Wearing face masks while climbing stairs influences respiratory physiology

BACKGROUND

During the COVID-19 pandemic wearing face masks was mandatory. Nowadays, face masks are still encouraged indoors, especially in hospitals. People climbing stairs with masks describe unpredictable dyspnea.

METHODS

Healthy adults climbed 5 floors with and without a mask. Various cardio-respiratory parameters were measured, including O2-Saturation (O2-Sat) and End-tidal CO2 (EtCO2), at baseline and on the top floor. Subjective indexes, such as Borg's scale, were evaluated.

RESULTS

Thirty-two volunteers (16 males), median age 39 years (IQR 32.5-43), median BMI=23.6 (IQR 21.5-25.1), with good fitness levels, participated. Comparing baseline to end-activity, median (IQR): O2-Sat change was -1.0% (-2-0) without mask, versus -3.0% (-4-0) with mask, p=0.003; EtCO2 +7.0 (+3.3-+9) without mask, versus +8.0 (+6 -+12) with mask, p=0.0001. Hypercarbia was seen in 5 (15.6%) participants without mask, median=48mmHg (IQR 47.5-51), and in 11 (34%) participants with mask, median=50mmHg (IQR 47-54), p<0.001. Desaturation (O2-Sat<95%) was seen in 5 (15.6%) participants without mask, median=94% (IQR 93-94%), and in 10 (31%) participants with mask, median=91.5% (IQR 90-93%), p=0.06. Regression analysis demonstrated that only male sex was significantly associated with abnormal EtCO2 (OR=26.4, 95%CI=1.9-366.4, p=0.005). Ascent duration increased from median (IQR) of 94 seconds (86-100) without mask to 98 seconds (89-107) with mask, p<0.001. Borg's scale of perceived exertion (range 0-10) increased from median (IQR) of 3.0 (2.5-3.87) without mask to 4.0 (3.0-4.37) with mask, p<0.001.

CONCLUSIONS

During routine daily activities, such as stair-climbing, face masks cause dyspnea, and have measurable influences on ventilation, including true desaturation and hypercapnia, especially in males.

Carbon dioxide and MAPK signalling: towards therapy for inflammation

Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.

Severe subcutaneous emphysema caused by small injury to the abdominal wall during robot-assisted laparoscopic radical prostatectomy

A 67-year-old man underwent RARP in the Trendelenburg position with pneumoperitoneum at 12 mmHg. Gradual elevation of End-tidal CO2(EtCO2) began, and extensive subcutaneous emphysema was recognized when EtCO2 reached 58 mmHg. After interruption of pneumoperitoneum, careful observation of the surgical field led to detect an injury of the abdominal wall of 1 cm in length, suggesting the cause of severe subcutaneous emphysema. The injury was repaired and RARP was terminated without any cardiovascular problems. Attention should be paid that even minor abdominal wall injury could lead to severe subcutaneous emphysema which may cause respiratory or cardiovascular problems during laparoscopic surgeries.

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Severe subcutaneous emphysema with severe hypercarbia occurred during RARP.

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A small but deep abdominal wall injury cause severe subcutaneous emphysema.

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Minor abdominal wall injury lead to subcutaneous emphysema, which could be fatal.

The association of acute hypercarbia and plasma potassium concentration during laparoscopic surgery: a retrospective observational study

BACKGROUND

It is uncertain whether increases in PaCO₂ during surgery lead to an increase in plasma potassium concentration and, if so, by how much. Hyperkalaemia may result in cardiac arrhythmias, muscle weakness or paralysis. The key objectives were to determine whether increases in PaCO₂ during laparoscopic surgery induce increases in plasma potassium concentrations and, if so, to determine the magnitude of such changes.

METHODS

A retrospective observational study of adult patients undergoing laparoscopic abdominal surgery was perfomed. The independent association between increases in PaCO₂ and changes in plasma potassium concentration was assessed by performing arterial blood gases within 15 min of induction of anaesthesia and within 15 min of completion of surgery.

