Mechanics of Breathing, Gas Distribution and Functional Residual Capacity at Different Frequencies of Respiration During Spontaneous and Artificial Ventilation

Hedenstierna, Göran; McCarthy, Graham

doi:10.1093/bja/47.6.706

Cited by 37 publications

(11 citation statements)

References 20 publications

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“…However, no flow limitation was detected before surgery, suggesting the absence of severe lung disease. In addition, none of the patients experienced dyspnoea or shortness of breath and our baseline values of respiratory variables are consistent with those of Auler et al [16] and Hedenstierna & McCarthy [17], confirming the normality of our patients' lung function. Secondly, it has been demonstrated previously that anaesthesia itself can increases E L .…”

Section: Discussionsupporting

confidence: 90%

Respiratory mechanics during and after anaesthesia for major vascular surgery

Volta¹,

Verri²,

Righini³

et al. 1999

Anaesthesia

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SummaryTo evaluate the effects of major vascular surgery on respiratory mechanics, 11 patients undergoing general anaesthesia for abdominal aortic surgery were studied. Before aortic cross-clamping, chest wall elastance and resistance both increased (by 126% and 58%, respectively) when surgical retractors were placed. After aortic cross-clamping, lung elastance increased by 29%, accompanied by a decrease in cardiac index (22%) and an increase in pulmonary (17%) and systemic (15%) vascular resistance. After aortic unclamping, lung elastance decreased, although it remained higher than baseline values (by 12% Changes in respiratory system elastance have been described previously during anaesthesia. This has been attributed to various mechanisms, for example an increased thoracic blood volume [1][2][3][4]. During major vascular surgery aortic cross-clamping (ACC) is likely to cause a redistribution of blood to the upper part of the body [5]. If this phenomenon also occurs at the lung level, lung elastance might increase. This hypothesis was proposed almost 60 years ago, when Barcroft & Samaan [6] suggested that an increase in blood volume in the lungs can occur during and after ACC. In contrast, Paterson et al. [7] observed interstitial pulmonary oedema on chest radiography 4-8 h after surgery, even though pulmonary arterial occlusion pressure did not exceed 12 mmHg. They also described increased peak airway pressure, although the latter could arise because of an increase not only of respiratory elastance, but also of respiratory resistance, and therefore should not be used to quantify pulmonary disease. Moreover, a high percentage of pulmonary failure [5] has been described following repair of thoracoabdominal aneurysm, which is likely to represent a more severe clinical condition. We sought to study repair of abdominal aneurysm as a model of cardiac-lung interaction during major vascular surgery. Methods Patients and monitoring proceduresEleven patients (10 males) undergoing general anaesthesia for infrarenal aortic surgery were studied. The research was approved by our institutional ethics committee and informed consent was obtained from all subjects. No premedication was administrated. Anaesthesia was induced with fentanyl and thiopentone and maintained with 60% nitrous oxide/0.2-0.3% isoflurane in oxygen according to our standard practice, with further fentanyl as required. Orotracheal intubation was facilitated by vecuronium 0.1 mg.kg ¹1 with further doses to provide a level of twitch depression at which no palpable response to train-of-four stimulation was obtained. The patients' lungs were ventilated mechanically (Ohmeda Excel 210, BOC Health Care) with tidal volume (V T ) and ventilatory frequency ( f ) chosen to maintain normocapnia.Because the quantity and quality of the administered fluids could have an effect on respiratory and cardiovascular variables, peri-operative fluid management consisted of an almost fixed amount of both quality (crystalloid : colloid 3 : 1) and quantity (12 Ϯ 3 ml.kg ¹1 .h ¹1 )...

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Section: Discussionsupporting

confidence: 90%

Respiratory mechanics during and after anaesthesia for major vascular surgery

Volta¹,

Verri²,

Righini³

et al. 1999

Anaesthesia

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“…The lower dynamic lung compliance and the higher inspiratory resistance with IPPB have also been shown to occur with controlled ventilation (patient relaxed throughout the respiratory cycle) of normal subjects as well as lung-diseased patients (7,11,22,25,30,44). The reduction in lung compliance was less marked in the present study compared with findings during controlled ventilation, while the increase in inspiratory resistance (on an average 3 cm H,O x I-' x sec) corresponds to the increase found under controlled ventilation.…”

