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C K Mahutte

Publications and source records attributed to C K Mahutte.

At least 37 records · Page 2Linked to original sources
PubMed1994

Variability of arterial blood gas values over time in stable medical ICU patients.

The spontaneous variability of arterial blood gas and pH values (ABGs) was examined in a group of 28 typical stable medical ICU patients under a variety of ventilatory conditions. In each patient, 13 ABG specimens were measured at 5-min intervals during a 1-h study period using a new bedside, extravascular fluorescent blood gas monitor. For all patients, the mean coefficient of variation (C) was 6.1 percent for PO2 and 4.7 percent for PCO2. The average SD for pH was 0.012. We conclude that the spontaneous variability for ABG values over a 1-h period is substantial and that this variability should be taken into account when making clinical decisions based on ABG values.

Adult↗
PubMed1994

Acquired laryngomalacia as a cause of obstructive sleep apnea.

We describe a patient who, 4 years after a radical neck dissection and radiotherapy, presented with obstructive sleep apnea; upon bronchoscopy, he was found to have acquired laryngomalacia. Inspiration induced upper airway obstruction due to a large flaccid epiglottis, large aryepiglottic folds, and edema of the supraglottic area. We suggest that acquired laryngomalacia can lead to obstructive sleep apnea. Patients with obstructive sleep apnea after radical neck dissection need to be evaluated for laryngomalacia with fiberoptic laryngobronchoscopy. Examination of the upper airway is useful to determine the nature and extent of any upper airway collapse.

Adult↗
PubMed1994

Influence of pressure- and flow-triggered synchronous intermittent mandatory ventilation on inspiratory muscle work.

OBJECTIVE: To determine the effect of pressure- and flow-triggered synchronous intermittent mandatory ventilation on inspiratory muscle work. DESIGN: Consecutive clinical, prospective, randomized trial. SETTING: Medical intensive care unit (ICU) of a U.S. Veterans Affairs Medical Center. PATIENTS: Eight patients recovering from acute respiratory failure of various etiologies. INTERVENTIONS: Assist control, followed by randomized application of pressure- and flow-triggered synchronous intermittent mandatory ventilation at 60%, 40%, 20% of the assist-control rate, and flow-triggered continuous positive airway pressure. A total of eight settings were maintained for 10 mins each. MEASUREMENTS AND MAIN RESULTS: Total work rate (joules/min), inspiratory muscle work (joules/L), and pressure time-product per breath (cm H2O-sec) were measured. During pressure- or flow-triggered synchronous intermittent mandatory ventilation, total work rate increased as the mandatory rate was decreased. The method of ventilator triggering had a significant effect on the total work rate. With pressure-triggered synchronous intermittent mandatory ventilation, the total work rate at 60% of the assist-control rate was similar to that with assist-control; whereas with flow-triggered synchronous intermittent mandatory ventilation, this result was achieved at 40% of the assist-control rate. At a machine support level of 20%, total work rate with pressure-triggered synchronous intermittent mandatory ventilation was significantly greater than with flow-triggered synchronous intermittent mandatory ventilation. The method of ventilator triggering had no significant effect on the inspiratory muscle work of the mandatory breaths. This finding was in contrast to the effect on inspiratory muscle work of spontaneous breaths. With pressure-triggered synchronous intermittent mandatory ventilation, inspiratory muscle work of the spontaneous breaths was greater than with the flow-triggered at machine support of 40% and 20%. With either pressure- or flow-triggered synchronous intermittent mandatory ventilation, inspiratory muscle work of the mandatory breaths was not significantly different from that of the corresponding spontaneous breaths, except at the lower machine support levels with the pressure-triggered synchronous intermittent mandatory ventilation. Pressure-time product followed a trend similar to that of inspiratory muscle work. CONCLUSIONS: During synchronous intermittent mandatory ventilation, the method of ventilator triggering has a significant effect on the total work rate and inspiratory muscle work of the spontaneous breaths, particularly at lower machine support levels. Conversely, the method of ventilator triggering has no significant effect on inspiratory muscle work of the mandatory breaths.

Acute Disease↗
PubMed1993

Experimental and predicted dual oximetry variability.

