Detection of Chronic Hypoventilation Among Infants With Robin Sequence Using Capillary Blood Gas Sampling.

OBJECTIVES/HYPOTHESIS: To describe the use of capillary blood gas (CBG) sampling to detect and quantify hypoventilation in infants with Robin sequence (RS). METHODS: Case series with chart review at two institutions. Infants with RS presenting over a 10-year period were identified using departmental databases. CBG values obtained during infancy or until airway intervention (AI) were reviewed. RESULTS: From 2008 to 2018, 111 infants with RS were identified as having had been assessed and managed from birth or transfer until discharge home and having CBG data available. In most cases, CBG sampling was obtained every other day until intervention or discharge. A total of 81 (73%) infants required AI: 72 (89%) underwent mandibular distraction osteogenesis, five (6%) underwent tracheotomy, and four (5%) were discharged home with a nasopharyngeal airway. The mean PCO2 at day of life (DOL) 7-30 for the AI group was 52.7 mmHg (95% confidence interval: 51.7-53.7) and for the no AI group was 45.9 mmHg (44.8-47.0; P < .0001). The mean HCO3 at DOL 7-30 for the AI group was 29.8 mEq/L (29.4-30.1) and for the no AI group was 27.0 mEq/L (26.5-27.4; P < .0001). Receiver operating characteristic curves were created for maximum PCO2 and HCO3 values and cutoffs were established by optimizing a balance of sensitivity and specificity. Infants requiring AI surpassed the PCO2 and HCO3 cutoff at a median of DOL 9. CONCLUSIONS: Among infants with RS and hypoventilation, objective measures of respiratory acidosis may be apparent by DOL 9. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:2789-2794, 2021.

High flow nasal cannula in acute hypercapnic exacerbation of chronic obstructive pulmonary disease: an emerging utility.

High flow nasal cannula (HFNC) provides warmed and humidified air with flow rates up to 60 liters/min with relatively fixed oxygen content (FiO2). It has been extensively evaluated for hypoxemic respiratory failure and has been used in mild acute respiratory distress syndrome, pre-intubation, bronchoscopy and pediatric obstructive sleep apnea. Recent data has suggested a role in stable hypercapnic chronic obstructive pulmonary disease (COPD) and even in acute exacerbations, though, the use has not been advocated by any guidelines yet. We present a case of acute hypercapnic exacerbation of COPD, intolerant to non-invasive ventilation, showing response and improvement on use of HFNC. This case highlights this potential mechanisms and prospects for the same.

Alkali Therapy for Respiratory Acidosis: A Medical Controversy.

Alkali therapy for certain organic acidoses remains a topic of ongoing controversy, but little attention has been given to a related medical controversy, namely the prescription of alkali for respiratory acidosis. We first describe the determinants of carbon dioxide retention in the 2 types of respiratory failure; hypercapnic respiratory failure and hypoxemic respiratory failure with coexisting hypercapnia. We then highlight the deleterious consequences of severe acidemia for several organ systems, particularly the cardiovascular and central nervous systems. We argue that alkali therapy is not indicated for respiratory acidosis as a simple acid-base disturbance. Notwithstanding, we recommend prescription of alkali for severe acidemia caused by mixed acidosis (ie, combined respiratory and metabolic acidosis) or permissive hypercapnia. We examine the utility of alkali therapy in various clinical scenarios incorporating respiratory acidosis. We conclude that controlled studies will be required to test the impact of alkali therapy on clinical outcomes of these clinical settings. Such studies should also examine the optimal mode of administering alkali (amount, rate, and tonicity) and the blood pH to be targeted. The development of new buffers should be explored, especially systems that do not generate carbon dioxide or even consume it.

Effects of Vasoactive Medications and Maternal Positioning During Cesarean Delivery on Maternal Hemodynamics and Neonatal Acid-Base Status.

