Significant Differences In Ventilation Research Articles

Influence of Pulmonary Hypertension on Surgical PDA Ligation Outcomes in Preterm Neonates

Background: Pulmonary hypertension (PH) increases mortality in infants with bronchopulmonary dysplasia (BPD). As practice has shifted towards expectant management of patent ductus arteriosus (PDA), there is limited data guiding treatment with PH. Methods: Retrospective single center cohort study of neonates <32 weeks gestation who underwent surgical PDA ligation before discharge. Ductal gradients by echocardiogram defined PH severity: severe PH as bidirectional/ right to left shunting, mild-to-moderate PH as greater than half-systemic pressure, no PH as less than half-systemic pressure. Primary outcome was mortality. Secondary outcomes were length of stay (LOS), duration of ventilation, post-operative inotropes, steroids, systemic pulmonary vasodilators, and incidence of BPD. Results: Eighty patients, median gestational age 25 (23-31) weeks, underwent surgical PDA ligation between 2010-2016. Ten had severe PH, 54 mild-to-moderate PH, and 16 no PH. Severe PH group had significantly longer LOS, 173 vs. 143 days (p=.05). PH cohort had higher surgical weight, 1.71 kg vs. 1.06 kg (p=0.04). All deaths occurred in the PH group (6% vs. 0%), p=NS. No significant difference in ventilation, inotropes, steroids, pulmonary vasodilators, and BPD. Although, statistically insignificant, the PH group had higher rates of tracheostomies (18.8% vs. 6.25%). Conclusion: Premature infants requiring PDA ligation with severe PH had longer overall LOS. All mortality occurred in the PH group. More data is needed to determine effect of PDA on lung disease and the development of PH.

Ingestion of Caffeine and Carbohydrate Increases Average Power Output during a 10 mile Time Trial in Both Male and Female Cyclists

Previous researchers observed that elite male cyclists’ performance improves with combined ingestion of caffeine and carbohydrate. We carried out this study to determine if similar outcomes would be observed in a group of cyclists varying widely in age and racing experience as well as gender. We administered carbohydrate with or without the addition of 6 mg/kg body weight caffeine in a counterbalanced blind manner to ten trained male and female cyclists in the fed state one hour prior to 20 minutes of steady-state (SS) cycling at 60% VO2max power followed by a simulated 10-mile time trial (TT). Ventilation (VE), rate of oxygen consumption (VO2), respiratory exchange ratio (RER), and rate of perceived exertion (RPE) were measured during the SS, whereas completion time, average power output, heart rate (HR) and RPE were measured during the TT. The addition of caffeine resulted in a significant reduction in completion time (1.9%) and increased the average power output (5.0%), as well as significantly higher heart rates during the TT (2.9%). We observed no significant differences in VE, VO2, RER, RPE, and HR during the SS between treatments. Our data shows that the ingestion of 6 mg/kg of caffeine in combination with a 7.5% carbohydrate solution in male and female cyclists in the fed state improves short duration time trial performance as measured by completion time and average power output. These findings can be of great value to cyclists across a wide range of age and experience.

Influence of estrous cycle hormonal fluctuations and gonadal hormones on the ventilatory response to hypoxia in female rats.

Sex hormones may influence many physiological processes. Recently, we demonstrated that hormonal fluctuations of cycling female rats do not affect respiratory parameters during hypercapnia. However, it is still unclear whether sex hormones and hormonal fluctuations that occur during the estrous cycle can affect breathing during a hypoxic challenge. Our study aimed to evaluate respiratory, metabolic, and thermal responses to hypoxia in female rats on different days of the estrous cycle (proestrus, estrus, metestrus, and diestrus) and in ovariectomized rats that received replacement with oil (OVX), estradiol (OVX+E2), or a combination of estradiol and progesterone (OVX+E2P). Ventilation (V E), tidal volume (V T), respiratory frequency (fR), oxygen consumption (VO2), and V E/VO2 were not different during the estrous cycle in normoxia or hypoxia. Body temperature (Tb) was higher during estrus, but decreased similarly in all groups during hypoxia. Compared with intact females in estrus, gonadectomized rats also had lower Tb in normoxia, but not in hypoxia. OVX rats experienced a significant drop in the ventilatory response to hypoxia, but hormonal replacement did not restore values to the levels of an intact animal. Our data demonstrate that the different phases of the estrous cycle do not alter ventilation during normoxia and hypoxia, but OVX animals display lower ventilatory responses to hypoxia compared with ovary-intact rats. Because estradiol and progesterone replacement did not cause significant differences in ventilation, our findings suggest that a yet-to-be-defined non-steroidal ovarian hormone is likely to stimulate the ventilatory responses to hypoxia in females.

