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Williams EE, Dassios T, Harris C, Greenough A. Capnography waveforms: basic interpretation in neonatal intensive care. Front Pediatr 2024; 12:1396846. [PMID: 38638588 PMCID: PMC11024230 DOI: 10.3389/fped.2024.1396846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 03/26/2024] [Indexed: 04/20/2024] Open
Abstract
End-tidal capnography can provide useful clinical information displayed on the ventilator screen or bedside monitor. It is important that clinicians can assess and utilise this information to assist in identifying underlying complications and pulmonary pathology. Sudden change or loss of the CO2 waveform can act as a safety measure in alerting clinicians of a dislodged or blocked endotracheal tube, considering the concurrent flow and volume waveforms. Visual pattern recognition by the clinicians of commonly seen waveform traces may act as an adjunct to other modes of ventilatory monitoring techniques. Waveforms traces can aid clinical management, help identify cases of ventilation asynchrony between the infant and the ventilator. We present some common clinical scenarios where tidal capnography can be useful in the timely identification of pulmonary complication and for practical troubleshooting at the cot-side.
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Affiliation(s)
- Emma E. Williams
- Department of Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
| | - Theodore Dassios
- Department of Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
- Neonatal Intensive Care Centre, King’s College Hospital NHS Foundation Trust, London, United Kingdom
| | - Christopher Harris
- Department of Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
- Neonatal Intensive Care Centre, King’s College Hospital NHS Foundation Trust, London, United Kingdom
| | - Anne Greenough
- Department of Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
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Williams EE, Gareth Jones J, McCurnin D, Rüdiger M, Nanjundappa M, Greenough A, Dassios T. Functional morphometry: non-invasive estimation of the alveolar surface area in extremely preterm infants. Pediatr Res 2023; 94:1707-1713. [PMID: 37045946 PMCID: PMC10624622 DOI: 10.1038/s41390-023-02597-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 04/14/2023]
Abstract
BACKGROUND The main pathophysiologic characteristic of chronic respiratory disease following extremely premature birth is arrested alveolar growth, which translates to a smaller alveolar surface area (SA). We aimed to use non-invasive measurements to estimate the SA in extremely preterm infants. METHODS Paired measurements of the fraction of inspired oxygen and transcutaneous oxygen saturation were used to calculate the ventilation/perfusion ratio, which was translated to SA using Fick's law of diffusion. The SA was then adjusted using volumetric capnography. RESULTS Thirty infants with a median (range) gestational age of 26.3 (22.9-27.9) weeks were studied. The median (range) adjusted SA was 647.9 (316.4-902.7) cm2. The adjusted SA was lower in the infants who required home oxygen [637.7 (323.5-837.5) cm2] compared to those who did not [799.1 (444.2-902.7) cm2, p = 0.016]. In predicting the need for supplemental home oxygen, the adjusted SA had an area under the receiver operator characteristic curve of 0.815 (p = 0.017). An adjusted SA ≥688.6 cm2 had 86% sensitivity and 77% specificity in predicting the need for supplemental home oxygen. CONCLUSIONS The alveolar surface area can be estimated non-invasively in extremely preterm infants. The adjusted alveolar surface area has the potential to predict the subsequent need for discharge home on supplemental oxygen. IMPACT We describe a novel biomarker of respiratory disease following extremely preterm birth. The adjusted alveolar surface area index was derived by non-invasive measurements of the ventilation/perfusion ratio and adjusted by concurrent measurements of volumetric capnography. The adjusted alveolar surface area was markedly reduced in extremely preterm infants studied at 7 days of life and could predict the need for discharge home on supplemental oxygen. This method could be used at the bedside to estimate the alveolar surface area and provide an index of the severity of lung disease, and assist in monitoring, clinical management and prognosis.
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Affiliation(s)
- Emma E Williams
- Women and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - J Gareth Jones
- Cambridge University Clinical School, Hills Rd, Cambridge, UK
| | - Donald McCurnin
- Division of Neonatology, Department of Pediatrics, University of Texas Health, San Antonio, TX, USA
| | - Mario Rüdiger
- Neonatology and Pediatric Critical Care Medicine, Department of Pediatrics, Medizinische Fakultät, Carl Gustav Carus, TU Dresden, Dresden, Germany
- Saxony Center for Feto/Neonatal Health, Medizinische Fakultät, TU Dresden, Dresden, Germany
| | - Mahesh Nanjundappa
- Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, UK
| | - Anne Greenough
- Women and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, UK
| | - Theodore Dassios
- Women and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.
- Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, UK.
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Vallarino M, Quintela L, Jorge G, Lorenzo G, Nan C, Isper M, Bouchacourt JP, Grignola JC. SAMAY S24: a novel wireless 'online' device for real-time monitoring and analysis of volumetric capnography. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38083576 DOI: 10.1109/embc40787.2023.10340680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Volumetric capnography (VCap) provides information about CO2 exhaled per breath (VCO2br) and physiologic dead space (VDphys). A novel wireless device with a high response time CO2 mainstream sensor coupled with a digital flowmeter was designed to monitor all VCap parameters online in rabbits (SAMAY S24).Ten New Zealand rabbits were anesthetized and mechanically ventilated. VCO2br corresponds to the area under the VCap curve. We used the modified Langley method to assess the airway VD (VDaw) and the alveolar CO2 pressure. VDphys was estimated using Bohr's formula, and the alveolar VD was calculated by subtracting VDaw from VDphys. We compared (Bland-Altman) the critical VCap parameters obtained by SAMAY S24 (Langley) with the Functional Approximation based on the Levenberg-Marquardt Algorithm (FA-LMA) approach during closed and opened chest conditions.SAMAY S24 could assess dead space volumes and VCap shape in real time with similar accuracy and precision compared to the 'offline' FA-LMA approach. The opened chest condition impaired CO2 kinetics, decreasing the phase II slope, which was correlated with the volume of CO2 exhaled per minute.
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Dassios T, Williams EE, Jones JG, Greenough A. Pathophysiology of gas exchange impairment in extreme prematurity: Insights from combining volumetric capnography and measurements of ventilation/perfusion ratio. Front Pediatr 2023; 11:1094855. [PMID: 37009267 PMCID: PMC10050367 DOI: 10.3389/fped.2023.1094855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 02/28/2023] [Indexed: 04/04/2023] Open
Abstract
Background Infants born extremely preterm often suffer from respiratory disease and are invasively ventilated. We aimed to test the hypothesis that gas exchange in ventilated extremely preterm infants occurs both at the level of the alveoli and via mixing of fresh deadspace gas in the airways. Methods We measured the normalised slopes of phase II and phase III of volumetric capnography and related them with non-invasive measurements of ventilation to perfusion ratio (VA/Q) and right-to-left shunt in ventilated extremely preterm infants studied at one week of life. Cardiac right-to-left shunt was excluded by concurrent echocardiography. Results We studied 25 infants (15 male) with a median (range) gestational age of 26.0 (22.9-27.9) weeks and birth weight of 795 (515-1,165) grams. The median (IQR) VA/Q was 0.52 (0.46-0.56) and shunt was 8 (2-13) %. The median (IQR) normalised slope of phase II was 99.6 (82.7-116.1) mmHg and of phase III was 24.6 (16.9-35.0) mmHg. The VA/Q was significantly related to the normalised slope of phase III (ρ = -0.573, p = 0.016) but not to the slope of phase II (ρ = 0.045, p = 0.770). The right-to-left shunt was not independently associated with either the slope of phase II or the slope of phase III after adjusting for confounding parameters. Conclusions Abnormal gas exchange in ventilated extremely preterm infants was associated with lung disease at the alveolar level. Abnormal gas exchange at the level of the airways was not associated with quantified indices of gas exchange impairment.