Maternal hemodynamics, positioning, and anesthesia technique for cesarean delivery influence neonatal acid-base balance; direct effects from drugs that cross the placenta also have an influence. Spinal anesthesia limits fetal exposure to depressant drugs and avoids maternal airway instrumentation, but is associated with hypotension. Hypotension may be prevented/treated with vasopressors and intravenous fluids. Current evidence supports phenylephrine as the first-line vasopressor. Fifteen degrees of lateral tilt during cesarean delivery has been advocated to relieve vena caval obstruction, but routine use may be unnecessary in healthy nonobese women having elective cesarean delivery if maternal blood pressure is maintained near baseline.

Neuroapoptosis in newborns with respiratory acidosis at birth.

BACKGROUND: S100B protein is one of the most accurate biomarkers for diagnosis of neuroapoptosis and brain damage. The aim was to evaluate the lactate concentration and acid-base balance (pH, pCO2, pO2, HCO3c and BEb) in umbilical cord blood to predict high risk of neuroapoptosis and analyze the relationship between the levels of these biomarkers and umbilical cord blood S100B protein concentration at birth. METHODS: Apparently healthy newborns were included. S100B protein and blood gas test (lactate and acid-base balance) were determined in umbilical cord blood at birth. Newborns were classified into two groups: with and without high risk of neuroapoptosis. Newborns with high umbilical cord blood S100B protein concentration were considered newborns at high risk of neuroapoptosis. RESULTS: Sixty-one newborns were included, 12 had high risk of neuroapoptosis and 49 did not. S100B protein concentration correlate directly with pCO2 levels (Rho: 0.286, p = .0321) and lactate concentration (Rho: 0.278, p = .0315); and indirectly with pH (Rho: -0.332, p = .01). The analysis of the ROC curves yielded significant curves for pH and pCO2 to predict high risk of neuroapoptosis, pH optimal cutoff value was 7.19 (sensitivity: 50%, specificity: 83.7%, AUC: 0.708); and pCO2 optimal cutoff value was 60 mmHg (sensitivity: 30%, specificity: 85.4%, AUC: 0.705). CONCLUSIONS: Respiratory acidosis is associated to high concentrations of S100B protein in umbilical cord blood at birth. Umbilical cord blood pH and pCO2 may be useful in differentiating newborns at high risk of neuroapoptosis. Umbilical cord blood gas test may be valuable as risk indicator for neuroapoptosis at birth.

Ischemic priapism as a model of exhausted metabolism.

In vivo metabolic studies typically concern complex open systems. However, a closed system allows better assessment of the metabolic limits. Ischemic priapism (IP) constitutes a special model of the compartment syndrome that allows direct sampling from a relatively large blood compartment formed by the corpora cavernosa (CC). The purpose of our study was to measure metabolic changes and the accumulation of end products within the CC during IP. Blood gas and biochemical analyses of aspirates of the CC were analyzed over an 8-year period. Mean ± SD pH, pCO2 , pO2 , O2 -saturation, lactate, and glucose of the aspirated blood were determined with a point-of-care analyzer. Forty-seven initial samples from 21 patients had a pH of 6.91 ± 0.16, pCO2 of 15.3 ± 4.4 kPa, pO2 of 2.4 ± 2.0 kPa, and an O2 -saturation of 19 ± 24% indicating severe hypoxia with severe combined respiratory and metabolic acidosis. Glucose and lactate levels were 1.1 ± 1.5 and 14.6 ± 4.8 mmol/L, respectively. pH and pCO2 were inversely correlated (R2  = 0.86; P < 0.001), glucose and O2 -saturation were positively correlated (R2  = 0.83; P < 0.001), and glucose and lactate were inversely correlated (R2  = 0.72; P < 0.001). The positive correlation of CO2 and lactate (R2  = 0.69; P < 0.001) was similar to that observed in vitro, when blood was titrated with lactic acid. The observed combined acidosis underscores that IP behaves as a closed system where severe hypoxia and glycopenia coexist, indicating that virtually all energy reserves have been consumed.

Inadequacy of Pulse Oximetry in the Catheterization Laboratory. An Exploratory Study Monitoring Respiratory Status Using Arterial Blood Gases during Cardiac Catheterization with Conscious Sedation.