OBJECTIVE: We wished to determine whether the individual bias (mean difference) and precision (standard deviation of the difference) values of 2 variables, arterial oxygen saturation (SaO2) and mixed venous oxygen saturation (SvO2), could be used to predict the bias and precision values of the combined dual oximetry variable (SaO2-SvO2). METHODS: We simultaneously measured SaO2 by pulse oximetry and arterial blood gas co-oximetry and SvO2 by fiberoptic reflectance oximetry pulmonary artery catheter and venous blood gas co-oximetry in 238 data sets from 55 patients. Three different methods were used to predict the standard deviation of the difference of (SaO2-SvO2) [s delta(SaO2-SvO2)]: simple sum, root mean square (RMS) error, and RMS error with correction term. We derived the equation for the RMS error with correction term because initial results showed that the simple sum and RMS error methods did not predict s delta(SaO2-SvO2) well. The correction term accounts for the non-independence of simultaneous SaO2 and SvO2 measurements. RESULTS: The observed overall bias of the SaO2, SvO2, and (SaO2-SvO2) measurement methods were 0.17, -1.76, and 1.94, respectively. The observed overall s delta(SaO2-SvO2) of the (SaO2-SvO2) measurement method was 5.12. The simple sum method overestimated the actual s delta(SaO2-SvO2) by 38%, the RMS error method differed from the actual s delta(SaO2-SvO2) by 3%, and the RMS error with correction term method matched the actual s delta(SaO2-SvO2). CONCLUSION: The bias of a (SaO2-SvO2) measurement method is simply the bias of the SaO2 measurement method less the bias of the SvO2 measurement method. s delta(SaO2-SvO2) is best predicted by the derived equation, RMS error with correction term. The same principles and equations also apply to other situations in which 2 variables with the same dimensions are combined into 1 variable, such as (PaCO2-EtCO2) gradients and perfusion-pressure gradients. Although the difference between the s delta(SaO2-SvO2) predicted by the RMS error equation and the derived RMS error equation with correction term was small, the difference may be significant for other combined variables.

Oximetry↗
PubMed1993

Clinical performance of a blood gas monitor: a prospective, multicenter trial.

OBJECTIVE: To prospectively assess the clinical performance of a fluorescent optode-based blood gas monitoring system that is designed to perform arterial pH, PCO2, and PO2 measurements as frequently as clinically required without violating the integrity of the arterial catheter tubing system or permanently removing blood from the patient. DESIGN: A prospective, multicenter study to compare modern blood gas analyzer measurements with the coinciding measurements of the blood gas monitoring system. SETTING: Four intensive care units (ICUs) in academic centers with varying patient populations, blood gas measurement routines, and blood gas laboratory facilities. PATIENTS: Adult ICU patients (n = 117), with appropriately functioning radial arterial catheters in place, who were assessed as likely to require multiple arterial blood gas measurements for > or = 2 days. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 117 patients had 1,341 concurrent blood gas analyzer and monitor measurements of arterial pH, PCO2, and PO2 over a 1- to 4-day period. The range of values were 7.14 to 7.64 for arterial pH, 19 to 98 torr (2.5 to 13.0 kPa) for PaCO2, and 38 to 413 torr (5.1 to 54.9 kPa) for PaO2. Linear regression analysis of the optode-based monitor compared with the electrode-based blood gas analyzer demonstrated r2 values of .85 for pH, .92 for PCO2, and .94 for PO2. Comparative statistical analyses for bias (mean difference between analyzer and monitor) and precision (standard deviation of the mean difference [+/- SD] between analyzer and monitor) were respectively:-0.004 and +/- 0.027 for pH; -0.8 torr (-0.11 kPa) and +/- 2.4 torr (0.32 kPa) for PCO2; -2.2 torr (-0.31 kPa) and +/- 8.7 torr (1.2 kPa) for PO2. CONCLUSIONS: Clinical performance of this fluorescent, optode-based blood gas monitoring system demonstrates stability, consistency, and accuracy comparable to modern blood gas analyzers. This system withstood the normal abuse and rigors of clinical conditions common to the ICU while reliably performing in critically ill patients for up to 80 hrs. Use of the device did not significantly alter the function or longevity normally expected from a 20-gauge radial artery catheter. We submit that this blood gas monitoring system can replace the use of blood gas analyzers for ICU patients with indwelling arterial catheters.

Adolescent↗
PubMed1993

Effect of hypercapnia on the arousal response to airway occlusion during sleep in normal subjects.

