Search PubMed⌕ Search

Biomedical subjects

R G Walker

Publications and source records attributed to R G Walker.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of electrode polarity on internal defibrillation with monophasic and biphasic waveforms using an endocardial lead system.

INTRODUCTION: To test the hypothesis that the effect of shock polarity on defibrillation depends on waveform duration, this study determined strength-duration defibrillation curves of monophasic and biphasic truncated exponential waveforms for both polarities. METHODS AND RESULTS: Defibrillation thresholds (DFTs) were obtained in 32 pigs for catheter electrodes in the right ventricle (RV) and superior vena cava (SVC) using a modified Purdue technique. Both electrode polarities were tested in five different protocols. In part 1, DFTs were determined with 1- to 14-msec monophasic waveforms. In parts 2, 3, and 4, DFTs were determined with two different sizes of SVC electrodes for biphasic waveforms with a phase 1 of 4 or 6 msec and a phase 2 ranging from 1 to 10 msec. In part 5, DFTs were tested for monophasic waveforms ranging from 2 to 11 msec and for biphasic waveforms with a phase 1 duration corresponding to each monophasic waveform and a phase 2 held constant at 1 msec. Mean DFTs for monophasic waveforms were significantly lower when the RV electrode was an anode than when it was a cathode for waveform durations > or = 3 msec. For biphasic waveforms in which phase 2 was < or = phase 1 in duration, no significant difference in mean DFT was observed when polarity was reversed. Even a phase 2 as short as 1 msec could eliminate the DFT difference between polarities observed with monophasic shocks. When phase 2 was > or = 2 msec longer than phase 1, polarity did affect the DFT of biphasic waveforms; it affected the DFT similarly to a monophasic waveform of the same polarity as phase 2. Phase 1 duration and electrode size also affected the difference in DFT produced by changing the electrode polarity. CONCLUSIONS: For phase durations most commonly used clinically because of their low DFTs, reversing polarity changed defibrillation efficacy for monophasic but not biphasic shocks. For inefficient biphasic waveforms with phase 2 > or = 2 msec longer than phase 1, the DFT was lower when the RV electrode was an anode during phase 2, similar to the polarity difference for monophasic waveforms, suggesting that a long second phase of biphasic waveforms defibrillates in a similar fashion to monophasic waveforms.

Animals↗
PubMed1997

Dialysis adequacy and self-reported health status in a group of CAPD patients.

The purpose of the study was to describe in a cross sectional manner the self-reported level of health of a group of continuous ambulatory peritoneal dialysis (CAPD) patients and to establish whether any clinical or laboratory variables correlated with this measure of health. While undergoing routine baseline and 6 monthly measurements of weekly total urea over volume distribution (Kt/V) and weekly creatinine clearance (Ccr)/1.73 m2 body surface area (BSA), 57 patients voluntarily completed the Short Form 36 health status questionnaire (SF36) (a self-report, multidimensional, generic measure of health status). Weekly Kt/V was correlated with weekly Ccr (r = 0-81, p < 0.001). Thirty-one of the 57 patients were recorded as having Ccr < 65 L/week. A comparison with Australian interim normative data demonstrated that this group of CAPD patients reported lower scores on the eight physical and mental health components that are measured by the SF36 than did the general population. Patients who were most impaired in their physical functioning were more likely to be older, overweight, and to have a lower normalized protein catabolic rate (nPCR). Patients who were adequately dialyzed (Ccr > or = 65 L/week/1.73 m2) reported greater vitality than those patients recorded as having Ccr < 65 L/week/1.73 m2.

Adult↗
PubMed1996

Calmodulin controls adaptation of mechanoelectrical transduction by hair cells of the bullfrog's sacculus.

