Effect of oral hydration on skin microcirculation in healthy young and midlife and older adults

Clinically undetected underhydration lowers subcutaneous tissue oxygen, impairs healing and increases wound infection. This study examined the effect of supplemental oral hydration on noninvasive measures of skin temperature (T(s)), transcutaneous skin O(2) (PtcO(2)), and CO(2) (PtcCO(2)), and skin blood flow (laser Doppler fluxmetry [Flux]=concentration of moving blood cells [CMBC] x Velocity) in healthy adults. Nineteen Control and 18 Test (Hydrated) subjects participated. Ad libitum fluid intake was allowed before the experiment. Sensors were placed on the chest, lower legs, and feet. Time 1 resting supine T(s), PtcO(2)/PtcCO(2), and Flux/CMBC/Velocity were obtained. Then, the Test group ingested 500 mL of H(2)O. Time 2 measures were obtained 30 minutes later. Data were analyzed using ANOVA. Change in T(s), PtcO(2), PtcCO(2), and Velocity did not differ between groups. Flux increased more in the Test than in the Control group (p<0.01). The Flux change was explained by a CMBC increase (p<0.05). For midlife/older subjects only, the CMBC change was greater in the Test than in the Control group (p<0.01). Flux may be sufficiently sensitive to detect microvascular changes in response to supplemental oral hydration. These data also suggest that subtle levels of hypoperfusion due to underhydration may exist in community-dwelling healthy midlife/older adults in their natural state.

An open-label, multicentre pilot study of bosentan in pulmonary arterial hypertension related to congenital heart disease

BACKGROUND

Bosentan has been shown to be a safe and efficacious treatment for idiopathic pulmonary arterial hypertension (PAH) and PAH associated with connective tissue disease. However, there are limited studies examining the benefits of bosentan in PAH associated with congenital heart disease (CHD).

OBJECTIVE

The aim of the present pilot study was to explore the safety and efficacy of bosentan in patients with PAH associated with CHD.

PATIENTS AND METHODS

In the present study, 11 patients with PAH associated with CHD were enrolled to receive bosentan for a minimum of 16 weeks (62.5 mg twice a day for four weeks; thereafter 125 mg twice a day). Safety was assessed by monitoring adverse events, oxygen saturation, systemic blood pressure, pulse, complete blood count and liver function tests. Efficacy was assessed by the World Health Organization functional class, 6 min walk test (6-MWT), modified Borg dyspnea index, echocardiography and the 36-item short form health survey.

RESULTS

Ten patients completed the 16-week treatment period (one patient withdrew). Bosentan was not associated with a deterioration in resting oxygen saturation (83.0+/-4.6% at week 16 versus 81.9+/-6.1% at baseline; P = 0.402), or a deterioration in post-6-MWT oxygen saturation (70.1+/-10.9% at week 16 versus 68.7+/-15.1% at baseline; P = 0.747). Two patients experienced three serious adverse events. The distance walked in 6 min improved significantly by 28 m (P = 0.005) at week 16 compared with baseline, and the modified Borg dyspnea index also improved at week 16 compared with baseline (P = 0.050). The World Health Organization functional class improved from class III to class II for five of 10 patients (50%). Patients' self-rated quality of life (36-item short form health survey) demonstrated a nonsignificant improvement in each of the eight domains. Obtaining reliable echocardiographic measurements was difficult. Most echocardiographic parameters were only measurable on few patients, and none were measured on all patients, questioning the usefulness of echocardiography as a measuring tool for patients with complex CHD.

CONCLUSION

Bosentan was not associated with worsening of resting oxygen saturation or exercise systemic oxygen saturation, suggesting its potential as a safe treatment option for patients with PAH associated with CHD. Improved 6-MWT and the modified Borg dyspnea index also suggested the possibility of bosentan as an efficacious treatment option for these patients. The results of the present study provide evidence for the need and feasibility of a large randomized, placebo-controlled clinical trial.

Comparison of nasal cannulas and the OxyArm in patients requiring chronic domiciliary oxygen therapy

OBJECTIVES

The present study was designed to compare the performance of a new oxygen delivery device, the OxyArm (OA) (Southmedic Inc, Canada), with a standard nasal cannula (NC) (Salter-Style 1600, Salter Labs, USA) for both oxygen delivery and patient preference in patients on long-term oxygen therapy (LTOT).

DESIGN AND SETTING

Randomized crossover study conducted in an outpatient setting.

PATIENTS AND METHODS

Twenty-five clinically stable LTOT patients were randomly assigned to an oxygen device (NC or OA) sequence. The baseline saturation level was determined, and patients were then treated at oxygen flow rates of 2 L/min, 3 L/min, 4 L/min, 5 L/min, 6 L/min and 7 L/min for 10 min each while at rest. Patients were then crossed over to the second device and the procedure was repeated. Oximetry values were then obtained following a 5 min walk test using the same device sequence. Lastly, the patients were sent home for a four-week home OA trial, after which, they filled out a questionnaire.

RESULTS

This sample of patients was primarily elderly ex-smokers with severe chronic obstructive pulmonary disease on oxygen therapy for the majority of the day. The primary findings were that the OA and NC were equally effective in delivering oxygen to patients and maintaining their oxygen saturation at both rest (P = 0.82) and during a 5 min walk test (P = 0.83). A patient's personal experience and comfort were identified as the most important factors in deciding on an oxygen device. Most patients felt that the OA was most suited for oxygen therapy while at rest.

CONCLUSIONS

The OA proved to be similar to the NC in delivering oxygen and maintaining saturation in patients on LTOT. The OA is one of the few alternatives to using NCs for these patients and, with its current design, appears to be most suited for resting conditions.

Effect of different dialyzer membranes on cutaneous microcirculation during hemodialysis

AIM

Biocompatibility profiles of synthetic membranes may vary. In this prospective crossover study, we examined the effect of various membranes on cutaneous microcirculation during HD.

SUBJECTS AND METHODS

11 HD patients without cardiovascular complications were enrolled in this study. They were dialyzed using three types of membrane in a randomized order: ethylene-vinyl alcohol copolymer (EVAL), vitamin E-bonded cellulose (VE-C) and polysulfone (PS). The transcutaneous oxygen tension (TcPO2) was examined on the dorsum of foot to assess the cutaneous microcirculation. Serum biochemical parameters were also measured.

RESULTS

The TcPO2 as a percentage of the predialysis level decreased from the beginning of HD, and significant differences were observed after 15 min of HD between EVAL and the other 2 membranes (98 +/- 6% (mean +/- SD) for EVAL versus 89 +/- 7% for VE-C (p < 0.01) and 88 +/- 10% for PS (p < 0.01)). Furthermore, there were significant differences at 30 and 60 min between EVAL and PS (30 min: 93 +/- 9% for EVAL versus 85 +/- 7% for PS (p < 0.05); 60 min: 92 +/- 10% for EVAL versus 79 +/- 10% for PS (p < 0.01)). The serum level of thiobarbituric acid reactants (TBARs), a marker of lipid peroxidation, increased significantly at the end of HD relative to that at the beginning of HD when using a PS membrane (from 1.9 +/- 0.5 to 2.1 +/- 0.5 nmol/ml, p < 0.05).

CONCLUSION

Our results indicate that an EVAL membrane is superior to PS and VE-C membranes in terms of its smaller influence on cutaneous microcirculation. The repeated occurrence of microcirculatory disturbance during HD sessions may cause chronic endothelial dysfunction and even cardiovascular complications in HD patients.

High prevalence of proximal claudication among patients with patent aortobifemoral bypasses

BACKGROUND

Proximal (ie, buttock, hip) claudication can result from impaired perfusion in the hypogastric area after aortobifemoral bypass (ABF) despite normal femorodistal blood flow provided by the patent bypass. The proportion of patients that experience proximal claudication after ABF is unknown, and arguments for the vascular origin of symptoms specifically at the proximal level have never been reported.

METHODS

This was a prospective study set in an institutional practice of ambulatory patients referred for a systematic survey of their previous ABF bypass. Among the 131 eligible patients, 10 refused to participate and 16 were unable to walk on a treadmill. The 105 studied patients (94 men, 11 women) were a mean age of 63 +/- 10 years, and the median delay from surgery was 2 years (range, 4 months to 26 years). We used a modified version of the San Diego Claudication Questionnaire administered both at rest before the treadmill study and again after the treadmill test. Transcutaneous oxygen pressure (TcPO2) at the buttock level was used to evaluate blood flow impairment during exercise at the proximal level, with blood flow impairment defined as buttock minus chest TcPO2 decrease in excess of -15 mm Hg.

RESULTS

Thirty patients reported proximal exercise-related pain consistent with vascular criteria by history before exercise. However, 59 patients (56%) reported symptoms compatible with proximal claudication, and TcPO2 values were abnormal on one or both sides in 52. The persistence of at least one (prograde or retrograde) pathway to the hypogastric circulation, determined by review of operative details from the aortobifemoral bypass and angiography, did not significantly decrease the proportion of patients reporting proximal claudication by history (26%) or on treadmill (55%) compared with those with bilateral hypogastric occlusion (33% by history, P = .51 compared with at least one prograde hypogastric pathway and 61% based on treadmill test, P = .65 compared with at least one prograde hypogastric pathway).

