Transcutaneous Carbon Dioxide Monitoring in Subjects With Acute Respiratory Failure and Severe Hypercapnia

Supporting patients with hypercapnia

Hypercapnia is commonly encountered by general and specialist respiratory clinicians. Patients at risk of developing hypercapnic respiratory failure include those with chronic obstructive pulmonary disease (COPD), obesity and neuromuscular disease. Such patients may present to clinicians acutely unwell on the acute medical take or during an inpatient deterioration, or be identified in the stable outpatient setting. In this review, we provide a practical guide to develop clinicians' knowledge, skills and confidence in promptly recognising and managing hypercapnic respiratory failure, and to promote national ventilation quality standards to encourage consistent delivery of high-quality care and optimise outcomes for patients.

Effect of N95 Respirator on Oxygen and Carbon Dioxide Physiologic Response: A Systematic Review and Meta-Analysis

During the COVID-19 pandemic, N95 respirators were commonly used in many situations. Respiratory problems from prolonged use of respirators were discussed in many studies, which show varied results. From the inconclusive results, the current systematic review and meta-analysis discerned the effects of the N95 respirator by assessing the oxygen and carbon dioxide changes in both high- and low-to-moderate-intensity physical activities in a healthy population. Thirteen studies were identified for inclusion in the study. In high-intensity physical activities, our meta-analysis showed borderline lower oxygen saturation and higher carbon dioxide partial pressure, but oxygen saturation did not change in low-to-moderate physical activity. The use of N95 respirators could statistically affect the physiologic changes of carbon dioxide and oxygen in high-intensity physical activity among healthy participants, but this may not be clinically significant. Some users who have certain health conditions, such as respiratory problems, should be informed of the clinical symptoms related to hypercarbia and hypoxia for the early detection of adverse effects of N95 respirators.

Application and Efficiency of Transnasal Humidified Rapid-Insufflation Ventilatory Exchange in Laryngeal Microsurgery

OBJECTIVES/HYPOTHESIS

This study aimed to analyze the feasibility of transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) during laryngeal microsurgery (LMS) and investigated its efficiency and application according to the location of the lesion.

STUDY DESIGN

Retrospective chart review.

METHODS

Patients over 20 years of age who underwent LMS without underlying cardiac, pulmonary, or cerebrovascular disease were retrospectively reviewed. Overall, 54 patients with endotracheal intubation (ETI) and 44 patients with THRIVE were included. The operation and anesthesia time, induction and emergence time, oxygen saturation (SpO₂ ), and transcutaneous carbon dioxide (TcCO₂ ) levels were analyzed and compared between the two ventilation methods according to disease subsite.

RESULTS

Compared with ETI, patients with THRIVE presented reduced operation time (16.3 ± 9.69 min vs. 21.9 ± 12.0 min), anesthesia time (33.6 ± 11.4 min vs. 45.4 ± 13.9 min), emergence time (6.73 ± 2.49 min vs. 8.52 ± 3.17 min), without significant decreases in SpO₂ but with increased TcCO₂ (10.9 ± 6.12% vs. 7.33 ± 3.86%). Comparing THRIVE to ETI for lesions at the glottis yielded similar findings, which were particularly more significant. However, lesions above the glottis presented no significant difference for any parameters between THRIVE and ETI groups. Lesions involving multiple subsites and prolonged operation time were risk factors for the intraoperative conversion of ventilation method.

CONCLUSION

THRIVE is reliable for maintaining oxygenation during LMS and is efficient in reducing the operation and emergence times, leading to shorter anesthesia time, especially for lesions at the glottis. However, caution is required administering THRIVE, when lesion involves multiple subsites, and when operation time is prolonged.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

Association of transcutaneous CO2 with respiratory support: a prospective double blind observational study in children with bronchiolitis and reactive airway disease

