Arterial Blood Gas Tensions Research Articles

Highlights of recent clinically relevant papers

Equine Veterinary EducationVolume 35, Issue 7 p. 338-339 RESEARCH HIGHLIGHTS Highlights of recent clinically relevant papers Sue Wright, Corresponding Author Sue Wright [email protected] orcid.org/0000-0002-5513-8571 EVE Editorial Office Email: [email protected]Search for more papers by this author Sue Wright, Corresponding Author Sue Wright [email protected] orcid.org/0000-0002-5513-8571 EVE Editorial Office Email: [email protected]Search for more papers by this author First published: 01 June 2023 https://doi.org/10.1111/eve.13809Read the full textAboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Cameron-Whytock, H.A., Parkin, T.D.H., Hobbs, S.J., Brigden, C.V. & Bennet, E.D. (2023) Towards a safer sport: risk factors for cross-country horse falls at British Eventing competition. Equine Veterinary Journal, Epub ahead of print. Available from: https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.13934 Fisher, K., Dodam, J., Bailey, J., Thombs, L., Hodgson, D. & Bukoski, A. (2023) Arterial blood gas tensions during recovery in horses anesthetized with apneustic anesthesia ventilation compared with conventional mechanical ventilation. Journal of Veterinary Anaesthesia Analgesia, Epub ahead of print. Available from: https://doi.org/10.1016/j.vaa.2023.01.004 Goldkuhl, J.E.C., Zablotski, Y., Sill, V., Jahn, W., Lorenz, I., Brunk, J. et al. (2023) Evaluation of cartilage injury in horses with osteochondral fragments in the metacarpo−/metatarsophalangeal joint: a study on 823 arthroscopies. Equine Veterinary Journal, Epub ahead of print. Available from: https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.13937 Goni, J.I., Hendrix, K. & Kritchevsky, J. (2023) Recovery of salmonella bacterial isolates from pooled fecal samples from horses. Journal of Veterinary Internal Medicine., 37(1), 323– 327. Available from: https://doi.org/10.1111/jvim.16586 Terschuur, J.A., Coomer, R.P.C., Handel, I., Pressanto, M.C. & McKane, S.A. (2023) Benefits of cyanoacrylate mesh closure following exploratory laparotomy in horses. Veterinary Record, Epub ahead of print. Available from: https://doi.org/10.1002/vetr.2732 Volume35, Issue7July 2023Pages 338-339 ReferencesRelatedInformation

A view from the floor of the pharmacy: The experience of a severe asthma attack

A view from the floor of the pharmacy: The experience of a severe asthma attack

Arterial blood gas tensions during recovery in horses anesthetized with apneustic anesthesia ventilation compared with conventional mechanical ventilation

ObjectiveTo compare PaO2 and PaCO2 in horses recovering from general anesthesia maintained with either apneustic anesthesia ventilation (AAV) or conventional mechanical ventilation (CMV). Study designRandomized, crossover design. AnimalsA total of 10 healthy adult horses from a university-owned herd. MethodsDorsally recumbent horses were anesthetized with isoflurane in oxygen [inspired oxygen fraction = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)] and ventilated with AAV or CMV according to predefined criteria [10 mL kg–1 tidal volume, PaCO2 40–45 mmHg (5.3–6.0 kPa) during CMV and < 60 mmHg (8.0 kPa) during AAV]. Horses were weaned from ventilation using a predefined protocol and transferred to a stall for unassisted recovery. Arterial blood samples were collected and analyzed at predefined time points. Tracheal oxygen insufflation at 15 L minute–1 was provided if PaO2 < 60 mmHg (8.0 kPa) on any analysis. Time to oxygen insufflation, first movement, sternal recumbency and standing were recorded. Data were analyzed using repeated measures anova, paired t tests and Fisher’s exact test with significance defined as p < 0.05. ResultsData from 10 horses were analyzed. Between modes, PaO2 was significantly higher immediately after weaning from ventilation and lower at sternal recumbency for AAV than for CMV. No PaCO2 differences were noted between ventilation modes. All horses ventilated with CMV required supplemental oxygen, whereas three horses ventilated with AAV did not. Time to first movement was shorter with AAV. Time to oxygen insufflation was not different between ventilation modes. ConclusionsAlthough horses ventilated with AAV entered the recovery period with higher PaO2, this advantage was not sustained during recovery. Whereas fewer horses required supplemental oxygen after AAV, the use of AAV does not preclude the need for routine supplemental oxygen administration in horses recovering from general anesthesia.