The effect of an acute increase in PCO2 on the arousal response to occlusion of a mask covering the nose with the mouth sealed during non-rapid-eye-movement sleep was studied in six normal males aged 28.3 +/- 8.3 (SD) yr. Baseline occlusions, while subjects breathed a room air-O2 mixture adjusted to produce an arterial O2 saturation of 98%, were alternated with hypercapnic occlusions in which a small amount of 100% CO2 was added to increase the preocclusion end-tidal PCO2 by 3.5 +/- 0.59 Torr above the baseline value. The maximum deflections in supraglottic airway pressure (Pmax) were measured on the initial occluded breath (PmaxI) and the final breath preceding arousal (PmaxF). In the hypercapnic occlusions, the time to arousal was shorter (23.7 +/- 13.9 vs. 35.2 +/- 15.9 s, P < 0.03) and PmaxI and rate of change in Pmax were higher. However, the PmaxF in the baseline (20.2 +/- 4.1 cmH2O) and hypercapnic occlusions (20.4 +/- 4.4 cmH2O) did not differ. We conclude that an increase in PCO2 before airway occlusion shortens the time to arousal by increasing the initial occluded inspiratory effort (suction pressure) and the rate of increase in effort but does not change the arousal threshold.

Adolescent↗
PubMed1993

Airway occlusion pressure and breathing pattern as predictors of weaning outcome.

Airway occlusion pressure (P0.1) and the ratio of breathing frequency (f) to tidal volume (VT) (f/Vt) are good predictors of weaning outcome. However, the specificity of f/VT in predicting weaning success is relatively low. We postulated that the product of P0.1 and f/VT (P0.1*f/VT) would better predict weaning outcome than either variable alone. In 45 male patients, we prospectively evaluated P0.1*f/VT, P0.1, and f/VT in predicting weaning outcome. The threshold values of each variable were determined from published data. The sensitivity, specificity, and positive and negative predictive values in detecting weaning success, and the area under the receiver operating characteristic (ROC) curves were calculated. Ten (22%) of the 45 patients failed weaning. P0.1*f/VT yielded the highest specificity and positive and negative predictive values. P0.1*f/VT, P0.1, and f/VT were all highly sensitive (0.97); but they were less specific, 0.60 for P0.1*f/Vt and 0.40 for P0.1 and f/VT. The areas under the ROC curves for P0.1*f/VT, P0.1, and f/VT were not significantly different. We conclude that P0.1*f/VT has equivalent sensitivity as P0.1 and f/VT. P0.1 slightly improves the specificity of f/VT in predicting weaning success.

Acute Disease↗
PubMed1993

Does the hypoxic ventilatory response predict the oxygen-induced falls in ventilation in COPD?

The purpose of this study was to determine whether supplemental oxygen-induced decreases in ventilation (VE) and mouth occlusion pressure (P0.1) in patients with COPD are related to the ventilatory or P0.1 responses to hypoxia (delta VE/delta SaO2, delta P0.1/delta SaO2). We measured these responses in 14 patients with a (mean +/- SD) FEV1 of 0.95 +/- .41 L. The VE and P0.1 were also measured while the patients sequentially breathed either room air or supplemental oxygen (1-2 L/min) for 10 min in a randomized single blind fashion. The mean (+/- SEM) SaO2 increased from 90.8 +/- 0.99 percent to 95.2 +/- 0.46 percent and the VE decreased during oxygen breathing from 12.3 +/- 0.46 to 11.6 +/- 0.47 L/min (p < 0.03). However, the individual changes in VE were not significantly related to the corresponding changes in SaO2 (CHG SaO2), (delta VE/delta SaO2), or (delta VE/SaO2) (CHG SaO2). Similarly, the P0.1 decreased from 2.50 +/- 0.27 to 2.26 +/- 0.20 cm H2O (p < 0.05), but the individual changes in P0.1 were not significantly related to (CHG SaO2), (delta P0.1/delta SaO2), or (delta PO.1/delta SaO2) (CHG SaO2).

Aged↗
PubMed1993

Drug-induced pulmonary edema in a patient infected with human immunodeficiency virus.

Adverse reactions to drugs are common in patients infected with the human immunodeficiency virus (HIV). In these patients pulmonary reactions to drugs may be difficult to differentiate from opportunistic pulmonary infections. We report a HIV-infected patient who on two occasions developed acute pulmonary edema related to the administration of ibuprofen.

AIDS-Related Opportunistic Infections↗
PubMed1993

Relationship of thermodilution cardiac output to metabolic measurements and mixed venous oxygen saturation.