The Effect Of Ischemic Preconditioning On Pulmonary Pressure And Gas Exchange During Exercise In Hypoxia

Elevations in pulmonary vascular pressure are common at high altitude and can influence respiratory gas exchange. PURPOSE: The purpose of this study was to determine the role of acute ischemic preconditioning (IPC) on pulmonary vascular pressures and gas exchange during hypoxic exercise in healthy individuals. METHODS: A total of 12 healthy subjects were randomly assigned to either treatment group (n=6, 22.4±4.2yrs) or the sham group (n=6, 27.3±9.7yrs). Pulmonary vascular pressure was estimated from right ventricle systolic pressure (RVSP) and mean pulmonary artery pressure (mPAP) via echocardiograph (General Electric, Duluth, GA). In addition, minute ventilation (VE), end tidal CO2 (PETCO2) and breathing efficiency for CO2 (VE/VCO2) were measured breath-by-breath (MGC Diagnostics, Saint Paul, MN). For baseline measurement, subjects exercised at 30W on an echocardiograph-ergometer (Ergoline, Germany) during hypoxia (FiO2=~12.5%) followed by IPC treatment. Between baseline measurement and IPC treatment, a 90min washout period was applied. For IPC, an arm cuff was placed on the upper arm and the procedure included 4 cycles of alternating between 5min inflation and 5min deflation. The cuff pressures were 200mmHg for the treatment group and 20mmHg for the sham group. Following treatment or sham, both groups rested for 90min and post measurements were made. RESULTS: The treatment group demonstrated a trend towards an improved RVSP (-28.8±27.5% vs. -1.1±20.8% respectively, p=0.055) and mPAP (-11.30±16.2% vs. 13.8±23.8% respectively, p=0.057) but sham did not. However, no significant difference in VE, PETCO2 and VE/VCO2 between groups was observed (p>0.05). CONCLUSION: In this small preliminary study, IPC reduced pulmonary vascular pressure during hypoxic exercise, however, it was not associated with altered respiratory gas exchange.

Anatomic Variations in Pulmonary Perfusion and Ventilation Per Quantitative MAA and DTPA SPECT/CT in Patients Receiving Thoracic Radiation Therapy

Anatomic Variations in Pulmonary Perfusion and Ventilation Per Quantitative MAA and DTPA SPECT/CT in Patients Receiving Thoracic Radiation Therapy

Maximal and Ventilatory Thresholds Cardiorespiratory Responses to Three Water Aerobic Exercises Compared With Treadmill on Land

The purpose of this study was to compare the cardiorespiratory responses of young women to exercise at the first ventilatory threshold (VT1), the second ventilatory threshold (VT2), and at maximum effort (MAX) between maximal incremental tests performed using water aerobic exercises and a treadmill on land (TL). Twenty women (24.0 ± 2.5 years; 163.3 ± 6.7 cm; 60.0 ± 6.7 kg) underwent 4 maximal tests in randomized order, with a 48-hour interval between tests. Three tests involved performing water aerobic exercises (stationary running, frontal kick, and cross-country skiing) and 1 TL. Oxygen uptake (VO2), ventilation (VE), and heart rate were measured throughout the tests, and their values at the VT1, VT2, and MAX intensities were determined by 3 independent, experienced physiologists. Repeated measures analysis of variance with Bonferroni post hoc tests were used for comparisons between tests (α = 0.05). Heart rate was significantly higher in the TL condition compared with the water aerobic exercises at the VT1 (p = 0.001), VT2 (p < 0.001), and MAX (p < 0.001) intensities. VO2 and VE had similar values across the 4 protocols at the VT1 intensity, but significantly higher values were observed with TL (VO2: p < 0.001; VE: p < 0.001) at the VT2 intensity. At the MAX intensity, VO2 was significantly higher with TL compared with the 3 water aerobic exercises (p < 0.001), whereas no significant differences in VE between the 4 protocols were found. These results suggest that the prescription of water aerobics classes should be based on specific maximal tests for water aerobic exercises. Training intensities could be overestimated if they were based on maximal tests on dry land.