The use of clinical scoring to assess for severity of respiratory distress and respiratory failure is challenging due to subjectivity and interrater variability. Transcutaneous Capnography (TcpCO₂) can be used as an objective tool to assess a patient’s ventilatory status. This study was designed to assess for any correlation of continuous monitoring of TcpCO₂ with the respiratory clinical scores and deterioration in children admitted for acute respiratory distress. A prospective observational study over one year on children aged 2 weeks to 5 years admitted with acute respiratory distress or failure secondary to Bronchiolitis and Reactive airway disease was performed. Continuous TcpCO₂ monitoring for upto 48 h was recorded. Investigators, bedside physicians, respiratory therapists, and nurses were blinded from the transcutaneous trends at the time of data collection. Total of 813 TcpCO₂ measurements at standard intervals of 30 min were obtained on 38 subjects. Subjects with abnormal TcpCO₂ (> 45 mmHg) were younger (6.9 ± 5.2 vs. 23.05 ± 17.7 months,) and were more likely to be on higher oxygen flow rate (0.52 L/min/kg vs 0.46 lier/min/kg, p = 0.004) and higher FiO₂ (38.4 vs 33.6, p < 0.001 using heated high flow nasal cannula. No difference was found in bronchiolitis score or PEW score in subjects with normal and abnormal TcpCO₂. A small but statistically significant increase in TcpCO₂ was observed at the escalation of care. Even though odds of escalation of care are higher with abnormal TcpCO₂ (OR 1.92), this difference did not reach statistical significance. pCO₂ can provide additive information for non-invasive clinical monitoring of children requiring varying respiratory support; however, it does not provide predictive value for escalation or de-escalation of care.

Evaluating a novel formula for noninvasive estimation of arterial carbon dioxide during post-resuscitation care

BACKGROUND

Controlling arterial carbon dioxide is paramount in mechanically ventilated patients, and an accurate and continuous noninvasive monitoring method would optimize management in dynamic situations. In this study, we validated and further refined formulas for estimating partial pressure of carbon dioxide with respiratory gas and pulse oximetry data in mechanically ventilated cardiac arrest patients.

METHODS

A total of 4741 data sets were collected retrospectively from 233 resuscitated patients undergoing therapeutic hypothermia. The original formula used to analyze the data is PaCO₂ -est1 = PETCO₂  + k[(PIO₂  - PETCO₂ ) - PaO₂ ]. To achieve better accuracy, we further modified the formula to PaCO₂ -est2 = k₁ *PETCO₂  + k₂ *(PIO₂  - PETCO₂ ) + k₃ *(100-SpO₂ ). The coefficients were determined by identifying the minimal difference between the measured and calculated arterial carbon dioxide values in a development set. The accuracy of these two methods was compared with the estimation of the partial pressure of carbon dioxide using end-tidal carbon dioxide.

RESULTS

With PaCO₂ -est1, the mean difference between the partial pressure of carbon dioxide, and the estimated carbon dioxide was 0.08 kPa (SE ±0.003); with PaCO₂ -est2 the difference was 0.036 kPa (SE ±0.009). The mean difference between the partial pressure of carbon dioxide and end-tidal carbon dioxide was 0.72 kPa (SE ±0.01). In a mixed linear model, there was a significant difference between the estimation using end-tidal carbon dioxide and PaCO₂ -est1 (P < .001) and PaCO₂ -est2 (P < .001) respectively.

CONCLUSIONS

This novel formula appears to provide an accurate, continuous, and noninvasive estimation of arterial carbon dioxide.

Arterial and transcutaneous variability and agreement between multiple successive measurements of carbon dioxide in patients with chronic obstructive lung disease

PURPOSE

This study evaluates agreement between carbon dioxide measured arterial (PaCO₂) and transcutaneous (PtcCO₂) over time, by repeated successive measures, taking into consideration the inherent variability of arterial measurements.

METHODS AND RESULTS

11 patients receiving LTOT, with severe to very severe COPD in a stable phase were studied. Repeated arterial blood samples were drawn and PtcCO₂ measured simultaneously at the ear lobe. Bland-Altman analysis was used to evaluate 95 % limits of agreement (LoA). 194 paired samples were analysed. Following correction for bias, the difference between PaCO₂ and PtCO₂ during dynamic conditions was 0.02 kPa and LoA 0.94 to -0.90 kPa while 29 % of PtCO₂ measurements were outside the range of variability for arterial measurements.

CONCLUSION

PtcCO₂ corrected for intra-patient bias provide reasonable description of PaCO₂ values within but not outside steady state conditions. Our results suggest that PtcCO₂ is a valuable method for monitoring in chronic rather than acute conditions when bias can be removed.

