in a reduced response to ISO with F, TV and MV differences (F: 352±28 vs. *157±23, TV: 0.63±0.07 vs. *0.43±0.21, MV: 237.1±53.7 vs. *72.6±45.3). Conscious and 1% ISO arterial blood sampling in B6/C57 mice showed no difference in PaCO2 (38.8±1.9 vs. 35.2±2.3 mmHg), but differences did emerge with pH (7.43±0.02 vs. *7.38±0.03). Additional experiments were conducted to measure blood pressure with the volume‐pressure recording tail cuff method to determine other possible systemic changes with ISO, but no differences were uncovered (96±8 vs. 85±11 mmHg) although the data did approach significance. These experiments demonstrate the pattern of quiet breathing, ventilation and blood pressure are similar in conscious and 1% ISO exposed mice. However, the capacity to respond to respiratory stressors is attenuated with 1% ISO. Overall due to the near significant p‐values, along with clear differences from hypoxia/hypercapnia, we do not recommend blood sampling with 1% ISO as an alternative to monitoring conscious ventilation.Support or Funding InformationFunded by 1 R15 HD076379‐01A1, AML supported by McDevitt Fellowship, CNR supported by 1 R15 HD076379‐01A1S1.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Nasopharyngeal Airway Versus Laryngeal Mask Airway During Diagnostic Flexible Fiber-Optic Bronchoscope in Children

Background: Pediatric fibreoptic diagnostic bronchoscope under general anesthesia using Supraglottic devices as Laryngeal Mask Airway (LMA) and nasopharyngeal airway (NPA) are one of the variable techniques used for patient’s ventilation during this procedure. Objective: We studied the effect of both devices on hypoxemia, the duration of the procedure, recovery time and the overall propofol consumption. Methods: Ninety patients of both sexes, aged 5-10 years, American society of Anesthesiology class I & II scheduled for diagnostic fibreoptic bronchoscope under general anesthesia were divided randomly into two equal groups; LMA group & NPA group, during the procedure: heart rate, non invasive blood pressure, peripheral arterial oxygen saturation (SpO2), arterial partial pressure of carbon dioxide(PaCO2), time of procedure, recovery time and total dose of propofol were measured and compared for each patient in both groups. Results: Hypoxemia & desaturation incidence was more in LMA group than NPA group with high significant difference (p-value 0.005). Also the duration of procedure, recovery time in PACU, and total dose of propofol consumed were significantly less in the NPA group (p< 0.001). With no difference in hemodynamic status and PaCO2. Conclusion: The use of NPA as supraglottic ventilating device for children undergoing diagnostic flexible fibreoptic bronchoscopy is considered a good alternative for shortening the bronchoscopy time with less incidence of hypoxemia and better recovery time compared to LMA.

Effect of ischemic preconditioning combined with ?7 nAchR agonists on limb ischemia-reperfusion lung injury in rat

Objective: To investigate the effect of ischemic preconditioning combined with α7 nAchR agonists on limb ischemia-reperfusion lung injury in rats. Methods: Fifty healthy male Sprague-Dawley rats weighing 230-280 g were randomly divided into 5 groups: sham operation group (S, also means the control group), model group(M), model and ischemic preconditioning (IP) group, model and α7 nAchR agonists group (PNU) and model and united treatment (U) group. The model of lung injury was induced by 3 h of ischemia and 3 h of reperfusion. The arterial blood was collected at 3 h- reperfusion for blood gas analysis; The lung tissues were collected for determination of Pulmonary coefficient, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity and lung tissue inflammatory cytokines (IL-6 and TNF-a). The pathological changes of lung tissues were observed under light microscope, and the pathological score of lung tissue was conducted. Results: Compared with S group, the PaO2, pH and the activity of SOD in lung tissue of M group at 3 h reperfusion were significantly decreased, Pulmonary coefficient, MDA,IL-6, TNF-a and pulmonary pathological score of lung tissue were significantly increased (P<0.05), the difference of PaCO2 was not statistically significant (P>0.05). Compared with M group, arterial PaO2and lung SOD activity of IP group, PNU Group, U group at 3 h-reperfusion decreased, while Pulmonary coefficient, lung group, MDA,IL-6, TNF-a and pulmonary pathological score of lung tissue were significantly increased (P<0.05), there was no statistically significant difference in pH and PaCO2 between the two groups (P>0.05). Compared with IP group and PNU group, PaO2 and SOD activity of lung tissue decreased in U group at 3 h reperfusion, Pulmonary coefficient, MDA, IL-6, TNF-a, pulmonary pathology scores of lung tissue increased (P<0.05). There was no significant difference in PH and PaCO2 between the two groups (P>0.05). Conclusion: Ischemic preconditioning and α7 nAchR agonists can attenuate limb ischemia-reperfusion lung injury in rat to a certain extent, and the combined effect of the two is better than the separate application.