The Effect of Pre-exposure to Diluted Diesel Exhaust on 20km Cycling Time Trial Performance

Particulate matter air pollution (PM) causes lung inflammation, systemic inflammation and endothelial dysfunction, however the effect of PM on endurance performance is unknown. With international sports competitions being held in cities with high levels of PM, it is important to understand the physiological and performance implications of this. PURPOSE: Determine the effect of pre-exposure to dilute diesel exhaust (DE) on 20km time trial (TT) performance, cardio-respiratory responses during exercise and lung function. METHODS: Seven endurance-trained males (mean ± SD; VO2max of 68.0 ± 9.0 mL·kg-1·min-1, age: 28.3 ± 5.9 yr, height: 178.8 ± 10.2 cm, weight: 71.0 ± 3.0 kg) participated. They attended on 3 separate occasions. Day 1 consisted of a maximal exercise test; days 2 and 3 included a 60-minute exposure followed be a 20km TT. Days 2 and 3 exposures were blinded and randomized to filtered air (FA) or DE containing PM2.5 (particles with a diameter of <2.5 microns) at a concentration of 300ug/m3. Pulmonary function was assessed immediately prior to and 30 minutes post-exposure, and 30 minutes post-exercise. Minute ventilation (VE) tidal volume (Vt) and breathing frequency (Fb,) were collected during the TTs. Duration, mean and peak power were analysed using paired T-tests; repeated measures ANOVA were used to assess the effect of exposure on physiological measures: pulmonary function was analysed using condition (DE vs. FA) and time (pre-exposure, post-exposure, post-TT); ventilatory data and heart rate during time trial performance were analysed using condition (DE vs. FA) and time (quartile 1, 2, 3 and 4 of the time trial). RESULTS: There were no significant differences in time trial duration (33.2 ± 1.4 min vs. 32.6 ± 0.9 min), mean power output (253.1 ± 29.1w vs. 262.9 ± 20.34w), peak power output (436.4 ± 167.6w vs. 467.1 ± 139.6w) between the FA and DE condition respectively. There were no significant differences in VE, Vt and Fb between tests. There was a trend for heart rate to be higher following DE compared to FA (p=0.057; Q1: 150.0 ± 11.1 vs. 155.1 ± 15.1, Q2: 157.0 ± 11.1 vs. 164.9 ± 12.6, Q3: 158.9 ± 14.7 vs. 167.4 ± 13.2, Q4: 169.6 ± 18.2 vs, 171.9 ± 12.6 bpm for FA and DE respectively). CONCLUSION: A 60-minute pre-exposure to 300ug/m3 PM does not significantly impair 20km time trial cycling performance in endurance athletes.

Comparison of the Sensormedics® 3100A and Bronchotron® transporter in a neonatal piglet ARDS model

The Sensormedics 3100A (Cardinal Health, Dublin, OH) (HFOV) and the Bronchotron (Percussionaire, Sandpoint, ID) (HFPV) are high-frequency ventilation devices used to support neonatal respiratory failure; however, a comparison of the devices, with respect to gas exchange at similar ventilator settings, has not been previously studied. Thus, we compared the ability of HFOV to that of HFPV to provide oxygenation and ventilation during acute lung injury in a newborn animal model. Using a saline lung lavage model, 12 neonatal piglets were randomized to initial support with either the HFOV or HFPV with settings adjusted to achieve PaCO2 of 45-60 mmHg. After stabilization, ventilator settings and arterial blood gases were serially recorded for 30 min. Animals were then crossed over to the alternative device set to deliver the same V(t), MAP, and F for an additional 30 min with the same parameters recorded. We found that the DeltaP needed to generate adequate V(t) on HFPV (35 +/- 7 cm H2O) trended higher versus HFOV (31 +/- 7 cm H2O P = 0.09) when the devices were matched for V(t), F, and MAP. No significant differences in ventilation (PaCO(2) = 50 +/- 10.7 mmHg vs. 46 +/- 10 mmHg, P = 0.22) or oxygenation (PaO2 = 150 +/- 76 mmHg vs. 149 +/- 107 mmHg, P = 0.57) between the devices were found. We conclude that HFPV ventilates and oxygenates as well as HFOV at equivalent ventilator settings. HFPV may require larger DeltaP's to generate equivalent V(t).