CONCLUSION

The present study shows that (1) the proportion of ABF patients with a median bypass age of 2 years that report proximal claudication is high (28%), (2) this proportion is significantly higher when claudication is detected by treadmill exercise tests, (3) a vascular origin (or at least contribution) is likely 88% of the proximal symptoms observed on treadmill, (4) the presence of proximal claudication with associated abnormal TcPO(2) results increases the risk of walking impairment in affected patients, and (5) preservation of at least one internal iliac artery to allow prograde or retrograde flow to the hypogastric vascular bed does not decrease the risk of proximal claudication after ABF surgery. A vascular origin of (or at least contribution to) most of the proximal exercise-related symptoms should always be discussed in patients with patent ABF bypass.

Effects of acupressure on lower limb blood flow for the treatment of peripheral arterial occlusive diseases

PURPOSE

To investigate the effects of acupressure on lower limb blood flow for the treatment of peripheral arterial occlusive diseases (PAOD).

METHODS

From February 2004 to February 2005, 30 patients with stage II PAOD underwent measurements of the lower limb blood flow. Six patients (group A) were assigned as controls without any acupoint stimulation, while 24 (group B) underwent stimulation at acupoints by acupressure. The acupoints Yanglingquan (GB34), Zusanli (ST36), Yinlingquan (SP9), and Sanyinjiao (SP6) of the symptomatic lower limbs were stimulated for 3 min. Transcutaneous oximetry (tcPO2) was used to determine the blood flow of the chest wall, bilateral distal crura, and bilateral dorsa of the foot before and during the stimulations at the acupoints.

RESULTS

Group A showed no significant change in the lower limb blood flow. In group B, the tcPO2 values of chest wall, bilateral distal crura, and the dorsum of foot of the stimulated lower limb increased significantly during acupressure (P < 0.01), whereas no significant change was shown in the dorsum of the foot of the non-stimulated lower limb. Moreover, the blood flow of the lower limbs that had undergone an ipsilateral sympathectomy increased significantly (P < 0.01).

CONCLUSIONS

Acupressure was found to cause significant increases in the lower limb blood flow of stage II PAOD patients. This treatment modality may therefore be effective for improving the symptoms of such patients.

[Hemodynamic steal syndrome in the distal limb segments in patients treated by Ilizarov method]

Complex physiological examination of 149 patients with lower limb bone defects was performed using Doppler ultrasonography, rheovasography, percutaneous measurement of oxygen and carbon dioxide during treatment with Ilizarov apparatus. Within the process of treatment with Ilizarov apparatus, with marked collateral circulation, steal syndrome is noted in the distal parts of limb due to the effect of "functional shunting" in the zone of distraction regenerate bone. Steal syndrome during treatment by Ilizarov technique is registered, according to rheovasography and Doppler data, in 57% of patients with a defect in the femoral bone, in 24% of patients with post-traumatic defects in shin bones, and in 85% of patients with congenital defects in shin bones. In the compensated form of steal syndrome in the distal segment, according to polarography data, normoxia combined with hypocapnia is registered; oxygen requirements at rest are met by its more complete utilization, and activation of anaerobic processes.

Effect of silver-threads-containing compression stockings on the cutaneous microcirculation: a double-blind, randomized cross-over study

Recently silver fiber-containing compression stockings for the use in patients with chronic venous insufficiency (CVI) were introduced to the market. In order to gain some first insight into the effects of these new fabrics on the cutaneous microcirculation, a double-blind, randomized cross-over trial was performed in 10 healthy volunteers. A 3 days run-in phase preceded the (2 x10 days) treatment phases and was used to assess the reproducibility of the primary endpoint, which was the transcutaneous partial oxygen pressure (tcpO(2)) measured at a probe temperature of 44 degrees C in the perimalleolar region of the reference leg in supine and dependent leg positions. Coefficients of variation for double measured tcpO(2) values were 4.2% (3.1 SD) and 5.8% (6.0 SD) for the leg in supine and dependent position. The intra-individual comparison of the effects from both treatment phases (value end of treatment - start of treatment) resulted in a negative tcpO(2) net balance for the regular hosiery (-0.93 (2.7 SD) mmHg, supine; -1.1 (3.5 SD) mmHg, dependent) but a positive net balance for the silver fibers containing stockings (0.25 (4.0 SD) mmHg, supine; 1.7 (3.9 SD) mmHg, dependent). The inter-treatment differences were statistically significant for the leg in a dependent position. The trial provides first evidence that interweaving silver threads into regular compression stockings may result in a positive effect regarding the nutritive skin perfusion.

Laparoscopic surgery impairs tissue oxygen tension more than open surgery

Background

Wound infection remains a common and serious complication after colonic surgery. Although many colonic operations are performed laparoscopically, it remains unclear whether this has any impact on the incidence of wound infection. Subcutaneous tissue oxygenation is an excellent predictor of surgical wound infection. The impact of open and laparoscopic colonic surgery on tissue oxygenation was compared.

Methods

Fifty-two patients undergoing elective open and laparoscopic left-sided colonic resections were evaluated in a prospective observational study. Anaesthesia management was standardized and intraoperative arterial partial pressure of oxygen was kept at 150 mmHg in both groups. Oxygen tension was measured in the subcutaneous tissue of the right upper arm.

Results

At the start of surgery subcutaneous tissue oxygen tension (Psqo2) was similar in both groups (mean(s.d.) 65·8(17·2) and 63·7(23·6) mmHg for open and laparoscopic operations respectively; P = 0·714). Tissue oxygen remained stable in the open group, but dropped significantly in the laparoscopic group during the course of surgery (Psqo2 after operation 53·4(12·9) and 45·5(11·6) mmHg, respectively; P = 0·012).

Conclusion

Laparoscopic colonic surgery significantly decreases Psqo2, an effect that occurs early in the course of surgery. As tissue oxygen tension is a predictor of wound infection, these results may explain why the risk of wound infection after laparoscopic surgery remains higher than expected.

Hemodynamic Patterns of Blunt and Penetrating Injuries

BACKGROUND

The aims of this prospective observational study were to describe early hemodynamic patterns of blunt and penetrating truncal injury and to evaluate outcomes prediction using noninvasive hemodynamic monitoring with a mathematical model tested against actual in-hospital outcomes. The hypothesis was that traumatic shock is a circulatory disorder that can be monitored by noninvasive hemodynamic parameters that reflect cardiac, pulmonary, and tissue perfusion functions.

STUDY DESIGN

The cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SapO(2)), transcutaneous oxygen tension indexed to FiO(2) (PtcO(2)/FiO(2)), and carbon dioxide (PtcCO(2)) tensions were monitored beginning shortly after emergency department admission in 657 emergency patients with severe blunt and penetrating chest, abdominal, and extremity trauma. Of these, 113 patients had associated head injury, and these patients also were analyzed separately. A search and display mathematical model, with a decision support program, was based on continuous online, real-time, noninvasive hemodynamic monitoring.

RESULTS

There were similar patterns in the blunt and penetrating injuries; the cardiac index, mean arterial pressure, pulse oximetry, transcutaneous oxygen tension indexed to FiO(2), and survival probability values of the survivors were significantly higher (p < 0.01) than the corresponding values of those who died, although heart rate and carbon dioxide tension were higher in the nonsurvivors during the first 24 hours after their emergency department admission. These patterns occurred more rapidly in patients with penetrating injuries. After initial resuscitation in the emergency department, results were correlated with actual outcomes at hospital discharge and found to be 88% correct.

CONCLUSIONS

Early noninvasive hemodynamic monitoring with a computerized information system provided a feasible pattern recognition program for outcomes prediction and therapeutic decision support.

Steal in Hemodialysis Patients Depends on Type of Vascular Access

OBJECTIVES

To study incidence and severity of steal phenomena in hemodialysis patients and to investigate possible methods for its detection.

METHODS

A questionnaire was composed based on a literature search. A subgroup of patients having steal as identified by the questionnaire was studied using physical examination, arterial blood pressure, skin temperature, digital oxygenation, grip strength and plethysmography. Contralateral arms served as controls.

RESULTS

A cold hand was present in 50% of the patients with a brachiocephalic (BC) arteriovenous fistula (AVF, n = 28) compared to 25% of prosthetic forearm loops (loop, n = 27) and 12% of the radiocephalic (RC, n = 65, p < 0.05) fistulas. Diabetics were at risk for steal (p < 0.001). Intensity of steal was not related to magnitude of access flow. Digital skin temperatures and grip strength were lower in steal hands (p < 0.02). Manual compression of the AVF normalised low digital pressures in steal hands (106 +/- 33 vs 154 +/- 25 mmHg, p < 0.001, contralateral side 155 +/- 21 mmHg).