Arterial blood gas tensions - Effect of storage time and temperature

Introduction: Arterial and venous blood gas analysis provide vital information on pH, oxygenation, ventilatory and acid-base status that guide clinician interventions. Factors such as syringe material, sampling technique, type of anticoagulant, storage time and temperature, and analysis may influence the accuracy of results. Aim: To determine the effect of storage time and temperature on blood gas analysis. Method: Nine 1-ml samples of arterial blood were collected by convenient sampling method involving 25 subjects in a single attempt from an in-dwelling arterial line. Four samples were stored in separate ice bags and four at room temperature. One sample was analysed immediately (‘reference’). One sample from each storage group was analysed at 15-min intervals for 60-min. The agreement of the ‘ureference’ value with values of samples taken at 15-, 30-, 45- and 60-min were determined using Lin’s concordance correlation and Bland and Altman’s 95% limits of agreement (LOA). Results: The rate of decay of pH and PaCO2 values over time were similar for samples stored at room temperature and ice. The average difference (95% LOA) in PaO2 on samples stored at room temperature at 15, 30, 45 and 60 min when compared with baseline were 1.80 (-18 to 21.7), 3.84 (-20.5 to 28.2), 3.40 (-18.8 to 25.6) and 4.36 (-17.5 to 26.2) respectively. The decay in PaO2 was less pronounced in samples stored in ice with differences of -2.04 (-18.3 to 14.2), -2.64 (-14.2 to 9.0), -3.08 (-20.0 to 13.5) and -2.40 (-12.2 to 7.4) at 15, 30, 45 and 60 min respectively. Conclusion: PaO2 values reduce with time. The changes are more pronounced when samples are stored in room temperature than in ice. The wide LOA would imply that blood gas samples should, as far as possible, be processed immediately.

Optimal Arterial Blood Gas Tensions for the Prognosis of Favorable Neurological Outcomes in Survivors after Extracorporeal Cardiopulmonary Resuscitation.

Our aim is to assess the optimal levels of oxygen and carbon dioxide for the prognosis of favorable neurologic outcomes in survivors after extracorporeal cardiopulmonary resuscitation (ECPR). We obtained the mean levels of PaCO2 and PaO2 in arterial blood gas samples 72 h after ECPR. The primary outcome was the neurological status, according to the Cerebral Performance Categories (CPC) scale, upon discharge. Of 119 (48.6%) survivors, 95 (38.8%) had favorable neurologic outcomes (CPC 1 or 2). There was a U-shaped relationship between mean arterial blood gas tensions and poor neurological outcomes. The risk of poor neurological outcome was lowest in patients with the second tertile of mean PaCO2 (30–42 mm Hg) and PaO2 (120–160 mm Hg). In a multivariable analysis, third tertile of mean PaCO2, third tertile of mean PaO2, age, shockable rhythm, out of hospital cardiac arrest, duration of cardiopulmonary resuscitation, and ECPR at cardiac catheterization lab were found to be significantly associated with poor neurologic outcomes. Additionally, hypercapnia and extreme hyperoxia were found to be significantly associated with poor neurological outcomes after ECPR. Therefore, maintaining adequate arterial levels of oxygen and carbon dioxide may be important for favorable neurological prognoses in survivors after ECPR.

Measurement of maximal respiratory static pressure in stable COPD patients and their co-rrelation with various physiological anthropometric and spirometry parpmeters and arterial blood gas tension

The strength of respiratory muscles can be evaluated from static measurement (PImax and PEmax) or inferred from dynamic measurement such as maximal voluntary ventilation. Maximal inspiratory pressure and Maximal expiratory pressure are simple, convenient and non-invasive measurement of respiratory muscle strength. Respiratory muscle strength decreases in COPD patients due to multiple factors. The primary aim of this study is to obtain mean PImax and PEmax values in Indian COPD patients and its co-rrelation with anthropomatric, physiological, spirometric parameters and arterial blood gas tension.

