Effect of body posture on respiratory impedance

Navajas, Daniel; Farre, R.; Rotger, M.; Milic–Emili, J.; Sanchís, J.

doi:10.1152/jappl.1988.64.1.194

Cited by 75 publications

(60 citation statements)

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“…This is not the case for FRC. Whereas in normal subjects, FRC falls by 700 -800 ml on going from the seated to the supine position (3,21,32,33,35), in severely obese subjects our laboratory (33,35) and others (3,32) have shown that supine falls in FRC are much smaller and may even be absent. The difference in values of FRC, FRC/TLC, and ERV between control and obese subjects shown in Table 2, therefore, would be even larger if the subjects were seated.…”

Section: Methodsmentioning

confidence: 54%

“…There is no consistent supine change in RV, but supine values of TLC and VC in normal subjects are, on average, slightly lower (200 ml or less) than seated values (3,21,32,33,35), with the reduction being attributed to an increase in central blood volume when supine. Similar small reductions in supine TLC and VC have been shown in obese subjects (3,32,33,35); indeed, previously our laboratory found that supine TLC in obese subjects, some of whom had lung restriction, was, on average, only 80 ml smaller than seated values (33).…”

Section: Methodsmentioning

confidence: 83%

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Reduction of total lung capacity in obese men: comparison of total intrathoracic and gas volumes

Watson

Pride

Thomas

et al. 2010

Journal of Applied Physiology

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Ind PW, Bell JD. Reduction of total lung capacity in obese men: comparison of total intrathoracic and gas volumes. J Appl Physiol 108: 1605-1612, 2010. First published March 18, 2010 doi:10.1152/japplphysiol.01267.2009.-Restriction of total lung capacity (TLC) is found in some obese subjects, but the mechanism is unclear. Two hypotheses are as follows: 1) increased abdominal volume prevents full descent of the diaphragm; and 2) increased intrathoracic fat reduces space for full lung expansion. We have measured total intrathoracic volume at full inflation using magnetic resonance imaging (MRI) in 14 asymptomatic obese men [mean age 52 yr, body mass index (BMI) 35-45 kg/m 2 ] and 7 control men (mean age 50 yr, BMI 22-27 kg/m 2 ). MRI volumes were compared with gas volumes at TLC. All measurements were made with subjects supine. Obese men had smaller functional residual capacity (FRC) and FRC-to-TLC ratio than control men. There was a 12% predicted difference in mean TLC between obese (84% predicted) and control men (96% predicted). In contrast, differences in total intrathoracic volume (MRI) at full inflation were only 4% predicted TLC (obese 116% predicted TLC, control 120% predicted TLC), because mediastinal volume was larger in obese than in control [heart and major vessels (obese 1.10 liter, control 0.87 liter, P ϭ 0.016) and intrathoracic fat (obese 0.68 liter, control 0.23 liter, P Ͻ 0.0001)]. As a consequence of increased mediastinal volume, intrathoracic volume at FRC in obese men was considerably larger than indicated by the gas volume at FRC. The difference in gas volume at TLC between the six obese men with restriction, TLC Ͻ 80% predicted (OR), and the eight obese men with TLC Ͼ 80% predicted (ON) was 26% predicted TLC. Mediastinal volume was similar in OR (1.84 liter) and ON (1.73 liter), but total intrathoracic volume was 19% predicted TLC smaller in OR than in ON. We conclude that the major factor restricting TLC in some obese men was reduced thoracic expansion at full inflation. magnetic resonance imaging; restricted total lung capacity; mediastinal volume ABOUT 50 YEARS AGO, IT WAS established that functional residual capacity (FRC) and expiratory reserve volume (ERV) are reduced in most seated obese subjects (14, 32). More recently, reduction in total lung capacity (TLC), formerly thought only to occur in massively obese subjects (28), has been found in some subjects with less severe obesity (17). Consistent with the development of a restrictive pattern of lung function in some obese subjects, prospective studies have shown that weight gain is associated with loss of vital capacity (VC) (6,7,34), while weight loss is associated with increase in VC (22,28,29,31).The mechanical factors reducing VC and TLC in obesity are uncertain, but it has been speculated that increased abdominal volume in some way reduces inspiratory descent of the diaphragm and consequent expansion of the thorax. Recent studies of induced ascites in dogs have shown that, at FRC, the lung-expanding action of the diaphragm was r...