Use of dynamic CT in acute respiratory distress syndrome (ARDS) with comparison of positive and negative pressure ventilation

Negative pressure ventilation via an external device ('iron lung') has the potential to provide better oxygenation with reduced barotrauma in patients with ARDS. This study was designed to see if oxygenation differences between positive and negative ventilation could be explained by CT. Six anaesthetized rabbits had ARDS induced by repeated saline lavage. Rabbits were ventilated with positive pressure ventilation (PPV) and negative pressure ventilation (NPV) in turn. Dynamic CT images were acquired over the respiratory cycle. A computer-aided method was used to segment the lung and calculate the range of CT densities within each slice. Volumes of ventilated lung and atelectatic lung were measured over the respiratory cycle. NPV was associated with an increased percentage of ventilated lung and decreased percentage of atelectatic lung. The most significant differences in ventilation and atelectasis were seen at mid-inspiration and mid-expiration (ventilated lung NPV = 61%, ventilated lung PPV = 47%, p < 0.001; atelectatic lung NPV = 10%, atelectatic lung PPV 19%, p < 0.001). Aeration differences were not significant at end-inspiration. Dynamic CT can show differences in lung aeration between positive and negative ventilation in ARDS. These differences would not be appreciated if only static breath-hold CT was used.

Standard Versus Over-the-Head Cardiopulmonary Resuscitation During Simulated Advanced Life Support

Background. Limited space can make rescuer position changes difficult during cardiopulmonary resuscitation (CPR). Over-the-head (OTH) CPR enables one rescuer to deliver chest compressions andventilations without changing position. The aim of the present study was to evaluate quality of OTH versus standard CPR with bag-valve-mask (BVM) ventilation in a manikin model during advanced life support (ALS). Method. In a randomised double-crossover trial, eight paramedic students performed ALS using both OTH andstandard CPR with BVM. Initial rhythm was asystole, converting to ventricular fibrillation after atropine, adrenaline, andCPR. Data collection was stopped after atropine andepinephrine had been given. Data are presented as means ± SD or median with 25% and75% percentile. Results. There were no significant differences in ventilation or compression variables or any time factors with median total hands off times of 50% versus 52% for OTH andstandard CPR respectively. Conclusion. OTH CPR is an alternative method during CPR.

Hyperventilation and asymptomatic chronic asthma

BACKGROUNDWe have consistently argued that mild asthma is an important underlying aetiological factor in patients with severe symptomatic hyperventilation. While hyperventilation has been demonstrated in acute asthma, there have been...

Validation of a 5-minute steady state indirect calorimetry protocol for resting energy expenditure in critically ill patients.

Numerous protocols are used for indirect calorimetry in research and clinical settings. The objective of the current study was to validate in critically ill patients an abbreviated protocol that uses five consecutive stable 1-minute readings of oxygen consumption (VO2), carbon dioxide production (VCO2), and minute ventilation (VE) in a range of +/- 5%, versus a more standard protocol that uses 30 consecutive stable one minute readings of VO2, VCO2, and VE in a range of +/- 10%. Indirect calorimetry was performed on resting, mechanically ventilated, critically ill patients. The first 5-minute period in which coefficients of variation for VO2, VCO2, and VE were < or = 5% was compared to the first 30-minute period in which coefficients of variation for these variables were < or = 10%. Thirty-four critically ill patients were studied. Twenty four patients (70%) successfully completed both protocols (Success Group). Eighteen percent of subjects completed neither the abbreviated nor the 30 minute protocol, and 12% completed only one protocol (Fail Group). The Success Group was marked by a higher incidence of sedation and/or medical paralysis. There were no significant differences in VE, VO2, VCO2, respiratory quotient, or energy expenditure between the protocols in the Success Group or the Fail Group. Coefficients of determination (R2) for VO2 and VCO2 between the two methods in the Success Group were 0.99. In the Fail Group, R2 values ranged from 0.75 for VCO2 to 0.91 for VO2. In sedated, mechanically ventilated patients, an indirect calorimetry test of five consecutive 1-minute periods with coefficient of variation < or = 5% is equivalent to a longer test consisting of 30 consecutive 1-minute periods with coefficient of variation < or = 10%.