Evaluation of oxygen administration with a high-flow nasal cannula to clinically normal dogs.

OBJECTIVE To evaluate the safety and efficacy of oxygen administration by use of a high-flow nasal cannula (HFNC) in sedated clinically normal dogs. ANIMALS 6 healthy adult dogs undergoing routine dental prophylaxis. PROCEDURES Dogs were sedated with butorphanol tartrate and dexmedetomidine. An esophageal balloon catheter was inserted into the esophagus, a double-pronged nasal cannula was inserted into the nares, and a catheter was inserted into the dorsal pedal artery. Dogs were positioned in right lateral recumbency. After a 6-minute acclimation period, baseline blood gas values and transpulmonary pressure were measured. Dogs then received supplemental oxygen via conventional oxygen therapy (COT) at a rate of 100 mL/kg/min (COT-100 treatment) and an HFNC at a rate of 20 L/min (HF-20 treatment) and 30 L/min (HF-30 treatment). Arterial blood gas and transpulmonary pressure were measured after a 6-minute acclimation period for each oxygen delivery method. Radiographs were obtained before and after oxygen administration to evaluate gastric distension. RESULTS Median Pao2 was significantly higher for HF-20 (519.9 mm Hg) and HF-30 (538.1 mm Hg) treatments, compared with median Pao2 for the COT-100 treatment (202.9 mm Hg). The Pao2 did not differ significantly between the HF-20 and HF-30 treatments. There was no significant difference in Paco2 or change in transpulmonary pressure between baseline and any oxygen delivery method. CONCLUSIONS AND CLINICAL RELEVANCE In this study, HFNC appeared to be a safe and effective method for oxygen delivery to sedated healthy dogs. Further studies are needed to evaluate use of HFNCs for oxygen administration to hypoxemic patients.

Apnoeic oxygenation in adults under general anaesthesia using Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) – a physiological study

BackgroundApnoeic oxygenation during anaesthesia has traditionally been limited by the rapid increase in carbon dioxide and subsequent decrease in pH. Using a Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) technique a slower increase in carbon dioxide than earlier studies was seen. Notably, apnoeic oxygenation using THRIVE has not been systematically evaluated with arterial blood gases or in patients undergoing laryngeal surgery. The primary aim of this study was to characterize changes in arterial PO2, PCO2 and pH during apnoeic oxygenation using THRIVE under general anaesthesia. MethodsAdult patients, (ASA I-II), undergoing shorter laryngeal surgery under general anaesthesia, were oxygenated during apnoea using THRIVE, 100% oxygen, 40–70 litres min−1. A cohort was randomized to hyperventilate during pre-oxygenation. Vital parameters and blood gases were monitored. ResultsThirty-one patients, age 51 (34–76) yr, BMI 25 (4) were included. Mean apnoea time was 22.5 (4.5) min. Patients were well oxygenated, SpO2 was never below 91%. The increase in PaCO2 and end-tidal CO2 during apnoea was 0.24 (0.05) and 0.12 (0.04) kPa min−1, respectively. Hyperventilation during pre-oxygenation generated no difference in PaCO2 at the end of apnoea compared with normoventilation. ConclusionsThis physiological study of apnoeic oxygenation using THRIVE during laryngeal surgery shows that this technique is able to keep patients with mild systemic disease and a BMI <30 well oxygenated for a period of up to 30 min. The THRIVE concept makes it possible to extend the apnoeic window but monitoring of CO2 and/or pH is recommended. Clinical trial registrationNCT02706431.

