This study investigated the changes in partial pressure of oxygen during surgical removal of wisdom teeth utilizing a spontaneous ventilation general anesthesia technique with enflurane. Simultaneous transcutaneous and arterial blood gas determination confirmed the presence of two oxygen patterns. Normal preoperative pulmonary function tests, coupled with the stability of the Paco2 between surgery and extubation, indicates that the 23±10 mmHg increase in transcutaneous oxygen (Ptco2) reported in 14 of 27 patients evaluated, was due to ventilation perfusion defects, since 13 of the 27 patients showed a 149±22 mmHg increase in Ptco2 during the same time period.
Respiratory resistance (Rrs6), transcutaneous oxygen tension (PtcO2), and oxygen saturation (SaO2) were measured during methacholine challenge in 15 asthmatic children and six normal adults. During bronchoconstriction, induced by a wide range of inhaled methacholine concentrations (0.5-256 g/l), the rise in Rrs6 was reflected by a fall in PtcO2 in all subjects. Although there was a significant mean fall in SaO2 at maximum bronchoconstriction there was no consistent relation between changes in SaO2 and Rrs6. The inhaled dose of methacholine causing a 40% increase in Rrs6 (PD40Rrs6) and a 20% fall in PtCO2 (PD20PtcO2) was calculated for each subject. There was no significant difference in mean PD40Rrs6 and PD20PtcO2, and the relation between the two was similar in the asthmatic children and the normal adults. It was therefore concluded that the measurement of PtcO2, but not SaO2, during methacholine challenge can be used for the assessment of bronchial responsiveness, and that it could prove particularly useful for children too young to cooperate with lung function tests.
PCO2 and PO2 are important monitoring parameters in neonatal intensive care units (NICU). Compared to conventional blood gas measurements that cause significant blood loss in preterms, transcutaneous (tc) measurements allow continuous, non-invasive monitoring of blood gas levels. The aim of the study was to survey the usage and opinions among German speaking NICUs concerning tc blood gas monitoring.
A questionnaire was developed and sent to 56 head nurses of different NICUs in Germany, Switzerland and Austria.
A completely answered questionnaire was obtained from 41 NICUs. In two of these units tc measurements are not performed. In most NICUs (77%), both PtcO2 and PtcCO2 are measured simultaneously. Most units change the sensors every 3 hours; however, the recommended temperature of 44°C is used in only 15% of units. In only 8% of units are arterial blood gases obtained to validate tc values. Large variations were found concerning the targeted level of oxygen saturation [median upper limit: 95% (range 80–100%); median lower limit: 86% (range 75–93%)] and PO2 [median upper limit: 70 mmHg (range 45–90 mmHg); median lower limit: 44 mmHg (range 30–60 mmHg)].
Our survey shows that the use of tc monitors remains widespread among German speaking NICUs, despite earlier data suggesting that their use had been abandoned in many NICUs worldwide. In addition, we suggest that the current method of monitoring oxygenation may not prevent hyperoxemia in preterm infants.
To determine whether high concentration oxygen increases the PaCO2 in the treatment of community-acquired pneumonia.
Randomized controlled clinical trial in which patients received high concentration oxygen (8 L/min via medium concentration mask) or titrated oxygen (to achieve oxygen saturations between 93 and 95%) for 60 minutes. Transcutaneous CO2 (PtCO2) was measured at 0, 20, 40 and 60 minutes.
The Emergency Departments at Wellington, Hutt and Kenepuru Hospitals.
150 patients with suspected community-acquired pneumonia presenting to the Emergency Department. Patients with chronic obstructive pulmonary disease (COPD) or disorders associated with hypercapnic respiratory failure were excluded.
Main outcome variables
The primary outcome variable was the proportion of patients with a rise in PtCO2 ≥4 mmHg at 60 minutes. Secondary outcome variables included the proportion of patients with a rise in PtCO2 ≥8 mmHg at 60 minutes.
The proportion of patients with a rise in PtCO2 ≥4 mmHg at 60 minutes was greater in the high concentration oxygen group, 36/72 (50.0%) vs 11/75 (14.7%), relative risk (RR) 3.4 (95% CI 1.9 to 6.2), P < 0.001. The high concentration group had a greater proportion of patients with a rise in PtCO2 ≥8 mmHg, 11/72 (15.3%) vs 2/75 (2.7%), RR 5.7 (95% CI 1.3 to 25.0), P = 0.007. Amongst the 74 patients with radiological confirmation of pneumonia, the high concentration group had a greater proportion with a rise in PtCO2 ≥4 mmHg, 20/35 (57.1%) vs 5/39 (12.8%), RR 4.5 (95% CI 1.9 to 10.6) P < 0.001.