CONCLUSIONS

Mild to moderate steal symptoms are common in a hemodialysis patient. Individuals with a BC are at a higher risk for developing complaints associated with reduced hand circulation compared to patients with a RC or loop. Low finger pressures in the presence of steal symptoms are usually reversible.

Exercise responses following heart transplantation: 5 year follow-up

Heart transplantation is an established treatment for end stage heart failure. In addition to increased life expectancy, heart transplant recipients report a remarkable improvement in symptoms and functional capacity. Exercise performance following heart transplantation, however, remains impaired even in the absence of exertional symptoms. We have assessed the response to exercise in 47 patients with cardiac failure prior to and then at yearly intervals to five years post transplantation. All patients performed incremental symptom limited exercise tests during which minute ventilation (V'E), oxygen consumption (V'O2) and carbon dioxide production (V'CO2) and heart rate (HR) were measured. Ventilatory response (V'E/V'CO2), anaerobic threshold (V'O2 AT %predicted) and heart rate response (HR/VO2) were calculated. The dead space to tidal volume ratio (VD/VT) and alveolar-arterial oxygen gradient (A-aO2) were computed from transcutaneous monitoring. Despite substantial improvement in subjective functional capacity, heart transplant recipients continue to have limited exercise performance [Maximal V'O2% predicted pre-transplant 41.3 (2.2); 1 year 48.6 (1.7), p <0.001: V'O2 AT% 31.5 (1.1); 1 year 35.6 (1.0); respectively p<0.05]. The maximal oxygen uptake continued to improve at two years post-transplant but, thereafter, there was no further significant change at up to 5 years post transplant [50.9 (1.5)]. At one year post-transplantation peak HR [65.2 (0.9) vs 79.1(1.4)] and the HR/VO2 response [24.0(1.8) vs 79.6(4.2)] were significantly reduced compared to pre-transplant values. The heart rate response remained lower compared to predicted at 5 years post-transplant although there was a significant increase compared to one year post-transplant (32.9 vs 24.0mls/bt). There was a weak but significant relationship between maximal VO2 and peak HR (0.39, p<0.05) and HR/VO2 (r= 0.37, p<0.05) at one year post-transplant. Prior to transplantation the ventilatory response to exercise was elevated [V'E/V'CO2 45.6 (2.5)] and decreased significantly following transplantation [1 yr 34.1 (1.3), respectively p<0.001]. In addition, despite significant improvement in VD/VT after transplantation, it remained higher than normal [Pre VD/VT at maximum exercise 0.35 (0.02); 1 yr 0.31 (0.02); p<0.05]. There was a further fall in the VE/VCO2 and VD/VT at two years post-transplantation with no further change at up to 5 years post transplantation [VE/VCO2 32.0 (1.0); VD/VT 0.29 (0.01)]. Although cardiac output is markedly improved after transplantation, due to chronotropic incompetence associated with denervation, its response remains subnormal and this may explain the residual abnormalities of ventilatory and gas exchange responses to exercise following transplantation.

Calf Muscles Imaged at BOLD MR: Correlation with TcPo2and Flowmetry Measurements during Ischemia and Reactive Hyperemia—Initial Experience

PURPOSE

To prospectively compare the blood oxygen level-dependent (BOLD) magnetic resonance (MR) signal intensity of calf muscle during ischemia and reactive hyperemia with laser Doppler flowmetry (LDF) and transcutaneous oxygen pressure (TcPo2) measurements, two parameters routinely used to evaluate peripheral arterial occlusive disease.

MATERIALS AND METHODS

The study was institutional review board approved; all volunteers gave informed consent. Fifteen healthy volunteers (eight male, seven female; mean age, 33.0 years +/- 6.1 [standard deviation]) underwent LDF, TcPo2 measurement, and BOLD MR imaging of the calf during ischemia and reactive hyperemia. The BOLD signal intensity of the gastrocnemius muscle was measured at 1.5-T single-shot multiecho gradient-echo echo-planar imaging. Time to half ischemia minimum (THIM), time to half hyperemia peak (THHP), and time to peak (TTP) after cuff deflation were measured with each method. Correlation coefficients (CCs) for associations of BOLD response with LDF and TcPo2 time courses were calculated. Student t testing of key BOLD MR, LDF, and TcPo2 measurement parameters was performed.

RESULTS

During ischemia, normalized LDF and TcPo2 measurements decreased similarly to BOLD MR signal intensity (CCs: 0.86 and 0.96 for associations with LDF and TcPo2 measurements, respectively). Mean THIM values were 136.0, 82.5, and 121.3 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P > .05) measurements, respectively. During early reactive hyperemia, LDF and TcPo2 measurements increased rapidly to peak values, similarly to BOLD MR signal intensity (CCs: 0.81 and 0.78, respectively). Mean THHP values were 26.0, 12.5, and 44.0 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P < .01) measurements, respectively. Mean TTP values were 48.7, 47.5, and 98.0 seconds for BOLD MR, LDF (P > .05), and TcPo2 (P < .01) measurements, respectively.

CONCLUSION

BOLD MR imaging of calf muscles-depending on underlying key parameters-has moderate to good correlation with LDF and TcPo2 measurements during ischemia and reactive hyperemia.

Transcutaneous monitoring of partial pressure of carbon dioxide in the elderly patient: a prospective, clinical comparison with end-tidal monitoring

STUDY OBJECTIVE

To evaluate the accuracy and precision of estimation of partial pressure of carbon dioxide (Pa(CO2)) using end-tidal or transcutaneous CO2 (TcP(CO2)) measurements during mechanical ventilation in the elderly patient.

DESIGN

A prospective, observational study was conducted.

SETTINGS

The study was done in the anesthesia department of a university hospital.

PATIENTS

Seventeen anesthetized, mechanically ventilated patients older than 60 years were studied.

INTERVENTIONS AND MEASUREMENTS

During standard sevoflurane anesthesia, and after proper calibration and an equilibration time of 30 minutes with stable hemodynamic and respiratory variables, arterial (Pa(CO2)), end-tidal (Pet(CO2)), and transcutaneous (TcP(CO2)) CO2 partial pressures were determined. In each patient, 1 to 5 sample sets (Pa(CO2), Pet(CO2), and TcP(CO2)) were obtained.

MAIN RESULTS

A total of 45 sample sets were obtained from the patients studied. The Pa(CO2) values ranged between 21 and 58 mm Hg. The Pa(CO2) - Pet(CO2) tension gradient was 6 +/- 5 mmHg (95% confidence interval, -3 to 16 mmHg), whereas the Pa(CO2) - TcP(CO2) tension gradient was 2 +/- 4 mmHg (95% confidence interval, -6 to 9 mmHg) (P = 0.0005). The absolute value of the difference between Pa(CO2) and Pet(CO2) was 3 mm Hg or less in 7 of 45 sample sets (15%), whereas the absolute value of the difference between Pa(CO2) and TcP(CO2) was 3 mm Hg or less in 21 of 45 sample sets (46%) (P = 0.003). Linear regression analysis for TcP(CO2) versus Pa(CO2) showed a slope of 0.84 (r(2) = 0.73), whereas the linear regression analysis for Pet(CO2) versus Pa(CO2) showed a slope of 0.54 (r(2) = 0.50).

CONCLUSION

Transcutaneous monitoring of CO(2) partial pressure gives a more accurate estimation of arterial CO(2) partial pressure than does Pet(CO2) monitoring.

[Usefulness of transcutaneous carbon dioxide pressure monitoring to measure blood gases in adults hospitalized for respiratory disease]

OBJECTIVE

To evaluate the usefulness of transcutaneous carbon dioxide pressure (TcPCO2) monitoring in patients hospitalized for respiratory disease.

PATIENTS AND METHODS

We used a SenTec TcPCO2 monitor that also determines transcutaneous oxygen saturation (SpO2) by means of a sensor placed behind the ear lobe at a temperature of 42 degrees C. We compared arterial blood gas measurements--PaCO2 and arterial oxygen saturation (SaO2)--with transcutaneous measurements and analyzed the correlation, regression line, and agreement between the 2 methods.

RESULTS

Thirty patients (20 men and 10 women) with various respiratory diseases and a mean (SD) age of 71 (13) years were included in the study. The median TcPCO2 was 43.25 mm Hg and the median PaCO2 was 42.6 mm Hg with no significant differences between the 2 measurements. The correlation was significant (rho=0.979; P< .0001) and the corresponding regression equation was TcPCO2=-2.475+1.058 PaCO2. The mean difference was 0.16 mm Hg (95% confidence interval [CI], --0.74 to 1.06). The lower limit of agreement (mean -1.96 SD) was -4.64 mm Hg, and the upper limit (mean +1.96 SD) was 4.96 mm Hg. For SaO2, the median was 94% and for SpO2, 95%. The difference between the 2 medians was significant (P< .004). The correlation was also significant (rho=0.822; P< .0001) with SpO2=4.427+0.97 SaO2. The mean difference was 1.14% (95% CI, 0.381% to 1.899%). The lower limit of agreement (mean -1.96 SD) was --2.93% and the upper limit (mean +1.96 SD) was 5.21%

CONCLUSIONS

Transcutaneous determination of carbon dioxide pressure and oxygen saturation is useful for patients hospitalized for respiratory disease in view of its good correlation and agreement, although SpO2 does tend to overestimate SaO2.