Ventilation of rats with room air is more adequate than ventilation with pure oxygen

O presente estudo investigou se a ventilação de ratos com cilindros de ar comprimido é possível e se esta técnica seria melhor do que o procedimento de ventilação com cilindros de oxigênio comprimido. Vinte ratos foram divididos em dois grupos de dez animais cada. Em um grupo os animais foram ventilados com ar ambiente e o outro grupo foram ventilados com oxigênio puro. Parâmetros dos gases sanguíneos e o índice de oxigenação foram comparados entre os grupos. O grupo dos animais ventilados com oxigênio puro teve hiperóxia no começo e no fim da ventilação mecânica. A PaO2 ficou adequada nos aniamais ventilados com ar ambiente. Não houve diferença significativa na PaCO2 entre os dois grupos no começo e no fim da ventilação mecânica. A média do índice de oxigenação (razão PaO2/FiO2) foi significativamente mais alta no grupo de ar ambiente quando comparado com o grupo do oxigênio puro no começo e no fim da ventilação mecânica (5min: p &lt; 0,001e 60min: p &lt; 0,002). Em conclusão, ventilar ratos com ar ambiente é mais vantajoso do que quando realizado com oxigênio puro porque permite oxigenação adequada sem causar hiperóxia.

The effect of ulinastatin on blood gas analysis in rabbits with acute lung injury following a blast

Objective To study the effect of ulinastatin (UTI) on blood gas analysis in rabbits with acute lung injury (ALI) after an explosion. Methods A total of 24 healthy New Zealand white rabbits were made to be ALI models by an explosion at a distance of 11 cm.The rabbits met the criteria of ALI, and were randomly(random number) divided into A and B groups. In group B, rabbits received UTI injected at 0.5 h, 6 h, 12 h, 24 h after modeling.In group A, an equal volume of saline was given to rabbits instead at the same intervals after modeling. Arterial blood pH, carbon dioxide partial pressure (PaCO2) and partial pressure of blood oxygen(PaO2) were determined by a portable blood gas analyzer before modeling and at given intervals after modeling. All rabbits were sacrificed after 48 h later. The pathological changes of lung tissue were observed with naked eye and extent of lung injury with HE staining. Results Compared with group A, pulmonary edema and infiltration of inflammatory cells in the lungs of rabbits in group B were less significant. The blood gas analysis showed there were significant difference in pH at 24 h after injury between group A(7.24 ± 0.07) and group B(7.35 ± 0.06), P<0.05.There was significant difference in PaO2 at 24 h after injury between group A(50.5±9.9)mmHg and group B (78.1±8.4)mmHg, P<0.05.And there was significant difference in PaCO2 at 24 h after injury between group A(52.4±5.5)mmHg and group B(42.8±4.5)mmHg, P<0.05. Conclusion UTI can significantly reduce acidosis, PaCO2 and increase PaO2 in rabbits with ALI following a blast, improving oxygenation and mitigating lung histopathological changes. Key words: Blast injuries; Acute lung injury; Ulinastatin; Blood gas analysis; Pathology

Efficacy of auto-trilevel positive airway ventilation in hypercapnic patients with overlap syndrome

To observe the efficacy of auto-trilevel positive airway pressure (Auto-trilevel PAP) ventilation in overlap syndrome (OS) patients with hypercapnia. From October 2012 to May 2014, 21 OS patients with a PaCO2> 45 mmHg (1 mmHg = 0.133 kPa) and coexisting stable chronic obstructive pulmonary diseases (COPD) and moderate-to-severe OSAS were recruited. Three different positive airway pressure (PAP) modes of ventilators (SOMNOvent auto-S, Weinmann Inc, Germany) were employed for 8 hours per night with each mode at each night and two nights' interval without any treatment among different modes. Under mode one, the expiratory positive airway pressure (EPAP) issued by bilevel positive airway pressure (BiPAP) was titrated as the minimal positive pressure for a disappearance of snoring. The same inspiratory positive airway pressure (IPAP) titrated by end tidal CO2 levels under mode 1 was used under modes 2 and 3 as well. However, the EPAP issued by BiPAP under mode 2 was 3 cmH2O (1 cmH2O = 0.098 kPa) higher than that under mode 1. Under mode 3 with autotrilevel PAP, the beginning of EPAP was set the same as that under mode 1 while the end of EPAP (EEPAP) was automatically adjusted based on upper airway patency condition. Comparisons were made for parameters before and after treatment as well as among different ventilation modes. The following parameters were compared such as nocturnal apnea hypopnea index (AHI), minimal SpO2 (miniSpO2), arousal index, sleep efficiency, morning PaCO2 and Epworth sleepiness score (ESS). Compared with the parameters pre-therapy, modes 1-3 showed a significant decrease in nocturnal AHI (6.3 ± 1.3), (3.1 ± 1.0), (3.6 ± 0.6) vs (38.6 ± 11.3) events/h), arousal index ((7.0 ± 1.1), (5.1 ± 0.9), (4.2 ± 1.7) vs (27.5 ± 5.4) events/h), morning PaCO2 (42.4 ± 3.8), (47.9 ± 2.6) and (43.2 ± 3.3) vs (57.3 ± 4.3) mmHg and daytime ESS (7.2 ± 1.3, 7.4 ± 1.3 and 5.3 ± 1.5 vs 11.4 ± 2.7), but a significant increase in nocturnal miniSpO2 (82.3 ± 5.4), (89.6 ± 3.9) and (90.3 ± 3.2) vs (62.4 ± 11.3) mmHg and sleep efficiency caused (71.3 ± 5.2)%, (79.4 ± 4.3)% and (83.2 ± 4.4)% vs (59.8 ± 6.3)% (all P < 0.01). Comparison of 3 modes demonstrated that, with the same IPAP, mode 3 resulted in the lowest arousal index, daytime ESS and the highest sleep efficiency. Comparison of modes 1 and 2 revealed a statistically lower AHI but higher miniSpO2 and morning PaCO2 under mode 2 (all P < 0.01). Compared with mode 1, mode 3 showed a lower AHI, higher miniSpO2 (all P < 0.01), but there was no significant difference in PaCO2 at the end of therapy. Compared with mode 2, mode 3 showed a significant lower PaCO2 (P < 0.01), but there was no significant difference in AHI and miniSpO2. Auto-trilevel PAP ventilation is superior to fixed BiPAP ventilation in the treatment of hypercapnic OS since this novel PAP mode can achieve a higher efficacy in simultaneous removal of residual apnea hypopnea events and correction of hypercapnia and yield a higher sleep quality and lower daytime sleepiness.

