Gas Exchange in the Lungs
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The diffusing capacity is the rate at which oxygen or carbon monoxide is absorbed from alveolar gas into pulmonary capillaries (in millilitres per minute) per unit partial pressure gradient (mmHg). The transfer of carbon monoxide from alveolus to pulmonary blood is very rapid. It has a high affinity for haemoglobin (210 times that of oxygen). Consequently, the partial pressure of carbon monoxide in blood is zero, as it is not dissolved in blood. The partial pressure gradient of carbon monoxide across the alveolar–capillary barrier is maintained for the entire time the blood spends in the pulmonary blood. The diffusion of carbon monoxide is limited only by its diffusivity across the barrier, the surface area and the thickness of the barrier. Carbon monoxide in the alveolus does not equilibrate by the time blood reaches the end of the pulmonary capillary. Carbon monoxide transfer from alveolus to pulmonary capillary blood is referred to as diffusion limited.
Interstitial Lung disease In Childhood Rheumatic Disorders
Lourdes R. Laraya-Cuasay, Walter T. Hughes in Interstitial Lung Diseases in Children, 2019
Steen and associates26 followed 44 patients with PSS treated with a mean dose of 636 mg of D-penicillamine for 2.3 years. They compared these patients with 48 untreated patients who had repeat pulmonary function tests. There was a mean of 3.5 years between sets of pulmonary function tests in the treated group and 4.8 years in the untreated group. There were no significant changes in the vital capacity or forced expiratory volumes in either group but there was a small change in diffusing capacity in penicillamine treated patients, from 76 to 87% of the predicted value. Diffusing capacity in untreated patients changed from 73 to 76% of the predicted value. The improvement in treated patients was associated with no further progression of dyspnea or of fibrosis on chest radiograph. The authors concluded that D-penicillamine might be useful in treatment of PSS involving the lung. Other agents including corticosteroids and immunosuppressive drugs have not been shown to alter the pulmonary outcome although corticosteroids occasionally appear to be of short term benefit when there is evidence of inflammatory disease.
Nonparametric Methods
Marcello Pagano, Kimberlee Gauvreau, Heather Mattie in Principles of Biostatistics, 2022
Emphysema is a swelling of the air sacs in the lungs that is characterized by labored breathing and an increased susceptibility to infection. Carbon monoxide diffusing capacity, denoted is a measure of lung function that has been tested as a possible diagnostic tool for detecting emphysema. Consider the distributions of CO diffusing capacity for a population of healthy individuals, and a population of patients with emphysema. We are not willing to assume that these distributions follow a normal distribution. Therefore, using a Wilcoxon rank sum test conducted at the level of significance, we evaluate the null hypothesis that the two populations have the same median DlCO.
Lung function in relation to six-minute walk test in pulmonary hypertension
Published in European Clinical Respiratory Journal, 2020
Amir Farkhooy, Michaela Bellocchia, Hans Hedenström, Daniela Libertucci, Caterina Bucca, Christer Janson, Paolo Solidoro, Andrei Malinovschi
No relation between diffusing capacity for carbon monoxide and walk distance was found in the present material. The diffusing capacity relates inversely to the mean pulmonary arterial pressure and this is in line with results from echocardiography studies, which found no relation between pulmonary arterial pressure and 6MWD [20]. We hypothesize that the patients were characterized as pulmonary hypertensive, e.g. reduced diffusion capacity, makes airway obstruction more influential in the outcome of 6MWT due to a tendency of uniformity for DLCO. This is in fact in line with previous findings from our group in which we could demonstrate that in patients suffering from COPD, e.g. airway obstruction, DLCO is more closely linked to reduced walk distance [38]. On the other hand, DLCO/VA was revealed as the main determinant of exercise-induced desaturation, which is in line with reported interdependence between pulmonary diffusion and oxygen desaturation during exercise in patients with diffuse systemic sclerosis and interstitial lung disease [39].
Tracheobronchial amyloidosis: A report of two cases and literature review
Published in Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 2018
Sultan Qanash, Nadir Kharma, Stephen Corne
A 62-year-old male had previously been diagnosed with chronic obstructive pulmonary disease (COPD) secondary to a previous 45-pack year history of smoking. He presented with a 3-year history of cough and SOB, and a 2-month history of fever and purulent sputum that had not responded to multiple courses of antibiotics. He was initially diagnosed with a COPD exacerbation and pneumonia. The physical examination demonstrated decreased breath sounds to the left upper lobe (LUL) and a prolonged expiratory wheeze. A CXR showed increasing density projecting over the left hilum. Chest CT revealed collapse in the LUL secondary to a central obstructing mass (Figure 2). PFT demonstrated an FEV1 of 1.43 L (35% predicted) and an FVC of 3.74 L (69% predicted) with an FEV1/FVC of 0.38. TLC was 10.66 L (132% predicted) with a RV of 6.39 L(249% predicted). Diffusing capacity was 18.76 mL/min/mmHg (57% predicted). He had a FOB that demonstrated polypoid lesions bilaterally in the left and right main stem bronchi and a large lesion occluded the LUL (Figure 3). Pathology was consistent with AL-amyloidosis (Figure 4). Extensive investigations ruled out systemic amyloidosis, and a diagnosis of TBA was made. Argon plasma coagulation (APC) and local resection failed to alleviate LUL collapse. Over 5 years of observation, the patient has continued to smoke, with a fall in his FEV1 to 23% predicted.
Automatic oxygen titration with O2matic® to patients admitted with COVID-19 and hypoxemic respiratory failure
Published in European Clinical Respiratory Journal, 2020
Ejvind Frausing Hansen, Charlotte Sandau Bech, Jørgen Vestbo, Ove Andersen, Linette Marie Kofod
Lung function data showed a marked reduction in FEV1, FVC and PEF, all reduced to approximately 50% of predicted, reflecting a substantial loss of lung volume. It was not possible to measure diffusing capacity due to patients having dyspnea and tachypnea, which prevented the breath-holding maneuver. Neither do we have data on lung function before admission with COVID-19, but only three patients had known obstructive lung disease, which makes it unlikely that a severe reduction in dynamic volumes was present before admission. Some patients experienced difficulties in performing spirometry due to acute breathlessness and coughing, and acceptability criteria could not be met for all patients. However, we find it unlikely that low quality of the spirometry accounts for a substantial part of the reduction in FEV1, FVC and PEF. Another study has shown minor reduction in dynamic values at discharge from admission with COVID-19 [19]. Our study was done during the first days after admission, and 93% of the patients had acute radiological abnormalities with infiltrates and interstitial changes which could account for the severely impacted lung function.
Related Knowledge Centers
- Diffusion
- Hypoxemia
- Lung Volumes
- Respiration
- Lung
- Red Blood Cell
- Pulmonary Function Testing
- Diffusing Capacity For Carbon Monoxide
- Ventilation/Perfusion Ratio
- Dead Space