Postural control, male sex and use of a walking aid are associated with falling during hospitalization after acute stroke.
Suboptimal asthma control is common despite modern asthma therapy. The degree of peripheral airway involvement remains unclear and poor medication delivery to these regions might be a contributing reason for this failure in obtaining adequate symptom control. A cohort of 196 adults (median (range) age 44 (18-61) years, 109 females, 54 ex-smokers, six current smokers) with physician-diagnosed asthma were recruited from primary care. Subjects were characterized clinically by interviews, questionnaires, skin prick tests (SPT) and blood eosinophil counts. Lung function was assessed by spirometry, impulse oscillometry (IOS) and nitrogen multiple breath washout (N2 MBW). IOS assessed peripheral airway resistance (FDR, frequency dependence of resistance). N2 MBW assessed global ventilation inhomogeneity (LCI, lung clearance index), specific indices of peripheral airway function (Scond × VT and Sacin × VT; VT, tidal volume), and inter-regional inhomogeneity (specific ventilation ratio). Never-smoking healthy cohorts of 158 and 400 adult subjects provided local reference values for IOS and N2 MBW variables, respectively. Peripheral airway dysfunction was detected in 31% (FDR or specific ventilation ratio) to 47% (Scond x VT) of subjects. Risk factors for peripheral airway dysfunction were identified. Among subjects with low FEV1 and either positive smoking history and/or blood eosinophilia (>4.0%), 63% had abnormality across all peripheral airway outcomes, whilst only one subject was completely normal. Abnormal peripheral airway function was present in a large proportion of adult asthmatics at baseline. Reduced FEV1, a positive smoking history, and/or blood eosinophilia identified "a small airway asthma subtype" that might benefit from peripheral airway targeted therapy.
Nitrogen multiple breath washout (N MBW) is a sensitive method to identify peripheral airway involvement in asthma, but is a time-consuming test. The N vital capacity single breath (VC SBW) test offers greater time efficiency, but concordance with N MBW is poorly understood. The prevalence of peripheral airway abnormality was determined by N MBW and N SBW tests in 194 asthmatic subjects aged 18-1 years. N MBW data were related to findings in 400 healthy controls, aged 17-71 years, while N SBW data were compared to findings in 224 healthy controls, aged 15-65 years, to derive equipment-specific reference values. Amongst asthmatic subjects, relationships between N SBW and N MBW outcomes were studied. N SBW relationship with clinical history, spirometry, blood eosinophils and fraction exhaled nitric oxide (FENO) data was also explored. The prevalence of peripheral airway involvement (i.e. abnormal ventilation distribution) determined by N SBW-derived phase III slope (N S ) was 24·7%, compared to 44% determined by N MBW-derived lung clearance index (LCI) (P<0·001). Predictors of abnormal N S were older age, smoking history and lower FEV N SBW offers lower sensitivity than N MBW to detect small airway dysfunction in adult asthma, but may be a marker of more severe disease.
We have previously shown that functional residual capacity (FRC) and lung clearance index were significantly greater in sleeping healthy infants when measured by N2 (nitrogen) washout using 100% O2 (oxygen) versus 4% SF6 (sulfur hexafluoride) washout using air. Following 100% O2 exposure, tidal volumes decreased by over 30%, while end‐expiratory lung volume (EELV, i.e., FRC) rose markedly based on ultrasonic flow meter assessments. In the present study to investigate the mechanism behind the observed changes, N2 MBW was performed in 10 separate healthy full‐term spontaneously sleeping infants, mean (range) 26 (18–31) weeks, with simultaneous EELV monitoring (respiratory inductance plethysmography, RIP) and oxygen uptake (V´O2) assessment during prephase air breathing, during N2 washout by exposure to 100% O2, and subsequently during air breathing. While flow meter signals suggested a rise in ELLV by mean (SD) 26 (9) ml over the washout period, RIP signals demonstrated no EELV change. V'O2/FRC ratio during air breathing was mean (SD) 0.43 (0.08)/min, approximately seven times higher than that calculated from adult data. We propose that our previously reported flow meter‐based overestimation of EELV was in fact a physiological artifact caused by rapid and marked movement of O2 across the alveolar capillary membrane into the blood and tissue during 100% O2 exposure, without concomitant transfer of N2 to the same degree in the opposite direction. This may be driven by the high observed O2 consumption and resulting cardiac output encountered in infancy. Furthermore, the low resting lung volume in infancy may make this error in lung volume determination by N2 washout relatively large.
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