Antenatal sildenafil treatment improves neonatal pulmonary hemodynamics and gas exchange in lambs with diaphragmatic hernia.

Infants with congenital diaphragmatic hernia (CDH) are predisposed to pulmonary hypertension after birth, owing to lung hypoplasia that impairs fetal pulmonary vascular development. Antenatal sildenafil treatment attenuates abnormal pulmonary vascular and alveolar development in rabbit and rodent CDH models, but whether this translates to functional improvements after birth remains unknown. We aimed to evaluate the effect of antenatal sildenafil on neonatal pulmonary hemodynamics and lung function in lambs with diaphragmatic hernia (DH). DH was surgically induced at approximately 80 days' gestation in 16 lamb fetuses (term in lambs is approximately 147 days). From 105 days' gestation, ewes received either sildenafil (0.21 mg/kg/h intravenously) or saline infusion until delivery (n = 8 fetuses in each group). At approximately 138 days' gestation, all lambs were instrumented and then delivered via Cesarean section. The lambs were ventilated for 120 min with continuous recording of physiological (pulmonary and carotid artery blood flow and pressure; cerebral oxygenation) and ventilatory parameters, and regular assessment of arterial blood gas tensions. Only lambs that survived until delivery and with a confirmed diaphragmatic defect at postmortem examination were included in the analysis; these comprised six DH-sildenafil lambs and six DH-saline control lambs. Lung-to-body-weight ratio (0.016 ± 0.001 vs 0.013 ± 0.001; P = 0.06) and dynamic lung compliance (0.8 ± 0.2 vs 0.7 ± 0.2 mL/cmH2 O; P = 0.72) were similar in DH-sildenafil lambs and controls. Pulmonary vascular resistance decreased following lung aeration to a greater degree in DH-sildenafil lambs, and was 4-fold lower by 120 min after cord clamping than in controls (0.6 ± 0.1 vs 2.2 ± 0.6 mmHg/(mL/min); P = 0.002). Pulmonary arterial pressure was also lower (46 ± 2 vs 59 ± 2 mmHg; P = 0.048) and pulmonary blood flow higher (25 ± 3 vs 8 ± 2 mL/min/kg; P = 0.02) in DH-sildenafil than in DH-saline lambs at 120 min. Throughout the 120-min ventilation period, the partial pressure of arterial carbon dioxide tended to be lower in DH-sildenafil lambs than in controls (63 ± 8 vs 87 ± 8 mmHg; P = 0.057), and there was no significant difference in partial pressure of arterial oxygen between the two groups. Sustained maternal antenatal sildenafil infusion reduced pulmonary arterial pressure and increased pulmonary blood flow in DH lambs for the first 120 min after birth. These findings of improved pulmonary vascular function are consistent with improved pulmonary vascular structure seen in two previous animal models. The data support the rationale for a clinical trial investigating the effect of antenatal sildenafil in reducing the risk of neonatal pulmonary hypertension in infants with CDH. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Fourth generation e-cigarette vaping induces transient lung inflammation and gas exchange disturbances: results from two randomized clinical trials.

