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PubMed2003

Prediction of postoperative pulmonary complications on the basis of preoperative risk factors in patients who had undergone coronary artery bypass graft surgery.

BACKGROUND AND PURPOSE: Pulmonary complications are among the most frequently reported complications after coronary artery bypass graft (CABG) surgery. However, the risks of postoperative pulmonary complications (PPCs) are not equal for all patients. The aim of this study was to develop a model, based on preoperative factors, for classifying patients with high and low risks for PPCs in order to implement tailored interventions. SUBJECTS AND METHODS: Postoperative pulmonary complications were examined in 117 adult patients who had undergone elective CABG surgery at the University Medical Centre Utrecht, Utrecht, the Netherlands. The presence of preoperative risk factors (N=12) that have been described in the literature was noted for each patient. A risk model was developed by use of logistic regression analysis. RESULTS: Preoperative risk factors for developing PPCs were an age of (>/=70 years, productive cough, diabetes mellitus, and a history of cigarette smoking. Protective factors against the development of PPCs were a predicted inspiratory vital capacity of (>/=75% and a predicted maximal expiratory pressure of (>/=75%. These risk and protective factors were included in the model (sensitivity=87% and specificity=56%), and a sum score for its clinical use was generated. DISCUSSION AND CONCLUSION: Six factors that can be determined easily before surgery, with need for only simple pulmonary testing, can provide a model for identifying patients at risk of developing PPCs after CABG surgery.

Adult↗
PubMed2003

Use of inspiratory strength training to wean six patients who were ventilator-dependent.

BACKGROUND AND PURPOSE: Patients who are unable to wean from mechanical ventilation (MV) after resolution of critical illness or surgery risk increased morbidity and death and consume a disproportionate amount of intensive care unit resources. Decreased inspiratory muscle strength is often cited as a major factor contributing to prolonged MV. The purpose of this case report is to describe the rationale and application of inspiratory strength training (IST) as an adjunct to lengthen unassisted breathing trials and to ultimately wean patients with chronic mechanical ventilator dependency. CASE DESCRIPTION: Six patients who had been ventilator-dependent for 18 to 221 days (mean of 72 days) after surgery and were diagnosed with "failure to wean" performed low-repetition, high-resistance breathing exercises that were coupled with increasing time off the ventilator. OUTCOMES: All 6 patients were weaned from the ventilator in 9 to 28 days (mean of 17 days). The patients' training pressure increased from a mean of 9.3 cm/H2O to 27.5 cm/H2O, for an increase of 195%. The volitional maximum inspiratory pressure (MIP) increased from a mean of 22.5 cm/H2O to 54 cm/H2O, for a 140% gain in pressure. DISCUSSION: Although it is not clear why the patients appeared to benefit from IST, possible explanations include: (1) addressing inspiratory muscle pump dysfunction, (2) standardization of breathing patterns, 3) routinization of the patients' unassisted breathing trials, and (4) nonspecific training effects. Future research should address these possibilities when attempting to understand the effects of IST in the weaning of patients with chronic ventilator dependency.

Adult↗
PubMed2003

Peak inspiratory flow rate and the ability to use the Turbuhaler in Thai children aged 3-7 years.

A Turbuhaler is a dry powder inhaler device commonly used by asthmatic patients. Its superiority over a metered-dose inhaler device includes easy technique, convenience in handling and absence of chloro fluoro carbon (CFC). However, the use of this device has some limitations in young children who may not be able to generate the inspiratory flow rate high enough to assure adequate medication delivery. Even though the Turbuhaler has been used in Thailand for many years, the study of inspiratory flow rate and the ability to use this device in Thai preschool children is lacking. In the present study, the authors aimed to evaluate the ability to use the Turbuhaler in Thai preschool children by measuring the peak inspiratory flow rate, peak inspiratory flow rate through the Turbuhaler as well as positive test of the Turbutester. Subjects included 468 Thai preschool children, aged 3-7 years old. They were assigned to perform the test with In-Check Dial, Mini-Wright Peak Flow Meter and Turbutester. The authors found that the ability to use the device correlated directly with age and children with age of 5 years or more could perform significantly better. Children weight of 20 kilograms or more, or a height of 113 centimeters or more were also able to generate adequate inspiratory flow rate for medication delivery. The authors concluded that children from the age of five years, or with a weight from 20 kilograms or a height from 113 centimeters were able to generate adequate inspiratory flow rate for effective medication delivery by the Turbuhaler.