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Section: Methodsmentioning

confidence: 54%

Section: Methodsmentioning

confidence: 83%

Reduction of total lung capacity in obese men: comparison of total intrathoracic and gas volumes

Watson

Pride

Thomas

et al. 2010

Journal of Applied Physiology

View full text Add to dashboard Cite

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“…Total resistance and reactance of the respiratory system were measured using the forced oscillation technique, as described in detail previously [11,13]. The forced oscillations (2 hPa peak-to-peak, 4-32 Hz) were generated by means of a loudspeaker enclosed in a chamber, servocontrolled [14] to withstand the pressure variation due to the subject's breathing, and applied at the mouth of the subject through the four-port valve ( fig.…”

Section: Methodsmentioning

confidence: 99%

Effect of nitric oxide inhalation on respiratory system resistance in chronic obstructive pulmonary disease

Roger¹,

Barberà²,

Farré³

et al. 1996

Eur Respir J

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Nitric oxide (NO) has been identified as a neurotransmitter of nonadrenergic noncholinergic bronchodilator nerves. To investigate whether inhaled NO exerts a bronchodilator effect in patients with chronic obstructive pulmonary disease (COPD), we measured the resistance of the respiratory system, using the forced oscillation technique, while breathing NO.Eight patients with COPD (7 men and 1 woman; aged 66±7 yrs (mean±SD); forced expiratory volume in one second (FEV1) 37±17% of predicted) and eight healthy subjects (7 men and 1 woman; 33±4 yrs; FEV1 108±14% pred) were studied. Nitric oxide, at a concentration of 40 parts per million (ppm) in air, was inhaled for 20 min. Total resistance (Rrs) and reactance (Xrs) of the respiratory system, arterial oxygen saturation, heart rate, tidal volume, and breathing frequency were continuously recorded at baseline, and during and after ceasing NO inhalation. Methaemoglobin levels were additionally measured in healthy subjects.At baseline, patients with COPD showed higher Rrs than healthy subjects (Rrs From these results, we conclude that inhaled nitric oxide, at a concentration of 40 ppm, exerts no effect on respiratory system resistance in patients with chronic obstructive pulmonary disease or in healthy subjects.

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“…2,3 For patients experiencing orthopnoea, total lung capacity and vital capacity are enhanced with an elevated position. 4,5 Specifically in patients with HNC, the additional factor of excessive salivation is one of the most common patient-reported symptoms. An elevated position decreases pooling of accumulated saliva in the pharynx, reduces the hazard of choking and assists in fluid clearance.…”

Section: Introductionmentioning

confidence: 99%

Slant board immobilisation of head-and-neck radiotherapy patients who cannot tolerate a flat position

et al. 2016

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Purpose: Patients treated with intensity-modulated radiation therapy (IMRT) for head-and-neck cancer are often positioned supine on a carbon fibre board to which a thermoplastic mask is attached to immobilise the head and shoulders. For patients unable to tolerate a supine position, we developed a tilting board that accommodates a full-scale head-and-shoulder mask. Materials and methods:Phantom measurements were obtained to confirm the dosimetric accuracy of our treatment planning system when using this board. A patient was simulated in the flat and tilted positions on the board. The two corresponding treatment plans were evaluated by comparing the target coverage and doses with organs at risk. The patient's intra-fraction motion was quantified during his tilted treatments.Results: Phantom measurements confirmed the accuracy of the dosimetric calculations. The tilted plan met dosimetric standards for clinical acceptability. The intra-fraction motion of the patient in the tilted position was >3 mm in any direction. Conclusions:The tilting board met clinical requirements for IMRT planning and delivery. Full-scale head-and-shoulder immobilisation was achieved in a more tolerable tilted position.

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Effect of body posture on respiratory impedance

Cited by 75 publications

References 0 publications

Reduction of total lung capacity in obese men: comparison of total intrathoracic and gas volumes

Reduction of total lung capacity in obese men: comparison of total intrathoracic and gas volumes

Effect of nitric oxide inhalation on respiratory system resistance in chronic obstructive pulmonary disease

Slant board immobilisation of head-and-neck radiotherapy patients who cannot tolerate a flat position

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