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Affiliation(s)
- Theodore Dassios
- Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
- Neonatal Intensive Care Unit, Patras University Hospital, Patras, Greece
- Correspondence: Theodore Dassios
| | - Emma E. Williams
- Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
| | - J. Gareth Jones
- Cambridge University Clinical School, Cambridge, United Kingdom
| | - Anne Greenough
- Women and Children’s Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King’s College London, London, United Kingdom
- National Institute for Health Research (NIHR) Biomedical Research Centre Based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London, London, United Kingdom
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Volumetric capnography pre- and post-surfactant during initial resuscitation of premature infants. Pediatr Res 2022; 91:1551-1556. [PMID: 34023855 PMCID: PMC9197760 DOI: 10.1038/s41390-021-01578-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/19/2021] [Accepted: 04/22/2021] [Indexed: 02/03/2023]
Abstract
BACKGROUND Volumetric capnography allows for continuous monitoring of expired tidal volume and carbon dioxide. The slope of the alveolar plateau of the capnogram (SIII) could provide information regarding ventilation homogeneity. We aimed to assess the feasibility of measuring SIII during newborn resuscitation and determine if SIII decreased after surfactant indicating ventilation inhomogeneity improvement. METHODS Respiratory function traces of preterm infants resuscitated at birth were analysed. Ten capnograms were constructed for each infant: five pre- and post-surfactant. If a plateau was present SIII was calculated by regression analysis. RESULTS Thirty-six infants were included, median gestational age of 28.7 weeks and birth weight of 1055 g. Average time between pre- and post-surfactant was 3.2 min. Three hundred and sixty capnograms (180 pre and post) were evaluated. There was adequate slope in 134 (74.4%) capnograms pre and in 100 (55.6%) capnograms post-surfactant (p = 0.004). Normalised for tidal volume SIII pre-surfactant was 18.89 mmHg and post-surfactant was 24.86 mmHg (p = 0.006). An increase in SIII produced an up-slanting appearance to the plateau indicating regional obstruction. CONCLUSION It was feasible to evaluate the alveolar plateau pre-surfactant in preterm infants. Ventilation inhomogeneity increased post-surfactant likely due to airway obstruction caused by liquid surfactant present in the airways. IMPACT Volumetric capnography can be used to assess homogeneity of ventilation by SIII analysis. Ventilation inhomogeneity increased immediately post-surfactant administration during the resuscitation of preterm infants, producing a characteristic up-slanting appearance to the alveolar plateau. The best determinant of alveolar plateau presence in preterm infants was the expired tidal volume.
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Abstract
Mechanical ventilation can be life-saving for the premature infant, but is often injurious to immature and underdeveloped lungs. Lung injury is caused by atelectrauma, oxygen toxicity, and volutrauma. Lung protection must include appropriate lung recruitment starting in the delivery suite and throughout mechanical ventilation. Strategies include open lung ventilation, positive end-expiratory pressure, and volume-targeted ventilation. Respiratory function monitoring, such as capnography and ventilator graphics, provides clinicians with continuous real-time information and an adjunct to optimize lung-protective ventilatory strategies. Further research is needed to assess which lung-protective strategies result in a decrease in long-term respiratory morbidity.
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Williams E, Dassios T, Greenough A. Carbon dioxide monitoring in the newborn infant. Pediatr Pulmonol 2021; 56:3148-3156. [PMID: 34365738 DOI: 10.1002/ppul.25605] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 11/06/2022]
Abstract
Carbon dioxide (CO2 ) monitoring is vital during mechanical ventilation of newborn infants, as morbidity increases when CO2 levels are inappropriate. Our aim was to review the uses and limitations of such noninvasive monitoring methods. Colorimetry is primarily utilized during resuscitation to determine whether successful intubation has occurred. False negative and positive results can however lead to delays in detecting tracheal versus esophageal intubation. Transcutaneous carbon dioxide sensors have limited use during resuscitation, but can be utilized to provide continuous trend data during on-going ventilation. End-tidal capnography can provide clinicians with quantitative end-tidal CO2 (EtCO2 ) values and a continuous real-time capnogram waveform trace. These devices are becoming more widely accepted for use in the neonatal population as the new devices are lightweight with minimal additional dead space. Nevertheless, they have been reported to have variable accuracy when compared to arterial CO2 measurements, however, divergence of results may be related to disease severity rather than technological limitations. During resuscitation EtCO2 can be detected by capnography more rapidly than by colorimetry. Furthermore, capnography can be currently utilized in neonatal research settings to determine the physiological dead space and ventilation inhomogeneity, and thus has potential to be beneficial to clinical care. In conclusion, novel modes of noninvasive carbon dioxide monitoring can be safely and reliably utilized in newborn infants during mechanical ventilation. Future randomized trials should aim to address which device provides the most optimal form of monitoring in different clinical contexts.
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Affiliation(s)
- Emma Williams
- Department of Woman and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Theodore Dassios
- Department of Woman and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.,Neonatal Intensive Care Centre, King's College Hospital NHS Foundation Trust, London, UK
| | - Anne Greenough
- Department of Woman and Children's Health, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.,Asthma UK Centre for Allergic Mechanisms in Asthma, King's College London, London, UK.,National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, UK
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