[FIO2 and SpO2 during cardiac surgery in neonates and infants]

Fractional inspired oxygen (FIO2) applied before and after a repair or palliative procedure for cardiac defects along with SpO2 measured by pulse oximeter were reviewed from anesthetic records of 62 neonates and infants. Fentanyl was used for anesthesia, except in cases without i.v. route in which sevoflurane with nitrous oxide in oxygen was used for induction of anesthesia. FIO2 was adjusted using air and oxygen. The lower FIO2 was applied to the patients for a closure of ventricular septal defect, a reconstruction of coarctation or interrupted aortic arch, and pulmonary artery banding, while the higher FIO2 was used for systemic-to-pulmonary artery shunts and the repair of tetralogy of Fallot. In the congenital heart disease with the intracardiac shunt, the magnitude of the shunt flow and hemodynamics can be altered by changing systemic and pulmonary vascular resistance which could be induced by various ways. Since alveolar oxygen tension is a known determinant of pulmonary vascular resistance, an appropriate FIO2 should be applied to each patient with different pathophysiology. A low FIO2 should be set for the cases with nonrestrictive left-to-right shunting, since a high FIO2 may cause a torrential pulmonary blood flow. A high FIO2 is preferable for the cases with right-to-left shunting and a concomitant decreased pulmonary blood flow.

Transcutaneous oxygen tension measurement in patients with chronic arterial obstructive disease: reliability and long-term variability of the method

Although transcutaneous oxygen tension (TcpO2) measurement may be useful for assessing changes in regional perfusion induced over time by drug or surgical treatment in patients with chronic arterial obstructive disease (CAOD), the reliability of the method over a long-term period is not know. To approach this problem, the authors evaluated retrospectively the behavior of TcpO2 measurement over time in patients with CAOD. To eliminate confounding influences due to the concomitant vascular disease at the limb level, data analysis was performed on TcpO2 measured at the right infraclavicular position. The median length of follow-up ranged from twenty days in 34 patients to 832 days in 3 patients (n = 2 and n = 10 individual sequential replications respectively). Initial and final TcpO2 values did not differ significantly even at the longest follow-up term, which indicates that the parameter is constant over time. The intrapatient variation coefficient of TcpO2 (calculated over at least three individual replications) ranged between an average of 11% to 16.2%. The corresponding interpatient variation fluctuated between 15.5% and 33.4%, a variability explained to some extent by sex-related influences, but, at least in the range of this sample, not by age, arterial oxygen levels, or disease status. Thus TcpO2 levels per se are stable, implying that TcpO2 measurement has the potential to record consistent changes caused by specific therapeutic interventions or the clinical evolution of patients with CAOD. However, the intrapatient and interpatient variability of the method has to be taken into account when TcpO2 is used for the follow-up and the physiopathologic study of patients with CAOD.

Comparison between the use of whole blood versus a diluted perfusate in regional isolated perfusion by continuous monitoring of transcutaneous oxygen tension: a pilot study

In 12 successive women (median age, 58 [39-89] years) who were treated with regional isolated perfusion for melanoma of the lower extremities, peroperative continuous monitoring of the transcutaneous oxygen tension (PtcO2) was performed as an indicator for tissue oxygenation and (sub)cutaneous perfusion. Regional perfusion started using whole blood as perfusate with a hematocrit of 40.7 +/- 4.9. After 40 min of drug circulation the perfusate was diluted to a hematocrit of 25.3 +/- 4.9, a value usually applied in perfusion. Flow rates (mean 51.2 +/- 14.4 mL/min/L perfused tissue) were kept at a level that caused no systemic leakage and no more than 10-cm increase above starting venous pressure. Oxygen supply was set at one half of the flow of the perfusate (in mL/min). The mean PtcO2 during the first part of perfusion, in which seven patients could achieve preperfusion levels for at least some of the time, was significantly higher than during the last part, in which no patient reached the preperfusion level (30.8 mm Hg vs 23.5 mm Hg; p = .0019). The mean maximal decrease in PtcO2 after dilution was 21.3 +/- 11.6 mm Hg. Venous blood gases of the perfusate also deteriorated after dilution. Two patients encountered a grade III and two a grade IV toxicity reaction after perfusion. We conclude that increasing the hematocrit of the perfusate to physiologic levels by using whole blood can guarantee a physiologic tissue oxygenation at relatively low flow rates. However, physiologic tissue oxygenation on its own is not enough to prevent toxicity after perfusion.