Hypercapnia and Acidosis During Open and Thoracoscopic Repair of Congenital Diaphragmatic Hernia and Esophageal Atresia

We aimed to evaluate the effect of thoracoscopy in neonates on intraoperative arterial blood gases, compared with open surgery. Congenital diaphragmatic hernia (CDH) and esophageal atresia with tracheoesophageal fistula (EA/TEF) can be repaired thoracoscopically, but this may cause hypercapnia and acidosis, which are potentially harmful. This was a pilot randomized controlled trial. The target number of 20 neonates (weight > 1.6 kg) were randomized to either open (5 CDH, 5 EA/TEF) or thoracoscopic (5 CDH, 5 EA/TEF) repair. Arterial blood gases were measured every 30 minutes intraoperatively, and compared by multilevel modeling, presented as mean and difference (95% confidence interval) from these predictions. Overall, the intraoperative PaCO2 was 61 mm Hg in open and 83 mm Hg [difference 22 mm Hg (2 to 42); P = 0.036] in thoracoscopy and the pH was 7.24 in open and 7.13 [difference -0.11 (-0.20 to -0.01); P = 0.025] in thoracoscopy. The duration of hypercapnia and acidosis was longer in thoracoscopy compared with that in open. For patients with CDH, thoracoscopy was associated with a significant increase in intraoperative hypercapnia [open 68 mm Hg; thoracoscopy 96 mm Hg; difference 28 mm Hg (8 to 48); P = 0.008] and severe acidosis [open 7.21; thoracoscopy 7.08; difference -0.13 (-0.24 to -0.02); P = 0.018]. No significant difference in PaCO2, pH, or PaO2 was observed in patients undergoing thoracoscopic repair of EA/TEF. This pilot randomized controlled trial shows that thoracoscopic repair of CDH is associated with prolonged and severe intraoperative hypercapnia and acidosis, compared with open surgery. These findings do not support the use of thoracoscopy with CO2 insufflation and conventional ventilation for the repair of CDH, calling into question the safety of this practice. The effect of thoracoscopy on blood gases during repair of EA/TEF in neonates requires further evaluation. (ClinicalTrials.gov Identifier: NCT01467245).