Deflection of the mechanically sensitive hair bundle atop a hair cell opens transduction channels, some of which subsequently reclose during a Ca2+-dependent adaptation process. Myosin I in the hair bundle is thought to mediate this adaptation; in the bullfrog's hair cell, the relevant isozyme may be the 119-kDa amphibian myosin I beta. Because this molecule resembles other forms of myosin I, we hypothesized that calmodulin, a cytoplasmic receptor for Ca2+, regulates the ATPase activity of myosin. We identified an approximately 120-kDa calmodulin-binding protein that shares with hair-bundle myosin I the properties of being photolabeled by vanadate-trapped uridine nucleotides and immunoreactive with a monoclonal antibody raised against mammalian myosin I beta. To investigate the possibility that calmodulin mediates Ca2+-dependent adaptation, we inhibited calmodulin action and measured the results with two distinct assays. Calmodulin antagonists increased photolabeling of hair-bundle myosin I by nucleotides. In addition, when introduced into hair cells through recording electrodes, calmodulin antagonists abolished adaptation to sustained mechanical stimuli. Our evidence indicates that calmodulin binds to and controls the activity of hair-bundle myosin I, the putative adaptation motor.

Adaptation, Physiological↗
PubMed1996

An extreme example of the neonatal form of Bartter's syndrome.

A male infant is described who had polyuria over the 4 months of his life with urine volumes exceeding 1,000 ml/kg per day, severe serum electrolyte losses, metabolic alkalosis and increased plasma renin activity (56 ng/ml per hour). He had a normal blood pressure and glomerular filtration rate when fluid replete. The urine flow rate was about 25% of the glomerular filtration rate. Renal histology showed hyperplasia of the juxtaglomerular apparatus and abnormalities of the proximal tubules. The features of this case suggest an extreme form of Bartter's syndrome presenting from the first days of life.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Left ventricular abnormalities in children, adolescents and young adults with renal disease.

The cardiac abnormalities that complicate chronic renal failure and renal replacement therapy are not well characterized in young people. These abnormalities are becoming more important because successful renal transplantation has resulted in children with end-stage renal failure living longer. Echocardiographic abnormalities of cardiac function and structure were studied in children and young adults (< 27 years old) with chronic renal failure (CRF, N = 32), end-stage renal failure treated with chronic peritoneal dialysis (CPD, N = 10) or renal transplantation (N = 30) or controls (N = 60). Left ventricular mass indexed for height (LVM/Ht and LVM/Ht2.7) and body surface area (LVM/SA), fractional shortening, measurement of left ventricular diastolic function (peak E and A wave velocities and the EA ratio) and structural (such as valvular) abnormalities were determined by echocardiography. The median (and range) of LVM/Ht in the groups were control 51.8 (23.1 to 119.8), CRF 60.2 (22.2 to 135.8), CPD 80.2 (14.5 to 100.9) and transplant group 97.8 (51.2 to 182.1) g/m. The increases in LVM/Ht, LVM/Ht2.7 and LVM/SA in the transplant group were significant (P < 0.01). The CRF group had significantly increased LVM/Ht2.7 and LVM/SA (P < 0.01). Systolic function was not significantly different between the groups. A significant correlation between creatinine and LVM indexed for height was found in the CRF group. Systolic or diastolic blood pressure could not be correlated with LVM indices in the transplant group. Changes in diastolic function were found (increased peak A wave velocity and decreased E/A ratios in the CRF and CPD groups, and increased peak E wave velocity in the transplant group). The study demonstrated that left ventricular hypertrophy is a frequent and often severe finding in children with chronic renal failure and those treated with renal replacement therapy. Factors other than hypertension and anaemia are important, and evidence was found for a link between serum creatinine and increased left ventricular mass prior to end-stage renal failure.

Adolescent↗
PubMed1996

Epicardial sock mapping following monophasic and biphasic shocks of equal voltage with an endocardial lead system.