The influence of maternal oxygen administration on the fetus

During the last few years opinions have been divided on the advantages and disadvantages of oxygen administration in pregnancy and during labor. We review the present knowledge regarding the influence of maternal oxygen inhalation on the fetus. We conclude that the fetus may benefit from oxygen therapy during pregnancy and labor.

The effect of nonnutritive sucking on oxygenation in healthy, crying full-term infants

Crying in healthy, recently born infants has been associated with decreased oxygenation, which may prolong adjustment to extrauterine life. This research investigated the use of nonnutritive sucking (NNS) as an intervention to reduce crying and prevent any decreases in oxygenation that may occur in crying healthy term infants between 9 and 72 hours of life. Twenty-nine experimental group infants, who received a pacifier (NNS) immediately after crying was induced by a heelstick, had statistically significantly higher transcutaneous oxygen tensions (tcPO2S) compared with baseline values than 30 control (ONNS) infants who did not. Infants who received NNS also had higher tcPO2S after crying than infants who did not. NNS, which attenuates crying, may alleviate crying-induced oxygen decreases in healthy, transitional newborn infants.

Alleviation of the pain of heel prick in preterm infants

The hypothesis that the variability of physiological parameters may indicate pain or stress in the neonate was examined. Four parameters (heart rate, respiratory rate, transcutaneous oxygen tension, and carbon dioxide tension) were examined over a 2 minute epoch in response to a heel prick in an attempt to measure stress/pain in 35 preterm newborn infants (26-34 weeks' gestation) half of whom were receiving intensive care. The change in absolute values of these parameters did not discriminate a dummy procedure without prick from the actual procedure containing the prick (paired t test), but the variability of the parameters during an epoch showed significant discrimination. Three procedures were evaluated to reduce this distress using unpaired t test. The use of local anaesthetic cream was not successful. The components of the mixture cause vasoconstriction that would reduce blood flow to the heel and lead to more squeezing which is likely to be painful in the presence of tissue damage. A nurse comforting the infant with tactile and vocal stimulation was slightly helpful but the use of a spring loaded lance was most successful in reducing the distress. The use of spring loaded lances may be more humane for heel pricks.

Hyperventilation in Patients Who Have Sustained Myocardial Infarction after a Work Injury

Patients who present with acute myocardial infarction after a work injury (AMI-WI) often report symptoms consistent with chronic hyperventilation which date back as far as the work injury itself, rather than to the AMI. The aim of the study was to test the hypothesis that hyperventilation significantly contributes to the symptoms of AMI-WI patients.

The prevalence of hyperventilation was assessed by clinical capnography in 12 AMI-WI patients, 20 normal controls, 15 AMI patients whose AMI was conventional and not subsequent to a work injury (AMI-C) and 14 patients with post-traumatic stress disorder (PTSD). End-tidal carbon dioxide partial pressure (PetCO2) was measured at rest, after 1 min hyperventilation (FHPT), after recall of the relevant stressor (Think) and when the breathing was felt to be normal (MBIN).

PetCO2 levels after FHPT were: 29.0±1.5 (mean±SD) mmHg for AMI-WI; 26.7±1.9 mmHg for PTSD; 32.1± 4.1mmHg for AMI-C and 33.7±1.4 mmHg for the controls ( P< 0.05 and P< 0.01 for AMI-WI and PTSD, respectively, versus controls). After Think, the levels were 25.8±1.6 mmHg for AMI-WI, 24.6±1.4 mmHg for PTSD, 31.2±4.1mmHg for AMI-C and 31.2± 1.5 mmHg for normals ( P<0.05 and P<0.01 for AMI-WI and PTSD, respectively, versus controls). For MBIN, values of PetCO2 were 26.8±1.7 mmHg and 26.7±1.5mmHg for AMI-WI and PTSD versus 33.8±1.2 mmHg for normals, ( P< 0.01 for both versus controls). Ten AMI-WI and 12 PTSD were positive for hyperventilation versus four AMI-C patients and four controls ( P< 0.01). The implications for rehabilitation, compensation and pathophysiology of AMI-WI are discussed, both from a medical-scientific perspective and in terms of admissible legal evidence.