Effect of inhaled budesonide before operation on inflammatory responses to one-lung ventilation in patients undergoing thoracotomy

Objective To evaluate the effect of inhaled budesonide before operation on the inflammatory responses to one-lung ventilation (OLV) in patients undergoing thoracotomy.Metheds Fifty ASA Ⅰ or Ⅱ physical status patients,aged 20-60 yr,weighing 50-80 kg,undergoing pulmonary lobectomy,were randomly divided into 2 groups (n =25 each):control group (group C) and budesonide group (group B).The patients inhaled normal saline and budesonide 1 mg for 20 min before operation in groups C and B,respectively.Before OLV (T1),at 30 min after OLV (T2),and at 24 and 48 h after operation (T3-4),arterial blood samples were collected for blood gas analysis and venous blood samples were collected for determination of serum concentrations of TNF-α,IL-1,IL-6,IL-8 and IL-10.Oxygenation index was calculated at T1-4.Airway peak pressure,airway plateau pressure and lung compliance were recorded at T1 and T2.Broncho-alveolar lavage fluid (BALF) of the ventilated lung was collected at T1 and T2 for determination of concentrations of TNF-α,IL-1,IL-6,IL-8 and IL-10.Results Compared with group C,airway peak pressure and airway plateau pressure were significandy decreased at T1 and T2,ling compliance was increased at T1 and T2,the concentrations of TNF-α,IL-1,IL-6 and IL-8 in BALF were decreased at T2,oxygenation index was increased and serum concentrations of TNF-α,IL-1,IL-6,IL-8 and IL-10 were decreased at T2-4 in group B (P ＜ 0.05).There was no significant difference in PaCO2 at each time point between the two groups (P ＞ 0.05).Conclusion Inhaled budesonide before operation can inhibit the inflammatory responses to OLV in patients undergoing thoracotomy,and is helpful in improving lung function. Key words: Budesonide ; Respiration, artificial ; Inflammation

Effects of inspired oxygen concentration on ventilation, ventilatory rhythm, and gas exchange in isoflurane-anesthetized horses

To compare the effects of 2 fractions of inspired oxygen, 50% and > 95%, on ventilation, ventilatory rhythm, and gas exchange in isoflurane-anesthetized horses. 8 healthy adult horses. In a crossover study design, horses were assigned to undergo each of 2 anesthetic sessions in random order, with 1 week separating the sessions. In each session, horses were sedated with xylazine hydrochloride (1.0 mg/kg, IV) and anesthesia was induced via IV administration of diazepam (0.05 mg/kg) and ketamine (2.2 mg/kg) Anesthesia was subsequently maintained with isoflurane in 50% or > 95% oxygen for 90 minutes. Measurements obtained during anesthesia included inspiratory and expiratory peak flow and duration, tidal volume, respiratory frequency, end-tidal CO(2) concentration, mixed expired partial pressures of CO(2) and O(2), PaO(2), PaCO(2), blood pH, arterial O(2) saturation, heart rate, and arterial blood pressure. Calculated values included the alveolar partial pressure of oxygen, alveolar-to-arterial oxygen tension gradient (PaO(2) - PaO(2)), rate of change of PAO(2) - PaO(2), and physiologic dead space ratio. Ventilatory rhythm, based on respiratory rate and duration of apnea, was continuously observed and recorded. Use of the lower inspired oxygen fraction of 50% resulted in a lower arterial oxygen saturation and PaO(2) than did use of the higher fraction. No significant difference in PaCO(2), rate of change of PAO(2) - PaO(2), ventilatory rhythm, or other measured variables was observed between the 2 sessions. Use of 50% inspired oxygen did not improve the ventilatory rhythm or gas exchange and increased the risk of hypoxemia in spontaneously breathing horses during isoflurane anesthesia. Use of both inspired oxygen fractions requires adequate monitoring and the capacity for mechanical ventilation.

Transoral endoscopic surgery versus conventional thoracoscopic surgery for thoracic intervention: safety and efficacy in a canine survival model

Transoral endoscopic surgery has been shown to be feasible and safe in both humans and animal models. The purpose of this study was to evaluate the safety and efficacy of transoral and conventional thoracoscopy for thoracic exploration, surgical lung biopsy, and pericardial window creation. The animals (n = 20) were randomly assigned to the transoral endoscopic approach group (n = 10) or conventional thoracoscopic approach group (n = 10). Transoral thoracoscopy was performed with a flexible bronchoscope via an incision over the vestibulum oris. In conventional thoracoscopy, access to the thoracic cavity was obtained through a thoracic incision. Surgical outcomes (body weight, operating time, operative complications, and time to resumption of normal diet), physiologic parameters (respiratory rate, body temperature), inflammatory parameters [white blood cell (WBC) counts and C-reactive protein (CRP)], and pulmonary parameters (arterial blood gases) were compared for both procedures. The surgical lung biopsy and pericardial window creation were successfully performed in all animals except one animal in the transoral group. There was no significant difference in operating times between the groups. The increase in WBC in the transoral thoracoscopy group was significantly smaller on postoperative day 1 than in the conventional thoracoscopy group (p = 0.0029). The transoral group had an earlier return to preoperative body temperature (p = 0.041) and respiratory rate (p = 0.045) on day 7. With respect to pulmonary parameters, there was no significant difference in blood pH, pCO2, or PaCO2 between the transoral and transthoracic groups. All animals survived without complications 14 days after surgery. This study demonstrated that the transoral approach was comparable to conventional thoracoscopic surgery for lung biopsy and pericardial window creation in terms of safety and efficacy.