RESULTS

289 patients were studied (mean age of 63.2 years; 176 [60.9%] male, and mean body mass index of 29.3 kg/m²). At the completion of the surgery, PaCO₂ had increased by 5.18 mmHg (95% CI 4.27 mmHg to 6.09 mmHg) compared to baseline values (P < 0.001) with an associated increase in potassium concentration of 0.25 mmol/L (95% CI 0.20 mmol/L to 0.31 mmol/L, P < 0.001). On multiple regression analysis, PaCO₂ changes significantly predicted immediate changes in plasma potassium concentration and could account for 33.1% of the variance (r² = 0.331, f(3,259) = 38.915, P < 0.001). For each 10 mmHg increment of PaCO₂ the plasma potassium concentration increased by 0.18 mmol/L.

CONCLUSION

In patients receiving laparoscopic abdominal surgery, there is an increase in PaCO₂ at the end of surgery, which is independently associated with an increase in plasma potassium concentration. However, this effect is small and is mostly influenced by intravenous fluid therapy (Plasma-Lyte 148 solution) and the presence of diabetes. Trial registration Retrospectively registered in the Australian New Zealand Clinical Trials Registry (Trial Number: ACTRN12619000716167).

Adherence to Positive Airway Pressure Therapy in Obesity Hypoventilation Syndrome

Because of the prevalence of extreme obesity in the United States, there has been an increase in prevalence of obesity hypoventilation syndrome (OHS). There is limited information on the characteristics and pattern of positive airway pressure (PAP) adherence in patients with OHS compared with eucapnic patients with obstructive sleep apnea (OSA). This article discusses in detail the impact of PAP therapy on outcomes in patients with OHS, compares adherence between continuous PAP and noninvasive ventilation in OHS, and compares PAP adherence in patients with OHS to patients with moderate to severe OSA enrolled in clinical trials designed to improve CPAP adherence.

Postnatal development of diving physiology: implications of anthropogenic disturbance for immature marine mammals

Marine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving mechanisms to prolong aerobically supported dives to great depths, while typically avoiding (or tolerating) hypoxia, hypercarbia, acidosis and decompression sickness (DCS). Over the last few decades, research has revealed that diving physiology is underdeveloped at birth. Here, I review the postnatal development of the body's oxygen stores, cardiorespiratory system and other attributes of diving physiology for pinnipeds and cetaceans to assess how physiological immaturity makes young marine mammals vulnerable to disturbance. Generally, the duration required for body oxygen stores to mature varies across species in accordance with the maternal dependency period, which can be over 2 years long in some species. However, some Arctic and deep-diving species achieve mature oxygen stores comparatively early in life (prior to weaning). Accelerated development in these species supports survival during prolonged hypoxic periods when calves accompany their mothers under sea ice and to the bathypelagic zone, respectively. Studies on oxygen utilization patterns and heart rates while diving are limited, but the data indicate that immature marine mammals have a limited capacity to regulate heart rate (and hence oxygen utilization) during breath-hold. Underdeveloped diving physiology, in combination with small body size, limits diving and swimming performance. This makes immature marine mammals particularly vulnerable to mortality during periods of food limitation, habitat alterations associated with global climate change, fishery interactions and other anthropogenic disturbances, such as exposure to sonar.

Effects of hypercarbia on arterial oxygenation during one-lung ventilation: prospective randomized crossover study

Background

This study aimed to evaluate the effects of hypercarbia on arterial oxygenation during one-lung ventilation (OLV).

Methods

Fifty adult patients undergoing elective video-assisted thoracoscopic lobectomy or pneumonectomy were enrolled. Group I patients (n = 25) were first maintained at normocarbia (PaCO₂: 38–42 mmHg) for 30 min and then at hypercarbia (45–50 mmHg). In Group II patients (n = 25), PaCO₂ was maintained in the reverse order. Arterial oxygen partial pressure (PaO₂), respiratory variables, hemodynamic variables, and hemoglobin concentration were compared during normocarbia and hypercarbia. Arterial O₂ content and O₂ delivery were calculated.