Section: Discussionmentioning

confidence: 97%

Acute Effects of Intermittent Positive Pressure Breathing in Patients with Chronic Obstructive Lung Disease

Hedenstierna¹,

Gertz²

1976

Scandinavian Journal of Clinical and Laboratory Investigation

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The immediate effects of intermittent positive pressure breathing (IPPB) on air were studied in seven patients (age 55-73 years) with advanced chronic obstructive lung disease (COLD) and with chronic respiratory insufficiency. Dynamic lung compliance was reduced by an average of 25% by IPPB, while inspiratory resistance increased by 40%. Distribution of inspired gas, as determined by nitrogen washout, became more even with IPPB. Respiratory frequency was not altered, whereas total ventilation increased by 25% during IPPB and PaCO2 was reduced. Oxygen uptake was reduced by 6%. PaO2 did not change during IPPB but had decreased by an average of 20% 10 minutes after IPPB and then slowly improved; PaCO2 did not change after IPPB. The pressures in the right atrium, pulmonary artery, and in pulmonary wedge position all increased approximately 2 mm Hg (approximately 2 cm H2O) with IPPB, while intrathoracic pressure rose on an average by 5 cm H2O, the transmural pressures thus being lowered during IPPB. The pulmonary vascular resistance was not significantly altered by IPPB, whereas the systemic vascular resistance rose 25%. Cardiac output was reduced approximately 20% and venous admixture almost 50%.

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“…1Zesistarice 'I'he inspiratory resistance during anaesthesia was low in most subjects and, in one subject, slightly above comparable mean values in previous studies (cf. WESTGATE et al HEDENSTIERNA & MCCARTHY 1975a).…”

Section: Single Breath Washout Slope Of Alveolar Plateaumentioning

confidence: 99%

“…During anaesthesia, most subjects display airway closure within or even above a normal tidal breath (GIL- MOUR et al 1976, HEDENSTIERNA et al 1976a, 1976b. The inspiratory resistance, including resistance to gas flow in airways and pulmonary tissue resistance, has been shown to be increased by anaesthesia (CLEMENTS et al 1959, WESTCATE et al 1962, NORLANDER et al 1968, HEDENSTIERNA & MCCARTHY 1975a and may, in analogy with the increased resistance found in chronic obstructive lung disease, indicate an increased scatter of regional airway resistances and thus pulmonary time constants. The extent to which each of these factorsairway closure and non-gravitational differences in regional time constants -may affect gas distribution within the lung has not been established in the anaesthetized, normal subject.…”

mentioning

confidence: 99%

Studies on Intrapulmonary Gas Distribution in the Normal Subject Influence of Anaesthesia and Artificial Ventilation

Hedenstierna

Santesson

1979

Acta Anaesthesiol Scand

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Intrapulmonary gas distribution, assessed by a multiple breath, nitrogen washout technique and expressed by the Fowler index NWOD, was studied in subjects with healthy lungs during spontaneous breathing while awake, and during mechanical ventilation under halothane anaesthesia. The distribution index rose from a mean of 32% awake to 56% during anaesthesia. An attempt was also made to differentiate between the contribution of gravitational (airway closure) and non-gravitational (diffuse airway obstruction) inhomogeneity of ventilation. This was accomplished by measurement of the slope of the alveolar plateau during a sinle breath nitrogen washout. The slope was similar awake and anaesthetized, and it increased equally under both conditions, when preinspiratory lung volume was stepped up from RV to CC, CC being the lung volume at which airways begin to close during expiration. NWOD was significantly correlated to the degree of airway closure, expressed as FRC-CC, and, less so, to inspiratory resistance. It is suggested that a less efficient ventilation distribution in anaesthetized normal subjects, as measured by NWOD, is caused rather by airway closure (gravitational inhomogeneity) than by diffuse airway obstruction (non-gravitational inhomogeneity of ventilation).

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Mechanics of Breathing, Gas Distribution and Functional Residual Capacity at Different Frequencies of Respiration During Spontaneous and Artificial Ventilation

Cited by 37 publications

References 20 publications

Respiratory mechanics during and after anaesthesia for major vascular surgery

Respiratory mechanics during and after anaesthesia for major vascular surgery

Acute Effects of Intermittent Positive Pressure Breathing in Patients with Chronic Obstructive Lung Disease

Studies on Intrapulmonary Gas Distribution in the Normal Subject Influence of Anaesthesia and Artificial Ventilation

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