We conclude that high concentration oxygen therapy increases the PtCO2 in patients presenting with suspected community-acquired pneumonia. This suggests that the potential increase in PaCO2 with high concentration oxygen therapy is not limited to COPD, but may also occur in other respiratory disorders with abnormal gas exchange.
Arterial oxygen saturation (SaO2) and partial arterial pressure of carbon dioxide (PaCO2) are important respiratory parameters in critically ill neonates. A sensor combining a pulse oximeter with the Stow-Severinghaus electrode, required for the measurement of peripheral oxygen saturation (SpO2) and transcutaneous partial pressure of carbon dioxide (PtcCO2), respectively, has been recently used in neonatal clinical practice (TOSCA500ÒRadiometer). We evaluated TOSCA usability and reliability in the delivery room (DR), throughout three different periods, on term, late-preterm, and preterm neonates. During the first period (period A), 30 healthy term neonates were simultaneously monitored with both TOSCA and a MASIMO pulse oximeter. During the second period (period B), 10 healthy late-preterm neonates were monitored with both TOSCA and a transcutaneous device measuring PtcCO2 (TINAÒ TCM3, Radiometer). During the third period (period C), 15 preterm neonates were monitored with TOSCA and MASIMO after birth, during stabilization, and during transport to the neonatal intensive care unit (NICU). Blood gas analyses were performed to compare transcutaneous and blood gas values. TOSCA resulted easily and safely usable in the DR, allowing reliable noninvasive SaO2 estimation. Since PtcCO2 measurements with TOSCA required at least 10 min to be stable and reliable, this parameter was not useful during the early resuscitation immediately after birth. Moreover, PtcCO2 levels were less precise if compared to the conventional transcutaneous monitoring. However, PtcCO2 measurement by TOSCA was useful as trend-monitoring after stabilization and during transport to NICU.
oxygen saturation; partial pressure of carbon dioxide; pulse oximeter; delivery room; TOSCA sensor; neonate
Fifty children with at least one hospital admission for acute lower airway obstruction in the first 2.5 years of life were assessed at 3 years of age to determine the relationship between atopy, bronchial responsiveness, and the pattern of their symptoms. Bronchial responsiveness was measured by assessing the effect of inhaled metacholine, using the change in transcutaneous oxygen tension (PtCO2) as an indirect measure of response. Symptom patterns were defined by the number of wheezing episodes associated with colds and the presence or absence of cough or wheeze unrelated to viral infections. Forty per cent of the children were found to be atopic by skin prick test or history. In contrast to the situation found in older children and adults, the non-atopic children had significantly greater bronchial responsiveness (lower mean concentration of methacholine causing a 20% fall in PtCO2, the PC20) than the atopic children and significantly more of them had an onset of respiratory symptoms in the first year of life. Cough and wheeze in the absence of colds was more frequently found in the atopic children as was the use of continuous medication. However, the number of reported acute episodes of wheeze associated with colds was the same in the two groups. The findings of the study suggest that in this hospital based group of children, acute wheeze associated with colds in the first three years of life is independent of the finding of atopy and that bronchial responsiveness in this age group may have a different pathogenesis from that in older subjects.
BACKGROUND: The airway response to bronchial provocation may be evaluated by monitoring the fall in transcutaneous oxygen tension (PtcO2) but the repeatability of this method has not been rigorously assessed. METHODS: To determine the repeatability of this indirect method of assessment, bronchial challenge was performed with methacholine in nine children with stable asthma (age range 6-12 years) and was repeated 24 hours later. The response was determined by the fall both in forced expiratory volume in one second (FEV1) and in PtcO2. A modified tidal inhalation protocol was used in which quadrupling concentrations of methacholine were given, thereby reducing the time taken for the full challenge by almost half. The concentrations of methacholine that provoked a 20% decrease in FEV1 (PC20FEV1) and 15% and 10% falls in PtcO2 (PC15PtcO2, PC10PtcO2) were calculated. RESULTS: Repeatability measures, assessed as the 95% range for a single determination, were +/- 0.96 and +/- 1.12 doubling concentration differences respectively for PC15PtcO2 and PC10PtcO2 and +/- 0.80 for PC20FEV1. CONCLUSION: This challenge method using quadrupling concentrations and an indirect assessment of the response by PtcO2 was sufficiently repeatable for clinical use and compared favourably with repeated challenge assessed by FEV1. The PtcO2 method is simple and effort independent, and should prove particularly useful for measuring bronchial reactivity in young children.
BACKGROUND—The repeatability of lung function
tests and methacholine inhalation tests was evaluated in recurrently
wheezy infants over a one month period using the rapid thoracic
METHODS—Eighty one wheezy, symptom free infants
had pairs of methacholine challenge tests performed one month apart.
Maximal flow at functional residual capacity
(V̇maxFRC) and transcutaneous oxygen tension
(PtcO2) were measured at baseline and after
methacholine inhalation. Provocative doses of methacholine causing a
15% fall in PtcO2
(PD15PtcO2) or a 30% fall in
V̇maxFRC (PD30V̇maxFRC) were determined.