When heated by an electronic cigarette, propylene glycol and glycerol produce a nicotine-carrying-aerosol. This hygroscopic/hyperosmolar aerosol can deposit deep within the lung. Whether these deposits trigger local inflammation and disturb pulmonary gas exchanges is not known. The aim of this study was to assess the acute effects of high-wattage electronic cigarette vaping with or without nicotine on lung inflammation biomarkers, transcutaneous gas tensions, and pulmonary function tests in young and healthy tobacco smokers. Acute effects of vaping without nicotine on arterial blood gas tensions were also assessed in heavy smokers suspected of coronary artery disease. Using a single-blind within-subjects study design, 25 young tobacco smokers underwent three experimental sessions in random order: sham-vaping and vaping with and without nicotine at 60 W. Twenty heavy smokers were also exposed to sham-vaping (n = 10) or vaping without nicotine (n = 10) in an open-label, randomized parallel study. In the young tobacco smokers, compared with sham-vaping: 1) serum club cell protein-16 increased after vaping without nicotine (mean ± SE, −0.5 ± 0.2 vs. +1.1 ± 0.3 µg/l, P = 0.013) and vaping with nicotine (+1.2 ± 0.3 µg/l, P = 0.009); 2) transcutaneous oxygen tension decreased for 60 min after vaping without nicotine (nadir, −0.3 ± 1 vs. −15.3 ± 2.3 mmHg, P < 0.001) and for 80-min after vaping with nicotine (nadir, −19.6 ± 2.8 mmHg, P < 0.001). Compared with sham vaping, vaping without nicotine decreased arterial oxygen tension for 5 min in heavy-smoking patients (+5.4 ± 3.3 vs. −5.4 ± 1.9 mmHg, P = 0.012). Acute vaping of propylene glycol/glycerol aerosol at high wattage with or without nicotine induces airway epithelial injury and sustained decrement in transcutaneous oxygen tension in young tobacco smokers. Intense vaping conditions also transiently impair arterial oxygen tension in heavy smokers.

Effect of Liuzijue Qigong on patients with chronic obstructive pulmonary disease: Protocol for a systematic review and meta-analysis.

Background:Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide with a substantial and increasing social and economic burden. Liuzijue Qigong is a kind of traditional Chinese Qigong exercises that Traditional Chinese Medicine practitioners prescribe to individuals with COPD to strengthen the internal organs’ function. Liuzijue Qigong was recommended for use in COPD rehabilitation, and some clinical trials indicate that Liuzijue Qigong would produce better functional capacity and quality of life of individuals with COPD. The objective of this study is to conduct a systematic review of the existing studies to assess effectiveness and safety of Liuzijue Qigong for the prevention or treatment of COPD in patients.Methods:We will perform the comprehensive literature search in English and Chinese electronic database. The publication period will be from inception to the search date. In addition, the clinical trial registries, dissertations, informal publication, grey literature, reference lists of studies, systematic reviews, and conference abstracts will also be collected. Two reviewers will identify relevant studies, extract data information, and then assess the methodical quality by the Cochrane risk of bias assessment tool. Only randomized controlled trials comparing Liuzijue Qigong against other intervention or nonintervention will be included. Data will be synthesized by either fixed-effect or random-effect model regarding to a heterogeneity test. The routine lung function, arterial blood gas tensions, partial pressure of carbon dioxide, functional capacity, 30 seconds sit-to-stand test, respiratory function, maximal inspiration pressure, maximal expiratory pressure, airway resistance, and specific airway conductance will be assessed as primary outcomes. The secondary outcomes involved dyspnea, and fatigue levels, respiratory muscle strength, upper and lower limb muscle strength, handgrip strength test, and health-related quality of life and safety. Meta-analysis will be performed by using Cochrane's Review Manager software (version 5.3.5).Results:This systematic review and meta-analysis will provide a high-quality synthesis and evaluate the efficacy and safety based on current relevant literature evidence of Liuzijue Qigong intervention for COPD patient.Conclusion:Our systematic review will provide evidence to determine whether Liuzijue Qigong is an effective and safe approach to prevention and treatment of COPD patients.

Afferent neural feedback overrides the modulating effects of arousal, hypercapnia and hypoxaemia on neonatal cardiorespiratory control.