INTRODUCTION: The reason for the increased defibrillation efficacy of biphasic shocks over monophasic shock is not definitely known. METHODS AND RESULTS: In six anesthetized pigs, we mapped the epicardium after transvenous defibrillation shocks to compare the activation patterns following successful biphasic shocks with unsuccessful monophasic shocks of the same voltage. The heart was exposed and a 510-electrode sock with approximately 4-mm interelectrode spacing was pulled over the entire ventricular epicardium and sutured to the pericardium. Defibrillation catheters were placed in the right ventricular apex and in the superior vena cava. Paired monophasic 12 msec and biphasic 6/6 msec defibrillation shocks were given using an up-down protocol to keep shock strength between the defibrillation thresholds for the two waveforms so that the biphasic shock was successful while the monophasic shock was not. Activation fronts immediately following 60 paired shocks were recorded and analyzed by animated maps of the first derivative of the electrograms. The ventricles were divided into apical (I), middle (II), and basal (III) thirds, and early sites, i.e., the sites from which activation fronts first appeared on the epicardium following the shock, were grouped according to their location. Postshock intervals, i.e., the time from the shock until earliest epicardial activation occurred, were also determined. No ectopic activation fronts followed the shock in 20 biphasic episodes. In the other 40 paired episodes, the number of early sites was smaller after biphasic shocks than after monophasic shocks [monophasic: 198 (total), 3.3 +/- 0.9 (mean +/- SD) per shock episode; biphasic: 67, 1.1 +/- 1.0, P < 0.05]. For biphasic but not monophasic shocks, early sites were less likely to arise from the middle (II) and basal (III) thirds than from the apical third (I) [monophasic: I: 84 (42%), II: 68 (34%), III: 46 (23%); biphasic: I: 49 (73%), II: 10 (15%), III: 8 (12%), P < 0.05]. Postshock intervals were significantly shorter for monophasic shocks (54 +/- 14 msec) than for biphasic shocks (75 +/- 23 msec, P < 0.05). CONCLUSION: The decreased number of activation fronts and the longer delay following the shock for the earliest epicardial appearance of those activation fronts that do occur may be responsible for the increased defibrillation efficacy for biphasic shocks.

Animals↗
PubMed1995

Influence of epicardial patches on defibrillation threshold with nonthoracotomy lead configurations.

BACKGROUND: In previous studies, epicardial patch electrodes decreased transthoracic defibrillation efficacy. We studied the effects of two inactive epicardial 14-cm2 titanium mesh patches on defibrillation energy requirements with nonthoracotomy internal lead configurations. METHODS AND RESULTS: A 6/6-millisecond biphasic shock wave-form was delivered via several electrode configurations 10 seconds after ventricular fibrillation was initiated with a 60-Hz generator. In two series, a total of 16 dogs (weight, 23.3 +/- 2.4 kg) underwent an up-down defibrillation protocol. In the first series, the defibrillation threshold (DFT) was determined for each electrode configuration in the presence of two inactive epicardial patches. In the second series, DFTs were determined in the presence of an inactive right ventricular (RV) or left ventricular (LV) patch alone. For several nonthoracotomy lead configurations tested in the first 8 dogs, the mean +/- SD DFT energy increased 49% to 97% with two inactive patches on the heart compared with no patches on the heart as follows: RV to superior vena caval (SVC) electrode, from 8.9 +/- 2.6 to 18.0 +/- 14.3 J; RV to SVC plus subcutaneous array electrode, from 7.0 +/- 2.4 to 10.7 +/- 5.3 J; RV to subcutaneous pectoral plate electrode, from 6.2 +/- 1.3 to 11.4 +/- 4.0 J (P < or = .05). The lowest DFT was achieved by defibrillating between the epicardial patches (3.8 +/- 3.3 J). The second series showed that DFT voltage requirements increased significantly for all three nonthoracotomy lead configurations with the inactive LV patch alone (P < or = .05) but not with the inactive RV patch alone. CONCLUSIONS: Inactive epicardial patches can significantly increase the defibrillation energy requirements for nonthoracotomy lead configurations. This negative impact may be due to an insulating effect of the patches and to a disturbance of the potential gradient field under the patches. If the same holds true in patients, these results have clinical implications. Functioning epicardial patch leads should be incorporated in the defibrillation lead system if already present. If the LV patch is nonfunctioning, such as because of a lead fracture, the marked increase in DFT due to an inactive LV patch calls for thorough DFT testing during surgery and, in selected patients, may necessitate patch removal to produce an effective transvenous-based system.

Animals↗
PubMed1995

Effect of rapid pacing and T-wave scanning on the relation between the defibrillation and upper-limit-of-vulnerability dose-response curves.