Comparison of macro- and micro-lightguide spectrophotometric measurements of microvascular haemoglobin oxygenation in the tuberculin reaction in normal human skin

The changes in haemoglobin oxygenation (SO2) occurring in the tuberculin reaction in human skin were measured using macro- and micro-lightguide spectrophotometry and the results compared. A significant difference was found between the measurements from the respective instruments, demonstrating that the micro-lightguide technique measures only in the most superficial capillaries. Laser Doppler flux (LDF) and transcutaneous oxygen (tcpO2) measurements were also obtained concurrently. At the height of the reaction, heating did not significantly change SO2 or LDF, showing that the vessels in the skin were maximally vasodilated. Although SO2 was increased in the reaction, tcpO2 decreased. This suggests that the infiltrating cells may present a diffusion barrier to oxygen between the capillaries and the tissue cells. This study has shown that micro-lightguide spectrophotometry gives a local picture of intracapillary oxygen supply, which is useful in elucidating the pathophysiological changes occurring during chronic inflammation.

Effects of salbutamol inhalations on transcutaneous blood gases in children during the acute asthmatic attack: from acute deterioration to recovery

Nine children, 7-16 years of age, were studied repeatedly during an acute asthmatic attack, from acute deterioration to recovery. The transcutaneous blood gases, forced expiratory volume in 1 s (FEV1) and maximum expiratory flow when 25% of vital capacity remained to be expelled (MEF25) were monitored before and after salbutamol inhalation. The flow-volume variables were markedly impaired in the acute phase but improved gradually by the time of recovery. The transcutaneous PO2 (tcPO2) decreased in the acute and early recovery phase but improved by the late recovery phase. In the acute phase, the salbutamol inhalations increased the FEV1, indicating an improvement in central airway function, but also reduced the MEF25 and tcPO2 in some of the children. The changes in tcPO2 after the inhalations correlated with the changes in MEF25 (p < 0.001), thereby indicating a common denominator, probably the condition of the peripheral airways. In the recovery phase, the FEV1, MEF25 and tcPO2 improved after the inhalations (p < 0.05). In conclusion, transcutaneous PO2 can be used to evaluate the effects of treatment in children with acute asthmatic symptoms and may add information about peripheral airway function which may prove particularly valuable in small children where few methods are available for such measurements.

[Usefulness of transcutaneous oximetry in detection of diabetic microangiopathy in lower limbs]

The purpose of the work was an assessment of the usefulness of transcutaneous measurement of O2 pressure in the foot (in recumbent position, recumbent with venostasis, elevated and erect position) for the detection of microcirculation disturbances in patients with diabetes mellitus. The studies included 43 patients with type I and II diabetes without haemodynamically significant stenoses of the axial arteries of the lower limbs, and a control group of 14. It was found that already in the period preceding the development of obliterative lesions in the arteries, microcirculation disturbances in the lower limbs became manifest causing statistically significant decrease of tcPO2 in patients with type I and II diabetes mellitus. The values of tcPO2 in position with limb elevation differentiate best these two groups of patients.

The effect of insufflation leaks in long-term ventilation. Waking and sleeping transcutaneous gas tensions in ventilator-dependent patients with an uncuffed tracheostomy tube

Transcutaneous blood gases were recorded for 60 min when awake and asleep in 10 ventilator-dependent patients with high tetraplegia who used a pressure-limited ventilator and uncuffed tracheostomy tube. The mean arterial oxygen tension awake was 16.0 kPa compared with 15.2 kPa when asleep; the mean arterial carbon dioxide tension awake was 3.2 kPa, compared with 3.9 kPa when asleep. The oxygen tensions in each patient during the awake and sleep states were not significantly different between the two states, but during sleep the carbon dioxide tension was significantly greater.