RESULTS—Large changes in V̇maxFRC
were measured from T1 to T2 with a mean
difference between measurements (T2—T1) of 7 (113) ml/s and a 95% range for a single determination for
V̇maxFRC of 160 ml/s. The mean (SD) difference
between pairs of PD30V̇maxFRC measurements was 0.33 (1.89) doubling doses with a 95% range for a single
determination of 2.7 doubling doses. Repeatability of
PD15PtcO2 was similar. A change of
3.7 doubling doses of methacholine measured on successive occasions
represents a significant change.
values are highly variable in wheezy, symptom free infants. Using
either V̇maxFRC or PtcO2 as
the outcome measure for methacholine challenges provided similar
repeatability. A change of more than 3.7 doubling doses of methacholine
is required for clinical significance.
To determine the optimal clinical reading time for the transcutaneous measurement of oxygen saturation (SpO2) and transcutaneous CO2 (TcPCO2) in awake spontaneously breathing individuals, considering the overshoot phenomenon (transient overestimation of arterial PaCO2).
Observational study of 91 (75 men) individuals undergoing forced spirometry, measurement of SpO2 and TcPCO2 with the SenTec monitor every two minutes until minute 20 and arterial blood gas (ABG) analysis. Overshoot severity: (a) mild (0.1–1.9 mm Hg); (b) moderate (2–4.9 mm Hg); (c) severe: (>5 mm Hg). The mean difference was calculated for SpO2 and TcPCO2 and arterial values of PaCO2 and SpO2. The intraclass correlation coefficient (ICC) between monitor readings and blood values was calculated as a measure of agreement.
The mean age was 63.1 ± 11.8 years. Spirometric values: FVC: 75.4 ± 6.2%; FEV1: 72.9 ± 23.9%; FEV1/FVC: 70 ± 15.5%. ABG: PaO2: 82.6 ± 13.2; PaCO2: 39.9.1 ± 4.8 mmHg; SaO2: 95.3 ± 4.4%. Overshoot analysis: overshoot was mild in 33 (36.3%) patients, moderate in 20 (22%) and severe in nine (10%); no overshoot was observed in 29 (31%) patients. The lowest mean differences between arterial blood gas and TcPCO2 was −0.57 mmHg at minute 10, although the highest ICC was obtained at minutes 12 and 14 (>0.8). The overshoot lost its influence after minute 12. For SpO2, measurements were reliable at minute 2.
The optimal clinical reading measurement recommended for the ear lobe TcPCO2 measurement ranges between minute 12 and 14. The SpO2 measurement can be performed at minute 2.
transcutaneous CO2; optimal reading time; overshoot phenomenon
The harmful effect of hypocapnia on the neonatal brain emphasizes the importance of monitoring arterial carbon dioxide tension (PaCO2). Transcutaneous monitoring of carbon dioxide (tcPCO2) reduces the need for arterial blood sampling. Drawbacks are high electrode temperature causing risks of skin burning. The aim was to determine the accuracy and precision of tcPCO2 at reduced electrode temperature.
Forty newborns (GA 24.9-41.7) were included. Two tc-monitors were applied (TCM4, Radiometer, Copenhagen). Arterial blood gas sampling and monitoring of tcPCO2-level at different electrode temperatures was done simultaneously (39°C, 40°C, 41 °C, 42°C, 44°C). Difference of PaCO2-tcPCO2 was expressed as a percentage of the mean.
Mean PaCO2 was 5.8kPa [3,2; 7.9]. Bias (PaCO2 -tcPCO2) increased from 5% at 44°C to 17% at 39°C, but did not differ significantly between 41°C and 40°C. The precision of the tcPCO2 at each temperature ranged from +7-10%. After correction for the temperature-dependent over-reading, we found increasing PaCO2 — tcPCO2 difference with increasing PaCO2, approx. 2% pr. kPa increase of CO2. Only mild transient erythema was observed.
A lower electrode temperature in tcPCO2-monitoring increases systematic overreading of the tc-electrode. However, in very preterm babies, monitoring at 40°C or 41°C is possible provided a bias correction of 12-15% is applied.
Infant: newborn; infant: premature; carbon dioxide; blood gas monitoring; transcutaneous; pulmonary ventilation
To reveal the significance of continuous transcutaneous carbon dioxide (CO2) level monitoring through reviewing cases which showed a discrepancy in CO2 levels between arterial blood gas analysis (ABGA) and continuous transcutaneous blood gas monitoring.
Medical record review was conducted retrospectively of patients with neuromuscular diseases who had started home mechanical ventilation between June 2008 and May 2010. The 89 patients underwent ABGA at the 1st hospital day, and changes to their CO2 level were continuously monitored overnight with a transcutaneous blood gas analysis device. The number of patients who initially appeared to show normal PaCO2 through ABGA, yet displayed hypercapnea through overnight continuous monitoring, was counted.
