Divers revisited: The ventilatory response to carbon dioxide in experienced scuba divers.

PURPOSE: To investigate the ventilatory response to CO2 in hyperoxia, hypoxia, and during exercise amongst experienced scuba divers and matched controls. METHODS: Two studies were performed. The first investigated the CO2 sensitivity in rest and exercise using CO2 rebreathing in hyperoxia at a workload typical for diving with divers (n = 11) and controls (n = 11). The second study examined the respiratory drive of divers (n = 10) and controls (n = 10) whilst breathing four different gas mixtures balanced with N2 (ambient air; 25% O2/6% CO2; 13% O2; 13% O2/6% CO2) to assess the combined response to hypercapnia and moderate hypoxia. RESULTS: Exercise at a load typical for diving was found to have no effect on the ventilatory sensitivity to CO2 in divers (rest: 1.49 ± 0.33; exercise: 1.22 ± 0.55 [l/min × mmHg(-1)]) and controls (rest: 2.08 ± 0.71; exercise: 2.05 ± 0.98 [l/min × mmHg(-1)]) while differences in sensitivity remained between the groups. Inhalation of the four gas mixtures revealed the tested oxygen pressures caused no significant alteration in the ventilatory sensitivity to CO2 in divers and controls. CONCLUSIONS: Experienced divers possess a lower ventilatory response to CO2 which was not affected by exercise or the tested oxygen pressures suggesting a dominant adaptation of central CO2 sensitivity.

So, they thought it was all over.

Non-tubercular mycobacteriae (NTM) are ubiquitous organisms found throughout the environment including soil and water. Incidence of NTM infection or isolation is increasing both in immunocompromised as well as immunocompetent patients and may present with a spectrum of disease similar to tuberculosis. The authors report cases of two patients with a background of cancer who presented with NTM infection mimicking lung cancer. The case report is followed by review of reported cases of NTM infections which presented similarly mimicking cancer. Based on their experience and the review of literature the authors recommend that all efforts should be made to obtain tissue for histology and acid fast bacilli examination in all cases which present with lung masses, nodules, bronchiectasis, air-space shadowing or cavity formation especially over a background of structural lung disease. Such cases should be kept under close clinical and radiological follow-up, as cancer and NTM infections can coexist.