Failure of hyperoxic gas to alter the arterial lactate anaerobic threshold.

Oxygen-enriched gases enable patients and healthy individuals to exercise submaximally with reduced lactate concentration, lower minute ventilation (VE), and less subjective stress compared to normoxia. These findings suggest that hyperoxia may raise the lactate accumulation threshold, also known as the anaerobic threshold (AT). This study measured the anaerobic threshold by gas exchange (Gx-AT) and arterial lactate (Lac-AT) methods in normoxia (FIO2 = 0.209) and the Lac-AT in hyperoxia (FIO2 = 0.40). Eight healthy males (age = 30.6 +/- 3.5 years; weight = 73.4 +/- 5.2 kg; VO2max = 41.3 +/- 6.6 mL/kg/min) worked incrementally (25 Watts [W] x 2 minutes) on a cycle ergometer with the legs on three occasions: once in normoxia, twice in hyperoxia. The latter situation enabled a reliability analysis of hyperoxic anaerobic threshold by arterial lactate methods that yielded a correlation coefficient (r) of 0.94 and nonsignificant paired t-ratio. Gas exchange and arterial lactate methods of detecting the anaerobic threshold in normoxia yielded nearly identical VO2 (21.8 +/- 5.4 mL/kg/min vs 21.5 +/- 5.5 mL/kg/min) with an r of 0.98. Contrary to the study's hypothesis, the normoxic Lac-AT (134.4 +/- 35.2 W), expressed in power output at which the lactate threshold occurred, was not significantly different with hyperoxic gas (128.1 +/- 32.7 W). Furthermore, arterial lactate concentration at the breakpoint in normoxia (1.74 +/- 0.50 mmol.l-1) was not significantly affected by hyperoxia (1.68 +/- 1.03 mmol.l-1) nor was it different between the two hyperoxic tests. No significant differences in VE, HR, or CO2-ventilation equivalent at Lac-AT were found between the two FIO2 conditions. The elevation of estimated PaO2 to 200 mm Hg does not alter the Lac-AT, compared to the normoxic condition, nor does it affect the arterial lactate concentration at its systematic break point in incremental cycling. Lac-AT is a reliable measurement and it can be estimated accurately using the VE/VO2 in conjunction with VE/VCO2.

Effect of raised potassium on ventilation in euoxia, hypoxia and hyperoxia at rest and during light exercise in man.

The purpose of this study was to determine whether changes in arterial plasma potassium concentration [K+]a affect expired ventilation (VE) in euoxia, hypoxia and hyperoxia during rest and light exercise in humans. Three periods of ventilatory measurements were undertaken in eight healthy subjects at rest and in seven other subjects during cycle ergometry (70 W). The first period of measurement was before the ingestion of 64 mmol of potassium chloride (KCl), the second 20 min after ingestion of KCl when [K+]a levels were elevated, and the third 3 h after the ingestion of KCl when [K+]a had returned substantially to normal. During each period, end-tidal PO2 was cycled between euoxia, hypoxia and hyperoxia, whilst the end-tidal PCO2 was maintained constant. The acute ventilatory response to hypoxia (AHVR) was calculated as the difference in VE during hypoxia and hyperoxia within each period of measurement. Oral KCl produced a 1.3 +/- 0.2 mM (mean +/- S.E.M.) increase in [K+]a at rest and a 0.8 +/- 0.2 mM increase during exercise. There was no significant difference in ventilation during euoxia between the three periods of measurement at rest or during exercise. There was a significant increase in AHVR with the rise in [K+]a of 21 min-1 mM-1 at rest (arterial PO2 during hypoxia ca 57 Torr) and 10 l min-1 mM-1 during exercise (arterial PO2 during hypoxia ca 52 Torr). There was a significant difference in the absolute increase in AHVR with [K+]a between rest and exercise, but this difference was not significant if the increase in AHVR with [K+]a was expressed as a percentage of the initial AHVR. We conclude that changes in [K+]a of the order of 1 mM have little effect on euoxic ventilation at rest or during light exercise in humans. We also conclude that [K+]a changes of this order increase AHVR at rest and during light exercise and that increases in [K+]a contribute to the increase in AHVR with exercise in humans.

