Airway luminal area is the major determinant of resistance to airflow in the tracheobronchial tree. Women may have smaller central conducting airways than men; however, previous evidence is confounded by an indirect assessment of airway geometry and by subjects with prior smoking history. The purpose of this study was to examine the effect of sex on airway size in healthy nonsmokers. Using low-dose high-resolution computed tomography, we retrospectively assessed airway luminal area in healthy men ( n = 51) and women ( n = 73) of varying ages (19-86 yr). Subjects with a positive smoking history, cardiopulmonary disease, or a body mass index > 40 kg/m were excluded. Luminal areas of the trachea, right and left main bronchus, bronchus intermediate, left and right upper lobes, and the left lower lobe were analyzed at three discrete points. The luminal areas of the conducting airways were ~26%-35% smaller in women. The trachea had the largest differences in luminal area between men and women (298 ± 47 vs. 195 ± 28 mm or 35% smaller for men and women, respectively), whereas the left lower lobe had the smallest differences (57 ± 15 vs. 42 ± 9 mm or 26% smaller for men and women, respectively). When a subset of subjects was matched for height, the sex differences in airway luminal area persisted, with women being ~20%-30% smaller. With all subjects, there were modest relationships between height and airway luminal area ( r = 0.73-0.53, P < 0.05). Although there was considerable overlap between sexes, the luminal areas of the large conducting airways were smaller in healthy women than in men. NEW & NOTEWORTHY Previous evidence for sex differences in airway size has been confounded by indirect measures and/or cohorts with significant smoking histories or pathologies. We found that central airways in healthy women were significantly smaller (~26%-35%) than men. The significant sex-difference in airway size was attenuated (20%-30% smaller) but preserved in a subset of subjects matched for height. Over a range of ages, healthy women have smaller central airways than men.

Patients with heart failure (HF) display numerous derangements in ventilatory function, which together serve to increase the work of breathing (Wb) during exercise. However, the extent to which the resistive and elastic properties of the respiratory system contribute to the higher Wb in these patients is unknown. We quantified the resistive and elastic Wb in patients with stable HF (n=9; New York Heart Association functional class I–II) and healthy control subjects (n=9) at standardised levels of minute ventilation (V′E) during graded exercise. Dynamic lung compliance was systematically lower for a given level of V′E in HF patients than controls (p<0.05). HF patients displayed slightly higher levels of inspiratory elastic Wb with greater amounts of ventilatory constraint and resistive Wb than control subjects during exercise (p<0.05). Our data indicates that the higher Wb in HF patients is primarily due to a greater resistive, rather than elastic, load to breathing. The greater resistive Wb in these patients probably reflects an increased hysteresivity of the airways and lung tissues. The marginally higher inspiratory elastic Wb observed in HF patients appears related to a combined decrease in the compliances of the lungs and chest wall. The clinical and physiological implications of our findings are discussed.

We propose that abnormalities of the pulmonary system contribute significantly to the exertional dyspnea and exercise intolerance observed in patients with chronic heart failure.Interventions designed to address the deleterious pulmonary manifestations of heart failure may therefore yield promising improvements in exercise tolerance in this population.

It is unknown whether the greater total work of breathing (WOB) with aging is due to greater elastic and/or resistive WOB. We hypothesized that older compared with younger adults would exhibit a greater total WOB at matched ventilations (V̇e) during graded exercise, secondary to greater inspiratory resistive and elastic as well as expiratory resistive WOB. Older (OA: 60 ± 8 yr; n = 9) and younger (YA: 38 ± 7 yr; n = 9) adults performed an incremental cycling test to volitional fatigue. Esophageal pressure, inspiratory (IRV) and expiratory reserve volumes (ERV), expiratory flow limitation (EFL), and ventilatory variables were measured at matched V̇e (i.e., 25, 50, and 75 l/min) during exercise. The inspiratory resistive and elastic as well as expiratory resistive WOB were quantified using the Otis method. At V̇e of 75 l/min, older adults had greater %EFL and larger tidal volumes to inspiratory capacity but smaller relative IRV ( P ≤ 0.03) than younger adults. Older compared with younger adults had greater total WOB at V̇ of 50 and 75 l/min (OA: 90 ± 43 vs. YA: 49 ± 21 J/min; P < 0.04 for both). At V̇e of 75 l/min, older adults had greater inspiratory elastic and resistive WOB (OA: 44 ± 27 vs. YA: 24 ± 22 and OA: 23 ± 15 vs. YA: 11 ± 3 J/min, respectively, P < 0.03 for both) and expiratory resistive WOB (OA: 23 ± 19 vs. YA: 14 ± 9 J/min, P = 0.02) than younger adults. These data demonstrate that aging-induced pulmonary alterations result in greater inspiratory elastic and resistive as well as expiratory resistive WOB, which may have implications for the integrated response during exercise. NEW& NOTEWORTHY Aging-induced changes to the pulmonary system result in increased work of breathing (WOB) during exercise. However, it is not known whether this higher WOB with aging is due to differences in elastic and/or resistive WOB. Herein, we demonstrate that older adults exhibited greater inspiratory elastic and resistive as well as expiratory resistive WOB during exercise.

Heart failure (HF) is a complex and multifaceted disease. The disease affects multiple organ systems, including the respiratory system. This review provides three unique examples illustrating how the cardiovascular and respiratory systems interrelate because of the pathology of HF. Specifically, these examples outline the impact of HF pathophysiology on 1) respiratory mechanics and the mechanical “cost” of breathing; 2) mechanical interactions of the heart and lungs; and on 3) abnormalities of pulmonary gas exchange during exercise, and how this may be applied to treatment. The goal of this review is to, therefore, raise the awareness that HF, though primarily a disease of the heart, is accompanied by marked pathology of the respiratory system.

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The "extradiaphragmatic" shift in inspiratory muscle recruitment, commensurate with increasing P(rcm,e) and P(abm,e), may reflect an extreme loading response to breathing against a heavy elastance (i.e., closed glottis). In addition, the relative intensity of diaphragmatic and inspiratory rib cage muscle contractions approaches potentially "fatiguing" levels by the break point of maximal breath holding.

Our data confirm that the external work rate associated with the RCP is labile and that these power outputs display poor measurement agreement with the CP. Taken together, these findings indicate that the RCP does not provide an accurate estimation of CP.