Evidence obtained at whole animal, organ-system, and cellular and molecular levels suggests that afferent volume feedback is critical for the establishment of adequate ventilation at birth. As a result of the irreversible nature of the vagal ablation studies performed to date, it was difficult to quantify the roles of afferent volume input, arousal and changes in blood gas tensions on neonatal respiratory control. During reversible perineural vagal block, profound apnoeas and hypoxaemia and hypercarbia were observed, necessitating the termination of perineural blockade. Respiratory depression and apnoeas were independent of sleep state. We demonstrate that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. A change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period. Afferent volume feedback plays a vital role in neonatal respiratory control. Mechanisms for the profound respiratory depression and life-threatening apnoeas observed in vagally denervated neonatal animals remain unclear. We investigated the roles of sleep states, hypoxic-hypercapnia and afferent volume feedback on respiratory depression using reversible perineural vagal block during the early postnatal period. Seven lambs were instrumented during the first 48h of life to record/analyse sleep states, diaphragmatic electromyograph, arterial blood gas tensions, systemic arterial blood pressure and rectal temperature. Perineural cuffs were placed around the vagi to attain reversible blockade. Postoperatively, during the awake state, both vagi were blocked using 2% xylocaine for up to 30min. Compared to baseline values, pHa , and decreased and increased during perineural blockade (P<0.05). Four of seven animals exhibited apnoeas of ≥20s requiring the immediate termination of perineural blockade. Breathing rates decreased from the baseline value of 53±12 to 24±20breathsmin-1 during blockade despite an increased (P<0.001). Following blockade, breathing patterns returned to baseline values despite marked hypocapnia ( 33±3torr; P=0.03). Respiratory depression and apnoeas were independent of sleep states. The present study provides the much needed physiological evidence indicating that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. Rather, a change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period.

Opioid-type Respiratory Depressant Side Effects of Cebranopadol in Rats Are Limited by Its Nociceptin/Orphanin FQ Peptide Receptor Agonist Activity.

Cebranopadol is a first-in-class analgesic with agonist activity at classic opioid peptide receptors and the nociceptin/orphanin FQ peptide receptor. The authors compared the antinociceptive and respiratory depressant effects of cebranopadol and the classic opioid fentanyl and used selective antagonists to provide the first mechanistic evidence of the contributions of the nociceptin/orphanin FQ peptide and μ-opioid peptide receptors to cebranopadol's respiratory side-effect profile. Antinociception was assessed in male Sprague-Dawley rats using the low-intensity tail-flick model (n = 10 per group). Arterial blood gas tensions (PaCO2 and PaO2) were measured over time in samples from unrestrained, conscious rats after intravenous administration of cebranopadol or fentanyl (n = 6 per group). The ED50 for peak antinociceptive effect in the tail-flick model was 7.4 μg/kg for cebranopadol (95% CI, 6.6 to 8.2 μg/kg) and 10.7 μg/kg for fentanyl citrate (9 to 12.7 μg/kg). Fentanyl citrate increased PaCO2 levels to 45 mmHg (upper limit of normal range) at 17.6 μg/kg (95% CI, 7.6 to 40.8 μg/kg) and to greater than 50 mmHg at doses producing maximal antinociception. In contrast, with cebranopadol, PaCO2 levels remained less than 35 mmHg up to doses producing maximal antinociception. The nociceptin/orphanin FQ peptide receptor antagonist J-113397 potentiated the respiratory depressant effects of cebranopadol; these changes in PaCO2 and PaO2 were fully reversible with the μ-opioid peptide receptor antagonist naloxone. The therapeutic window between antinociception and respiratory depression in rats is larger for cebranopadol than that for fentanyl because the nociceptin/orphanin FQ peptide receptor agonist action of cebranopadol counteracts side effects resulting from its μ-opioid peptide receptor agonist action.

50 Years Ago in TheJournal ofPediatrics: Arterial Blood Gas Tensions and Acid-Base Balance in the Management of Respiratory Distress Syndrome

50 Years Ago in TheJournal ofPediatrics: Arterial Blood Gas Tensions and Acid-Base Balance in the Management of Respiratory Distress Syndrome