36 patients (40.45%) presented inconsistent CO2 level results between ABGA and continuous overnight monitoring. The mean CO2 level of the 36 patients using ABGA was 37.23±5.11 mmHg. However, the maximum and mean CO2 levels from the continuous monitoring device were 52.25±6.87 mmHg and 46.16±6.08 mmHg, respectively. From the total monitoring period (357.28±150.12 minutes), CO2 retention over 45 mmHg was detected in 198.97 minutes (55.69%).
Although ABGA only reflects ventilatory status at the puncturing moment, ABGA results are commonly used to monitor ventilatory status in most clinical settings. In order to decide the starting point of home mechanical ventilation in neuromuscular patients, continuous overnight monitoring should be considered to assess latent CO2 retention.
Respiratory failure; Blood gas analysis; Transcutaneous blood gas monitoring; Mechanical ventilation
Arterial blood gas (ABG) analysis is useful in evaluation of the clinical condition of critically ill patients; however, arterial puncture or insertion of an arterial catheter may sometimes be difficult and cause many complications. Arterialized ear lobe blood samples have been described as adequate to gauge gas exchange in acute and chronically ill pediatric patients.
This study evaluates whether pH, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), base excess (BE), and bicarbonate (HCO3) values of arterialized earlobe blood samples could accurately predict their arterial blood gas analogs for adult patients treated by mechanical ventilation in an intensive care unit (ICU).
A prospective descriptive study
Sixty-seven patients who were admitted to ICU and treated with mechanical ventilation were included in this study. Blood samples were drawn simultaneously from the radial artery and arterialized earlobe of each patient.
Regression equations and mean percentage-difference equations were derived to predict arterial pH, PCO2, PO2, BE, and HCO3-values from their earlobe analogs. pH, PCO2, BE, and HCO3 all significantly correlated in ABG and earlobe values. In spite of a highly significant correlation, the limits of agreement between the two methods were wide for PO2. Regression equations for prediction of pH, PCO2, BE, and HCO3- values were: arterial pH (pHa) = 1.81+ 0.76 × earlobe pH (pHe) [r = 0.791, P < 0.001]; PaCO2 = 1.224+ 1.058 × earlobePCO2 (PeCO2) [r = 0.956, P < 0.001]; arterial BE (BEa) = 1.14+ 0.95 × earlobe BE (BEe) [r= 0.894, P < 0.001], and arterial HCO3- (HCO3-a) = 1.41+ earlobe HCO3(HCO3-e) [r = 0.874, P < 0.001]. The predicted ABG values from the mean percentage-difference equations were derived as follows: pHa = pHe × 1.001; PaCO2 = PeCO2 × 0.33; BEa = BEe × 0.57; and HCO3-a = HCO3-e × 1.06.
Arterialized earlobe blood gas can accurately predict the ABG values of pH, PCO2, BE, and HCO3- for patients who do not require regular continuous blood pressure measurements and close monitoring of arterial PO2 measurements.
Arterialized earlobe blood gas; critically illness; mechanical ventilation
Objective: To assess the accuracy of measurements of end tidal carbon dioxide (CO2) during neonatal transport compared with arterial and transcutaneous measurements.
Design: Paired end tidal and transcutaneous CO2 recordings were taken frequently during road transport of 21 ventilated neonates. The first paired CO2 values were compared with an arterial blood gas. The differences between arterial CO2 (PaCO2), transcutaneous CO2 (TcPCO2), and end tidal CO2 (PetCO2) were analysed. The Bland-Altman method was used to assess bias and repeatability.
Results: PetCO2 correlated strongly with PaCO2 and TcPCO2. However, PetCO2 underestimated PaCO2 at a clinically unacceptable level (mean (SD) 1.1 (0.70) kPa) and did not trend reliably over time within individual subjects. The PetCO2 bias was independent of PaCO2 and severity of lung disease.
Conclusions: PetCO2 had an unacceptable under-recording bias. TcPCO2 should currently be considered the preferred method of non-invasive CO2 monitoring for neonatal transport.