Results

PaO₂ values during normocarbia and hypercarbia were 66.5 ± 10.6 and 79.7 ± 17.3 mmHg, respectively (mean difference: 13.2 mmHg, 95% CI for difference of means: 17.0 to 9.3, P < 0.001). SaO₂ values during normocarbia and hypercarbia were 92.5 ± 4.8% and 94.3 ± 3.1% (P = 0.009), respectively. Static compliance of the lung (33.0 ± 5.4 vs. 30.4 ± 5.3 ml/cmH₂O, P < 0.001), arterial O₂ content (15.4 ± 1.4 vs. 14.9 ± 1.5 ml/dl, P < 0.001) and O₂ delivery (69.9 ± 18.4 vs. 65.1 ± 18.1 ml/min, P < 0.001) were significantly higher during hypercarbia than during normocarbia.

Conclusions

Hypercarbia increases PaO₂ and O₂ carrying capacity and improves pulmonary mechanics during OLV, suggesting that it may help manage oxygenation during OLV. Therefore, permissive hypercarbia may be a simple and valuable modality to manage arterial oxygenation during OLV.

Preferential intracellular pH regulation is a common trait amongst fishes exposed to high environmental CO2

Acute (<96 h) exposure to elevated environmental CO2 (hypercarbia) induces a pH disturbance in fishes that is often compensated by concurrent recovery of intracellular and extracellular pH (pHi and pHe, respectively; coupled pH regulation). However, coupled pH regulation may be limited at CO2 partial pressure (PCO2 ) tensions far below levels that some fishes naturally encounter. Previously, four hypercarbia-tolerant fishes had been shown to completely and rapidly regulate heart, brain, liver and white muscle pHi during acute exposure to >4 kPa PCO2  (preferential pHi regulation) before pHe compensation was observed. Here, we test the hypothesis that preferential pHi regulation is a widespread strategy of acid-base regulation among fish by measuring pHi regulation in 10 different fish species that are broadly phylogenetically separated, spanning six orders, eight families and 10 genera. Contrary to previous views, we show that preferential pHi regulation is the most common strategy for acid-base regulation within these fishes during exposure to severe acute hypercarbia and that this strategy is associated with increased hypercarbia tolerance. This suggests that preferential pHi regulation may confer tolerance to the respiratory acidosis associated with hypercarbia, and we propose that it is an exaptation that facilitated key evolutionary transitions in vertebrate evolution, such as the evolution of air breathing.

Swimming performance of a freshwater fish during exposure to high carbon dioxide

Deterring the spread of invasive fishes is a challenge for managers, and bigheaded carp (including bighead and silver carp, Hypophthalmichthys spp.) are invasive fish that have spread throughout large portions of the Mississippi River basin and threaten to invade the Great Lakes' ecosystem. Studies have shown that elevated levels of carbon dioxide gas (CO₂) have the ability to act as a nonphysical fish barrier, but little work has been done on the efficacy of CO₂ to deter fish movement in flowing water. An annular swim flume was used to measure U_burst and sprint duration of the model species largemouth bass (Micropterus salmoides) across a range of pCO₂ levels (< 400 μatm [ambient]; 10,000 μatm; 50,000 μatm; and 100,000 μatm). This species was tested as a proxy because of the likelihood of a similar CO₂ response being produced, as well as constraints in obtaining and housing appropriately sized Asian carp. A significant decrease in U_burst swimming occurred when exposed to 100,000 μatm. No effects on sprint duration were detected. In both swimming tests, 15% of fish lost equilibrium when exposed to 50,000 μatm pCO₂, while 50% of fish lost equilibrium when exposed to 100,000 μatm. Together, results define target levels for managers to impede the spread of largemouth bass and potentially other invasive freshwater fishes, helping guide policy to conserve aquatic ecosystems.

Water pH limits extracellular but not intracellular pH compensation in the CO2-tolerant freshwater fish Pangasianodon hypophthalmus

Preferentially regulating intracellular pH (pH_i) confers exceptional CO₂ tolerance on fish, but is often associated with reductions in extracellular pH (pH_e) compensation. It is unknown whether these reductions are due to intrinsically lower capacities for pH_e compensation, hypercarbia-induced reductions in water pH or other factors. To test how water pH affects capacities and strategies for pH compensation, we exposed the CO₂-tolerant fish Pangasianodon hypophthalmus to 3 kPa P _CO2  for 20 h at an ecologically relevant water pH of 4.5 or 5.8. Brain, heart and liver pH_i was preferentially regulated in both treatments. However, blood pH_e compensation was severely reduced at water pH 4.5 but not 5.8. This suggests that low water pH limits acute pH_e but not pH_i compensation in fishes preferentially regulating pH_i Hypercarbia-induced reductions in water pH might therefore underlie the unexplained reductions to pH_e compensation in fishes preferentially regulating pH_i, and may increase selection for preferential pH_i regulation.