BACKGROUND: The critical-point and upper-limit-of-vulnerability (ULV) hypotheses predict that the ULV dose-response curve should be steeper and to the right of the defibrillation (DF) curve. Yet, some recent experimental data contradict this prediction. Two studies are presented that test two explanations for the contradiction: (1) Testing at a single point in the T wave underestimates the ULV dose-response curve and (2) ULV testing at normal heart rates does not mimic the mechanical or electrical state of the heart in ventricular fibrillation (VF). METHODS AND RESULTS: A nonthoracotomy lead system with a biphasic waveform was used throughout. In eight dogs, the dose-response curve widths (a measure of steepness) were compared between DF data and ULV data gathered at the peak (ULVPK), middownslope (ULVDWN), midupslope (ULVUP), and all times (scanning or ULVSCN) in the T wave. In another eight dogs, ULV data (ULVRAP) were gathered by scanning the T wave after 15 rapidly paced beats (166- to 198-ms pacing interval). The rapid pacing interval was chosen to more closely mimic the hemodynamics and activation rate of early VF. ULV data (ULVSTD) at normal heart rates were gathered for all animals. In the first study, scanning significantly reduced the ULV curve width (ULVSCN, 63.5 +/- 29.7 V; ULVPK, 81.9 +/- 45.2 V; ULVDWN, 116 +/- 36.5 V; DF, 105 +/- 22.0 V; P < .03) and significantly shifted the ULV curve to the right (ULV80 SCN, 410 +/- 62.6 V; ULV80 PK, 266 +/- 35.3 V; ULV80 DWN, 355 +/- 80.4 V; DF80, 427 +/- 60.9 V; P < .001). The subscript 80 signifies that the subject was left in normal sinus rhythm 80% of the time after that stimulus strength was delivered. In the second study, the ULVRAP curve was shifted dramatically to the right, the average ULV50 RAP being greater than the average DF90. Furthermore, 92% of the ULVRAP VF inductions occurred between 10 ms before and 50 ms after the peak of the T wave, suggesting that scanning of the entire T wave may not be necessary. CONCLUSIONS: With a single rapidly paced ULV sequence with limited T-wave scanning, it may be possible to estimate highly effective defibrillation doses with few VF episodes and high-voltage stimuli.

Animals↗
PubMed1995

Familial hypomagnesaemia--hypercalciuria leading to end-stage renal failure.

Several disorders of hypomagnesaemia of hetary renal origin are now recognised. The cases of two sisters from a consanguineous marriage with the syndrome of renal magnesium wasting, hypercalciuria and nephrocalcinosis are presented. Pathological examination of the heterozygous parental kidneys revealed mild focal interstitial fibrosis. This condition is a previously unreported cause of end-stage renal failure in childhood, and this report suggests that transplantation from heterozygous parental donors can be successfully undertaken without recurrence of the syndrome.

Calcium↗
PubMed1995

Renal transplantation in very young children.

Results of renal transplantation in very young children with end-stage chronic renal failure have been poor compared with those in older children and adults. Consequently small children either may not be treated or may be placed on chronic dialysis programmes. Between 1988 and 1992, six children under the age of 5 years received seven renal transplants at the Royal Children's Hospital, Parkville, Victoria, Australia; five from live donors and two from cadaver donors. All children were treated with peritoneal dialysis before transplantation, and immunosuppressed with a standardized regimen of cyclosporine, azathioprine and prednisolone. An extraperitoneal incision was used, and the donor renal vessels were anastomosed to the lower abdominal aorta and inferior vena cava or the common iliac vein. All children received intensive monitoring and fluid replacement during the peri-operative period. Patient survival was 100%. One cadaver graft failed 1 week after transplantation because of irreversible acute rejection. This child subsequently received a successful second transplant. Two children developed postoperative urinary fistulae which were treated successfully by further operation. Current renal function in all children is excellent. The success of this programme has led us to review our attitude towards renal transplantation in this age group and to advocate live donor renal transplantation as the treatment of choice in very young children with end-stage chronic renal failure whenever possible.

Cadaver↗
PubMed1995

Renal transplantation in young children.