Oxygen consumption using the K2 telemetry system and a metabolic cart

The purpose of this study was to compare measurements of oxygen consumption (VO2), ventilation (VE), and respiratory rate (RR) between a relatively new portable, telemetry system (K2) and a system that has been shown to be valid and reliable. Duplicate measurements were made at rest and during four levels of exercise in 10 subjects. Heart rate values were comparable for exercise at the same work level during gas collection using the two systems, indicating that the metabolic stresses were similar. Oxygen consumption measurements were significantly lower using the K2 system compared with a metabolic measurement cart (MMC). There was no significant difference in VE, but RR was lower for measurements made with the MMC. Compared with the MMC, the K2 system uses a slightly different formula to calculate VO2 because the content of carbon dioxide in expired air is not measured. To determine differences resulting from the method of calculating VO2, MMC measurements were applied to the formula used by the K2 system, and K2 values were adjusted using the RER values obtained from the MMC. There were no differences between these calculated values and the values obtained directly from either the MMC or the K2 system. Consequently, we concluded that the lower VO2 values obtained with the K2 system were attributed to the method of collecting and analyzing expired air, rather than to the method of calculating VO2.

Hypoxia does not increase CSF or plasma beta-endorphin activity.

The ability of moderate (30-50 Torr arterial PO2) and severe (less than 30 Torr arterial PO2) hypoxia to generate endogenous opioids that modulate ventilation was studied in unanesthetized goats. Ventilation and its components, arterial blood gas tensions and pH, and plasma and cerebrospinal fluid (CSF) beta-endorphin activity were measured before and after 4 h of sustained moderate or severe hypoxia. Ventilation, as expected, increased with hypoxia. There were no significant changes in either plasma or CSF beta-endorphin activity after sustained hypoxia. To rule out elaboration of endogenous opioids other than beta-endorphin after hypoxia, naloxone or saline was administered to five of the seven goats exposed to 4 h of severe hypoxia, and their ventilatory responses were compared for 30 additional min of hypoxic breathing. No significant differences in ventilation occurred in the two treatment groups during this time period. We conclude that, unlike increases in airway resistance, moderate and severe hypoxia do not cause the elaboration of endogenous opioids that modify respiratory output in unanesthetized adult goats. The apparent ability of hypoxia to cause elaboration of endogenous opioids in the neonate may represent a maturational phenomenon.

1377 VARYING FEEDING CONTAINER RIGIDITY: EFFECT ON INTAKE AND VENTILATION IN PRETERM INFANTS

Following observations that reducing milk container rigidity may help oral feedings, five preterm infants (x+SEM GA 33±1.2 wks, weight 1.7±0.1 kg, post-natal age 4.2±0.9 wks) were studied at sequential feeds with equal volumes of milk from two containers, rigid (R) and collapsible (C). Ventilation, sucking pressure, duration of feeding (DF) were measured. No significant difference in ventilation during sucking was found between containers. Nipple sucking pressure was significantly greater with R (12.1±0.9 cmH20, P<0.001) Suck-pause sucking pattern was clearly seen only with R, where pause occupied 21.7±2.8% of total time. Pause ventilation was similar to baseline. No significant difference in total airway closure time was found between containers. Result suggest that reducing the oral load decreasesingestion time without further impairment of ventilation, and maybe useful in aiding the oral feeding of preterm infants.

Expired air volumes of males and females during cold water immersion.

Expired air volumes were measured from a random population of adult male and female human volunteers before and during short-term immersion in either cold (13.53 +/- 0.13 degrees C) or warm (33.18 +/- 0.11 degrees C) water. A statistically significant difference was found in the pulmonary ventilation over the first 4 min of immersion between males and females when immersed in cold water. The swim suits worn could not account for the differences observed. No statistically significant difference in pulmonary ventilation was found between males and females during warm water immersion. A numerically smaller group of volunteers was preheated in a sauna before immersion in cold or warm water and this resulted in an attenuated ventilatory response. In this instance there is no statistically significant difference in ventilation between males and females. Also, in another small group of volunteers, surface and deep skin temperatures were continuously measured before and during immersion in cold water. The rates of change of deep skin temperature between males and females were found to be similar.