Airway hyper-responsiveness to adenosine 5'-monophosphate in preschool-age children with asthma

Airway hyper-responsiveness (AHR) to adenosine 5'-monophosphate (AMP) is closely associated with airway inflammation; however, not all asthmatic patients are responsive to it. This study was planned to investigate the predictive factors of AHR to AMP in asthmatic children aged between 3 and 6 yr. We performed a retrospective analysis of data from 63 asthmatic preschool-age children who were challenged by AMP in our department. All children were characterized by skin-prick tests, serum immunoglobulin E (IgE) levels, peripheral blood eosinophil percentage and bronchial challenge with methacholine (MCH) and AMP. Potential determinants for AHR to AMP were assessed within the group. AHR to AMP was found in 46% of preschool-age children with asthma, while that of MCH was 93.7%. All children responsive to AMP were also responsive to MCH. The geometric mean provocative concentration of MCH and AMP causing a 15% fall in transcutaneous oxygen tension (PC(15)PtcO(2)MCH and AMP) were 0.55 mg/ml (0.004-9.19) and 10.53 mg/ml (0.59-342.89), respectively. AMP-responsive children did not differ from non-responsive ones with respect to demographic factors, geometric mean PC(15)PtcO(2)MCH and atopic status. The median serum IgE level was significantly higher in AMP-responsive group than the non-responsive ones (p = 0.011). The peripheral blood eosinophilia was more frequent among responsive children (p = 0.019), and it was found as the only predictive factor for AMP responsiveness in preschool-age children with asthma in logistic regression model (odds ratio: 5.14; 95% CI: 1.23-21.47; p = 0.025). AMP responsiveness may be predicted by peripheral blood eosinophilia but not with atopy markers in young children with asthma.

Noninvasive Hemodynamic Monitoring for Combat Casualties

The aims of this study were to develop and to test a noninvasive hemodynamic monitoring system that could be applied to combat casualties to supplement conventional vital signs, to use an advanced information system to predict outcomes, and to evaluate the relative effectiveness of various therapies with instant feedback information during acute emergency conditions. In a university-run inner city public hospital, we evaluated 1,000 consecutively monitored trauma patients in the initial resuscitation period, beginning shortly after admission to the emergency department. In addition to conventional vital signs, we used noninvasive monitoring devices (cardiac index by bioimpedance with blood pressure and heart rate to measure cardiac function, arterial hemoglobin oxygen saturation by pulse oximetry to reflect changes in pulmonary function, and tissue oxygenation by transcutaneous oxygen tension indexed to fractional inspired oxygen concentration and carbon dioxide tension to evaluate tissue perfusion). The cardiac index, mean arterial pressure, pulse oximetry (arterial hemoglobin oxygen saturation), and transcutaneous oxygen tension/fractional inspired oxygen concentration were significantly higher in survivors, whereas the heart rate and carbon dioxide tension were higher in nonsurvivors. The calculated survival probability was a useful outcome predictor that also served as a measure of severity of illness. The rate of misclassification of survival probability was 13.5% in the series as a whole but only 6% for patients without severe head injuries and brain death. Application of noninvasive hemodynamic monitoring to acute emergency trauma patients in the emergency department is feasible, safe, and inexpensive and provides accurate hemodynamic patterns in continuous, on-line, real-time, graphical displays of the status of cardiac, pulmonary, and tissue perfusion functions. Combined with an information system, this approach provided an early outcome predictor and evaluated, with an objective individualized method, the relative efficacy of alternative therapies for specific patients.

Pneumocystis jiroveci pneumonia in a patient with rheumatoid arthritis as a complication of treatment with infliximab, anti-tumor necrosis factor alpha neutralizing antibody

We report that a-63-year-old woman developed Pneumocystis jiroveci pneumonia (PCP) as a complication from treatment with infliximab for rheumatoid arthritis. Although there was neither symptoms of dyspnea nor typical observations on a chest X-ray examination, low levels of oxygen saturation and findings of high-resolution chest computed tomographic scanning suggested a possibility of interstitial pneumonia. A polymerase chain reaction-based detection of Pneumocystis jiroveci in induced sputum allowed an early diagnosis of PCP and subsequent effective treatment.

The influence of diabetes and lower limb arterial disease on cutaneous foot perfusion

OBJECTIVE

Peripheral arterial occlusive disease and peripheral neuropathy are major risk factors in diabetic foot disease. We evaluated the relative influences of noncritical lower limb arterial disease and peripheral neuropathy on cutaneous foot perfusion in diabetes.

METHOD

Toe-brachial pressure indices, transcutaneous oxygen, and carbon dioxide tensions at foot and chest sites were measured in individuals with diabetes, with or without detectable peripheral neuropathy and with or without significant arterial disease on color duplex imaging. Subjects without diabetes, with and without arterial disease, were used as controls.

RESULTS

A total of 130 limbs were studied during an 8-month period. Toe-brachial pressure indices reflected the presence of arterial disease in all groups. Foot transcutaneous oxygen values were reduced in diabetes and correlated with chest transcutaneous oxygen values. Low foot transcutaneous oxygen with elevated transcutaneous carbon dioxide values were only demonstrated in individuals with diabetes, arterial disease, and peripheral neuropathy. Toe-brachial pressure indices demonstrated a positive correlation with foot transcutaneous oxygen values, but values >1.2 demonstrated a negative correlation.

CONCLUSIONS

We demonstrated two influences on cutaneous foot perfusion in diabetes: (1) a global microcirculatory dysfunction, reflected in low chest and foot transcutaneous oxygen values, and (2) macrovascular disease as indicated by reduced toe-brachial pressure indices and foot transcutaneous oxygen values. Further, the results demonstrated that in diabetic individuals without critical limb ischemia, impaired foot perfusion secondary to arterial disease is amplified significantly by coexisting microcirculatory disease.

Rapid diagnosis of cannula migration by cerebral oximetry in neonatal arch repair

Although it has gained much interest in other surgical specialties, the application of near-infrared spectroscopy to assess cerebral perfusion during cardiac surgery is relatively new. Regional cerebral oxygen saturation (rSO2) is a function of cerebral oxygen supply and demand. Continuous monitoring of the rSO2 permits early detection of cerebral ischemia allowing for prompt intervention. The following is a description of a repair of truncus arteriosus with type A interrupted aortic arch during which continuous cerebral oximetry assisted with the positioning of the arterial cannula avoiding a prolonged episode of cerebral ischemia.

Is transcutaneous oxygen and carbon dioxide monitoring indispensable in short- and long-term therapeutic management of non-reconstructable lower critical limb ischemia?

AIM

The aim of this study was to evaluate the capacity of transcutaneous partial pressure of O(2) (TCpO(2)) and CO(2) (TCpCO(2)) to predict clinical response to pharmacological treatment in short- and long-term follow-up of unreconstructable critical limb ischemia (CLI) treated with prostanoids; to suggest a diagnostic and therapeutic algorithm able to define the possibility of prostanoid therapy in unreconstructable CLI at high risk of limb loss.

METHODS

Twenty-six consecutive patients with CLI (21 with distal trophic lesions, 31 symptomatic limbs) considered unreconstructable after peripheral angiography and with a history of type 2 diabetes mellitus underwent daily parenteral Iloprost treatment for 2-3 weeks.

RESULTS

Transcutaneous gas-analytic monitoring (TGM) in non-reconstructable CLI treated with Iloprost divided patients into 2 groups: early responders (ER) with increased TcpO(2) and normalization of TcpCO2, and non responders (NR) with unchanged TcpO(2) and TcpCO(2) parameters. In the NR who underwent a second cycle of Iloprost within a few months of the first, TGM further divided the patients into another subgroup of late responders (LR) with TcpO(2) and TcpCO(2) similar to the ER group and a subgroup of NR, who, after pharmacological treatment failure, should undergo eventual surgical re-timing and/or spinal cord stimulation in a final attempt to save the limb.

CONCLUSIONS

In the short-term follow-up of CLI, a marked reduction in supine/dependent TcpO(2) and a marked increase in supine TcpCO(2) at the symptomatic forefoot proved to be significant predictors of major amputation risk. In the long-term follow-up period, TGM showed that, in ER and in LR, the favourable effect of pharmacological therapy observed in the first 6 months will disappear over the next 6 months, suggesting an algorithm of 2- to 3-week cycles of prostanoid therapy repeated every year. In NR treated with surgical and/or alternative therapies who did not undergo major amputations, prolonged instrumental TGM will provide a constant evaluation of metabolic parameters, thus providing the possibility to save the limb with additional pharmacological therapy.