EFFECTS OF WEIGHT LOSS AFTER BARIATRIC SURGERY ON PULMONARY FUNCTION TESTS AND OBSTRUCTIVE SLEEP APNEA IN MORBIDLY OBESE WOMEN

obesity impacts on respiratory function and also it acts as a risk factor for obstructive sleep apnea (OSA). to study the effects of bariatric surgery on pulmonary function tests and on OSA in morbidly obese women over 4 years. fifteen morbidly obese women (mean body mass index [BMI] 50.52 ± 12.71 kg.m-2, mean age 40.13 ± 10.06 years) underwent pulmonary function tests (PFT) in two opportunities (before and after weight loss surgery). PFT included spirometry, body plethysmography and measure of maximal inspiratory mouth pressure (PImax) and of tension-time index for inspiratory muscles. Also, in both opportunities, resting arterial blood gas tensions were evaluated and a full night sleep register was performed. BMI significantly decreased after bariatric surgery (-44.07 kg.m-2 [CI 95% -38.32 - -49.81]). Also, there was a significantly increase in forced expiratory volume in 1 second (FEV1) (p < 0.01), forced vital capacity (FVC) (p < 0.01), expiratory reserve volume (ERV) (p = 0.040), functional residual capacity (FRC) (p = 0.009) and a decline in airways resistance (Raw) (p = 0.018). Concerning sleep registers, apnea hypopnea index (p = 0.001) and desaturation index (p = 0.001) were also reduced after weight loss. Improve in ERV had a significant correlation with weight loss (r = 0.774, p = 0.024). Conclussions: pulmonary function tests and apnea hypopnea index improve after bariatric surgery in mor bidly obese women. Improvement of ERV is well correlated with weight loss.

Exposure to 100% Oxygen Abolishes the Impairment of Fracture Healing after Thoracic Trauma.

In polytrauma patients a thoracic trauma is one of the most critical injuries and an important trigger of post-traumatic inflammation. About 50% of patients with thoracic trauma are additionally affected by bone fractures. The risk for fracture malunion is considerably increased in such patients, the pathomechanisms being poorly understood. Thoracic trauma causes regional alveolar hypoxia and, subsequently, hypoxemia, which in turn triggers local and systemic inflammation. Therefore, we aimed to unravel the role of oxygen in impaired bone regeneration after thoracic trauma. We hypothesized that short-term breathing of 100% oxygen in the early post-traumatic phase ameliorates inflammation and improves bone regeneration. Mice underwent a femur osteotomy alone or combined with blunt chest trauma 100% oxygen was administered immediately after trauma for two separate 3 hour intervals. Arterial blood gas tensions, microcirculatory perfusion and oxygenation were assessed at 3, 9 and 24 hours after injury. Inflammatory cytokines and markers of oxidative/nitrosative stress were measured in plasma, lung and fracture hematoma. Bone healing was assessed on day 7, 14 and 21. Thoracic trauma induced pulmonary and systemic inflammation and impaired bone healing. Short-term exposure to 100% oxygen in the acute post-traumatic phase significantly attenuated systemic and local inflammatory responses and improved fracture healing without provoking toxic side effects, suggesting that hyperoxia could induce anti-inflammatory and pro-regenerative effects after severe injury. These results suggest that breathing of 100% oxygen in the acute post-traumatic phase might reduce the risk of poorly healing fractures in severely injured patients.

Functional capacity, physical activity, and quality of life in hypoxemic patients with chronic obstructive pulmonary disease.

BackgroundThe risk of hypoxemia increases with the progression of chronic obstructive pulmonary disease (COPD) and the deterioration of pulmonary function. The aim of this study was to compare functional capacity, physical activity, and quality of life in hypoxemic and non-hypoxemic patients with COPD.MethodsThirty-nine COPD patients (mean age: 62.0±7.03 years) were included in this study. Arterial blood gas tensions were measured, and patients were divided into two groups according to oxygen partial pressure (PaO2), the hypoxemic COPD (PaO2 <60 mmHg) (n=18), and the control (PaO2 ≥60 mmHg) (n=21) groups. Functional exercise capacity was evaluated using the 6-minute walk test (6MWT). Oxygen saturation, dyspnea, and fatigue perception were measured before and after the 6MWT. Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ) and an accelerometer. Quality of life was assessed using the St George’s Respiratory Questionnaire (SGRQ).ResultsThe number of emergency visits and hospitalizations were higher in hypoxemic patients (P<0.05). Lung function parameters, 6MWT distance, exercise oxygen saturation, IPAQ total score, and energy expenditure during daily life were significantly lower, but percentage of maximum heart rate reached during the 6MWT was significantly higher, in hypoxemic COPD patients than in controls (P<0.05).ConclusionHypoxemia has a profound effect on functional capacity and physical activity in patients with COPD.