Effect of mechanical ventilation with different tidal volumes on pulmonary surfactant in dogs during cardiopulmonary resuscitation

Objective To observe the effects of mechanical ventilation with different tidal volumes (Vt) on the pulmonary surfactant in dogs during cardiopulmonary resuscitation (CPR) and discuss the strategy of mechanical ventilation for CPR.Methods A total of 24 healthy,adult and mongrel canines were randomly (random number) divided into three groups,namely control group (A),low Vt group (B) and high Vt group (C).Canines without ventricular fibrillation in group A were not supported with mechanical ventilation,while canines in group B and group C were induced to get ventricular fibrillation (VF) with pacing catheter inserted through right external carotid vein into the right ventricle.CPR was initiated with mechanical ventilation with different Vt for 6 hours after ventricular fibrillation.The Vt set in group B was 6 ml/kg body weight and Vt set in group C was 20 ml/kg body weight.The arterial blood gas analyses were tested in different intervals.The levels of phosphatidylchline in bronchia alveolus lavage fluid (BALF) was assayed with high performance liquid chromatography (HPLC).The ratio of wet and dry weight and the morphological change scores of lung tissue were calculated.Results After ventricular fibrillation,pH,PaO2 in both groups B and C decreased and PaCO2 increased in comparison with those before VF (P ＜ 0.05),while pH,PaO2 and PaCO2 were improved after mechanical ventilation.These was statistical difference in PaCO2 between group B and group C 2 h after mechanical ventilation (P ＜ 0.05).There was difference in HCO3-between group B and group C 6 h after ROSC.The rate of successful restoration of spontaneous circulation (ROSC) and the 72 h survival rate were 75％ and 50％ respectively in group B,and 62.5％ and 40％ respectively in group C.There were no statistically different between two groups (P ＞ 0.05).The levels of phosphatidylchline in BALF of group B and C greatly decreased compared with the group A (All P ＜0.01),while phosphatidylcholine detected in the group C decreased much more than that in the group B (P ＜0.01).The W/D ratio and morphological change scores in the group C were higher than those in the group B (P ＜ 0.01).Conclusion Low tidal volume ventilation can reduce the loss of pulmonary surfactant and mitigate pulmonary injury.Therefore it may be a protective ventilation strategy after resuscitation. Key words: Cardiopulmonary resuscitation; Mechanical ventilation ; Tidal volumes ; Lung injury ; Pulmonary surfactant

Effects of peritoneal jet ventilation on peritoneal oxygenation in pigs

Objective To evaluate the effects of peritoneal jet ventilation on peritoneal oxygenation in pigs.Methods Twenty-four pigs of both sexes (12-16 weeks,35-45 kg) were randomly divided into 3 groups (n=8 each): sham operation group (group S) ; peritoneal regular frequency jet ventilation group (16 bpm)(group N) and peritoneal high-frequency jet ventilation group (150 bpm) (group H).Oral tracheal intubation was performed.The animals were mechanically ventilated (VT 8-12 ml/kg,RR 12-16 bpm,I:E 1.0:1.5,FiO2 100％) via airway.Endotracheal tubes were inserted into abdomen through the incisions in the left lower (for peritoneal jet ventilation) and right upper quadrant (for outlet of air).Arterial blood PaO2 and PaCO2 were measured before (baseline) and at 30,60,90,120,150,180,210 and 240 s of peritoneal jet ventilation.Peritoneal jet ventilation was started after the lungs being mechanically ventilated for 35 min.Peritoneal jet ventilation was terminated when SpO2 dropped to SpO2 ＜ 90 ％.The duration of safe apnea (DSA,from the moment of begging of peritoneal jet ventilation to the time when PaO2 ＜ 60 mm Hg).Results PaO2 was significandy higher and DSA longer in group H than in groups S and N.But there was no significant difference in PaCO2 among the 3 groups.Conclusion Peritoneal high-frequency jet ventilation can significantly enhance the efficiency of peritoneal oxygenation and prolong DSA,while peritoneal regular frequency jet ventilation has no effect on peritoneal oxygenation. Key words: Respiration,artificial; Abdominal cavity; Peritoneum; Extracorporeal membrane oxygenation

Heated Moisture Exchanger (HME) and dead space ventilation. Is Isocapnic conditions unachievable in children?