AIMS: To review the outcome of renal transplantation in small children treated with triple immunosuppression at a single Australian centre. METHODS: The medical records of all children under the age of five years undergoing renal transplantation from 1988 were reviewed. The duration of follow-up was 30 months (range 18-36). RESULTS: Six children received seven renal allografts (five living-related [LR] and two cadaveric [CD]). They had a median age of 3.75 years (range 1.5-4.9) and weight of 11.6 kg (9.1-14.5) at the time of transplantation. All patients received an immunosuppressive regime involving cyclosporin A, azathioprine and prednisolone. There were no deaths. The only graft lost was a CD graft (severe acute rejection within one week of transplantation). Hypertension occurred in all recipients and usually required more than one antihypertensive drug for treatment. Renal function measured by serum median creatinine concentration (range) was 0.05 mmol/L (0.03-0.11) at three months (n = 6) and 0.10 mmol/L (0.07-0.22) at 30 months (n = 4). Growth estimated from median (range) height standard deviation scores was -1.97 (-1.36-(-4.04)) at three months (n = 6) and -1.90 (-1.74-2.50) at 30 months (n = 4). No patient was entirely weaned from prednisolone. Cyclosporin A side effects included hirsutism (five patients), gingival hyperplasia (six patients) and nephrotoxicity (three patients). CONCLUSIONS: Satisfactory patient and graft survival can be accomplished in this recipient age group. The results compare with other international experience and accumulating Australian experience. Hypertension and poor skeletal growth were consistent observations. The long-term outcome of renal function using triple immunosuppression remains to be determined.

Azathioprine↗
PubMed1995

Influence of malpositioned transvenous leads on defibrillation efficacy with and without a subcutaneous array electrode.

Some patients cannot receive a transvenous lead system because of high defibrillation thresholds (DFTs). We hypothesized that a right ventricular (RV) catheter electrode not extending as far as possible into the RV apex could cause high DFTs. Recently, a subcutaneous array (SQA) electrode has been shown to lower DFTs substantially. We compared the influence of a malpositioned RV catheter electrode on defibrillation efficacy for endocardial lead systems with and without a SQA. In eight anesthetized pigs, defibrillation catheters were placed in the RV apex and near the junction of the superior vena cava (SVC) and right atrium. SQA, formed by three elements, each 20 cm in length, was placed in the left thorax. DFTs were determined for a biphasic waveform using an up/down protocol with the RV catheter at the apex and with it repositioned 1-cm and 2-cm proximal to the apex. The mean DFT energies for the configurations with a SQA were less than those without a SQA for every catheter position. The placement of the RV catheter away from the apex caused an increase in defibrillation energy for the configurations without a SQA (apex: 17.1 +/- 3.8 J [mean +/- SD]; 1 cm: 20.1 +/- 4.6 J; 2 cm: 27.6 +/- 9.5 J; P < 0.05), but not for the configurations with a SQA (apex: 12.2 +/- 2.2 J; 1 cm: 12.3 +/- 2.9 J; 2 cm: 12.1 +/- 0.9 J: P = NS). These results suggest that a malpositioned RV catheter electrode, at the time of implantation or by late dislodgment, significantly elevates DFTs for a total endocardial system but not for a system that includes a SQA.

Animals↗
PubMed1995

Choosing the optimal monophasic and biphasic waveforms for ventricular defibrillation.

INTRODUCTION: The truncated exponential waveform from an implantable cardioverter defibrillator can be described by three quantities: the leading edge voltage, the waveform duration, and the waveform time constant (tau s). The goal of this work was to develop and test a mathematical model of defibrillation that predicts the optimal durations for monophasic and the first phase of biphasic waveforms for different tau s values. In 1932, Blair used a parallel resistor-capacitor network as a model of the cell membrane to develop an equation that describes stimulation using square waves. We extended Blair's model of stimulation, using a resistor-capacitor network time constant (tau m), equal to 2.8 msec, to explicitly account for the waveform shape of a truncated exponential waveform. This extended model predicted that for monophasic waveforms with tau s of 1.5 msec, leading edge voltage will be constant for waveforms 2 msec and longer; for tau s of 3 msec, leading edge voltage will be constant for waveforms 3 msec and longer; for tau s of 6 msec, leading edge voltage will be constant for waveforms 4 msec and longer. We hypothesized that the best phase 1 of a biphasic waveform is the best monophasic waveform. Therefore, the optimal first phase of a biphasic waveform for a given tau s is the same as the optimal monophasic waveform. METHODS AND RESULTS: We tested these hypotheses in two animal experiments. Part I: Defibrillation thresholds were determined for monophasic waveforms in eight dogs. For tau s of 1.5 msec, waveforms were truncated at 1, 1.5, 2, 2.5, 3, 4, 5, and 6 msec. For tau s of 3 msec, waveforms were truncated at 1,2,3,4,5,6, and 8 msec. For tau s of 6 msec, waveforms were truncated at 2,3,4,5,6,8, and 10 msec. For waveforms with tau s of 1.5, leading edge voltage was not significantly different for the waveform durations of 1.5 msec and longer. For waveforms with tau s of 3 msec, leading edge voltage was not significantly different for waveform durations of 2 msec and longer. For waveforms with tau s of 6 msec, there was no significant difference in leading edge voltage for the waveforms tested. Part II: Defibrillation thresholds were determined in another eight dogs for the same three tau s values. For each value of tau s, six biphasic waveforms were tested: 1/1, 2/2, 3/3, 4/4, 5/5, and 6/6 msec. For waveforms with tau s of 1.5 msec, leading edge voltage was a minimum for the 2/2 msec waveform. For waveforms with tau s of 3 msec, leading edge voltage was a minimum for the 3/3 msec waveform. For waveforms with tau s of 6 msec, leading edge voltage was a minimum and not significantly different for the 3/3, 4/4, 5/5, and 6/6 msec waveforms. CONCLUSIONS: The model predicts the optimal monophasic duration and the first phase of a biphasic waveform to within 1 msec as tau s varies from 1.5 to 6 msec: for tau s equal to 1.5 msec, the optimal monophasic waveform duration and the optimal first phase of a biphasic waveform is 2 msec, for tau s equal to 3.0 msec, the optimal duration is 3 msec, and for tau s equal to 6 msec, the optimal duration is 4 msec. For both monophasic and biphasic waveforms, optimal waveform duration shortens as the waveform time constant shortens.