Aptitude↗
PubMed1992

Body composition of university students by hydrostatic weighing and skinfold measurement.

The body composition of 124 male and 70 female Tartu University students was measured by three different methods: hydrostatic weighing by maximal expiration, hydrostatic weighing by maximal inspiration and subcutaneous fat thickness measurements. Our results show that the proposed body density measuring method by maximal expiration is simple, reliable and applicable not only in indoor swimming pools but in field conditions as well. The second new hydrostatic weighing apparatus is more comfortable for the subjects where the body density is measured at maximal inspiration. The mean body density of males was somewhat higher when measured by the maximal inspiration (1.066 +/- 0.012 g.ml-1) than when measured by the maximal expiration (1.063 +/- 0.009 g.ml-1, p < 0.05). For females, on the contrary, the maximal expiration method (1.044 +/- 0.010 g.ml-1) yielded a higher body density value than when measured by the maximal inspiration (1.040 +/- 0.011 g.ml-1, p > 0.05). The body fat percentage measured by skinfold thickness correlated significantly with the body fat percentage calculated by body density by maximal expiration (males r = 0.420, females r = 0.531) and inspiration (males r = 0.507, females r = 0.663). We must conclude that the presented two methods of measuring body density offer new possibilities for densitometric analysis without the need for expensive laboratory equipment.

Adult↗
PubMed1992

[The effect of rapid changes in lung volume on the postinspiratory phase of the respiratory cycle in decerebrate cats].

In decerebrated cats, fast blowing of the lungs decreased the duration of inspiration, the amplitude of the diaphragmatic nerve ENG, and increased the duration of the second phase of expiration. The duration of postinspiratory phase was increased in proportion to changes in lung volume. Bilateral vagotomy induced a complete disappearance of the reflex responses.

Abdominal Muscles↗
PubMed1992

Nasal positive pressure ventilation in the treatment of chronic hypercapnic respiratory failure: a case report.

This paper describes the use of a nasal mask to deliver intermittent positive pressure ventilation to treat chronic respiratory failure in one patient with severe kyphoscoliosis. After two months of overnight nasal ventilation at home the patient achieved normal blood gases, showed improved inspiratory muscle strength, effort tolerance and was able to return to work. Intermittent nasal ventilation is a safe and effective ventilatory support modality for some patients with hypercapnic respiratory failure.

Adult↗
PubMed1992

Inspiratory spirogram in emphysema.

Bronchodilator therapy on inspiratory indices has not been documented so far. Reduction in inspiratory airflow resistance following inhalation of bronchodilator giving the most consistent and significant changes in emphysematous patients has been demonstrated in the present study.

Administration, Inhalation↗
PubMed2004

Correction of error in respiratory resistance measurements made with the flow-interruption technique during mechanical ventilation: evaluation of the puritan bennett 7200 and 840 ventilators.

BACKGROUND: Calculation of total inspiratory resistance (Rtot) for patients on ventilatory support is typically based on measurement of airflow velocity and airway opening pressure during end-inspiratory occlusion by the inspiratory valve in the ventilator. Systematic error is introduced into Rtot measurements because the inspiratory valve closes over a period of time (not instantaneously, so gas continues to flow into the circuit while the valve is shutting) and because the circuit tubing is a distensible compartment between the occluding valve and the respiratory system. The Rtot-measurement error can be minimized with a rapidly-shutting occlusion valve positioned at the airway opening, or, alternatively, by mathematical correction that accounts for the valve-closure period and circuit tubing characteristics. METHODS: In a bench study we measured Rtot with the Puritan Bennett 7200 and 840 ventilators (using the inspiratory valves that are built into those ventilators) and compared those measurements to measurements made with a rapidly-shutting valve at the airway opening. We deemed the rapid-occlusion-valve measurements the best available (benchmark) values. We also studied the closure characteristics of the ventilators' inspiratory occlusion valves and created equations for mathematical correction of Rtot values measured with those valves. RESULTS: Compared to the benchmark measurements, the measurements from the Puritan Bennett 7200 averaged 23.2% relative error and 2.6 cm H2O/L/s absolute error. Measurements from the Puritan Bennett 840 averaged 7.3% relative error and 1.0 cm H2O/L/s absolute error. Mathematical correction for the circuit tubing and valve-closure time reduced the average relative and absolute error to 3.0% and 0.4 cm H2O/L/s, respectively, for the Puritan Bennett 7200, and to 4.5% and 0.3 cm H2O/L/s, respectively, for the Puritan Bennett 840. CONCLUSIONS: The Puritan Bennett 840 measures Rtot more accurately than the Puritan Bennett 7200. Our equations to mathematically correct Rtot measurements made with the PB7200 and PB840 are useful in settings where very accurate Rtot measurements are necessary.