The objective of this prospective clinical study was to evaluate the accuracy of pulse oximetry and capnography in healthy and compromised horses during general anesthesia with spontaneous and controlled ventilation. Horses anesthetized in a dorsal recumbency position for arthroscopy (n = 20) or colic surgery (n = 16) were instrumented with an earlobe probe from the pulse oximeter positioned on the tip of the tongue and a sample line inserted at the Y-piece for capnography. The horses were allowed to breathe spontaneously (SV) for the first 20 min after induction, and thereafter ventilation was controlled (IPPV). Arterial blood, for blood gas analysis, was drawn 20 min after induction and 20 min after IPPV was started. Relationships between oxygen saturation as determined by pulse oximetry (SpO2), arterial oxygen saturation (SaO2), arterial carbon dioxide partial pressure (PaCO2), and end tidal carbon dioxide (P(et)CO2), several physiological variables, and the accuracy of pulse oximetry and capnography, were evaluated by Bland–Altman or regression analysis. In the present study, both SpO2 and P(et)CO2 provided a relatively poor indication of SaO2 and PaCO2, respectively, in both healthy and compromised horses, especially during SV. A difference in heart rate obtained by pulse oximetry, ECG, or palpation is significantly correlated with any pulse oximeter inaccuracy. If blood gas analysis is not available, ventilation to P(et)CO2 of 35 to 45 mmHg should maintain the PaCO2 within a normal range. However, especially in compromised horses, it should never substitute blood gas analysis.
Patients undergone mechanical ventilation need rapid and reliable evaluation of their respiratory status. Monitoring of End-tidal carbon dioxide (ETCO2) as a surrogate, noninvasive measurement of arterial carbon dioxide (PaCO2) is one of the methods used for this purpose in intubated patients.
The aim of the present trial was to study the relationship between end-tidal CO2 tensions with PaCO2 measurements in mechanically ventilated patients.
Materials and Methods:
End-tidal carbon dioxide levels were recorded at the time of arterial blood gas sampling. Patients who were undergoing one of the mechanical ventilation methods such as: synchronized mandatory mechanical ventilation (SIMV), continuous positive airway pressure (CPAP) and T-Tube were enrolled in this study. The difference between ETCO2 and PaCO2 was tested with a paired t-test. The correlation of end-tidal carbon dioxide to (ETCO2) CO2 was obtained in all patients.
A total of 219 arterial blood gases were obtained from 87 patients (mean age, 71.7 ± 15.1 years). Statistical analysis demonstrated a good correlation between the mean of ETCO2 and PaCO2 in each of the modes of SIMV, CPAP and T-Tube; SIMV (42.5 ± 17.3 and 45.8 ± 17.1; r = 0.893, P < 0.0001), CPAP (37 ± 9.7 and 39.4 ± 10.1; r = 0.841, P < 0.0001) and T-Tube (36.1 ± 9.9 and 39.4 ± 11; r = 0.923, P < 0.0001), respectively.
End-tidal CO2 measurement provides an accurate estimation of PaCO2 in mechanically ventilated patients. Its use may reduce the need for invasive monitoring and/or repeated arterial blood gas analyses.
Blood Gas Analysis; Carbon Dioxide; Artificial Respiration
BACKGROUND--Techniques for sampling arterialised capillary blood from the finger pulp and the earlobe were first described over two decades ago but, although close agreement between arterial values and earlobe samples has been demonstrated in normal subjects, this technique is not in common usage. METHODS--Forty patients with chronic lung disease and a wide range of arterial blood gas values were studied. Simultaneous earlobe and arterial samples were drawn with the patient at rest and analysed in the same blood gas analyser. The respiratory function laboratory staff in 50 UK hospitals with a respiratory department were telephoned and asked whether the technique was used in their hospital and the reasons, if known, for not adopting it. RESULTS--Earlobe and arterial blood gas tensions agreed closely over a wide range of values of arterial pH, PCO2 (mean difference 0.21, 95% confidence intervals -0.24 to +0.67 kPa) and PO2 (mean difference -0.17, 95% confidence intervals -1.09 to +0.75 kPa), especially at arterial PO2 values lower than 8 kPa. Of 50 UK centres surveyed 18% used the arterialised earlobe technique and 4% had plans to introduce it. Reasons for not using it were lack of knowledge in 64%, no blood gas analyser in 6%, the technique was considered inaccurate in 4%, and insufficient staff in 4%. CONCLUSIONS--Although earlobe blood gas analysis is sufficiently accurate to be reliably substituted for arterial sampling in routine clinical practice, most centres in the UK do not use the technique. The main reasons for this appear to be lack of knowledge of its existence and uncertainty over its accuracy.
Non-enzymatic glycation increases hemoglobin-oxygen affinity and reduces oxygen delivery to tissues by altering the structure and function of hemoglobin.
We investigated whether an elevated blood concentration of glycosylated hemoglobin (HbA1c) could induce falsely high pulse oximeter oxygen saturation (SpO2) in type 2 diabetic patients during mechanical ventilation or oxygen therapy.
Arterial oxygen saturation (SaO2) and partial pressure of oxygen (PO2) were determined with simultaneous monitoring of SpO2 in 261 type 2 diabetic patients during ventilation or oxygen inhalation.