Transcutaneous PCO2 monitoring in critically ill patients: update and perspectives

The physiology of venous and tissue CO₂ monitoring has a long and well-established physiological background, leading to the technological development of different tissue capnometric devices, such as transcutaneous capnometry monitoring (TCM). To outline briefly, measuring transcutaneous PCO₂ (tcPCO₂) depends on at least three main phenomena: (I) the production of CO₂ by tissues (VCO₂), (II) the removal of CO₂ from the tissues by perfusion (wash-out phenomenon), and (III) the reference value of CO₂ at tissue inlet represented by arterial CO₂ content (approximated by arterial PCO₂, or artPCO₂). For this reason, there are, at present, roughly two clinical uses for tcPCO₂ measurement: a respiratory approach where tcPCO₂ is likely to estimate and non-invasively track artPCO₂; and a hemodynamic under-estimate use where tcPCO₂ can reflect tissue perfusion, summarized by a so-called "tc-art PCO₂ gap". Recent research shows that these two uses are not incompatible and could be combined. The spectrum of indications and validation studies in ICUs is summarized in this review to give a survey of the potential applications of TCM in critically ill patients, focusing mainly on its potential (micro)circulatory monitoring contribution. We strongly believe that the greatest benefit of measuring tcPCO₂ is not to only to estimate artPCO₂, but also to quantify the gap between these two values, which can then help clinicians continuously and noninvasively assess both respiratory and hemodynamic failures in critically ill patients.

How should we monitor patients with acute respiratory failure treated with noninvasive ventilation?

Noninvasive ventilation (NIV) is currently one of the most commonly used support methods in hypoxaemic and hypercapnic acute respiratory failure (ARF). With advancing technology and increasing experience, not only are indications for NIV getting broader, but more severe patients are treated with NIV. Depending on disease type and clinical status, NIV can be applied both in the general ward and in high-dependency/intensive care unit settings with different environmental opportunities. However, it is important to remember that patients with ARF are always very fragile with possible high mortality risk. The delay in recognition of unresponsiveness to NIV, progression of respiratory failure or new-onset complications may result in devastating and fatal outcomes. Therefore, it is crucial to understand that timely action taken according to monitoring variables is one of the key elements for NIV success. The purpose of this review is to outline basic and advanced monitoring techniques for NIV during an ARF episode.

Utility of Transcutaneous Capnography for Optimization of Non-Invasive Ventilation Pressures

INTRODUCTION

Nocturnal Non-invasive Positive Pressure Ventilation (NPPV) is the treatment of choice in patients with chronic hypercapnic respiratory failure due to hypoventilation. Continuous oxygen saturation measured with a pulse oximeter provides a surrogate measure of arterial oxygen saturation but does not completely reflect ventilation. Currently, Partial Pressure of Arterial (PaCO2) measured by arterial blood analysis is used for estimating the adequacy of ventilatory support and serves as the gold standard.

AIM

To examine the safety, feasibility and utility of cutaneous capnography to re-titrate the non-invasive positive pressure ventilation settings in patients with chronic hypercapnic respiratory failure due to hypoventilation.

MATERIALS AND METHODS

Twelve patients with chronic hypercapnic respiratory failure prospectively underwent complete polysomnography and cutaneous capnography measurement on the ear lobe. Non-invasive ventilation pressures were adjusted with the aim of normalizing cutaneous carbon dioxide or at least reducing it by 10 to 15 mmHg. Sensor drift for cutaneous carbon dioxide of 0.7 mmHg per hour was integrated in the analysis.

RESULTS

Mean baseline cutaneous carbon dioxide was 45.4 ± 6.5 mmHg and drift corrected awake value was 45.1 ± 8.3 mmHg. The correlation of baseline cutaneous carbon dioxide and the corrected awake cutaneous carbon dioxide with arterial blood gas values were 0.91 and 0.85 respectively. Inspiratory positive airway pressures were changed in nine patients (75%) and expiratory positive airway pressures in eight patients (66%). Epworth sleepiness score before and after the study showed no change in five patients, improvement in six patients and deterioration in one patient.

CONCLUSION

Cutaneous capnography is feasible and permits the optimization of non-invasive ventilation pressure settings in patients with chronic hypercapnic respiratory failure due to hypoventilation. Continuous cutaneous capnography might serve as an important additional tool to complement diurnal arterial carbon dioxide tension values.