Background -Inspiratory muscle strength is often better reflected by oesophageal pressure during a maximal sniff (sniff POES) than by maximal inspiratory pressure (PImax). Sniff POES can be estimated non-invasively by measuring the sniff nasal inspiratory pressure (SNIP). The aim was to establish maximal normal values for the SNIP and to compare them with PImax.Methods -One hundred and sixty healthy subjects (80 men) aged 20-80 years were recruited. All subjects had a forced vital capacity (FVC) of >80%, a forced expiratory volume in one second (FEV1)IFVC of >85% predicted value, and a body mass index of 18-31 kg/m2. Because Pimax is known to be reduced in the supine posture, the SNIP was measured in both the sitting and the supine positions. Pimax sustained over one second was measured from functional residual capacity (FRC) in the sitting position with a standard flanged mouthpiece during four manoeuvres. SNIP was measured from FRC in the sitting and supine positions using a catheter through a plug occluding one nostril during 10 maximal sniffs through the contralateral nostril. For each test the largest pressure measured in cm H2O was taken into account. Results -For both men and women maximal SNIP was negatively correlated with age, and was similar in the sitting and the supine positions. In the sitting position maximal SNIP was greater or equal to PImax in 107 of 160 subjects. The mean (SD) ratio SNIP/Pimax was 1l08 (0.22) in men and 1-17 (0.29) in women.Conclusions -Normal values of maximal SNIP can be predicted from age and sex. Maximal SNIP is similar in the sitting and the supine position and is significantly higher than Pimax in healthy subjects. The low level of agreement between maximal SNIP and Pimax indicates that the two manoeuvres are not interchangeable but complementary.

The measurement of esophageal pressure during maximal sniffs (sniff Pes) has been shown useful to assess inspiratory muscle strength. The aim of this study was to validate a noninvasive method for estimating sniff Pes. The sniff nasal inspiratory pressure (SNIP) was measured through a plug occluding one nostril during sniffs performed through the contralateral nostril. Sniff Pes was simultaneously measured with an esophageal balloon. Ten normal subjects performed 338 sniffs of variable intensity. The correlation coefficient of SNIP and sniff Pes was 0.99 +/- 0.01 (p < 0.001). The ratio SNIP/sniff Pes was 0.91 (range, 0.82 to 0.99) and the mean difference between the two measures (SNIP - sniff Pes) was -4.56 cm H2O (-1.2 to -8.6 cm H2O). Twelve patients with neuromuscular or skeletal disorders performed 181 maximal sniffs. The correlation coefficient of SNIP and sniff Pes was 0.96 +/- 0.04 (p < 0.001). The ratio SNIP/sniff Pes was 0.93 (0.77 to 1.07) and the mean difference (SNIP - sniff Pes) was -4.66 cm H2O (+0.47 to -14.26 cm H2O). Nasal mucosal congestion was induced by nebulization of increasing doses of histamine in four normal subjects. The ratio SNIP/sniff Pes was 0.93 (0.72 to 1.02) when nasal peak flow was > 100 L/min, and 0.49 (0.36 to 0.57 L/min) when nasal peak flow fell below 100 L/min. We conclude that SNIP provides a reliable and noninvasive estimation of sniff Pes in normal subjects and in patients with neuromuscular or skeletal disorders. The validity of this method may by impaired by severe nasal congestion.

Patients with chronic obstructive pulmonary disease (COPD) often develop weight loss, which is associated with increased mortality. Recombinant human growth hormone (rhGH) treatment has been proposed to improve nitrogen balance and to increase muscle strength in these patients. The aim of this study was to assess the effects of rhGH administration on the nutritional status, resting metabolism, muscle strength, exercise tolerance, dyspnea, and subjective well-being of underweight patients with stable COPD. Sixteen patients attending a pulmonary rehabilitation program (age: 66 +/- 9 yr; weight: 77 +/- 7% of ideal body weight; FEV1: 39 +/- 13% of predicted) were randomly treated daily with either 0.15 IU/kg rhGH or placebo during 3 wk in a double-blind fashion. Measurements were made at the beginning (DO) and at the end (D21) of treatment and 2 mo later (D81). Body weight was similar in the two groups during the study, but lean body mass was significantly higher in the rhGH group at D21 (p < 0.01) and D81 (p < 0.05). The increase in lean body mass was 2.3 +/- 1.6 kg in the rhGH group and 1.1 +/- 0.9 kg in the control group at D21 and 1.9 +/- 1.6 kg in the rhGH group and 0.7 +/- 2.1 kg in the control group at D81. At D21, the resting energy expenditure was increased in the rhGH group (107.8% of DO, p < 0.001 compared with the control group). At D21 and D81, the changes in maximal respiratory pressures, handgrip strength, maximal exercise capacity, and subjective well-being were similar in the two groups. At D21, the 6-min walking distance decreased in the rhGH group (-13 +/- 31%) and increased in the control group (+10 +/- 14%; p < 0.01). We conclude that the daily administration of 0.15 IU/kg rhGH during 3 wk increases lean body mass but does not improve muscle strength or exercise tolerance in underweight patients with COPD.

Inspiratory muscle strength is an important variable in patients with neuromuscular or skeletal disorders. It is usually assessed by measuring maximal inspiratory pressure (PI(max)), but this test may prove difficult for some patients, and low values may originate from incomplete effort or air leaks. We assessed the usefulness of the novel sniff nasal pressure (Pn(sn)) test in 126 patients with a neuromuscular or a skeletal disorder, aged 5 to 49 yr. Pn(sn) was measured in an occluded nostril during maximal sniffs performed through the contralateral nostril. All patients performed the Pn(sn) maneuver easily, whereas 10 young and weak patients with neuromuscular disorders could not perform the PI(max) maneuver. Data were analyzed for the 116 patients who could perform both tests (92 patients with neuromuscular and 24 with skeletal disorders). When expressed as percents of the predicted values, Pn(sn) was similar to PI(max) in patients with neuromuscular disorders (54 +/- 25% predicted [mean +/- SD] versus 52 +/- 24% predicted), and was higher than PI(max) in patients with skeletal disorders (70 +/- 25% predicted versus 61 +/- 27% predicted, p < 0.05). Pn(sn) appeared to be the main determinant of VC in patients with neuromuscular disorders, whereas the Cobb angle and PI(max) were the main determinants of VC in patients with skeletal disorders. We conclude that inspiratory muscle strength can be easily assessed with Pn(sn) in children and adults with various neuromuscular and skeletal disorders. This new muscular parameter appears particularly useful in neuromuscular disorders, in which it represents a major determinant of VC.