Autonomic neuropathy influences great toe blood pressure

OBJECTIVE

To assess the influence of autonomic neuropathy on toe blood pressure (TBP), a parameter used currently as an ischemic index.

RESEARCH DESIGN AND METHODS

The age-matched study subjects included 20 non-insulin-dependent diabetes mellitus (NIDDM) patients with autonomic neuropathy (DN) and 10 NIDDM patients without autonomic neuropathy (D), assessed by standard cardiovascular tests and galvanic skin response, and 8 control subjects (C). None of the subjects had peripheral vascular disease (PVD) (ankle/brachial index 0.9-1.1.

RESULTS

The TBP and toe/brachial index (TBI) were significantly lower in DN than in C and D (P < 0.01). The saturation index (SI), the ratio between foot venous and arterial partial pressure of oxygen (PO2), was significantly higher in DN than in C and D (P < 0.05). An inverse relationship was found between TBI and SI (r = 0.554, P = 0.001).

CONCLUSIONS

The autonomic nervous system directly influences peripheral circulation. In diabetic patients without PVD, a failure of sympathetic fibers caused by autonomic neuropathy could lead to a reduction of TBP. Therefore, TBP cannot be used as an ischemic index in diabetic patients.

[The evaluation of the oximetric and Doppler sonographic parameters in patients with chronic venous insufficiency. A controlled double-blind clinical study versus placebo]

Twenty four patients suffering from chronic venous insufficiency of the lower limbs were treated with sulfo-mucopolysaccharides (SMPS) or placebo in a double-blind controlled study. At recruitment, and again at 60 and 120 days of ongoing treatment, each patient was tested for transcutaneous partial oxygen tension and for pressure in the posterior tibial vein and saphena by Doppler sonography. Findings were assessed in each case separately for the affected limb versus the unaffected, or for the more severely affected versus the contralateral limb in patients affected bilaterally. Patients treated with the test product, but not those treated with placebo, showed definite reduction of venous pressure in the posterior tibial vein and internal saphena of the affected or more severely affected limb at 60 days of treatment: namely -35% from basal for the posterior tibial vein and -28% for the internal saphena. Again on the affected or more severely affected side, patients treated with SMPS showed improved transcutaneous oxygen tension amounting to +13.8% from basal at 60 days, as opposed to worsening condition in the placebo group.

Oxygen desaturation following voluntary hyperventilation in normal subjects

To investigate the severity of oxygen desaturation following voluntary hyperventilation (VHV) in normal subjects and its possible relation to chemoresponsiveness, we examined respiration following VHV in 16 normal male subjects. Monitoring was performed according to the standard polysomnography protocol including measurements of arterial oxygen saturation (SaO2) and transcutaneous PCO2 (PtcCO2). The subjects hyperventilated voluntarily for 3 min, and were then observed for more than 15 min. They hyperventilated again for another 3 min, and were followed again for more than 15 min. Eleven subjects fell into non-REM sleep after VHV, and their mean lowest SaO2 was 67.6 +/- 13.0% (n = 15 trials in 11 subjects, mean +/- SD). Falling asleep during hypocapnia caused desaturation, and periodic breathing was invariably observed soon after. The difference between the PtcCO2 during non-REM sleep with stable breathing and the PtcCO2 when the SaO2 was 90% following VHV was defined as the delta PtcCO2 (90). The delta PtcCO2 (90) and hypoxic ventilatory response (HVR) were positively and significantly correlated (r = 0.73, p < 0.01). While the subjects were awake, the mean lowest SaO2 was 73.5 +/- 17.4% (17 trials in 12 subjects). Remaining awake induced oxygen desaturation in some subjects but not in others. In one subject, desaturation during the waking state was caused by hypoventilation, not by central apnea. In the seven subjects whose respiration following VHV was monitored during the waking state in one trial and during the sleeping state in another trial, plots of the PtcCO2-SaO2 relationship for the waking state were generally positioned above those made for the sleeping state.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of theophylline on periodic breathing in congestive heart failure measured by transcutaneous oxygen monitoring

The effect of theophylline on periodic breathing was measured by transcutaneous oxygen monitoring in 7 patients suffering from chronic congestive heart failure. Theophylline significantly decreased the frequency of Cheyne-Stokes breathing. Transcutaneous oxygen monitoring proved to be a useful method to follow changes in the breathing pattern. The suggested mechanism of action of theophylline in reducing the incidence of periodic breathing is blockade of adenosine receptors.