Pulmonary dead space under general paediatric anaesthesia is a useful and relevant parameter [1]. We know that Heated Moisture Exchanger (HME) may lead to larger dead space and can negatively impact mechanical ventilation and gas exchange [1,2]. Smaller HME appears to be preferable, but there is a lack of information regarding their applicability and suitability in paediatric population [2]. On this issue, Kwon [3] analyzed the effects of HME on dead space in 20 relatively healthy paediatric patients, during their exposure to general anaesthesia for minor surgical procedures. We would like to congratulate the authors on their original hypothesis and results, which have clinical crucial implications. They reported that PaCO2 was significantly influenced by HME and the difference was correlated with weight (P < 0.001) and age (P = 0.002) of a patient. However, some major considerations and questions should be taken into consideration for the definitive clinical implications of their results. Firstly, clinical consequences of the removal of HME for 15 minutes without compensatory use of another artificial humidification may lead to serious implications, such as cilia and endothelial injury, increase in airway resistance, hypothermia, and etc. [2,4]. We have not been provided with any information in regards to these well known consequences, as well as whether or not any attempt was made to measure such complications. Secondly, there is insufficient information on the baseline of mechanical ventilation in both situations, which may influences our interpretation of higher pCO2 levels [4]. We have no information regarding the airway resistance, compliance, or peak airway pressure, which could help us for a better interpretation [5]. It would have been important to know the difference in PaCO2 between the baseline and after experimentation rather than just knowing the difference at the end of the experiment [3,4]. It is hard to determine whether or not the reduction is temporal and not a direct influence. Thirdly, main thrust of this report is on the alteration in physiological variables rather than clinically important outcomes, such as length mechanical ventilation or influence on weaning [5]. Overall, this report does not answer what are clinically impor tant questions, such as which device is better for humidifi cation, what effects of clinically important outcomes can be derived from this experiment and how best to use humidification without causing lung injury. In our opinion, this attractive and original report fails to even bridge a tile in this puzzle of humidification during healthy pediatric anesthesia.

Effects of pulmonary stretch reflex on lung injury in rabbits with acute respiratory distress syndrome.

Pulmonary stretch reflex plays an important role in regulation of respiratory movement. This study aimed to evaluate the effect of pulmonary stretch reflex on lung injury in rabbits with acute respiratory distress syndrome (ARDS). ARDS rabbits were given intratracheal infusion of hydrochloric acid and ventilated with neurally adjusted ventilatory assistance (NAVA) with a tidal volume (VT) of 6 mL/kg and the electrical activity of diaphragm (EAdi)-determined positive end expiratory pressure. After isolation of the bilateral vagus nerve trunk, the rabbits were randomized into two groups: sham operation (SHAM) group (n=5) and bilateral vagotomy (VAG) group (n=5). Gas exchange and respiratory mechanics were detected at baseline, after lung injury and 1, 2, and 3 hours after ventilation respectively. Pulmonary permeability index, pathological changes and inflammatory response were also measured. Compared with the SHAM group, PaO2/FiO2 in the VAG group decreased significantly 2 and 3 hours after ventilation (P<0.05). There was no significant difference in PaCO2 between the SHAM and VAG groups (P>0.05), and the VAG group had a high VT, peak pressure (Ppeak), and mean pressure (Pm) compared with the SHAM group 1, 2, 3 hours after ventilation (P<0.05). Compared to the SHAM group, dead space fraction (VD/VT) and respiratory system elastance (Ers) in the VAG group increased (P<0.05) and static pulmonary compliance (Cst) decreased markedly (P<0.05) after ventilation for 3 hours. Lung wet/dry weight ratio (W/D) (8.4±1.2 vs. 6.6±1.0), lung injury score (6.3±1.8 vs. 3.8±1.3), tumor necrosis factor-α (TNF-α) (779±372 pg/mL vs. 355±130 pg/mL) and interleukin-8 (IL-8) (169±21 pg/mL vs. 118±17 pg/mL) increased significantly in the VAG group compared with the SHAM group (P<0.05). Lung injury is aggravated after bilateral vagotomy, demonstrating that pulmonary stretch reflex may have protective effect on the lung.