BACKGROUND: Benzodiazepines and opioids are commonly used for conscious sedation (CS) in cardiac catheterization laboratory (CCL) patients. Both drugs are known to predispose to hypoxemia, apnea and decreased responsiveness to PCO2, resulting in decreased arterial pH and PO2, as well as increased PCO2. We want to determine the effects of CS on arterial blood gas (ABG) in CCL patient, and identify if pulse oximetry monitoring is adequate. METHODS: We enrolled 18 subjects undergoing elective catheterization. Measurement of ABGs at one-minute intervals was done from the moment of arterial access until case end. The results of ABGs were not available to the clinician who administered sedation. Relationships of pH, PCO2, PaO2 and SaO2 were studied by plotting time series graphs. Significant changes were defined as pH <7.30, SaO2 < 90, and PCO2 > 50 mmHg. RESULTS: No significant change in pH, PCO2, PaO2 and SaO2 was noted in 4/18 (22%) subjects. A significant drop in SaO2 was noted in 4/18 (22%). A significant change in PCO2 and/or pH was noted in 10/18 (55%) cases. Among the 16 (16/18) subjects receiving supplemental oxygen, 7 (7/18, 39%) had no drop in SaO2, but developed respiratory acidosis. At the end of the case, 5/18 (28%) subjects had respiratory acidosis with normal PaO2. CONCLUSION: Significant hypercarbia and acidosis occurred frequently in this small study during CS in patients undergoing cardiac catheterization. Relying on pulse oximetry alone especially with patients on supplemental oxygen may lead to failure in detecting respiratory acidosis in a significant number of patients.

Hyperacute Hemodynamic Effects of BiPAP Noninvasive Ventilation in Patients With Acute Heart Failure and Left Ventricular Systolic Dysfunction in Emergency Department.

BACKGROUND: Acute heart failure (AHF) is one of the leading causes of admission to emergency department (ED); severe hypoxemic AHF may be treated with noninvasive ventilation (NIV). Despite the demonstrated clinical efficacy of NIV in relieving symptoms of AHF, less is known about the hyperacute effects of bilevel positive airway pressure (BiPAP) ventilation on hemodynamics of patients admitted to ED for AHF. We therefore aimed to assess the effect of BiPAP ventilation on principal hemodynamic, respiratory, pulse oximetry, and microcirculation indexes in patients admitted to ED for AHF, needing NIV. METHODS: Twenty consecutive patients admitted to ED for AHF and left ventricular systolic dysfunction, needing NIV, were enrolled in the study; all patients were treated with NIV in BiPAP mode. The following parameters were measured at admission to ED (T0, baseline before treatment), 3 hours after admission and initiation of BiPAP NIV (T1), and after 6 hours (T2): arterial blood oxygenation (pH, partial pressure of oxygen in the alveoli/fraction of inspired oxygen ratio, Paco2, lactate concentration, HCO3-), hemodynamics (tricuspid annular plane systolic excursion, transpulmonary gradient, transaortic gradient, inferior vena cava diameter, brain natriuretic peptide [BNP] levels), microcirculation perfusion (end-tidal CO2 [etco2], peripheral venous oxygen saturation [SpvO2]). RESULTS: All evaluated indexes significantly improved over time (analysis of variance, P < .001 in quite all cases.). CONCLUSIONS: The BiPAP NIV may rapidly ameliorate several hemodynamic, arterial blood gas, and microcirculation indexes in patients with AHF and left ventricular systolic dysfunction.

Effect of arterial puncture on ventilation.