Association between early arterial blood gas tensions and neurological outcome in adult patients following in-hospital cardiac arrest

ObjectiveThe early partial pressures of arterial O2 (PaO2) and CO2 (PaCO2) have been found in animal studies to be correlated with neurological outcome after brain injury. However, the relationship of early PaO2 and PaCO2 to the neurological outcomes of resuscitated patients after cardiac arrest was still not clear. MethodsThis was a retrospective observational cohort study in a single medical center. Adult patients who had in-hospital cardiac arrest between 2006 and 2012 and achieved sustained return of spontaneous circulation (ROSC) (ROSC>20min without resumption of chest compression) were included. Multivariable logistic regression analysis was used to identify factors associated with favorable neurological outcome at hospital discharge. The first PaO2 and PaCO2 values measured after first sustained ROSC were used for analysis. ResultsOf the 550 included patients, 154 (28%) survived to hospital discharge and 74 (13.5%) achieved favorable neurological outcome. The mean time from sustained ROSC to the measurement of PaO2 and PaCO2 was 136.8min. The mean PaO2 and PaCO2 were 167.4mmHg and 40.3mmHg, respectively. PaO2 between 70 and 240mmHg (odds ratio [OR] 1.96, 95% confidence interval [CI] 1.08–3.64) and PaCO2 levels (OR 0.98, 95% CI 0.95–0.99) were positively and inversely associated with favorable neurological outcome, respectively. ConclusionsThe early PaO2 and PaCO2 levels obtained after ROSC might be correlated with neurological outcome of patients with in-hospital cardiac arrest. However, because of the inherent limitations of the retrospective design, these results should be further validated in future studies.

Impaired alveolar-arterial oxygen transfer is associated with reduced milk yield in primiparous post-partum dairy heifers at moderate altitude.

Domestic cattle have limited cardiopulmonary reserve for their body size and oxygen requirements. Therefore, it is plausible that impaired alveolar-arterial gas exchange may be detrimental to energetically expensive traits such as milk production which, like all aerobic processes, requires oxygen. The degree of alveolar-arterial oxygen transfer impairment can be determined by estimating the alveolar-arterial oxygen (A-a O2) pressure gradient from arterial blood-gas tensions. The degree of oxygen transfer impairment is proportional to the A-a O2 pressure gradient: the higher the A-a O2 pressure gradient the less oxygen is transferred to the blood for a given ventilation rate. In this study two cohorts of Holstein-Friesian heifers were followed on one northern Colorado dairy farm. Arterial blood-gas analyses were performed up to 9d post-calving. Heifers were grouped into quartiles based on A-a O2 pressure gradient so that relative comparisons could be made. Heifers in the lowest (Q1) and highest (Q4) quartile had the least and greatest impairment of alveolar-arterial oxygen transfer, respectively. We hypothesised that milk yield over 60d would be greatest for heifers in Q1 and would decrease with quartile increments. Hyperventilation, as indicated by hypocapnia, was notable. Despite hypoxia, haematocrit was low. Alveolar-arterial O2 pressure gradient was associated with milk production (P=0·03) when controlling for cohort, treatment for disease and calving difficulty score. Heifers in Q1 produced 1992 kg (95% CI=1858, 2127kg) of milk when controlling for all other variables. Relative to heifers in Q1, heifers in Q2, Q3 and Q4 produced 130kg (95% CI=313, -52kg; P=0·45), 285kg (95% CI=474, 96kg; P=0·004) and 169kg (95% CI=395, -57kg; P=0.14) less milk, respectively. In conclusion, efficacy of alveolar-arterial oxygen transfer was associated with milk yield in dairy heifers on one farm at moderate altitude.