Animals↗
PubMed1994

Evaluation of ultrasonographic diagnostic criteria for autosomal dominant polycystic kidney disease 1.

Although ultrasound is commonly used for screening subjects at risk of polycystic kidney disease 1 (PKD1), there has been no evaluation of ultrasonographic diagnostic criteria. We used DNA linkage among subjects from 128 sibships within 18 PKD1 families as the basis for an assessment of ultrasound sensitivity. Positive and negative predictive values were calculated to allow assessment of different diagnostic cut-off points in previously undiagnosed cases. Currently used criteria (bilateral cysts with at least two in one kidney) provided good sensitivity (88.5% at age 15-29 years and 100% at 30 years and above) but performance could be improved by less stringent criteria in subjects aged 15-29 years and more stringent criteria in older family members, in whom simple renal cysts are frequent. The presence of at least two renal cysts (unilateral or bilateral) in individuals at risk and younger than 30 years may be regarded as sufficient to establish a diagnosis; among those aged 30-59 years, the presence of at least two cysts in each kidney may be required, and among those aged 60 years and above, at least four cysts in each kidney should be required.

Adolescent↗
PubMed1994

Triple immunosuppression with subsequent prednisolone withdrawal: 6 years' experience in paediatric renal allograft recipients.

Thirty-four children (< or = 15 years of age) with end-stage renal failure received 39 renal allografts between 1985 and 1991 and were treated with cyclosporin A (CyA), azathioprine and low-dose prednisolone (PNL). We aimed to withdraw PNL by 6 months after transplantation. Median duration of follow-up was 2 years 4 months (range 0.1 month to 6 years 4 months). There were no deaths. Crude graft survival for living-related grafts (n = 9) was 100%, although only 1 patient has been followed for > 2 years. For cadaveric grafts (n = 30), 1- and 5-year actuarial graft survivals were 90% and 79% respectively. At 12 months posttransplant, the median (range) glomerular filtration rate for all patients was 63 (19-109) ml/min per 1.73 m2 (n = 25) and at 5 years was 48 (17-64) ml/min per 1.73 m2 (n = 9). Complications observed included rejection episodes which occurred after discontinuation of PNL. Long-term (after 12 months), 28% of patients remain on PNL. Hypertension was present in more than 50% of patients. Severe CyA nephrotoxicity was not seen. Catch-up growth as determined by the change (delta) in mean height standard deviation score (Ht-SDS) was noted at 1 year [delta SDS/year = +0.60; P < 0.001 (n = 18)] and at 2 years [delta SDS/year = +0.27; P < 0.01 (n = 16)] in pre-pubertal patients. The median Ht-SDS at 2 years for pre-pubertal children was -0.71 SD and growth velocity did not improve thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