Control of air-breathing in fishes: Central and peripheral receptors

This review considers the environmental and systemic factors that can stimulate air-breathing responses in fishes with bimodal respiration, and how these may be controlled by peripheral and central chemoreceptors. The systemic factors that stimulate air-breathing in fishes are usually related to conditions that increase the O₂ demand of these animals (e.g. physical exercise, digestion and increased temperature), while the environmental factors are usually related to conditions that impair their capacity to meet this demand (e.g. aquatic/aerial hypoxia, aquatic/aerial hypercarbia, reduced aquatic hidrogenionic potential and environmental pollution). It is now well-established that peripheral chemoreceptors, innervated by cranial nerves, drive increased air-breathing in response to environmental hypoxia and/or hypercarbia. These receptors are, in general, sensitive to O₂ and/or CO₂/H⁺ levels in the blood and/or the environment. Increased air-breathing in response to elevated O₂ demand may also be driven by the peripheral chemoreceptors that monitor O₂ levels in the blood. Very little is known about central chemoreception in air-breathing fishes, the data suggest that central chemosensitivity to CO₂/H⁺ is more prominent in sarcopterygians than in actinopterygians. A great deal remains to be understood about control of air-breathing in fishes, in particular to what extent control systems may show commonalities (or not) among species or groups that have evolved air-breathing independently, and how information from the multiple peripheral (and possibly central) chemoreceptors is integrated to control the balance of aerial and aquatic respiration in these animals.

Motor neurone disease-associated neck pain misdiagnosed as cervical spondylosis: A case report and literature review

BACKGROUND

Motor neurone disease (MND) is a chronic, progressive and currently incurable neurodegenerative disorder. Although pain as a symptom appears in many patients with MND, it is often misdiagnosed as other diseases when occurs before the onset of weakness. Patients are often assigned to non-neurological departments due to the atypical symptoms, which can lead to diagnostic delay and inappropriate treatment.

OBJECTIVE

To analyze the causes of misdiagnosis and improve the clinician's understanding of neck pain in patients with MND.

METHODS

We reviewed relevant literature and retrospectively reported a misdiagnosis case of MND-associated neck pain.

RESULTS

A case of MND presenting prominently as neck pain was suspected of suffering from cervical spondylosis and wrongly assigned to orthopedic clinic. When eventually being diagnosed as MND, his neck pain was found to be caused by intracranial hypertension (ICH) resulting from hypoxia via insidious respiratory failure through ventilator insufficiency.

CONCLUSION

Careful evaluation of the clinical progression of the symptoms, extensive EMG and nerve conduction study, as well as the establishment of better clinical approach to the diagnosis and higher public awareness allow a reduction of misdiagnosis.

Effects of water ionic composition on acid-base regulation in rainbow trout, during hypercarbia at rest and during sustained exercise