Ischemic scleroderma wounds successfully treated with hyperbaric oxygen therapy

Hyperbaric oxygen therapy (HBOT) has been used to treat refractory wounds for the last several decades, with the majority of research focusing on wounds secondary to arterial insufficiency. We describe 2 patients with scleroderma with intractable bilateral extremity ulcers. Local ischemia was identified using transcutaneous oximetry. Each patient then underwent 30 treatments of HBOT at a relative depth of 2.4 ATA with resulting wound healing. This is the first reported successful use of HBOT to treat scleroderma ulcers, and may represent an unrecognized treatment option for these notoriously difficult chronic wounds.

Use of a noninvasive pulse CO-oximeter to measure blood carboxyhemoglobin levels in bingo players

BACKGROUND

Though smokers are known to have elevated blood carboxyhemoglobin (COHb), due to inhalation of carbon monoxide (CO) in cigarette smoke, limited data exist regarding COHb levels in nonsmokers exposed to secondhand smoke.

METHODS

COHb was measured using a new noninvasive pulse CO-oximeter (Rad-57, Masimo, Irvine, California) in 38 subjects entering a bingo hall where smoking was allowed, then again as they exited 3 hours later.

RESULTS

The mean +/- SD baseline COHb for the entire group was 3.3 +/- 1.8%, for the 23 nonsmokers it was 2.2 +/- 0.7%, and for the 15 smokers it was 4.9 +/- 1.9%. The nonsmokers' mean COHb was unchanged, at 2.2 +/- 0.8%, whereas the smokers' mean COHb fell to 3.2 +/- 1.9%.

CONCLUSIONS

The nonsmokers were not significantly exposed to CO from secondhand smoke in the setting we tested. The smokers probably consumed fewer cigarettes while playing bingo than they did prior to arrival. The Rad-57 pulse CO-oximeter is easy to use in the ambulatory setting.

Evaluation of bronchial hyperresponsiveness by monitoring of transcutaneous oxygen tension and arterial oxygen saturation during methacholine challenge in asthmatic children

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a key feature of asthma, but the measurement of BHR is hampered by the fact that most tests of airway caliber are difficult to conduct at a young age. Methacholine-induced bronchoconstriction is associated with significant hypoxemia, which can be assessed noninvasively by transcutaneous oxygen pressure (tcPO2) and pulse oximetry. Evaluating BHR by monitoring tcPO2 instead of respiratory resistance (Rrs) has been used over a wide age range in childhood.

OBJECTIVE

To investigate whether there is a consistent relationship between changes in arterial oxygen saturation (SaO2) and respiratory resistance (Rrs) similar to the relationship between tcPO2 and Rrs during methacholine challenge in young children and to assess the usefulness of SaO2 as a parameter for the indirect measurement of BHR.

METHOD

We performed methacholine inhalation challenge by monitoring SaO2, tcPO2 and Rrs in 37 asthmatic children 5 to 7 years of age. Consecutive doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. We recorded the cumulative dose of methacholine (Dmin) at the inflection point of tcPO2 (Dmin-tcPO2), SaO2 (Dmin-SaO2), and Rrs(Dmin-Rrs).

RESULTS

The mean value of Dmin-Rrs was 4.27 +/- 2.02 units, the mean value of Dmin-tcPO2 was 4.48 +/- 2.01 units, and the mean value of Dmin-SaO2 was 4.57 +/- 0.20 units. Inhalation of increasing doses of methacholine raised Rrs curvilinearly and depressed tcPO2 and SaO2. There were no significant differences between any of the parameters. There were significant relationships between Dmin-tcPO2 and Dmin-Rrs (r = 0.914, p < 0.001) and between Dmin-SaO2 and Dmin-Rrs (r = 0.905, p < 0.001) and a relationship between Dmin-tcPO2 and Dmin-SaO2 (r = 0.949, p < 0.001).

CONCLUSION

We concluded that measurement of SaO2 and/or tcPO2 during methacholine inhalation challenge may be used to assess bronchial hyperresponsiveness. This study showed that both SaO2 and tcPO2 monitoring are safe, useful, and tolerable for use in children who are too young to cooperate with lung function tests.

Hemoglobin oxygen saturation as a marker of cerebral hemodynamics in carotid artery occlusion

Cerebral hemodynamics play a pivotal role in stroke pathogenesis. Transcranial Doppler (TCD) studies demonstrated the importance of cerebral vasomotor reactivity (VMR) on the outcome of carotid artery occlusion (CAO). So far, positron emission tomography represents the best technique for detecting both hemodynamic and metabolic aspects of cerebral perfusion adaptive processes in cerebrovascular patients. Near-infrared spectroscopy (NIRS) is a new method allowing for a non-invasive assessment of cerebral blood flow and hemoglobin (Hb) oxygenation parameters.A recent TCD and NIRS study demonstrated that patients with symptomatic CAO had lower VMR values measured by TCD and lower oxygen saturation (oxygen%) increases detected by NIRS than asymptomatic ones. The parameters were obtained simultaneously after CO(2) inhalation. The present study aims to investigate if Hb oxygen % could represent also at rest a marker of hemodynamic status in carotid disease.Thirty-five symptomatic and 17 asymptomatic patients with CAO underwent a simultaneous examination by means of TCD and NIRS at rest condition and during CO(2) reactivity test. Symptomatic patients presented with oxygen% values at rest higher (p = 0.001) and VMR values lower (p < 0.001) than asymptomatic subjects. According to a logistic model, for each unitary VMR increase, the odds of being symptomatic decreases of about 10% (OR = 0.9, p = 0.001); for each unitary increase of oxygen% at baseline, this odd increases of about 23% (OR = 1.23, p = 0.031). In addition to TCD VMR values, oxygen hemoglobin saturation at rest detected by NIRS can discriminate symptomatic from asymptomatic patients with CAO. NIRS can add an important contribution to explain pathophysiological mechanisms of stroke occurrence.

Effects of lifestyle modifications on C-reactive protein: contribution of weight loss and improved aerobic capacity

High-sensitivity C-reactive protein (hs-CRP) is associated with an increased risk of cardiovascular disease and the development of type 2 diabetes mellitus. We analyzed the effects of lifestyle modifications including exercise training on hs-CRP in 47 overweight and obese adults. Subjects were divided into a lifestyle modification group (n=23) (exercise and diet instruction) and a control group (n=24) who did not participate in any lifestyle modification. After 3 months, body weight (80.8+/-11.5 to 73.5+/-10.7 kg, P<.01), total cholesterol (217+/-38.4 to 178.0+/-25.6 mg/dL, P<.01), low-density lipoprotein cholesterol (151.3+/-34.9 to 116.7+/-27.8 mg/dL, P<.01), Vo(2)peak (30.3+/-5.1 to 37.1+/-6.9 mL/[kg . min], P<.01), and log hs-CRP (0.75+/-0.4 to 0.56+/-0.3 mg/dL, P=.01) were significantly improved in the lifestyle modification group, but there was no significant improvement in the control group. Changes in log hs-CRP were associated with changes in Vo(2)peak (r=-0.41, P=.004) and changes in weight loss (r=0.42, P=.004). In stepwise multiple regression analysis, weight loss (P=.034) and improved Vo(2)peak (P=.039) were independent predictors of the changes in hs-CRP. When grouped into quartiles according to decreasing weight and increasing Vo(2)peak, levels of changes in log hs-CRP improved across quartiles of weight loss (P<.05) and improved Vo(2)peak (P<.01). Thus, lifestyle changes including regular exercise training in overweight and obese adults decreased hs-CRP, and this was associated with weight loss and improved Vo(2)peak.

Effects of nitroglycerin on erythrocyte rheology and oxygen unloading: novel role of S-nitrosohemoglobin in relieving myocardial ischemia

BACKGROUND

We hypothesized that nitroglycerin improves O2 delivery to ischemic tissue by altering erythrocyte rheology and O2 unloading through an increase in bioactive nitric oxide (NO) content.

METHODS AND RESULTS

Twelve dogs with resting flow-reducing single-vessel stenosis were studied at rest and during intracoronary infusion of nitroglycerin (0.3 to 0.6 microg.kg(-1).min(-1)). Half the dogs also had occlusion of the remote coronary artery to remove any collateral effects. Systemic and coronary hemodynamics, myocardial blood flow (MBF), whole blood viscosity (WBeta), erythrocyte charge (EC) and mobility (EM), regional myocardial O2 delivery and consumption, and tissue O2 pressure (Po2) were measured. No changes in systemic hemodynamics were seen with nitroglycerin. Despite flow-limiting stenosis, MBF increased significantly in the central 25% of the ischemic bed, which was associated with an approximately 19% decrease in WBeta. There was a good correlation (r=0.87) between the two. The decrease in WBeta was associated with a decrease in EC and an increase in EM (r=0.83). The nitroglycerin-induced increase in tissue Po2 was disproportionate to the increase in MBF, indicating enhanced O2 unloading. Erythrocyte S-nitrosothiol content (reflecting mainly S-nitrosohemoglobin) was significantly higher for blood exposed in vitro to 0.1 micromol/L nitroglycerin or the NO donor SNAP, as compared with control (18.9+/-8.8 and 10.5+/-6.5 versus 2.6+/-0.5x10(-5), P<0.05).