Blood concentration of HbA1c was >7% in 114 patients and ≤ 7% in 147 patients. Both SaO2 (96.2 ± 2.9%, 95% confidence interval [CI] 95.7-96.7% vs. 95.1 ± 2.8%, 95% CI 94.7-95.6%) and SpO2 (98.0 ± 2.6%, 95% CI 97.6-98.5% vs. 95.3 ± 2.8%, 95% CI 94.9-95.8%) were significantly higher in patients with HbA1c >7% than in those with HbA1c ≤ 7% (Data are mean ± SD, all p < 0.01), but PO2 did not significantly differ between the two groups. Bland-Altman analysis demonstrated a significant bias between SpO2 and SaO2 (1.83 ±0.55%, 95% CI 1.73% -1.94%) and limits of agreement (0.76% and 2.92%) in patients with HbA1c >7%. The differences between SpO2 and SaO2 correlated closely with blood HbA1c levels (Pearson’s r = 0.307, p < 0.01).
Elevated blood HbA1c levels lead to an overestimation of SaO2 by SpO2, suggesting that arterial blood gas analysis may be needed for type 2 diabetic patients with poor glycemic control during the treatment of hypoxemia.
Glycohemoglobin A1c; Diabetes mellitus; Arterial blood gas analysis; Pulse oxygen saturation
Stable severe chronic obstructive pulmonary disease (COPD) patients with chronic hypercapnic respiratory failure treated by nocturnal bi-level positive pressure non-invasive ventilation (NIV) may experience severe morning deventilation dyspnea. We hypothesised that in these patients, progressive hyperinflation, resulting from inappropriate ventilator settings, leads to patient–ventilator asynchrony (PVA) with a high rate of unrewarded inspiratory efforts and morning discomfort.
Polysomnography (PSG), diaphragm electromyogram and transcutaneous capnography (PtcCO2) under NIV during two consecutive nights using baseline ventilator settings on the first night, then, during the second night, adjustment of ventilator parameters under PSG with assessment of impact of settings changes on sleep, patient–ventilator synchronisation, morning arterial blood gases and morning dyspnea.
Eight patients (61 ± 8 years, FEV1 30 ± 8% predicted, residual volume 210 ± 30% predicted) were included. In all patients, pressure support was decreased during setting adjustments, as well as tidal volume, while respiratory rate increased without any deleterious effect on nocturnal PtcCO2 or morning PaCO2. PVA index, initially high (40 ± 30%) during the baseline night, decreased significantly after adjusting ventilator settings (p = 0.0009), as well as subjective perception of PVA leaks, and morning dyspnea while quality of sleep improved.
The subgroup of COPD patients treated by home NIV, who present marked deventilation dyspnea and unrewarded efforts may benefit from adjustment of ventilator settings under PSG or polygraphy.
Non-invasive ventilation; COPD; Patient–ventilator asynchrony
BACKGROUND--Accurate and reliable measurement of gas exchange during exercise has traditionally involved arterial cannulation. Non-invasive devices to estimate arterial oxygen (O2) and carbon dioxide (CO2) tensions are now available. A method has been devised and evaluated for measuring gas exchange during exercise with a combined transcutaneous O2 and CO2 electrode. METHODS--Symptom limited exercise tests were carried out in 24 patients reporting effort intolerance and breathlessness. Exercise testing was performed by bicycle ergometry with a specifically designed protocol involving gradual two minute workload increments. Arterial O2 and CO2 tensions were measured at rest and during exercise by direct blood sampling from an indwelling arterial cannula and a combined transcutaneous electrode heated to 45 degrees C. The transcutaneous system was calibrated against values obtained by direct arterial sampling before each test. RESULTS--In all tests the trend of gas exchange measured by the transcutaneous system was true to the trend measured from direct arterial sampling. In the 140 measurements the mean difference between the O2 tensions estimated by direct sampling and the transcutaneous method was 0.08 kPa (0.62 mm Hg, limits of agreement 4.42 and -3.38 mm Hg). The mean difference between the methods for CO2 was 0.02 kPa (0.22 mm Hg, limits of agreement 2.20 and -1.70 mm Hg). There was no morbidity associated with the use of the transcutaneous electrode heated to 45 degrees C. CONCLUSIONS--A combined transcutaneous O2 and CO2 electrode heated to 45 degrees C can be used to provide a reliable estimate of gas exchange during gradual incremental exercise in adults.
Background: Long term non-invasive ventilation (NIV) reduces morbidity and mortality in patients with neuromuscular and chest wall disease with hypercapnic ventilatory failure, but preventive use has not produced benefit in normocapnic patients with Duchenne muscular dystrophy. Individuals with nocturnal hypercapnia but daytime normocapnia were randomised to a control group or nocturnal NIV to examine whether nocturnal hypoventilation is a valid indication for NIV.