Airway Resistance↗
PubMed2004

[Pulmonary function results in healthy subjects breathing through external stenoses compared to patients with airway obstruction].

We compared body plethysmographic data, flow-volume curves during spontaneous breathing, P0.1 and PETCO2 in healthy subjects breathing through external stenoses (ES) of varying magnitude to the results in patients suffering from chronic obstructive pulmonary disease (COPD). Inspiratory vital capacity (IVC) remained unchanged by experimental airway stenoses. IVC is mainly determined by the end-expiratory closure of the airways, which only weakly correlates with airway resistance in patients. External stenoses had no effect on the physiological end-expiratory closure of the airways. For the other spirometric parameters the available force of the respiratory muscles and the degree of the experimental stenosis played the major role. The mouth occlusion pressure (P0.1) showed considerably lower variation during ES as well as in COPD patients than total resistance (Rt). There was no increase in intrathoracic gas volume (IGV) causing increased tension of the lungs and the thorax during ES. The well-known correlation between Rt and IGV is attributed to the end-expiratory closure of the airways during increased flow resistance and to "trapped air". It remains open, if and how the expiratory muscles act to overcome the increased resistance. With consideration of the underlying factors of the different lung function measures, the combination and the analysis of the correlation between different values may lead to far-reaching results in lung function testing.

Adult↗
PubMed1992

Vector analysis in partitioning of inspiratory muscle action in dogs.

We considered the displacements and the pressure changes resulting from isolated contraction of 2 muscles as analogous to 2 vectors and those during simultaneous contraction as resultants. These were resolved into contributing components to calculate the contribution of each muscle group and partition the action of inspiratory muscles. Relative displacements of rib cage (delta RC) and abdomen (delta AB) and changes in transpulmonary (delta PL) and abdominal (delta Pab) pressures were obtained during spontaneous breathing, isolated contraction of rib cage muscle (RCM), diaphragmatic (DI), costal and crural diaphragm and passive inflation in 7 dogs. The diaphragm accounted for 58 +/- 19.8% SD of the chest wall displacement and 90 +/- 6.6% SD of the pressure swings during spontaneous breathing. The costal diaphragm accounted for 61 +/- 28.9% SD of the displacement produced by contraction of the entire diaphragm. Despite wide variability in the action of the diaphragm and its components, all animals breathed close to their relaxation characteristic. We conclude that there are marked differences in the degree of RCM recruitment between dogs in order to prevent chest wall distortions.

Animals↗
PubMed2000

Pulmonary flow loop.

Pulmonary flow loops display characteric patterns which may indicate the underlying pathology of airway or parenchymal lung disease.

Airway Obstruction↗
PubMed1992

[Pulmonary mechanism in preterm neonates without respiratory problems].

Pulmonary function was measured by computerized pneumotacography in 26 preterm-newborn infants without respiratory problems. Mean (+/- SD) for birth weight, gestation and postnatal age were 2,034 +/- 412 g, 34.1 +/- 1.7 weeks, and 2.2 +/- 1.6 days, respectively. An esophageal balloon, a differential transducer and nasal prongs were used to measure pressure and flow. The following parameters were measured in each respiration by the mean squares method: Dynamic compliance (Cdyn), total respiratory resistance (RRt) and work (WRt), respiratory time constant (KTt), rate (f) and maximal inspiratory and expiratory flows (PIF, PEF). Replication of the method was found to be good, as the differences between two determinations were not significant (p less than 0.05). The mean differences were less than 6.26%. The mean (+/- SD) and the 3rd and 97th percentiles for each parameter were the following: f: 52 +/- 7 (39-66) r.p.m., Tv: 6.6 +/- 1.1 (4.5-8.7) ml/kg, Vmin: 342 +/- 82 (128-502) ml/min, Cdin: 3.7 +/- 1.1 (1.5-6) ml/cm, RRt: 83 +/- 47 (37-204) cm/L/sec, TRt: 27 +/- 15 (2-57.1) g/cm/kg, PIF: 2.2 +/- 0.5 (1.1-3.2) L/min and PEF: 1.9 +/- 0.6 (0.7-3) L/min.

Airway Resistance↗