CONCLUSIONS

The augmented MBF in the ischemic microcirculation during nitroglycerin administration occurs in tandem with increased erythrocyte S-nitrosothiol content, EM, and O2 unloading. These additional microvascular mechanisms may contribute to the powerful antiischemic effects of nitroglycerin, especially during low-flow states.

Randomized clinical trial to evaluate the effects of perioperative supplemental oxygen administration on the colorectal anastomosis

Background

Perioperative supplemental oxygen therapy may have beneficial effects on wound healing following colorectal surgery. The aim of this study was to evaluate the effects of such therapy on colorectal anastomotic pH and partial pressure of carbon dioxide (Pco2) gap.

Methods

Forty-five patients undergoing anterior resection for rectal or sigmoid cancer were randomized to receive 30 or 80 per cent perioperative oxygen. Administration was commenced after induction of anaesthesia and maintained for 6 h after surgery. Intragastric and anastomotic tonometric catheters were placed in each patient and intramucosal pH (pHi) was measured immediately after operation, and 6 and 24 h later. Gastric and anastomotic pHi and Pco2 gap in each group were compared.

Results

There was a significantly lower anastomotic pHi and wider Pco2 gap for gastric readings in the 30 per cent O2 group, both 30 min (pHi, P = 0·006; Pco2 gap, P = 0·006) and 6 h (pHi, P = 0·024; Pco2 gap, P = 0·036) after surgery. There were no differences 24 h after surgery while breathing room air (pHi, P = 0·131; Pco2 gap P = 0·139). No difference was found between gastric and anastomotic readings at any time point in the 80 per cent O2 group.

Conclusion

Perioperative administration of 80 per cent O2 both during surgery and for 6 hours afterwards is associated with an improvement in relative anastomotic hypoperfusion as assessed by the measurement of pHi and Pco2 gap.

The effect of haemodialysis on transcutaneous oxygen tension in patients with diabetes—a pilot study

BACKGROUND

Established renal failure in diabetes is associated with a high incidence of foot ulcers and gangrene, and these are major causes of morbidity and mortality. It has been suggested that this problem is particularly associated with the onset of renal replacement therapy, and since there is evidence that haemodialysis causes hypoxaemia, we have undertaken a pilot study to determine the effect of haemodialysis on lower limb transcutaneous oxygen tension (TcpO2).

METHODS

TcpO2 was measured on the dorsum of the foot through a single dialysis treatment and over the succeeding 4 h using a transcutaneous monitor (TCM400/3, Radiometer Ltd, Copenhagen, Denmark).

RESULTS

The median age (range) of the 10 (7 male) participants was 73 (58-83) years. The median duration of diabetes was 16.5 (7-30) years and that of dialysis treatment 29 (10-88) months. The median (range) baseline TcpO2 on the dorsum of the foot was 54.5 (51-77) mmHg and 54.0 (24-87) at the end of dialysis. Median TcpO2 at 1, 2 and 4 h after the end of dialysis was 50.0 (33-81), 49.0 (24-78) and 47.0 (20-78) mmHg. Analysis by ANOVA suggested a trend towards a difference between median TcpO2 concentrations at different time points (F(1.752, 15.765) = 3.359, P = 0.066).

CONCLUSIONS

The data identified a trend towards a fall in lower limb TcpO2, and that this fall continued for at least 4 h after the end of treatment. Dialysis-associated lower limb hypoxia may be a factor leading to the increased incidence of critical limb ischaemia in this group and further work is needed to define its cause and implications for clinical care.

An evaluation of transcutaneous carbon dioxide partial pressure monitoring during apnea testing in brain-dead patients

BACKGROUND

Diagnosis of brain death usually requires an arterial carbon dioxide partial pressure (Paco2) of 60 mmHg during the apnea test, but the increase in Paco2 is unpredictable. The authors evaluated whether transcutaneous carbon dioxide partial pressure (Ptcco2) monitoring during apnea test can predict that a Paco2 of 60 mmHg has been reached.

METHODS

The authors compared Ptcco2 measured with a transcutaneous ear sensor (V-Sign Sensor, Sentec Digital Monitoring System; SENTEC-AG, Therwil, Switzerland) and Paco2 obtained from arterial blood gas measurements in 32 clinically brain-dead patients.

RESULTS

In the first 20 patients, the mean Paco2-Ptcco2 gradient was 0.7 +/- 3.6 mmHg at baseline and 8.7 +/- 7.1 mmHg after 20 min of apnea. Using receiver operating characteristic curve analysis (area under the curve: 0.983 +/- 0.013), the best threshold value of Ptcco2 to predict that a Paco2 of 60 mmHg had been reached was 60 mmHg (positive predictive value: 1.00 [0.93-1.00]). In the following 12 patients investigated with use of this Ptcco2 target value of 60 mmHg, the mean duration of the apnea test (11 +/- 4 vs. 20 +/- 0 min; P < 0.001), hypercapnia (74.0 +/- 4.9 vs. 98.3 +/- 20.0 mmHg; P < 0.001), acidosis (pH: 7.18 +/- 0.06 vs. 7.11 +/- 0.08; P < 0.001), and decrease in arterial oxygen partial pressure (-47 +/- 44 vs. -95 +/- 89; P < 0.05) at the end of the test were reduced as compared with the 20-min apnea test group.

CONCLUSION

During the apnea test in brain-dead patients, a Ptcco2 of 60 mmHg accurately predicts that a Paco2 of 60 mmHg has been reached. This may allow a reduction in the duration of the apnea test and consecutively limit occurrence of complications.

[Experimental study of cerebral protection by retrograde vs selective antegrade cerebral perfusion during deep hypothermic circulatory arrest]

OBJECTIVE

To compare the effect of cerebral protection between retrograde cerebral perfusion (RCP) and selective antegrade cerebral perfusion (SACP) during deep hypothermic circulatory arrest (DHCA) in canine models.

METHODS

Fifteen healthy adult dogs were randomly divided into 3 groups (n=5), namely the simple DHCA group (group I), DHCA+RCP group (group II) and DHCA+SACP group (group III). Extrocorporeal circulatory was established routinely in the dogs, and DHCA commenced when the nasopharyngeal temperature was reduced to 18 degrees C. During DHCA, RCP and SACP were applied in groups II and III, respectively. All the models were rewarmed after 90 min of DHCA and the cerebral reperfusion continued for 90 min. Cerebral oxygenous metabolic function, cerebral temperature and ultrastructural changes of the neurons were observed in the 3 groups at different time points during the operation.

RESULTS

The jugular venous oxygen saturation (SjvO(2)) increased with the temperature reduction, and then decreased after DHCA commencement, showing significant changes at different time points in groups I and II. SjvO(2) in group III were significantly higher than that in the other two groups after 90 min of DHCA (P=0.000). Brain temperature significantly increased in group I during DHCA as compared with that in groups II and III (P=0.000), but showed no significant difference between the latter two groups (P=0.195). The ultrastructure of the neurons underwent obvious changes after reperfusion for 30 min in group I. In group II the neuronal ultrastructure was basically normal at 60 min during DHCA and changed slightly at 90 min, but in group III no obvious changes were seen at 90 min during DHCA and only slight changes occurred at 30 min of reperfusion.

CONCLUSIONS

RCP can not supply enough oxygen but can maintain low cerebral temperature, and provide short-term brain protection. DHCA+SACP provides better brain protection than simple DHCA and DHCA+RCP, and has a promising prospect in cardiac surgery.

Influence of digital clubbing on oxygen saturation measurements by pulse-oximetry in cystic fibrosis patients

OBJECTIVE

To determine the influence of digital clubbing on oxygen saturation by pulse oximetry measurements (SpO2) in Cystic Fibrosis patients.

BACKGROUND

Measuring the arterial oxygen saturation at the fingertip by pulse-oximetry is commonly used in the management of CF patients. In these patients, clinical signs of hyperoxia are often observed with oxygen supplies based on digital oximetry readings. This suggests inaccuracies in the digital measurement method, which in its turn may be caused by digital clubbing. In order to study the influence of digital clubbing, measurements between fingertip and forehead sensor were compared in a clubbing and non-clubbing CF-population. The ear sensor measurements are used as a reference variable.

METHODS

Two groups were examined. Group 1 consisted of 50 CF patients without digital clubbing (DPD/IPD ratio<1.00). Group 2 consisted of 50 CF patients with digital clubbing (DPD/IPD ratio>1.00). Patients were measured at rest before any treatment and with their daily oxygen supply, if applicable. Saturation was simultaneously measured with three Criticare SpO2 T pulse oximeters, using a fingertip sensor at the right index (transmission oximetry), a forehead sensor at the forehead (reflectance oximetry) and an ear sensor at the right ear.