Aquatic hypercarbia (elevated environmental CO₂) results in a blood acidosis in fish, which is compensated by the exchange of Na⁺ and/or Cl^- for its acid/base counterpart (H⁺, HCO₃^-) across the gill epithelium. To date, no studies exist on how a single species, capable of inhabiting both fresh and saltwater, responds to hypercarbia, at rest or during sustained exercise. Rainbow trout was acclimated to soft water (in mmol l^- 1: Na⁺, 0.08; Cl^-, 0.05; pH 6.7-6.8), hard water (in mmol l^- 1: Na⁺, 2.4; Cl^-, 0.2; pH 7.9-8.0), or 85% saltwater (28 ppt) (in mmol l^- 1: Na⁺, 410; Cl^-, 476; pH 7.8-8.0). Acid-base relevant blood parameters were measured during a 1 kPa CO₂ hypercarbia exposure, both at rest and during sustained exercise (~ 60% U _crit). After 48 h of hypercarbia, resting hard-, and saltwater trout fully restored blood pH, whereas soft-water-acclimated trout was only 60.6 ± 10.5% recovered. In all fish, recovery was associated with an increase in plasma [HCO₃^-] and an equimolar reduction in plasma [Cl^-]. Following 8 h of hypercarbia during sustained exercise, saltwater fish fully restored blood pH, while soft- and hard water fish were 42 ± 18.1 and 64 ± 6.8% recovered, respectively. Results provide intra-specific support demonstrating that saltwater acclimated fish acid-base compensate faster than freshwater fish during hypercarbia. Furthermore, data indicate that recovery during hypercarbia in trout is more rapid during exercise than rest. This not only demonstrates an important link between ambient water ion levels and ability to recover from acid-base disturbances, but also it presents novel data, suggesting that exercise may enhance acid-base regulation.

Post-resuscitation arterial oxygen and carbon dioxide and outcomes after out-of-hospital cardiac arrest

OBJECTIVE

To determine if arterial oxygen and carbon dioxide abnormalities in the first 24h after return of spontaneous circulation (ROSC) are associated with increased mortality in adult out-of-hospital cardiac arrest (OHCA).

METHODS

We used data from the Resuscitation Outcomes Consortium (ROC), including adult OHCA with sustained ROSC ≥1h after Emergency Department arrival and at least one arterial blood gas (ABG) measurement. Among ABGs measured during the first 24h of hospitalization, we identified the presence of hyperoxemia (PaO2≥300mmHg), hypoxemia (PaO2<60mmHg), hypercarbia (PaCO2>50mmHg) and hypocarbia (PaCO2<30mmHg). We evaluated the associations between oxygen and carbon dioxide abnormalities and hospital mortality, adjusting for confounders.

RESULTS

Among 9186 OHCA included in the analysis, hospital mortality was 67.3%. Hyperoxemia, hypoxemia, hypercarbia, and hypocarbia occurred in 26.5%, 19.0%, 51.0% and 30.6%, respectively. Initial hyperoxemia only was not associated with hospital mortality (adjusted OR 1.10; 95% CI: 0.97-1.26). However, final and any hyperoxemia (1.25; 1.11-1.41) were associated with increased hospital mortality. Initial (1.58; 1.30-1.92), final (3.06; 2.42-3.86) and any (1.76; 1.54-2.02) hypoxemia (PaO2<60mmHg) were associated with increased hospital mortality. Initial (1.89; 1.70-2.10); final (2.57; 2.18-3.04) and any (1.85; 1.67-2.05) hypercarbia (PaCO2>50mmHg) were associated with increased hospital mortality. Initial (1.13; 0.90-1.41), final (1.19; 1.04-1.37) and any (1.01; 0.91-1.12) hypocarbia (PaCO2<30mmHg) were not associated with hospital mortality.

CONCLUSIONS

In the first 24h after ROSC, abnormal post-arrest oxygen and carbon dioxide tensions are associated with increased out of-hospital cardiac arrest mortality.

Preferential intracellular pH regulation: hypotheses and perspectives

The regulation of vertebrate acid-base balance during acute episodes of elevated internal PCO2  is typically characterized by extracellular pH (pHe) regulation. Changes in pHe are associated with qualitatively similar changes in intracellular tissue pH (pHi) as the two are typically coupled, referred to as 'coupled pH regulation'. However, not all vertebrates rely on coupled pH regulation; instead, some preferentially regulate pHi against severe and maintained reductions in pHe Preferential pHi regulation has been identified in several adult fish species and an aquatic amphibian, but never in adult amniotes. Recently, common snapping turtles were observed to preferentially regulate pHi during development; the pattern of acid-base regulation in these species shifts from preferential pHi regulation in embryos to coupled pH regulation in adults. In this Commentary, we discuss the hypothesis that preferential pHi regulation may be a general strategy employed by vertebrate embryos in order to maintain acid-base homeostasis during severe acute acid-base disturbances. In adult vertebrates, the retention or loss of preferential pHi regulation may depend on selection pressures associated with the environment inhabited and/or the severity of acid-base regulatory challenges to which they are exposed. We also consider the idea that the retention of preferential pHi regulation into adulthood may have been a key event in vertebrate evolution, with implications for the invasion of freshwater habitats, the evolution of air breathing and the transition of vertebrates from water to land.