To determine the individual contributions of variables in the Fick equation to cardiac output, we simultaneously measured oxygen uptake (VO2), carbon dioxide production (VCO2), venous oxygen saturation (SvO2) and thermodilution cardiac output (Qth) in 28 medical and surgical ICU patients. Patients were intubated and ventilated with the intermittent mandatory ventilation mode. VO2 and VCO2 (averaged over 3 min) were obtained from a metabolic cart. SvO2 was measured with fiberoptic reflectance oximetry (and COoximetry). Thirty-nine studies (average duration, 4.3 h) with 151 Qth measurements were performed. The relationships between Qth and VO2, Qth and VCO2, Qth and SvO2, and 1/Qth and SvO2, as well as between the sequential changes in these variables were analyzed by least squares linear regression. The ability of changes in the variables VO2, VCO2, and SvO2 to predict changes in Qth were analyzed by receiver operating characteristic (ROC) curves. Qth was weakly related to VO2 (r = 0.45), VCO2 (r = 0.45), or SvO2 (r = 0.36). Changes in Qth were weakly related to changes in VCO2 (r = 0.40), and even less to changes in VO2 (r = 0.18) and SvO2 (r = 0.13). The areas under the ROC curves for increases in Qth > 10 percent were as follows: 0.66 for VCO2, 0.50 for VO2, and 0.55 for SvO2. The areas for decreases in Qth < 10 percent were as follows: 0.78 for VCO2, 0.65 for VO2, and 0.49 for SvO2. None of the above oximetry relationships were substantially altered by use of COoximetry venous oxygen saturations. We conclude that Qth cannot be predicted well solely from VO2, VCO2, or SvO2 nor can changes in Qth be predicted well solely from changes in VO2, VCO2, or SvO2. Of the metabolic variables, changes in VCO2 best predicted changes in Qth.

Carbon Dioxide↗
PubMed1992

Inspiratory muscle work of breathing during flow-by, demand-flow, and continuous-flow systems in patients with chronic obstructive pulmonary disease.

The effect of flow-by continuous positive airway pressure (CPAP) in comparison with continuous-flow (CF) CPAP on inspiratory muscle work of breathing (WI) in intubated patients is not known. We hypothesized that WI during flow-by CPAP would be comparable with that during CF CPAP. In nine intubated male patients recovering from acute respiratory failure related to chronic obstructive pulmonary disease, we compared the effects of flow-by, demand-flow, and CF CPAP on WI. We also evaluated the extent to which the addition of 5 cm H2O of pressure support to demand-flow CPAP (DF-PS5) decreases WI. At CPAP levels of zero and 8 cm H2O, flow-by, demand-flow, DF-PS5 were applied in random order followed by CF CPAP for 15 min each. WI (expressed as Joules per liter and Joules per minute), maximal airway pressure drop during inspiration (delta Paw), total lung resistance (RL), lung compliance (CL), and ventilatory variables were measured. At CPAP of zero cm H2O, WI with flow-by was comparable with CF CPAP, and significantly less than with demand-flow CPAP. At both CPAP of zero and 8 cm H2O, the addition of 5 cm H2O PS to demand-flow CPAP reduced WI significantly to a level comparable with that of flow-by CPAP. At both CPAP levels, delta Paw was the largest, with demand-flow CPAP. RL and CL were not significantly different between the different CPAP systems. We conclude that WI with flow-by CPAP is comparable with that with CF CPAP, and significantly less than with demand-flow CPAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Evaluation of a closed-system, directional-tip suction catheter.

INTRODUCTION: It is difficult to successfully suction the left bronchial tree. We evaluated the success rate of left bronchial cannulation with a new closed-suction directional-tip catheter (Trach Care directional-tip catheter, TCDT, Ballard Medical Products, Midvale UT). Success rates were compared in patients with endotracheal and tracheostomy tubes. We also studied the effects on success rate of (1) the distance of the endotracheal tube from the carina, (2) the tube's bevel orientation, and (3) the tube's position in the patient's mouth. METHOD: At the time of the routine daily chest radiograph, 75 attempts at left bronchial cannulation were made in 45 patients. With the head maintained in a midline position, the TCDT catheter was advanced with the radiopaque blue line in the 1 o'clock position. The radiograph was evaluated for correct placement of the TCDT catheter. RESULTS: Due to lung pathology and x-ray technique, catheter placement could not be interpreted in 17% of the radiographs. In the remainder, overall success rate was 71% (79% with tracheostomy tubes and 67% with endotracheal tubes, not significantly different, with p > 0.3). Tube distance from the carina and bevel orientation did not significantly affect success rates. Success rates for tubes located in the left and central positions of the patient's mouth were significantly better (p < 0.002 and p < 0.03, respectively) than for tubes located on the right side of the patient's mouth. With the endotracheal tube on the left side of the patient's mouth, the success rate was 89%. CONCLUSION: We conclude that the TCDT catheter successfully combines the features of a closed-suction system with those of a directional-tip catheter that allows selective bronchial cannulation, a large percentage of the time.