RESULTS

Using the Bland and Altman method no clear difference was found between the saturation measurements of right ear versus forehead sensor in the two groups. When the measurements of right ear versus fingertip sensor are compared there is still no difference for the non-clubbing group. On the contrary, for the clubbing group lower saturation scores were measured by the fingertip probe compared to the right ear measurement. The differences in saturation became greater as the saturation value at fingertip was lower.

CONCLUSION

Digital clubbing significantly influences the registrations of the SpO2 measurements by means of a fingertip probe, underestimating the saturation. It can be advised to use the ear sensor as good alternative for these patients.

Sublingual capnometry: a non-invasive measure of microcirculatory dysfunction and tissue hypoxia

With improvement in supportive care patients rarely die from their presenting illness but rather from its sequela, namely sequential multi-organ failure. Tissue hypoxia is believed to be the causation of multi-organ dysfunction syndrome (MODS). The expedient detection and correction of tissue hypoxia may therefore limit the development of MODS. The standard oxygenation and hemodynamic variables (blood pressure, arterial oxygenation, cardiac output) which are monitored in critically ill patients are 'upstream' markers and provide little information as to the adequacy of tissue oxygenation. Global 'downstream' markers such as mixed venous oxygen saturation and blood lactate are insensitive indicators of tissue hypoxia. Sublingual PCO(2) is a regional marker of microvascular perfusion and tissue hypoxia that holds great promise for the risk stratification and end-point of goal directed resuscitation in critically ill patients. This paper reviews the technology and application of sublingual PCO(2) monitoring.

Sensitivity of bronchial responsiveness measurements in young infants

OBJECTIVES

There is limited evidence on the preferred methods for evaluating lung function in infancy. The objective of this study was to compare sensitivity and repeatability of indexes of lung function in young infants during induced airway obstruction.

METHODS

The study population consisted of 402 infants (median age, 6 weeks). Forced flow-volume measurements were obtained by the raised volume rapid thoracoabdominal compression technique and were compared with indexes of tidal breathing, measurements of transcutaneous oxygen (Ptco(2)), and auscultation during methacholine challenge testing.

RESULTS

Ptco(2) was the most sensitive parameter to detect increasing airway obstruction during methacholine challenge, followed by forced expiratory volume at 0.5 s (FEV(0.5)). Both were superior to other indexes of forced spirometry as well as tidal breathing indexes and auscultation. Coefficients of variations for Ptco(2) and FEV(0.5) were 4% and 7%, respectively.

CONCLUSIONS

Ptco(2) and FEV(0.5) are the most sensitive parameters for measurement of bronchial responsiveness in young infants. Measurements of baseline lung function should preferably be made using FEV(0.5.) Measurements of bronchial responsiveness are best assessed using Ptco(2), which may be performed in nonsedated infants and improve feasibility of future studies on lung function in infancy.

Effect of Benzodiazepine Hypnotic Triazolam on Relationship of Blood Pressure and Paco2 to Cerebral Blood Flow During Human Non-Rapid Eye Movement Sleep

We sought to clarify the effect of short-acting benzodiazepine hypnotic on the relationship of arterial blood pressure and arterial partial pressure of carbon dioxide (Paco2) to regional cerebral blood flow (rCBF) during human non-rapid-eye-movement (non-REM) sleep. Nine young normal volunteers were treated in a randomized, crossover design with triazolam or placebo and underwent positron emission tomography at night. During wakefulness and stage 2 and slow wave (stages 3 and 4) sleep, we measured mean arterial blood pressure (MAP), Paco2, and absolute CBF. With triazolam compared to placebo, MAP reduced gradually. During stage 2 sleep, Paco2 increased and whole-brain mean CBF decreased. With triazolam, relative rCBF of the left orbital basal forebrain decreased more during stage 2 than slow wave sleep, whereas absolute CBF of the occipital cortex and cerebral white matter remained constant. During triazolam-induced stage 2 sleep, absolute CBF of the cerebral white matter correlated more strongly to both MAP and Paco2 than during placebo sleep and also correlated more strongly to both MAP and Paco2 than absolute CBF of the occipital cortex. In the frontal white matter, during triazolam-induced stage 2 sleep compared to wakefulness, absolute CBF was significantly better correlated to MAP, but not to Paco2. During triazolam-induced stage 2, the cerebral white matter may receive a modulated CBF regulation having the strengthened relationship of Paco2 to CBF and, more locally, the frontal white matter may depend precariously on CBF regulation.

‘Pole Test’ Measurements in Critical Leg Ischaemia

BACKGROUND

For the quantification of critical limb ischaemia (CLI) most vascular surgery units use sphygmo-manometric and transcutaneous oxygen pressure (TcPO2) measurements. However, measurements obtained by cuff-manometry can be overestimated especially in diabetic patients because of medial calcification that makes leg arteries less compressible. TcPO2 measurements present a considerable overlap in the values obtained for patients with different degrees of ischaemia and its reproducibility has been questioned. Arterial wall stiffness has less influence on the pole test, based on hydrostatic pressure derived by leg elevation, and this test seems to provide a reliable index of CLI.

OBJECTIVE

The objective of this study was to evaluate the pole pressure test for detection of critical lower limb ischaemia, correlating results with cuff-manometry and transcutaneous oxygen pressure.

DESIGN

University hospital-prospective study.

MATERIALS AND METHODS

Seventy-four patients (83 legs) with rest pain or gangrene were evaluated by four methods: pole test, cuff-manometry, TcPO2 and arteriography. CLI was present if the following criteria were met: (a) important arteriographic lesions+rest pain with an ankle systolic pressure (ASP) < or = 40 mmHg and/or a TcPO2 < or = 30 mmHg, or (b) important arteriographic lesions+tissue loss with an ASP < or = 60 mmHg and/or a TcPO2 < or = 40 mmHg. Fifty-seven lower limbs met the criteria for CLI.

RESULTS

Measurements obtained by cuff-manometry were significantly higher to those obtained by pole test (mean pressure difference: 40 mmHg, p<0.001). The difference between the two methods remained statistically significant for both diabetics (50.73, p<0.001) and non-diabetics (31.46, p<0.001). Mean TcPO2 value was 15.51 mmHg and there was no important difference between patients with and without diabetes. Overall, there was a correlation between sphygmomanometry and pole test (r = 0.481). The correlation persisted for patients without diabetes (r = 0.581), but was not evident in patients with diabetes. Correlation between pole test and TcPO2 was observed only for patients with diabetes (r = 0.444). There was no correlation between cuff-manometry and TcPO2. The pole test offered an accuracy of 88% for the detection of CLI. The sensitivity of this test was 95% and the specificity 73%.

The relationship of the transcutaneous oxygen tension, pulse waves and systolic pressures to the risk for limb amputation in patients with peripheral arterial disease and skin ulcers or gangrene

AIM

Our aim was to determine how the risk associated with presence of low transcutaneous oxygen tension (tcPO2) for subsequent major amputation in patients with skin ulcers or gangrene and peripheral arterial disease, compares with the risks associated with low peripheral pressures and low amplitude of pulse waves. Secondly, we determined whether combination of measurements of oxygen tension with that of the pressures or pulse wave amplitude predicts amputation better than pressure, wave or oxygen tension measurements alone.

METHODS

Measurements were carried out to obtain foot tcPO2, ankle and toe pressures, pressure indices, and toe pulse wave amplitude in 75 limbs with skin lesions and arterial disease of 66 patients referred to the vascular laboratory. These variables were related to the risk of a subsequent major amputation during a median time of 4.2 years, using Cox proportional hazards model.

RESULTS

Low oxygen tension was associated with increased risk of amputation (relative risks 2.16 and 2.55 for tcPO2 < or = 10 mmHg and < or = 20 mmHg, respectively, P<0.05; relative risk 2.22 for tcPO2 < or = 30 mmHg, P=0.07). The relative risks associated with cutoff values of ankle and toe pressures and pressure indices varied from 2.53 (toe < or = 20 mmHg, P<0.05) to 5.83 (ankle < or = 50 mmHg, P<0.001) and the relative risk associated with low wave amplitude (< or = 4 mm) was 3.41, P<0.01. The cutoff values of tcPO2 became insignificant when included in the models together with each pressure variable or pulse amplitude separately. In contrast, wave amplitude remained significantly associated with increased risk of amputation after controlling for each pressure variable (P<0.05).

CONCLUSIONS

TcPO2 < or = 10 mmHg and < or = 20 mmHg are related significantly to increased risk of amputation in patients with skin lesions and arterial disease, but these relative risks are similar in magnitude or smaller than those associated with low cutoff values of pressures, pressure indices or pulse wave amplitude. Low wave amplitude does provide significant information in addition to peripheral pressures with respect to the risk of amputation. On the other hand, low tcPO2 does not provide significant information in addition to peripheral pressures or pulse wave amplitude.