Comparison of transcutaneous oximetry and laser Doppler flowmetry as noninvasive predictors of wound healing after excision of extremity soft-tissue sarcomas

BACKGROUND

We wished to determine whether transcutaneous oximetry or laser Doppler flowmetry (LDF) could identify patients at risk for wound failure after conservative, limb-sparing surgery for extremity sarcomas.

METHODS

Studies were performed on postoperative days (PODs) 1, 4/5, 7, and 9. Measurements of transcutaneous oxygen pressure (tcPO2) were taken at breathing room air (BL) and 100% oxygen (rate tcPO2). LDF measurements were taken at multiple sites along the wound, and a perfusion index was calculated.

RESULTS

Twenty-four patients were studied. Four (17%) had nonhealing wounds. There was no difference in tcPO2 (BL) values between healed and nonhealing wounds. Measurement of rate tcPO2 on POD 1 was significantly lower in the nonhealing wounds than in those with normal healing (28.5 +/- 12.1 mm Hg vs 14.3 +/- 16.2 mm Hg, mean +/- SD, p = 0.03). Rate tcPO2 values increased significantly in healing wounds from POD 1 to PODs 7 and 9 (p = 0.006, p = 0.009). This increase was absent in nonhealing wounds. A clear separation was noted in rate tcPO2 values between groups, with a minimum rate tcPO2 value recorded in a healed wound of 9 mm Hg/min, compared with the maximum value in a nonhealing wound of 7 mm Hg/min. The LDF perfusion index failed to predict wound healing at any of the measured time points.

CONCLUSIONS

This study showed that measurement of tcPO2 during oxygen inhalation can accurately predict wound healing in patients after excision of an extremity sarcoma.

Effects of routine hyperventilation on PCO2 and PO2 in normal subjects: implications for EEG interpretations

There are few data in the EEG literature describing the time course of hyperventilation-(HV) induced changes in blood gases, despite this being a routine activating procedure. We studied changes in blood gases and EEG in nine normal adult subjects before, during, and after HV. The mean PCO2 fell 18 mm Hg from the baseline during HV and recovered in 7 min. The mean PO2 rose 7 mmHg during HV and fell to 25 mm Hg below baseline 5 min after HV. The PCO2 recovery period is longer than is usually assumed in clinical EEG. The PO2 fall to a nadir at 5 min after the end of HV suggests that close attention should be paid to this period, as is confirmed by the re-buildup seen in moyamoya disease. Despite uniform changes in blood gases, the EEG median power frequency change showed marked variability; on average, it dropped by 1 Hz during HV and returned to baseline within 2 min of resumption of normal respiration. The EEG root-mean-square power showed a 200% increase during HV and also had returned to normal within 2 min.

Effects of short-term NIPPV in the treatment of patients with severe obstructive sleep apnea and hypercapnia