G.P.65: Obstructive sleep apnoea and subclinical impairment of respiratory function are common in sporadic inclusion body myositis

To examine the occurrence of respiratory dysfunction in sporadic inclusion body myositis (IBM) and its relationship to peripheral muscle strength and ventilation during sleep. Anthropometric, muscle strength, dyspnoea, daytime sleepiness and dysphagia data were collected. Spirometry, respiratory muscle strength and arterial blood gas tensions were measured. Ventilation during sleep was assessed by dual channel (oximetry, nasal pressure) home monitoring. Sixteen patients with biopsy-proven IBM were studied (10 males, 6 females; age 68.1±9.9years; disease duration 11.9±5.0years; body mass index 28.5±4.0kg/m²). Four patients reported excessive daytime sleepiness (Epworth Sleepiness Scale ⩾10); 8 had at least mild dysphagia (Dysphagia Outcome Severity Scale ⩽5); forced vital capacity was <80% of the predicted normal in 7; sniff nasal inspiratory pressure was reduced (<60cm H₂O) in 3; daytime hypoxemia (PaO₂<80mmHg) was present in 10 and hypercapnia (PaCO₂>45mmHg) in one. Sleep study was performed in 15 patients and revealed sleep hypoxemia (⩾2% of total sleep time at or below a saturation <90% (TST⩽90)) in 10 and obstructive sleep apnoea (respiratory disturbance index 23.4±12.8 (range 7–50.3) events/h) in all 15. Daytime PaO₂ was related to TST⩽90 (<i>r</i>=−0.55, <i>p</i>=0.04). Asymptomatic impairment of wakeful respiratory function was common and obstructive sleep apnoea was observed in all patients tested, irrespective of daytime respiratory function. This high occurrence probably reflects the combined effects of pharyngeal muscle weakness and sleep-related reduction in muscle activation and ventilatory drive. These findings suggest that tests of respiratory function, including an overnight sleep study, should be performed routinely in IBM patients, irrespective of peripheral muscle function or other non-respiratory disease severity parameters.

Sleep disordered breathing and subclinical impairment of respiratory function are common in sporadic inclusion body myositis

Relatively little is known about frequency and extent of respiratory problems in sporadic inclusion body myositis (IBM). To address this issue a study of peripheral muscle and respiratory function and related symptoms was performed in a cohort with biopsy-proven IBM. Dyspnoea, daytime sleepiness, dysphagia, spirometry, respiratory muscle strength, arterial blood gas tensions and ventilation during sleep were assessed. Sixteen patients were studied (10 males; age 68.1±9.9years; disease duration 11.9±5.0years; body mass index 28.5±4.0kg/m2). Four reported excessive daytime sleepiness; 8 had at least mild dysphagia; forced vital capacity was <80% predicted normal in 7; sniff nasal inspiratory pressure was reduced in 3; daytime hypoxemia was present in 9 and hypercapnia in one. Sleep study was performed in 15 and revealed sleep disordered breathing (apnoea–hypopnoea index 23.4±12.8 (range 7–50.3)events/h) in all. There were no consistent relationships between respiratory function impairment, occurrence of sleep disordered breathing, and severity of peripheral muscle weakness. Thus, asymptomatic impairment of respiratory function was common and sleep disordered breathing observed in all patients tested, irrespective of daytime respiratory function. This suggests respiratory function testing, including sleep study, should be performed routinely in IBM, irrespective of peripheral muscle function or other disease severity parameters.

The hidden consequences of ventilator management decisions.

In the following perspective, we will highlight seemingly remote, downstream consequences of common ventilator management decisions. For example, a change in PEEP may alter venous return, blood pressure, cardiac output, arterial and venous blood gas tensions, metabolic rate, respiratory sensations, breathing pattern, and the work of breathing. If providers consider any of these changes dangerous or maladaptive, they may initiate additional interventions in the form of vasoactive agents, intravenous fluids, and/or sedatives, all of which have their own risk/benefit profile. The approach to such co-interventions is rarely addressed even in well-designed large clinical trials. Therefore, it is often impossible to infer intervention-specific mechanisms of action and/or identify the phenotype of responders and nonresponders in such trials. On the flip side, in preclinical research intended to uncover mechanisms, experimental animals are rarely treated the way a critically ill patient would be. For respiratory therapists, this knowledge gap stresses the imperative to think beyond the lungs and to communicate ventilator management decisions with all members of the healthcare team.