[Peculiarities of infusion-transfusion therapy for purulent-septic diseases of respiratory organs]

The oxygen-transporting blood surrogate perftoran was included in the infusion-transfusion therapy programme on various stages in the treatment of purulent-septic diseases of respiratory organs. Application of this method of intensive therapy had promoted the blood oxygentransporting function improvement in patients, as well as the respiratory-hemic hypoxia severity lowering and their treatment efficacy raising.

The availability and use of oxygen saturation monitoring in primary care in order to assess asthma severity

INTRODUCTION

The BTS/SIGN guideline recommends oxygen saturation (SaO2) monitoring as an objective measure of acute asthma severity, particularly in children, in both primary and secondary care. We assessed the availability and use of SaO2 monitoring for acute asthma assessment in primary care.

METHODS

Fax and telephone questionnaire of Primary Care services in the Edinburgh region to assess use of SaO2 monitoring in the past 24 months, in association with a 24-month retrospective assessment of A&E attendances with acute wheeze. Children over 12 months of age registered with eligible general practices attending A&E with wheeze and/or asthma were included.

RESULTS

There were replies from 103 general practices (100%) and eight Out-of-hours cooperatives (100%). Oxygen saturation monitoring was available in four general practices (3.9%) and three Out-of-hours cooperatives (37.5%). 1408 children attended A&E with wheeze/asthma, 721 referred by primary care. Oxygen saturation monitoring was available to 7.9% of A&E attendees from primary care, but documented in only 1.8% of primary care referrals.

CONCLUSIONS

SaO2 monitoring is not widely available in primary care and is infrequently used for the assessment of acute asthma. SaO2 measurement as an adjunct to clinical assessment of asthma in primary care needs encouragement.

Preamputation evaluation of limb perfusion with laser Doppler imaging and transcutaneous gases

We studied 31 subjects with severe leg ischemia and 29 age-matched nonischemic control subjects to compare preamputation assessments of leg ischemia using laser Doppler imaging (LDI), transcutaneous partial pressure of oxygen (TcPO(2)), and transcutaneous partial pressure of carbon dioxide (TcPCO(2)). TcPO(2) and TcPCO(2) were evaluated with Novametrix Medical Systems, Inc, monitors (Wallingford, Connecticut) and perfusion (flux) of skin topically heated to 44 degrees C, and adjacent nonheated areas were evaluated with a Moor Laser Doppler Imager (Moor Instruments, Ltd; Devon, England). LDI flux of heated areas, its ratio to nonheated areas, and TcPO(2) (not TcPCO(2)) were lower in ischemic subjects than in control subjects. LDI flux ratio performed better than TcPO(2) in identifying ischemia, with fewer false positive and false negative results. Moreover, LDI flux of heated skin detected a proximal to a distal gradient of perfusion in ischemic subjects, while TcPO(2) did not. LDI was superior to TcPO(2) in discriminating correctly between ischemic and nonischemic skin. The results suggest that an LDI ratio below 5 indicates nonviable skin.

[Respiratory responses to CO2 stimulation in hypercapnic patients with obstructive sleep apnea syndrome]

Obstructive sleep apnea can be associated with daytime chronic hypercapnia in some patients, but the prevalence of the phenomenon is highly variable in the published literature. The most often it is found in patients with coexisting COPD. There is also an evidence of persisting hypercapnia in OSA patients without other respiratory disease. In previous studies lung function impairment, obesity, gender, severity of OSAS have been considered to contribute to daytime hypercapnia. Several studies demonstrated that the defect in control of breathing can play a role in the development of chronic hypercapnia in patients with OSAS. The aim of the study was to estimate respiratory responses to hypercapnic stimulation in patients with OSAS and chronic daytime hypercapnia. Material consisted of 38 patients with OSAS and chronic hypercapnia (COPD was present in 24-group B, "pure" OSA in 14-group A) and 40 normocapnic OSA patients (group C). Lung function testing, blood gases and chemical control of breathing tests were performed in all of them before initiating therapy with nCPAP. Diagnosis of OSAS was stated with standard polisomnography and AHI was similar in mentioned groups.

RESULTS

Respiratory responses to hypercapnic stimulation were significantly lower in hypercapnic patients (A 10.6+/-4.6; B 9.5+/-5.6) in opposition to normocapnics (C 23.3+/-14.0 l/min/kPa). In all studied patients PaCO2 level significantly correlated with respiratory responses to hypercapnic stimulation (r=-.61), lung function indices (VC r=-.69 and FEV1 r=-.71), mean SaO2 during sleep (r=-.68), and BMI (r=.49), but not with the factors like age, AHI or minimal SaO2 during sleep. Analysis with multiple regression revealed that hypercapnic drive, mean SaO2 during sleep, FEV1 and BMI were the best predictors of hypercapnia in studied group, being responsible for 72% of the total variance in PaCO2 in our OSA patients (R2=0.72; p<0.0001).

CONCLUSION

predisposition to daytime hypercapnia in our OSA patients was related to dimished chemosensitivity to CO2, mean desaturation during sleep, the severity of obesity and impairment of lung function mainly due to coexisting COPD.

Can transcutaneous oxygen tension measurement determine re-amputation levels?

OBJECTIVE

To review the preoperative transcutaneous oxygen tension (TcPO2) measurements in patients having major lower leg amputation, and also consider the re-amputation rate, wound infection and the definitive level of amputation.

METHOD

A case-control study was performed in a consecutive cohort of 170 patients (1999-2003). Fifty-two patients underwent preoperative TcPO2 measurements (cases) and 118 patients did not (control). Multiple logistic regression analysis was performed to analyse independent risk factors associated with re-amputations.

RESULTS

Primary and definitive (in case of a re-amputation) amputation levels were lower in the TcPO2 group, although this did not reach statistical significance. The number of re-amputations in the TcPO2 group was significantly higher: 15 versus 18 patients (p=0.039). Selection of an amputation level with aTcPO2 of 30mmHg resulted in a positive predictive value of re-amputation of 41% and a negative predictive value of 90%. A cut off value of 20mmHg resulted in 41% and 77% respectively.

CONCLUSION

The use of TcPO2 measurements for major amputation level selection resulted in an increased rate of re-amputation. However, there was a trend in gaining a more distal definitive amputation level. Selection of an amputation level solely based on a TcPO2 value is unreliable.

A New Technique for Detecting Sleep Apnea-Related "Midnight" Surge of Blood Pressure

Patients with obstructive sleep apnea syndrome (OSAS) have been reported to be at greater risk for cardiovascular events, and midnight surge of blood pressure (BP) may be a mechanism of sleep apnea-related cardiovascular risk. However, there has been no accurate noninvasive technique to detect intermittent BP surge at the time of each sleep apnea episode. We therefore developed an experimental system to detect apnea-related short-term BP surge based on BP measurement triggered by peripheral (finger-tip) oxygen desaturation (a desaturation-triggered BP monitoring system). In 16 patients with OSAS, this new system successfully detected BP surges at the time of the sleep apnea, and the BP values were found to be significantly higher than those detected using a conventional fixed interval BP monitoring system (systolic BP [SBP] difference: 13 +/- 5.8 mmHg, p = 0.039; diastolic BP [DBP] difference: 10 +/- 6.8 mmHg, p = 0.032). The maximum SBP time rate (velocity of BP surge) showed a strong positive correlation with the apnea-hypopnea index (r = 0.855, p < 0.0001). In conclusion, we developed a noninvasive oxygen desaturation-triggered BP monitoring system that can successfully detect sleep apnea-related BP surge. The midnight BP surge detected by this new method was significantly associated with the severity of OSAS.

Measurement of tumor hypoxia in spontaneous canine sarcomas

We used positron emission tomography (PET) with [18F]fluoromisonidazole ([18F]FMISO) to study tumor hypoxia in six dogs with spontaneous sarcomas. The tumors were regarded as hypoxic if [18F]FMISO uptake exceeded normal tissue radioactivity by 40% (tumor/muscle ratio > 1.4) or if kinetic analysis indicated a positive [18F]FMISO tissue influx rate (Ki > 0) by a Patlak plot. Using these criteria, we found hypoxia in a fibrosarcoma grade II, an undifferentiated sarcoma, and an ostoeosarcoma, but not in a fibrosarcoma grade I, another osteosarcoma, and a myxosarcoma. In three animals, the tumor oxygen partial pressure (pO2) was also measured invasively using Eppendorf needle electrodes. In these cases, the Eppendorf measurements were confirmed by the [18F]FMISO PET results. In addition, [15O]H2O PET was performed in four dogs in order to assess tumor perfusion. Comparisons of the [18F]FMISO with [15O]H2O PET images in two cases showed that tumor hypoxia occurred in the tumor center with low perfusion, whereas perfusion was heterogeneous in a nonhypoxic tumor.