Effectiveness Of End-tidal Carbon Dioxide Clamping In The Heat Stressed Human

During moderate to pronounced passive heat stress end-tidal carbon dioxide tension (PETCO2) is reduced by approximately 3 - 8 mmHg, which in part contributes to the decreases in cerebral blood flow and cerebrovascular conductance that occur in this thermal condition. Clamping devices have been used to manipulate PETCO2 in normothermic humans, however, their effectiveness in clamping arterial carbon dioxide tension (PaCO2) while heat stressed is unknown. PURPOSE: The aim of this study was to test the hypothesis that in the heat stressed human PETCO2 accurately tracks PaCO2 when PETCO2 is clamped at normothermic levels. METHODS: Internal temperature (telemetry pill), PaCO2 (radial artery catheter), and PETCO2 (capnograph) were assessed in 7 healthy individuals during three conditions performed sequentially; 1) normothermia (NT), 2) passive heat stress (HS), and 3) passive heat stress when PETCO2 was clamped at normothermic levels (HS+Clamp). Clamping was achieved using a computer controlled sequential gas delivery breathing circuit (RespiractTM). RESULTS: Heat stress increased internal temperature from 37.0 ± 0.3 to 38.4 ± 0.4 °C (P < 0.001). While normothermic values of PaCO2 (40.4 ± 3.4 mmHg) and PETCO2 (38.8 ± 3.5 mmHg; P = 0.12) were similar, HS resulted in significantly greater reductions in PaCO2 (D 10.1 ± 3.0 mmHg) relative to PETCO2 (D 7.8 ± 3.5 mmHg; P = 0.04). HS+Clamp caused comparable increases in PaCO2 (D 6.6 ± 3.4 mmHg) and PETCO2 (D 7.5 ± 2.8 mmHg: P = 0.30), however, because the decrease in PaCO2 due to HS was greater than PETCO2, absolute PaCO2 during HS+Clamp remained significantly lower (PaCO2: 36.8 ± 4.9 mmHg; PETCO2: 38.5 ± 5.2 mmHg; P < 0.01). CONCLUSION: These results indicate that despite a difference in absolute PETCO2 and PaCO2 during heat stress+clamp conditions, clamping caused similar increases between PETCO2 and PaCO2. Supported by NIH Grants HL61388 & HL84072

Both Extremes of Arterial Carbon Dioxide Pressure and the Magnitude of Fluctuations in Arterial Carbon Dioxide Pressure Are Associated With Severe Intraventricular Hemorrhage in Preterm Infants

The goal was to test the hypothesis that extremes of PaCO2 during the first 4 days after birth are associated with severe intraventricular hemorrhage (grades 3 and 4). A single-center retrospective review of clinical and blood gas data in the first 4 postnatal days for 849 infants with birth weights of 401 to 1250 g was performed. The univariate and multivariate relationships of severe intraventricular hemorrhage with maximal and minimal PaCO2, PaCO2 averaged over time (time-weighted PaCO2), and measures of PaCO2 fluctuation (SD of PaCO2 and difference in PaCO2 [maximum minus minimum]) were assessed. Birth weight (mean +/- SD) was 848 +/- 212 g, and the median gestational age was 26 weeks. Infants with severe intraventricular hemorrhage had higher maximal PaCO2 (median: 72 vs 59 mm Hg) and time-weighted PaCO2 (mean: 49 vs 47 mm Hg) values but lower minimal PaCO2 values (32 vs 37 mm Hg). High PaCO2, low PaCO2, SD of PaCO2, and difference in PaCO2 predicted severe intraventricular hemorrhage, but time-weighted average PaCO2 was not as predictive. Both extremes and fluctuations of PaCO2 are associated with severe intraventricular hemorrhage. It may be prudent to avoid extreme hypocapnia and hypercapnia during the period of risk for intraventricular hemorrhage.

Prevention of acute mountain sickness by acetazolamide: as yet an unfinished story

since the 1970s, over 200 studies with acetazolamide have shown it safe and 60–80% effective in acute mountain sickness (AMS). Despite much investigation, our understanding of its action in AMS remains incomplete and more complicated than generally taught. This should come as no surprise