Although nasal continuous positive airway pressure (CPAP) is effective in the treatment of most patients with obstructive sleep apnea (OSA), there is a small group of such patients in whom rapid eye movement (REM) hypoventilation and CO2 retention persist despite the use of CPAP and supplemental oxygen. In this report we describe our experience with nocturnal nasal ventilation (nocturnal nasal positive pressure ventilation [NIPPV] in such patients and its effectiveness in reversing daytime hypercapnia. Thirteen patients, aged 28 to 69 years, with severe OSA confirmed on polysomnography, failed to respond to initial CPAP therapy. All were grossly obese (body mass index [BMI] > 35 kg.ml-1) and hypercapnic (mean PaCO2, 62 mm Hg). Nocturnal nasal ventilation was commenced using a volume-cycled ventilator, which was well tolerated in all patients. After 7 to 18 days of NIPPV, significant improvements in daytime arterial blood gas values were achieved, with a rise in arterial oxygen tension from 50 +/- 2.6 (SEM) to 66 +/- 3 mm Hg (p < 0.001) and a fall in CO2 from 62 +/- 2.5 to 46 +/- 1 mm Hg (p < 0.0001). Nine of the 13 patients were able to be established on a regimen of nasal CPAP after this period, while 3 patients required a longer period (up to 3 months) before adequate nocturnal ventilation could be maintained. In one patient, the improvements in ventilatory drive achieved with NIPPV could not be maintained on CPAP, and she was transferred on to NIPPV long term. These results indicate that effective nasal ventilation leads to an overall improvement in spontaneous ventilation and blood gas values both awake and asleep. We believe this improvement is the result of improved central ventilatory drive. Short-term NIPPV provides lasting benefits allowing the majority of such patients to resume CPAP therapy. Short-term intervention with this therapy should be considered as an interim measure in patients with severe hypercapnic OSA who fail to respond to initial CPAP therapy.

[Nocturnal oxygen therapy in chronic obstructive bronchitis?]

Patients with chronic obstructive pulmonary disease suffer often from sleeping disorders. A cause for these complaints is the disturbed respiration during sleep. By such ventilatory alterations arterial oxygenation is decreased and periodic severe desaturation may occur. For investigation of oxygenation during the night, pulse oximetry is suited best. For difficult problems polysomnography may be used. Treatment is based primarily on optimal anti-obstructive therapy with bronchodilators and antiinflammatory agents and an adapted physical therapy. In selected patients administration of oxygen by a nasal tube is advantageous. Patients with severe desaturation and with an overlap syndrome profit most from additional oxygen treatment. Survival can thus be prolonged and the quality of life is improved.

[Persistence of fetal circulation and high frequency oscillation]

High frequency ventilation (HVF) was used in 17 newborns with severe respiratory distress due to persistent fetal circulation. All patients except one had been treated previously but not satisfactorily by conventional ventilation. Four children died from neurological causes despite respiratory improvement. HVF failed in one case. Twelve newborns recovered without any sequelae. Thus HVF appears to be a most valuable ventilation technique in this situation.

Continuous tissue oxygenation assessment during bloodflow alterations in an isolated hindlimb model of the pig

A continuous intramuscular oxygen tension sensor was compared, with transcutaneous oximetry and laser Doppler flowmetry, during periods of arterial flow alterations in an isolated hindlimb model in the pig. The intramuscular oxygen tension sensor correlated well with bloodflow and was superior to the other two methods.

The usefulness of capillary microscopy, transcutaneous oximetry and laser Doppler fluxmetry in the assessment of the severity of lower limb ischaemia

TMo date, capillary microscopy, transcutaneous oximetry (tcpO2) and laser Doppler fluxmetry are frequently used in the investigation of skin microcirculation in patients with lower limb ischaemia. The concomitant microcirculatory disturbances may be useful in addition to macrocirculatory parameters to discriminate the different degrees of ischaemic severity. The best ways of application of these methods and the choice of the best parameters to assess ischaemia have been insufficiently investigated. Therefore, skin microcirculation was investigated with the use of these techniques in 130 patients with different stages of lower limb ischaemia, divided according to their ankle-to-brachial pressure index (ABI). Patients were investigated in the sitting and the supine position. Measurements were performed at rest and during reactive hyperaemia following arterial occlusion, and before and after local skin heating. The reactive hyperaemic response using laser Doppler fluxmetry differed in every patient group investigated. Capillary red blood cell velocity was markedly impaired in critically ischaemic patients (ABI < 25%). Transcutaneous oxygen pressure measurements at rest rendered the highest positive predictive value (PV; 87%) to classify patients as having clinically severe ischaemia (Fontaine 3 or 4). Ankle and toe pressure measurements provided a PV value of 78%. Microcirculatory parameters and techniques appear to be useful as an addition to standard macrocirculatory techniques to assess the severity of lower limb ischaemia. This is particularly of importance in patients in whom macrocirculatory parameters are unattainable.