Molecular, behavioral, and performance responses of juvenile largemouth bass acclimated to an elevated carbon dioxide environment

Aquatic hypercarbia, either naturally occurring or anthropogenically induced, can have extensive impacts on aquatic environments and resident organisms. While the impact of acute hypercarbia exposure on the behavior and physiology of fishes has been well studied, relatively little work has examined the physiological impact and acclimation capacity of fishes to chronic hypercarbia. To better understand the impacts of prolonged hypercarbia exposure, largemouth bass were held at ambient CO2 (13 mg L(-1)) and elevated CO2 (31 mg L(-1); ≈ 21,000 µatm) for 58 days. Following this acclimation period, fish were subjected to three separate, yet complementary, experiments: (1) acute hypercarbia challenge of 120 mg L(-1) CO2 for 1 h to quantify physiological and molecular responses; (2) hypercarbia avoidance challenge to compare CO2 agitation and avoidance responses; and (3) swim performance challenge to quantify burst swimming performance. Acclimation to 31 mg L(-1) CO2 resulted in a significant constitutive upregulation of c-fos expression in erythrocytes, combined with significant constitutive expression of hsp70 in both gill and erythrocytes, relative to controls. Largemouth bass acclimated to elevated CO2 also had a reduced glucose response (relative to controls) following an acute CO2 exposure, indicating a reduced stress response to CO2 stressors. In addition, largemouth bass acclimated to elevated CO2 conditions required 50 % higher CO2 concentrations to illicit agitation behaviors and displayed prolonged burst swimming abilities in high CO2 environments relative to controls. Together, results demonstrate that largemouth bass exposed to chronic hypercarbia may possess a physiological advantage during periods of elevated CO2 relative to naïve fish, which may permit increased performance in hypercarbia.

Southmedic OxyMask(TM) compared with the Hudson RCI(®) Non-Rebreather Mask(TM): Safety and performance comparison

BACKGROUND

The non-rebreather mask (NRBM) is used for many applications and in many patient care scenarios in which hypoxemia and resultant hypoxia are a concern. The NRBM is a low-flow oxygen delivery system that is easily deployed and capable of delivering a relatively high fraction of inspired oxygen (FiO2).The potential for ineffective carbon dioxide (CO2) removal at low flow rates is a safety concern.

OBJECTIVE

The authors hypothesized that the use of an OxyMask (Southmedic Inc, Canada) would mitigate these safety concerns while still delivering a relatively high FiO2.

METHODS

Bench studies were performed in a third-party laboratory by qualified engineers (Piper Medical, USA). A Harvard Respirator Pump (Harvard Apparatus, USA), oxygen source, CO2 source and a mannequin head were used to simulate varying respiratory conditions. End tidal CO2 (EtCO2), FiO2, fraction of inspired CO2 and percent drop in CO2 in the first second of exhalation were measured at different mask flow rates and respiratory rates. There were two categories of flow rates: high-flow (15 L/min) and low-flow (2 L/min). In each flow group, the above parameters were measured using a tidal volume of 400 mL, inspiratory/expiratory ratio of 1:2, EtCO2 of 5% and a breathing frequency of 15, 20 or 24 breaths/min. Mask performance measurements were obtained and compared.

CONCLUSION

The OxyMask outperformed the traditional NRBM in each tested category. There was a higher inspired oxygen level, lower inspired CO2 level, and more efficient CO2 clearance at each mask flow level and simulated patient minute volume. This was especially true during conditions in which there were very low mask flow rates.

Persistent hypercarbia after resuscitation is associated with increased mortality in congenital diaphragmatic hernia patients

BACKGROUND

Within congenital diaphragmatic hernia (CDH) care, there have been attempts to identify clinical parameters associated with patient survival, including markers of postnatal pulmonary gas exchange. This study aimed to identify whether postnatal pulmonary gas exchange parameters correlated with CDH patient survival.