Methods: Forty eight patients with congenital neuromuscular or chest wall disease aged 7–51 years and vital capacity <50% predicted underwent overnight respiratory monitoring. Twenty six with daytime normocapnia and nocturnal hypercapnia were randomised to either nocturnal NIV or to a control group without ventilatory support. NIV was started in the control group if patients fulfilled preset safety criteria.
Results: Peak nocturnal transcutaneous carbon dioxide tension (TcCO2) did not differ between the groups, but the mean (SD) percentage of the night during which TcCO2 was >6.5 kPa decreased in the NIV group (–57.7 (26.1)%) but not in controls (–11.75 (46.1)%; p = 0.049, 95% CI –91.5 to –0.35). Mean (SD) arterial oxygen saturation increased in the NIV group (+2.97 (2.57)%) but not in controls (–1.12 (2.02)%; p = 0.024, 95% CI 0.69 to 7.5). Nine of the 10 controls failed non-intervention by fulfilling criteria to initiate NIV after a mean (SD) of 8.3 (7.3) months.
Conclusion: Patients with neuromuscular disease with nocturnal hypoventilation are likely to deteriorate with the development of daytime hypercapnia and/or progressive symptoms within 2 years and may benefit from the introduction of nocturnal NIV before daytime hypercapnia ensues.
Background: Patients with advanced cystic fibrosis can benefit from non-invasive positive pressure ventilation (NPPV) for the treatment of acute decompensation as well as for the management of chronic respiratory failure. This study was undertaken to compare the physiological effects of non-invasive proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilatory pattern, transcutaneous blood gas tensions, and diaphragmatic effort in stable patients with cystic fibrosis and chronic CO2 retention.
Methods: In 12 patients two periods of spontaneous breathing were followed randomly by PSV (12 (3) cm H2O) and PAV (flow assist 4.9 (1.3) cm H2O/l.s, volume assist 18.9 (5.1) cm H2O/l) set for the patient's comfort and administered for 40 minutes with 2 cm H2O continuous positive airway pressure. Ventilatory pattern, transcutaneous blood gas tensions, and surface diaphragmatic electromyography were measured in the last 10 minutes of each application.
Results: On average, both PSV and PAV improved ventilation (+30%), tidal volume (+30%), and transcutaneous CO2 (-7%) while reducing diaphragmatic activity (-30% with PSV, -20% with PAV). Mean inspiratory airway pressure was lower during PAV than during PSV (9.7 (1.9) and 12.9 (2.7) cm H2O, respectively; p<0.05). The mean coefficient of variation of tidal volume was about 20% (range 11–39%) during spontaneous breathing and did not change with either PAV or PSV.
Conclusions: These results show that short term administration of nasal PAV and PSV to patients with stable cystic fibrosis with chronic respiratory insufficiency is well tolerated, improves ventilation and blood gas tensions, and unloads the diaphragm.
Previous studies have suggested that end-tidal CO2 (ET-CO2) may be inaccurate during one-lung ventilation (OLV). This study was performed to compare the accuracy of the noninvasive monitoring of PCO2 using transcutaneous CO2 (TC-CO2) with ET-CO2 in patients undergoing video-assisted thoracoscopic surgery (VATS) during OLV.
Materials and Methods:
In adult patients undergoing thoracoscopic surgical procedures, PCO2 was simultaneously measured with TC-CO2 and ET-CO2 devices and compared with PaCO2.
The cohort for the study included 15 patients ranging in age from 19 to 71 years and in weight from 76 to 126 kg. During TLV, the difference between the TC-CO2 and the PaCO2 was 3.0 ± 1.8 mmHg and the difference between the ET-CO2 and PaCO2 was 6.2 ± 4.7 mmHg (P=0.02). Linear regression analysis of TC-CO2 vs. PaCO2 resulted in an r2 = 0.6280 and a slope = 0.7650 ± 0.1428, while linear regression analysis of ET-CO2 vs. PaCO2 resulted in an r2 = 0.05528 and a slope = 0.1986 ± 0.1883. During OLV, the difference between the TC-CO2 and PaCO2 was 3.5 ± 1.7 mmHg and the ET-CO2 to PaCO2 difference was 9.6 ± 3.6 mmHg (P=0.03 vs. ET-CO2 to PaCO2 difference during TLV; and P<0.0001 vs. TC-CO2 to PaCO2 difference during OLV). In 13 of the 15 patients, the TC-CO2 value was closer to the actual PaCO2 than the ET-CO2 value (P =0.0001). Linear regression analysis of TC-CO2 vs. PaCO2 resulted in an r2 = 0.7827 and a slope = 0.8142 ± 0.0.07965, while linear regression analysis of ET-CO2 vs. PaCO2 resulted in an r2 = 0.2989 and a slope = 0.3026 ± 0.08605.
During OLV, TC-CO2 monitoring provides a better estimate of PaCO2 than ET-CO2 in patients undergoing VATS.