Bronchi↗
PubMed1991

Cardiac output from carbon dioxide production and arterial and venous oximetry.

OBJECTIVE: To determine cardiac output from measurements of CO2 production (VCO2), and arterial (SaO2) and mixed venous (SvO2) oxygen saturations, using a modified Fick equation, in which cardiac output = VCO2/[k (SaO2 - SvO2)], where k represents a constant. DESIGN: A metabolic measurement cart was used to measure VCO2 and oxygen consumption (VO2) at 3-min intervals. SaO2 and SvO2 were measured via a pulse oximeter and a fiberoptic right heart catheter, respectively. The initial value of k for each study was determined from initial simultaneous measurements of thermodilution cardiac output, VCO2, SaO2, and SvO2 via the equation k = VCO2/[cardiac output (SaO2 - SvO2)]. The value of k was assumed to remain constant for the entire study period. Thereafter, cardiac outputs calculated from k and the measurements of VCO2, SaO2, and SvO2 were compared with the simultaneously obtained cardiac outputs determined by thermodilution. Similarly, cardiac outputs calculated from the traditional oxygen Fick equation, where cardiac output = VO2/[13.4 x hemoglobin (SaO2 - SvO2)], were compared with the simultaneously acquired cardiac outputs determined by thermodilution. SETTING: Surgical ICU in a Veterans Affairs Medical Center. PATIENTS: Seven postoperative patients, mechanically ventilated using the intermittent mandatory ventilation mode, were studied over a mean period of 4 hrs. RESULTS: Cardiac output (obtained from VCO2 and oximetry saturations) was closely related to thermodilution cardiac output: with linear regression showing r2 = .96 and standard error of the estimate = 0.59 L/min, n = 21; and, with bias and precision = 0.17 and 0.68 L/min, respectively. The traditional oxygen Fick cardiac output was also closely related to the thermodilution cardiac output (r2 = .81, standard error of the estimate = 1.46 L/min, n = 22; bias and precision = 0.31 and 1.46 L/min, respectively). CONCLUSION: The proposed method for calculating cardiac outputs solely from VCO2 and oximetry saturations yields results that correspond closely to thermodilution determined cardiac outputs. The method is simple and avoids the difficulties in the Fick method associated with accurate VO2 measurement. This approach may be suitable for continuous cardiac output monitoring in critically ill patients.

Aged↗
PubMed1991

Pressure-time product during continuous positive airway pressure, pressure support ventilation, and T-piece during weaning from mechanical ventilation.

The objective of this study was to compare the effects of continuous positive airway pressure (CPAP), pressure support ventilation (PS), and T-piece on the pressure-time product (PTP) during weaning from mechanical ventilation. The PTP is an estimate of the metabolic work or oxygen consumption of the respiratory muscles. We studied 10 intubated patients recovering from acute respiratory failure of various etiologies. A modified continuous flow (flow-by) CPAP of 0 and 5 cm H2O (CPAP-0 and CPAP-5, respectively), PS of 5 cm H2O (PS-5), and T-piece were applied in random order for 30 min each. In the last 5 min of the 30-min periods, we measured the esophageal pressure and transdiaphragmatic pressure-time products--PTP(es) and PTP(di), cm H2O.s/min, respectively-multiplied by respiratory frequency. Breathing pattern, total lung resistance (RL), quasi-static lung compliance (CL), intrinsic positive end-expiratory pressure (PEEPi), end-expiratory transpulmonary pressure (Ptpexp), arterial blood gases, blood pressure, and heart rate were also measured. In comparison to T-piece, CPAP-5 decreased PTP(es) 40% (p less than 0.01) and PTP(di) 43% (p less than 0.02), whereas PS-5 decreased PTP(es) 34% (p less than 0.01) and PTP(di) 38% (p less than 0.05). The decrease in PTP(es) with CPAP-5 was associated with a significant reduction in RL, and to a less extent in PEEPi relative to airway pressure. The contribution of the decrease in PEEPi to the reduction in PTP(es) amounted to 36%. With PS-5, respiratory system mechanics and PEEPi were not significantly different compared with T-piece. With CPAP-0, PTP tended to be lower than with T-piece.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Progress in the development of a fluorescent intravascular blood gas system in man.