METHODS

A retrospective review was performed of isolated CDH neonates treated at a single institution from 1/2007 to 12/2013. Patient demographics, prenatal imaging, and postnatal clinical parameters, including arterial blood gas values within the first 24hours of life, were collected.

RESULTS

Seventy-four patients with isolated CDH were identified. Fifty-seven had fetal MRI. Overall, 30-day patient survival was 85%. Sixteen infants (22%) required ECMO within 24hours. Mean initial PaCO2 in nonsurvivors was higher, and infants who remained hypercarbic postresuscitation (72±19mmHg) had a worse prognosis than those who resuscitated to a normal PaCO2 (39±1.6mmHg) (p<0.001). Prenatal fetal lung volumes measured by MRI were not strongly correlated with PaCO2 levels.

CONCLUSION

CDH nonsurvivors are unable to maintain sufficient pulmonary gas exchange during the first 24hours of resuscitation. Furthermore, prenatal fetal lung volumes are weakly correlated with actual pulmonary gas exchange. These data may be useful for patient counseling during the resuscitative phase of CDH care.

Grossly delayed massive subcutaneous emphysema following laparoscopic left hemicolectomy: A case report

INTRODUCTION

Surgical emphysema is a known early complication of laparoscopic surgery, common during upper gastrointestinal and gynaecological surgery; the authors present the first case of delayed subcutaneous emphysema following a laparoscopic left hemicolectomy.

PRESENTATION OF CASE

A 52-year-old woman underwent a laparoscopic left hemicolectomy for a sigmoid malignancy; on the third post-operative day after an uneventful procedure, she developed a massive surgical emphysema involving her face, neck and chest with associated pneumoperitoneum but without any evidence of pneumothorax. A gastrograffin enema ruled out an anastomotic leak. Apart from a borderline tachycardia, mildly low saturations and an area of erythema in her right flank, she was totally asymptomatic. The emphysema resolved spontaneously around the 6th post-operative day.

DISCUSSION

Massive subcutaneous surgical emphysema after laparoscopic colorectal surgery is a rare complication and can me managed conservatively with a good outcome.

CONCLUSION

To our knowledge, this represents the first case of delayed massive surgical emphysema following colorectal surgery, the aetiology of which has still not been clearly explained, after exclusion of the most common causes.

Arterial blood carbonic Acid inversely determines lactic and organic acids

OBJECTIVE

To establish that arterial blood carbonic acid varies inversely with lactic acid in accordance with bicarbonate exchanging for lactate across cell membranes through the anion exchange mechanism to maintain the Gibbs-Donnan equilibrium.

STUDY DESIGN

Over 5 years, lactate was measured on all blood gases taken from neonatal admissions, as well as organic acid whenever electrolytes were required.

RESULTS

Arterial blood gases from 63 infants given high calcium TPN were analyzed. Twenty two needed continuous positive airways pressure (CPAP) only and 31 intermittent positive pressure ventilation (IPPV) and surfactant followed by CPAP to treat respiratory distress syndrome in 51 and meconium aspiration syndrome in 2. All survived and were free of infection. Excluded gases were those with high and falling lactate soon after delivery representing perinatal asphyxia, and those on dexamethasone. Strong inverse relations between carbonic and lactic acids were found at all gestational ages and, independent of glomerular filtration, between carbonic and organic acids. Lactate (mmol/L) = 62.53 X PCO2 (-0.96)(mmHg) r(2) 0.315, n 1232, p <0.001. Sixty divided by PCO2 is a convenient measure of physiological lactate at any given PCO2. In the first week, 9.13 ± 2.57% of arterial gases from infants on IPPV had lactates above 120/PCO2, significantly more than 4.74 ± 2.73% on CPAP (p<0.05) and 2.47 ± 2.39% on no support.

CONCLUSION

Changes in arterial blood carbonic acid cause immediate inverse changes in lactic acid, because their anions interchange across cell membranes according to the Gibbs -Donnan equilibrium. Increasing PCO2 from 40 to 120 mmHg decreased lactate from 1.5 mmol/L to 0.5 mmol/L, so that the sum of carbonic and lactic acids increased from 2.72 mmol/L to only 4.17 mmol/L. This helps explain the neuroprotective effect of hypercapnoea and highlights the importance of avoiding any degree of hypocapnoea in infants on IPPV.