End-tidal CO2; thoracoscopy; transcutaneous CO2
To determine the effectiveness of noninvasive positive pressure ventilation (NIPPV), and the factors predicting failure of NIPPV in acute respiratory failure (ARF) due to chronic obstructive pulmonary disease (COPD) versus other causes of ARF.
Patients and methods
This was a prospective observational study and all patients with ARF requiring NIPPV over a one-and-a-half year period were enrolled in the study. We recorded the etiology of ARF and prospectively collected the data for heart rate, respiratory rate, arterial blood gases (pH, partial pressure of oxygen in the arterial blood [PaO2], partial pressure of carbon dioxide in arterial blood [PaCO2]) at baseline, one and four hours. The patients were further classified into two groups based on the etiology of ARF as COPD–ARF and ARF due to other causes. The primary outcome was the need for endotracheal intubation during the intensive care unit (ICU) stay.
During the study period, 248 patients were admitted in the ICU and of these 63 (25.4%; 24, COPD–ARF, 39, ARF due to other causes; 40 male and 23 female patients; mean [standard deviation] age of 45.7 [16.6] years) patients were initiated on NIPPV. Patients with ARF secondary to COPD were older, had higher APACHE II scores, lower respiratory rates, levels compared to other causes of ARF. After one hour there was lower pH and higher PaCO2 levels with increase a significant decrease in respiratory rate and heart rate and decline in PaCO2 levels in patients successfully managed with NIPPV. However, there was no in pH and PaO2 difference in improvement of clinical and blood gas parameters between the two groups except at one hour which was significantly the rate of decline of pH at one and four hours and PaCO2 faster in the COPD group. NIPPV failures were significantly higher in ARF due to other causes (15/39) than in ARF–COPD (3/24) (p = 0.03). The mean ICU and hospital stay and the hospital mortality were similar in the two groups. In the multivariate logistic regression model (after and adjusting for gender, APACHE II scores and improvement in respiratory rate, pH, PaO2 at one hour) only the etiology of ARF, ie, ARF–COPD, was associated with a decreased PaCO2 risk of NIPPV failure (odds ratio 0.23; 95% confidence interval, 0.58–0.9).
NIPPV is more effective in preventing endotracheal intubation in ARF due to COPD than other causes, and the etiology of ARF is an important predictor of NIPPV failure.
noninvasive ventilation; noninvasive positive pressure ventilation; acute respiratory failure; chronic obstructive pulmonary disease; CPAP; bilevel positive airway pressure; pneumonia; ALI; ARDS
Patients undergoing coronary artery bypass surgery and/or heart valve surgery using a median sternotomy approach coupled with the use of cardiopulmonary bypass often experience pulmonary complications in the postoperative period. These patients are initially monitored in an intensive care unit (ICU) but after discharge from this unit to the ward they may still have compromised pulmonary function. This dysfunction may progress to significant respiratory failure that will cause the patient to return to the ICU. To investigate the severity and incidence of respiratory insufficiency once the patient has been discharged from the ICU to the ward, this study used transcutaneous carbon dioxide monitoring to determine the incidence of unrecognized inadequate ventilation in 39 patients undergoing the current standard of care. The incidence and severity of hypercarbia, hypoxia, and tachycardia in post–cardiac surgery patients during the first 24 hours after ICU discharge were found to be high, with severe episodes of each found in 38%, 79%, and 44% of patients, respectively.
Background: Nocturnal non-invasive ventilation (NIV) is an effective treatment for hypercapnic respiratory failure in patients with restrictive thoracic disease. We hypothesised that NIV may reverse respiratory failure by increasing the ventilatory response to carbon dioxide, reducing inspiratory muscle fatigue, or enhancing pulmonary mechanics.
Methods: Twenty patients with restrictive disease were studied at baseline (D0) and at 5–8 days (D5) and 3 months (3M).
Results: Mean (SD) daytime arterial carbon dioxide tension (PaCO2) was reduced from 7.1 (0.9) kPa to 6.6 (0.8) kPa at D5 and 6.3 (0.9) kPa at 3M (p = 0.004), with the mean (SD) hypercapnic ventilatory response increasing from 2.8 (2.3) l/min/kPa to 3.6 (2.4) l/min/kPa at D5 and 4.3 (3.3) l/min/kPa at 3M (p = 0.044). No increase was observed in measures of inspiratory muscle strength including twitch transdiaphragmatic pressure, nor in lung function or respiratory system compliance.
Conclusions: These findings suggest that increased ventilatory response to carbon dioxide is the principal mechanism underlying the long term improvement in gas exchange following NIV in patients with restrictive thoracic disease. Increases in respiratory muscle strength (sniff oesophageal pressure and sniff nasal pressure) correlated with reductions in the Epworth sleepiness score, possibly indicating an increase in the ability of patients to activate inspiratory muscles rather than an improvement in contractility.