In vitro and in vivo animal studies have shown accurate measurements of arterial blood pH (pHa), carbon dioxide tension (PaCO2), and oxygen tension (PaO2) with small intravascular fluorescent probes. Initial human clinical studies showed unexplained intermittent large drops in sensor oxygen tension (PiO2). Normal volunteers were studied to elucidate this problem. In the first part of this study, the probe and cannula were manipulated and the probe configuration and its position within the cannula were varied. The decreases in PiO2 were judged to be primarily due to the sensor touching the arterial wall. Retraction of the sensor tip within the cannula eliminated the problem. In the second part of this study, the accuracy of the retracted probe was evaluated in 4 subjects who breathed varying fractions of inspired oxygen and carbon dioxide. The arterial ranges achieved were 7.20 to 7.59 for pH, 22 to 70 mm Hg for PaCO2, and 46 to 633 mm Hg for PaO2. Linear regression of 48 paired sensor (i) versus arterial values showed pHi = 0.896 pHa + 0.773 (r = 0.98, SEE = 0.017); PiCO2 = 1.05 PaCO2 - 1.33 (r = 0.98, SEE = 2.4 mm Hg); and PiO2 = 1.09 PaO2 - 20.6 (r = 0.99, SEE = 21.2 mm Hg). Bias (defined as the mean differences between sensor and arterial values) and precision (SD of differences) were, respectively, -0.003 and 0.02 for pHi, 0.77 and 2.44 mm Hg for PiCO2, and -2.9 and 25.4 mm Hg for PiO2. The mean in vivo 90% response times for step changes in inspired gas were 2.64, 3.88, and 2.60 minutes, respectively, for pHi, PiCO2, and PiO2.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

Two-beam pulsed Doppler cardiac output measurement: reproducibility and agreement with thermodilution.

Two observers used two-beam pulsed Doppler ultrasound, equipped with a suprasternal probe, to measure cardiac output (QtDopp) in 38 ICU patients who had pulmonary artery catheters and in 20 adult volunteers. The two-beam pulsed Doppler method enables one device to measure simultaneously both aortic blood velocity and aortic diameter. Each observer was blind to the other's measurement and to the thermodilution cardiac output measurement (Qttd). Linear regression of the mean of both observer's QtDopp on Qttd showed QtDopp = 0.90.Qttd + 0.01 (see = 1.54 L/min, r = .90). Bias (+/- SD), defined as mean (QtDopp - Qttd) difference, was -0.69 +/- 1.55 L/min. Interobserver agreement was more variable in patients than volunteers; mean (observer 1 - observer 2) difference was 0.14 +/- 1.30 L/min in ICU patients and -0.09 +/- 0.92 L/min in volunteers. Two-beam pulsed Doppler ultrasound is a simpler method of measuring QtDopp than previous pulsed Doppler methods which measure separately the aortic diameter by echocardiography. Although its agreement with Qttd is close to other Doppler methods and has acceptable interobserver reproducibility, its accuracy remains operator-dependent.

Cardiac Output↗
PubMed1990

Maximum inspiratory muscle endurance capacity during resistive loading in chronic obstructive pulmonary disease.

In 10 patients with stable severe chronic obstructive pulmonary disease (COPD) we evaluated the relationship between the degree of airway obstruction and hyperinflation, and the maximum inspiratory muscle endurance capacity during added inspiratory resistive loading. We measured the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) and airway resistance (Raw) as indices of airway obstruction, and the ratio of functional residual capacity to total lung capacity (FRC/TLC) as an index of hyperinflation. The mean resting transdiaphragmatic pressure to its maximum (Pdi/Pdimax), the tension time index of the diaphragm, and the maximum transdiaphragmatic pressure (Pdimax) were also determined. Following 15 min of resting breathing, the patients breathed through added inspiratory resistances which were progressively increased every 3 min until exhaustion. Maximum endurance capacity (ECmax) was defined as the product of the esophageal pressure - time integral and frequency at the maximum load sustainable for 3 min. ECmax correlated significantly with Raw (r = -0.67, p less than 0.04). The addition of FRC/TLC to the analysis resulted in a significant increase in the correlation coefficient (r = 0.86, p less than 0.01). ECmax did not correlate with FEV1/FVC. Both resting Pdi/Pdimax and Pdimax independently influenced ECmax. In addition, Pdimax correlated significantly with FRC/TLC, and resting Pdi/Pdimax with Raw. We conclude that in stable patients with severe COPD, both airway obstruction and hyperinflation affect maximum inspiratory muscle endurance capacity during inspiratory resistive loading.

Aged↗