Removing extra CO2 in COPD patients

For patients experiencing acute respiratory failure due to a severe exacerbation of chronic obstructive pulmonary disease (COPD), noninvasive positive pressure ventilation has been shown to significantly reduce mortality and hospital length of stay compared to respiratory support with invasive mechanical ventilation. Despite continued improvements in the administration of noninvasive ventilation (NIV), refractory hypercapnia and hypercapnic acidosis continue to prevent its successful use in many patients. Recent advances in extracorporeal gas exchange technology have led to the development of systems designed to be safer and simpler by focusing on the clinical benefits of partial extracorporeal carbon dioxide removal (ECCO2R), as opposed to full cardiopulmonary support. While the use of ECCO2R has been studied in the treatment of acute respiratory distress syndrome (ARDS), its use for acute hypercapnic respiratory during COPD exacerbations has not been evaluated until recently. This review will focus on literature published over the last year on the use of ECCO2R for removing extra CO2 in patients experiencing an acute exacerbation of COPD.

Nocturnal carbon dioxide monitoring in patients with idiopathic intracranial hypertension

BACKGROUND

Idiopathic intracranial hypertension may be associated with sleep apnea. This study evaluated the incidence of sleep breathing disorders in patients with idiopathic intracranial hypertension.

MATERIALS AND METHODS

Overnight respiratory monitoring was performed in 22 untreated patients with idiopathic intracranial pressure diagnosed at a tertiary medical center over a two-year period and 12 sex- and age-matched control subjects. Breathing measures included heart rate, respiratory rate,oxygen saturation, and continuous end-tidal capnography. Sleep quality and daily fatigue were assessed by self-report questionnaires.

RESULTS

Mean age of the study group was 32.6±12.2 years and of the control group, 37.0±12.9 years. Neither group had significant findings of hypoxia or hypercarbia during sleep, and there were no between-group differences in mean carbon dioxide level (patients, 35.8±4.41 mmHg; controls, 37.6±4.38 mmHg; p>0.02) or minimal oxygen saturation (96.35±1.99% and 5.69±1.71%, respectively; p>0.02). The study group had significantly more events of apnea (CO2) per hour of sleep than the control group (1.21±1.38 and 0.92±0.56, respectively; p=0.02), although values were still within normal range (<5/hr).

CONCLUSION

Idiopathic intracranial hypertension is not associated with a clinically significant nocturnal breathing abnormality, and hypercarbia is apparently not involved in the pathogenesis. However, it is possible that a subtle increase in paroxysmal sleep apnea (CO2) events might be sufficient to cause vasodilatation of the cerebral blood vessels, thereby increasing intracranial pressure. Screening for sleep apnea may be appropriate in idiopathic intracranial hypertension patients, and further studies are needed to clarify this issue.

Anesthetic course and complications that were encountered during endoscopic thyroidectomy -A case report-

Endoscopic thyroidectomy is gaining popularity, but it can increase the risk of certain complications. Carbon dioxide insufflation in the neck may cause adverse effects on hemodynamic and ventilatory aspects. We report the anesthetic course and complications that were encountered during endoscopic thyroidectomy. Although the surgery was successful, the patient developed signs of hypercarbia, subcutaneous emphysema and pneumothorax.

The use of chest band to prevent CO(2) subcutaneous emphysema expansion -Two case reports-

CO(2) subcutaneous emphysema is one of the complications of laparoscopic surgery using CO(2) gas. During laparoscopic surgery, CO(2) gas can spread to the entire body surface through the subcutaneous tissue layer. Extensive CO(2) subcutaneous emphysema results in hypercarbia and acute respiratory acidosis. Hypercarbia and acidosis can lead to decreased cardiac contractility and arrhythmia. A cloth band, 5 cm in width and 120 cm in length, was made with Velcro tape at both tips, and placed on the patient's xyphoid process level and inframammary fold to prevent CO(2) subcutaneous emphysema. This report describes two successful cases using a chest band to prevent the expansion of CO(2) subcutaneous emphysema.