BACKGROUND: Clinicians frequently assume that during arterial puncture for measuring arterial blood gases patients hyperventilate from pain and anxiety. This assumption leads clinicians to falsely interpret a PaCO2 and pH near the upper limit of normal as a chronic respiratory acidosis corrected by an acute respiratory alkalosis. OBJECTIVE: Determine if participants hyperventilate during arterial puncture from pain and anxiety. METHODS: We recruited participants from a pulmonary function laboratory referred for arterial blood gas measurement. We excluded those with heart failure and included those with any respiratory condition (COPD, asthma, sleep apnea). We measured end tidal PCO2 (PETCO2), respiratory rate, and heart rate 15 min before topical anesthesia, during anesthesia, during arterial puncture, and 15 min later. We assessed generalized anxiety before and measured pain during and after arterial puncture. RESULTS: 24 participants were recruited (age: 54 ± 12 years; men: 54%). PaCO2 was 41 ± 5 mmHg. One had acute respiratory alkalosis. Respiratory rate increased from (19 ± 6 breaths per minute (bpm)) before to a maximum (21 ± 6 bpm) during arterial puncture (p = 0.001). Heart rate was stable throughout. The lowest PETCO2 during the procedure (35 ± 5) was similar to PETCO2 before the procedure (p = 0.1). The change in PETCO2 and respiratory rate did not correlate with pain, anxiety, or lung function. CONCLUSION: Respiratory rate increased slightly during arterial puncture without any change in PETCO2. Hence, acid-base status must be interpreted without the assumption of procedure induced hyperventilation.

White sturgeon (Acipenser transmontanus) acid-base regulation differs in response to different types of acidoses.

White sturgeon (Acipenser transmontanus) completely protect intracellular tissue pH (pHi) despite large reductions in extracellular (blood) pH (pHe), termed preferential pHi regulation, in response to elevated environmental PCO2 (hypercarbia) and in general appear to be relatively resilient to stressors. Preferential pHi regulation is thought to be associated with hypercarbia tolerance in general, but has also recently been observed to protect pHi against metabolic acidoses induced by exhaustive exercise and anoxia in a tropical air breathing catfish. We hypothesized that preferential pHi regulation may also be a general strategy of acid-base regulation in sturgeon. To address this hypothesis, severe acidoses were imposed to reduce pHe, and the presence or absence of preferential pHi regulation was assessed in red blood cells (RBC), heart, brain, liver and white muscle. A respiratory acidosis was imposed using hyperoxia, while metabolic acidoses were induced by exhaustive exercise, anoxia or air exposure. Reductions in pHe occurred following hyperoxia (0.15 units), exhaustive exercise (0.30 units), anoxia (0.10 units) and air exposure (0.35 units); all acidoses reduced RBC pHi. Following hyperoxia, heart, brain and liver pHi were preferentially regulated against the reduction in pHe, similar to hypercarbia exposure. Following all metabolic acidoses heart pHi was protected and brain pHi remained unchanged following exhaustive exercise and air exposure, however, brain pHi was reduced following anoxia. Liver and white muscle pHi were reduced following all metabolic acidoses. These results suggest preferential pHi regulation may be a general strategy during respiratory acidoses but during metabolic acidoses, the response differs between source of acidoses and tissues.

Nasal flaring as a clinical sign of respiratory acidosis in patients with dyspnea.

OBJECTIVE: To determine whether the presence of nasal flaring is a clinical sign of respiratory acidosis in patients attending emergency departments for acute dyspnea. METHODS: Single-center, prospective, observational study of patients aged over 15 requiring urgent attention for dyspnea, classified as level II or III according to the Andorran Triage Program and who underwent arterial blood gas test on arrival at the emergency department. The presence of nasal flaring was evaluated by two observers. Demographic and clinical variables, signs of respiratory difficulty, vital signs, arterial blood gases and clinical outcome (hospitalization and mortality) were recorded. Bivariate and multivariate analyses were performed using logistic regression models. RESULTS: The sample comprised 212 patients, mean age 78years (SD=12.8), of whom 49.5% were women. Acidosis was recorded in 21.2%. Factors significantly associated with the presence of acidosis in the bivariate analysis were the need for pre-hospital medical care, triage level II, signs of respiratory distress, presence of nasal flaring, poor oxygenation, hypercapnia, low bicarbonates and greater need for noninvasive ventilation. Nasal flaring had a positive likelihood ratio for acidosis of 4.6 (95% CI 2.9-7.4). In the multivariate analysis, triage level II (aOR 5.16; 95% CI: 1.91 to 13.98), the need for oxygen therapy (aOR 2.60; 95% CI: 1.13-5.96) and presence of nasal flaring (aOR 6.32; 95% CI: 2.78-14.41) were maintained as factors independently associated with acidosis. CONCLUSIONS: Nasal flaring is a clinical sign of severity in patients requiring urgent care for acute dyspnea, which has a strong association with acidosis and hypercapnia.

Blood Gas Analyzers.

Acid-base and respiratory disturbances are common in sick and hospitalized veterinary patients; therefore, blood gas analyzers have become integral diagnostic and monitoring tools. This article will discuss uses of blood gas analyzers, types of samples that can be used, sample collection methods, potential sources of error, and potential alternatives to blood gas analyzers and their limitations. It will also discuss the types of analyzers that are available, logistical considerations that should be taken into account when purchasing an analyzer, and the basic principles of how these analyzers work.

Differences in baseline factors and survival between normocapnia, compensated respiratory acidosis and decompensated respiratory acidosis in COPD exacerbation: A pilot study.

BACKGROUND AND OBJECTIVE: Patients with chronic obstructive pulmonary disease (COPD) experiencing acute exacerbation (AE-COPD) with decompensated respiratory acidosis are known to have poor outcomes in terms of recurrent respiratory failure and death. However, the outcomes of AE-COPD patients with compensated respiratory acidosis are not known. METHODS: We performed a 1-year prospective, single-centre, cohort study in patients surviving the index admission for AE-COPD to compare baseline factors between groups with normocapnia, compensated respiratory acidosis and decompensated respiratory acidosis. Survival analysis was done to examine time to readmissions, life-threatening events and death. RESULTS: A total of 250 patients fulfilling the inclusion and exclusion criteria were recruited and 245 patients were analysed. Compared with normocapnia, both compensated and decompensated respiratory acidosis are associated with lower FEV1 % (P < 0.001), higher GOLD stage (P = 0.003, <0.001) and higher BODE index (P = 0.038, 0.001) and a shorter time to life-threatening events (P < 0.001). Comparing compensated and decompensated respiratory acidosis, there was no difference in FEV1 (% predicted) (P = 0.15), GOLD stage (P = 0.091), BODE index (P = 0.158) or time to life-threatening events (P = 0.301). High PaCO2 level (P = 0.002) and previous use of non-invasive ventilation (NIV) in acute setting (P < 0.001) are predictive factors of future life-threatening events by multivariate analysis. CONCLUSIONS: Compared with normocapnia, both compensated and decompensated respiratory acidosis are associated with poorer lung function and higher risk of future life-threatening events. High PaCO2 level and past history of NIV use in acute settings were predictive factors for future life-threatening events. Compensated respiratory acidosis warrants special attention and optimization of medical therapy as it poses risk of life-threatening events.

Enhanced Extracorporeal CO2 Removal by Regional Blood Acidification: Effect of Infusion of Three Metabolizable Acids.

Acidification of blood entering a membrane lung (ML) with lactic acid enhances CO2 removal (VCO2ML). We compared the effects of infusion of acetic, citric, and lactic acids on VCO2ML. Three sheep were connected to a custom-made circuit, consisting of a Hemolung device (Alung Technologies, Pittsburgh, PA), a hemofilter (NxStage, NxStage Medical, Lawrence, MA), and a peristaltic pump recirculating ultrafiltrate before the ML. Blood flow was set at 250 ml/min, gas flow (GF) at 10 L/min, and recirculating ultrafiltrate flow at 100 ml/min. Acetic (4.4 M), citric (0.4 M), or lactic (4.4 M) acids were infused in the ultrafiltrate at 1.5 mEq/min, for 2 hours each, in randomized fashion. VCO2ML was measured by the Hemolung built-in capnometer. Circuit and arterial blood gas samples were collected at baseline and during acid infusion. Hemodynamics and ventilation were monitored. Acetic, citric, or lactic acids similarly enhanced VCO2ML (+35%), from 37.4 ± 3.6 to 50.6 ± 7.4, 49.8 ± 5.6, and 52.0 ± 8.2 ml/min, respectively. Acids similarly decreased pH, increased pCO2, and reduced HCO3 of the post-acid extracorporeal blood sample. No significant effects on arterial gas values, ventilation, or hemodynamics were observed. In conclusion, it is possible to increase VCO2ML by more than one-third using any one of the three metabolizable acids.